記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：Acta Materialia  

In this study, the microstructure of polycrystalline Co-doped BaFe2As2 superconducting bulks was comprehensively analyzed. The synthesis process involved ball milling and subsequent spark plasma sintering (SPS). A strong correlation between the microstructure and synthesis conditions was observed. Specifically, when mechanochemical synthesis of raw metal powders was carried out at a ball milling energy (EBM) of 100 MJ/kg, the resulting Co-BaFe2As2 bulk contained nanograins with a high density of planar defects and exhibited a high critical current density (Jc) under both magnetic and self-fields. The findings suggest that planar defects are one of the influential factors on the superconducting properties. Atomic-resolution microstructural characterization revealed that the planar defects are parallel to (001) and exhibit distinctive atomic arrangements. Atomic-resolution elemental mappings displayed a remarkable barium concentration in planar defects and grain boundaries compared to the BaFe2As2 matrix. Local strain fields were also observed around planar defects, especially near their edges. These nanoscale strain fields could be considered as volumetric pinning centers, and effectively pin flux vortices in the random crystal orientation, thereby increasing Jc in the Fe-based superconducting bulk. Additionally, an extended investigation was performed to include a K-doped BaFe2As2 bulk that exhibits similar planar defects. Based on the results of the microstructural analysis, speculations were mode on the evolution process of the microstructure during the preparation of BaFe2As2 bulks.

DOI： 10.1016/j.actamat.2024.119648

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Small  

Abstract

Enhancing the mobility of lithium‐ions (Li⁺) through surface engineering is one of major challenges facing fast‐charging lithium‐ion batteries (LIBs). In case of demanding charging conditions, the use of a conventional artificial graphite (AG) anode leads to an increase in operating temperature and the formation of lithium dendrites on the anode surface. In this study, a biphasic zeolitic imidazolate framework (ZIF)‐AG anode, designed strategically and coated with a mesoporous material, is verified to improve the pathways of Li⁺ and electrons under a high charging current density. In particular, the graphite surface is treated with a coating of a ZIF‐8‐derived carbon nanoparticles, which addresses sufficient surface porosity, enabling this material to serve as an electrolyte reservoir and facilitate Li⁺ intercalation. Moreover, the augmentation in specific surface area proves advantageous in reducing the overpotential for interfacial charge transfer reactions. In practical terms, employing a full‐cell with the biphasic ZIF‐AG anode results in a shorter charging time and improved cycling performance, demonstrating no evidence of Li plating during 300 cycles under 3.0 C‐charging and 1.0 C‐discharging. The research endeavors to contribute to the progress of anode materials by enhancing their charging capability, aligning with the increasing requirements of the electric vehicle applications.

DOI： 10.1002/smll.202310201

Web of Science

Scopus

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.matchemphys.2023.128223

researchmap

記述言語：その他   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE Transactions on Applied Superconductivity  

For obtaining microscopic knowledge toward a fabrication process of (Bi,Pb)2Sr2Ca2Cu3Ox (Bi,Pb-2223) single-phase material, we fabricated a multilayered film on a SrTiO3(001) substrate by a sputtering method using (Bi,Pb)2Sr2CaCu2Oy (Bi,Pb-2212) and Pb-Ca-Cu-O targets alternately at 650 °C. The as-grown film was an epitaxially grown multilayered film consisting of Bi,Pb-2212 and Pb-Ca-Cu-O layers. Coarse grains of impurity phases were also formed within the multilayered film, and these impurity phases were difficult to eliminate even after heat treatments. After 10 h heat treatment at 840 °C with Bi,Pb-2223 pellets, the phase transition from Bi,Pb-2212 to Bi,Pb-2223 occurred in the multilayered film. The phase transition to Bi,Pb-2223 proceeded preferentially at the interface with the impurity phases and the Pb-Ca-Cu-O layers. These observation results suggest that the impurity phases promote three-dimensional atomic diffusion in the multilayered film to accelerate the phase transition to Bi,Pb-2223, as well as consume constituent elements, Ca, Cu and O. Even after the 100 h heat treatment at 840 °C with Bi,Pb-2223 pellets, the phase transition from Bi,Pb-2212 to Bi,Pb-2223 did not proceed completely, and the fraction of the Bi,Pb-2223 phase in the whole superconducting phases was ∼50%. It is suggested that controlling the formation and microstructure of the impurity phases is a key to further increasing the fraction of the Bi,Pb-2223 phase.

DOI： 10.1109/tasc.2023.3259920

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.jallcom.2023.169450

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.23-00017

researchmap

記述言語：その他   掲載種別：研究論文（学術雑誌）  

In iron-based superconductors, randomly oriented grain boundaries have a strong influence on the transport properties via intrinsic weak-link and flux pinning mechanisms. Herein we report the critical current density (Jc) and the three-dimensional microstructure of polycrystalline bulk Co-doped Ba122 (BaFe1.84Co0.16As2) superconductors, with highly dense grain boundaries (grain size smaller than 50 nm), produced by high-energy milling. Three-dimensional electron microscopy revealed that the anomalous growth of secondary particles (aggregation) and the inter-aggregation structures were significantly different in the samples with finer grains, which may have extrinsically limited Jc. These important microstructural features were quantified as two parameters—local thickness and total pore length—by reconstructing the three-dimensional structure of the superconducting phase using the adaptive thresholding method. The results obtained in this study suggest that understanding and controlling the microstructural formation process by sintering are instrumental for improving the Jc properties of 122 polycrystalline materials consisting of ultrafine grains.

