| 1. |
Yusuke Shimada, Akiyasu Yamamoto, Yujiro Hayashi, Kohji Kishio, Jun-ichi Shimoyama, Satoshi Hata, Toyohiko J. Konno, The formation of defects and their influence on inter- and intra-granular current in sintered polycrystalline 122 phase Fe-based superconductors, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 10.1088/1361-6668/ab0eb6, Vol.32, No.8, 2019.08, 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.. |
| 2. |
Solid Solution Hardening in Supersaturated Al-Mg-Si Alloy
The yield strength and work hardening of Al-Mg-Si alloys are related to the concentration of solute atoms. This study was carried out to clarify the effect of two kinds of solute atoms on these properties in terms of a linear combination of contributions from a solid solution. Tensile tests were conducted with Al and with Al-0.62Mg-0.32Si, Al-0.65Mg-0.81Si, Al-2.4Mg and Al-4.4Mg (mass%) alloys in solid solution. Work hardening was analysed using the Kocks–Mecking model, yielding two parameters which indicate the storage and recovery of dislocations in the material. The yield strength could not be expressed as a linear combination of solute atom concentrations, but the amount of dislocation storage and dynamic recovery could be expressed as such linear combinations. In the high-strain region, the Kocks–Mecking model no longer applies, and the maximum stress at which the model failed increased with increasing concentrations of solute atoms. It is generally known that an interaction between strain fields around solute atoms and quenched-in vacancies can affect the yield strength owing to dislocation motion and that these atoms can retard the development of microstructure in high-strain regions. A linear combination of contributions from solid solutions is possible only for the storage and recovery of dislocations in the low-strain region. . |
| 3. |
Kana L. Hasezaki, Hikaru Saito, Takumi Sannomiya, Hiroya Miyazaki, Takashi Gondo, Shinsuke Miyazaki, Satoshi Hata, Three-dimensional visualization of dislocations in a ferromagnetic material by magnetic-field-free electron tomography, ULTRAMICROSCOPY, 10.1016/j.ultramic.2017.07.016, Vol.182, pp.249-257, 2017.11, In conventional transmission electron microscopy, specimens to be observed are placed in between the objective lens pole piece and therefore exposed to a strong magnetic field about 2 T. For a ferromagnetic specimen, magnetization of the specimen causes isotropic and anisotropic defocusing, deflection of the electron beam as well as deformation of the specimen, which all become more severe when the specimen tilted. Therefore electron tomography on a ferromagnetic crystalline specimen is highly challenging because tilt-series data sets must be acquired without changing the excitation condition of a specific diffraction spot. In this study, a scanning transmission electron microscopy (STEM) tomography method without magnetizing a ferromagnetic specimen has been developed for three-dimensional (3D) visualization of dislocations in alpha-Fe, which is a typical ferromagnetic material. Magnetic-field-free environment down to 0.38 +/- 0.07 mT at the specimen position is realized by demagnetizing the objective lens pole piece of a commercial STEM instrument. By using a spherical aberration corrector with the magnetic-field-free environment, an "aberration corrected Low-Mag STEM mode" with no objective lens field reaches a convergence semi angle similar to 1 mrad and a spatial resolution similar to 5 nm, and shows an adequate performance of imaging dislocations under a two-beam excitation condition for a low-index diffracted beam. The illumination condition for the aberration corrected Low-Mag STEM mode gives no overlap between the direct beam disk (spot) and neighboring diffraction disks. An electron channeling contrast imaging technique, in which an annular detector was located at a doughnut area between the direct beam and the neighboring diffracted beams, was effectively employed with the aberration corrected Low-Mag STEM mode to keep image intensity high enough even at large specimen-tilt angles. The resultant tomographic observation visualized 3D dislocation arrangements and active slip planes in a deformed alpha-Fe specimen. (C) 2017 Elsevier B.V. All rights reserved.. |
| 4. |
Wan-song Li, Hong-ye Gao, Hideharu Nakashima, Satoshi Hata, Wen-huai Tian, In-situ EBSD study of deformation behavior of retained austenite in a low-carbon quenching and partitioning steel via uniaxial tensile tests, MATERIALS CHARACTERIZATION, 10.1016/j.matchar.2016.06.020, Vol.118, pp.431-437, 2016.08, Through using in-situ electron back-scattered diffraction and uniaxial tensile tests, this work mainly focuses on the deformation behavior of retained austenite (RA) in a low-carbon quenching and partitioning (Q&P) steel. In this paper, three different types of RA can be distinguished from different locations, respectively, RA grains at the triple edges, twinned austenite and RA grains positioned between martensite. The results have shown that grains at the triple edges and twinned austenite could transform easily with increasing strain, i.e. are less stable when compared with RA grains distributed between martensite that could resist a larger plastic deformation. Meanwhile, the strain leads to rotations of RA grains distributed at the triple edges and between martensite. Moreover, RA grains with a similar orientation undergone similar rotations with the same true strain. These RA grains rotated along a specific slip plane and slip direction and the grain rotation is taken as a significant factor to improve the ductility of steel. In addition, grain sizes of RA decreased gradually with an increase of true strain and smaller (0-02 mu m) grains were more capable of resisting the deformation. According to kernel average mis-orientation (KAM) analysis, it can be found that strain distribution is preferentially localized near martensite-austenite phase boundaries and in the interior of martensite. The average KAM values increased continuously with increasing true strain. (C) 2016 Elsevier Inc. All rights reserved.. |
| 5. |
Wan-song Li, Hong-ye Gao, Hideharu Nakashima, Satoshi Hata, Wen-huai Tian, Microstructural evolution and mechanical properties of a low-carbon quenching and partitioning steel after partial and full austenitization, INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS, 10.1007/s12613-016-1306-0, Vol.23, No.8, pp.906-919, 2016.08, In this work, low-carbon steel specimens were subjected to the quenching and partitioning process after being partially or fully austenitized to investigate their microstructural evolution and mechanical properties. According to the results of scanning electron microscopy and transmission electron microscopy observations, X-ray diffraction analysis, and tensile tests, upper bainite or tempered martensite appears successively in the microstructure with increasing austenitization temperature or increasing partitioning time. In the partially austenitized specimens, the retained austenite grains are carbon-enriched twice during the heat treatment, which can significantly stabilize the phases at room temperature. Furthermore, after partial austenitization, the specimen exhibits excellent elongation, with a maximum elongation of 37.1%. By contrast, after full austenitization, the specimens exhibit good ultimate tensile strength and high yield strength. In the case of a specimen with a yield strength of 969 MPa, the maximum value of the ultimate tensile strength reaches 1222 MPa. During the partitioning process, carbon partitioning and carbon homogenization within austenite affect interface migration. In addition, the volume fraction and grain size of retained austenite observed in the final microstructure will also be affected.. |
| 6. |
Chanmin Lee, Yukwon Jeon, Satoshi Hata, Joo-Il Park, Ryutaro Akiyoshi, Hikaru Saito, Yasutake Teraoka, Yong-Gun Shul, Hisahiro Einaga, Three-dimensional arrangements of perovskite-type oxide nano-fiber webs for effective soot oxidation, APPLIED CATALYSIS B-ENVIRONMENTAL, 10.1016/j.apcatb.2016.03.001, Vol.191, pp.157-164, 2016.08, Perovskite-type oxides have been widely applied in heterogeneous catalytic reactions, such as soot oxidation. However, a poor contact point between the catalyst and solid reactant (soot) often limits the catalytic performance. Here, we report La1-xSrxCo0.2Fe0.8O3-delta perovskite oxide catalysts with a unique three-dimensional (3D) fiber web structure that increases the high-contact area by trapping soot in the unique pore structure for effective catalytic activity. This feature was carefully analyzed using scanning transmission electron microscopy (STEM) tomography to investigate the location of the soot on the web. The structure of the web, with a thickness of approximately 55 mu m, indicated that the soot particles were caught by the 3D pores between the fibers. The relationship between the Sr amount and activate oxygen was also characterized by means of XPS. The results show that the Sr amount of 0.4 produced the highest amount of active oxygen species (O-) that are essential for soot oxidation reaction. The developed catalyst exhibited a good catalytic performance due to the optimized perovskite chemical structure and the greatly increased number of the contact points owing to the 3D inter-fiber spaces. Hence, our proposed approach is reasonable for application to real soot combustion processes and can also be easily extended to numerous other catalytic processes to enhance the catalytic activity. (C) 2016 Elsevier B.V. All rights reserved.. |
| 7. |
Jun-jie Shen, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Primary-transient creep and anelastic backflow of pure copper deformed at low temperatures and ultra-low strain rates, TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA, 10.1016/S1003-6326(16)64285-1, Vol.26, No.7, pp.1729-1735, 2016.07, Creep and anelastic backflow behaviors of pure copper (4N Cu) with grain size d(g) = 40 mu m were investigated at low temperatures of T |
| 8. |
Jesbains Kaur, Noriyuki Kuwano, Khairur Rijal Jamaludin, Masatoshi Mitsuhara, Hikaru Saito, Satoshi Hata, Shuhei Suzuki, Hideto Miyake, Kazumasa Hiramatsu, Hiroyuki Fukuyama, Electron microscopy analysis of microstructure of postannealed aluminum nitride template, APPLIED PHYSICS EXPRESS, 10.7567/APEX.9.065502, Vol.9, No.6, 2016.06, The microstructure of an AlN template after high-temperature annealing was investigated by transmission electron microscopy (TEM). The AlN template was prepared by depositing an AlN layer of about 200nm thickness on a sapphire (0001) substrate by metal-organic vapor phase epitaxy. The AlN template was annealed under (N-2 + CO) atmosphere at 1500-1650 degrees C. TEM characterization was conducted to investigate the microstructural evolution, revealing that the postannealed AlN has a two-layer structure, the upper and lower layers of which exhibit Al and N polarities, respectively. It has been confirmed that postannealing is an effective treatment for controlling the microstructure. (C) 2016 The Japan Society of Applied Physics. |
| 9. |
K. Jesbains, N. Kuwano, K. R. Jamaludin, H. Miyake, K. Hiramatsu, S. Suzuki, M. Mitsuhara, S. Hata, Y. Soejima, Reduction of dislocation density of aluminium nitride buffer layer grown on sapphire substrate, Journal of Mechanical Engineering and Sciences, 10.15282/jmes.10.1.2016.14.0182, Vol.10, No.1, pp.1908-1916, 2016.06, An aluminium nitride (AlN) buffer layer with 200 nm thickness was grown on (0001) sapphire substrate using the metal-organic vapour phase epitaxy (MOVPE) method in a low-pressure furnace, followed by a clean-up treatment of sapphire substrate at 1100°C. Thereafter, the AlN buffer layer was annealed at a high temperature in the range of 1500°C to 1700°C for 2 hours under the atmosphere of N2+CO. The objective of this research is to determine the microstructure changes with different annealing temperatures. Cross-sectional TEM has revealed that, after annealing at 1500°C, two types of defects remained in the AlN buffer layer: inverted cone shape domains and threading dislocations. The former domains were observed in an image taken with diffraction of g=0002, but not in an image with g=1010. The morphology and the diffraction condition for the image contrast strongly, suggesting that the domains are inversion domains. The threading dislocations were invisible in the image taken with the diffraction of g=0002, revealing that they were a-Type dislocations. However, after annealing at 1600oC, the inversion domains coalesced with each other to give a two-layer structure divided by a single inversion domain boundary at the centre of the AlN buffer layer. The density of threading dislocation was roughly estimated to be 5×109 cm-2 after annealing at 1500°C, and to be reduced to 5×108 cm-2 after annealing at 1600°C. These experimental results validate the fact that the annealing temperature around 1600°C is high enough to remove the defects by the diffusion process. Therefore, it was discovered that high temperature annealing is an effective treatment to alter the microstructure of AlN thin films and remove defects by the diffusion process. Annealing at high temperature is recommended to increase the emission efficiency for fabrication of optoelectronic devices.. |
| 10. |
Wan-song Li, Hong-ye Gao, Zhong-yi Li, Hideharu Nakashima, Satoshi Hata, Wen-huai Tian, Effect of lower bainite/martensite/retained austenite triplex microstructure on the mechanical properties of a low-carbon steel with quenching and partitioning process, INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS, 10.1007/s12613-016-1239-7, Vol.23, No.3, pp.303-313, 2016.03, We present a study concerning Fe-0.176C-1.31Si-1.58Mn-0.26Al-0.3Cr (wt%) steel subjected to a quenching and partitioning (Q&P) process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demonstrate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite (LB), and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstructure, three types of retained austenite with different sizes and morphologies were observed: blocky retained austenite (similar to 300 nm in width), film-like retained austenite (80-120 nm in width), and ultra- fine film-like retained austenite (30-40 nm in width). Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q&P steel.. |
| 11. |
