Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Syo Matsumura Last modified date:2021.10.28

Professor / Quantum Sciences of Materials / Department of Applied Quantum Physics and Nuclear Engineering / Faculty of Engineering

1. Junsik Mun, Wei Peng, Chang Jae Roh, Sangmin Lee, Syo Matsumura, Jong Seok Lee, Tae Won Noh, Miyoung Kim, In Situ Cryogenic HAADF-STEM Observation of Spontaneous Transition of Ferroelectric Polarization Domain Structures at Low Temperatures, Nano Letters, 10.1021/acs.nanolett.1c02729, 21, 20, 8679-8686, 2021.10, Precise determination of atomic structures in ferroelectric thin films and their evolution with temperature is crucial for fundamental study and design of functional materials. However, this has been impeded by the lack of techniques applicable to a thin-film geometry. Here we use cryogenic scanning transmission electron microscopy (STEM) to observe the atomic structure of a BaTiO3 film on a (111)-SrTiO3 substrate under varying temperatures. Our study explicitly proves a structure transition from a complex polymorphic nanodomain configuration at room temperature transitioning to a homogeneous ground-state rhombohedral structure of BaTiO3 below ∼250 K, which was predicted by phase-field simulation. More importantly, another unexpected transition is revealed, a transition to complex nanodomains below ∼105 K caused by an altered mechanical boundary condition due to the antiferrodistortive phase transition of the SrTiO3 substrate. This study demonstrates the power of cryogenic STEM in elucidating structure–property relationships in numerous functional materials at low temperatures..
2. Katsutoshi Sato, Shin-ichiro Miyahara, Kotoko Tsujimaru, Yuichiro Wada, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Koji Inazu, Hirono Mohri, Takeshi Iwasa, Tetsuya Taketsugu, Katsutoshi Nagaoka , Barium Oxide Encapsulating Cobalt Nanoparticles Supported on Magnesium Oxide: Active Non-Noble Metal Catalysts for Ammonia Synthesis under Mild Reaction Conditions, ACS Catalysis, 10.1021/acscatal.1c02887, 11, 13050-13061, 2021.10, To realize a carbon-free society, catalysts are needed for the synthesis of ammonia under mild reaction conditions (<400 °C, <10 MPa) that use hydrogen produced from renewable energy. Ru-based catalysts are currently the most promising candidates; however, Ru is expensive and of low abundance. Here, we discovered that the encapsulation of Co nanoparticles with BaO enhanced the ammonia synthesis activity of Co and that a simple Ba-doped Co/MgO catalyst prereduced at an unusually high temperature of 700 °C ([email protected]/MgO-700red) showed outstanding ammonia synthesis activity. The ammonia synthesis rate (24.6 mmol gcat–1 h–1) and turnover frequency (0.246 s–1) of the catalyst at 350 °C and 1.0 MPa were about 80 and 250 times higher, respectively, than those of the nondoped parent catalyst. At the same temperature but higher pressure (3.0 MPa), the ammonia synthesis rate was increased to 48.4 mmol gcat–1 h–1, which is higher than that of active Ru-based catalysts. In addition, at 1.0 MPa, our catalyst produced ammonia even at temperatures as low as 150 °C. Scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy investigations revealed that after reduction at 700 °C, the Co nanoparticles had become encapsulated by a nanofraction of BaO. The mechanism underlying the formation of this unique structure was considered to comprise reduction of oxidic Co to metallic Co, decomposition of BaCO3 to BaO, and migration of BaO and Co nanoparticles. Spectroscopic and density functional theory investigations revealed that adsorption of N2 on the Co atoms at the catalyst surface weakened the N2 triple bond to the strength of a double bond due to electron donation from Ba²⁺ of BaO via adjacent Co atoms; this weakening accelerated the cleavage of the triple bond, which is the rate-determining step for ammonia synthesis..
3. Yuko Mitsuka, Naoki Ogiwara, Megumi Mukoyoshi, Hiroshi Kitagawa, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Masaaki Haneda, Shogo Kawaguchi, Yoshiki Kubota, Hirokazu Kobayashi, Fabrication of Integrated Copper-Based Nanoparticles/Amorphous Metal–Organic Framework by a Facile Spray-Drying Method: Highly Enhanced CO2 Hydrogenation Activity for Methanol Synthesis, Angewandte Chemie International Edition, 10.1002/anie.202110585, 60, 41, 22283-22288, 2021.08, We report on Cu/amUiO-66, a composite made of Cu nanoparticles (NPs) and amorphous [Zr6O4(OH)4(BDC)6] (amUiO-66, BDC=1,4-benzenedicarboxylate), and Cu-ZnO/amUiO-66 made of Cu-ZnO nanocomposites and amUiO-66. Both structures were obtained via a spray-drying method and characterized using high-resolution transmission electron microscopy, energy dispersive spectra, powder X-ray diffraction and extended X-ray absorption fine structure. The catalytic activity of Cu/amUiO-66 for CO2 hydrogenation to methanol was 3-fold that of Cu/crystalline UiO-66. Moreover, Cu-ZnO/amUiO-66 enhanced the methanol production rate by 1.5-fold compared with Cu/amUiO-66 and 2.5-fold compared with γ-Al2O3-supported Cu-ZnO nanocomposites (Cu-ZnO/γ-Al2O3) as the representative hydrogenation catalyst. The high catalytic performance was investigated using in situ Fourier transform IR spectra. This is a first report of a catalyst comprising metal NPs and an amorphous metal–organic framework in a gas-phase reaction..
4. Kohei Aso, Jens Maebe, Xuan Quy Tran, Tomokazu Yamamoto, Yoshifumi Oshima, Syo Matsumura, Subpercent Local Strains Due to the Shapes of Gold Nanorods Revealed by Data-Driven Analysis, ACS Nano, 10.1021/acsnano.1c03413, 15, 7, 12077-12085, 2021.07, Analysis of subpercent local strain is important for a deeper understanding of nanomaterials, whose properties often depend on the strain. Conventional strain analysis has been performed by measuring interatomic distances from scanning transmission electron microscopy (STEM) images. However, measuring subpercent strain remains a challenge because the peak positions in STEM images do not precisely correspond to the real atomic positions due to disturbing influences, such as random noise and image distortion. Here, we utilized an advanced data-driven analysis method, Gaussian process regression, to predict the true strain distribution by reconstructing the true atomic positions. As a result, a precision of 0.2% was achieved in strain measurement at the atomic scale. The method was applied to gold nanoparticles of different shapes to reveal the shape dependence of the strain distribution. A spherical gold nanoparticle showed a symmetric strain distribution with a contraction of ∼1% near the surface owing to surface relaxation. By contrast, a gold nanorod, which is a cylinder terminated by hemispherical caps on both sides, showed nonuniform strain distributions with lattice expansions of ∼0.5% along the longitudinal axis around the caps except for the contraction at the surface. Our results indicate that the strain distribution depends on the shape of the nanomaterials. The proposed data-driven analysis is a convenient and powerful tool to measure the strain distribution with high precision at the atomic scale..
5. Shanshan Liu, Zihan Li, Ke Yang, Enze Zhang, Awadhesh Narayan, Xiaoqian Zhang, Jiayi Zhu, Wenqing Liu, Zhiming Liao, Masaki Kudo, Takaaki Toriyama, Yunkun Yang, Qiang Li, Linfeng Ai, Ce Huang, Jiabao Sun, Xiaojiao Guo, Wenzhong Bao, Qingsong Deng, Yanhui Chen, Lifeng Yin, Jian Shen, Xiaodong Han, Syo Matsumura, Jin Zou, Yongbing Xu, Xiaodong Xu, Hua Wu, Faxian Xiu, Tuning 2D magnetism in Fe3+XGeTe2 films by element doping, National Science Review, 10.1093/nsr/nwab117, 2021.07, Two-dimensional (2D) ferromagnetic materials have been discovered with tunable magnetism and orbital-driven nodal-line features. Controlling the 2D magnetism in exfoliated nanoflakes via electric/magnetic fields enables the boosted Curie temperature (TC) or phase transitions. One of the challenges, however, is the realization of high TC 2D magnets that are tunable, robust and suitable for large scale fabrication. Here, we report molecular-beam epitaxy growth of wafer-scale Fe3+XGeTe2 films with TC above-room-temperature. By controlling the Fe composition in Fe3+XGeTe2, a continuously-modulated TC in a broad range of 185–320 K has been achieved. This widely tunable TC is attributed to the doped interlayer Fe that provide a 40% enhancement around the optimal composition X = 2. We further fabricated magnetic tunneling junction device arrays that exhibit clear tunneling signals. Our results show an effective and reliable approach, i.e. element doping, to produce robust and tunable ferromagnetism beyond room temperature in a large-scale 2D Fe3+XGeTe2 fashion..
6. Shiqian Liu, Xin Fu Tan, Stuart D. McDonald, Qinfen Gu, Syo Matsumura, Kazuhiro Nogita, Interfacial reactions between Ga and Cu-xNi (x=0, 2, 6, 10, 14) substrates and the strength of Cu-xNi/Ga/Cu-xNi joints, Intermetallics, 10.1016/j.intermet.2021.107168, 133, 107168, 1-9, 2021.06, There is potential for using Ga and Ga-based alloys as low temperature bonding materials in electronic packaging. This study investigates the interfacial reactions between liquid Ga and Cu-xNi (x = 0, 2, 6, 10, 14 wt%) substrates at room temperature using Synchrotron X-ray powder diffraction and analytical scanning/transmission electron microscopy, and subsequently examines the lap shear strength of these joints. The concentration of Ni in the substrate has a strong effect on both the type of intermetallics that form and their rate of growth. Mechanisms of intermetallic growth and the strength of the joints fabricated with the Cu-xNi substrates are discussed along with the crystallography of the intermetallics and methods of joining..
7. M.M. Rahman, T. Yamamoto, S. Matsumura, J.M. Costantini, K. Yasuda, Ab Initio molecular dynamics study of threshold displacement energy in Zirconium Nitride, Journal of Nuclear Materials, 10.1016/j.jnucmat.2021.153076, 554, 153076, 1-9, 2021.05, Zirconium nitride (ZrN) is a promising matrix candidate for advanced nuclear fuels and transmutation of minor actinides. This study investigates the displacement process induced by low-energy recoils in ZrN using ab initio molecular dynamics (AIMD) simulations to evaluate the threshold displacement energy (Ed). Observations of the collision processes of primary knock-on atoms (PKAs) for both Zr and N atoms were performed for seven different directions: [100], [110], [111], [210], [211], [221], and [321], which cover most regions of the stereographic triangle. The values of Ed ranged from 15 eV to 50 eV, and the collision processes were dependent on the crystallographic orientations. The weighted average values of Ed evaluated from the PKA directions investigated in this study were 33 eV and 29 eV for the Zr and N atoms, respectively. Anti-site defects were not formed for either Zr or N PKAs. Sequential replacement collisions along the [110] atomic row played an important role in the collision process, providing a lower value of Ed in the crystallographic directions. Furthermore, configurations of interstitials were different between the Zr and N atoms, which also influenced Ed values..
8. Megumi Mukoyoshi, Hirokazu Kobayashi, Kohei Kusada, Kazuya Otsubo, Mitsuhiko Maesato, Yoshiki Kubota, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, Ni@onion-like carbon and Co@amorphous carbon: control of carbon structures by metal ion species in MOFs, Chemical Communications, 10.1039/D1CC02154K, 57, 48, 5897-5900, 2021.05, We first report the facile synthesis of metal–carbon composites consisting of metal nanoparticles (NPs) and different types of carbon species: onion-like and amorphous carbon, Ni@onion-like carbon and Co@amorphous carbon. By simply changing the metal species in an isostructural metal–organic framework, thermal decompositions of MOF-74 directly afforded different types of metal NPs and carbon composites, which exhibited good electrical conductivity. In particular, the Ni@onion-like carbon, having a well-ordered carbon structure, had high electrical conductivity (σ = 5.3 Ω−1 cm−1 at 295 K), explained by a modified model of the Efros–Shklovskii variable range hopping..
9. Akhil Tayal, Okkyun Seo, Jaemyung Kim, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, Osami Sakata, Mechanism of Hydrogen Storage and Structural Transformation in Bimetallic Pd–Pt Nanoparticles, ACS Applied Materials & Interfaces, 10.1021/acsami.0c22432, 13, 20, 23502-23512, 2021.05, The hydrogen storage capacity of Pd nanoparticles (NPs) decreases as the particles become smaller; however, this reduced capacity is ameliorated by addition of Pt. In the present work, the hydrogen storage mechanism and structural transformations of core (Pd)–shell (Pt) (CS) and solid-solution (SS) NPs during hydrogen absorption and desorption (PHAD) processes are investigated. In situ X-ray absorption spectroscopy measurements were performed to study the evolution of electronic and local structures around Pd and Pt during PHAD. Under ambient conditions, Pd and Pt have distinct local structures. The Pd atomic pairs are more strained in CS NPs than in SS NPs. A similar behavior has been seen in CS NPs after PHAD. The Pd K-edge extended X-ray absorption fine structure data indicate that in CS and SS NPs a substantial fraction of the signal derives from Pd–Pd atomic pairs, indicating that Pd clusters remain present even after PHAD. PHAD causes a rearrangement of the interfacial structure, which becomes homogeneously distributed. The higher coverage of active bimetallic sites results in a higher observed hydrogen storage capacity in the SS phase..
10. Sumio Iijima Wenhui Yang, Syo Matsumura, Ichiro Ohnishi, Atomic resolution imaging of cation ordering in niobium–tungsten complex oxides, Communications Materials, 10.1038/s43246-021-00128-z, 2, 24, 1-9, 2021.03, Energy dispersive X-ray emission imaging at atomic resolution is a powerful tool to solve order–disorder problems in complex metal oxide crystals, supplementing conventional X-ray or neutron diffraction. Here, we use this method, based on scanning transmission electron microscopy, to investigate cation ordering in ternary metal oxides 4Nb2O5·9WO3 and 2Nb2O5·7WO3, which have recently attracted attention as energy storage materials in lithium-ion batteries. Their crystal structures are a tetragonal tungsten bronze-type and its hybrid with a ReO3-type ‘block structure’, respectively. Our study reveals the presence of chemical ordering of metal ions in these materials, which have previously been assumed to be solid-solutions. In particular, we show that the two types of cations, Nb and W, are well ordered in their lattices, and that the Nb ions tend to occupy one third of the pentagonal channel sites. These results demonstrate that atomic resolution X-ray emission imaging is an effective alternative approach for the study of locally ordered crystal structures..
11. Keigo Kobayashi, Kohei Kusada, Hirokazu Kobayashi, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Hiroshi Kitagawa, Cu–Pd–B Alloy Nanoparticles Synthesized by External Boron Doping Method, Chemistry Letters, 10.1246/cl.200861, 50, 4, 611-614, 2021.04, We present a new synthetic approach for Cu–Pd–B nanoscale alloys. Crystalline face-centered cubic Cu–Pd–B alloy nanoparticles were successfully obtained via an amorphous structure phase caused by external heavy B doping. Elemental mapping with simultaneous energy-dispersive X-ray spectroscopy and energy loss spectroscopy in a scanning transmission electron microscope revealed a solid-solution structure composed of the three elements..
12. Kohei Kusada, Dongshuang Wu,Yusuke Nanba, Michihisa Koyama, Tomokazu Yamamoto, Xuan Quy Tran, Takaaki Toriyama, Syo Matsumura, Ayano Ito, Katsutoshi Sato, Katsutoshi Nagaoka, Okkyun Seo, Chulho Song, Yanna Chen, Natalia Palina, Loku Singgappulige, Rosantha Kumara, Satoshi Hiroi, Osami Sakata, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, Highly Stable and Active Solid‐Solution‐Alloy Three‐Way Catalyst by Utilizing Configurational‐Entropy Effect, Advanced Materials, 10.1002/adma.202005206, 1-7, 2021.03, Since 1970, people have been making every endeavor to reduce toxic emissions from automobiles. After the development of a three‐way catalyst (TWC) that concurrently converts three harmful gases, carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx), Rh became an essential element in automobile technology because only Rh works efficiently for catalytic NOx reduction. However, due to the sharp price spike in 2007, numerous efforts have been made to replace Rh in TWCs. Nevertheless, Rh remains irreplaceable, and now, the price of Rh is increasing significantly again. Here, it is demonstrated that PdRuM ternary solid‐solution alloy nanoparticles (NPs) exhibit highly durable and active TWC performance, which will result in a significant reduction in catalyst cost compared to Rh. This work provides insights into the design of highly durable and efficient functional alloy NPs, guiding how to best take advantage of the configurational entropy in addition to the mixing enthalpy..
13. Sho Kitano, Mei Lee Ooi, Tomokazu Yamamoto, Syo Matsumura, Miho Yamauchi, Catalytic roles and synergetic effects of iron-group elements on monometals and alloys for electrochemical oxidation of ammonia, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20210007, 2021.02, Electrooxidation of NH3 has gained extensive attention for energy and environmental applications such as fuel cell and water purification. Pt-based precious metal alloy catalysts have been intensively studied as anode catalysts for the NH3 electrooxidation whereas applicability of earth-abundant transition metals to catalysts was not sufficiently examined. In this study, we synthesized carbon-supported simple metal-nanoparticle, binary- and ternary-nanoalloy (NA) catalysts composed of Fe-group elements, i.e., Fe, Co and Ni, and systematically investigated catalytic performances on these catalysts for NH3 electrooxidation in alkaline media. We found that the affinity of constituent metals to nitrogen species controls overpotential and durability for the NH3 electrooxidation on Fe-group simple monometal and NA catalysts for the first time. Furthermore, each Fe-group element shows distinctive catalytic features for the NH3 electrooxidation, i.e., Ni ensures chemical stability, Fe effectively lowers overpotential and Co increases current density. The ternary FeCoNi/C shows excellent activities due to combination of all the catalytic features and synergetic effects exerted by the alloying..
14. Satoru Yoshioka, Kazuhiro Yasuda, Syo Matsumura, Takeharu Sugiyama, Eiichi Kobayashi, Transition of Cationic Local Structures in Mg1-xNixAl2O4, Journal of Physical Chemistry C, 10.1021/acs.jpcc.0c08349, 125, 9, 5269-5277, 2021.02, In this study, cationic local structures in the series of MgAl2O4–NiAl2O4 solid solutions (Mg1-xNixAl2O4) were examined using Mg, Al, and Ni K-edge X-ray absorption near-edge structure (XANES). Theoretical calculations of XANES using the all-electron full-potential augmented plane-wave in addition to the local-orbital method were performed to investigate the transition of the cationic local structures depending on their compositions. For the calculations, the atomic coordination was studied using crystal structures of normal and ordered inverse spinels. The experimental spectra of the end members MgAl2O4 and NiAl2O4 were successfully reproduced from the theoretical spectra. Furthermore, the inversion degrees of the end members, analyzed using the calculated spectra, were consistent with previous experimental reports. The Ni2+ ions show three kinds of local structures, and their volume fractions change depending on the composition of Mg1-xNixAl2O4, whereas the Mg2+ ions show two kinds of local structures. The Al3+ ions change the local structure between tetrahedral and octahedral sites to balance the behaviors of Mg2+ and Ni2+ in the compositions. Although the analysis using XANES provides rich information, a theoretical approach is desirable for reliable and quantitative analysis of multication oxides and their disordering..
15. Shinya Okazoe, Lena Staiger, Mirza Cokoja, Kohei Kusada, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Hiroshi Kitagawa, Roland A. Fischer, Enhanced Hydrogenation Catalytic Activity of Ruthenium Nanoparticles by Solid‐Solution Alloying with Molybdenum, European Journal of Inorganic Chemistry, 10.1002/ejic.202001141, 2021, 12, 1186-1189, 2021.02, We report the hydrogenation catalytic activity application of molybdenum–ruthenium (MoRu) solid‐solution alloy nanoparticles (NPs) as catalysts for the hydrogenation of 1‐octene and 1‐octyne. The solid‐solution structure of MoRu NPs was confirmed through scanning transmission electron microscopy (STEM) coupled with energy‐dispersive X‐ray spectroscopy (EDX), and powder X‐ray diffraction (PXRD) measurement. The hydrogenation catalytic activity of these NPs toward 1‐octyne and 1‐octene in tetrahydrofuran (THF) was tested. The hydrogenation catalytic activity of Ru was enhanced by alloying with Mo at the atomic level. An electronic modification of Ru by a charge transfer from Mo to Ru, which could induce the change in the adsorption energy of reactants resulting in enhanced catalytic activity, was observed by X‐ray photoelectron spectroscopy..
16. Dongshuang Wu, Kohei Kusada, Satoru Yoshioka, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Yanna Chen, Okkyun Seo, Jaemyung Kim, Chulho Song, Satoshi Hiroi, Osami Sakata, Toshiaki Ina, Shogo Kawaguchi, Yoshiki Kubota, Hirokazu Kobayashi, Hiroshi Kitagawa, Efficient overall water splitting in acid with anisotropic metal nanosheets, Nature Communications, 10.1038/s41467-021-20956-4, 12, 1145, 1-9, 2021.02, Water is the only available fossil-free source of hydrogen. Splitting water electrochemically is among the most used techniques, however, it accounts for only 4 % of global hydrogen production. One of the reasons is the high cost and low performance of catalysts promoting the oxygen evolution reaction (OER). Here, we report a highly efficient catalyst in acid, that is, solid-solution Ru‒Ir nanosized-coral (RuIr-NC) consisting of 3 nm-thick sheets with only 6 at.% Ir. Among OER catalysts, RuIr-NC shows the highest intrinsic activity and stability. A home-made overall water splitting cell using RuIr-NC as both electrodes can reach 10 mA cm−2geo at 1.485 V for 120 h without noticeable degradation, which outperforms known cells. Operando spectroscopy and atomic-resolution electron microscopy indicate that the high-performance results from the ability of the preferentially exposed {0001} facets to resist the formation of dissolvable metal oxides and to transform ephemeral Ru into a long-lived catalyst..
17. Junko Matsuda, Tomokazu Yamamoto, Shinji Takahashi, Hiroshi Nakanishi, Kazunari Sasaki, Syo Matsumura, In Situ TEM Investigation of Structural Changes in Ni Nanoparticle Catalysts under Gas Atmospheres: Implications for Catalyst Degradation, ACS Applied Nano Materials, 10.1021/acsanm.1c00006, 4, 2, 2175-2182, 2021.02, Ni catalysts with strong hydrogenation and dehydrogenation activities have been used to reform hydrocarbons in natural gas. In this study, microstructural changes, which relate to catalytic degradation for reforming hydrocarbons, in Ni nanocatalysts were observed in situ in oxygen, hydrogen, and methane atmospheres at elevated temperatures using an environmental transmission electron microscope. During oxidation and reduction under oxygen and hydrogen atmospheres, respectively, volumetric changes and mass transfer occurred in the Ni nanoparticle as well as in a larger Ni catalyst particle. On the other hand, the face-centered cubic (fcc) crystal structure of the Ni nanocatalysts transformed to a hexagonal close-packed (hcp) structure as the particles were heated from 250 to 350 °C in methane atmosphere at pressures of 30–40 Pa. The entire Ni nanocatalyst particle had the hcp structure at 350 °C. The spacing of close-packed planes was more than 5% wider in the hcp Ni crystals than it was in fcc Ni. We concluded that carbon and nickel solid solutions formed in the Ni particles as methane thermally decomposed to elemental carbon, which caused the transformation of the Ni crystal structure. Graphite layers appeared, surrounding the Ni particles, after the Ni transformation from fcc to hcp..