DOI： 10.1016/j.jallcom.2022.166358

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AIP Publishing  

Anomalous Nernst effect of epitaxial Fe4N films on MgO(001), MgAl2O4(MAO)(001), and SrTiO3(STO)(001) substrates grown by molecular beam epitaxy was investigated. Moderately large anomalous Nernst coefficients (S-ANE) of 1.4 and 1.7 mu V/K were obtained in the Fe4N films on the MgO(001) and MAO(001) substrates, respectively, and large anomalous Hall angles (similar to 0.06) and transverse thermoelectric conductivities [similar to 1.3 A/(m K)] were derived from the experimental results. On the other hand, a large effective S-ANE of 2.8 mu V/K was obtained in the Fe4N film on the STO(001) substrate. The origin of the enhanced effective SANE is the negatively large Seebeck coefficient (S-SE) in an oxygen deficient STO layer near the surface of the STO substrate. This indicates that it is possible to enhance the effective S-ANE of ferromagnetic materials by utilizing adjacent materials with large vertical bar S-SE vertical bar such as the oxygen deficient STO layer. Published under an exclusive license by AIP Publishing.

DOI： 10.1063/5.0102928

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Iron-based superconductors are expected to be used in strong magnet applications owing to their excellent superconducting properties. The process of sintering a mechanically alloyed precursor powder is effective in achieving a high upper critical field and critical current density in BaFe2As2 (Ba122) polycrystalline bulk materials. However, when this process is applied to K-doped Ba122, which shows the highest critical temperature in the Ba122 family, suppressing the vaporization of potassium is challenging. In this study, spark plasma sintering (SPS) method was applied to K-doped Ba122 to achieve fast densification. In contrast to the conventional synthesis method, which requires several tens of hours, optimally K-doped bulks with near theoretical density were obtained after only 5 min of SPS, and the magnetic critical current density reached 105 A/cm2 at 5 K. The demonstrated superconducting properties suggest that this fast densification technique is a useful tool for applying K-doped Ba122 to bulk trapped field magnets.

DOI： 10.1016/j.isci.2022.103992

PubMed

researchmap

記述言語：その他   掲載種別：研究論文（学術雑誌）  

The typical experimental conditions inside a transmission electron microscope (TEM), such as ultra-high vacuum, high-energy electron irradiation, and surface effects of ultrathin TEM specimens, can be the origin of unexpected microstructural changes compared with that of bulk material during in situ thermal-annealing experiments. In this paper, we report on the microstructural changes of a Fe-15%Si alloy during in situ TEM annealing, where, in its bulk form, it exhibits an ordering transformation from D03 to B2 at 650 °C. Using a heating-pot type double tilt holder with a proportional-integral-differential control system, we observed the precipitation of α-Fe both at the sample surface and inside the sample. Surface precipitates formed via surface diffusion are markedly large, several tens of nm, whereas precipitates inside the specimen, which are surrounded by Fe-poor regions, reach a maximum size of 20 nm. This unexpected microstructural evolution could be attributed to vacancies on Si sites, which are induced due to high-energy electron irradiation before heating, as well as enhanced thermal diffusion of Fe atoms.

DOI： 10.1063/5.0070471

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS & MATERIALS  

In situ electron irradiation using high-resolution transmission electron microscopy (HRTEM) was performed to visualize the Frank loop evolution in aluminum-copper (Al-Cu) alloy with an atomic-scale spatial resolution of 0.12 nm. The in situ HRTEM observation along the [110] direction of the FCC-Al lattice, Frank partial dislocation bounding an intrinsic stacking fault exhibited an asymmetrical climb along the (112) direction opposed to those in the reference pure Al under an electron irradiation, with a corresponding displacement-per-atom rate of 0.055- 0.120 dpa/s in a high vacuum (1.2 (c) 1015 Pa). We performed theoretical calculations to simulate the asymmetrical climb of the dislocation with Burgers vector b of 1/3(111). The Cu-Cu bonding in Guinier-Preston zones was described as a possible pinning site of the dislocation climb by molecular dynamics simulation.

DOI： 10.2320/matertrans.MT-M2021233

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)  

Superconducting Properties and Microstructure of In-situ Cu Addition Low Activation MgB₂ Multifilamentary Wires Using Different Boron-11 Isotope Powders

DOI： 10.2221/jcsj.57.31

CiNii Research

J-GLOBAL

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Oxide dispersion strengthened Cu alloys (ODS-Cu) having dispersed yttria (Y2O3) fabricated using hot isostatic pressing (HIP) of mechanically alloyed (MA) Cu-Y powders. They exhibited a heterogeneous mixed grain structure, which were composed of a large and small Cu grain area. In the small Cu grain regions, Y2O3 particles were segregated along the grain boundaries, and acted as a crack propagation path, leading to brittle fracture. Therefore, we investigated the microstructural changes by the MA and heat treatment processes for the microstructure optimization. The powders of 4 to 32 MA hours formed a nested crust-like layered structure with large and small Cu grains. The layers were destroyed by heat treatment at 500 degrees C, because recrystallization and grain growth of Cu occurred in the temperature range of 310 - 330 degrees C. It was considered that Y2O3 was moved out to the circumferential area of the powders. Based on these results, it was suggested that the structural changes inside MA powders during HIP are the essential factor of the Y2O3 distribution within the Y2O3-added ODS-Cu alloys.