Sumiha Ikeshita, Ansis Strodahs, Zineb Saghi, Kazuhiro Yamada, Pierre Burdet, Satoshi Hata, Ken-ichi Ikeda, Paul A. Midgley, Kenji Kaneko, Hardness and microstructural variation of Al-Mg-Mn-Sc-Zr alloy, MICRON, 10.1016/j.micron.2015.12.002, Vol.82, pp.1-8, 2016.03, Variations of Vickers hardness were observed in Al-Mg-Mn alloy and Al-Mg-Mn-Sc-Zr alloy at different ageing times, ranging from a peak value of 81.2 HV at 54 ks down to 67.4 HV at 360 ks, below the initial hardness value, 71.8 HV at 0 ks for the case of Al-Mg-Mn-Sc-Zr alloy. Microstructures of samples at each ageing stage were examined carefully by transmission electron microscopes (TEMs) both in two-dimensions and three-dimensions. The presence of different types, densities, and sizes of particles were observed dispersed spherical Al3Sc1-xZrx and also block-shaped Al3Sc precipitates growing along (Al) with facets {1 0 0} and {1 1 0} of the precipitates. TEM analysis both in two-dimensions and three-dimensions, performed on various samples, confirmed the direct correlation between the hardness and the density of Al3Sc. (C) 2015 Elsevier Ltd. All rights reserved.. |
| 12. |
Hisahiro Einaga, Ryo Shiranita, Hikaru Saito, Satoshi Hata, Codeposition of Colloidal Platinum Particles and Iron Chloride Precursor on TiO2 for Efficient Catalytic Oxidation of CO to CO2, CHEMISTRY LETTERS, 10.1246/cl.150903, Vol.44, No.12, pp.1786-1788, 2015.12, Codeposition of metal chlorides with Pt colloidal nanoparticles on TiO2 followed by oxidation at 400 degrees C and reduction at 200 degrees C improved the activity for Pt-catalyzed CO oxidation with stoichiometric amount of O-2. The highest activity was obtained when FeCl3 was used as the additive with the Fe/Pt ratio of 0.2. XAFS, X-EDS, FTIR, and catalytic studies revealed that the deposition of Fe species on the reduced Pt sites gave active sites, which exhibited CO oxidation with high efficiency.. |
| 13. |
Yoshimitsu Hishinuma, Akihiro Kikuchi, Yusuke Shimada, Taro Kashiwai, Satoshi Hata, Shuichi Yamada, Takeo Muroga, Akio Sagara, Development of MgB2 superconducting wire for the low activation superconducting magnet system operated around core D-T plasma, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2015.05.005, Vol.98-99, pp.1076-1080, 2015.10, 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 (J(c)) around the magnetic field of 4T could be improved. We found that addition of Cu using the compound Mg2Cu was an effective method to enhancek 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 2.62T. 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 (B-11) powder as the boron source to reduce the radioactivity. The critical temperature (T-c) of the MgB2 wire using B-11 powder was found to be 37K, and T-c was found to be changed by different boron materials. (C) 2015 Published by Elsevier B.V.. |
| 14. |
K. Sato, H. Miyazaki, T. Gondo, S. Miyazaki, M. Murayama, S. Hata, Development of a novel straining holder for transmission electron microscopy compatible with single tilt-axis electron tomography, MICROSCOPY, 10.1093/jmicro/dfv021, Vol.64, No.5, pp.369-375, 2015.10, We have developed a newly designed straining specimen holder for in situ transmission electron microscopy (TEM) compatible with high-angle single tilt-axis electron tomography. The holder can deform a TEM specimen under tensile stress with the strain rate between 1.5 x 10(-6) and 5.2 x 10(-3) s(-1). We have also confirmed that the maximum tilt angle of the specimen holder reaches +/- 60 degrees with a rectangular shape aluminum specimen. The new specimen holder, termed as 'straining and tomography holder', will have wide range potential applications in materials science.. |
| 15. |
Improvement of Strength and Elongation Balance of Al-Mg-Si Alloy Utilizing Mg-Si Cluster and Its Mechanism
Tensile properties of Al-Mg-Si alloy with Mg-Si clusters was compared with that with beta" precipitate with the same strength. It was found that the elongation of the alloy with Mg-Si cluster was greater than the alloy with beta" precipitate because of high work hardening rate, in particular at large strain region. Decomposition of Mg-Si cluster into solute Mg and Si atoms during the tensile deformation test were also shown by differential scanning calorimetry (DSC). Three types of dislocation characteristics were observed from these alloys by transmission electron microscopy (TEM), homogeneous distribution of dislocation with beta" precipitate, cell structure with Mg and Si in solid solution, and combination of them with Mg-Si cluster. For the case of alloy with Mg-Si cluster, the yield strength was significantly increased due to the cutting mechanism. Simultaneously, the elongation was greatly improved due to the presences of decomposed solute Mg and Si atoms with plastic strain, which are inferred to prevent dynamic recovery in the later stage of tensile test. Consequently, the alloy with clusters has advantages from both alloys with precipitates and solutes, in terms of strength and elongation balance among the conventional 6000 series and 7000 series Al alloys.. |
| 16. |
A. Matsumoto, H. Kitaguchi, T. Doi, T. Izumi, Y. Hakuraku, Y. Shimada, S. Hata, Effect of Annealing DC-Sputtered Bi,Pb-2223 Thin Films, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2014.2376193, Vol.25, No.3, 2015.06, Thin films of Bi-2223 fabricated on SrTiO3(100) substrates by dc sputtering were found to have a transition temperature (T-c) 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 T-c 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 (J(c)) of 3.3 x 10(5) A/cm(2) 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 Iii,Pb-2223 tapes. J(c) values of thin films were strongly dependent on the annealing temperatures between 854 degrees C and 866 degrees 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 J(c) value.. |
| 17. |
Yusuke Shimada, Satoshi Hata, Ken-ichi Ikeda, 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, Vol.25, No.3, 2015.06, 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.. |
| 18. |
Yusuke Shimada, Takato Kajihara, Satoshi Hata, Ken-ichi Ikeda, Hideharu Nakashima, Akiyoshi Matsumoto, Hitoshi Kitaguchi, Toshiya Doi, Microstructural Studies of the Effect of Heat-Treatment on Bi,Pb-2223 Films Prepared by RF Sputtering, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2014.2382874, Vol.25, No.3, 2015.06, 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.. |
| 19. |
J. Wang, S. Hata, Y. K. Takahashi, H. Sepehri-Amin, B. S. D. Ch. S. Varaprasad, T. Shiroyama, T. Schrefl, K. Hono, Effect of MgO underlayer misorientation on the texture and magnetic property of FePt-C granular film, ACTA MATERIALIA, 10.1016/j.actamat.2015.03.007, Vol.91, pp.41-49, 2015.06, A transmission electron microscope (TEM) based orientation mapping technique and micromagnetic simulations were applied to study the influence of easy axis distribution (EAD) on magnetic properties of FePt-C granular films which were deposited on a single crystalline MgO (0 0 1) substrate and a (0 0 1)-textured poly-crystalline MgO underlayer. The FePt-C film on the polycrystalline MgO underlayer shows smaller perpendicular coercivity, broader switching field distribution and visible in-plane minor loop compared with that deposited on the single crystalline MgO (0 0 1) substrate. Although the grain sizes and their distributions in both films look similar in TEM, orientation mapping and texture analysis revealed that the polycrystalline MgO underlayer introduces significant misorientation in the (0 0 1)-textured FePt grains. Micromagnetic simulations successfully reproduced the large hysteresis in the in-plane magnetization by introducing the specific misorientation distribution of the FePt grains obtained from the texture analysis. The misoriented FePt grains were found to be grown from misoriented MgO grains, indicating that the improvement of the (0 0 1) texture of the MgO underlayer is essential to reduce the in-plane component of FePt based recording media. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.. |
| 20. |
R. G. Abhilash Kumar, Satoshi Hata, Ken-ichi Ikeda, K. G. Gopchandran, Luminescence dynamics and concentration quenching in Gd2-xEuxO3 nanophosphor, CERAMICS INTERNATIONAL, 10.1016/j.ceramint.2015.01.051, Vol.41, No.4, pp.6037-6050, 2015.05, Gd2-xEuxO3 nanophosphor with enhanced luminescence has been synthesized by solution combustion method in diethylene glycol medium. The effect of Eu3+ content on the structure, morphology and luminescence dynamics has been investigated. The observed red shift in charge transfer band of the nanophosphor with increase in Eu3+ content is attributed to the increase in covalency and Eu-O bond length. Excess europium content leads to reduction in intensity of photoemission as a result of concentration quenching. Transient characteristics exhibit single exponential behaviour and the fitted life time values get shortened with increase of Eu3+ content, due to increase in non-radiative transition rate. The observed quenching of luminescence in the phosphor is found to be in agreement with the energy transfer theory proposed by Dexter and Schulman and found that dipole dipole interaction between Eu3+ ions is the key mechanism responsible for quenching. Critical energy transfer distance between Eu3+ ions in Gd2-xEuxO3 is determined to be 1.148 nm. Judd-Ofelt intensity parameters and the radiative parameters of the phosphors were evaluated from the emission spectrum to analyse the crystal field environment and the degree of covalency between the rare-earth ion and the surrounding ligands. The value of Omega(2) intensity parameter confirmed the hypersensitive nature of the D-5(0)-F-7(2) transition with larger asymmetry around Eu3+ ions. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.. |
| 21. |
Masaharu Tsuji, Koichi Takemura, Chihiro Shiraishi, Koji Ikedo, Keiko Uto, Atsuhiko Yajima, Masashi Hattori, Yukinori Nakashima, Kento Fukutomi, Kunihiko Tsuruda, Takeshi Daio, Takeshi Tsuji, Satoshi Hata, Syntheses of Au@PdAg and Au@PdAg@Ag Core-Shell Nanorods through Distortion-Induced Alloying between Pd Shells and Ag Atoms over Au Nanorods, JOURNAL OF PHYSICAL CHEMISTRY C, 10.1021/jp509340s, Vol.119, No.20, pp.10811-10823, 2015.05, Noble Au@PdAg and Au@PdAg@Ag core-shell nanorods (NRs) having PdAg alloy shells were synthesized using Au@Pd NRs as seeds. Their crystal structures and growth mechanisms were examined using data from TEM, TEM-EDS, XRD, and UV- Vis-NIR extinction spectroscopy. First, cuboid or dumbbell-type Au@Pd NR seeds were prepared using Au@Pd NRs as seeds. In the second step, when Ag+ ions were reduced over these seeds, cuboid and dumbbell-type Au core PdAg alloy shell NRs were formed with maximum Ag content of about 16% and 24%, respectively, after heating at 60 degrees C. The driving force of alloying between Pd shells and Ag atoms was attributed to the distortion of Pd layers over Au NRs based on peak shifts and broadening of XRD data. The higher Ag content in dumbbell-type Au@PdAg NRs was explained by the greater distortion of Pd shells over Au NRs. When the Ag content exceeds its maximum solubility in Pd shells, the third Ag shells were grown over Au@PdAg NRs. For cuboid Au@PdAg NRs, the crystal growth of Ag shells over cuboid Au@PdAg cores begins with the formation of single nuclei on a wide side PdAg alloy facet, followed by growth to one cuboid rod shell and further growth of one or two neighboring cuboid rod shells having {100} facets. On the other hand, for dumbbell-type Au@Pd NRs, Ag shells were deposited over concave curvature of the side facets of Au@PdAg and cuboid Au@PdAg@Ag NRs having one large cuboid Ag block was finally formed in each particle. Our study provides a new simple technique for the epitaxial growth of uniform PdAg alloy layers using spontaneous alloying between Pd shells and Ag atoms over Au NRs.. |
| 22. |
Yoji Miyajima, Shin-ya Komatsu, Masatoshi Mitsuhara, Satoshi Hata, Hideharu Nakashima, Nobuhiro Tsuji, Microstructural change due to isochronal annealing in severely plastic-deformed commercial purity aluminium, PHILOSOPHICAL MAGAZINE, 10.1080/14786435.2015.1021400, Vol.95, No.11, pp.1139-1149, 2015.04, Microstructural changes, such as the density of grain boundary (GB) and dislocation density, due to isochronal annealing in severely plastic-deformed commercial purity aluminium up to 523K was evaluated using electrical resistivity measurements and scanning transmission electron microscopy. Eventually, the GB density decreases from about 7.2 x 10(6) to about 2 x 10(6)m(-1), whilst the dislocation density decreases from an initial value of around 1.3 x 10(14)m(-2) down to around 4 x 10(13)m(-2).. |
| 23. |
Aira Matsugaki, Gento Aramoto, Takafumi Ninomiya, Hiroshi Sawada, Satoshi Hata, Takayoshi Nakano, Abnormal arrangement of a collagen/apatite extracellular matrix orthogonal to osteoblast alignment is constructed by a nanoscale periodic surface structure, BIOMATERIALS, 10.1016/j.biomaterials.2014.10.025, Vol.37, pp.134-143, 2015.01, Morphological and directional alteration of cells is essential for structurally appropriate construction of tissues and organs. In particular, osteoblast alignment is crucial for the realization of anisotropic bone tissue microstructure. In this article, the orientation of a collagen/apatite extracellular matrix (ECM) was established by controlling osteoblast alignment using a surface geometry with nanometer-sized periodicity induced by laser ablation. Laser irradiation induced self-organized periodic structures (laser-induced periodic surface structures; LIPSS) with a spatial period equal to the wavelength of the incident laser on the surface of biomedical alloys of Ti-6Al-4V and Co-Cr-Mo. Osteoblast orientation was successfully induced parallel to the grating structure. Notably, both the fibrous orientation of the secreted collagen matrix and the c-axis of the produced apatite crystals were orientated orthogonal to the cell direction. To the best of our knowledge, this is the first report demonstrating that bone tissue anisotropy is controllable, including the characteristic organization of a collagen/apatite composite orthogonal to the osteoblast orientation, by controlling the cell alignment using periodic surface geometry. (C) 2014 Elsevier Ltd. All rights reserved.. |
| 24. |
Simulations of TDGL equations for B2 type ordering with two-step phase separation in Fe-Ni-Al alloys