18. Xin Fu Tan, Sergey A. Belyakov, Te-Cheng Su, Qinfen Gu, Shiqian Liu, Stuart D. McDonald, Christopher M. Gourlay, Hideyuki Yasuda, Syo Matsumura, Kazuhiro Nogita, Rapid fabrication of tin-copper anodes for lithium-ion battery applications, Journal of Alloys and Compounds, 10.1016/j.jallcom.2021.159031, 867, 159031, 1-10, 2021.02, The intermetallic Cu6Sn5 is ubiquitous in electronic interconnects where research has focused on controlling the size and distribution of this phase for improved performance. Cu6Sn5 also finds application as an anode material for advanced lithium-ion batteries. Cu6Sn5 anodes can be fabricated via an in-situ growth method involving the reaction between molten Sn and the Cu current collector. This manufacturing route offers some advantages over traditional anode fabrication however the process is slow, limiting its practical application. In this work we show the addition of 6 wt% Ni to the Cu current collector greatly accelerates the growth of (Cu,Ni)6Sn5 in Cu-xNi/Sn solid-melt couples, leading to a growth rate of up to 50x faster, reducing the processing time above 200 °C to less than 10  min. This research studies the dynamics of the formation of (Cu,Ni)6Sn5 between Cu-xNi alloys and liquid Sn through real-time observation using synchrotron X-ray imaging. The (Cu,Ni)6Sn5 growth dynamics are characterised, and the growth kinetics are analysed. Subsequently, the mechanism of the accelerated growth is investigated with electron backscatter diffraction and transmission electron microscopy. The results show the accelerated growth is due to the formation of η-(Cu,Ni)6Sn5 grains with two distinct Ni concentration ranges, leading to finer grains and spalling, which in turn facilitates the diffusion of Sn, enhancing the η-(Cu,Ni)6Sn5 formation kinetics..
19. Shinya Okazoe, Kohei Kusada, ukihiro Yoshida, Mitsuhiko Maesato, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, First Observation of Superconductivity in Molybdenum–Ruthenium–Carbon Alloy Nanoparticles, Chemistry Letters, 10.1246/cl.200779, 50, 4, 596-598, 2021.02, We report the synthesis of molybdenum–ruthenium–carbon alloy nanoparticles with molybdenum-rich composition by an annealing treatment following a thermal decomposition. We first found its superconductivity with a transition temperature at around 5 K through the observation of zero resistivity and Meisner effect..
20. Kohei Kusada, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Katsutoshi Sato, Katsutoshi Nagaoka, Kenji Terada, Yasuyuki Ikeda, Yoshinari Hirai, Hiroshi Kitagawa*, Nonequilibrium Flow-Synthesis of Solid-Solution Alloy Nanoparticles: From Immiscible Binary to High-Entropy Alloys, Journal of Physical Chemistry C, 10.1021/acs.jpcc.0c08871, 125, 1, 458-463, 2021.01, Solid-solution alloy nanoparticles (NPs), where the constituents mix at the atomic level, show a variety of attractive properties due to their tunable electronic structures. However, it is still difficult to stably synthesize them, particularly nonequilibrium alloys that consist of combinations immiscible in the bulk. Here, we first report the successful syntheses of solid-solution alloy NPs including PdRu and PdRuIr, which are immiscible in the bulk, and of IrPdPtRhRu high-entropy alloy NPs through a continuous-flow reactor providing a high productivity with high reproducibility. The designed solvothermal flow reactor enabled us to use a lower alcohol as a reductant that cannot be applied in a batch synthesis for these NPs..
21. Xin F.Tan, Qinfen Gu, Dongdong Qu, Adrian X.B.Yong, WenhuiYang, Stuart D.McDonald, SyoMatsumura, KazuhiroNogita, Electrochemically enhanced Cu6Sn5 anodes with tailored crystal orientation and ordered atomic arrangements for lithium-ion battery applications, Acta Materialia,, 201, 341-348, 2020.12, Sn-based anodes are potential replacements for commercial carbon-based lithium-ion battery anodes. Moreover, alloying with Cu improves the cyclability of Sn. This study directly grows Cu6Sn5 crystals on polycrystalline Cu current collectors via a solid-liquid reaction with molten Sn alloys. The Cu6Sn5 crystals grown when a molten Sn-Cu alloy was used have a preferred orientation along the η-Cu6Sn5 (101). In this study, the crystals are tailored to grow along the η-Cu6Sn5 (2-12) preferred orientation by excluding Cu in the molten Sn alloy used as a starting material. The (2-12) oriented electrodes show significantly improved electrochemical properties, displaying a 50th cycle discharge capacity of 762 mAh g-1, a 55% increase over the (101) electrode under the same cycling conditions. The (101) electrode ceased to function at 1C and above, while the (2-12) electrode retained around 480 mAh g-1 at 2C. In addition, the (101) electrode shows the formation of 3-fold superstructures in the crystal lattice; while the (2-12) electrode shows atomic arrangements of a higher crystal symmetry, further facilitating the transportation of Li-ions. Density functional theory calculations confirm that Li-ions prefer to adsorb onto Sn in η-Cu6Sn5 and diffuse through the structure in a zig-zag pattern along the [111] channels with a low barrier energy of 0.705 eV..
22. Chandan Chaudhari, Katsutoshi Sato, Yoshihide Nishida, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura , Yasuyuki Ikeda, Kenji Terada, Naoya Abe, Kohei Kusuda, Hiroshi Kitagawa, Katsutoshi Nagaoka , Chemoselective hydrogenation of heteroarenes and arenes by Pd–Ru–PVP under mild conditions, RSC Advances, 10.1039/D0RA09981C, 10, 72, 44191-44195, 2020.12, Monometallic (Pd, Ru or Rh) and bimetallic (Pd0.5–Ru0.5) alloy NPs catalysts were examined for the hydrogenation of quinoline. Pd–Ru alloy catalyst showed superior catalytic activity to the traditional Rh catalyst. The characterization of Pd0.5–Ru0.5 catalysts, HAADF-EDX mapping and XPS analysis suggested that the alloy state of PdRu catalysts remained unchanged in the recovered catalyst. Furthermore, the catalyst was highly selective for the hydrogenation of different arenes..
23. Shinya Okazoe, Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Shogo Kawaguchi, Yoshiki Kubotae, Hiroshi Kitagawa , Synthesis of Mo and Ru solid-solution alloy NPs and their hydrogen evolution reaction activity, Chemical Communications, 10.1039/D0CC05958G, 56, 92, 14475-14478, 2020.11, We report the synthesis of MoRu solid-solution alloy nanoparticles using carbonyl complexes as a precursor through thermal decomposition. Alloying Ru with an early transition metal, Mo, leads to an electronic structure change, resulting in an enhancement of the catalytic activity for the hydrogen evolution reaction, which overtook that of the Pt catalyst..
24. Daiya Kobayashi, Hirokazu Kobayashi, Dongshuang Wu,Shinya Okazoe,Kohei Kusada, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Shogo Kawaguchi, Yoshiki Kubota, Susan Meñez Aspera, Hiroshi Nakanishi, Shigebumi Arai, Hiroshi Kitagawa, Significant Enhancement of Hydrogen Evolution Reaction Activity by Negatively Charged Pt through Light Doping of W, Journal of the American Chemical Society, 10.1021/jacs.0c07143, 142, 41, 17250-17254, 2020.09, We report novel PtW solid-solution nanoparticles (NPs) produced through electrochemical cleaning of core/shell PtW@WO3 NPs. The resulting PtW NPs achieved a record hydrogen evolution reaction (HER) performance as a class of Pt-based solid-solution alloys. A current density of 10 mA cm–2 was reached with an overpotential of 19.4 mV, which is significantly lower than that of a commercial Pt catalyst (26.3 mV). The PtW NPs also exhibited long-term stability. Theoretical calculations revealed that negatively charged Pt atoms adjacent to a W atom provide favorable hydrogen adsorption energies for the HER, realizing significantly enhanced HER activity..
25. Bo Huang, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Yoshihide Nishida, Katsutoshi Sato, Katsutoshi Nagaoka, Masaaki Haneda, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa , Coreduction methodology for immiscible alloys of CuRu solid-solution nanoparticles with high thermal stability and versatile exhaust purification ability, Chemical Science, 10.1039/D0SC03373A, 11, 42, 11413-11418, 2020.09, This study provides a coreduction methodology for solid solution formation in immiscible systems, with an example of a whole-region immiscible Cu–Ru system. Although the binary Cu–Ru alloy system is very unstable in the bulk state, the atomic-level well-mixed CuRu solid solution nanoparticles were found to have high thermal stability up to at least 773 K in a vacuum. The exhaust purification activity of the CuRu solid solution was comparable to that of face-centred cubic Ru nanoparticles. According to in situ infrared measurements, stronger NO adsorption and higher intrinsic reactivity of the Ru site on the CuRu surface than that of a pure Ru surface were found, affected by atomic-level Cu substitution. Furthermore, CuRu solid solution was a versatile catalyst for purification of all exhaust gases at a stoichiometric oxygen concentration..
26. Xuan Quy Tran, Yoshiki Kono, Tomokazu Yamamoto, Kohei Kusada, Hiroshi Kitagawa, Syo Matsumura, Statistical Evaluation of the Solid-Solution State in Ternary Nanoalloys, Journal of Physical Chemistry C, 10.1021/acs.jpcc.0c06813 , 124, 39, 21843-21852, 2020.08, Quantitative evaluation of the alloying state in nanoalloy systems is key to understanding their functional properties in a diverse range of applications spanning from catalysis and plasmonics to biomedicine and so forth. Here, we develop a method to statistically and visually represent the sub-nanometer local compositional distribution in ternary nanoparticles (NPs) in terms of ternary histograms and kernel density estimation analysis. Further descriptive statistics is performed within the mathematical framework of compositional data analysis to account for the constant-sum constraint and positivity inherent to the nature of compositional data. The approach has been demonstrated on several conceptual particle models and real systems, namely, Pd–Rh–Ru and Ag–Au–Pd NPs, utilizing experimental X-ray energy-dispersive spectroscopy (XEDS) maps acquired from a scanning transmission electron microscope. We regard this as a useful tool for extending to other well-known configurations such as uniformly mixed solid solutions, core–shell, or phase-decomposed clusters often encountered in other nanoalloy systems. Proposed solutions to overcome common problems associated with NPs such as low X-ray counting and XEDS spectral overlapping are also presented and discussed..
27. Dongshuang Wu, Kohei Kusada, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Ibrahima Gueye, Okkyun Seo, Jaemyung Kim, Satoshi Hiroi, Osami Sakata, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, On the electronic structure and hydrogen evolution reaction activity of platinum group metal-based high-entropy-alloy nanoparticles, Chemical Science, 10.1039/D0SC02351E, 11, 47, 12731-12736, 2020.08, We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H2SO4 and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts..
28. V. T. Nguyen, M. Qian, Z. Shi, X. Q. Tran, D. M. Fabijanic, J. Joseph, D. D. Qu, S. Matsumura, C. Zhang, F. Zhang, J. Zou, Cuboid-like nanostructure strengthened equiatomic Ti–Zr–Nb–Ta medium entropy alloy, Materials Science and Engineering A, 10.1016/j.msea.2020.140169, 798, 140168, 2020.08, This study investigates the effect of annealing treatment on the phase transformation and mechanical properties of the equiatomic TiZrNbTa MEA from room temperature to 1200 °C. After annealing at 1200 °C for 24h, the single solid-solution body-centred cubic (BCC) phase in the as-cast Ta25Zr25Nb25Ti25 transformed into an extremely high number density (~103/μm2) of Ta–Nb-rich BCC nanocuboidal phase (28 ± 10 nm square, BCC1) and a nanostrip-like Zr-rich BCC phase (3 ± 2 nm thick, BCC2). The phase separation from BCC to BCC1 and BCC2 arises from two primary reasons: (i) the high positive mixing enthalpy of both Ta–Zr and Nb–Zr (strong tendency to separation between each pair), and (ii) the 3–4 orders of magnitude higher mobility of Zr than Ta, Nb and Ti in these MEAs (kinetically driven). Detailed CALPHAD simulations of phase formation in this MEA agreed with experiments and provided insightful phase transformation details. The calculated diffusion distance of Zr (~4.1 nm) from the CALPHAD data corresponds to the measured Zr-rich nanostrip thickness (3 ± 2 nm). The nanocuboidal BCC1-BCC2 structure exhibited 112<111>-type of twinning deformation under compression at room temperature. The Ta25Zr25Nb25Ti25 MEA retained yield strength of ~410 MPa at 1000 °C and ~210 MPa at 1200 °C. The phase transformation during cooling after annealing and the microstructural evolution during compression at temperatures from 600 °C to 1200 °C were characterized and discussed in detail..
29. Xin Fu Tan, Adrian Xiao, Bin Yong, Qinfen Gu, Wenhui Yang, Kohei Aso, Syo Matsumura, Stuart D. McDonald, Kazuhiro Nogita, The Effects of Trace Sb and Zn Additions on Cu6Sn5 Lithium-Ion Battery Anodes, Journal of Nanoscience and Nanotechnology, 10.1166/jnn.2020.18538, 20, 8, 5182-5191, 2020.08, Sn-based compounds are promising candidates for application as anodes in lithium-ion batteries (LIBs) due to the favourable storage capacity of Sn at 993 mAh g−1 compared to carbon at 372 mAh g−1. The use of Sn-based anodes also avoids some of the safety concerns associated with carbon anodes. However, the large volume changes during lithiation and delithiation of pure Sn anodes often results in poor cyclic performance. Alloying Sn with Cu, an element inactive with respect to Li, buffers the expansion stresses and can improve cycling performance. Cu6Sn5 is therefore a promising candidate anode material. In this work, the effects of Sb and Zn additions on the morphology, crystal structure, atomic arrangements and the electrochemical performance of the anodes were evaluated. Characterisation with synchrotron X-ray powder diffraction and Cs -corrected transmission electron microscopy revealed the larger lattice parameters, higher symmetry crystal structures and well-ordered atomic arrangements in the Sb and Zn modified electrodes, which resulted in a more than 50% increase in cycling capacity from 490 mAh g−1 to 760 mAh g−1..
30. Zhiheng An, Wenhui Yang, Hongyi Zhan, Bin Hu, Qigui Wang, Syo Matsumura, Gang Sha, , On the strengthening effect of Al-Cr-Si dispersoid in an Al-Si-Mg-Cu casting alloy with Cr addition, Materials Characterization, 10.1016/j.msea.2020.140169, 166, 110457, 2020.08, In the present study, chromium (Cr) was added to an Al-Si-Mg-Cu casting alloy to investigate the strengthening effect of face-centered cubic structured Al-Cr-Si dispersoid precipitated in the intra-dendritic region. The Al-Si-Mg-Cu alloy with Cr addition shows a stronger hardening response to solution treatment than the Al-Si-Mg-Cu alloy without Cr addition, which was ascribed to the precipitation of Al-Cr-Si dispersoid occurred during solution treatment. Detailed characterization on Al-Cr-Si dispersoid via scanning transmission electron microscopy (STEM) indicates that there is a preferential orientation relationship between Al-Cr-Si dispersoid and Al matrix. This is in a good agreement with the prediction by the edge-to-edge model. In addition, the present study unveils a contradiction between the castability of Al-Si-Mg-Cu-Cr alloy and strengthening effect of Al-Cr-Si dispersoid. This contradiction was discussed based on thermodynamic calculations. Tensile properties of the Cr-free and Cr-containing Al-Si-Mg-Cu alloys after ageing treatment have been characterized. Unfortunately, strengthening effect of Al-Cr-Si dispersoid was not retained in the Cr-containing alloy after ageing treatment, owing to the strong interaction between Al-Cr-Si dispersoid and age strengthening elements during quenching. Quench-induced particles were extensively nucleated on the dispersoid, which may result from the synergic effects of dispersoid/matrix interphase energy and Si enrichment in the dispersoid. The undesirable quench-induced particles attached to Al-Cr-Si dispersoid consumed age strengthening elements in the Al matrix and undermined the thermal stability of Al-Cr-Si dispersoid..
31. Dongshuang Wu, Kohei Kusada, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, Platinum-Group-Metal High-Entropy-Alloy Nanoparticles, Journal of the American Chemical Society, 10.1021/jacs.0c04807, 142, 32, 13833-13838, 2020.07, The platinum-group metals (PGMs) are six neighboring elements in the periodic table of the elements. Each PGM can efficiently promote unique reactions, and therefore, alloying PGMs would create ideal catalysts for complex or multistep reactions that involve several reactants and intermediates. Thus, high-entropy-alloy (HEA) nanoparticles (NPs) of all six PGMs (denoted as PGM-HEA) having a great variety of adsorption sites on their surfaces could be ideal candidates to catalyze complex reactions. Here, we report for the first time PGM-HEA and demonstrate that PGM-HEA efficiently promotes the ethanol oxidation reaction (EOR) with complex 12-electron/12-proton transfer processes. PGM-HEA shows 2.5 (3.2), 6.1 (9.7), and 12.8 (3.4) times higher activity than the commercial Pd/C, Pd black and Pt/C catalysts in terms of intrinsic (mass) activity, respectively. Remarkably, it records more than 1.5 times higher mass activity than the most active catalyst to date. Our findings pave the way for promoting complex or multistep reactions that are seldom realized by mono- or bimetallic catalysts..
32. Wenhui Yang, Xuan Quy Tran, Tomokazu Yamamoto, Satoru Yoshioka, Flora Somidin, Kazuhiro Nogita, and Syo Matsumura, Atomic locations of minor dopants and their roles in the stabilization of η-Cu6Sn5, Physical Review Materials, 10.1103/PhysRevMaterials.4.065002, 4, 6, 065002, 2020.06, Chemical modification using only small amounts of elements such as Zn, In, Sb, or Ni has proven to be an effective means to control the desirable crystal structure of hexagonal η-Cu6Sn5 over a wide thermally operating window, typically found in Pb-free Sn-based soldering or Li-ion battery anode applications. Though appealing, the underlying mechanisms on the role of these dopants remain incomplete and their atomic arrangements within the η-Cu6Sn5 lattices have not yet been experimentally determined. In the current study, we directly reveal the atomic positions of Zn, In, and Sb at the Sn sites of η-Cu6Sn5 via atomic-scale x-ray energy dispersive spectroscopy (XEDS) maps utilizing advanced Cs-corrected scanning transmission electron microscopy. The use of advanced statistical algorithms including Poisson non-local principal component analysis and lattice averaging enables the fine resolution of weak XEDS maps from trace dopant elements. Our first-principles calculations further identify the influence of dopants at these atomic sites on the overall energetics, electronic structures, as well as local bonding environments, leading to the most favorable situations for η-Cu6Sn5 stabilization..
33. Shiqian Liu, Guang Zeng, Wenhui Yang, Stuart McDonald, Qinfen Gu, Syo Matsumura, Kazuhiro Nogita, Interfacial Reactions between Ga and Cu-10Ni Substrate at Low Temperature, ACS Applied Materials & Interfaces, 10.1021/acsami.0c02032, 12, 18, 21045-21056, 2020.04, Ga alloys have been attracting significant renewed attention for low-temperature bonding applications in electronic packaging. This study systematically investigates the interfacial reaction between liquid Ga and Cu-10Ni substrates at 30 °C. In addition to CuGa2 formed from binary Ga/Cu couples, a layer of nanocrystalline Ga5Ni and CuGa2 formed between the Cu-10Ni substrate and the blocklike micrometer scale CuGa2 layer. The growth of interfacial intermetallics (IMCs) on the Cu-10Ni substrate was substantially accelerated compared to the IMC growth in binary Ga/Cu couples. Reaction kinetics study shows the IMC growth from the Cu-10Ni substrate was controlled by reaction and volume diffusion, while the IMC growth from the Cu substrate was controlled by volume diffusion. It is also found that the presence of Ni within the CuGa2 phase resulted in improved thermal stability and a smaller coefficient of thermal expansion during heating from 25 to 300 °C, using synchrotron XRD analysis. There was least thermal expansion anisotropy among most of the IMCs that form in conventional Sn-based solder alloys, including Cu6Sn5 and so forth. It is concluded that using a Cu-10Ni substrate as opposed to a Cu substrate could achieve sufficient metallurgical bonding within shorter processing time. The results have implications for broadening the application temperatures when using Ga as a low-temperature joining material..
34. Yuta Ogura, Takahiro Asai, Katsutoshi Sato, Shin-ichiro Miyahara, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka , Effect of Calcination and Reduction Temperatures on the Catalytic Activity of Ru/La0.5Ce0.5O1.75 for Ammonia Synthesis under Mild Conditions, Energy Technology, 10.1002/ente.202000264, 2020.04, Ammonia is a potential carrier of hydrogen as a zero‐emission fuel. Herein, the effects of calcination and reduction temperatures on the ammonia‐synthesis activity of Ru/La0.5Ce0.5O1.75 are investigated under mild synthesis conditions (≤400 °C, ≤3 MPa), which are the preferred conditions for the storage of hydrogen as an energy source. The highest catalytic activity is obtained after calcination of the support at 700 °C and reduction of the catalyst at 650 °C. Calcination using a higher temperature than that used for reduction results in the induction of a strong metal–support interaction (SMSI) effect. This high‐temperature calcination also provides heat resistance to the support, which prevents sintering of the primary support particles during reduction. Thus, calcination and reduction at temperatures higher than those normally used for the preparation of Ru catalysts provide a novel approach for obtaining supported highly dispersed Ru catalysts exhibiting the SMSI effect and high catalytic activities..