DOI： 10.1016/j.fusengdes.2021.112804

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Heusler alloys are a material class exhibiting various magnetic properties, including antiferromagnetism. A typical application of antiferromagnets is exchange bias that is a shift of the magnetization curve observed in a layered structure consisting of antiferromagnetic and ferromagnetic films. In this study, a layered sample consisting of a Heusler alloy, Mn2VAl and a ferromagnet, Fe, is selected as a material system exhibiting exchange bias. Although the fully ordered Mn2VAl is known as a ferrimagnet, with an optimum fabrication condition for the Mn2VAl layer, the Mn2VAl/Fe layered structure exhibits exchange bias. The appearance of the antiferromagnetic property in the Mn2VAl is remarkable; however, the details have been unclear. To clarify the microscopic aspects on the crystal structures and magnetic moments around the Mn2VAl/Fe interface, cross-sectional scanning transmission electron microscope (STEM) observation, and synchrotron soft X-ray magnetic circular dichroism (XMCD) measurements were employed. The high-angle annular dark-field STEM images demonstrated clusters of Mn2VAl with the L2(1) phase distributed only around the interface to the Fe layer in the sample showing the exchange bias. Furthermore, antiferromagnetic coupling between the Mn- and Fe-moments were observed in element-specific hysteresis loops measured using the XMCD. The locally ordered L2(1) phase and antiferromagnetic Mn-moments in the Mn2VAl were suggested as important factors for the exchange bias.

DOI： 10.3390/nano11071723

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The precipitation behaviors of alloy nitrides during the high-temperature tempering of Fe-0.3mass%N-1mass%M (M: Cr, Mo, Mn, or Si) martensite obtained by gaseous nitriding and quenching was investigated. Resistance to temper softening was observed with the addition of Mn, Cr, and Mo and secondary hardening occurred in the Cr and Mo alloys at tempering temperature above 673K although Si addition did not result in clear change in temper softening in comparison to the Fe-N binary case. X-ray diffraction analysis and conventional TEM observation shows the precipitation of iron nitride (gamma'-Fe4N) and alloy nitride during tempering at 773K. Cs-corrected STEM-HAADF observation revealed that metastable mono-layered nitrogen-alloying element clusters are formed along {001}alpha' plane and they are eventually thickened into B1-type MN precipitate in the Cr and Mo alloys. In the Mn alloy, B1-type Mn nitride was detected which presumably changes to eta-Mn3N2 by thickening. 3DAP analysis confirmed the ratio of nitrogen and alloying element of the nitride corresponds to the structure deduced by STEM-HAADF. Clustering analysis of 'matrix' indicated that there are still finer clusters which could not be clearly visualized in STEM-HAADF and 3DAP. Hardness after tempering was examined by strengthening by precipitation and dislocations, suggesting that undetected Cr-N clusters should contribute to hardening in the Cr alloy. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actamat.2020.116612

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 Acta Materialia Inc. Multi-scale characterization techniques, including computed tomography (CT) based on serial sectioning by focused ion beam (FIB) and scanning transmission electron microscopy (STEM), have been employed to elucidate the microstructural hierarchy inside yttria (Y2O3) dispersed copper alloys designed for fusion reactors. The alloys were fabricated by the combination of mechanical alloying of metal and oxide powders and subsequent hot isostatic pressing. Optical microscopy, together with electron micro-probe analysis revealed bimodal size distribution of powders, where coarse Cu powders of several hundred micrometer are composed of metallic core surrounded by a crust of Cu oxides, while fine powders of several ten micrometer are mostly of oxides. Scanning electron microscopy (SEM) on the fabricated bulk alloys revealed heterogeneous inner structure, which is best described by an assembly of large Cu grain regions bordered by small Cu grain regions. Distribution of Y2O3 particles are visualized three dimensionally by serial sectioned FIB-SEM images and by CT-STEM, both of which revealed the particles are enriched in small Cu grain regions. These multi-scale characterization, together with mechanical bend testing, demonstrated that excess Y2O3 particles in grain boundaries leads to brittle fracture, while that large Cu grains are responsible for the ductility of the alloy.

DOI： 10.1016/j.mtla.2020.100892

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 Elsevier B.V. A copper-based material is the recent main trend of advanced heat sink materials for the solid divertor systems, providing an optimal combination of excellent mechanical strength and superior thermal conductivity under severe neutron irradiation environment. In particular, oxide dispersion strengthened Cu (ODS-Cu) alloy with yttrium oxide (Y2O3) nano-particles is one of the promising materials because of the lower influence of the particles on thermal conductivity and the higher resistance to coarsening of the particles due to their thermodynamic stability. The metal Y as the Y2O3 source has been used to fabricate ODS-Cu alloys in the previous work. In this study, we used the Cu6Y intermetallic compound as the new Y source material to form Y2O3 particles during mechanical alloying (MA) followed by hot isostatic pressing (HIP) process, and successfully fabricated ODS-Cu alloy with Y2O3 nano-particles using the Cu6Y compound. The effects of Cu2O addition in this process as the oxidant material were also investigated. Y2O3 nano-particles with typical size of 30 nm were successfully formed into the Cu intra-grains and around grain boundaries, and the density of the Y2O3 nano-particles increased by the Cu2O addition. Cu2O addition promoted the oxidation of Y from the Cu6Y compound, forming Y2O3 nano-particles.

DOI： 10.1016/j.fusengdes.2020.112045

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 IOP Publishing Ltd. The effect of microstructure control on intergranular critical current density (J c) was evaluated using Co-doped Ba122 as a model material. Polycrystalline bulk samples were prepared by sintering mechanically alloyed powder prepared by planetary ball milling. Between low and intermediate milling energy, refinement of grain size, improvement in the uniformity of structure and composition, and a threefold improvement in J c were observed with increasing milling energy. These indicate that the high-energy milling is an effective method for the synthesis of single-phase Ba122 samples and improvement of J c by controlling the microstructure. At very high milling energy, the grain size of Ba122 reached as small as 30 nm, abnormal aggregates were formed, and the magnetic T c and J c decreased. Our results suggest that the suppression of the formation of large aggregates and control of grain boundary properties are necessary to achieve superior critical current properties.