The present authors recently developed a time-dependent Ginzburg-Landau (TDGL) formulation for ordering processes of B2 and D03 in binary alloys, taking into account the symmetrical relationships between these ordered phases. Kinetic equations for time-evolution of order parameters and the composition one are derived from the Ginzburg-Landau type potential consisting of a mean-field free energies and interfacial energy terms. On the other hand, coauthors have investigated domain structures in two-step phase separation of Fe-based Fe-Ni-Al alloys. Micro-structures in the superalloys consist of B2 ordered domains and A2 disordered matrices in the first stage of phase separation. The second stage during a subsequent aging leads to formation of B2 domains and A2 phase regions in the former A2 matrices and B2 domains, respectively. The evolution of three-dimensional domain structures and composition profiles has been analyzed by electron tomography imaging and energy-dispersive X-ray spectroscopy. In this work the authors have applied the TDGL formulation to this alloy system, and performed three-dimensional numerical simulations assuming the thermal processing. The results of the simulations well reproduced the characteristics of the micro-structures obtained from the observations.. |
| 25. |
窒素添加したフェライト系耐熱鋼のXAFSによる化学状態評価. |
| 26. |
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. |
| 27. |
Al‐Mg‐Si系合金の長時間時効析出挙動. |
| 28. |
強加工を施した弾性異常Fe‐Ni‐Co‐Ti系合金の結晶相・方位マッピング. |
| 29. |
接合用Sn‐Cu系合金の微細組織のその場観察を用いた劣化機構の検討. |
| 30. |
積層前駆体膜を用いたBi,Pb‐2223超伝導薄膜. |
| 31. |
長時間時効を施したAl‐Mg‐Si系合金の析出形態. |
| 32. |
Shigeto Yamasaki, Masatoshi Mitsuhara, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low-Stress Creep Deformation in Long-Term Aged Ferritic Heat-Resistant Steel, MATERIALS TRANSACTIONS, 10.2320/matertrans.M2013427, Vol.55, No.5, pp.842-849, 2014.05, The transition of the creep deformation mechanism in the low-stress region of Grade P92 high Cr ferritic heat-resistant steel was investigated by a helicoid spring creep test. Specifically, the effect of variation in the microstructure of steel on creep deformation behavior was evaluated by subjecting samples to thermal aging for 1000, 3000, 5000, and 10000 h at 700 degrees C over a wide stress range. In addition, stress exponents were determined from the stress dependence of the minimum strain rate in the creep curves up to 270 ks. The transition of the creep mechanism was indicated when the stress exponent decreased from 4 in the high-stress region to 1 in the low-stress region below 40 MPa. A quantitative evaluation of the microstructure of a tempered martensite sample, including the determination of the amount of dissolved Mo and W, dispersion state of the precipitates, and length of the grain boundaries per unit area, was also carried out. Furthermore, the change in the minimum strain rate was evaluated as a function of the microstructural changes that accompanied thermal aging. It was found that the change in the strain rate was the most affected by the fineness of the martensitic lath structure in the high-stress region and by the dispersion density of M23C6 precipitates in the low-stress region. Based on these results, it was concluded that the microstructural parameter that most affects creep deformation behavior differs depending on the stress region due to the difference in the creep mechanism.. |
| 33. |
R. G. Abhilash Kumar, Satoshi Hata, Ken-ichi Ikeda, K. G. Gopchandran, Influence of metal ion concentration in the glycol mediated synthesis of Gd2O3:Eu3+ nanophosphor, CERAMICS INTERNATIONAL, 10.1016/j.ceramint.2013.10.020, Vol.40, No.2, pp.2915-2926, 2014.03, The solvothermal synthesis of highly luminescent and homogeneous Gd2O3:Eu3+ nanophosphor using diethylene glycol as medium, followed by controlled combustion with citric acid as fuel is reported. The influence of concentrations of carboxylic acid and metal cations on the structure, morphology and luminescence properties are investigated in detail. The microscopic investigations indicate the nanocrystalline nature and the strong influence of cation concentration on the size, shape and agglomeration of the particles. It is found that increase in concentration of metal cations lead to the reduction in agglomeration of nanophosphors. The large value of intensity parameter Omega(2), suggested that Eu3+ ions reside in a more asymmetric environment, resulted in intense emission due to D-5(0)-F-7(2) electric dipole transition. Emission decay analysis of the samples exhibited one exponential nature. The samples prepared under optimum conditions showed a quantum efficiency of 78.63% and a moderately high life time of 1.217 ms. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.. |
| 34. |
Mohammed Shahabuddin, Nasser S. Alzayed, Sangjun Oh, Seyong Choi, Minoru Maeda, Satoshi Hata, Yusuke Shimada, Md Shahriar Al Hossain, Jung Ho Kim, Microstructural and crystallographic imperfections of MgB2 superconducting wire and their correlation with the critical current density, AIP ADVANCES, 10.1063/1.4862670, Vol.4, No.1, 2014.01, 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.. |
| 35. |
R.G. Abhilash Kumar, Satoshi Hata, K. G. Gopchandran, Diethylene glycol mediated synthesis of Gd2O3:Eu 3+ nanophosphor and its Judd-Ofelt analysis, Ceramics International, 10.1016/j.ceramint.2013.05.010, Vol.39, No.8, pp.9125-9136, 2013.12, Gd1.9Eu0.1O3 nanophosphor with enhanced photoemission is successfully synthesized by a controlled combustion method of metal-citrate complex in diethylene glycol medium. It is found that the phase formation and spectral properties including quantum efficiency are highly sensitive to sintering temperature and the role of citric acid both as a chelating agent and as a fuel for combustion was evident in the study. The formation of cubic Gd2O3:Eu nanocrystalline phosphor was confirmed by X-ray diffraction, Raman and Infrared measurements. Transmission electron microscopic images together with the SAED patterns indicate the formation of spherical Gd2O3 nanocrystalline powder with well defined planes separated by 0.312 nm of cubic Gd2O3. The high degrees of homogeneity observed in the electron micrographs are attributed to the glycol medium used. The intensities of transitions between different J levels depend on the symmetry of the local environment of Eu 3+ activators and are described using the Judd-Ofelt analysis. The spectral properties of the samples prepared under optimum conditions have shown large asymmetric ratio, indicating high degree of distortion in local environment around Eu3+ ions and a maximum quantum efficiency of 78% was obtained. The life-time measurements indicated an increase from 0.83 to 1.28 ms with increase in sintering temperature from 700 to 1000 C. The chromaticity and correlated colour temperature of the emission were evaluated based on the 1931 CIE chromaticity diagram. The absorptions observed in the excitation spectra show the suitability of the nanophosphor obtained in this study for getting excited in UV, NUV and visible regions for a variety of device applications. © 2013 Elsevier Ltd and Techna Group S.r.l.. |
| 36. |
Shen Junjie, Ikeda Kenichi, Hata Satoshi, Nakashima Hideharu, Instantaneous Creep in Face-centered Cubic Metals at Ultra-low Strain Rates by a High-resolution Strain Measurement, JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION, 10.1007/s11595-013-0826-y, Vol.28, No.6, pp.1096-1100, 2013.12, Instantaneous creep in face-centered cubic metals, 5N Al (99.999%), 2N Al (99%) and 4N Cu (99.99%) with different grain sizes, was firstly investigated by sudden stress-change experiments at ultra-low strain rates (epsilon) over dot 1600 mu m, shows non-viscous behavior, and is controlled by the recovery of dislocations in the boundary of dislocation cells. On the other hand, for 5N Al with a small grain size, d(g) = 30 mu m, and low-purity aluminum, 2N Al, with d(g) = 25 mu m, creep shows viscous behavior and may be related to 'low temperature grain boundary sliding'. For high-purity copper, 4N Cu, with d(g) = 40 mu m and lower stacking fault energy, creep shows a non-viscous behavior, and is controlled by the recovery process of dislocations. For all of the samples, creep shows anelastic behavior.. |
| 37. |
Simulation with Two Spherical B2 Domains for Two Step Phase Separation in Fe-Ni-Al Alloys. |
| 38. |
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. |
| 39. |
α‐Tiの引張変形挙動に及ぼす添加元素の効果. |
| 40. |
純ニッケルの極低ひずみ速度クリープの変形機構の解明. |
| 41. |
Yuichiro Koizumi, Takeshi Otsuka, Yoritoshi Minamino, Takemori Takayama, Masanori Ueyama, Takeshi Daio, Satoshi Hata, Microstructures developed by super-rapid induction heating-and-quenching (SRIHQ) of Fe-1.4%Cr-1%C pearlitic steel, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 10.1016/j.msea.2013.04.024, Vol.577, pp.29-35, 2013.08, Microstructures and hardness of a Fe-1.4%Cr-1%C pearlitic steel processed by super-rapid induction heating-and-quenching (SRIHQ) under various conditions have been investigated. A nano-scaled laminated microstructure composed of two different types of martensite (highly-twinned or containing a high dislocation density) was formed and the maximum hardness was obtained by heating to 1223 K in 0.5 s and quenched. Electron energy loss spectroscopy indicated that the two different types of martensite were formed depending on the local solute-concentration in the non-uniform solute-distribution realized by the SRIHQ-process. (C) 2013 Elsevier B.V. All rights reserved.. |
| 42. |
Yusuke Shimada, Yuuki Kubota, Satoshi Hata, Ken-ichi Ikeda, Hideharu Nakashima, Toshiya Doi, Takanori Fujiyoshi, Influences of Microstructure on Critical Current Properties in MgB2/Al Film, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2013.2238284, Vol.23, No.3, pp.1-4, 2013.06, 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.. |
| 43. |
Akiyoshi Matsumoto, Hitoshi Kitaguchi, Toshiya Doi, Takato Kajihara, Satoshi Hata, The Microstructure and Superconducting Properties of Bi,Pb-2223 Thin Film Fabricated by RF Sputtering and Annealing Method, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2012.2233856, Vol.23, No.3, pp.1-4, 2013.06, We investigated the microstructures and superconducting properties of Bi,Pb-2223 thin films on SrTiO3(100) fabricated by radio-frequency (RF) sputtering and annealing. Most as-deposited films fabricated by RF sputtering did not exhibit a superconducting transition due to their low crystallinity, their deviation from the composition of Bi-2223, and their low inter-grain connectivity. The as-deposited films did not contain Pb. To obtain the Bi,Pb-2223 phase, we annealed the film with Bi,Pb-2223 pellets and powder. After annealing, we confirmed that the thin film contained Pb. T-c(zero) = 100 K was obtained in Bi,Pb-2223 thin film after post-annealing. We observed strong 00l peaks and a sharp quadrupole in X-ray theta - 2 theta and phi-scan measurements. These results suggest that this film consists of a single phase of Bi,Pb-2223 and has a biaxial orientation. The Bi,Pb-2223 thin film had a maximum J(c) of 0.1 x 10(5) A/cm(2) at 78 Kin a magnetic field of 2 T. Furthermore, Bi,Pb-2223 exhibited very strong anisotropy in its J(c) - B angle characteristics.. |
| 44. |
Jun-jie Shen, Kenichi Ikeda, Satoshi Hata, Hideharu Nakashima, "Abnormal transient creep" in fine-grained Al-5356 alloy observed at low strain rates by high-resolution strain measurement, TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA, 10.1016/S1003-6326(13)62585-6, Vol.23, No.5, pp.1209-1214, 2013.05, Transient creep at very low strain rates (less than 10(-10) s(-1)) is still unclear. The traditional uniaxial creep testing is less useful due to unsatisfied resolution strain (similar to 10(-6)). To study transient creep behavior at such low strain rates, a high-resolution strain measurement using the helicoid spring specimen technique was employed in a fine-grained Al-5356 alloy at temperatures ranging from 0.47T(m) to 0.74T(m) (T-m: melting point). To clarify transient creep mechanism at such low strain rates, transmission electron microscopy (TEM) was used in microstructure observation of crept specimens. The abnormal transient creep, high temperature strengthening at T>T-p(T-p: the phase transformation temperature, 0.58T(m)) or intermediate temperature softening at 0.4T(m) |
| 45. |
YAMAMOTO Shinji, NAKADA Nobuo, TSUCHIYAMA Toshihiro, TAKAKI Setsuo, MURAYAMA Mitsuhiro, HATA Satoshi, Deformation and dissolution of Cu particles in iron matrix during cold-rolling, 材料とプロセス(CD-ROM), Vol.26, No.1, p.ROMBUNNO.277, 2013.03. |
| 46. |
Fe‐2wt.%Cu合金の冷間圧延による組織変化. |
| 47. |
オーステナイト系耐熱鋼の局所結晶方位解析によるクリープひずみの評価. |
| 48. |
磁性体試料のためのSTEM連続傾斜観察条件の検討. |
| 49. |
Takayoshi Nakano, Koji Hagihara, Satoshi Hata, Hajime Shigyo, Hideharu Nakashima, Yukichi Umakoshi, Ashok Arya, Ulhas D. Kulkarni, Long-period ordered superstructures that appear in an (Al,Ga)-rich (Al,Ga)Ti system, PHILOSOPHICAL MAGAZINE, 10.1080/14786435.2012.699691, Vol.93, No.1-3, pp.22-37, 2013.01, Long-period ordered superstructures in an (Al,Ga)-rich (Al,Ga)Ti system composed of (Al,Ga) x Ti100- x (x=5065 at. %) were investigated by using melt-spun ribbons, focusing on the ordering process of the superstructural phases. Compositional regions in which h-(Al,Ga)2Ti (Ga2Zr-type), (Al,Ga)5Ti3 and (Al,Ga)3Ti2 with threefold, fourfold and fivefold periodicity, respectively, appeared coherently in the L10 matrix were identified by electron diffraction patterns in two different temperature conditions of as-spun (a relatively high-temperature state) and heat-treatment at 700 degrees C (a relatively low-temperature state). The (Al,Ga)5Ti3 superstructural phase always existed between the compositional region where h-(Al,Ga)2Ti and (Al,Ga)3Ti2 dominantly appear. Therefore, periodical ordering proceeds following the periodicity of the concentration wave of pure (Al,Ga) layers parallel to {310) in the Ti (002) layers from threefold to fivefold periodicity via fourfold periodicity. We found that the (Al,Ga)3Ti2 long-period superstructural phase preferentially appeared with increasing Ga concentration in the melt-spun ribbon annealed at 700 degrees C. In other words, the h-(Al,Ga)2Ti superstructure with threefold periodicity preferentially appeared at the high temperature and a low Ga concentration. Thus, the (Al,Ga)3Ti2-type superstructure was never produced without the addition of Ga in the present study. The long-period ordered superstructures were composed of three pairs of primitive cells, (Al,Ga)Ti2, (Al,Ga)Ti3 and (Al,Ga)Ti4, with periodic atomic arrangements corresponding to lean rhombus, fat rhombus and square, respectively. We discuss the ordering process throughout the (Al,Ga)5 superstructure based on the periodic concentration wave and exchange of atoms. The effect of long-period ordered superstructures on hardness is also mentioned.. |