35. Satoru Yoshioka, Konosuke Tsuruta, Tomokazu Yamamoto, Kazuhiro Yasuda, Syo Matsumura, Takeharau Sugiyama, Yojiro Oba, Norito Ishikawa,Eiichi Kobayashi,Koji Okudaira, Local structure investigations of accumulated damage in irradiated MgAl2O4, Journal of the American Ceramic Society, 10.1111/jace.17101, 103, 8, 4654-4663, 2020.03, Damaged structures in the MgAl2O4 spinel induced by swift heavy ions were investigated using the X‐ray absorption near edge structure (XANES) and small angle X‐ray scattering (SAXS). Increasing the fluence of 100 MeV Xe ions leads to increased SAXS intensity and XANES spectral changes on both Mg and Al K‐edges. The damaged regions of ion tracks were observed by SAXS to be cylindrical in shape with a diameter of 5 nm. The theoretical XANES spectra indicated that the changes in the experimental spectra were due to the cationic disordering between tetrahedral and octahedral sites. This disordering caused an increase in the inversion degree of the cations. Furthermore, the quantitative analysis of the XANES spectra revealed the preferential occupation of cations at the octahedral sites at high fluence..
36. Lianlian Deng, Mai Thanh Nguyen, Jingming Shi, Yuen-ting Rachel Chau, Tomoharu Tokunaga, Masaki Kudo, Syo Matsumura, Naoyuki Hashimoto, Tetsu Yonezawa, Highly correlated size and composition of Pt/Au alloy nanoparticles via magnetron sputtering onto liquid, Langmuir, 10.1021/acs.langmuir.0c00152, 36, 12, 3004-3015, 2020.03, Pt/Au alloy nanoparticles (NPs) in a wide composition range have been synthesized by room-temperature simultaneous sputter deposition from two independent magnetron sources onto liquid PEG (MW = 600). The prepared NPs were alloyed with the face-centered cubic (fcc) structure. In addition, the particle sizes, composition, and shape are strongly correlated but can be tailored by an appropriate variation of the sputtering parameters. No individual particle but large agglomerates with partial alloy structure formed at Pt content of less than 16 atom %. Highly dispersed NPs with no agglomeration were observed in PEG when the quantity of Pt is more than 26 atom %. On the other hand, a small amount of Pt could terminate the agglomeration of Au when sputtering on the grids for transmission electron microscope observation. Our experiment and computer simulation carried out by two different methods indicate that the composition-dependent particle size of Pt/Au can be explained by the atomic concentration, formation energy of the cluster, and interaction between different metal atoms and the PEG molecule..
37. Yoshimasa Aoyama, Hirokazu Kobayashi, Tomokazu Yamamoto,Takaaki Toriyama, Syo Matsumura, Masaaki Haneda, Hiroshi Kitagawa, Significantly enhanced CO oxidation activity induced by a change in the CO adsorption site on Pd nanoparticles covered with metal–organic frameworks, Chemical Communications, 10.1039/D0CC00566E, 56, 3839-3842, 2020.03, We report the significantly enhanced CO oxidation activity of Pd nanoparticles covered with [Zr6O4(OH)4(BDC)6] (UiO-66, BDC = 1,4-benzenedicarboxylate). The catalytic activity was much higher than those of Pd and Ru nanoparticles on ZrO2. The origin of the enhancement was suggested to be a change in the CO adsorption properties on Pd nanoparticles..
38. Satoshi Hata, Hiromitsu Furukawa, Takashi Gondo,Daisuke Hirakami, Noritaka Horii, Ken-Ichi Ikeda, Katsumi Kawamoto, Kosuke Kimura, Syo Matsumura, Masatoshi Mitsuhara, Hiroya Miyazaki, Shinsuke Miyazaki, Mitsu Mitsuhiro Murayama, Hideharu Nakashima, Hikaru Saito, Masashi Sakamoto, Shigeto Yamasaki, Electron tomography imaging methods with diffraction contrast for materials research, Microscopy, 10.1093/jmicro/dfaa002, 63, 3, 141-155, 2020.03, Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) enable the visualization of three-dimensional (3D) microstructures ranging from atomic to micrometer scales using 3D reconstruction techniques based on computed tomography algorithms. This 3D microscopy method is called electron tomography (ET) and has been utilized in the fields of materials science and engineering for more than two decades. Although atomic resolution is one of the current topics in ET research, the development and deployment of intermediate-resolution (non-atomic-resolution) ET imaging methods have garnered considerable attention from researchers. This research trend is probably not irrelevant due to the fact that the spatial resolution and functionality of 3D imaging methods of scanning electron microscopy (SEM) and X-ray microscopy have come to overlap with those of ET. In other words, there may be multiple ways to carry out 3D visualization using different microscopy methods for nanometer-scale objects in materials. From the above standpoint, this review paper aims to (i) describe the current status and issues of intermediate-resolution ET with regard to enhancing the effectiveness of TEM/STEM imaging and (ii) discuss promising applications of state-of-the-art intermediate-resolution ET for materials research with a particular focus on diffraction contrast ET for crystalline microstructures (superlattice domains and dislocations) including a demonstration of in situ dislocation tomography..
39. ShiqianLiu, Dongdong Qu, Stuart McDonald, Qinfen Gu, SyoMatsumura, KazuhiroNogita, Intermetallic formation mechanisms and properties in room-temperature Ga soldering, Journal of Alloys and Compounds, 10.1016/j.jallcom.2020.154221, 826, 154221, 1-11, 2020.06, Ga and Ga-based alloys have received significant attention due to their potential applications as liquid metals and also for low temperature, or even room temperature, bonding in microelectronics. This study investigates the effect of In and Sn on the interfacial reactions between eutectic Ga-based alloys and Cu substrates at room temperature. The interfacial microstructures are characterised by electron microscopy and Synchrotron powder x-ray diffraction. In-situ heating observations are carried out to verify the thermal expansion properties of the intermetallic compounds formed with In and/or Sn additions in the Ga-based alloy/Cu reactions. The alloying elements are found to decrease the coefficient of thermal expansion of CuGa2 as the temperature increases. In and Sn are also examined with respect to their influence on the wettability of Ga-based alloys on Cu substrates under an argon atmosphere. The results are important to consider in the development of bonding processes involving Ga and Ga alloys..
40. Shusaku Shoji, Xiaobo Peng, Akira Yamaguchi, Ryo Watanabe, Choji Fukuhara, Yohei Cho, Tomokazu Yamamoto, Syo Matsumura, Min-Wen Yu, Satoshi Ishii, Takeshi Fujita, Hideki Abe, Masahiro Miyauchi , Photocatalytic uphill conversion of natural gas beyond the limitation of thermal reaction systems, Nature Catalysis, 10.1038/s41929-019-0419-z, 3, 148-153, 2020.01, Dry reforming of methane is one of the key reactions to exploit natural gas feedstocks by their catalytic conversion to synthesis gas (CH4 + CO2 → 2H2 + 2CO), which is used in the production of transportable liquid fuel. However, this reaction suffers from thermodynamic conversion limits and high thermal energy requirements. Herein we report that a SrTiO3-supported rhodium (Rh/STO) catalyst efficiently promotes methane reforming under ultraviolet light irradiation without heat supply at low temperatures, which cannot be achieved by conventional thermal catalysis. The photoexcited holes and electrons are used for CH4 oxidation over STO and CO2 reduction over rhodium, respectively. Isotope analysis clarified that the lattice oxygens (O2−) act as mediator to drive dry reforming of methane. The materials design of Rh/STO can be extended in principle to diverse uphill reactions that utilize photon energy to obtain valued products from different carbon resources..
41. Katsutoshi Sato, Shin-ichiro Miyahara, Yuta Ogura, Kotoko Tsujimaru, Yuichiro Wada, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka, Surface dynamics for creating highly active Ru sites for ammonia synthesis: accumulation of a low-crystalline, oxygen-deficient nano-fraction, ACS Sustainable Chemistry & Engineering, 10.1021/acssuschemeng.9b06299, 8, 7, 2726-2734, 2020.01, To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity per weight of catalyst of Ru/Ba/LaCeOx, pre-reduced at 700 °C, is the highest among oxide-supported Ru catalysts, 52.3 mmol h⁻¹ gcat⁻¹ at 350 ºC, 1.0 MPa. The turnover frequency of Ru/Ba/LaCeOx at 350 °C was more than 8 times that of Cs⁺/Ru/MgO which is a well-known active catalyst used as a benchmark. Furthermore, hydrogen poisoning, a typical drawback for oxide-supported Ru catalysts, was effectively suppressed over the catalyst. Scanning transmission electron microscopy observations with energy dispersive X-ray spectrometry and electron energy loss spectroscopy analysis revealed that a low-crystalline, oxygen-deficient nano-fraction including Ba²⁺, Ce³⁺ and La³⁺ had accumulated on the Ru particles. This unique structure was obtained by exploiting the surface dynamics of alkaline earth compounds and thermostable rare earth oxides that contain redox-active atoms during the reduction at unusually high temperature. The nano-fraction showed strong electron-donating ability because of the strong basicity of the included cations, removal of carbonate, and formation of oxygen defect sites that eliminated electron-withdrawing O²⁻ anions from the interface between the nano-fraction and Ru atom. Electrons were therefore effectively donated to antibonding π-orbitals of the N2 molecules via Ru in contact with the nano-fraction, and N≡N bond cleavage, which is the rate-determining step for ammonia synthesis, was promoted..
42. Takuo Wakisaka, Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Hiroshi Kitagawa, Catalytic activity of Rh nanoparticles with high-index faces for hydrogen evolution reaction in alkaline solution, Chemistry Letters, 10.1246/cl.190830, 2019.12, Rh nanoparticles (NPs) with various shapes exposing different faces were synthesized and their catalytic activities for hydrogen evolution reaction (HER) were investigated. Rh NPs showed a shape dependence on the catalytic activities and the activity of Rh NPs with high-index faces was higher than the others..
43. Xin F. Tan, Wenhui Yang, Kohei Aso, Syo Matsumura, Stuart D. McDonald, Kazuhiro Nogita, Evidence of copper separation in lithiated Cu6Sn5 lithium-ion battery anodes, ACS Applied Energy Materials, 10.1021/acsaem.9b02014, 2019.12, Intermetallics such as Cu6Sn5, NiSi2, and CuGa2 etc., are promising candidate materials to replace carbon-based lithium-ion battery anodes. However, the lithiation reactions of these anodes often involve the separation of the inactive phases, a slow process that retards the lithiation kinetics and deactivates their role as a stress buffer. This research visualizes the separated Cu in a lithiated Cu6Sn5 anode by advanced transmission electron microscopy techniques. Cu nanospheres of 3–4 nm are found homogeneously distributed in both Li(13+y)Sn5 and Li13Cu6Sn5 phases, suggesting that Cu is transported by long-range diffusion from the reaction site at the Li(13+y)Sn5/Li13Cu6Sn5 phase boundaries..
44. Takuo Wakisaka, Kohei Kusada, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Gueye Ibrahima, Okkyun Seo, Jaemyung Kim, Satoshi Hiroi, Osami Sakata, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, Discovery of face-centred cubic Os nanoparticles, Chemical Communications, 10.1039/C9CC09192K, 56, 3, 372-374, 2019.11, We succeeded in controlling the crystal structure of osmium (Os) nanoparticles (NPs). Although Os adopts only a hexagonal close-packed (hcp) structure in the bulk state, a face-centred cubic (fcc) Os was synthesized by a chemical reduction method using an Os acetylacetonate complex as a precursor..
45. Takuo Wakisaka, Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Hiroshi Akiba, Osamu Yamamuro, Kazutaka Ikeda, Toshiya Otomo, Natalia Palina, Yanna Chen, Loku S. R. Kumara, Chulho Song, Osami Sakata, Wei Xie, Michihisa Koyama, Yoshiki Kubota, Shogo Kawaguchi, Ryan L. Arevalo, Susan M. Aspera, Elvis F. Arguelles, Hiroshi Nakanishi, Hiroshi Kitagawa, Rational synthesis for a noble metal carbide, Journal of the American Chemical Society, 10.1021/jacs.9b09219, 142, 3, 1247-1253, 2019.11, Transition metal carbides have attractive physical and chemical properties that are much different from their parent metals. Particularly, noble metal carbides are expected to be promising materials for a variety of applications, particularly as efficient catalysts. However, noble metal carbides have rarely been obtained because carbide phases do not appear in noble metal–carbon phase diagrams and a reasonable synthesis method to make noble metal carbides has not yet been established. Here, we propose a new synthesis method for noble metal carbides and describe the first synthesis of rhodium carbide using tetracyanoethylene (TCNE). The rhodium carbide was synthesized without extreme conditions, such as the very high temperature and/or pressure typically required in conventional carbide syntheses. Moreover, we investigated the electronic structure and catalytic activity for the hydrogen evolution reaction (HER). We found that rhodium carbide has much higher catalytic activity for HER than pure Rh. Our study provides a feasible strategy to create new metal carbides to help advance the field of materials science..
46. Xin F. Tan, Stuart D. McDonald, Qinfen Gu, Lianzhou Wang, SyoMatsumura, Kazuhiro Nogita, The effects of Ni on inhibiting the separation of Cu during the lithiation of Cu6Sn5 lithium-ion battery anodes, Journal of Power Sources, 10.1016/j.jpowsour.2019.227085, 440, 227085, 1-12, 2019.11, Sn-based lithium-ion battery (LIB) anodes have a lower risk of lithium dendrite formation and a higher storage capacity of 993 mAh g−1 vs. 372 mAh g−1 compared to carbon-based anodes. Alloying Sn with Cu can reduce the reaction stresses in the anode, and Cu6Sn5 is therefore a promising candidate material to replace carbon-based anodes. However, the separation of Cu during the second stage of the lithiation reaction results in slow kinetics and degrades the cyclability of the anodes. This study proposes an effective method to inhibit the separation of Cu via the addition of Ni. Ni occupies the Cu positions in the Cu6Sn5 crystal structures to form (Cu, Ni)6Sn5, and therefore alters the crystal structure of the anode, leading to the formation of superstructures. As a result, Ni partially blocks the diffusion pathways of Li and therefore inhibits the Cu separation reaction, while the superstructure provides additional Li storage sites to increase the capacity of the anodes. Ni also refines the grain size of Cu6Sn5, leading to faster kinetics. The reaction mechanisms of the modified anodes are confirmed by in-situ synchrotron X-ray powder diffraction and ex-situ high voltage transmission electron microscopy..
47. Matthew Dargusch, Xiao-Lei Shi, Xuan Quy Tran, Tianli Feng, Flora Somidin, Xin Tan, Weidi Liu, Kevin Jack, Jeffrey Venezuela, Hiroshi Maeno, Takaaki Toriyama, Syo Matsumura, Sokrates T. Pantelides, Zhi-Gang Chen*, In-situ observation of the continuous phase transition in determining the high thermoelectric performance of polycrystalline Sn0.98Se, Journal of Physical Chemistry Letters , 10.1021/acs.jpclett.9b02818, 10, 21, 6512-6517, 2019.10, We report a comprehensive in-situ phase-change study on polycrystalline Sn0.98Se via high-temperature X-ray diffraction and in-situ high-voltage transmission electron microscopy from room temperature to 843 K. The results clearly demonstrate a continuous phase transition from Pnma to Cmcm starting from 573 to 843 K, rather than a sudden transition at 800 K. We also find that the thermal-conductivity rise at high temperature after the phase transition, as commonly seen in pristine SnSe, does not occur in Sn0.98Se, leading to a high thermoelectric figure of merit. Density functional theory calculations reveal the origin to be the suppression of bipolar thermal conduction in the Cmcm phase of Sn0.98Se due to the enlarged bandgap. This work fills the gap of in-situ characterization on polycrystalline Sn0.98Se, and provides new insights into the outstanding thermoelectric performance of polycrystalline Sn0.98Se.
48. Shiqian Liu, Stuart McDonald, Qinfen Gu, Syo Matsumura, Dongdong Qu, Keith Sweatman, Tetsuro Nishimura, Kazuhiro Nogita, Properties of CuGa2 formed between liquid Ga and Cu substrates at room temperature, Journal of Electronic Materials, 10.1007/s11664-019-07688-4, 49, 128-139, 2019.10, Ga and Ga-based alloys have received significant attention due to their potential application in the liquid state for low-temperature bonding in microelectronics. This study investigated the interfacial reactions between liquid Ga and pure Cu substrates at room temperature. The directional thermal expansion behaviour of the resulting CuGa2 was analysed by synchrotron x-ray powder diffraction with supporting observations of single crystal foils in high-voltage transmission electron microscopy. The mechanical properties of CuGa2 were evaluated by nano-indentation. CuGa2 was found to have advantages over other intermetallics that are present in assemblies made with current generation lead-free solders, including Ag3Sn, Cu6Sn5 and Cu3Sn. In addition to enabling lower process temperatures, solder alloys that form CuGa2 at the interface with Cu offer the possibility of providing more reliable connections in the very small joints that play an increasingly important role as the trend to miniaturisation of electronics continues..
49. Shiqian Liu, Wenhui Yang, Youichirou Kawami, Qinfen Gu, Syo Matsumura, Dongdong Qu, Stuart McDonald, Kazuhiro Nogita, Effects of Ni and Cu antisite substitution on the phase stability of CuGa2 from liquid Ga/Cu-Ni interfacial reaction, ACS Applied Materials & Interfaces, 10.1021/acsami.9b10630, 11, 35, 32523-32532, 2019.08, Ga and Ga-based alloys have received significant attention due to their potential applications as liquid metals and also for the bonding of materials in microelectronics near room temperature. This study investigates the phase stability of CuGa2 phase as a product of the interfacial reaction between liquid Ga and Cu-10Ni substrates at room temperature. In the binary Ga-Cu system CuGa2 is decomposed into liquid Ga and Cu9Ga4 as the temperature increases to around 260 °C, which prevents the widespread application of this alloy. In contrast to CuGa2 grown from a pure Cu substrate, that from the Cu-10Ni substrate shows an increase in the decomposition temperature during heating from 25 °C to 300 °C) According to our first-principle calculations, there is only a minor difference in the total free energy between Ni solute at the Cu sublattice and the Ga sublattice in the tetragonal CuGa2 crystal structure. This result indicates that both of the sublattices can accommodate the dilute Ni solute with comparable probability. Regardless of the sublattice where the Ni impurities are located, the presence of diluted Ni in the matrix stabilises the CuGa2 system by inducing some localized Ni-3d states at energy levels near the Fermi level. It is also shown the formation of Cu antisite defects, which also stabilise CuGa2, is preferable if the CuGa2 matrix is grown on a Ni-containing substrate..
50. Min Hong, Yuan Wang, Tianli Feng, Qiang Sun, Shengduo Xu, Syo Matsumura, Sokrates T. Pantelides, Jin Zou, Zhi Gang Chen, Strong phonon–phonon interactions securing extraordinary thermoelectric Ge1–xSbxTe with Zn-alloying-induced band alignment, Journal of the American Chemical Society, 10.1021/jacs.8b12624, 141, 4, 1742-1748, 2019.06, The ability of substitution atoms to decrease thermal conductivity is usually ascribed to the enhanced phonon-impurity scattering by assuming the original phonon dispersion relations. In this study, we find that 10% SbGe alloying in GeTe modifies the phonon dispersions significantly, closes the acoustic–optical phonon band gap, increases the phonon–phonon scattering rates, and reduces the phonon group velocities. These changes, together with grain boundaries, nanoprecipitates, and planar vacancies, lead to a significant decrease in the lattice thermal conductivity. In addition, an extra 2–6% Zn alloying decreases the energy offset between valence band edges at L and Σ points in Ge<sub>1–x</sub>Sb<sub>x</sub>Te that is found to be induced by the Ge 4s<sup>2</sup> lone pairs. Since Zn is free of s<sup>2</sup> lone pair electrons, substituting Ge with Zn atoms can consequently diminish the Ge 4s<sup>2</sup> lone-pair characters and reduce the energy offset, resulting in two energetically merged valence band maxima. The refined band structures render a power factor up to 40 μW cm<sup>–1</sup> K<sup>–2</sup> in Ge<sub>0.86</sub>Sb<sub>0.1</sub>Zn<sub>0.04</sub>Te. Ultimately, a superhigh zT of 2.2 is achieved. This study clarifies the impacts of high-concentration substitutional atoms on phonon band structure, phonon–phonon scattering rates, and the convergence of electron valence band edges, which could provide guidelines for developing high-performance thermoelectric materials..
51. Mo Rigen He, Shuai Wang, Ke Jin, Hongbin Bei, Kazuhiro Yasuda, Syo Matsumura, Kenji Higashida, Ian M. Robertson, A comparative characterization of defect structure in NiCo and NiFe equimolar solid solution alloys under in situ electron irradiation, Scripta Materialia, 10.1016/j.scriptamat.2019.03.008, 166, 96-101, 2019.06, Dislocation loops in NiCo and NiFe, both being single-phase, equimolar solid solution alloys, are generated by in situ high-voltage electron irradiation and characterized inside a transmission electron microscope. In addition to the different defect growth rates, the two alloys present dislocation loops with distinct shape evolution and element segregation, which reflect the element-sensitive, intrinsic properties (e.g., defect energetics, lattice distortion, and local ordering) of the alloys. These results provide evidence that the structure and dynamics of radiation-induced defects in concentrated alloys depend on not only the number but also the species of alloying elements..
52. A.M.Manzoni, S.Haas, J.M.Yu, H.M.Daoud, U.Glatzel, H.Aboulfadl, F.Mücklich, R.Duran, G.Schmitz, D.M.Többens, S.Matsumura, F.Vogel, N.Wanderka, Evolution of γ/γ' phases, their misfit and volume fractions in Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy, Materials Characterization, 10.1016/j.matchar.2019.06.009, 154, 363-376, 2019.06, Recently introduced Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy has been investigated in the as-cast state and after heat treatment in a thorough characterization. The combination of optical, scanning and transmission electron microscopy, three dimensional atom probe and x-ray diffraction, both at lab and synchrotron level provides precise information of the microstructural evolution.
After the typical dendritic solidification the alloy reveals dendritic cores consisting of γ and γ' phases and interdendritic regions consisting of η and Heusler type phases. Homogenization removes the interdendritic regions and their phases and subsequent annealing produces a microstructure similar to Ni based superalloys consisting of γ/γ' phases. In addition, about 50 μm sized Al-Ni rich needle-shaped precipitates of Heusler type structure can be observed. The four phases and their evolution with heat treatment are investigated in detail. Special focus lies on the γ/γ' misfit determination and the determination of volume fractions by different methods..
53. Lianlian Deng, Mai Thanh Nguyen, Shuang Mei, Tomoharu Tokunaga, Masaki Kudo, Syo Matsumura, Tetsu Yonezawa, Preparation and growth mechanism of Pt/Cu alloy nanoparticles by sputter deposition onto a liquid polymer, Langmuir, 10.1021/acs.langmuir.9b01112, 35, 25, 8418-8427, 2019.06, We use a green sputtering technique to deposit a Pt/Cu alloy target on liquid polyethylene glycol (PEG) to obtain well-dispersed and stable Pt29Cu71 alloy nanoparticles (NPs). The effects of sputtering current, rotation speed of the stirrer, sputtering time, sputtering period, and temperature of PEG on the particle size are studied systematically. Our key results demonstrate that the aggregation and growth of Pt/Cu alloy NPs occurred at the surface as well as inside the liquid polymer after the particles landed on the liquid surface. According to particle size analysis, a low sputtering current, high rotation speed for the stirrer, short sputtering period, and short sputtering time are found to be favorable for producing small-sized single crystalline alloy NPs. On the other hand, varying the temperature of the liquid PEG does not have any significant impact on the particle size. Thus, our findings shed light on controlling NP growth using the newly developed green sputtering deposition technique..