DOI： 10.1088/1361-6668/aba545

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 To better understand the thermal stability of dislocation loops formed by long-term neutron irradiation in reactor pressure vessel (RPV) steels, in-situ scanning transmission electron microscopy (STEM) observation was performed for a surveillance test specimen of a European pressurized water reactor (PWR). The surveillance test specimen was neutron irradiated to a fluence of 8.2 × 1023 neutrons•m−2. A membrane sample from the surveillance test specimen was annealed at 673 K and 723 K for 30 min using a heating holder, and the same area was in-situ observed under STEM. After annealing, dislocation loops with Burgers vectors of ½ 〈111〉 and 〈100〉 were quantitatively examined. When annealing temperature increased from 673 K to 723 K, the number of dislocation loops decreases, whereas the size of them becomes larger. Correspondingly, the proportion of 〈100〉 dislocation loops changes from 27% to 45%. The ratio of 〈100〉 to ½ 〈111〉 loops increases with annealing temperature rising. The evolution process of dislocation loops during annealing at 723 K was in-situ observed and analyzed to shed light on the transformation mechanism of dislocation loops going from ½ 〈111〉 to 〈100〉. It is the first time to directly observe that two ½ 〈111〉 dislocation loops collide with each other and coalesce to form a 〈100〉 dislocation loop. Moreover, small ½ 〈111〉 dislocation loops could be absorbed by large 〈100〉 dislocation loops, whereas the Burgers vector of 〈100〉 loops remained unchanged. Dislocation decoration occurs during annealing due to the interaction between dislocations and loops. The dislocations decorated by loops are pretty stable during the continuous annealing process, which is well explained by molecular dynamics simulation.

DOI： 10.1016/j.mtla.2020.100778

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 Dispersion-strengthened (DS) copper alloys with Y2O3 particles are known as high strength and high thermal conductivity materials having potential for heat sink materials of fusion devices. In the previous study on mechanical alloying (MA) and hot isostatic pressing (HIP) processing of DS-Cu alloys, the MA powders showed various morphology and size distribution which influenced the properties of the MA-HIP samples. In this study, the MA alloyed powders with 3 wt% Y2O3 particles were classified by their size and characterized. The particles ranged from fine particles of under 46 μm to coarse particles of 212 μm over, and a wide particle size distribution was confirmed. The peeled Cu-O fragments from coarser MA powders are the main source of finer grain with 46 μm. The finer grains had oxide-like behavior as microstructural and mechanical properties. On the other hand, the coarser powder having over 212 μm had metal-like behavior as microstructural and mechanical properties. We thought that the classification of the MA powder before HIP process was one of the suitable process to optimize the microstructure and several properties of ODS-Cu alloy.

DOI： 10.1016/j.nme.2020.100773

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 Author(s). L10-orderd FeNi alloy films with a high degree of order (S) and a large uniaxial magnetic anisotropy energy (Ku) were realized by denitriding FeNiN films. FeNiN films with the a-axis perpendicular to the film plane were epitaxially grown on SrTiO3 (001) substrates by molecular beam epitaxy by changing the growth temperatures (TS) to 200, 250, and 350 °C. The a-axis oriented epitaxial L10-FeNi films were fabricated by annealing the FeNiN films in a H2 gas atmosphere at 300 °C. S and Ku of the denitrided L10-FeNi films were characterized by anomalous X-ray diffraction using synchrotron radiation and magnetic torque measurements, respectively. A high S of 0.87 and a Ku of 5.9 × 105 J/m3 were realized in the L10-FeNi film with a TS of 350 °C. This high S value exceeds the values reported on L10-FeNi to date, but the Ku value was comparable to those of c-axis oriented L10-FeNi films with S ∼0.5 grown by alternate monoatomic deposition of Fe and Ni layers. A possible origin for the suppressed macroscopic Ku in a-axis oriented L10-FeNi films is discussed, and denitriding FeNiN is a promising method for the fabrication of L10-FeNi with a high S and a large Ku.

DOI： 10.1063/5.0011875

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Controlling the feature sizes of 3D bicontinuous nanoporous (3DNP) materials is essential for their advanced applications in catalysis, sensing, energy systems, etc., requiring high specific surface area. However, the intrinsic coarsening of nanoporous materials naturally reduces their surface energy leading to the deterioration of physical properties over time, even at ambient temperatures. A novel 3DNP material beating the universal relationship of thermal coarsening is reported via high-entropy alloy (HEA) design. In newly developed TiVNbMoTa 3DNP HEAs, the nanoporous structure is constructed by very fine nanoscale ligaments of a solid-solution phase due to enhanced phase stability by maximizing the configuration entropy and suppressed surface diffusion. The smallest size of 3DNP HEA synthesized at 873 K is about 10 nm, which is one order of magnitude smaller than that of conventional porous materials. More importantly, the yield strength of ligament in 3DNP HEA approaches its theoretical strength of G/2π of the corresponding HEA alloy even after thermal exposure. This finding signifies the key benefit of high-entropy design in nanoporous materials—exceptional stability of size-related physical properties. This high-entropy strategy should thus open new opportunities for developing ultrastable nanomaterials against its environment.