| 50. |
Innovations in Superconducting Technology for Next-generation Railway Systems : Development of Superconducting Cables for Railway Systems
DC electric railway systems are widely used in Japan, including in the metropolitan areas. However, they have some problems, such as limited use of regenerative brakes and energy loss. In order to solve those problems, and to attain energy savings for next-generation electric railway systems, we have been studying the feasibility of applying superconducting power cables to DC electric feeder systems. In this study, investigations regarding issues such as effective use of regenerative brakes and loss reduction have been carried out on the assumption that the substations concerned are connected with each other via superconducting power cables placed in parallel with the feeder line. This research was supported by the Japan Science and Technology Agency, JST, as part of the Strategic Promotion of Innovative Research and Development Problem.. |
| 51. |
Innovations in Superconducting Technology for Next-generation Railway Systems : Development of Superconducting Cables for Railway Systems
DC electric railway systems are widely used in Japan, including in the metropolitan areas. However, they have some problems, such as limited use of regenerative brakes and energy loss. In order to solve those problems, and to attain energy savings for next-generation electric railway systems, we have been studying the feasibility of applying superconducting power cables to DC electric feeder systems. In this study, investigations regarding issues such as effective use of regenerative brakes and loss reduction have been carried out on the assumption that the substations concerned are connected with each other via superconducting power cables placed in parallel with the feeder line. This research was supported by the Japan Science and Technology Agency, JST, as part of the Strategic Promotion of Innovative Research and Development Problem.. |
| 52. |
Microstructural Evolution of Bi,Pb-2223 Films During Heat-Treatment. |
| 53. |
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. |
| 54. |
Mg‐Al‐Ca‐Sn‐Mnダイカスト合金の高温強度に及ぼす粒界晶出相の影響. |
| 55. |
Preface to the Special Issue on Young Researchers' Comments on Globalization in Research and Education of Materials Science in Japan. |
| 56. |
粒界晶出相がMg‐Al‐Ca‐Sr系ダイカスト合金の高温強度に及ぼす影響. |
| 57. |
Fe‐Al‐Ni合金における2段階相分離過程の電子線トモグラフィー観察. |
| 58. |
SEM/EBSD法によるクリープ変形に伴うGr.92鋼溶接継手の組織変化挙動解析. |
| 59. |
Al‐Mg‐Si系合金における時効生成物と転位の相互作用. |
| 60. |
Al‐Mg‐Si系合金中のクラスタおよび析出物の転位運動への影響. |
| 61. |
Mg‐Al‐Ca系合金の高温強度に及ぼす粒界晶出相と粒内分散粒子の影響. |
| 62. |
DP鋼打ち抜き部の局所方位解析(DP鋼の打ち抜き大変形の定量化‐3). |
| 63. |
SmBa2Cu3Oy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. |
| 64. |
フェライト系耐熱鋼の低応力クリープ変形挙動. |
| 65. |
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. |
| 66. |
Al‐Mg‐Si系合金の内部組織と力学特性に及ぼすScとZrの影響. |
| 67. |
EDDC法により作製したSmBa2Cu3Oy高温超伝導線材の局所微細構造解析. |
| 68. |
Influence of alloying elements on creep rupture strength and aging toughness in austenitic heat resistant steels
Highly strengthened heat-resistant steels for boiler tubing are required to develop for higher efficiency of coal-fired power plants. Creep rupture test and impact test after long-term thermal aging have been carried out on austenitic steels to reveal the influence of alloying elements on the properties which are required for boiler materials. Creep rupture strength at 700 ℃ for 105 h of a highly-alloyed steel B was estimated to be higher than 100 MPa. However, aging toughness of the steels studied became lower than 30 J/cm2 after aging for 1000 h. It was clarified that precipitation and growth of M23C6, Laves and W-rich phases at grain boundaries lower the toughness of the steels. Therefore, optimization of contents of alloying elements such as C, Cr, Mo and W is needed to suppress the precipitation and growth.. |
| 69. |
Al‐Mg‐Si系合金の引張変形特性に及ぼす析出形態の影響. |
| 70. |
J. J. Shen, K. Ikeda, S. Hata, H. Nakashima, Creep Mechanisms in a Fine-Grained Al-5356 Alloy at Low Stress and High Temperature, MATERIALS TRANSACTIONS, 10.2320/matertrans.M2011143, Vol.52, No.10, pp.1890-1898, 2011.10, Monotonic creep tests were carried out on fine-grained Al-5356 alloy with grain size d(g) = 5 +/- 0.5 mu m by the helicoid spring specimen technique at homologous temperatures ranging from 0.63 to 0.74 and applied stresses of 0.13 to 1.42 MPa. At stresses lower than about 0.50 MPa, Bingham-type viscous creep with activation energy Q = 80 +/- 25 kJ/mol, characterized by a threshold stress which decreases with increasing temperature, was predominant. At a stress above about 0.50 MPa, grain boundary sliding with a stress exponent n = 2 and Q = 85 25 kJ/mol obviously contributed to the measured creep data. Stress redistribution was evaluated, and it did not greatly influence the stress exponent. The creep mechanisms were elucidated with respect to standard creep models supported by the substructures studied by transmission electron microscopy. Viscous creep (n = 1) was identical to be Harper-Dorn creep controlled by dislocation core diffusion. The motion of jogs on edge dislocations dependent on dislocation core diffusion was observed to control the creep. Grain boundary sliding accommodated by slip with n = 2 was noted, while hardening and the recovery of dislocations at grain boundaries were suggested to control the creep. Microstructural observations along with a determination of parametric variations in the creep rates were useful for identifying the underlying deformation mechanisms. [doi:10.2320/matertrans.M2011143]. |
| 71. |
Fe‐Ni‐Al合金における二段階相分離組織の三次元解析. |
| 72. |
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. |
| 73. |
Mo双結晶の圧縮変形で生じた粒界近傍の転位の3次元観察. |
| 74. |
Sc,Zr複合添加6000系アルミニウム合金の再結晶挙動と力学特性. |
| 75. |
Junjie Shen, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Transient Creep in High-Purity Aluminum at Ultra-Low Strain Rate and Room Temperature by Constant Stress and Changing-Stress Experiments, MATERIALS TRANSACTIONS, 10.2320/matertrans.M2011175, Vol.52, No.10, pp.1885-1889, 2011.10, Creep of high-purity aluminum (5N Al) at room temperature and ultra-low strain rate was investigated by a high sensitive helicoid-spring specimen technique under conditions of constant and changing stress. Creep deformation consists of transient creep stages, and no secondary creep stage was observed. Li's equation showed a good fit to the experimental curves.
During nominal steady-state creep, the stress exponent is equal to one regardless of initial state of specimens. However, the nominal steady-state creep rate for water quenched 5N Al is one order less than that for the static recovered specimens due to work hardening. With increase in stress, creep strengthening (the creep rate progressively decreasing in subsequent segments) was observed, which is due to different hardening remains because changing-stress creep experiment was conducted in the transient creep stage. Those phenomena of work hardening indicate creep deformation is controlled by recovery and work-hardening mechanism.
During transient creep, every decrease in stress is associated with the large and long anelastic backflow. The anelastic transient strain for stress reduction is equivalent to elastic deformation corresponding to the applied stress, while transient strain is 2.5 times greater than the equivalent elastic deformation regardless of whether stress increases or is constant. The transient effect was suggested to be due to a mix of anelastic behavior caused by the internal redistribution of stress and inelastic behavior. [doi:10.2320/matertrans.M2011175]. |
| 76. |
Junjie Shen, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Transient Creep in High-Purity Aluminum at Ultra-Low Strain Rate and Room Temperature by Constant Stress and Changing-Stress Experiments, MATERIALS TRANSACTIONS, 10.2320/matertrans.M2011175, Vol.52, No.10, pp.1885-1889, 2011.10, Creep of high-purity aluminum (5N Al) at room temperature and ultra-low strain rate was investigated by a high sensitive helicoid-spring specimen technique under conditions of constant and changing stress. Creep deformation consists of transient creep stages, and no secondary creep stage was observed. Li's equation showed a good fit to the experimental curves.During nominal steady-state creep, the stress exponent is equal to one regardless of initial state of specimens. However, the nominal steady-state creep rate for water quenched 5N Al is one order less than that for the static recovered specimens due to work hardening. With increase in stress, creep strengthening (the creep rate progressively decreasing in subsequent segments) was observed, which is due to different hardening remains because changing-stress creep experiment was conducted in the transient creep stage. Those phenomena of work hardening indicate creep deformation is controlled by recovery and work-hardening mechanism.During transient creep, every decrease in stress is associated with the large and long anelastic backflow. The anelastic transient strain for stress reduction is equivalent to elastic deformation corresponding to the applied stress, while transient strain is 2.5 times greater than the equivalent elastic deformation regardless of whether stress increases or is constant. The transient effect was suggested to be due to a mix of anelastic behavior caused by the internal redistribution of stress and inelastic behavior. [doi:10.2320/matertrans.M2011175]. |
| 77. |
局所方位解析法を用いたフェライト系耐熱鋼溶接熱影響部クリープ弱化要因の特定. |
| 78. |
時効硬化型Al‐Mg‐Si系合金の引張変形特性と転位組織. |
| 79. |
酸化物分散強化型フェライト鋼の強度特性に及ぼすナノメゾスケール微細組織構造に関する研究. |
| 80. |
Junjie Shen, Shigeto Yamasaki, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low-Temperature Creep at Ultra-Low Strain Rates in Pure Aluminum Studied by a Helicoid Spring Specimen Technique, MATERIALS TRANSACTIONS, 10.2320/matertrans.M2010405, Vol.52, No.7, pp.1381-1387, 2011.07, The creep behavior in pure aluminum has been investigated by helicoid spring creep tests at strain rates, (epsilon) over dot, lower than 10(-10) s(-1) and low temperature ranging from 0.32T(m) to 0.43T(m). It was found that the creep behavior in this region depends strongly on grain sizes and impurity concentrations. For high-purity aluminum (5N Al) with an average grain size, d(g) > 1600 mu m, nearly the wire diameter of the spring sample, where the role of grain boundary during creep deformation can be negligible, the stress exponent was n similar to 5 and the activation energy was Q(c) = 32 kJ/mol. Microstructural observation showed the formation of large dislocation cells (similar to 10 mu m) and tangled dislocations at the cell walls. For high-purity aluminum (5N Al) with d(g) = 24 mu m, the stress exponent was n similar to 1 and the activation energy was Q(c) = 15 kJ/mol. On the other hand, for commercial low-purity aluminum (2N Al) with d(g) = 25 mu m, the stress exponent was n = 2 and the activation energy was Q(c)= 25 kJ/mol. Microstructural observations revealed dislocations emitted from grain boundaries, those dislocations interacting with intragranular dislocations and the formation of dislocation cells in the grains. Based on those experimental results, the low-temperature creep mechanisms in pure aluminum at (epsilon) over dot |
| 81. |
Junjie Shen, Shigeto Yamasaki, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low-Temperature Creep at Ultra-Low Strain Rates in Pure Aluminum Studied by a Helicoid Spring Specimen Technique, MATERIALS TRANSACTIONS, 10.2320/matertrans.M2010405, Vol.52, No.7, pp.1381-1387, 2011.07, The creep behavior in pure aluminum has been investigated by helicoid spring creep tests at strain rates, (epsilon) over dot, lower than 10(-10) s(-1) and low temperature ranging from 0.32T(m) to 0.43T(m). It was found that the creep behavior in this region depends strongly on grain sizes and impurity concentrations. For high-purity aluminum (5N Al) with an average grain size, d(g) > 1600 mu m, nearly the wire diameter of the spring sample, where the role of grain boundary during creep deformation can be negligible, the stress exponent was n similar to 5 and the activation energy was Q(c) = 32 kJ/mol. Microstructural observation showed the formation of large dislocation cells (similar to 10 mu m) and tangled dislocations at the cell walls. For high-purity aluminum (5N Al) with d(g) = 24 mu m, the stress exponent was n similar to 1 and the activation energy was Q(c) = 15 kJ/mol. On the other hand, for commercial low-purity aluminum (2N Al) with d(g) = 25 mu m, the stress exponent was n = 2 and the activation energy was Q(c)= 25 kJ/mol. Microstructural observations revealed dislocations emitted from grain boundaries, those dislocations interacting with intragranular dislocations and the formation of dislocation cells in the grains. Based on those experimental results, the low-temperature creep mechanisms in pure aluminum at (epsilon) over dot |
| 82. |
Three-dimensional Microstructure and High Temperature Strength in ODS 9Cr Ferritic Heat Resistant Steels. |
| 83. |
SHEN Junjie, IKEDA Ken‐ichi, HATA Satoshi, NAKASHIMA Hideharu, Creep behavior in a fine-grained Al-5356 alloy at low stress and intermediate temperature, 九州大学大学院総合理工学報告, 10.15017/19574, Vol.33, No.1, pp.1-6, 2011.06, Creep in an Al-5356 solid solution alloy with an intercept grain size, dE=5±0.5um was in-vestigated using the helicoid spring specimen technique. The testing temperatures ranged from 423 K to 523 K (0.47 to 0.58 Tm) and the applied stresses from 0.20 MPa to 4.04 MPa. It was found that under the above conditions, viscous creep of Bingham type occurs, characterized by a threshold stress which decreases with increasing temperature. The activation energy is Qc = 44±7 kJ/mol. No microstructural changes were observed in recrystallized and the as-crept specimens. The meas-ured creep rates were found to be four orders faster than that predicted by Coble creep model.. |