54. Hiroshi Akiba, Hirokazu Kobayashi, Hiroshi Kitagawa, Kazutaka Ikeda, Toshiya Otomo, Tomokazu Yamamoto, Syo Matsumura, Osamu Yamamuro, Structural and Thermodynamic Studies of Hydrogen Absorption/Desorption Processes on PdPt Nanoparticles, Journal of Physical Chemistry C, 10.1021/acs.jpcc.8b11380, 123, 14, 9471-9478, 2019.04, This work is motivated by an interesting phenomenon discovered by Kobayashi et al., whereby a phase-separated nanoparticle of the Pd-core and Pt-shell is mixed into a solid solution alloy nanoparticle by repeating hydrogen absorption/desorption processes at 373 K. To investigate the structural change, including the positions of hydrogen atoms and the thermodynamic aspect, we measured the neutron diffraction and enthalpy of hydrogen absorption for Pd 0.8Pt0.2 nanoparticles (diameter: 5.0 ± 1.1 nm). Rietveld and atomic pair distribution function (PDF) analyses revealed that D atoms are located at the interstitial octahedral (O) and tetrahedral (T) sites in the solid solution Pd0.8Pt0.2D0.36nanoparticles, while D atoms are not located at the interstitial sites but trapped somewhere, probably at the surface and at the core-shell interface, in core-shell Pd0.8Pt0.2D0.50 nanoparticles. These results are consistent with the model in which hydrogen atoms play a role in creating defects around the interface to lower the activation energy of the mixing process. The enthalpies of H2 and D 2 absorptions in the solid solution Pd0.8Pt0.2 nanoparticles at 298 K and 0.1 MPa are -(20.7 ± 0.1) kJ(H·mol)-1 and -(20.1 ± 0.2) kJ(D·mol)-1, respectively. Both of these values are larger than the corresponding values in Pd nanoparticles, suggesting that the hydrogen absorption sites are stabilized by adding Pt atoms, even though Pt itself does not absorb hydrogen. This unusual and interesting effect is discussed on the basis of the structural and thermodynamic data obtained in this work..
55. Shu-Sheng Liu, Leton C. Saha, @Albert Iskandarov, Takayoshi Ishimoto, Tomokazu Yamamoto, Yoshitaka Umeno, Syo Matsumura, Michihisa Koyama, Atomic structure observations and reaction dynamics simulations on triple phase boundaries in solid-oxide fuel cells, Communications Chemistry, 10.1038/s42004-019-0148-x, 2, 48, 2019.04, The triple phase boundary (TPB) of metal, oxide, and gas phases in the anode of solid oxide fuel cells plays an important role in determining their performance. Here we explore the TPB structures from two aspects: atomic-resolution microscopy observation and reaction dynamics simulation. Experimentally, two distinct structures are found with different contact angles of metal/oxide interfaces, metal surfaces, and pore opening sizes, which have not previously been adopted in simulations. Reaction dynamics simulations are performed using realistic models for the hydrogen oxidation reaction (HOR) at the TPB, based on extensive development of reactive force field parameters. As a result, the activity of different structures towards HOR is clarified, and a higher activity is obtained on the TPB with smaller pore opening size. Three HOR pathways are identified: two types of hydrogen diffusion processes, and one type of oxygen migration process which is a new pathway..
56. Kohei Aso, Koji Shigematsu, Tomokazu Yamamoto, Syo Matsumura, Sequential transmission electron microscopy observation of the shape change of gold nanorods under pulsed laser light irradiation, Microscopy, 10.1093/jmicro/dfy136, 68, 2, 174-180, 2019.03, In situ sequential high-resolution observations were performed on gold nanorods under near-infra-red pulsed laser irradiation using a high-voltage electron microscope attached to a pulsed laser illumination system. The original nanorods were single crystals; the longer axes were oriented along [001]. Under laser light irradiation with λ = 1064 nm with an average intensity per pulse of 980 or 490 J/m2, the shape of the nanorods changed from rod to barrel surrounded by the {111} and {001} facets, while the original single-crystalline structure was maintained. The side surfaces with <110> direction were reconstructed into zig–zag fine structures consisting of narrow {111} facets. The temporal evolution of the volume and surface area during irradiation was evaluated based on the images, assuming that the particles have a rotational symmetry along their longer axes. The surface area was stepwise decreased during the shape change using pulse shots of 980 J/m2 while the volume was maintained. On the other hand, several repeated shots were required to induce the shape change when the averaged intensity was reduced to 490 J/m2 per pulse. In addition to the surface area, the volume was reduced under the latter condition during the shape change due to the evaporation of atoms. The quantitative analysis of the temporal changes indicates the heterogeneity of the atomic excitation or heating of gold nanorods induced by pulsed laser illumination..
57. Xin Fu Tan, Stuart D. McDonald, Qinfen Gu, Yuxiang Hu, Lianzhou Wang, Syo Matsumura, Tetsuro Nishimura, Kazuhiro Nogita, Characterisation of lithium-ion battery anodes fabricated via in-situ Cu6Sn5 growth on a copper current collector, Journal of Power Sources, 10.1016/j.jpowsour.2019.01.034, 50-61, 2019.03, Li-ion batteries (LIBs) are favoured in many applications due to their high energy density and good cyclic performance. However, some safety concerns remain with respect to the risk of fires and explosions with LIBs. Carbon-based anode materials in LIBs operate close to the Li metal reduction potential, therefore Li dendrites can grow during voltage fluctuations, causing short circuits which may lead to fires. The Cu6Sn5 anodes has the lithiation potential at about 0.4 V vs Li/Li+ and therefore less prone to Li metal plating. A new manufacturing method involving direct in-situ formation of Cu6Sn5 on a Cu current collector via melt-solid contact is proposed. This method combines the active material production and the anode fabrication into a single process. Lithiation and delithiation mechanisms of the anode produced are studied by in-situ synchrotron X-ray powder diffraction (XRPD) and ex-situ high voltage transmission electron microscope (HV-TEM). The in-situ XRPD study shows a reversible two-step reaction during cycling, and also reveals the differences in the reaction mechanisms at higher charge/discharge rates than those in published data..
58. Xuan Quy Tran, Min Hong, Hiroshi Maeno, Youichirou Kawami, Takaaki Toriyama, Kevin Jacke, Zhi-Gang Chen, Jin Zou, Syo Matsumur, Matthew S.Dargusch, Real-time observation of the thermally-induced phase transformation in GeTe and its thermal expansion properties, Acta Materialia, 10.1016/j.actamat.2018.11.059, 165, 327-335, 2019.02, The GeTe-based system has long been considered as a promising candidate system for various functional applications; many of which are directly related to the polymorphic phase transformation in their crystalline forms. Consequently, the microstructure underlying their intriguing phase transition has been the subject of numerous studies. Here we provide real-time observation of the microstructural changes associated with the reversible pseudo-cubic (or rhombohedral) to cubic GeTe phase transition using high-voltage transmission electron microscopy (HV-TEM) operating at 1,250 kV and complementary high-temperature X-ray diffraction (XRD). As a result of the phase transition, the pseudo-cubic GeTe domain's configuration significantly changes from its original band-like to a spike-like morphology with a different orientation after a heating/cooling cycle. The coefficients of thermal expansion (CTE) properties as a function of temperature are also explored in relation to the GeTe phase transition.
59. Wenhui Yang, Tomokazu Yamamoto, Kohei Aso, Flora Somidin Kazuhiro Nogita, Syo Matsumura,, Atom locations in a Ni doped η-(Cu,Ni)6Sn5 intermetallic compound, Scripta Materialia, 10.1016/j.scriptamat.2018.08.020, 158, 1, 1-5, 2019.01, The present study has succeeded in direct determination of the location of dopant Ni atoms in η-(Cu,Ni)6Sn5 by aberration-corrected scanning transmission electron microscopy (STEM) including atomic-resolution imaging as well as elemental mapping by X-ray energy-dispersive spectroscopy (XEDS). The three sublattices of Sn, Cu1 and Cu2 were distinguished in atomic-resolution images observed along the [2 -1 -1 0] direction. Atomic-resolution XEDS maps have verified for the first time that the dopant Ni atoms located at the Cu2 sites in η-(Cu,Ni)6Sn5, taking advantage of the Poisson non-local principal component analysis (NLPCA) processing and the lattice-averaging procedure..
60. Ayaka Sato, Shuhei Ogo, Keigo Kamata, Yuna Takeno, Tomohiro Yabe, Tomokazu Yamamoto, Syo Matsumura, Michikazu Hara, Yasushi Sekine, Ambient-temperature oxidative coupling of methane in an electric field by a cerium phosphate nanorod catalyst, Chemical Communications, 10.1039/c9cc00174c, 55, 28, 4019-4022, 2019.01, CePO4 nanorods with uniform surface Ce sites could work as a durable catalyst and showed the highest C2 yield of 18% in an electric field without the need for external heating, which was comparable to that reported for high-performance catalysts at high temperature (>900 K)..
61. Hirokazu Kobayashi, Jared M. Taylor, Yuko Mitsuka, Naoki Ogiwara, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Hiroshi Kitagawa, Charge transfer dependence on CO2 hydrogenation activity to methanol in Cu nanoparticles covered with metal-organic framework systems, Chemical Science, 10.1039/c8sc05441j, 10, 11, 3289-3294, 2019.01, We report the synthesis and characterization of highly active Cu nanoparticles covered with zirconium/hafnium-based metal-organic frameworks for CO2 hydrogenation to methanol. Compared to Cu/γ-Al2O3, Cu/ZIF-8, Cu/MIL-100 and Cu/UiO-66 composites, UiO-66 acts as the most active support, with Cu/Zr-UiO-66 producing methanol at a rate 70 times higher than that of Cu/γ-Al2O3. In addition, the replacement of Zr4+ with Hf4+ in UiO-66 tripled in the rate of methanol production. Furthermore, we describe a substituent effect on the catalytic activity, with Cu/Zr-UiO66-COOH providing a three-fold enhancement of methanol production, compared to that of Zr-UiO-66 or Zr-UiO66-NH2. The enhanced catalytic activity of Cu nanoparticles depends on the charge transfer degree from Cu nanoparticles to UiO-66 at the interface between Cu nanoparticles and UiO-66..
62. Quan Zhang, Kohei Kusada, Dongshuang Wu, Naoki Ogiwara, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Shogo Kawaguchi, Yoshiki Kubota, Tetsuo Honma, Hiroshi Kitagawa, Solid-solution alloy nanoparticles of a combination of immiscible Au and Ru with a large gap of reduction potential and their enhanced oxygen evolution reaction performance, Chemical Science, 10.1039/c9sc00496c, 10, 19, 5133-5137, 2019.01, Au and Ru are elements that are immiscible in the bulk state and have the largest gap in reduction potential among noble metals. Here, for the first time, AuxRu1-x solid-solution alloy nanoparticles (NPs) were successfully synthesized over the whole composition range through a chemical reduction method. Powder X-ray diffraction and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed that Au and Ru atoms are homogeneously mixed at the atomic level. We investigated the catalytic performance of AuxRu1-x NPs for the oxygen evolution reaction, for which Ru is well known to be one of the best monometallic catalysts, and we found that even alloying with a small amount of Au could significantly enhance the catalytic performance..
63. Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Wei Xie, Michihisa Koyama, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa , Emergence of high ORR activity through controlling local density-of-states by alloying immiscible Au and Ir, Chemical Science, 10.1039/C8SC04135K, 2018.12, The electronic structure of surface atoms has a great effect on catalytic activity because the binding energy of reactants is closely related to the electronic structure. Therefore, designing and controlling the local density of states (LDOS) of the catalyst surface would be a rational way to develop innovative catalysts. Herein, we first demonstrate a highly active AuIr solid-solution alloy electrocatalyst for the oxygen reduction reaction (ORR) by emulating the Pt LDOS profile. The calculated LDOS of Ir atoms on the Au0.5Ir0.5(111) surface closely resembled that of Pt(111), resulting in suitable oxygen adsorption energy on the alloy surface for the ORR. We successfully synthesized AuIr solid-solution alloys, while Ir and Au are immiscible even above their melting points in the bulk state. Although monometallic Ir or Au is not active for the ORR, the synthesized Au0.5Ir0.5 alloy demonstrated comparable activity to Pt at 0.9 V versus a reversible hydrogen electrode..
64. Katsutoshi Sato, Ayano Ito, Hiroyuki Tomonaga, Homare Kanematsu, Yuichiro Wada, Hiroyuki Asakura, Saburo Hosokawa, Tsunehiro Tanaka, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka, Pt‐Co alloy nanoparticles on a γ‐Al₂O₃ support: Synergistic effect between isolated electron‐rich Pt and Co for automotive exhaust purification, ChemPlusChem, 10.1002/cplu.201800542, 84, 5, 447-456, 2018.12, There is interest in minimizing or eliminating the use of Pt in catalysts by replacing it with more widely abundant and cost‐effective elements. The alloying of Pt with non‐noble metals is a potential strategy for reducing Pt use because interactions between Pt and non‐noble metals can modify the catalyst structure and electronic properties. Here, we prepared a γ‐Al₂O₃‐supported bimetallic catalyst [Pt(0.1)Co(1)/Al₂O₃], which contained 0.1 wt% Pt and 1 wt% Co and thus featured an extremely low Pt:Co ratio (<1:30 mol/mol). The Pt and Co in this catalyst formed alloy nanoparticles in which isolated electron‐rich Pt atoms were present on the nanoparticle surface. The activity of our Pt(0.1)Co(1)/Al₂O₃ catalyst for purification of automotive exhaust was comparable to the activities of 0.3 and 0.5 wt% Pt/γ‐Al₂O₃ catalysts. Electron‐rich Pt and metallic Co promoted activation of NOx and oxidization of CO and hydrocarbons, respectively. Our strategy of tuning the surrounding structure and electronic state of a noble metal by alloying it with an excess of a non‐noble metal will enable reduced noble metal use in catalysts for exhaust purification and other environmentally important reactions..
65. Bo Huang, Hirokazu Kobayashi, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Yoshihide Nishida, Katsutoshi Sato, Katsutoshi Nagaoka, Masaaki Haneda, Wei Xie, Yusuke Nanba, Michihisa Koyama, Fenglong Wang, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, A CO Adsorption site change induced by copper substitution in a ruthenium catalyst for enhanced CO oxidation activity, Angewandte Chemie International Edition, 10.1002/anie.201812325, 58, 8, 2230-2235, 2018.12, Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance‐improved and cost‐reduced solid‐solution alloy nanoparticles of the Cu‐Ru system for CO oxidation are now presented. Over the whole composition range, all of the CuxRu1−x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations..
66. Naoki Ogiwara, Hirokazu Kobayashi, Keigo Kobayashi, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Hiroshi Kitagawa, Coating of 2D flexible metal–organic frameworks on metal nanocrystals, Chemisty Letters, 10.1246/cl.180931, 2018.12, We report, for the first time, metal (Pd) nanocrystals (NCs) covered with a 2D flexible metal–organic framework (MOF) of [Zn(NO2-ip)(bpy)]n (NO2-ip: 5-nitro-isophthalate, bpy: 4,4′-bipyridine). The hybrid materials were characterized by powder X-ray diffraction measurements and transmission electron microscope techniques. The CO2 sorption and hydrogen storage properties revealed that both the flexible porous character of the MOF and the hydrogen absorption ability of Pd NCs were compatible in the hybrid..
67. Min Hong, Yuan Wang, Tianli Feng, Qiang Sun, Shengduo Xu, Syo Matsumura, Sokrates T. Pantelides, Jin Zou, Zhi-Gang Chen, Strong phonon–phonon interactions securing extraordinary thermoelectric Ge1–xSbxTe with Zn-alloying-induced band alignment, Journal of American Chemical Society, 10.1021/jacs.8b12624, 2018.12, The ability of substitution atoms to decrease thermal conductivity is usually ascribed to the enhanced phonon-impurity scattering by assuming the original phonon dispersion relations. In this study, we find that 10% SbGe alloying in GeTe modifies the phonon dispersions significantly, closes the acoustic–optical phonon band gap, increases the phonon–phonon scattering rates, and reduces the phonon group velocities. These changes, together with grain boundaries, nanoprecipitates, and planar vacancies, lead to a significant decrease in the lattice thermal conductivity. In addition, an extra 2–6% Zn alloying decreases the energy offset between valence band edges at L and Σ points in Ge1–xSbxTe with Zn-alloying-induced band alignment that is found to be induced by the Ge 4s2 lone pairs. Since Zn is free of s2 lone pair electrons, substituting Ge with Zn atoms can consequently diminish the Ge 4s2 lone-pair characters and reduce the energy offset, resulting in two energetically merged valence band maxima. The refined band structures render a power factor up to 40 μW cm–1 K–2 in Ge0.86Sb0.1Zn0.04Te. Ultimately, a superhigh zT of 2.2 is achieved. This study clarifies the impacts of high-concentration substitutional atoms on phonon band structure, phonon–phonon scattering rates, and the convergence of electron valence band edges, which could provide guidelines for developing high-performance thermoelectric materials..
68. Flora Somidin, Hiroshi Maeno, Xuan Quy Tran, Stuart D. McDonald, Mohd Arif Anuar Mohd Salleh, Syo Matsumura, Kazuhiro Nogita, Imaging the polymorphic transformation in a single Cu6Sn5 grain in a solder joint, Materials, 10.3390/ma11112229 , 11, 11, 2229-2238, 2018.11, In-situ observations of the polymorphic transformation in a single targeted Cu6Sn5 grain constrained between Sn-0.7 wt % Cu solder and Cu-Cu3Sn phases and the associated structural evolution during a solid-state thermal cycle were achieved via a high-voltage transmission electron microscope (HV-TEM) technique. Here, we show that the monoclinic η′-Cu6Sn5 superlattice reflections appear in the hexagonal η-Cu6Sn5 diffraction pattern upon cooling to isothermal 140 °C from 210 °C. The in-situ real space imaging shows that the η′-Cu6Sn5 contrast pattern is initiated at the grain boundary. This method demonstrates a new approach for further understanding the polymorphic transformation behavior on a real solder joint..
69. Yuta Ogura, Kotoko Tsujimaru, Katsutoshi Sato, Shin-ichiro Miyahara, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka, Ru/La0.5Pr0.5O1.75 catalyst for low-temperature ammonia synthesis, ACS Sustainable Chemistry & Engineering, 10.1021/acssuschemeng.8b04683, 2018.10, o exploit the use of hydrogen as a source of sustainable energy, development of an efficient process for synthesizing an energy carrier such as ammonia under mild conditions will be necessary. Here, we show that Ru/La0.5Pr0.5O1.75 prereduced at an extraordinary high temperature of 650 °C catalyzes high NH3-synthesis rates under mild conditions. At 400 °C under 1.0 MPa, the synthesis rate was comparable with that of most active oxide-supported Ru catalysts. Kinetic analysis revealed that hydrogen poisoning, which is a typical drawback for oxide-supported Ru catalysts such as Cs+/Ru/MgO, was effectively suppressed over Ru/La0.5Pr0.5O1.75. The high activity induced by high-temperature reduction was attributable to the good thermal stability of the support and a phase change of the La0.5Pr0.5O1.75 support during prereduction. Fourier transform-infrared spectroscopy measurements after N2 adsorption on the catalyst revealed that electrons were efficiently donated from trigonal La0.5Pr0.5O1.5 to the antibonding π orbital of the N≡N bond of N2 via Ru atoms. Cleavage of the N≡N bond, the rate-determining step for ammonia synthesis, was thus accelerated. Our results expand the range of possibilities for developing more effective ammonia synthesis catalysts under mild conditions. Such catalysts will be needed to enable development of hydrogen-based sustainable energy resources..
70. Min Hong, Yuan Wang, Weidi Liu, Syo Matsumura, Har Wang, Jin Zou, Zhi‐Gang Chen,, Arrays of planar vacancies in superior thermoelectric Ge1−x−yCdxBiyTe with band convergence, Advanced Energy Materials, 10.1002/aenm.201801837, 8, 30, 1801837-1-1801837-10, 2018.09, The multivalence bands in GeTe provide an additional handle to manipulate the thermoelectric performance. Herein, the density‐functional‐theory calculation indicates that Cd doping enables the convergence of these multivalence bands. Plus, the additional Bi dopant serving as the electron donors optimizes the carrier concentration, leading to an enhanced power‐factor in Ge1−x−yCdxBiyTe. Moreover, comprehensive electron microscopy characterizations demonstrate the array of high‐density planar vacancies in Ge1−x−yCdxBiyTe stemming from the absence of {111} Ge atomic planes, which is driven by the reduced formation energy in the scenario of Cd/Bi codoping. Simulations of phonon transport confirm the significant role of planar vacancies in scattering mid‐frequency phonons. Such high‐density planar vacancies, in tandem with grain boundaries and point defects, lead to a lattice thermal conductivity of 0.4 W m−1 K−1 in Ge1−x−yCdxBiyTe, reaching the amorphous limit. Ultimately, a peak zT of 2.2 is realized, which promotes GeTe into the first echelon of cutting‐edge thermoelectric materials. The strategy of combining band convergence and planar vacancies opens an avenue to develop Pb‐free derivatives with superhigh thermoelectric efficiency..
71. Min Hong, Zhi‐Gang Chen, Syo Matsumura, Jin Zou, Nano-scale dislocations induced by self-vacancy engineering yielding extraordinary n-type thermoelectric Pb0.96-yInySe, Nano Energy, 10.1016/j.nanoen.2018.06.030, 50, 785-793, 2018.08, Nanostructuring has successfully enhanced thermoelectric performance for wide solid-state materials via embedding nano-scale particles, precipitates, or dislocations into the matrix to significantly lower the thermal conductivity. Herein, high-density dislocations are successfully introduced through engineering the off-stoichiometry ratio of cation atoms in Pb1-xSe. As examined by electron microscopy characterizations and phonon transport modeling studies, the existence of dense nano-scale dislocations in conjunction with grain boundaries and point defects lead to the strong wide-frequency phonon scatterings. Consequently, lattice thermal conductivity is significantly decreased in Pb1-xSe. Through doping In into the Pb0.96Se with an ultralow lattice thermal conductivity, the carrier concentration is tuned to reach the optimal level, which is confirmed by our modeling investigations. The synergistically obtained high-density of dislocations and the optimized carrier concentration lead to an extraordinary figure-of-merit of 1.6 in n-type Pb0.96-yInySe. This study demonstrates a natural way to induce high-density nano-scale dislocations by self-vacancy engineering, which extends the strategy of nanostructuring to broader materials for developing high-performance thermoelectric candidates..