DOI： 10.1002/adma.201906160

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2002-2011 IEEE. Bi,Pb-2223 phase on SrTiO3(100) fabricated by RF sputtering and annealing method have been investigated. We tried to fabricate Bi,Pb-2223 phase using multilayered precursors of Bi-2212 and Ca-Cu-Pb-O. We fabricated a multilayered film as a precursor by using two kinds of sputtering targets of Bi,Pb-2212 and Ca-Cu-Pb-O. After deposition by sputtering, the multi-layered precursor was annealed with Bi,Pb-2223 pellets at 840 °C for 100 h. From the X-ray diffraction (XRD) measurements, the main peaks of the precursor film were of Bi,Pb-2212 phase, but still remained large impurity phase. From the transmission electron microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) observation, we confirmed that a multilayer combination of a Bi,Pb-2212 layer and Ca-Cu-Pb-O layer was formed. After annealing, we determined the Tc through resistance measurements. The Tc value determined by the four-probe method was Tczero = 104.K. Furthermore, we observed two phases of Bi,Pb-2223 and Bi,Pb-2212 by XRD measurement. These results suggest that the Bi,Pb-2223 phase transformed from multilayered precursor film of Bi,Pb-2212 and Ca-Cu-Pb-O formed.

DOI： 10.1109/TASC.2019.2907229

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 IOP Publishing Ltd. The evolution of intra-and inter-granular structures in Co-doped BaFe2As2 (Ba-122) has been studied to address key issues associated with limited inter-granular current transport in randomly oriented polycrystalline Fe-based superconducting materials. We found that the following phenomena occur with an increase in reaction temperature: (i) significant grain growth; (ii) formation and evolution of two types of cracks; (iii) enhancement in the intra-granular current loop; (iv) reduction of magnetic shielding volume; and (v) decrease of the inter-granular transport current. A strong correlation between the inverse grain size and the inter-granular current density was observed. These results indicate that the key microstructural feature to achieve high transport current is a small grain size with no inter-granular cracks, and that low temperature synthesis is an effective path to this end. Based on the observed stacking faults and inter-granular amorphous layers, we propose a model for the formation of the two types of cracks in a polycrystalline Ba-122 phase, i.e. intra-and inter-granular cracks.

DOI： 10.1088/1361-6668/ab0eb6

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 The Author(s). The in situ annealing observation in transmission electron microscope (TEM) is one of the effective methods for imaging thermally induced microstructural changes. For applying this dynamical characterization to bulk samples fabricated by ion-milling, electropolishing or focused ion beam (FIB) mill, it is generally needed to use a heating-pot type system. We here report an initial trial to improve the spatial and temporal resolution during the in-situ annealing observation of bulk samples using a spherical aberration corrected (AC) TEM with a new thermal control unit. The information limit of 1.5Å and the point resolution of 2.0Å are achieved under isothermal annealing at 350°C, which is the same resolution at room temperature, and it is affected strongly of sample drift by the temperature variation. The sample is heated at a heating rate of +1.0°C/s, the drift distance observed by a TV readout speed CCD camera is less than 2.0 Å/s.

DOI： 10.1093/jmicro/dfz010

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 IOP Publishing Ltd. Atomic-scale relaxations of platinum nanoparticles (Pt NPs) for fuel-cell catalysts are evaluated by spherical-aberration corrected environmental transmission electron microscopy (ETEM) under reference high-vacuum and N 2 atmospheres, and then under reactive H 2 , CO and O 2 atmospheres, combined with ex situ durability test using an electrochemical half-cell. In high-vacuum, increasing roughness due to continuous relaxation of surface-adsorbed Pt atoms is quantified in real-space. Under H 2 and N 2 atmospheres at a critical partial pressure of 1 ×10 -2 Pa the stability of the surface facets is for the first time found to be improved. The adsorption behaviour of CO molecules is investigated using experimentally measured Pt-Pt bond lengths on the topmost surface layer of Pt NPs. The deactivation of Pt NPs in the anode environment of a proton-exchange-membrane fuel-cell is demonstrated at the atomic-scale in the ETEM, and the transformation of NPs into disordered nanoclusters is systematically quantified using the partial size distribution of Pt atomic clusters under controlled heating experiments at 423, 573 and 723 K.

DOI： 10.1088/1361-6528/aafe1e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2018 Elsevier B.V. We elucidate the microstructural evolution in MgB2 wires fabricated at two different temperatures by the internal Mg diffusion (IMD) method via multiple-scale microstructural observations. The critical current (Ic) of MgB2 wire was enhanced by the IMD method; however, the Ic of MgB2 was not sufficiently high to allow its practical applications. To prepare MgB2 by the IMD method, molten Mg is required to infiltrate the gaps between the B grains and penetrate each B grain. Here, we suggest that controlling the infiltration and penetration behaviors of Mg are key to enhancing the Ic of MgB2 fabricated by the IMD method. One reason for the decrease in Ic is the existence of residual B grains in the MgB2 crystalline region, which has an area fraction of 25% even in the MgB2 wire exhibiting the highest Ic. The amount of residual B grains, which formed due to the insufficient penetration distance of Mg atoms in the B grain, decreased after high-temperature treatment. However, the microstructure of the MgB2 wire fabricated at a temperature higher than the melting point of Mg was non-uniform because Mg infiltrated the gap between the B grains rapidly and non-uniformly. Thus, optimization of heat treatment temperature can effectively control the infiltration and penetration of Mg in the B grains, yielding uniform microstructures.

DOI： 10.1016/j.jallcom.2018.01.012

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2017 The Author(s). Tetrataenite (L10-FeNi) is a promising candidate for use as a permanent magnet free of rare-earth elements because of its favorable properties. In this study, single-phase L10-FeNi powder with a high degree of order was synthesized through a new method, nitrogen insertion and topotactic extraction (NITE). In the method, FeNiN, which has the same ordered arrangement as L10-FeNi, is formed by nitriding A1-FeNi powder with ammonia gas. Subsequently, FeNiN is denitrided by topotactic reaction to derive single-phase L10-FeNi with an order parameter of 0.71. The transformation of disordered-phase FeNi into the L10 phase increased the coercive force from 14.5 kA/m to 142 kA/m. The proposed method not only significantly accelerates the development of magnets using L10-FeNi but also offers a new synthesis route to obtain ordered alloys in non-equilibrium states.