| 84. |
Shen Junjie, Ikeda Ken-ichi, Hata Satoshi, Nakashima Hideharu, Creep behavior inb a fine-grained Al -5356 alloy at low stress and intermediate temperature, Engineering sciences reports, Kyushu University, 10.15017/19574, Vol.33, No.1, pp.1-6, 2011.06, Creep in an Al-5356 solid solution alloy with an intercept grain size, dE=5±0.5um was in-vestigated using the helicoid spring specimen technique. The testing temperatures ranged from 423 K to 523 K (0.47 to 0.58 Tm) and the applied stresses from 0.20 MPa to 4.04 MPa. It was found that under the above conditions, viscous creep of Bingham type occurs, characterized by a threshold stress which decreases with increasing temperature. The activation energy is Qc = 44±7 kJ/mol. No microstructural changes were observed in recrystallized and the as-crept specimens. The meas-ured creep rates were found to be four orders faster than that predicted by Coble creep model.. |
| 85. |
Yusuke Shimada, Yuuki Kubota, Satoshi Hata, Ken-ichi Ikeda, Hideharu Nakashima, Akiyoshi Matsumoto, Kazumasa Togano, Jahmahn Hur, Hiroaki Kumakura, Microstructure in High-Density MgB2 Wires Prepared by an Internal Mg Diffusion Method, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2010.2091097, Vol.21, No.3, pp.2668-2671, 2011.06, 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.. |
| 86. |
Alテープ上に作製したMgB2薄膜の微細組織構造. |
| 87. |
Mg2Cuを添加源としたCu添加MgB2線材の微細構造. |
| 88. |
X線CTによるMgB2線材の組織観察. |
| 89. |
Al‐Mg‐Si‐Sc‐Zr合金の再結晶挙動と力学特性. |
| 90. |
H. Gao, K. Ikeda, S. Hata, H. Nakashima, D. Wang, H. Nakashima, Measurement of strain and strain relaxation in free-standing Si membranes by convergent beam electron diffraction and finite element method, ACTA MATERIALIA, 10.1016/j.actamat.2011.01.031, Vol.59, No.7, pp.2882-2890, 2011.04, Bridge-shaped free-standing Si membranes (FSSM), strained by low-pressure (LP) Si(x)N(y), plasma-enhanced (PE) Si(x)N(y) and Si(x)Ge(1-x) stressors, were measured by convergent beam electron diffraction (CBED) and the finite element method (FEM). The results of CBED show that, while the strain along the length of the FSSM is compressive in an LPSi(x)N(y)/Si sample, those along the length of the FSSM are tensile in PESi(x)N(y)/Si and Si(x)Ge(1-x)/Si samples. The average absolute values of strains are different in FSSM with LPSi(x)N(y), PESi(x)N(y) and Si(x)Ge(1-x) as stressors. The FEM was used to compensate the results of CBED taking into account the strain relaxation in transmission electron microscopy (TEM) sample preparation. The FEM results give the strain properties in three dimensions, and are in good agreement with the results of CBED. There is approximately no strain relaxation along the length of FSSM, and the elastic strains along the other two axes in FSSM are partially relaxed by thinning down for the preparation of TEM samples. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.. |
| 91. |
X線CTによるMgB2超伝導線材の組織観察の試み. |
| 92. |
酸化物分散強化オーステナイト系耐熱鋼の高温強度と微細組織. |
| 93. |
Self Composed Si3N4-TiN Ceramics Prepared from Si-TiC-TiO2 Mixed Powders. |
| 94. |
Alテープ上へのMgB2薄膜の作製と特性評価. |
| 95. |
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. |
| 96. |
Yoji Miyajima, Masatoshi Mitsuhara, Satoshi Hata, Hideharu Nakashima, Nobuhiro Tsuji, Quantification of internal dislocation density using scanning transmission electron microscopy in ultrafine grained pure aluminium fabricated by severe plastic deformation, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 10.1016/j.msea.2010.09.058, Vol.528, No.2, pp.776-779, 2010.12, Dislocation density within ultrafine grains in severely deformed aluminium was evaluated by the scanning transmission electron microscopy. The values were around 10(14) m(-2) in commercial pure aluminium samples with equivalent strain up to 10. The obtained dislocation densities values correspond to strength between 55 MPa and 70 MPa according to the Bailey-Hirsch relationship. (C) 2010 Elsevier B.V. All rights reserved.. |
| 97. |
Mg‐Al‐Ca‐Sr系合金の高温変形と微細組織. |
| 98. |
Sc,Zr複合添加Al‐Mg‐Si系合金の再結晶組織と引張変形特性. |
| 99. |
アルミニウム添加量を変化させたMg‐Al‐Ca系ダイカスト合金の高温変形挙動. |
| 100. |
Mg‐Al‐Ca系ダイカスト合金の高温力学特性に及ぼすAl添加量の影響. |
| 101. |
Hongye Gao, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Dong Wang, Hiroshi Nakashima, Microstructure and strain distribution in freestanding Si membrane strained by SixNy deposition, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 10.1016/j.msea.2010.07.004, Vol.527, No.24-25, pp.6633-6637, 2010.09, Strain in a bridge-shaped freestanding Si membrane (FSSM) induced by depositing an amorphous SixNy layer was measured by convergent-beam electron diffraction (CBED). CBED results show that the strain magnitude depends negatively on the FSSM thickness. FEM is a supplement of the result of CBED due to the relaxation of TEM samples during fabricating. The FEM analysis results ascertain the strain property in three dimensions, and show that the strain magnitude depends negatively on the length of FSSM, and the magnitude of the compressive strain in FSSM increases as the position is closer to the upper Si/SixNy interface. (C) 2010 Elsevier B.V. All rights reserved.. |
| 102. |
Hongye Gao, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Dong Wang, Hiroshi Nakashima, Strain distribution in freestanding Si/SixNy membranes studied by transmission electron microscopy, THIN SOLID FILMS, 10.1016/j.tsf.2010.06.023, Vol.518, No.23, pp.6787-6791, 2010.09, Strain was induced in a bridge-shaped freestanding Si membrane (FSSM) by depositing an amorphous SixNy layer to surround the Si membrane. Convergent beam electron diffraction revealed that compressive strain is distributed uniformly along the horizontal direction in SixNy-deposited FSSM. On the other hand, strain decreases to almost zero at the ends of the FSSM, where the SixNy layer beneath the Si layer is replaced SiO2 buried oxide layer. (C) 2010 Elsevier B.V. All rights reserved. |
| 103. |
クリープ変形したNi基超合金中の転位組織の3次元観察. |
| 104. |
コイルばねクリープ試験法による改良9Cr‐1Mo鋼の極低速クリープ挙動評価. |
| 105. |
室温における超高純度アルミニウムの極低ひずみ速度変形挙動の評価. |
| 106. |
TEMトモグラフィーによる金属材料の評価. |
| 107. |
酸化物分散強化型フェライト鋼の強度特性に及ぼすナノメゾスケール微細組織構造に関する研究. |
| 108. |
Three-dimensional visualization of lattice defects by electron tomography. |
| 109. |
Three-dimensional Visualization of Lattice Defects by Electron Tomography. |
| 110. |
内部Mg拡散法により作製したMgB2線材の微細組織構造. |
| 111. |
K. Hagihara, T. Nakano, S. Hata, O. Zhu, Y. Umakoshi, Improvement of aligned lamellar structure by Cr-addition to NbSi2/MoSi2 duplex-silicide crystals, SCRIPTA MATERIALIA, 10.1016/j.scriptamat.2010.01.002, Vol.62, No.8, pp.613-616, 2010.04, The addition of Cr to (Mo0.85Nb0.15)Si-2 crystals significantly improves the thermal stability of the lamellar structure composed of C11(b)-MoSi2 and C40-NbSi2 phases. Analysis using electron microscopy indicates the segregation of Cr atoms at the C40/C11(b) lamellar interface. This leads to a decrease in the lattice misfit strain at the interface and better thermal stability of the lamellae. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.. |
| 112. |
6111合金のリジングと集合組織の関係. |
| 113. |
Al‐Mg‐Si系合金の引張変形挙動におよぼす時効析出形態の影響. |
| 114. |
H. Matsuo, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima, Electron microscopy analysis for crack propagation behavior of alumina, INTERNATIONAL JOURNAL OF FATIGUE, 10.1016/j.ijfatigue.2009.06.006, Vol.32, No.3, pp.592-598, 2010.03, In order to clarify crack propagation behavior of alumina (alpha-Al(2)O(3)), intergranular and transgranular fractures of alumina were investigated by electron microscopy techniques. For the intergranular fractures cracked grain boundaries were investigated by scanning electron microscopic electron back-scattered diffraction (SEM-EBSD) analysis. It was revealed that the intergranular fracture behavior of polycrystalline alumina with random distribution of crystallographic orientations is independent on grain boundary characters. For the transgranular fractures, fracture surfaces formed in a single-crystalline alumina were observed by electron tomography combined with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high resolution TEM (HR-TEM). Three kinds of fracture surfaces were observed: even fracture surfaces, even fracture surfaces with step-terraces and fracture surfaces composed of the even fracture surface and the curved one. The even fracture surfaces mostly consist of cleavage planes parallel to {1 (1) over bar 0 2} and {1 (1) over bar 0 4}. On the other hand, the even fracture surfaces with step-terraces consist of the cleavage planes and basal planes (0 0 0 1). For the fracture surfaces composed of the even fracture surface and the curved one, both the even and curved shapes the even parts were formed by the fine cleavage planes and basal planes, whose intervals were inhomogeneous. It was indicated that the fracture surfaces in alumina are composed of the cleavage planes or basal plane at an atomic scale. (C) 2009 Elsevier Ltd. All rights reserved.. |
| 115. |
MgB2超伝導薄膜の臨界電流特性と微細組織制御. |
| 116. |
Pt系分散強化合金の低応力領域でのクリープ特性の検討. |
| 117. |
コイルばねクリープ試験法によるAl‐Mg系合金の低ひずみ速度変形挙動の評価. |
| 118. |
ラスマルテンサイトのクリープ変形に伴う動的組織変化. |
| 119. |
多結晶MgB2超伝導バルク体の結晶方位分布解析. |
| 120. |
Y. Koizumi, T. Fujita, Y. Minamino, S. Hata, Effects of plastic deformation on lamellar structure formation in Ti-39 at.% Al single crystals, ACTA MATERIALIA, 10.1016/j.actamat.2009.10.027, Vol.58, No.3, pp.1104-1115, 2010.02, The effects of plastic deformation on lamellar structure formation in solution-treated Ti-39 at.% Al single crystals were investigated, focusing on the role of dislocations of different slip systems. The dislocations were introduced by indentation on the surfaces of solution-treated single crystals with different crystallographic orientations. Traces of basal and prism, slips were observed, depending on the position relative to the indentation. During annealing at alpha(2) + gamma dual-phase temperatures, lamellar structures were formed faster where basal slip had occurred than where prism slip had occurred. After long annealing, the length scale of lamellar structures formed depends on the slip system operated during prior deformation: in the region where only one of either basal or prism slip had occurred the lamellar structure was coarser than in undeformed crystal, while in the region where both basal and prism slips occurred the lamellar structure was finer than those formed in undeformed crystal. The reasons for the differences in lamellar structures are discussed on the basis of the frequencies of stacking fault formation on (0 0 0 1) planes as precursors to gamma-precipitates. The results suggest that the cross-slip of dislocations between basal and prism planes, which gives rise to the formation of multiple stacking faults on many parallel (0 0 0 1) planes, is responsible for the refinement of lamellar structures. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.. |
| 121. |
High Temperature Fatigue of Oxide-Dispersion-Strengthened Platinum Alloys. |
| 122. |
Observation of microstructure formation in an in-situ fabrication process of MgB2 superconducting tapes. |
| 123. |
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. |
| 124. |
Stress Intensity Factor and Crack Propagation Behavior of Thin alpha-Alumina
This paper reports the mechanical property and crack propagation behavior of thin ceramics. A method to evaluate the stress intensity factor, K-l, of thin ceramics was proposed. Dependence of K-l values on the average grain size, d, of thin alpha-alumina were measured by the method. K-l values of thin alpha-ahuuina decreased with increasing d values from 4.3 mu m to 15.2 mu m, while the K-l values were almost constant for 15.2 mu m |
| 125. |
Three-dimensional Visualization of Dislocations Using Two Diffraction Conditions. |
| 126. |
FIB Thinning and TEM Observation of Hard Tissue. |
| 127. |
The Morphology of Precipitations in Al-Mg-Si-Sc-Zr Hot Rolled Sheet. |
| 128. |
Stress-induced phase transformation in the vicinity of Vickers indentations in 10mol% CeO2 doped tetragonal ZrO2 polycrystal
The stress-induced martensitic phase transformation from a tetragonal (t) phase to a monoclinic (m) phase in a CeO2 doped tetragonal polycrystal (Ce-TZP) was investigated from the view pints of characters of lattice correspondences (LCs) between tand m-phases and morphology of m-phase. Electron back scattering diffraction (EBSD) analysis in the vicinity of Vickers indentations in Ce-TZP reveled that there were three LCs, named LCA (type A), LCB (type B) and LCC (type C), where fractions of the three LCs were 12%, 8% and 80%, respectively. Morphology of m-phase showing each of the three LCs were observed by transmission electron microscopy (TEM). A single variant of mphase with lamellar plate-shaped morphology (m-plates) was formed near the Vickers indentations. In contrast, two variants of m-phases with twin relationships (m-twins) were formed far from the Vickers indentations. The infinitesimal-deformation theory was adopted to calculate scalar magnitude of internal stress within the m-plates and m-twins for each type of the LCs. Irrespective of morphology of the m-phase, the internal stress field for type C is a tensile stress field. Regardless of the type of LCs, absolute values of internal stress in the m-plates are higher than those in the mtwins.. |
| 129. |
Electron Tomographic Observation of Fracture Surfaces in Single-crystalline α-alumina. |
| 130. |
Premix‐PICT拡散法で作製したMgB2バルク体のJc特性と微細組織. |
| 131. |
Al‐0.5Mg‐0.5Si‐0.3Sc‐0.2Zr合金の再結晶粒成長挙動. |
| 132. |
Al‐Mg‐Si合金におけるクラスタの熱的安定性. |
| 133. |
Al‐Mg‐Si合金の時効析出形態と引張変形挙動. |
| 134. |
Mg‐Al‐Ca合金の高温変形挙動のAl添加量依存性. |
| 135. |
PICT拡散法で作製したMgB2超伝導バルク体の微細組織観察. |
| 136. |
Sc,Zr複合添加Al‐Mg‐Si系合金板の再結晶組織. |
| 137. |
コイルばねクリープ試験法による高Cr鋼の低速クリープ挙動評価. |
| 138. |
透過電子顕微鏡による結晶材料組織の3次元可視化. |
| 139. |
酸化物分散強化型フェライト鋼の組織制御に基づく強度特性向上に関する研究 酸化物分散強化型フェライト鋼の強度特性に及ぼすナノメゾスケール微細組織構造に関する研究. |
| 140. |