72. Shun Dekura, Hirokazu Kobayashi, Ryuichi Ikeda, Mitsuhiko Maesato, Haruka Yoshino, Masaaki Ohba, Takayoshi Ishimoto, Shogo Kawaguchi, Yoshiki Kubota, Satoru Yoshioka, Syo Matsumura, Takeharu Sugiyama, Hiroshi Kitagawa, The Electronic State of Hydrogen in the α Phase of the Hydrogen‐Storage Material PdH(D)x: Does a Chemical Bond Between Palladium and Hydrogen Exist?, Angewandte Chemie International Edition, 10.1002/anie.201805753, 57, 31, 9823-9827, 2018.06, The palladium–hydrogen system is one of the most famous hydrogen‐storage systems. Although there has been much research on β‐phase PdH(D)x, we comprehensively investigated the nature of the interaction between Pd and H(D) in α‐phase PdH(D)x (x<0.03 at 303 K), and revealed the existence of Pd−H(D) chemical bond for the first time, by various in situ experimental techniques and first‐principles theoretical calculations. The lattice expansion, magnetic susceptibility, and electrical resistivity all provide evidence. In situ solid‐state 1H and 2H NMR spectroscopy and first‐principles theoretical calculations revealed that a Pd−H(D) chemical bond exists in the α phase, but the bonding character of the Pd−H(D) bond in the α phase is quite different from that in the β phase; the nature of the Pd−H(D) bond in the α phase is a localized covalent bond whereas that in the β phase is a metallic bond..
73. Yi‐Chao Zou, Zhi‐Gang Chen, Shijian Liu, Kohei Aso, Chenxi Zhang, Fantai Kong, Min Hong, Syo Matsumura Kyeongjae Cho, Jin Zou, Atomic insights into phase evolution in ternary transition‐metal dichalcogenides nanostructures, Small, 10.1002/smll.201800780, 14, 22, 1800780-1-1800780-6, 2018.05, Phase engineering through chemical modification can significantly alter the properties of transition‐metal dichalcogenides, and allow the design of many novel electronic, photonic, and optoelectronics devices. The atomic‐scale mechanism underlying such phase engineering is still intensively investigated but elusive. Here, advanced electron microscopy, combined with density functional theory calculations, is used to understand the phase evolution (hexagonal 2H→monoclinic T′→orthorhombic Td) in chemical vapor deposition grown Mo1− x W x Te2 nanostructures. Atomic‐resolution imaging and electron diffraction indicate that Mo1− x W x Te2 nanostructures have two phases: the pure monoclinic phase in low W‐concentrated (0 < x ≤ 10 at.%) samples, and the dual phase of the monoclinic and orthorhombic in high W‐concentrated (10 < x < 90 at.%) samples. Such phase coexistence exists with coherent interfaces, mediated by a newly uncovered orthorhombic phase Td′. Td′, preserves the centrosymmetry of T′ and provides the possible phase transition path for T′→Td with low energy state. This work enriches the atomic‐scale understanding of phase evolution and coexistence in multinary compounds, and paves the way for device applications of new transition‐metal dichalcogenides phases and heterostructures..
74. Lin Yu, Katsutoshi Sato, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka, Influence of the crystal structure of titanium oxide on the catalytic activity of Rh/TiO2 in steam reforming of propane at low temperature, Chemistry A European Journal, 10.1002/chem.201800936, 24, 35, 8742-8746, 2018.05, Solid oxide fuel cells (SOFCs) using liquefied petroleum gas(LPG) reduce CO2 emissions due to their high energy‐conversion efficiency. Although SOFCs can convert LPG directly, coking occurs easily by decomposition of hydrocarbons, including C‐C bonds on the electrode of fuel cell stacks. It is therefore necessary to develop an active steam pre‐reforming catalyst that eliminates the hydrocarbons at low temperature, where waste heat of SOFCs is used. Here we show that the crystal structure of the TiO2 that anchors Rh particles is crucial for catalytic activity of Rh/TiO2 catalysts for propane pre‐reforming. Our experimental results revealed that strong metal support interaction (SMSI) induced during H2 pre‐reduction were optimized over Rh/TiO2 with a rutile structure; this catalyst catalyzed the reaction much more effectively than conventional Rh/γ‐Al2O3. In contrast, the SMSI was too strong for Rh/TiO2 with an anatase structure, and the surface of the Rh particles was therefore covered mostly with partially reduced TiO2. The result was very low activity..
75. Takeshi Watanabe, SatoruYoshioka, TomokazuYamamoto, Hossein Sepehri-Amin, Tadakatsu Ohkubo, Syo Matsumura, Yasuaki Einaga, The local structure in heavily boron-doped diamond and the effect this has on its electrochemical properties, Carbon, 10.1016/j.carbon.2018.05.026, 137, 333-342, 2018.05, Transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS), and first principles calculations of EEL spectra were utilized to elucidate the relationship between the microscopic structure and the electrochemical properties of heavily boron-doped diamond (h-BDD). The electro-chemical properties of h-BDD containing 1 at.% and 3 at.% boron are very different. TEM observations showed that 1 at.% h-BDD consists of small densely packed diamond crystallites, while 3 at.% h-BDDcontains small voids and a graphite phase partly along the grain boundaries. The EEL spectrum of the grain interior in 1 at.% h-BDD and comparison of this with a theoretical spectrum shows that the boron atoms are mostly dispersed as single isolated substitutional atoms on diamond lattice sites in the grain interior and that only a small amount of sp2-bonded carbon is present. In contrast, in the grain interior of 3 at.% h-BDD, the boron atoms are mostly associated with nearest neighbor boron pairs, and consequently sp2-bonded carbon is formed. Thus, the local structure has a significant effect on the amount of sp2-bonded carbon. The quite different electrochemical properties of the samples are ascribed to the amount of sp2-bonding arising from the different local structures..
76. K. Sato, H. Yasuda, S. Ichikawa, M. Imamura, K. Takahashi, S. Hata, S. Matsumura, S. Anada, J.-G. Lee, H. Mori, Synthesis of platinum silicide at platinum/silicon oxide interface by photon irradiation, Acta Materialia, 10.1016/j.actamat.2018.05.045, 154, 284-294, 2018.05, The synthesis of platinum silicide at a Pt/SiOx interface by photon irradiation was investigated usingtransmission electron microscopy. A platinum silicide, Pt2Si, was successfully formed at the Pt/SiOx interface by irradiation with 680 and 140 eV photons, but not by irradiation with 80 eV photons. Silicide formation was also induced by irradiation with electrons of energy 75 keV. The amount of silicide formedby photon irradiation was lower than the amount obtained by electron irradiation. Silicide formation by both photon and electron irradiation was accompanied by Si depletion in amorphous SiOx. The experi-mental results indicate that silicide formation is induced by electronic excitation. A possible mechanismfor silicide formation is proposed on the basis of the results..
77. Hirokazu Kobayashi, Miho Yamauchi, Ryuichi Ikeda, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, Double enhancement of hydrogen storage capacity of Pd nanoparticles by 20 at% replacement with Ir; Systematic control of hydrogen storage in Pd-M nanoparticles (M = Ir, Pt, Au), Chemical Science, 10.1039/C8SC01460D, 9, 25, 5536-5540, 2018.05, We report on binary solid-solution nanoparticles (NPs) composed of Pd and Ir, which are not miscible at the equilibrium state of the bulk, for the first time, by means of a process of hydrogen absorption/desorption from core (Pd)/shell (Ir) NPs. Only 20 at% replacement with Ir atoms doubled the hydrogen-storage capability compared to Pd NPs, which are a representative hydrogen-storage material. Furthermore, the systematic control of hydrogen concentrations and the corresponding pressure in Pd and Pd–M NPs (M = Ir, Pt, Au) have been achieved based on the band filling control of Pd NPs..
78. Chen Zhou, Kun Zheng, Ping-Ping Chen, Syo Matsumura Wei Lu, Jin Zou, Crystal-phase control of GaAs-GaAsSb core-shell/axial nanowire heterostructures by a two-step growth, Journal of Materials Chemistry C, 10.1039/C8TC01529E, 6, 25, 6726-6732, 2018.05, The growth of III-Sb nanowires with controlled wurtzite and zinc-blende structures is essential for tailoring their fundamental properties and in turn potential applications. However, most studies of III-Sb nanowires showed that they adopt the zinc-blende structure, so that the growth of wurtzite structured III-Sb nanowires needs to be explored. In this study, both wurtzite and zinc-blende structured GaAs-GaAsSb core-shell nanowire heterostructures as well as axial heterostructures were grown by tuning the crystal structure of nanowire cores and varying the Sb flux. Our aberration-corrected electron microscopy investigations suggest that the nanowire shells maintained the same crystal structure as their nanowire cores. Besides, it was found that the axial-lateral GaAs-GaAaSb heterostructures were grown with increasing the Sb flux, due to the increased Sb supersaturation at the catalyst-nanowire interface. This study provides an avenue for growing III-Sb nanowires with desired crystal structures in order to secure different properties..
79. Flora Somidin, Hiroshi Maeno, M.A.A. Mohd Salleh, Xuan Quy Tran, Stuart D. McDonald, Syo Matsumura, Kazuhiro Nogita, Characterising the polymorphic phase transformation at a localised point on a Cu6Sn5 grain, Materials Characterization, 10.1016/j.matchar.2018.02.006, 138, 113-119, 2018.04, Highlights of this paper are: A single-targeted Cu6Sn5 grain adjacent to Sn-rich sites and Cu3Sn was investigated using HVTEM. Phase transformation from hexagonal to monoclinic in a single-targeted Cu6Sn5 grains. A time-temperature transformation (TTT) diagram was constructed using the HVTEM results..
80. Wenhui Yang, Tomokazu Yamamoto, Kazuhiro Nogita, Syo Matsumura, , STEM analysis of atom location in (Cu, Au, Ni)6Sn5 intermetallic compounds, Solid State Phenomena, 10.4028/, 273, 95-100, 2018.04, Cu6Sn5 is an important intermetallic compound in soldering and electronic packaging. It is formed at the interface between molten solder and substrate during the soldering process, and the evolution of microstructure and properties also occurs in service. Previous studies revealed that Au and Ni are stabilization alloying elements for hexagonal η-Cu6Sn5 intermetallic. For better understanding of stabilization mechanisms at atomic resolution level, in this work, we made an attempt atomic structure analysis on a stoichiometric (Cu, Au, Ni)6Sn5 intermetallic prepared by direct alloying. High-angle annular dark-field (HAADF) imaging and atomic-resolution chemical mapping were taken by the aberration-corrected (Cs-corrected) scanning transmission electron microscopy (STEM). It is found that Au and Ni doped Cu6Sn5 has hexagonal structure. The atom sites of Cu1 and Sn can be distinguished in atomic-resolution images after being observed from orientation [2110], which is also confirmed by atomic-resolution chemical mapping analysis. Importantly, atomic-resolution about distribution of alloying Au atom was directly observed, and Au atoms occupy the Cu1 sites in η-Cu6Sn5..
81. Satoru Yoshioka, Konosuke Tsuruta, Tomokazu Yamamoto, Kazuhiro Yasuda, Syo Matsumura, Norito Ishikawa, E. Kobayashi, X-ray absorption near edge structure and first-principles spectrum investigations of cation disordering in MgAl2O4 induced by swift heavy ions, Physical Chemistry Chemical Physics, 10.1039/c7cp07591j, 20, 4962-4969, 2018.02, Cationic disorder in the MgAl2O4 spinel induced by swift heavy ions was investigated using the X-rayabsorption near edge structure. With changes in the irradiation fluences of 200 MeV Xe ions, the Mg K-edge and Al K-edge spectra were synchronously changed. The calculated spectra based on density function theory indicate that the change in the experimental spectra was due to cationic disorder between Mg in tetrahedral sites and Al in octahedral sites. These results suggest a high inversion degree to an extent that the completely random configuration is achieved in MgAl2O4 induced by the high density electronic excitation under swift heavy ion irradiation..
82. Quan Zhang, Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Shogo Kawaguchi, Yoshiki Kubota & Hiroshi Kitagawa, Selective control of fcc and hcp crystal structures in Au–Ru solid-solution alloy nanoparticles, Nature Communications, 10.1038/s41467-018-02933-6, 9, Article number: 510, 1-9, 2018.02, Binary solid-solution alloys generally adopt one of three principal crystal lattices—body-centred cubic (bcc), hexagonal close-packed (hcp) or face-centred cubic (fcc) structures—in which the structure is dominated by constituent elements and compositions. Therefore, it is a significant challenge to selectively control the crystal structure in alloys with a certain composition. Here, we propose an approach for the selective control of the crystal structure in solid-solution alloys by using a chemical reduction method. By precisely tuning the reduction speed of the metal precursors, we selectively control the crystal structure of alloy nanoparticles, and are able to selectively synthesize fcc and hcp AuRu3 alloy nanoparticles at ambient conditions. This approach enables us to design alloy nanomaterials with the desired crystal structures to create innovative chemical and physical properties..
83. Fenglong Wang,Kohei Kusada,Dongshuang Wu,Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Yusuke Nanba, Michihisa Koyama, Hiroshi Kitagawa, Solid-solution alloy nanoparticles of the immiscible Ir-Cu system with a wide composition range for enhanced electrocatalytic applications, Angewandte Chemie International Edition, 10.1002/anie.201800650, 57, 17, 4505-4509, 2018.02, For the first time, we have synthesized solid-solution alloy nanoparticles between Ir and Cu with a size of ~2 nm, despite Ir and Cu being immiscible in the bulk up to their melting over the whole composition range. We performed a systematic characterization on the nature of the IrxCu1-x solid-solution alloys using powder X-ray diffraction, scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that the obtained IrxCu1-x alloys had a face-centered-cubic structure; charge transfer from Cu to Ir occurred in the alloy nanoparticles, as the core-level Ir 4f peaks shifted to lower energy region with the increase in Cu content. The electron transfer from Cu to Ir observed in the alloy nanoparticles matched the theoretical results well. Furthermore, we observed that the alloying of Ir with Cu enhanced both the electrocatalytic oxygen evolution and oxygen reduction reactions. The enhanced activities could be attributed to the electronic interaction between Ir and Cu arising from the alloying effect at atomic-level..
84. Yuta Ogura, Katsutoshi Sato, Shin-ichiro Miyahara, Yukiko Kawano, Takaaki Toriyama, Tomokazu Yamamoto, Syo Matsumura, Saburo Hosokawa, Katsutoshi Nagaoka, Efficient ammonia synthesis over Ru/La0.5Ce0.5O1.75 pre-reduced at high temperature, Chemical Science, 10.1039/C7SC05343F, 9, 2230-2237, 2018.01, Ammonia is an important feedstock for producing fertiliser and is also a potential energy carrier. However, the process currently used for ammonia synthesis, the Haber–Bosch process, consumes a huge amount of energy; therefore the development of new catalysts for synthesising ammonia at a high rate under mild conditions (low temperature and low pressure) is necessary. Here, we show that Ru/La0.5Ce0.5O1.75 pre-reduced at an unusually high temperature (650 °C) catalysed ammonia synthesis at extremely high rates under mild conditions; specifically, at a reaction temperature of 350 °C, the rates were 13.4, 31.3, and 44.4 mmol g−1 h−1 at 0.1, 1.0, and 3.0 MPa, respectively. Kinetic analysis revealed that this catalyst is free of hydrogen poisoning at the condition. Electron energy loss spectroscopy combined with O2 absorption capacity measurements revealed that the reduced catalyst consisted of fine Ru particles (mean diameter < 2.0 nm) that were partially covered with partially reduced La0.5Ce0.5O1.75 and were dispersed on the thermostable support. Furthermore, Fourier transform infrared spectra measured after N2 addition to the catalyst revealed that N2 adsorption on Ru atoms that interacted directly with the reduced La0.5Ce0.5O1.75 weakened the N≡N bond and thus promoted its cleavage, which is the rate-determining step for ammonia synthesis. Our results indicate that high-temperature pre-reduction of this catalyst consisting of Ru supported on a thermostable composite oxide with the cubic fluorite structure and containing reducible cerium resulted in the formation of many sites that were highly active for N2 reduction by hydrogen..
85. Min Hong, Zhi-Gang Chen, Lei Yang, Zhi-Ming Liao, Yi-Chao Zou, Yan-Hui Chen, Syo Matsumura, Jin Zou, Achieving zT > 2 in p-type AgSbTe2−xSex alloys via exploring the extra light valence band and introducing dense stacking faults, Advanced Energy Materials, 10.1002/aenm.201702333, 8, 9, 1702333, 2017.12, Through simultaneously enhancing the power factor by engineering the extra light band and enhancing phonon scatterings by introducing a high density of stacking faults, a record figure-of-merit over 2.0 is achieved in p-type AgSbTe2−xSex alloys. Density functional theory calculations confirm the presence of the light valence band with large degeneracy in AgSbTe2, and that alloying with Se decreases the energy offset between the light valence band and the valence band maximum. Therefore, a significantly enhanced power factor is realized in p-type AgSbTe2−xSex alloys. In addition, transmission electron microscopy studies indicate the appearance of stacking faults and grain boundaries, which together with grain boundaries and point defects significantly strengthen phonon scatterings, leading to an ultralow thermal conductivity. The synergetic strategy of simultaneously enhancing power factor and strengthening phonon scattering developed in this study opens up a robust pathway to tailor thermoelectric performance..
86. Loku Singgappulige Rosantha Kumara, Osami Sakata, Hirokazu Kobayashi, Chulho Song, Shinji Kohara, Toshiaki Ina, Toshiki Yoshimoto, Satoru Yoshioka, Syo Matsumura, Hiroshi Kitagawa, Hydrogen storage and stability properties of Pd–Pt solid-solution nanoparticles revealed via atomic and electronic structure, Scientific Reports, 10.1038/s41598-017-14494-7, 7, 14606-1-14606-11, 2017.11, Bimetallic Pd1−x Pt x solid-solution nanoparticles (NPs) display charging/discharging of hydrogen gas, which has relevance for fuel cell technologies; however, the constituent elements are immiscible in the bulk phase. We examined these material systems using high-energy synchrotron X-ray diffraction, X-ray absorption fine structure and hard X-ray photoelectron spectroscopy techniques. Recent studies have demonstrated the hydrogen storage properties and catalytic activities of Pd-Pt alloys; however, comprehensive details of their structural and electronic functionality at the atomic scale have yet to be reported. Three-dimensional atomic-scale structure results obtained from the pair distribution function (PDF) and reverse Monte Carlo (RMC) methods suggest the formation of a highly disordered structure with a high cavity-volume-fraction for low-Pt content NPs. The NP conduction band features, as extracted from X-ray absorption near-edge spectra at the Pd and Pt L III -edge, suggest that the Pd conduction band is filled by Pt valence electrons. This behaviour is consistent with observations of the hydrogen storage capacity of these NPs. The broadening of the valence band width and the down-shift of the d-band centre away from the Fermi level upon Pt substitution also provided evidence for enhanced stability of the hydride (ΔH) features of the Pd1−x Pt x solid-solution NPs with a Pt content of 8-21 atomic percent..
87. Yi-Chao Zou, Zhi-Gang Chen, Enze Zhang, Faxian Xiu, Syo Matsumura, Lei Yang, Min Hong, Jin Zou, Superconductivity and Magnetotransport of Single-Crystalline NbSe2 Nanoplates Grown by Chemical Vapour Deposition, Nanoscale, 10.1039/C7NR06617A, 9, 16591-16595, 2017.10, NbSe2 is a typical transition metal dichalcogenide with rich variety of electronic ground states existing in its nanostructures, including two-dimensional superconductivity and charge denisty wave. However, the direct growth of high-quality single-crystalline NbSe2 nanostructures is still challenging, which limits their applications in electronic devices. Here, we report the growth of high-quality NbSe2 nanoplates by a single-step chemical vapour deposition. Their temperature and magnetic-field dependent superconducting behaviors were investigated by four-terminal devices fabricated on individual nanostructures. The NbSe2 nanoplates show two-dimensional characteristics of superconducting transitions and strong anisotropy with magnetic field orientation, providing potential platforms for the exploration of new physics in nanoelectronic devices..
88. Ryusuke Ishikawa, Shuichiro Hirata, Atsushi Tsurumaki-Fukuchi, Masashi Arita, Yasuo Takahashi, Masaki Kudo and Syo Matsumura, In-situ electron microscopy of Cu movement in MoOx/Al2O3 bilayer CBRAM during cyclic switching, ECS Transactions, 10.1149/08010.0903ecst, 80, 10, 903-910, 2017.10, In-situ TEM (transmission electron microscopy) was applied to Cu/MoOx/Al2O3 bilayer CBRAM and the change of the Cu microstructure were observed during cyclic Set/Reset switching. In the Set process giving the low resistance state (LRS), a dark contrast appeared in Al2O3 layer, and in the Reset process giving the high resistance state (HRS), it almost disappeared. This result means that the resistance changed by formation and rupture of the conducting filament. In our MoOx/Al2O3 CBRAMs, cyclic Set/Reset operations were achieved with the real-time TEM observations. During the cycles, device degradation, i.e., gradual decrease in the resistance in the cyclic operation was observed in the both HRS and LRS. We confirmed that the contrast of the Cu layer and the Al2O3 layer had changed while the device degraded..
89. SHIXUE LIU, Shusheng Liu, LETON CHANDRA SAHA, Albert M Iskandarov, Zhenjun Jiao, Shotaro Hara, Takayoshi Ishimoto, Tomofumi Tada, Yoshitaka Umeno, Naoki Shikazono, Syo Matsumura, Michihisa KOYAMA, Multi-Scale, Multi-Physics Approach for Solid Oxide Fuel Cell Anode Reaction, ECS Transactions, 10.1149/07801.2835ecst, 78, 1, 2835-2844, 2017.09, The electrode performance in solid oxide fuel cell depends both on electrode materials and microstructure. Therefore, it is important to breakdown the complexity of multi-physics in the porous electrode into processes in different scales. To clarify the multi-physics toward better electrode design, the use of both the advanced measurement and the simulation techniques is inevitable. For this purpose, we have taken the combined top-down and bottom-up approaches. In this manuscript, we discuss the practical issues in multi-scale, multi-physics simulation, focusing on the local activity of Ni-YSZ anode..