DOI： 10.1038/s41598-017-13562-2

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2017 IOP Publishing Ltd. We measured critical currents and irreversibility fields of Ag-sheath (Sr, K)Fe2As2 tapes at various temperatures, magnetic fields and magnetic field directions. The sample tapes were made by a powder-in-tube with a hot-press process in the final heat treatments. The inverse anisotropy in J c in comparison with the effective mass anisotropy can be found in the hot-pressed (Sr, K)Fe2As2 tapes. We found that the broad c-axis peak in angular dependence of J c appears in a low field region and it decreases with increasing field and temperature. In addition, the crossover of J c anisotropy appears around 10 T at 4.2 K and the crossover field decreases with increasing temperature. It is considered that these unusual anisotropic J c behaviors may be originated by the strong random pinning center which is larger than the coherence length,

DOI： 10.1088/1361-6668/aa56fd

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2015 Elsevier B.V. All rights reserved. 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.

DOI： 10.1016/j.jallcom.2015.09.253

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2015 Elsevier B.V. All rights reserved. MgB2 is one of the "low activation superconductors", because the half-life of the induced radio-activity on the MgB2 is much shorter than that of Nb-based superconductors such as NbTi, Nb3Sn and Nb3Al. MgB2 wire would become an alternative material for Nb-Ti wire for the Poloidal Field and correction feedback coils, if the critical current density (Jc) around the magnetic field of 4 T could be improved. We found that addition of Cu using the compound Mg2Cu was an effective method to enhance Jc and succeed to fabricate 100 m length of MgB2 wire with Cu addition. Jc of the 100 m long MgB2 with Cu addition was comparable to that of a NbTi wire, and the small solenoid coil using Cu added MgB2 wire reached a central magnetic field of 2.62 T. We found that MgB2 wire is an alternative material to commercial NbTi wires under the hard neutron irradiation in a fusion reactor. Furthermore, we also fabricated a Cu added MgB2 wire using isotope pure boron-11 (11B) powder as the boron source to reduce the radioactivity. The critical temperature (Tc) of the MgB2 wire using 11B powder was found to be 37 K, and Tc was found to be changed by different boron materials.

DOI： 10.1016/j.fusengdes.2015.05.005

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2015 IEEE. Thin films of Bi-2223 fabricated on SrTiO3(100) substrates by dc sputtering were found to have a transition temperature (Tc) as low as that of bulk-phase Bi-2223. Subsequent annealing of these precursor films in the presence of Bi,Pb-2223 pellets increased this Tc value from 72 to 105 K, making it comparable to bulk-phase Bi,Pb-2223. Strong (00l) peaks and a sharp quadrupole were observed in this annealed film, indicating a main phase of Bi,Pb-2223 with a c-axis orientation by the X-ray diffractometry (XRD) measurements. A maximum critical current density (Jc) of 3.3 × 105 A/cm2 at 77 K was also obtained with the Bi,Pb-2223 thin film, which is a value that is much higher than that of commercial Bi,Pb-2223 tapes. Jc values of thin films were strongly dependent on the annealing temperatures between 854 °C and 866 °C. In this temperature range, XRD data show that the thin films were not a single phase of Bi,Pb-2223, suggesting only a slight interruption of the supercurrent. Although, the films have a good c-axis and ab-axis alignments. Thus, although the films were not perfect, the improvement in microstructure allows for a much higher Jc value.

DOI： 10.1109/TASC.2014.2376193

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2002-2011 IEEE. The uniform single phase Bi,Pb-2223 films are needed in order to acquire fundamental superconductivity data for the development of Bi,Pb-2223 wires. However, Bi,Pb-2223 films that we previously reported had the non-uniform microstructure containing several other phases. In this study we investigated the microstructural evolution during the heat treatment and processing route to fabricate uniform Bi,Pb-2223 films elucidated. An as-grown film had a small amount of Bi-2223 phase and a large amount of Ca-Sr-Cu-O phase. C-axes of some Bi-2223 crystals are not aligned along the normal direction of the STO substrate. In the primary stage of heat treatment, the formation of Bi,Pb-2223 phase proceeds. In the second stage of heat treatment, although the flat Cu-O layers in the Bi,Pb-2223 phase are formed by liquid-phase reactions, the grain coarsening of Ca-Sr-Cu-O phase also occurs. From the observation results, the fabrication process should be optimized based on the following points: uniform dispersion of penetration (diffusion) paths of Pb atoms into the film; short duration of heat treatment to avoid phase separation of Bi,Pb-2223 and coarsening of Ca-Sr-Cu-O phase.

DOI： 10.1109/TASC.2014.2382874

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2002-2011 IEEE. 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.

DOI： 10.1109/TASC.2014.2379928

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2014 IEEE. To investigate the effect of discontinuity of 1-D pinning centers on the flux pinning in a wide range of magnetic field directions, discontinuous columnar defects (CDs) and continuous CDs were formed in GdBCO coated conductors using Xe-ion irradiations with 80 and 270 MeV, respectively. An overall shift upward in Jc, for the 80-MeV-irradiated sample compared to the 270-MeV-irradiated one, can be observed in every direction of magnetic field, which is more remarkable as temperature decreases. This implies a synergetic effect of the pinning interaction between the linearity and the discontinuity for the discontinuous CDs. When the density of CDs is lower, however, the difference in Jc between the discontinuous and the continuous CDs becomes less at lower temperature, even in the magnetic field parallel to the c-axis. At lower density of CDs, the average spacing between CDs is wider, which would hardly lead to automatic entanglement of flux lines in the discontinuous CDs, i.e., to the synergetic effect.