K. Yamada, M. Mitsuhara, S. Hata, Y. Miyanaga, R. Teranishi, N. Mori, M. Mukaida, K. Kaneko, Three-dimensional observation of microstructures in Y123 films fabricated by TFA-MOD method, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 10.1016/j.physc.2009.05.059, Vol.469, No.15-20, pp.1446-1449, 2009.08, We were successful for three-dimensional imaging of microstructures in YBa(2)Cu(3)O(7-y) (Y123) films fabricated by metal organic deposition using trifluoroacetates (TFA-MOD) method. We have reported previously, that a transmission electron microscopy (TEM) analysis clarified microstructures such as Y123 crystal grains and pores in the Y123 films. In order to derive important parameters for enhancement Of Superconducting properties of the Y123 films, quantitative analyses of those microstructures are required. Then, control of both pores and a-axis oriented grains distribution in the Y123 films are important. However, general TEM images provide only a two-dimensional projection of a three-dimensional object. An electron tomography is an effective technique for three-dimensional structure analysis of various materials. Cross-sectional view specimen for the three-dimensional electron tomography was prepared by focused ion-beam milling equipped with micro-sampling system. A scanning transmission electron microscopy - annular dark field technique was used for the present three-dimensional electron tomography. For the cross-sectional specimen of fired Y123 films, three-dimensional shapes and distributions of both pores and unreacted phases were observed in reconstructed images. Also, morphologies of the Y123 film surface were clearly seen. (C) 2009 Elsevier B.V. All rights reserved.. |
| 141. |
高純度アルミニウム箔の再結晶集合組織形成挙動に関する研究. |
| 142. |
Yutaka Tsukano, Toshiya Doi, Hiroki Yamashita, Akira Tanaka, Ikumi Iwasaki, Yoshinori Hakuraku, Hitoshi Kitaguchi, Ken-ichiro Takahashi, Harini Sosiati, Satoshi Hata, Ken-ichi Ikeda, Hideharu Nakashima, Fabrication of Multilayered MgB2/Ni Thin Films and Their Flux Pinning Properties, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2009.2018527, Vol.19, No.3, pp.2807-2810, 2009.06, We prepared the multilayered MgB2/Ni thin films with the Ni layer spacings of 32, 23 and 16 nm. The MgB2/Ni multilayer nanostructure was confirmed to be obtained from the scanning transmission electron microscope observation. The clear enhancement of J(c) was observed in the multilayered MgB2/Ni thin film when the magnetic field was applied parallel to the film surface. Moreover, the peak position of F-p - B curves shifted to higher magnetic field with decreasing the Ni layer spacing.. |
| 143. |
High Temperature Deformation Behavior of Sn-Based Solder Alloys under Low Stress Conditions by a Helical Spring Creep Testing Method
In the field of electronics, it is crucial to guarantee long-term joint reliability of the Sn-Ag-Cu solder alloy. Creep tests in low-stresses are necessary to guarantee the reliability. However, a very long period of time is required for the creel) tests. To decide a steady-state creep strain rate, an approximate equation of a creep curve was newly applied to the helical spring creel) test known as a method of a low-stress creep test. Obtained results are as follows. (1) The torsional strain component is decreased with the deformation of the helical spring shaped specimen. Therefore, the steady-state creep rate cannot be detected in the helical spring creep test. The approximate equation of a creep curve introduced by Li's group was found to be effective to obtain the steady-state creep rate for Sn-based solder alloy. (2) The helical spring creep testing method that uses the torsional deformation of the test specimen is more effective for the Sn-based solder alloy with a strong anisotropy of strength than the uniaxis creep testing method. (3) In the heat-treated Sn-3.0 inass%Ag-0.5 inass%Cu solder alloy, the creep stress exponent changed from 19 into 1.1 on the boundary of about 14 MPa. This result implies that the creep deformation mechanism was changed from the dislocation creep with dispersion-strengthening to the grain boundary sliding. This phenomenon was found for the first time by using the helical spring creep testing method.. |
| 144. |
Properties of Die Cast Creep Resistant Mg-Al-Ca-Sn System Alloy. |
| 145. |
in‐situ MgB2線材の熱処理過程の組織観察. |
| 146. |
Al‐Mg‐Si合金における析出形態の引張強度への影響. |
| 147. |
Al‐Mg‐Si系合金の再結晶挙動に及ぼすScとZr添加の影響. |
| 148. |
Mg‐Al‐Ca系合金の高温力学特性に及ぼすAl添加量の影響. |
| 149. |
Sc,Zr複合添加Al‐Mg‐Si系合金熱間圧延板の析出形態. |
| 150. |
SrAl2O4系応力発光材料の微細組織観察. |
| 151. |
SrAl2O4系応力発光材に導入された面欠陥の透過型電子顕微鏡観察. |
| 152. |
HATA Satoshi, SOSIATI Harini, YOSHIDOME Takeshi, KUWANO Noriyuki, MATSUMOTO Akiyoshi, KITAGUCHI Hitoshi, KUMAKURA Hiroaki, Transmission Electron Microscopy Observation of MgB2 Superconducting Materials with Inhomogeneous Microstructure: Influences of Specimen Preparation Methods, 九州大学大学院総合理工学報告, Vol.30, No.1, pp.20-24, 2009.03. |
| 153. |
マウス大腿骨における生体アパタイトの電子顕微鏡観察. |
| 154. |
ラスマルテンサイトのクリープ変形に伴う結晶学的組織変化. |
| 155. |
極薄Ni層を人工ピンとして導入したMgB2薄膜のマッチング磁場とNi層間隔. |
| 156. |
Effectiveness of scanning transmission electron microscopy observation with medium and low magnifications for steels. |
| 157. |
Effectiveness of scanning transmission electron microscopy observation with medium and low magnifications for steels. |
| 158. |
In-situ heating SEM/EBSD analysis of recrystallization behavior in pure aluminum foils
Report of the center of advanced instrumental analysis, Kyushu University
. |
| 159. |
Three-Dimensional Observation of Superlattice Domains in Ordering Alloys by DFTEM Tomography
This paper shows a technique to acquire a tilt series of dark-field transmission electron microscopy (DFTEM) images for superlattice domains formed in ordering alloys. Fundamental points are as follows 1) use of a superlattice reflection with a relatively long extinction distance (small structure factor) to satisfy the projection requirement and 2) careful realignment of the electron beam to keep the diffraction condition during tilting the specimen. Tomographic reconstruction from the obtained DFTEM tilt series visualizes three-dimensional morphology and distribution of the superlattice domains, demonstrating the feasibility of the DFTEM tomography.. |
| 160. |
Electron microscopy analysis of crack propagation behavior of alumina
Macroscopic features of crack propagation behavior in polycrystalline alumina (poly-alumina) and alumina single crystals (single-alumina) were analyzed by scanning electron microscopic electron back-scattered diffraction (SEM-EBSD) analysis. It was revealed that the intergranular fracture behavior is independent on grain boundary characters. When the cracks are propagated in the grains of poly- or single-alumina, zigzag cracks were produced. The zigzag cracks are composed of fracture surfaces formed along the cleavage planes. Microscopic features of fracture surfaces formed in a single-alumina were observed in detail by electron tomography combined with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). It was by visualized that the zigzag cracks were composed of flat and uneven fracture surfaces at a nm scale. The flat fracture surfaces and uneven ones were nearly parallel to the cleavage plane, {11̄02}, and the basal plane, {0001}, respectively. © 2008 MS&T'08®.. |
| 161. |
Analysis of grain boundary characteristics in polycrystalline MgB_2 bulks. |
| 162. |
透過型電子顕微鏡を用いた生体アパタイト結晶の成長と結晶軸配向化プロセスの観察. |
| 163. |
Three-Dimensional Imaging of Crystalline Microstructures Using Electron Tomography. |
| 164. |
Masaki Tanaka, Masaki Honda, Masatoshi Mitsuhara, Satoshi Hata, Kenji Kaneko, Kenji Higashida, Three-Dimensional Observation of Dislocations by Electron Tomography in a Silicon Crystal (vol 49, pg 1953, 2008), MATERIALS TRANSACTIONS, 10.2320/matertrans.E2008002, Vol.49, No.11, p.2753, 2008.11. |
| 165. |
Al‐Mg‐Si系合金板の微細組織に及ぼすSc,Zr複合添加の影響. |
| 166. |
Mg‐Al‐Ca系合金のクリープ変形挙動. |
| 167. |
10Cr‐1Mo‐V‐Nb鋼のクリープ強度におよぼす焼ならし・焼もどし温度の影響. |
| 168. |
HPT加工を施した純銅の微細組織のTEM/STEM観察. |
| 169. |
Mg‐Al‐Ca系ダイカスト合金のクリープ変形挙動. |
| 170. |
Sc,Zr複合添加を行ったAl‐Mg‐Si系合金板の微細組織. |
| 171. |
コイルばねクリープ試験法によるSUS304鋼のクリープ挙動解析. |
| 172. |
電子線トモグラフィーを用いたセラミックスの破面観察. |
| 173. |
電子線トモグラフィーによる金属材料中の転位組織の3次元可視化への試み. |
| 174. |
Haigui Yang, Dong Wang, Hiroshi Nakashima, Hongye Gao, Kana Hirayama, Ken-ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Influence of top surface passivation on bottom-channel hole mobility of ultrathin SiGe- and Ge-on-insulator, APPLIED PHYSICS LETTERS, 10.1063/1.2972114, Vol.93, No.7, p.72104, 2008.08, Bottom-channel hole mobility was examined by a pseudo-metal-oxide-semiconductor field-effect transistors method for ultrathin SiGe-on-insulator (SGOI) and Ge-on-insulator (GOI), which were fabricated using Ge condensation by dry oxidation. By comparing samples with and without a top SiO2 layer, we investigated the influence of top surface passivation on bottom-channel hole mobility. Mobility degradation was found in an ultrathin SGOI/ GOI layer without top SiO2 and became more serious with a decrease in the thickness of the SGOI/GOI layer, which strongly suggested that top surface passivation is necessary to evaluate accurate channel mobility. A 13-nm-thick GOI with passivation showed a high mobility value of 440 cm(2) / V s. (C) 2008 American Institute of Physics.. |
| 175. |
Mechanical Properties of Polycrystalline MgB_2 Bulk
Mechanical properties of superconducting MgB2 materials are important for their practical uses. This paper reports relationships between mechanical properties (Vickers hardness and fracture toughness) and the microstructure in MgB2 bulk materials. MgB2 bulk specimens were prepared by a Premix-PICT (powder in closed tube)-diffusion method. It was found that Vickers hardness and fracture toughness were improved up to about 1.5 times by co-doping with SiC and C10H8. It is interpreted that (i) the improvement of Vickers hardness by the co-doping is mainly due to reducing the MgB2 grain size, and (ii) the improvement of fracture toughness by the co-doping is mainly due to decreasing the amount of amorphous phases.. |
| 176. |
HATA Satoshi, SOSIATI Harini, YOSHIDOME Takeshi, Transmission Electron Microscopy Observation of MgB₂ Superconducting Materials with Inhomogeneous Microstructure : Influences of Specimen Preparation Methods, 九州大学大学院総合理工学報告, 10.15017/14600, Vol.30, No.1, pp.20-24, 2008.06, Transmission electron microscopy (TEM) observation of microstructure in MgB2 superconducting materials was carried out using different TEM specimen preparation methods. When a focused ion beam microsampling (FIB-MS) technique was applied to prepare thin foil specimens, TEM observation revealed inhomogeneous microstructure in MgB2 tapes fabricated by an in situ powder-in-tube (PIT) process: the microstructure composed of a densely crystallized MgB2 area, a partially crystallized area containing amorphous phases, micro-meter sized holes, etc. It was also revealed that doping with SiC in the PIT process makes distribution of the crystallized and partially crystallized areas uniform. On the other hand, when a conventional TEM specimen preparation, pulverizing the specimen into powders and thinning the powders with an Ar ion mill was performed, the microstructural characters of the MgB2 tapes described above were hardly recognized.. |
| 177. |
J_c-B characteristics of alternately-layered MgB_2/Ni thin films. |
| 178. |
Composition dependence on microstructure in MgB_2 film fabricated by electron beam evaporation. |
| 179. |
Mechanical properties of high density MgB_2 bulk. |
| 180. |
6111アルミニウム合金の集合組織形成とリジング発生の関係. |
| 181. |
Al‐Mg‐Si系合金の立方体方位粒形成過程. |
| 182. |
CeO2添加正方晶ZrO2多結晶体の応力誘起相変態における結晶方位関係と応力場. |
| 183. |
STEM回折コントラスト法による巨大ひずみ加工組織観察の試み. |
| 184. |
ラット内軟骨性骨化領域のTEM観察. |
| 185. |
高Crフェライト系耐熱鋼のクリープ強度とΩ値の関係. |
| 186. |
T. Doi, H. Kitaguchi, S. Hata, K. Fukuyama, K. Masuda, K. Takahashi, T. Yoshidome, Y. Hakuraku, N. Kuwano, Monotonic decrease of T(c)s with thinning of the superconducting MgB2 layer in MgB2/Ni and MgB2/B alternately-layered thin films, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 10.1088/0953-2048/20/12/023, Vol.20, No.12, pp.1223-1227, 2007.12, We prepared MgB2/Ni and MgB2/B alternately-layered films using electron beam evaporation and coaxial vacuum arc evaporation techniques without any post-annealing. The thickness of each MgB2 layer was designed to be 42, 24 or 15 nm for both MgB2/Ni and MgB2/B alternately-layered films. We confirmed that the layered structure was successfully obtained from the scanning transmission electron microscopic cross-sectional image of the MgB2/Ni alternately-layered film. The critical temperature, T-c, of the alternately-layered film decreased as the MgB2 layer became thinner, for both MgB2/Ni and MgB2/B films. Moreover, the Tc was affected by only the MgB2 layer thickness, and was independent of the inserted layer materials.. |
| 187. |
Electron Tomographic Observation of Precipitates on Lath Boundaries in 10Cr Ferritic Steel Bearing V. |
| 188. |
3D Observation of Dislocations in Si Single Crystal using a High-angle Triple-axis (HATA) Specimen Holder. |
| 189. |
Magnetic field dependences of J_c of MgB_2/B multilayered thin films. |
| 190. |
内軟骨性骨化領域のアパタイト生成と結晶配向の電子顕微鏡観察. |
| 191. |
組成を変化させて作製したMgB2+X薄膜の超伝導特性. |
| 192. |
Superconducting properties of MgB_ thin films prepared with various compositions. |
| 193. |
TEM observation of high-density MgB_2 bulk. |
| 194. |
The formation process of cube oriented grains in 6000 aluminum alloy. |
| 195. |
High temperature deformation mechanism of Mg-Al-Ca Die-cast alloys in low stress region. |
| 196. |
Si/SiGeヘテロ界面近傍の酸化濃縮プロセスに伴う微細構造変化. |
| 197. |
VおよびNb添加高Crフェライト系耐熱鋼の3次元電子線トモグラフィー観察. |
| 198. |
コイルばねクリープ試験によるSn‐Ag‐Cu合金の低応力下でのクリープ変形挙動の解析. |
| 199. |
金属間化合物材料のための電子線トモグラフィー技術の開発. |
| 200. |
Fe‐3 mass% Cu合金におけるCu粒子と転位の電子顕微鏡観察. |
| 201. |
N. Kuwano, M. Hijikuro, S. Hata, M. Takeuchi, Y. Aoyagi, TEM analysis of an interface layer formed by the anti-surfactant treatment on a GaN template, JOURNAL OF CRYSTAL GROWTH, 10.1016/j.jcrysgro.2006.10.188, Vol.298, pp.284-287, 2007.01, Transmission electron microscope (TEM) analysis was performed for the anti-surfactant (AS)-treated interface of GaN thin films deposited by the metal-organic vapor-phase epitaxy method. It was revealed that the AS-treatment with supplying a gas-source of tetraethyl-silicon (TESi) forms an interface layer of about I nm thickness. The electron diffraction pattern for the interface layer shows a streak along [0 0 0 1] at about one-thrid positions between hkil = 0 0 0 0 and (1) over bar2 (1) over bar0. The point analysis of energy dispersive X-ray spectroscopy (EDS) confirmed that the interface layer contains a certain amount of silicon. These results revealed that the interface layer is a crystalline phase of silicon compound. The effect of the interface layer on the morphology of threading dislocations was also discussed in terms of coherency of the interface layer with GaN. (c) 2006 Elsevier B.V. All rights reserved.. |