90. Keigo Kobayashi, Hirokazu Kobayashi, Mitsuhiko Maesato, Mikihiro Hayashi, Tomokazu Yamamoto, S. Yoshioka, Syo Matsumura, Takeharu Sugiyama, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Nakanishi, Hiroshi Kitagawa, Discovery of Hexagonal Structured Pd–B Nanocrystals, Angewandte Chemie International Edition, 10.1002/anie.201703209 and 10.1002/ange.201703209, 56, 23, 6578-6582, 2017.06, We report on hexagonal close-packed (hcp) palladium (Pd)–boron (B) nanocrystals (NCs) by heavy B doping into face-centered cubic (fcc) Pd NCs. Scanning transmission electron microscopy–electron energy loss spectroscopy and synchrotron powder X-ray diffraction measurements demonstrated that the B atoms are homogeneously distributed inside the hcp Pd lattice. The large paramagnetic susceptibility of Pd is significantly suppressed in Pd–B NCs in good agreement with the reduction of density of states at Fermi energy suggested by X-ray absorption near-edge structure and theoretical calculations..
91. Yoshihide Nishida, Katsutoshi Sato, Tomokazu Yamamoto, Dongshuang Wu, Kohei Kusada, Hirokazu Kobayashi, Syo Matsumura, Hiroshi Kitagawa, Katsutoshi Nagaoka, Facile synthesis of size-controlled Rh nanoparticles via microwave-assisted alcohol reduction and their catalysis of CO oxidation, Chemistry Letters, 10.1246/cl.170440, 46, 8, 1254-1257, 2017.06, Size-controlled Rh nanoparticles stabilized by polyvinylpyrrolidone were quickly synthesized via alcohol reduction. Microwave-assisted synthesis in closed vessels allowed low to high boiling-point alcohols to be used as reductants under the same preparation conditions. Pure
ethanol has not been used previously because its boiling point is lower than the temperature required for reduction of Rh3+. Alcohols with relatively strong reduction ability were found to lead to smaller Rh nanoparticles. Ability to oxidize CO was enhanced as Rh particle size decreased..
92. Kazuhiro Nogita, X. Q. Tran, T. Yamamoto, E. Tanaka, S.D. McDonald, C. M. Gourlay, Kazuhiro Yasuda, Syo Matsumura, Reply to ‘Comments on “Evidence of the hydrogen release mechanism in bulk MgH2”’, Scientific Reports, 10.1038/srep43720, 7, Article number: 43720, 2017.04, In a comment on our Article “Evidence of the hydrogen release mechanism in bulk MgH2”, Surrey et al. assert that the MgH2 sample we studied was not MgH2 at any time but rather MgO; and that the transformation we observed was the formation of Kirkendall voids due to the outward diffusion of Mg. We address these issues in this reply..
93. Bo Huang, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Nishida Yoshihide, Katsutoshi Sato, Katsutoshi Nagaoka, Shogo Kawaguchi, Yoshiki Kubota, Hiroshi Kitagawa, Solid-Solution Alloying of Immiscible Ru and Cu with Enhanced CO Oxidation Activity, Journal of American Chemical Society, 10.1021/jacs.7b01186, 139, 10, 4643-4646, 2017.03, We report on novel solid-solution alloy nanoparticles (NPs) of Ru and Cu that are completely immiscible even above melting point in bulk phase. Powder X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray measurements demonstrated that Ru and Cu atoms were homogeneously distributed in the alloy NPs. Ru0.5Cu0.5 NPs demonstrated higher CO oxidation activity than fcc-Ru NPs, which are known as one of the best monometallic CO oxidation catalysts..
94. Christoph Rösler, Stefano Dissegna, Victor L. Rechac, Max Kauer, Penghu Guo, Stuart Turner, Kevin Ollegott, Hirokazu Kobayashi, Tomokazu Yamamoto, Daniel Peeters, Yuemin Wang, Syo Matsumura, Gustaaf Van Tendeloo, Hiroshi Kitagawa, Martin Muhler, Francesc X. Llabrés i Xamena, Roland A. Fischer, Encapsulation of Bimetallic Metal Nanoparticles into Robust Zirconium-Based Metal–Organic Frameworks: Evaluation of the Catalytic Potential for Size-Selective Hydrogenation, Chemistry- A European Journal, 10.1002/chem.201603984, 23, 15, 3583-3594, 2017.03, The encapsulation of preformed metal nanoparticles into metal-organic Framework UiO-66(Zr) during solvothermal synthesis represents a challenge due to the harsh acidic reaction conditions. A thin shell of Pt effectively protects the Pd and Ru cores of the bimetallic PdPt and RuPt nanoparticles against etching. In turn, the core modulates the catalytic properties of the Pt shell and allows for enhanced activity in substrate size selective hydrogenation of nitroarenes and low temperature CO oxidation. .
95. Xuan Quy Tran, Stuart D. McDonald, Qinfen Gu, Tomokazu Yamamoto, Koji Shigematsu, Kohei Aso, Eishi Tanaka, Syo Matsumura, Kazuhiro Nogita, In-situ investigation of the hydrogen release mechanism in bulk Mg2NiH4, Journal of Power Sources, 10.1016/j.jpowsour.2016.11.105, 341, 130-138, 2017.02, Hydrogen storage is an important aspect to enable the so-called hydrogen economy. Mg-Ni alloys are among the most promising candidates for solid-state hydrogen storage systems yet many questions remain unanswered regarding the hydriding/dehydriding mechanism of the alloys. Mg2NiH4 particularly has received much attention both for its potential as a hydrogen storage medium and also exhibits interesting properties relating to its different polymorphs. Here, the dehydriding mechanism in bulk Mg2NiH4 is investigated using in-situ ultra-high voltage transmission electron microscopy (TEM) combined with Synchrotron powder X-ray diffraction (XRPD) and differential scanning calorimetry (DSC). We find that the hydrogen release is based on a mechanism of nucleation and growth of Mg2NiHx (x∼0–0.3) solid solution grains and is greatly enhanced in the presence of crystal defects occurring as a result of the polymorphic phase transformation. Also importantly, with atomic resolution TEM imaging a high density of stacking faults is identified in the dehydrided Mg2NiHx (x∼0–0.3) lattices..
96. Tokutaro Komatsu, Hirokazu Kobayashi, Kohei Kusada, Yoshiki Kubota, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Sato, Katsutoshi Nagaoka, Hiroshi Kitagawa, First-principles calculation, synthesis, and catalytic properties of Rh-Cu alloy nanoparticles, Chemistry - A European Journal, 10.1002/chem.201604286, 23, 1, 57-60, 2017.01, The first synthesis of pure Rh1−xCux solid-solution nanoparticles is reported. In contrast to the bulk state, the solid-solution phase was stable up to 750 °C. Based on facile density-functional calculations, we made a prediction that the catalytic activity of Rh1−xCux can be maintained even with 50 at % replacement of Rh with Cu. The prediction was confirmed for the catalytic activities on CO and NOx conversions..
97. Mo-Rigen He, Shuai Wang, Ke Jin, Hongbin Bei, Kazuhiro Yasuda, Syo Matsumura, Kenji Higashida, Ian M. Robertson, Enhanced damage resistance and novel defect structure of CrFeCoNi under in situ electron irradiation, Scripta Materialia, 10.1016/j.scriptamat.2016.07.023, 125, 5-9, 2016.12, Defect production and growth in CrFeCoNi, a single-phase concentrated solid solution alloy, is characterized using in situ electron irradiation inside a transmission electron microscope operated at 400–1250 kV and 400 °C. All observed defects are interstitial-type, either elliptical Frank loops or polygonal (mostly rhombus) perfect loops. Both forms of loops in CrFeCoNi exhibit a sublinear power law of growth that is > 40 times slower than the linear defect growth in pure Ni. This result shows how compositional complexity impacts the production of Frenkel pairs and the agglomeration of interstitials into loops, and, thus, enhances the radiation tolerance..
98. Mo-Rigen He, Shuai Wang, Shi Shi, Ke Jin, Hongbin Bei, Kazuhiro Yasuda, Syo Matsumura, Kenji Higashida, Ian M. Robertson, Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys , Acta Materialia, 10.1016/j.actamat.2016.12.046, 126, 182-193, 2016.12, Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized, high-entropy configurations against radiation damage. Here we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elements are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L10 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. These findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition..
99. Kazuhiro Nogita, M. A. A. Mohd Salleh, Guang Zeng, Stuart D. McDonald, Syo Matsumura, In-situ TEM observations of Cu6Sn5 polymorphic transformations in reaction layers between Sn-0.7Cu solders and Cu substrates, JOM, 10.1007/s11837-016-2020-0, 68, 11, 2871-2878, 2016.11.
100. Kohei Aso, Koji Shigematsu, Tomokazu Yamamoto, Syo Matsumura, Detection of picometer-order atomic displacements in drift-compensated HAADF-STEM images of gold nanorods, Microscopy, 10.1093/jmicro/dfw018, 65, 5, 391-399, 2016.09.
101. Katsutoshi Sato, Kazuya Imamura, Yukiko Kawano, Shin-ichiro Miyahara, Tomokazu Yamamoto, Syo Matsumura, Katsutoshi Nagaoka, A low-crystalline ruthenium nano-layer supported on praseodymium oxide as an active catalyst for ammonia synthesis, Chemical Science, 10.1039/C6SC02382G, 8, 1, 674-679, 2016.09, Ammonia is a crucial chemical feedstock for fertilizer production and is a potential energy carrier. However, the current method of synthesizing ammonia, the Haber–Bosch process, consumes a great deal of energy. To reduce energy consumption, a process and a substance that can catalyze ammonia synthesis under mild conditions (low temperature and low pressure) are strongly needed. Here we show that Ru/Pr2O3 without any dopant catalyzes ammonia synthesis under mild conditions at 1.8 times the rates reported with other highly active catalysts. Scanning transmission electron micrograph observations and energy dispersive X-ray analyses revealed the formation of low-crystalline nano-layers of ruthenium on the surface of Pr2O3. Furthermore, CO2 temperature-programmed desorption revealed that the catalyst was strongly basic. These unique structural and electronic characteristics are considered to synergistically accelerate the rate-determining step of NH3 synthesis, cleavage of the N[triple bond, length as m-dash]N bond. We expect that the use of this catalyst will be a starting point for achieving efficient ammonia synthesis..
102. S. Takaki, Kazuhiro Yasuda, Tomokazu Yamamoto, Syo Matsumura, Norito Ishikawa, Structure of ion tracks in ceria irradiated with high energy xenon ions, Progress in Nuclear Energy, 10.1016/j.pnucene.2016.07.013, 92, 306312-312, 2016.09, Structure and accumulation behavior of ion tracks in CeO2 irradiated with 200 MeV Xe ions were examined by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) to obtain fundamental knowledge on the microstructure evolution induced by fission fragments in nuclear fuels and transmutation targets, which is of importance for the development of advanced fuel/target materials at high burn-up conditions. Bright-field (BF) TEM images of ion tracks from an inclined direction showed Fresnel contrast along penetrating path of incident ions. The signal intensity of high-angle annular dark-field (HAADF) STEM images was decreased at the core damage region of ion tracks along the path of ions, revealing the reduction of atomic density inside the ion track. Preferential formation of smaller and larger ion tracks was observed at a high ion fluence of 1 × 1014 cm−2 compared to a low ion fluence of 1 × 1011 cm−2. Results were discussed due to the coalescences and incomplete recovery of the core damage regions during the overlap of high density electronic excitation damage, which is induced during the repetition of the formation and recovery of ion tracks within an influence region..
103. Kazuhisa Sato, Shunya Tashiro, Yohei Yamaguchi, Takanori Kiguchi, Toyohiko J. Konno, Tomokazu Yamamoto, Kazuhiro Yasuda, Syo Matsumura, Three-Dimensional Imaging of a Long-Period Stacking Ordered Phase in Mg97Zn1Gd2 Using High-Voltage Electron Microscopy, Materials Transactions, 10.2320/matertrans.M2016021], 57, 6, 918-921, 2016.06.
104. Katsutoshi Sato, Hiroyuki Tomonaga, Tomokazu Yamamoto, Syo Matsumura, Nor Diana Binti Zulkifli, Takayoshi Ishimoto, Michihisa KOYAMA, Kohei Kusada, Hirokazu Kobayashi, Hiroshi Kitagawa, Katsutoshi Nagaoka, A synthetic pseudo-Rh: NOx reduction activity and electronic structure of Pd–Ru solid-solution alloy nanoparticles, Scientific Reports, 10.1038/srep28265, 6, article number 28265, 2016.06.
105. Xuan Quy Tran, Stuart D. McDonald, Qinfen Gu, Syo Matsumura, Kazuhiro Nogita, Effect of trace Na additions on the hydrogen absorption kinetics of Mg2Ni, Journal of Materials Research, 10.1557/jmr.2016.123 , 31, 9, 1316-1327, 2016.05, It is demonstrated that Na doping can significantly improve the hydriding performance of Mg2Ni under an isobaric-isothermal condition of 2 MPa H2 and 350 °C. .
106. LIU SHUSHENG, Akiko Takayama, Syo Matsumura, Michihisa KOYAMA, Image contrast enhancement of Ni/YSZ anode during the slice-and-view process in FIB-SEM, Journal of Microscopy, 10.1111/jmi.12355, 261, 3, 326-332, 2016.03, Focused ion beam-scanning electron microscopy (FIB-SEM) is a widely used and easily operational equipment for three-dimensional reconstruction with flexible analysis volume. It has been using successfully and increasingly in the field of solid oxide fuel cell. However, the phase contrast of the SEM images is indistinct in many cases, which will bring difficulties to the image processing. Herein, the phase contrast of a conventional Ni/yttria stabilized zirconia anode is tuned in an FIB-SEM with In-Lens secondary electron (SE) and backscattered electron detectors. Two accessories, tungsten probe and carbon nozzle, are inserted during the observation. The former has no influence on the contrast. When the carbon nozzle is inserted, best and distinct contrast can be obtained by In-Lens SE detector. This method is novel for contrast enhancement. Phase segmentation of the image can be automatically performed. The related mechanism for different images is discussed..
107. Sunao Sadamatsu, Masaki Tanaka, Kenji Higashida, Syo Matsumura, Transmission electron microscopy of bulk specimens over 10µm in thickness, Ultramicroscopy, 10.1016/j.ultramic.2015.09.001, 162, 10-16, 2015.12, [URL], We succeeded the observation of microstructures in bulk-sized specimens of over 10µm in thickness by employing a technique that combines transmission electron microscopy (TEM) with energy-filtered imaging based on electron energy-loss spectroscopy (EELS). This method is unique in that it incorporates the inelastically scattered electrons into the imaging process. Using this technique, bright and sharp images of dislocations in crystalline silicon specimens as thick as 10µm were obtained. A calibration curve to determine foil thickness of such a thick specimen was also derived. This method simply extends the observable thickness range in TEM. If combined with tilt series of observation over a significant range of angle, it will disclose three dimensional nanostructures in a µm-order block of a specimen, promoting our understanding of the controlling mechanisms behind various bulky material properties..
108. Ryuichiro Oguma, Syo Matsumura, Kinetics of ordered domain formation in binary alloys of D019 type order, Transactions of the Materials Research Society of Japan, 10.14723/tmrsj.40.325, 40, 4, 325-329, 2015.12, The present authors have developed a Time-dependent Ginzburg-Landau (TDGL) model for microstructural evolution of D019 type ordering, taking into account the crystal symmetry of the ordered phase. The D019 structure based on hcp is divided into four equivalent sublattices. The site occupation probabilities are given as a function of three order parameters and a composition parameter. Multiple types of variants of the structures are represented by the order parameters. Mean-field free energies are defined in a form of Landau type expansion with the order parameters and the composition parameter. Interfacial energies due to local variations of degrees of order and composition are given in a gradient square approximation. Kinetic equations for time-evolution of the order parameters and the composition one are derived from the Ginzburg-Landau type potential consisting of the mean-field free energies and the interfacial energy terms. We distinguish characteristic off-phase boundaries observed in Transmission Electron Microscopy (TEM) images in such as Cu3Sn and Ti3Al, and performed three-dimensional numerical simulations based on the kinetic equations..
109. Md. Shahajahan Kutubi, Katsutoshi Sato, Kenji Wada, Tomokazu Yamamoto, Syo Matsumura, Kohei Kusada, Hirokazu Kobayashi, Hiroshi Kitagawa, Katsutoshi Nagaoka, Dual Lewis Acidic/Basic Pd0.5Ru0.5–Poly(N-vinyl-2-pyrrolidone) Alloyed Nanoparticle: Outstanding Catalytic Activity and Selectivity in Suzuki–Miyaura Cross-Coupling Reaction, ChemCatChem, 10.1002/cctc.201500758, 7, 23, 3887-3894, 2015.12.
110. Yusuke Shimada, Satoshi Hata, Ken-ichi Ikeda, Hideharu Nakashima, Syo Matsumura, Hiroya Tanaka, Akiyasu Yamamoto, Jun-ichi Shimoyama, Kohji Kishio, Microstructural connectivity in sintered ex-situ MgB2 bulk superconductors, Journal of Alloys and Compounds, 10.1016/j.jallcom.2015.09.253, 656, 172-180, 2015.10, [URL], We have performed combined high-resolution microstructural and grain orientation analyses to understand the key microstructural factors associated with high intergranular transport current in polycrystalline bulk forms of MgB2. The ex-situ method can produce MgB2 with relatively high packing factors; nevertheless, the connectivity of MgB2 fabricated by the ex-situ method (ex-situ MgB2) was less than that of in-situ MgB2. The poor connections between MgB2 grain aggregates cause the low connectivity of ex-situ MgB2. Plate-like pores are present between the aggregates of MgB2 grains in ex-situ MgB2; these pores remain even after prolonged self-sintering at high temperatures. In addition, MgB2 crystals decompose to MgB4 in sintering for a long period. Moreover, MgO particles are formed between MgB2 grain aggregates and inhibit interaggregate connections. In contrast, in-situ MgB2 fabricated at the same sintering conditions exhibits spherical pores between MgB2 grains, resulting in a uniform pore distribution and intergranular connection. These problems must be addressed to further enhance the connectivity in ex-situ MgB2..
111. Guang Zeng, Stuart D. McDonald, Qinfen Gu, Syo Matsumura, Kazuhiro Nogita, Kinetics of the β → α transformation of tin: Role of α-tin nucleation, Crystal Growth Design, 10.1021/acs.cgd.5b01069, 15, 12, 5767-5773, 2015.10, The influence of α-Sn nucleation on the kinetics of the β → α phase transformation are investigated, using in situ synchrotron powder X-ray diffraction (PXRD) with variable temperature control. In the entire thermal history of the α → β → α ... The role of α-Sn nucleation on the kinetics of the β → α phase transformation is studied using synchrotron powder X-ray diffraction. The degree of α-Sn nucleation has a strong influence on the kinetics of the β → α transformation. The growth component n is a function of both transformation time (fraction) and temperature. By introducing an impingement factor c = 2, the transformation curves yield good fits to the modified Johnson−Mehl−Avrami−Kolmogorov model..
112. Masaaki Sadakiyo, Minako Heima, Tomokazu Yamamoto, Syo Matsumura, Masashi Matsuura, Satoshi Sugimoto, Kenichi Kato, Masaki Takata, Miho Yamauchi, Preparation of solid–solution type Fe–Co nanoalloys by synchronous deposition of Fe and Co using dual arc plasma guns, Dalton Transactions, 10.1039/C5DT02815A, 44, 36, 15764-15768, 2015.09, We succeeded in the efficient preparation of well-dispersed Fe–Co nanoalloys (NAs) using the arc plasma deposition method. Synchronous shots of dual arc plasma guns were applied to a carbon support to prepare the solid–solution type Fe–Co NAs having an approximately 1 : 1 atomic ratio. The alloy structures with and without a reductive thermal treatment under a hydrogen atmosphere were examined using X-ray powder diffraction, scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray analysis, high resolution STEM, and magnetic measurements, suggesting that highly crystalline spherical particles of ordered B2-type Fe–Co NAs form by the thermal treatment of the deposited grains..
113. Megumi Mukoyoshi, Hirokazu Kobayashi, Kohei Kusada, Mikihiro Hayashi, Teppei Yamada, Mitsuhiko Maesato, Jared M. Taylor, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, Hybrid materials of Ni NP@MOF prepared by a simple synthetic method, Chemical Communications, 10.1039/C5CC04663G, 51, 62, 12463-12466, 2015.07, We demonstrate a novel, simple synthetic method for metal (Ni) NPs in a MOF using the partial thermal decomposition of nickel(II) 2,5-dihydroxyterephthalate (Ni-MOF-74). The Ni NPs inside the Ni-MOF-74 are several nanometers in size, and the size can be precisely controlled by the heating conditions..
114. LIU SHUSHENG, Syo Matsumura, Michihisa KOYAMA, Boundary observation and contrast tuning of Ni/YSZ anode by TEM and FIB-SEM, ECS Transactions, 10.1149/06801.1275ecst, 68, 1, 1275-1279, 2015.07, Ni/yttria stabilized zirconia (Ni/YSZ) anode was investigated in the aspect of microstructure. Atomic resolution transmission electron microscopy and high resolution focused ion beam-scanning electron microscopy (FIB-SEM) were used to study the atomic structure of boundaries and phase contrast, respectively. Images of Ni/YSZ interface and Ni/YSZ/pore triple-phase boundary were obtained. High-Index contact surfaces were found. Distinct phase contrast among Ni, YSZ and resin was observed during the slice and view process in FIB-SEM..
115. Shu-Sheng Liu, Zhenjun Jiao, Naoki Shikazono, Syo Matsumura, Michihisa KOYAMA, Observation of the Ni/YSZ interface in a conventional SOFC, Journal of the Electrochemical Society, 10.1149/2.0591507jes, 162, 7, F750-F754, 2015.07, As a conventional anode for solid oxide fuel cell, Ni/YSZ has been deeply investigated in many aspects. However, little is known on the atomic structure of the Ni/YSZ interface, which is quite important for the reaction activity and stability. Herein, a conventional cell was prepared by mixing/sintering/reduction process. The crystallographic orientation relationships and contact surfaces between Ni and YSZ were investigated by transmission electron microscopy (TEM), and scanning TEM. The TEM specimens were prepared by focused ion beam-scanning electron microscopy. It was found that the Ni/YSZ orientation relationships are much more complicated than those samples prepared by directionally solidified eutectics and deposition methods. Higher-index and step contact surfaces were observed or estimated, such as Ni(15 13 1)/YSZ(4 4 10). This interface structure was analyzed with the help of atomistic models. The misfits were found to be small in both x and y directions. Further geometric analysis by near coincidence site lattice theory indicates that this interface is relatively stable. It is supposed that various Ni/YSZ interfaces exist in a conventional cell and stay in different energy states. The unstable and metastable interfaces should be considered when we discuss the long term stability of cell during the operation..