DOI： 10.1109/TASC.2014.2374554

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A comprehensive study of the effects of structural imperfections in MgB2 super-conducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB2 material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the pi and sigma bands of MgB2, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB2, however, even at low sintering temperature, and thus block current transport paths. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

DOI： 10.1063/1.4862670

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

In previous studies, the secondary (impurity and non-reactive) phase and voids were observed in MgB2 matrix after the heat treatment, and then these are the lowering factors of critical current density (J(c)) property. In order to improve J(c) property by microstructure control of MgB2 matrix, the fine elemental boron powder as the raw material was carried out using the high-speed vibrated milling with tungsten carbide (WC) jar. The average particle size of metal boron powder was decreased from 1.14 mu m to 0.20 mu m by the high-speed vibrated milling. The various fine particle boron powders as the function of milling time were also prepared, and in-situ Cu addition MgB2 multifilamentary wires using these fine boron powders were fabricated. Critical transition temperature (T-c) value of Cu addition MgB2 wire using fine boron powder obtained to about 37 K. No change of the T-c property by the different particle sized boron powders was confirmed. In this paper, the comparisons of microstructure and superconducting properties between the different boron particle sizes were investigated.

DOI： 10.1088/1742-6596/507/2/022009

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10853-012-6901-5

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

In order to study the mechanism of phase transformation from Bi-2212 to Bi-2223, we fabricated Pb-Ca-Cu deposited Bi-2212 (001) single crystals as precursors of the Bi,Pb-2223 phase. These single crystals were heated in a sintered Bi-Pb-Sr-Ca-Cu-O pellet, and microstructure was observed by analytical electron microscopy. As a result of the microstructural observation around the Bi,Pb-2223 phase, two formation paths of Bi, Pb-2223 were recognized. One is the formation from a liquid phase which is formed by Bi-2212 and melting of the secondary phases such as (Ca,Sr)(2)PbO4 and CuO. The other is the growth of Bi,Pb-2223 into Bi-2212 phase by diffusion of Pb, Ca and Cu atoms along the < hk0 > directions of Bi-2212. (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2013.04.054

記述言語：日本語  

Fabrication of (Bi,Pb)2223 Films by a DC Magnetron Sputtering Method

DOI： 10.2221/jcsj.48.95

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The metal Al is lighter in weight than other substrate materials for MgB2 films such as Si and Ni. This property inspires MgB2 fabrication on a large-scale Al substrate as a new route to MgB2 tapes. Here we report microstructural factors influencing critical current density, J(c), in MgB2/Al films. MgB2/Al films were prepared by the following steps: deposit a boron layer of 3 nm in thickness on an Al substrate heated at 280 degrees C; deposit Mg and boron on the boron layer (sample A). For comparison, Mg and boron were deposited directly on an Al substrate heated at 265 degrees C (sample B). The microstructure was observed by transmission electron microscopy (TEM) and scanning TEM. J(c) values at 20 K in the self-field were 4.9 x 10(6) A cm(-2) for sample A and 2.7 x 10(6) A cm(-2) for sample B. Both the samples form an oxygen-rich layer of 10 nm in thickness at the substrate surface. This oxygen-rich layer may suppress Al diffusion into MgB2 lattices. The [001] texture of columnar MgB2 crystals grown on the substrate is stronger in sample A than in sample B. This indicates that the boron layer deposition on the Al substrate is effective for fabricating well-textured MgB2 polycrystals, resulting in the higher J(c) enhancement for sample A.

DOI： 10.1109/TASC.2013.2238284

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Increasing dissipation-free supercurrent has been the primary issue for practical application of superconducting wires. For magnesium diboride, MgB2, carbon is known to be the most effective dopant to enhance high-field properties. However, the critical role of carbon remains elusive, and also low-field critical current density has not been improved. Here, we have undertaken malic acid doping of MgB2 and find that the microscopic origin for the enhancement of high-field properties is due to boron vacancies and associated stacking faults, as observed by high-resolution transmission electron microscopy and electron energy loss spectroscopy. The carbon from the malic acid almost uniformly encapsulates boron, preventing boron agglomeration and reducing porosity, as observed by three-dimensional X-ray tomography. The critical current density either exceeds or matches that of niobium titanium at 4.2 K. Our findings provide atomic-level insights, which could pave the way to further enhancement of the critical current density of MgB2 up to the theoretical limit. NPG Asia Materials (2012) 4, e3; doi:10.1038/am.2012.3; published online 18 January 2012

DOI： 10.1038/am.2012.3

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.physc.2011.05.143

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Several reaction-induced diffusion processes to fabricate high-density MgB2 materials are developed, and the critical current density (J(c)) has been notably enhanced. In this study, microstructure in high-density MgB2 wires fabricated by an internal Mg diffusion (IMD) process has been investigated. The inner reacted region of the wire heat-treated at 640 degrees C for 1 h shows dense polycrystalline MgB2 of 20-200 nm in grain sizes. Fine MgO and Mg2Si particles of 10-30 nm in sizes are dispersed in this region. On the other hand, the outer region near the Ta sheath is composed of unreacted B and SiC powders, fine MgO particles and small voids. Sizes of voids in the IMD MgB2 wire are small compared with the PIT MgB2 wire. Oxidation of Mg in the IMD process forms fine dispersion of MgO which may be effective for flux pinning.