| 202. |
Microstructural characterization of whiskers and oxidized surfaceson Sn/FeNi42 and Pb-free alloys
Microstructural characterization was performed by analytical transmission electron microscopy (ATEM) to clarify the formation mechanism of tin whiskers. A tin (Sn)-layer about 10 μm thickness was electrodeposited on a FeNi42 plate. The Sn/FeNi42 plate was heated and cooled repeatedly in a temperature range of 233-403 K for 100 cycles under various atmospheres. Cross-sectional TEM specimens of whiskers on the Sn/FeNi42 plate were prepared using a focused ion beam (FIB) micro-sampling technique. Some artifact-effects of the FIB treatments on microstructures in tin alloys were taken into account. Bent-type whiskers grown on the Sn/FeNi42 are of polycrystalline β-Sn. A tin-oxide layer around 10 nm in thickness is formed on the tin surface. Electron diffraction, high-resolution TEM and electron energy loss spectroscopy (EELS) analyses revealed that the tin-oxide layer is predominantly of crystalline SnO 2. The presence of crystalline SnO was also recognized. It was found that the tin-oxide layer tends to be rather thin around stems of the whiskers. It is interpreted that thermal stress in the tin-layer breaks the thin tin-oxide layer at grain boundaries of tin and the whiskers grow from the broken area. The formation mechanism of the whiskers is discussed. © (2006) by the Electronic Components Industry Association (ECIA) All rights reserved.. |
| 203. |
SOSHIATY Harini, HATA Satoshi, YOSHIDOME Ken, TOMOKIYO Yoshihito, KUWANO Noriyuki, MATSUMOTO Akiyoshi, KITAGUCHI Hitoshi, KUMAKURA Hiroaki, Effect of ball-milling treatment on microstructure of in situ powder-in-tube MgB2 tape, 日本金属学会講演概要, Vol.138th, p.324, 2006.03. |
| 204. |
SOSHIATI Harini, HATA Satoshi, KUWANO Noriyuki, IWANE Yuichi, MORIZONO Yasuhiro, ONO Yasuhide, Transmission electron microscopy analysis of tin oxide on an Sn/FeNi42 solder material, 日本金属学会講演概要, Vol.138th, p.348, 2006.03. |
| 205. |
Kosuke Kimura, Takao Horiuchi, Satoshi Hata, Syo Matsumura, Tomographic dark-field TEM observation of ordered precipitates in a Ni-Mo alloy, 2006.02, A Ni-Mo alloy treated in a solution was annealed at 1073K for 24 hours to obtain a two-phase nanostructure. It is composed of the nickel matrix with a face-centered cubic (fcc) structure and Ni4Mo precipitates with a D1a body-centered tetragonal superstructure. When Ni4Mo precipitates are formed in the nickel matrix, six types of orientation relationships exist between the precipitates and the matrix. Its etchant was an electrolysis polishing solution with composition CH3OH : HSO4 = 3:1 and mthe magnification of the dark-field image was 26000X.. |
| 206. |
K Kimura, T Horiuchi, S Hata, S Matsumura, Tomographic dark-field TEM observation of ordered precipitates in a Ni-Mo alloy, ADVANCED MATERIALS & PROCESSES, Vol.164, No.2, pp.46-47, 2006.02, A Ni-Mo alloy treated in a solution was annealed at 1073K for 24 hours to obtain a two-phase nanostructure. It is composed of the nickel matrix with a face-centered cubic (fcc) structure and Ni4Mo precipitates with a D1a body-centered tetragonal superstructure. When Ni4Mo precipitates are formed in the nickel matrix, six types of orientation relationships exist between the precipitates and the matrix. Its etchant was an electrolysis polishing solution with composition CH3OH : HSO4 = 3:1 and mthe magnification of the dark-field image was 26000X.. |
| 207. |
H Sosiati, S Hata, N Kuwano, Y Tomokiyo, H Kitaguchi, T Doi, H Yamamoto, A Matsumoto, K Saitoh, H Kumakura, Relationship between microstructure and J(c) property in MgB2/alpha-Al2O3 film fabricated by in situ electron beam evaporation, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 10.1088/0953-2048/18/10/005, Vol.18, No.10, pp.1275-1279, 2005.10, A transmission electron microscopy (TEM) study has been carried out on an MgB2/alpha-Al2O3 film that exhibits the typical property of critical current density (J(c)) under magnetic fields. The MgB2 layer of 300 nm in thickness was grown on a (001)alpha-Al2O3 substrate using an in situ electron beam evaporation method. J(c) of the film takes significantly high values when the applied magnetic field is perpendicular to the film surface. The MgB2 layer consists of fine columnar MgB2 crystals 20-30 nm in size. The columnar MgB2 crystals grow almost perpendicular to the substrate surface and have no crystallographic orientation relationship with the alpha-Al2O3 substrate because of an amorphous layer formed first on the substrate. A high density of columnar grain boundaries within the MgB2 layer may be effective for the enhancement of the flux-pinning under the perpendicular magnetic field.. |
| 208. |
BT Hang, T Watanabe, M Eashira, S Okada, J Yamaki, S Hata, SH Yoon, Mochida, I, The electrochemical properties of Fe2O3-loaded carbon electrodes for iron-air battery anodes, JOURNAL OF POWER SOURCES, 10.1016/j.jpowsour.2005.02.028, Vol.150, pp.261-271, 2005.10, The redox efficiency of iron has been improved by increasing the distribution of iron on the carbon surface with Fe2O3-loaded carbon materials. The Fe2O3-loaded carbon material was prepared by loading Fe2O3 on carbon by a chemical method. Fe(NO3)(3) was impregnated on carbon with different weight ratios of iron-to-carbon in an aqueous solution, and the mixture was dried and then calcined for 1 h at 400 degrees C in flowing Ar. The effect of various carbons on the physical and electrochemical properties of Fe2O3-loaded carbon electrodes was investigated with the use of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) along with X-ray energy-dispersive spectroscopy (EDS), cyclic voltammetry (CV) and galvanostatic cycling performance. Transmission electron microscopy coupled with X-ray diffraction measurements revealed that small Fe2O3 particles were distributed on the carbon surface. Natural graphite and several nano-carbon materials such as acetylene black and tubular carbon nanofibers (tubular CNF) exhibited improved characteristics, such as enhanced capacity and higher redox currents for the Fe2O3-loaded carbon electrode. SEM and EDS results suggest that Fe2O3-loaded nano-carbon electrodes, due to the large surface area of the nano-carbon, have more Fe2O3 dispersed than on Fe2O3-coated graphite electrodes. (c) 2005 Elsevier B.V. All rights reserved.. |
| 209. |
HANG Bui Thi, EGASHIRA Minato, WATANABE Izumi, HATA Satoshi, OKADA Shigeto, YAMAKI Jun‐ichi, YOON Seong‐Ho, Electrochemical properties of Fe2O3-Nano-Loaded Carbon and Fe2O3-Nano/Carbon Mixed Composites for Iron-Air Battery Anodes, 九州大学大学院総合理工学報告, 10.15017/16756, Vol.27, No.1, pp.1-8, 2005.07, In order to find the adequate material for Fe/air battery anode，two kinds of materials，Fe_2O_3-nano-loaded carbon and Fe_2O_3-nano mixed carbon material using various carbon materials, were prepared．The Fe_2O_3-nano-loaded carbon material was prepared by loading Fe_2O_3 on carbon using a chemical method．Fe(NO3)3 was impregnated on carbon with different weight ratios of iron to carbon in an aqueous solution，and the mixture was dried and then calcined for 1 h at 400℃ in flowing Ar．For the Fe_2O_3-nano mixed carbon material, Fe_2O_3-nano powder was mixed with carbon by mechanical method. The effect of various carbons on the physical and electrochemical properties of both Fe_2O_3-nano-loaded carbon and Fe_2O_3-nano mixed carbon electrodes was investigated and compared using X-ray diffraction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM) along with X-ray energy-dispersive spectroscopy(EDS), cyclic voltammetry(CV) and galvanostatic cycling performance．Transmission electron microscopy(TEM) coupled with X-ray diffraction measurements revealed that Fe_2O_3-nanoparticles were distributed on the carbon surface for Fe_2O_3-nano-loaded carbon．This distribution is similar to that for Fe_2O_3-nano mixed carbon electrodes observed by SEM and EDS．The CV results indicated that the redox currents of the Fe_2O_3-nano-loaded carbon are larger than that of correspondence Fe_2O_3-nano mixed carbon．Such properties are expected to provide the larger capacity for Fe_2O_3-nano-loaded carbon electrode than Fe_2O_3-nano mixed carbon electrode.. |
| 210. |
S Hata, H Sosiati, N Kuwano, Y Tomokiyo, A Matsumoto, M Fukutomi, H Kitaguchi, K Komori, H Kumakura, Effects of heat treatments on microstructure formation in MgB2/YSZ/Hastelloy film, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2005.848834, Vol.15, No.2, pp.3238-3241, 2005.06, Annealing processes in MgB2 films deposited on yttria-stabilized zirconia (YSZ)-buffered Hastelloy substrates were studied by transmission electron microscopy. The MgB2, films with Mg-rich compositions were fabricated at room temperature using a pulsed laser deposition (PLD) method. The as-deposited films do not exhibit clear superconducting transitions, and have inhomogeneous microstructures composed of amorphous regions and a small amount of crystalline MgB2 and MgO with several tens of nm in size. Various sizes of voids are also incorporated within the amorphous regions. After the annealing at 600 or 680 degrees C, the films exhibit clear superconducting transitions. The amorphous regions crystallize into fine grains of MgB2 or MgO 5-50 nm in size. The voids remain in the annealed films and their sizes depend on the annealing condition. Magnesium-and oxygen-rich layers are formed near the MgB2/YSZ interface and the film surface. It is suggested that the finer grains of MgB2 and MgO obtained by the lower-temperature annealing give a larger critical current density under a high magnetic field.. |
| 211. |
H Kitaguchi, T Doi, Y Kobayashi, A Matsumoto, H Sosiati, S Hata, M Fukutomi, H Kumakura, Properties of MgB2 films with very high transport critical current densities, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2005.848866, Vol.15, No.2, pp.3313-3316, 2005.06, Magnesium diboride, MgB2, thin films are fabricated through two different kinds of process. One is an in-situ process by using electron beam deposition and the other is an ex-situ process by using the combination of pulsed laser deposition and heat treatment. The critical current density, J(c), is investigated as a function of external magnetic field in the range of 0-7 T and/or temperatures ranging from 4.2 K to the critical temperature by using dc 4-probe transport method. The in-situ processed film shows very high J(c), e.g., 7.1 x 10(6), 1.2 x 10(6), and 1.4 x 10(5) A/cm(2) in 0, 4, and 7 T (perpendicular fields), respectively. Angular dependence of J(c) is much different between the two kinds of films. J(c)-angle (magnetic field) curves of the in-situ processed film show two peaks; one is around the field perpendicular to the film surface and the other is around the parallel field. On the contrary, the curves of the ex-situ. processed film have only one peak around the parallel field. Microstructure analyses show that the in-situ film has columnar grains aligned perpendicular to the film surface and that the ex-situ one has granular grains with random orientations. These results indicate that the grain boundaries between columnar grains act as effective pinning centers and enhance J(c) in the perpendicular fields.. |
| 212. |
S Fujino, H Tokunaga, S Hata, E Saiz, AP Tomsia, Graded glass coatings for Co-Cr implant alloys, JOURNAL OF MATERIALS SCIENCE, 10.1007/s10853-005-1982-z, Vol.40, No.9-10, pp.2499-2503, 2005.05, A graded glass coating for Vitallium (R), a Co-Cr alloy, has been prepared using a simple enameling technique. The composition of the glasses has been tailored to match the thermal expansion of the alloys. The optimum glass composition and firing conditions (temperature and time) needed to fabricate homogeneous coatings with good adhesion to the alloy were determined. The final coating thickness ranged between 25 and 60 mu m. Coatings fired under optimum conditions do not delaminate during indentation tests of adhesion. Excellent adhesion to the alloy has been achieved through the formation of 100 nm thick interfacial chromium-oxide (CrOx) layers. The graded glass (consisting of BIG and 6P50 layers) can be successfully coated to a Co-Cr alloy, and forms hydroxyapatite (HA) on the coating surface when immersed in a simulated body fluid (SBF) for 30 days. (C) 2005 Springer Science + Business Media, Inc.. |
| 213. |
S Hata, K Shiraishi, M Itakura, N Kuwano, T Nakano, Y Umakoshi, Long-period ordering in a TiAl single crystal with a gradient composition, PHILOSOPHICAL MAGAZINE LETTERS, 10.1080/09500830500157462, Vol.85, No.4, pp.175-184, 2005.04, A series of long-period superstructures (LPSs) formed in an Al-rich TiAl single crystal with a gradient composition has been observed by transmission electron microscopy. A Ti-54.7 at.% Al single crystal was heat treated within molten Al at 1234 degrees C, and a composition-gradient layer with an Al concentration from 55 to 75 at.% was formed at the surface of the single crystal. The composition-gradient layer exhibits ordering into different LPSs depending on the Al concentration as follows: short-range order, h-Al2Ti and one-dimensional antiphase domain structure. These LPSs have an alternate stacking of Al(002) and Ti-Al(002) layers and the ordering of the LPSs proceeds in the TiAl matrix, maintaining an orientation relationship in which Al(002) layers of the LPSs and the TiAl matrix are parallel to each other. The ordering of this type of LPS and the phase transition between these LPSs are thus interpreted as structural changes in Ti(002) layers of the Al-rich TiAl crystal. It was also observed that ordering of the orthorhombic h-Al2Ti exhibits anisotropic features depending on the direction of the composition gradient.. |
| 214. |
ソシアティ ハリニ, HATA Satoshi, YOSHIDOME Ken, TOMOKIYO Yoshiji, KUWANO Noriyuki, MATSUMOTO Akiyoshi, HATAKEYAMA Hideo, KITAGUCHI Hitoshi, KUMAKURA Hiroaki, Effect of nano-SiC doping on microstructure of in situ powder-in-tube MgB2 tape, 日本金属学会講演概要, Vol.136th, p.380, 2005.03. |
| 215. |
ソシアティ ハリニ, HATA Satoshi, TOMOKIYO Yoshiji, KUWANO Noriyuki, MATSUMOTO Akiyoshi, FUKUTOMI Katsuo, KITAGUCHI Hitoshi, DOI Toshiya, Microstructures of MgB2 Superconducting Films Fabricated by in situ EB and ex situ PLD Techniques, 日本金属学会講演概要, Vol.136th, p.379, 2005.03. |