116. Yusuke Shimada, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Syo Matsumura, Hiroya Tanaka, Akiyasu Yamamoto, Jun-ichi Shimoyama, Kohji Kishio, Microstructural characteristics of ball-milled self-sintered ex situ MgB2 bulks, IEEE Transactions on Applied Superconductivity, 10.1109/TASC.2014.2379928, 25, 3, 6801105-1-6801105-5, 2015.06, [URL], The ex situ method yields MgB2 samples with high packing factor. However, the critical current density of MgB2 bulks and wires fabricated using the ex situ method (ex situ MgB2) requires improvement for practical use because of insufficient connectivity. In this study, we evaluated the microstructure of self-sintered ex situ MgB2 bulks fabricated from laboratory-made ball-milled powder. We observed that green compacts of the ball-milled bulks contain fine MgB2 grain aggregates and a decreased gap length between MgB2 grain aggregates compared with those prepared without ball-milling. Therefore, the number of connections between the MgB2 grain aggregates and current path increased. However, the width of the connections between MgB2 grain aggregates remained narrow, suggesting the importance of controlling the initial microstructure of green compacts, such as the size of MgB2 grain aggregates and packing factor, by optimizing milling and pressing conditions..
117. Takeshi Matsumoto, Masaaki Sadakiyo, Mei Lee Ooi, Tomokazu Yamamoto, Syo Matsumura, Kenichi Kato, Tatsuya Takeguchi, Nobuki Ozawa, Momoji Kubo, Miho Yamauchi, Atomically mixed Fe-group nanoalloys: catalyst design for the selective electrooxidation of ethylene glycol to oxalic acid, Physical Chemistry Chemical Physics, 10.1039/C5CP00954E, 17, 17, 11359-11366, 2015.03, We demonstrate electric power generation via the electrooxidation of ethylene glycol (EG) on a series of Fe group nanoalloy (NA) catalysts in alkaline media. A series of Fe-group binary NA catalysts supported on carbon (FeCo/C, FeNi/C, and CoNi/C) and monometallic analogues (Fe/C, Co/C, and Ni/C) were synthesized. Catalytic activities and product distributions on the prepared Fe-group NA catalysts in the EG electrooxidation were investigated by cyclic voltammetry and chronoamperometry, and compared with those of the previously reported FeCoNi/C, which clarified the contributory factors of the metal components for the EG electrooxidation activity, C2 product selectivity, and catalyst durability. The Co-containing catalysts, such as Co/C, FeCo/C, and FeCoNi/C, exhibit relatively high catalytic activities for EG electrooxidation, whereas the catalytic performances of Ni-containing catalysts are relatively low. However, we found that the inclusion of Ni is a requisite for the prevention of rapid degradation due to surface modification of the catalyst. Notably, FeCoNi/C shows the highest selectivity for oxalic acid production without CO2 generation at 0.4 V vs. the reversible hydrogen electrode (RHE), resulting from the synergetic contribution of all of the component elements. Finally, we performed power generation using the direct EG alkaline fuel cell in the presence of the Fe-group catalysts. The power density obtained on each catalyst directly reflected the catalytic performances elucidated in the electrochemical experiments for the corresponding catalyst. The catalytic roles and alloying effects disclosed herein provide information on the design of highly efficient electrocatalysts containing Fe-group metals..
118. Kazuhiro Nogita, X. Q. Tran, T. Yamamoto, E. Tanaka, S.D. McDonald, C. M. Gourlay, kazuhiro Yasuda, Syo Matsumura, Evidence of the hydrogen release mechanism in bulk MgH2, Scientific Reports, 10.1038/srep08450, 5, Article number: 8450, 2015.02, Here we use in situ ultra-high voltage transmission electron microscopy (TEM) to directly verify the mechanisms of the hydride decomposition of bulk MgH2 in Mg-Ni alloys. We find that the hydrogen release mechanism from bulk (2 μm) MgH2 particles is based on the growth of multiple pre-existing Mg crystallites within the MgH2 matrix, present due to the difficulty of fully transforming all Mg during a hydrogenation cycle whereas, in thin samples analogous to nano-powders, dehydriding occurs by a ‘shrinking core’ mechanism..
119. Guangqin Li, Hirokazu Kobayashi, Kohei Kusada, Jared M. Taylor, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, An ordered bcc CuPd nanoalloy synthesised via the thermal decomposition of Pd nanoparticles covered with a metal-organic framework under hydrogen gas, Chemical Communications, 10.1039/C4CC05941G, 50, 89, 13750-13753, 2014.11, Presented here is the synthesis of an ordered bcc copper-palladium nanoalloy, via the decomposition of a Pd nanoparticle@metal-organic framework composite material. In situ XRD measurements were performed in order to understand the mechanism of the decomposition process. This result gives a further perspective into the synthesis of new nanomaterials via metal-organic framework decomposition..
120. Christoph Rösler, Daniel Esken, Christian Wiktor, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, Roland A. Fischer, Encapsulation of bimetallic nanoparticles into a metal–organic framework: Preparation and microstructure characterization of Pd/Au@ZIF-8, European Journal of Inorganic Chemistry, 10.1002/ejic.201402409, 2014, 32, 5514-5521, 2014.11, The zinc-imidazolate-based framework ZIF-8 was loaded with preformed surfactant-stabilized bimetallic Pd/Au nanoparticles and its corresponding monometallic counterparts Au and Pd by a controlled encapsulation process during the ZIF-8 crystal growth. The nanoparticle-loaded materials were characterized by powder X-ray diffraction (PXRD), FTIR spectroscopy, N2-sorption measurements, as well as by transmission electron microscopy (TEM). The ZIF-8 matrix material remained intact and the NP@ZIF-8 materials revealed the permanent porosity of Brunauer–Emmett–Teller (BET) surface areas above 1100 m2 g–1. The nanoparticles are exclusively found inside the volume of the nanocrystals and exhibit unchanged composition and size distribution as revealed by TEM investigations. Additionally, scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) confirmed the solid solution-type alloying of Pd and Au in the embedded Pd/Au nanoparticles. The materials were briefly evaluated in aqueous-phase aerobic alcohol oxidation to investigate the synergetic effects of alloyed Pd/Au nanoparticles and the microporous, hydrophobic matrix ZIF-8..
121. Takeshi Matsumoto, Masaaki Sadakiyo, Mei Lee Ooi, Sho Kitano, Tomokazu Yamamoto, Syo Matsumura, Kenichi Kato, Tatsuya Takeguchi, Miho Yamauchi, CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media, Scientific Reports, 10.1038/srep05620, 2014.07, An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system..
122. Guangqin Li, Hirokazu Kobayashi, Jared M. Taylor, Ryuichi Ikeda, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Shoichi Toh, Syo Matsumura, Hiroshi Kitagawa, ​Hydrogen storage in ​Pd nanocrystals covered with a metal–organic framework, Nature Materials, 10.1038/nmat4030, 13, 802-806, 2014.07, Here, we present remarkably enhanced capacity and speed of ​hydrogen storage in ​Pd nanocrystals covered with the metal–organic framework (MOF) ​HKUST-1 (​copper(II) 1,3,5-benzenetricarboxylate). The ​Pd nanocrystals covered with the MOF have twice the storage capacity of the bare ​Pd nanocrystals. The significantly enhanced ​hydrogen storage capacity was confirmed by ​hydrogen pressure–composition isotherms and solid-state deuterium nuclear magnetic resonance measurements. The speed of ​hydrogen absorption in the ​Pd nanocrystals is also enhanced by the MOF coating..
123. Guangqin Li, Hirokazu Kobayashi, Shun Dekura, Ryuichi Ikeda, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura, Hiroshi Kitagawa, Shape-Dependent Hydrogen-Storage Properties in Pd Nanocrystals: Which Does Hydrogen Prefer, Octahedron (111) or Cube (100)?, Journal of the American Chemical Society, 10.1021/ja504699u, 136, 29, 10222-10225, 2014.07, Hydrogen-storage properties of Pd octahedrons and cubes enclosed by {111} and {100} facets were investigated using in situ powder X-ray diffraction, in situ solid-state 2H NMR and hydrogen pressure–composition isotherm measurements. With these measurements, it was found that the exposed facets do not affect hydrogen-storage capacity; however, they significantly affect the absorption speed, with octahedral nanocrystals showing the faster response. The heat of adsorption of hydrogen and the hydrogen diffusion pathway were suggested to be dominant factors for hydrogen-absorption speed. Furthermore, in situ solid-state 2H NMR detected for the first time the state of 2H in a solid-solution (Pd + H) phase of Pd nanocrystals at rt..
124. S. Takaki, kazuhiro Yasuda, Tomokazu Yamamoto, Syo Matsumura, Norito Ishikawa, Atomic structure of ion tracks in Ceria, Nuclear Instruments and Methods in Physics Research B, 10.1016/j.nimb.2013.10.077, 326, 140-144, 2014.05, We have investigated atomic structure of ion tracks in CeO2 irradiated with 200 MeV Xe ions by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). TEM observations under inclined conditions showed continuous ion tracks with diffraction and structure factor contrast, and the decrease in the atomic density of the ion tracks was evaluated to be about 10%. High resolution STEM with high-angle annular dark-field (HAADF) technique showed that the crystal structure of the Ce cation column is retained at the core region of ion tracks, although the signal intensity of the Ce cation lattice is reduced over a region 4–5 nm in size. Annular bright field (ABF) STEM observation has detected that the O anion column is preferentially distorted at the core region of ion tracks within a diameter of 4 nm. The core region of ion track in CeO2 is determined to contain a high concentration of vacancies or small vacancy clusters and to generate interstitials in surrounding regions..
125. LIU SHUSHENG, Michihisa KOYAMA, Shoichi Toh, Syo Matsumura, Microstructure evolution of NiO–YSZ cermet during sintering, Solid State Ionics, 10.1016/j.ssi.2014.04.007, 262, 460-464, 2014.05, Sintering is one of the most important steps in the fabrication of solid oxide fuel cell anode. The microstructure evolution of practical NiO − YSZ cermets during sintering was investigated by a scanning electron microscopy. Energy selective backscatter and angle selective backscatter images could provide distinct contrast between NiO and YSZ while the later also shows morphology. Particle size distributions and grain growth activation energies were evaluated. The sintering is negligible below 700 °C while it becomes notorious from 1100 °C. NiO coarsens prior to YSZ, but nearly stops growth when the temperature maintains at 1400 °C for 3 h..
126. Nao Sumimoto, Koichiro Nakao, Tomokazu Yamamoto, Syo Matsumura, kazuhiro Yasuda, Yasuro Niidome, In situ observation of structural transformation of gold nanorods under pulsed laser irradiation in an HVEM , Microscopy, 10.1093/jmicro/dfu012, 63, 4, 261-268, 2014.04, A pulsed laser light illumination system was attached to a high-voltage electron microscope (HVEM) for in situ observation of light-induced behaviors of nano objects. The wavelength λ of emitted laser pulses was 1064, 532 or 266 nm, and the pulse duration was 6–8 ns. Using this combined HVEM system, we observed the deformation behavior of gold nanorods irradiated by a pulsed laser (λ = 1064 nm) at an intensity of 310 J m−2 pulse or higher. A single shot of pulsed laser reduced the aspect ratio of the gold nanorods from 5 to a much smaller value. The extent of the reduction increased at higher laser intensities. However, at 310 J m−2 pulse−1, additional pulsed shots induced limited further deformation. The mean aspect ratio approximated to 2.5 even after irradiation with 7 pulses (total fluence exceeding 2 MJ m−2). In situ high resolution transmission electron microscopy (HRTEM) observation revealed that deformation was accompanied by total atomic restructuring of the nanorod interiors..
127. Kohei Kusada, Hirokazu Kobayashi, Ryuichi Ikeda, Yoshiki Kubota, Masaki Takata, Shoichi Toh, Tomokazu Yamamoto, Syo Matsumura, Naoya, Sumi, Katsutoshi Sato, Katsutoshi Nagaoka, Yoshiki Kubota, Hiroshi Kitagawa, Solid Solution Alloy Nanoparticles of Immiscible Pd and Ru Elements Neighboring on Rh: Changeover of the Thermodynamic Behavior for Hydrogen Storage and Enhanced CO-Oxidizing Ability, Journal of the American Chemical Society, 10.1021/ja409464g, 136, 5, 1864-1871, 2014.01, PdxRu1–x solid solution alloy nanoparticles were successfully synthesized over the whole composition range through a chemical reduction method, although Ru and Pd are immiscible at the atomic level in the bulk state. From the XRD measurement, it was found that the dominant structure of PdxRu1–x changes from fcc to hcp with increasing Ru content. The structures of PdxRu1–x nanoparticles in the Pd composition range of 30–70% consisted of both solid solution fcc and hcp structures, and both phases coexist in a single particle. In addition, the reaction of hydrogen with the PdxRu1–x nanoparticles changed from exothermic to endothermic as the Ru content increased. Furthermore, the prepared PdxRu1–x nanoparticles demonstrated enhanced CO-oxidizing catalytic activity; Pd0.5Ru0.5 nanoparticles exhibit the highest catalytic activity. This activity is much higher than that of the practically used CO-oxidizing catalyst Ru and that of the neighboring Rh, between Ru and Pd..
128. kazuhiro Yasuda, M. Etoh, K. Sawada, Tomokazu Yamamoto, Kazufumi Yasunaga, Syo Matsumura, Norito Ishikawa, Defect formation and accumulation in CeO2 irradiated with swift heavy ions, Nuclear Instruments and Methods in Physics Research B, 10.1016/j.nimb.2013.04.069, 314, 185-190, 2013.11, We have investigated microstructure evolution in CeO2 irradiated with 210 MeV Xe ions by using transmission electron microscopy to gain the fundamental knowledge on radiation damage induced by fission fragments in nuclear fuel and transmutation target. Analysis on the accumulation of ion tracks has revealed an influence region to recover pre-existing core damage regions of ion tracks to be 8.4 nm in radius. Cross section observations showed that high-density electronic excitation induces both ion tracks and dislocation loops. At high fluences of 1.5 × 1019 and 1 × 1020 ions m−2, depth-dependent microstructure was developed with radiation-induced defects of ion tracks, dislocation loops (dot-contrast) and line dislocations. Formation of sub-divided small grains was found at shallow depth at a fluence of 1 × 1020 ions m−2. The microstructure evolution was discussed in terms of the accumulation of interstitials due to significant overlap of high density electronic excitation..
129. M. Timpel, N. Wanderka, R. Schlesiger, T. Yamamoto, N. Lazarev, D. Isheim, G. Schmitz, Syo Matsumura, J. Banhart, Sr–Al–Si co-segregated regions in eutectic Si phase of Sr-modified Al–10Si alloy, Ultramicroscopy,, 132, 216-221, 2013.09, The addition of 200 ppm strontium to an Al–10 wt% Si casting alloy changes the morphology of the eutectic silicon phase from coarse plate-like to fine fibrous networks. In order to clarify this modification mechanism the location of Sr within the eutectic Si phase has been investigated by a combination of high-resolution methods. Whereas three-dimensional atom probe tomography allows us to visualise the distribution of Sr on the atomic scale and to analyse its local enrichment, transmission electron microscopy yields information about the crystallographic nature of segregated regions. Segregations with two kinds of morphologies were found at the intersections of Si twin lamellae: Sr–Al–Si co-segregations of rod-like morphology and Al-rich regions of spherical morphology. Both are responsible for the formation of a high density of multiple twins and promote the anisotropic growth of the eutectic Si phase in specific crystallographic directions during solidification. The experimental findings are related to the previously postulated mechanism of “impurity induced twinning”..
130. Ryuichiro Oguma, Syo Matsumura, Minoru Doi, Satoshi Hata, Keisuke Ogata, Application of TDGL Model to B2 Type Ordering with Two Step Phase Separation in Fe-Ni-Al Alloys, MRS online proceedings, 1518, 703-709, 2013.05.
131. Masaru Itakura, Natsuki Watanabe, Minoru Nishida, Takeshi Daio, Syo Matsumura, Atomic-Resolution X-ray Energy-Dispersive Spectroscopy Chemical Mapping of Substitutional Dy Atoms in a High-Coercivity Neodymium Magnet, Japanese Journal of Applied Physics, 10.7567/JJAP.52.050201, 52, 5, 050201-1-050201-4, 2013.05, We have investigated local element distributions in a Dy-doped Nd2Fe14B hot-deformed magnet by atomic-column resolution chemical mapping using an X-ray energy-dispersive spectrometer (XEDS) attached to an aberration-corrected scanning transmission electron microscope (Cs-corrected STEM). The positions of the Nd and Dy atomic columns were visualized in the XEDS maps. The substitution of Dy was limited to a surface layer 2–3 unit cells thick in the Nd2Fe14B grains, and the Dy atoms preferentially occupied the 4f-Nd sites of Nd2Fe14B. These results provide further insights into the principal mechanism governing the coercivity enhancement due to Dy doping..
132. Kohei Kusada, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Naoya, Sumi, Katsutoshi Sato, Katsutoshi Nagaoka, Yoshiki Kubota, Hiroshi Kitagawa, Discovery of Face-Centered-Cubic Ruthenium Nanoparticles: Facile Size-Controlled Synthesis Using the Chemical Reduction Method, Journal of the American Chemical Society, 10.1021/ja311261s, 135, 15, 5493-5496, 2013.04, We report the first discovery of pure face-centered-cubic (fcc) Ru nanoparticles. Although the fcc structure does not exist in the bulk Ru phase diagram, fcc Ru was obtained at room temperature because of the nanosize effect. We succeeded in separately synthesizing uniformly sized nanoparticles of both fcc and hcp Ru having diameters of 2–5.5 nm by simple chemical reduction methods with different metal precursors. The prepared fcc and hcp nanoparticles were both supported on γ-Al2O3, and their catalytic activities in CO oxidation were investigated and found to depend on their structure and size..
133. Md Jafar Sharif,, Miho Yamauchi, Shoichi Toh, Syo Matsumura, Shin-ichiro Noro, Kenichi Kato, Masaki Takata, Tatsuya Tsukuda, Enhanced magnetization in highly crystalline and atomically mixed bcc Fe-Co nanoalloys prepared by hydrogen reduction of oxide composites, Nanoscale, 10.1039/c2nr33467d, 5, 4, 1489-1493, 2013.03, FexCo100−x nanoalloys (NAs) with 20 ≤ x ≤ 80 were prepared by hydrogen reduction of Fe–Co oxide nano-composites, which were composed of mixed phases (or domains) of Fe2O3 and CoO. In situ X-ray diffraction (XRD) measurements using synchrotron radiation clearly showed development of a solid-solution Fe–Co phase by hydrogen reduction from the oxide composites. High-resolution transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM and powder XRD revealed that Fe–Co NAs form a single crystal structure and the two elements are mixed homogeneously. The saturation magnetization depends on the size and metal composition and shows the highest value (250 emu g−1) for the Fe70Co30 NA in the size range of 30–55 nm, which is comparable to that of the Fe70Co30 bulk alloy (245 emu g−1). This high magnetization is attributable to high crystallinity and homogeneous mixing of constituent atoms, which are attained by thermal treatment of oxide phases under a hydrogen atmosphere..
134. Seiya Takaki, Tomokazu Yamamoto, Kazuhiro Yasuda, Masanori Kutsuwada, Syo Matsumura, Atomistic observation of electron irradiation-induced defects in CeO2, MRS Symposium Proceedings, 10.1557/opl.2013.199, 1514, 93-98, 2013.02, We have investigated the atomistic structure of radiation-induced defects in CeO2 formed under 200 keV electron irradiation. Dislocation loops on {111} habit planes are observed, and they grow accompanying strong strain-field. Atomic resolution scanning transmission electron microscopy (STEM) observations with high angle annular dark-field (HAADF) and annular bright-field (ABF) imaging techniques showed that no additional Ce layers are inserted at the position of the dislocation loop, and that strong distortion and expansion is induced around the dislocation loops. These results are discussed that dislocation loops formed under electron irradiation are non-stoichiometric defects consist of oxygen interstitials..
135. Ryuichiro Oguma, Syo Matsumura, Minoru Doi, Satoshi Hata, Keisuke Ogata, Simulations of Structure Formation in B2 type Ordering with Two Step Phase Separation in Fe-Ni-Al Alloys, AIP Conference Proceedings, 1518, 703-709, 2012.12.
136. Y.Q. Wu, J.C. Barry, T. Yamamoto, Q.F. Gu, Syo Matsumura, S.D. McDonald, H. Huang, Kazuhiro Nogita, A new phase in stoichiometric Cu6Sn5, Acta Materialia, 10.1016/j.actamat.2012.08.024, 60, 19, 6581-6591, 2012.11, The intermetallic compound Cu6Sn5 is a significant microstructural feature of many electronic devices where it is present at the solder–substrate interfaces. The time- and temperature-dependent thermomechanical properties of Cu6Sn5 are dependent on the nature and stability of its crystal structure, which has been shown to exist in at least four variants (η, η′, η6 and η8). This research details an additional newly identified monoclinic-based structure in directly alloyed stoichiometric Cu6Sn5 using variable-temperature synchrotron X-ray diffraction (XRD) and transmission electron microscopy. The phase is associated with a departure from the equilibrium temperature of the polymorphic monoclinic–hexagonal transformation temperature. The new monoclinic phase can be treated as a modulation of four η8-Cu5Sn4 unit cells plus one η′-Cu6Sn5 unit cell. It has been labeled as η4+1 and has cell parameters of a = 92.241 Å, b = 7.311 Å, c = 9.880 Å and β = 118.95° determined from electron diffraction patterns. The XRD results could be fitted well to a Rietveld refinement using the new crystal parameters..
137. Hirokazu Kobayashi, Hitoshi Morita, Miho Yamauchi, Ryuichi Ikeda, Hiroshi Kitagawa, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Shoichi Toh, Syo Matsumura, Nanosize-Induced Drastic Drop in Equilibrium Hydrogen Pressure for Hydride Formation and Structural Stabilization in Pd-Rh Solid-Solution Alloys, Journal of the American Chemical Society, 10.1021/ja305031y, 134, 30, 12390-12393, 2012.08, We have synthesized and characterized homogeneous solid-solution alloy nanoparticles of Pd and Rh, which are immiscible with each other in the equilibrium bulk state at around room temperature. The Pd–Rh alloy nanoparticles can absorb hydrogen at ambient pressure and the hydrogen pressure of Pd–Rh alloys for hydrogen storage is dramatically decreased by more than 4 orders of magnitude from the corresponding pressure in the metastable bulk state. The solid-solution state is still maintained in the nanoparticles even after hydrogen absorption/desorption, in contrast to the metastable bulks which are separated into Pd and Rh during the process..