DOI： 10.1109/TASC.2010.2091097

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Microstructure in MgB2/Ni Alternately-Layered Superconducting Film

記述言語：日本語  

We report relationships between the superconducting properties, microstructure and fabrication conditions in high-density MgB₂ bulks fabricated using a premix-powder-in-closed-tube (PICT) method. The microstructure of the MgB₂ bulks depends on the crystallinity of the initial B powders; use of crystalline B powders reduces the amount of MgB₂ and increases re-sidual B and MgO. The heat treatment condition influences the grain sizes of MgB₂ as well as the distribution and grain sizes of MgO. A lower temperature and a shorter duration of heat treatment tend to form fine grains of MgB₂ and uniform dispersion of fine MgO particles. These microstructural variations influence the distribution of effective flux pinning centers such as grain boundaries and fine MgO particles. Different types of critical current density behavior as a function of magnetic field were meas-ured.

DOI： 10.2221/jcsj.44.613

開催年月日： 2021年3月

記述言語：日本語  

国名：その他  

開催年月日： 2021年3月

記述言語：日本語  

国名：その他  

開催年月日： 2020年10月 - 2020年11月

記述言語：英語  

国名：その他  

開催年月日： 2020年9月

記述言語：英語  

国名：その他  

開催年月日： 2020年9月

記述言語：日本語  

国名：その他  

開催年月日： 2019年9月

記述言語：日本語  

国名：その他  

開催年月日： 2019年6月

記述言語：日本語  

国名：その他  

開催年月日： 2019年5月

記述言語：日本語  

国名：その他  

記述言語：その他  

開催地：日本国 Himeji   国名：その他  

Effectiveness of multi-scale observations for polycrystalline superconducting materials

記述言語：その他  

開催地：日本国 仙台   国名：その他  

多結晶超伝導材料の臨界電流特性と結晶粒構造

記述言語：その他  

開催地：日本国 Kyoto   国名：その他  

Influence of synthesis condition on grain structure of Ba(Fe,Co)2As2 polycrystalline bulks

記述言語：その他  

開催地：日本国   国名：その他  

ヒーター式加熱炉型ホルダーによる原子分解能その場観察

記述言語：その他  

開催地：韓国 Jeju   国名：その他  

Multi-scale interstructure of Mg2Cu addition MgB2 policrystalline wire

記述言語：その他  

開催地：日本国 札幌   国名：その他  

ヒーター式加熱による原子分解能その場加熱観察

記述言語：日本語  

国名：その他  

記述言語：日本語  

国名：その他  

記述言語：英語  

国名：その他  

Development of double-tilt heating holder for dynamical/atomic resolution AC-TEM and WB-STEM observations of ferromagnetic ferrous alloys

記述言語：日本語  

国名：その他  

記述言語：日本語  

国名：その他  

記述言語：英語  

国名：その他  

記述言語：日本語  

国名：その他  

記述言語：日本語   会議種別：口頭発表（一般）  

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

記述言語：日本語  

積層前駆体膜から作製したBi,Pb‐2223超伝導薄膜の超伝導特性

記述言語：日本語  

記述言語：日本語  

積層前駆体膜を用いたBi,Pb‐2223超伝導薄膜

記述言語：日本語  

記述言語：日本語  

Mg₂Cu添加in‐situ MgB₂線材の微細組織におけるB/Mg比と原料粉末の影響

記述言語：日本語  

記述言語：日本語  

Microstructural Evolution of Bi,Pb-2223 Films During Heat-Treatment

記述言語：日本語  

記述言語：日本語  

スパッタ法により作製したBi,Pb‐2223薄膜の微細組織と熱処理条件の関係

記述言語：日本語  

記述言語：日本語  

3Dによる微細構造解析技術の展望と構造材料への応用

記述言語：日本語  

記述言語：日本語  

電子ビーム蒸着法により作製したMgB₂/Al薄膜の微細組織観察

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

SmBa₂Cu₃O_y超伝導線材における結晶配向の局所変化と微細組織の関係

記述言語：日本語  

EDDC法により作製したSmBa₂Cu₃O_y高温超伝導線材の局所微細構造解析

記述言語：日本語  

記述言語：日本語  

Mg₂Cuを添加源としたCu添加MgB₂超伝導線材の低温熱処理生成挙動

記述言語：日本語  

記述言語：日本語  

X線CTによるMgB₂線材の組織観察

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

Alテープ上に作製したMgB₂薄膜の微細組織構造

記述言語：日本語  

Mg₂Cuを添加源としたCu添加MgB₂線材の微細構造

記述言語：日本語  

X線CTによるMgB₂超伝導線材の組織観察の試み

記述言語：日本語  

記述言語：日本語  

内部Mg拡散MgB₂線材のマクロ組織に及ぼす熱処理条件の影響

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

Alテープ上へのMgB₂薄膜の作製と特性評価

記述言語：日本語  

内部Mg拡散法により作製したMgB₂線材の微細組織構造

記述言語：日本語  

記述言語：日本語  

多結晶MgB₂超伝導バルク体の結晶方位分布解析

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

MgB₂超伝導薄膜の臨界電流特性と微細組織制御

記述言語：日本語  

MgB₂超伝導線材のin‐situ作製プロセスにおける微細組織形成の観察

記述言語：日本語  

記述言語：日本語  

Premix‐PICT拡散法で作製したMgB₂バルク体のJ_c特性と微細組織

記述言語：日本語  

記述言語：日本語  

PICT拡散法で作製したMgB₂超伝導バルク体の微細組織観察

記述言語：日本語  

記述言語：日本語  

in‐situ MgB₂線材の熱処理過程の組織観察

記述言語：日本語