138. Kazu Suenaga, Toshiya Okazaki, Eiji Okunishi, Syo Matsumura, Detection of photons emitted from single erbium atoms in energy-dispersive X-ray spectroscopy, Nature Photonics, 10.1038/nphoton.2012.148, 6, 8, 545-548, 2012.08, The detection of photons emitted from single quantum objects is highly desirable for the diagnosis of nanoscale devices using microscopes. An extremely tiny probe (∼0.1 nm) with high current recently became available for aberration-corrected scanning transmission electron microscopy, and it is possible for individual atoms in nanoscale devices to be excited using such a highly focused probe1–3. Here, we demonstrate the successful
detection of characteristic X-ray signals from single erbium atoms using energy-dispersive X-ray spectroscopy. The intensities of the erbium L and M lines from a single erbium atom were extremely weak in comparison to the N edge of electron energy-loss spectroscopy, demonstrating the intrinsic difficulty in sensing single atoms using X-ray spectroscopy.
Nevertheless, this work will certainly help in the advance towards obtaining X-ray spectra from single atoms and to evaluate the fluorescence yield on a single-atom basis..
139. M. Timpel, N. Wanderka, R. Schlesiger, T. Yamamoto, N. Lazarev, D. Isheim, G. Schmitz, Syo Matsumura, J. Banhart, The role of strontium in modifying aluminium–silicon alloys
, Acta Materialia,, 60, 9, 3920–3928, 2012.05, Small amounts of strontium can transform the morphology of the eutectic silicon phase present in Al–Si casting alloys from coarse plate-like to fine fibrous networks. In order to understand this industrially important but hitherto insufficiently understood effect, the strontium distribution was studied in atomic resolution by atom probe tomography and in nanometre resolution by transmission electron microscopy. The combined investigations indicate that Sr co-segregates with Al and Si within the eutectic Si phase. Two types of segregations were found: (i) nanometre-thin rod-like co-segregations of type I are responsible for the formation of multiple twins in a Si crystal and enable its growth in different crystallographic directions; (ii) type II segregations come as more extended structures, restrict growth of a Si crystal and control its branching. We show how Sr enables both kinds of mechanisms previously postulated in the literature, namely “impurity-induced twinning” (via type I) and growth restriction of eutectic Si phase (via type II)..
140. Kazuhiro Yasuda, Tomokazu Yamamoto, Motoki Etoh, Shinji Kawasoe, Syo Matsumura, Norito Ishikawa, Accumulation of radiation damage and disordering in MgAl2O4 under swift heavy ion irradiation, International Journal of Materials Research , 10.3139/146.110564, 102, 9, 1082-1088, 2011.09.
141. R. Oguma, S. Matsumura, T. Eguchi , Mesoscopic TDGL Model for Formation of Domain Structures in D019 Type Ordering, Solid State Phenomena, 10.4028/, 172-174, 1, 602-607, 2011.07.
142. S. Hata, H. Miyazaki, S. Miyazaki, M. Mitsuharaa M. Tanaka, K. Kaneko, K. Higashida, K. Ikeda, H. Nakashima, S. Matsumura, J.S. Barnard, J.H. Sharp, P.A. Midgley , High-angle triple-axis specimen holder for three-dimensional diffraction contrast imaging in transmission electron microscopy, Ultramicroscopy, 10.1016/j.ultramic.2011.03.021, 111, 8, 1168–1175, 2011.07.
143. S.K. Son, Syo Matsumura, K. Fukui, M. Takeda, The compositions of metastable phase precipitates observed at peak hardness condition in an Al–Mg–Si alloy, Journal of Alloys and Compounds, 10.1016/j.jallcom.2010.08.151, 509, 2, 241-245, 2011.01, The metastable-phase precipitates which appear at the peak condition of hardness in an Al–0.83at%Mg–0.4at%Si alloy were investigated, using a combination of Vickers microhardness tests, DSC calorimetry, and field-emission STEM observations with EDX analyses. EDX and elemental mapping revealed that both Si-rich and Mg–Si precipitates with needle-shapes were present. EDX analysis showed that needle-shaped .
144. Y. Takahashi, M. Tanaka, K. Higashida, K. Yasuda, S. Matsumura, H. Noguchi,, A combined environmental straining specimen holder for high-voltage electron microscopy, Ultramicroscopy, Volume 110, Pages 1420-1427, 2010.10.
145. Kenichi Shiiyama, Tomokazu Yamamoto, Tatsuro Takahashi, Aurore Guglielmetti, Alan Chartier, Kazuhiro Yasuda, Syo Matsumura, Kazufumi Yasunaga, Constantin Meis, Molecular dynamics simulations of oxygen Frenkel pairs in cerium dioxide, Nuclear Instruments and Methods in Physics Research Section B, 10.1016/j.nimb.2010.05.022, 268, 19, 2980-2983, 2010.10, Molecular dynamics simulations of oxygen Frenkel pairs (FPs) in cerium dioxide (CeO2) were carried out in order to understand their kinetic behavior. The results show that an oxygen FP recombine with the vacancy and the interstitial after the vacancy jump preferentially along the 〈1 0 0〉 direction. When multiple oxygen FPs are introduced, the interstitials aggregate into a (1 1 1) plate-like cluster at relatively lower temperature lower than 600 K, while they recombine with vacancies at elevated temperatures higher than 900 K within 10 ps. Molecular mechanics calculations of oxygen FPs on a (1 1 1) plane show that the formation energy per a FP decreases with increase of the number of FPs. The theoretical results are consistent with the transmission electron microscopy observations of formation of 1/9〈1 1 1〉{1 1 1} oxygen interstitial platelets in CeO2 under electron irradiation..
146. H. Unno, Y. Sato, S. Toh, N. Yoshinaga, S. Matsumura, Microstructures and electrical properties of TiO2-doped Al2O3 ceramics, Journal of Electron Microscopy, Volume 59, Pages S107-S115, 2010.08.
147. M. Shirai, K. Tsumori, M. Kutsuwada, K. Yasuda, S. Matsumura , Morphological change in FePt nanogranular thin films induced by swift heavy ion irradiation, Nuclear Instruments and Methods in Physics Research Section B, Volume 267, Issue 10, Pages 1787-1791
, 2009.05.
148. M. Kinoshita, K. Yasunaga, T. Sonoda, A. Iwase, N. Ishikawa, M. Sataka, K. Yasuda, S. Matsumura, H. Y. Geng, T. Ichinomiya, Y. Chen, Y. Kaneta, M. Iwasawa, T. Ohnuma, Y. Nishiura, J. Nakamura, Hj Matzke, Recovery and Restructuring induced by Fission Energy Ion in High Burnup Nuclear Fuel, Nuclear Instruments and Methods in Physics Research Section B, Volume 267, Issue 6, Pages 960-96, 2009.05.
149. Aurore Guglielmetti, Alan Chartier, Laurent van Brutzel, Jean-Paul Crocombette, K. Yasuda, Constantin Meis, Syo Matsumura, Atomistic simulation of point defects behavior in ceria, Nuclear Instruments and Methods in Physics Research Section B, 266, 24, 5120-5125, 2008.12.
150. Kennichi Shiiyama, Tomokazu Yamamoto, Tetsuro Takahashi, Aurore Gulielmetti, Alain Chartier, Kazuhiro Yasuda, Syo Matsumura , Kazufumi Yasunaga, Constatin Meis, Molecular dynamics study of Frenkel pairs in cerium dioxide, Proceedings of the Fouth International Conference on Multiscale Materials Modeling (MMM2008), p. 598-601, 2008.11.
151. Alain Chartier, Tomokazu Yamamoto, Kazuhiro Yasuda, Constatin Meis, Kennichi Shiiyama, Syo Matsumura, Molecular dynamics simulation of irradiation induced phase transition in MgAl2O4, Proceedings of the Fouth International Conference on Multiscale Materials Modeling (MMM2008), p. 583-588, 2008.11.
152. Ryuichiro Oguma, Syo Matsumura, Tetsuo Eguchi, Mesoscopic TDGL model for microstructural evolution of L10 type ordering, Proceedings of the Fouth International Conference on Multiscale Materials Modeling (MMM2008), p. 480-483, 2008.11.
153. K. Kimura, K. Matsuyama, S. Hata, S. Matsumura, Dark-field TEM tomography of ordered domain morphology in a Ni4Mo alloy, Proceedings of the 14th European Microscopy Congress, Vol. 1, 325-326, 2008.09.
154. Alain Chartier, Tomokazu Yamamoto, Kazuhiro Yasuda, Constatin Meis, Syo Matsumura, Frenkel pair accumulation induced crystallization of amorphous MgAl2O4, Journal of Nuclear Materials, Volume 378, Issue 2, Pages 188-192, 2008.08.
155. K. Yasunaga, K. Yasuda, S. Matsumura, T. Sonoda, Electron energy-dependent formation of dislocation loops in CeO2, Nuclear Instruments and Methods in Physics Research Section B, 266, 2877-2881, 2008.07.
156. T. Yamamoto, A. Chartier, K. Yasuda, C. Meis, K. Shiiyama, S. Matsumura, Molecular dynamics simulation of point defect accumulation in MgAl2O4, Nuclear Instruments and Methods in Physics Research Section B, 266, 2676-2682, 2008.07.
157. K. Yasuda, T. Yamamoto, S. Seki, K. Shiiyama, S. Matsumura, Production and stability of radiation-induced defects in MgAl2O4 under electronic excitation, Nuclear Instruments and Methods in Physics Research Section B, 266, 2834-2841, 2008.07.
158. R. Oguma, S. Matsumura, T. Eguchi, Kinetics of B2- and D03-type ordering and formation of domain structures in Fe-Al alloys, Journal of Physics: Condensed Matter, 20, 275225, 2008.07.
159. S. Hata, T. Nakano, N. Kuwano, M. Itakura, S. Matsumura and Y. Umakoshi, Microscopic Properties of Long-Period Ordering in Al-Rich TiAl Alloys, Metallurgical and Materials Transactions A, 39, [7], 1610-1617, 2008.06.
160. R. Oguma, S. Matsumura, T. Eguchi, Formation of boundary structures in L10 type ordering, Complex Systems, page 776-779, 2008.05.
161. S. Hata, K. Kimura, H. Gao, S. Matsumura, M. Doi, T. Moritani, J.S. Barnard, J.R. Tong, J.H. Sharp, P.A. Midgley, Electron tomography imaging and analysis of γ’ and γ domains in Ni-based superalloys, Advanced Materials, 20, [10], 1905-1909, 2008.05.
162. M. Kato, N. Kawase, T. Kaneko, S. Toh, S. Matsumura, H. Jinnai, Maximum diameter of the rod-shaped specimen for transmission electron microtomography without the missing wedge, Ultramicroscopy, 108, [3], 221-229, 2008.03.
163. Hongye Gao, Shoichi Toh, Syo Matsumura, Seishi Abe, Shigehiro Ohnuma, Microstructure of Ge:Ta2O5 granular thin films: an application of TEM-tomography, Materials Transactions, Vol. 48, No. 10, 2567-2571, 2007.10.
164. K. Yasuda, T. Yamamoto, S. Matsumura, The atomic structure of disordered ion tracks in magnesium aluminate spinel, JOM, 59, [4], 27-30, 2007.04.
165. S.Miyamoto, S. Uehara, M. Sasoh, M. Sato, M. Toyohara, K. Idemitsu and S. Matsumura, Characterization of Cement Alteration Process by Transmission Electron Microscopy with high spatial resolution, Journal of Nuclear Engineering and Technology, 2006.11.
166. K. Yasuda, S. Matsumura, Radiation damage effects in insulators for fusion reactors: Microstructure evolution in MgO-Al2O3 system oxide crystal, Advances in Science and Technology, 45, 1961-1968, 2006.09.
167. K. Yasuda, T. Yamamoto, M. Shimada, S. Matsumura, Y. Chimi and N. Ishikaw, Atomic structure and disordering induced by 350 MeV Au ions in MgAl2O4, Nuclear Instruments and Methods in Physics Research Section B, 250, 238-244, 2006.06.
168. K. Yasunaga, K. Yasuda, S. Matsumura and T. Sonoda, Nucleation and growth of defect clusters in CeO2 irradiated with electrons, Nuclear Instruments and Methods in Physics Research Section B, 250, 114-118, 2006.06.
169. R. Oguma, T. Eguchi, S. Matsumura, S. K. Son, Formation of off-phase domains in L12 type ordering, Flow Dynamics: The Second International Conference on Flow Dynamics (AIP conference proceedings vol. 832), pp. 520-523, 2006.05.
170. M. Shimada, T. Yamamoto, K. Yasuda, S. Matsumura, Y. Chimi and N. Ishikawa, Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions, Nuclear Instruments and Methods in Physics Research B, 245[1], 235-238, (2006), 2006.03.
171. R. Oguma, T. Eguchi, S. Matsumura, S.K. Son, Domain growth and off-phase boundary structure in L12-type ordering, Acta Materialia, 54 [6], 1533-1539, (2006), 2006.03.
172. K. Kimura, T. Horiuchi, S. Hata, S. Matsumura, Tomographic dark-field TEM observation of ordered precipitates in a Ni-Mo alloy, Advanced Materials and Processes, Vol. 164, No. 2 (2006), 46-47., 2006.02.
173. M. Shirai, T. Horiuchi, A. Horiguchi, S. Matsumura, K.Yasuda, M. Watanabe, T. Masumoto, Morphological change in FePt nanogranular thin films induced by irradiation with 2.4 MeV Cu2+ ions: Electron tomography observation, Materials Transactions, 47 [1], 52-58, (2006), 2006.01.
174. Kousuke Kimura, Satoshi Hata, Syo Matsumura and Takao Horiuchi, Dark-field transmission electron microscopy for a tilt series of ordering alloys: toward electron tomography, Journal of Electron Microscopy, 10.1093/jmicro/dfi060, 54, 4, 373-377, 54 [4], 373-377, (2005), 2005.12.
175. S. Hata, K. Kimura, S. Matsumura, Y. Tomokiyo, T. Moritani, M. Doi, Three-dimensional observation of ordered and disordered precipitates using dark-field TEM tomography, Solid→Solid Phase Transformations in Inorganic Materials 2005, 449-454, 2005.12.
176. Y. Tomokiyo, K. Kimura, T. Horiuchi, S. Hata, S. Matsumura, TEM tomographic observation of ordered particles in Ni-based ordering alloys, Proc. The China – Japan – Korea Joint Symposium on Advanced Electron Microscopy incorporated in BCEIA 2005, 2005.11.
177. S. Matsumura, T. Horiuchi, K. Yasuda, K. Kaneko, M. Watanabe, T. Masumoto, Morphological change in FePt nanogranular films induced by irradiation with 100 keV He ions, Scripta Materialia, 10.1016/j.scriptamat.2005.04.044, 53, 4, 441-445, 53, 441-445, (2005), 2005.01.
178. S. Hata, K. Kimura, T. Horiuchi, S. Matsumura, Y. Tomokiyo,, Electron Tomography of Crystalline Microstructures by Diffraction Contrast Imaging: Application to Ordered Alloys, Microscopy and Microanalysis, Vol. 11, Supplement 2 (2005), 18-19, 2005.01.
179. K. Kimura, S. Hata, S. Matsumura, Y. Tomokiyo, Tomographic Dark-Field TEM Observation of Ordered and Disordered Precipitates in Ni-Al-Ti Alloy, Microscopy and Microanalysis, Vol. 11, Supplement 2 (2005), 344-345, 2005.01.
180. K. Kimura, T. Horiuchi, S. Hata, S. Matsumura, Y. Tomokiyo, Tomographic dark field observation of ordered precipitates in Ni-18 at%Mo alloy, Proc. 8th Asia-Pacific Conf. Electron Microscopy, (2004),194-195., 2004.06.
181. K. Kaneko, Y. Kato, S. Toh, S. Matsumura, S. Ohnuma, T. Masumoto, Effect of the nitrohen content in CoFe-AlN granular thin films, Proc. 8th Asia-Pacific Conf. Electron Microscopy, 2004.06.
182. M. Shimada, K. Yasuda, S. Matsumura, C. Kinoshita, Y. Chimi, N. Ishikawa, Atomic disordering in magnesium aluminate spinel around ion tracks induced by high-density electronic excitation, Proc. 8th Asia-Pacific Conf. Electron Microscopy, 2004.06.
183. S. Matsumura, T. Horiuchi, N. Fukunaga, M. Kutsuwada, K. Kaneko, Radiation-induced structural change in FePt nanogranular films, Proc. 8th Asia-Pacific Conf. Electron Microscopy, (2004), 704-705, 2004.06.
184. M.P. Oxley, M. Shimada, S. Matsumura, Generalized formulation for quantitative ALCHEMI of disordered solids, Proc. 8th Asia-Pacific Conf. Electron Microscopy, (2004), 161-162., 2004.06.
185. S. Matsumura, M. Shimada, K. Yasuda, C. Kinoshita, Structural Disordering in Magnesium Aluminate Spinel Compounds Under Ion-Beam Irradiation, MRS Symp. Proc., 792, 131-142, 792, 131-141, (2004), 2004.01.
186. K. Kaneko, S. Matsumura, A. Sadakata, K. Fujita, W.-J. Moon, S. Ozaki, N. Nishimura, Y. Tomokiyo, Characterization of carbides at different boundaries of 9Cr-steel, Mater. Sci. Eng. A, 10.1016/j.msea.2003.12.065, 374, 1-2, 82-89, 374[1-2], 82-89, (2004), 2004.01.
187. M. Shimada, S. Matsumura, K. Yasuda, C. Kinoshita, Y. Chimi, N. Ishikawa, A. Iwase, Radiation-induced disordering in magnesium aluminate spinel subjected to ionizing radiation, J. Nuclear Mater., 10.1016/j.jnucmat.2004.04.161, 329, 1446-1450, 329-333, 1446-1450 (2004), 2004.01.
188. C. Kinoshita, K. Yasuda, S. Matsumura, M. Shimada, Effect of simultaneous displacive and ionizing radiations and of electric field on radiation damage in ionic crystals, Metal. Mater. Trans. A, 10.1007/s11661-006-0205-9, 35A, 8, 2257-2266, 35A, 2257-2266 (2004), 2004.01.
189. K. Yasuda, C. Kinoshita, S. Matsumura, A.I. Ryazanov, Radiation-induced defect clusters in fully stabilized zirconia irradiated with ions and/or electrons, Journal of Nuclear Materials, 10.1016/S0022-3115(03)00136-3, 319, 74-80, Vol. 319, page 74-80, 2003.09.
190. X.Z. Liao, J. Zou, D.J.H. Cockayne, S. Matsumura, [001] zone-axis bright-field diffraction contrast from coherent Ge(Si) islands on Si(001), Ultramicroscopy, 10.1016/j.ultramic.2003.08.017, 98, 2-4, 239-247, 2003.12.
191. K. Kaneko, S. Matsumura, K. Ikematsu, Y. Kato, Y. Tomokiyo, M. Watanabe, T. Masumoto, Quantitative electron microscopy of FePt nano-crystallites in amorphous Al2O3 matrix, Scripta Materialia, 10.1016/S1359-6462(02)00627-9, 48, 7, 915-920, 48, 915-920, 2003.08.
192. J. Pacaud, J.M. Zuo, R. Hoier, S. Matsumura, Quantitative electron diffraction evidence for one-dimensional ordering in magnetite above the Verwey transition, Microscopy and Microanalysis, 10.1017/S1431927603030393, 9, 5, 475-483, Vol.9, 475–483, 2003.08.
193. In-Tae Bae, M. Ishimaru, Y. Hirotsu, S. Matsumura, K. E. Sickafus, Ion-beam-induced amorphous structures in silicon carbide, Nuclear Instruments and Methods in Physics Research B, Vol.206, 974-978, 2003.08.
194. K. Kaneko, K. Fujita, A. Sadakata, Y. Tomokiyo, S. Matsumura, Nanostructural and nanoelemental analysis of metastable M3C-type carbides with alloy-rich layer in heat resistant 2Cr-martensitic steel, Scripta Materialia, 10.1016/S1359-6462(02)00534-1, 48, 6, 761-765, 48, 761-765, 2003.06.
195. M. Ishimaru, In-Tae Bae, Y. Hirotsu, S. Matsumura, K. E. Sickafus, Structural relaxation of amorphous silicon carbide, Physical Review Letters, 10.1103/PhysRevLett.89.055502, 89, 5, 89, 055502, 2002.10.
196. A. Sadakata, K. Kaneko, K. Fujita, Y. Tomokiyo, S. Matsumura, Characterization of precipitated carbides at the boundaries, Proc. 15th Int'l. Cong. Electron Microscopy, 1, 775-776, 2002.09.
197. M. Shimada, S. Matsumura, T. Soeda,C. Kinoshita, Electron channeling enhanced x-ray microanalysis of radiation-induced disordering in MgO·nAl2O3, Proc. 16th Int'l. Cong. Electron Microscopy, 1, 187-188, 2002.09.
198. S. Matsumura, T. Soeda, M. Shimada, N.J. Zaluzec, Precise determination of atom configuration in partially disordered spinel compounds by HARECXS, Proc. 17th Int'l. Cong. Electron Microscopy, 1, 181-182, 2002.09.
199. C. Abromeit, S. Matsumura, Kinetics of antiphase domain boundaries during an L12 order-disorder phase transformation: a Monte Carlo simulation, Philosophical Magazine A, 10.1080/01418610210138950, 82, 11, 2287-2302, 82, 2287-2302, 2002.08.
200. T. Soeda, M. Shimada, S. Matsumura, N.J. Zaluzec, C. Kinoshita, Radiation-induced disordering in magnesium aluminate spinel studied by electron channeling x-ray spectroscopy, Proc.the 4th Pacific Rim International Conference on Advanced Materials and Processing (PRICM4), 1423-1426, 129-134, 2001.10.
201. S. Matsumura, T. Soeda, N.J. Zaluzec, C. Kinoshita, Electron channeling x-ray microanalysis for cation configuration in irradiated magnesium alminate spinel, Advances in Materials Problem Solving with the Electron Microscope, 589, 129-134, 129-134, 2001.07.
202. S. Matsumura, Y. Tanaka, Y. Koga, K. Oki, Concurrent ordering and phase separation in the vicinity of the metastable critical point of order-disorder transition in Fe-Si alloys, Materials Science and Engineering A, 10.1016/S0921-5093(00)01874-8, 312, 1-2, 284-292, 312, 284-292, 2001.05.
203. T. Yamamoto, K. Yasuda, K. Shiiyama, S. Matsumura, C. Kinoshita, T. Shikama, Comparison of microstructure of a-alumina irradiated with ions and fast neutrons under an applied electric field, Proc. 8th Asia-Pacific Conf. Electron Microscopy, (2004), 720-721..
204. S. Hata, T. Mitate, N. Kuwano, S. Matsumura, D. Shindo, K. Oki, Short range order structures in fcc-based Ni-Mo studied by high resolution transmission electron microscopy with image processing, Materials Science and Engineering A, 10.1016/S0921-5093(00)01872-4, 312, 1-2, 160-167, 312, 160-167, 2001.05.