| 216. |
ISHIMARU M, HIROTSU Y, HATA S, MA C, NISHIYAMA N, AMIYA K, INOUE A, Structural characterization of Cu–Ti-based bulk metallic glass by advanced electron microscopy, Philosophical Magazine Letters, 10.1080/09500830500153776, Vol.85, No.3, pp.125-133, 2005.03, The atomistic structure of a high-strength Cu42.5Ti41.5Ni7.5Zr2.5Hf5Si1 bulk metallic glass prepared by copper-mould casting has been characterized by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). High-resolution TEM and high-angle annular dark-field observations revealed that crystalline nanoparticles with sizes less than 10?nm are embedded in an amorphous matrix. It was confirmed by energy-dispersive X-ray spectroscopy in combination with STEM that these nanoparticles possess higher copper content than the amorphous matrix. Nanobeam electron diffraction experiments indicated that their crystalline structure is basically face-centred cubic with ordered atomic arrangements.. |
| 217. |
SOSIATI H, HATA S, KUWANO N, TOMOKIYO Y, MATSUMOTO A, FUKUTOMI M, KITAGUCHI H, KOMORI K, KUMAKURA H, Electron microscopy of MgB2 thin film on YSZ-buffered Hastelloy（jointly worked）, Physica C, 10.1016/j.physc.2004.01.168, Vol.412, No.Pt.2, pp.1376-1382, 2004.10, In order to understand the relationship between the microstructures and superconducting properties of MgB2films, analytical TEM observations have been carried out. The films were fabricated by a KrF excimer laser deposition on Hastelloy substrates precoated with YSZ (yttria-stabilized zirconia). The deposited films were annealed under Ar atmosphere at 873 K for 1 h and at 953 K for 0.5 h. The critical current densities of these films were measured to be Jc=1×105A/cm2and Jc=7.7×103A/cm2at 4.2 K and 10 T, respectively. The conventional TEM observation showed nanocrystalline MgB2and MgO of 5-30 nm in size dispersed in the films. Voids with various sizes from 10 to 60 nm were also observed in the films. Two-dimensional elemental analyses exhibited that near the MgB2/YSZ interface the films have a layered structure where the layers enriched with Mg and O have low B concentrations complementarily. The average sizes of the MgB2and MgO grains and the voids increase with the annealing temperature. The enhancement of Jcvalue of the film annealed at 873 K may be due to smaller sizes of the MgB2and MgO grains and voids than those at 953 K. © 2004 Elsevier B.V. All rights reserved.. |
| 218. |
KITAGUCHI H, MATSUMOTO A, KUMAKURA H, DOI T, YAMAMOTO H, SAITOH K, SOSIATI H, HATA S, MgB2 films with very high critical current densities due to strong grain boundary pinning（jointly worked）, Applied Physics Letters, 10.1063/1.1805195, Vol.85, No.14, pp.2842-2844, 2004.10, The production of critical current density (Jc) by 20-30 nm diameter columnar grains of MgB2was analyzed. It was observed that 20-30 nm diameter columnar grain structure produced Jcexceeding 5×106A/cm2. It was also observed that strongest pinning ocurred when the field was aligned parallel to the grain boundaries. The results show that grain boundaries in MgB2do not obstruct current flow as in the high-temperature cuprate superconductors, but act like those in intermetallic superconductors such as Nb3Sn.. |
| 219. |
Microstructure of MgB2 films deposited on YSZ/Hastelloy substrate
Microstructures of MgB2 films on yttria-stabilized-zirconia (YSZ)/Hastelloy substrates were studied by analytical transmission electron microscopy. The MgB2 films with Mg- rich compositions were fabricated by pulsed laser deposition followed by annealing at 600degreesC or 680degreesC under Ar atmosphere. Fine grains of MgB2 and MgO crystals 5-30 nm in size that shows a good mutual connectivity are formed in the MgB2 films. The MgB2 films also form voids 5-100 nm in size that may contain amorphous or oxide phases. Two-dimensional elemental analyses revealed that Mg and O atoms are enriched near the MgB2/YSZ interface. From a comparison in microstructures between the 600degreesC- and 680degreesC-annealed MgB2 films, it is suggested that the films composed of finer grains of MgB2 exhibit a higher critical current density under high magnetic fields.. |
| 220. |
Atomistic structure of short-range order state in alloys, S. Hata and S. Matsumura, Journal of the Japan Society of Crystals, 44, 225 (2002). (Japanese). |
| 221. |
HATA S, HIGUCHI K, ITAKURA M, KUWANO N, NAKANO T, HAYASHI K, UMAKOSHI Y, Short-range order in Al-rich gamma-TiAl alloys studied by high-resolution transmission electron microscopy with image processing（jointly worked）, Phil. Mag. Lett., 10.1080/09500830210137425, Vol.82, No.7, pp.363-372, 2002.07, The atomic arrangements of short-range order (SRO) in two Al-rich γ-TiAl alloys with 62.5 and 60.0 at.% Al respectively have been investigated by high-resolution transmission electron microscopy with image processing. For both alloys, SRO structures are formed in Ti-rich (002) layers of the Ll0ordered γTiAl matrix, in the course of the phase transformation from the Al5Ti3long-period superstructure phase at lower temperatures to the h-Al2Ti phase at higher temperatures. The SRO structures are composed of three types of ordered cluster: Ti4Al type (square shaped), Ti3Al type (fat rhombus shaped) and Ti2Al type (lean rhombus shaped). The ordered clusters form local microdomains of the Al5Ti3and Al3Ti2superstructures in addition to the Al5Ti3and h-Al2Ti superstructures, by different methods of tiling the ordered clusters. Such ordered clusters or microdomains tend to be in contact with each other through common (310) boundaries. This results in peculiar diffuse streaks in diffraction connecting intensity maxima arising from the long-period superstructures.. |
| 222. |
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-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 10.1016/S0921-5093(00)01872-4, Vol.312, No.1-2, pp.160-167, 2001.08, Modern high resolution transmission electron microscopy was employed in study of short range order (SRO) in fcc-based Ni-Mo, which is classified as '1 1/2 0 alloy'. Digital processing of high resolution transmission electron microscope (HRTEM) images can give information about local atomic arrangements of SRO as well as their projection views. The HRTEM observation with image processing reveals the SRO structures in Ni-Mo depending upon the alloy composition and the heat treatment. Subunit cell clusters of D1(a), D0(22) and Pt2Mo structures are generated in the SRO states of Ni4Mo and Ni3Mo alloys. In the initial SRO states, the number of Pt2Mo type clusters increases with Mo composition while that of D1(a) type decreases. The D1(a), D0(22) and Pt2Mo type clusters increase in number in the early stages of subsequent ordering. The formation of D1(a), D0(22) and Pt2Mo type clusters in the SRO states is rationalized in terms of the similar tendencies in atomic configuration between D1(a), D0(22) and Pt,Mo structures. (C) 2001 Elsevier Science B.V. All rights reserved.. |
| 223. |
Asia Pacific Conference of Electron Microscopy 7th APEM, S. Hata, Electron Microscopy, 36, 75 (2001). (Japanese). |
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S Hata, D Shindo, T Mitate, N Kuwano, S Matsumura, K Oki, HRTEM image contrast of short range order in Ni4Mo, MICRON, 10.1016/S0968-4328(99)00134-1, Vol.31, No.5, pp.533-538, 2000.10, The high resolution transmission electron microscope (HRTEM) imaging of short range order (SRO) in Ni4Mo was investigated by means of multi-slice image simulations. The HRTEM images of Ni4Mo exhibit locally bright dot patterns corresponding to the [001] projections of the N2M2-type (chalcopyrite-like) structure. The multi-slice simulations revealed that the N2M2 patterns are rationalized as the projection patterns of the SRO structure which consists of subunit cell clusters of D1(a), D0(22) and Pt2Mo structures. The N2M2-type image contrast appears when both the fundamental fee lattice reflections and the 1 1/2 0 diffuse scattering of SRO contribute enough to imaging. This suggests that a good coincidence in intensity distribution between the Fourier power spectra of HRTEM images and the electron diffraction patterns is one of the conditions for the image contrast of SRO to be interpreted in terms of the projection contrast. (C) 2000 Elsevier Science Ltd. All rights reserved.. |
| 225. |
Analysis of characteristic X-ray intensities in ALCHEMI of ordered aluminum alloys. |
| 226. |
HRTEM image contrast of short range ordered Ni-Mo obtained by FETEM. |
| 227. |
N Tanaka, N Suzuki, M Kawasaki, S Hata, N Kuwano, K Oki, High-angle annular dark-field STEM of partially ordered Ni-19.5at%Mo alloys, JOURNAL DE PHYSIQUE IV, Vol.10, No.P6, pp.85-90, 2000.04, Atomic structures of partially ordered Ni-19.5at%Mo alloys are, for the first lime, studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The small ordered regions with a D1a structure are clearly visualized as the square-arrangement of bright dots corresponding to the Mo-atomic columns in the dark background due to the disordered matrix with a fee structure. The variation of the image contrast, where the D1a structure is visualized with high contrast in overfocused conditions from the Scherzer defocus, is observed, which is interpreted by using the approximate imaging theory by Jesson et al.(Proc.Roy.Soc.Lond.,441A('93) 261) and the size-variation of the probe. The imaging theory for the HAADF-STEM of short-range ordered state in binary alloys is formulated. where the dynamical diffraction effect is reduced in comparison with that for transmission electron microscopy(TEM).. |
| 228. |
N Tanaka, N Suzuki, M Kawasaki, S Hata, N Kuwano, K Oki, High-angle annular dark-field STEM of partially ordered Ni-19.5at%Mo alloys, JOURNAL DE PHYSIQUE IV, Vol.10, No.P6, pp.85-90, 2000.04, Atomic structures of partially ordered Ni-19.5at%Mo alloys are, for the first lime, studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The small ordered regions with a D1a structure are clearly visualized as the square-arrangement of bright dots corresponding to the Mo-atomic columns in the dark background due to the disordered matrix with a fee structure. The variation of the image contrast, where the D1a structure is visualized with high contrast in overfocused conditions from the Scherzer defocus, is observed, which is interpreted by using the approximate imaging theory by Jesson et al.(Proc.Roy.Soc.Lond.,441A('93) 261) and the size-variation of the probe. The imaging theory for the HAADF-STEM of short-range ordered state in binary alloys is formulated. where the dynamical diffraction effect is reduced in comparison with that for transmission electron microscopy(TEM).. |
| 229. |
Imageing theory for HAADF-STEM of disorderred Ni_4Mo alloys. |
| 230. |
High-angle annular dark-field STEM of partially ordered Ni-19.5at%Mo alloys
Atomic structures of partially ordered Ni-19.5at%Mo alloys are, for the first time, studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The small ordered regions with a D1a structure are clearly visualized as the square-arrangement of bright clots corresponding to the Mo-atomic columns in the dark background due to the disordered matrix with a fcc structure. The variation of the image contrast, where the D1a structure is visualized with high contrast in overfocused conditions from the Scherzer defocus, is observed, which is interpreted by using the approximate imaging theory by Jesson et al. and the size-variation of the probe. The imaging theory for the HAADF-STEM of short-range ordered state in binary alloys is formulated, where the dynamical diffraction effect is reduced in comparison with that for transmission electron microscopy (TEM).. |
| 231. |
Dependence of measurement conditions on characteristic X-ray intensity in ALCHEMI for B2-type ordered Ti-Al-Mo alloys. |
| 232. |
HRTEM image simulations of short range order in Ni_4Mo. |
| 233. |
HAADF-STEM Observation of Quenched N-19.5at%Mo Alloy. |
| 234. |
S Hata, D Shindo, N Kuwano, S Matsumura, K Oki, Interpretation of high resolution transmission electron microscope images of short range ordered Ni4Mo, MATERIALS TRANSACTIONS JIM, 10.2320/matertrans1989.39.914, Vol.39, No.9, pp.914-919, 1998.09, High resolution transmission electron microscope (HRTEM) image contrast of short-range order (SRO) in Ni4Mo alloys has been investigated by means of multi-slice simulations. The HRTEM image contrast of SRO in Ni4Mo coincides with a projection contrast of an SRO structure which involves D1(a), D0(22) and Pt2Mo-type subunit cells in a disordered matrix. Multi-slice simulations revealed that the SRO structure exhibit a projection contrast in the HRTEM Image when the fundamental fee lattice reflections contribute sufficiently to HRTEM imaging. The results indicate that the image of SRO in Ni4Mo can be interpreted in terms of projected potential of atomic columns under an appropriate imaging condition.. |
| 235. |
S Hata, S Matsumura, N Kuwano, K Oki, D Shindo, Short range order in Ni4Mo and its high resolution electron microscope images, ACTA MATERIALIA, 10.1016/S1359-6454(98)00180-3, Vol.46, No.14, pp.4955-4961, 1998.09, The short range ordered (SRO) structure in Ni4Mo has been investigated by means of high resolution transmission electron microscopy with digital image processing and Monte Carlo simulation. High resolution transmission electron microscope (HRTEM) images were recorded with an Imaging Flare (IP) system. Conventionally printed images of the SRO state exhibit locally dot patterns corresponding to N2M2-type (chalcopyrite-like) structure. However, the dot patterns transform into those of subunit cell clusters of D1(a), D0(22) and Pt2Mo structures, when the image is output with a different gray scale. The Monte Carlo simulation with appropriate interaction parameters of atoms has explained successfully the HRTEM images. It is concluded that the SRO state in Ni4Mo involves subunit cell clusters of D1(a), D0(22) and Pt2Mo structures in the atomistic level of microstructure. The concept of [1 1/2 0]* static concentration waves corresponding to the N2M2 pattern is rationalized as a mesoscopically averaging view of the SRO state. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.. |
| 236. |
S Hata, H Fujita, CG Schlesier, S Matsumura, N Kuwano, K Oki, Monte Carlo study of ordering processes in fcc-based Ni-Mo alloys, MATERIALS TRANSACTIONS JIM, 10.2320/matertrans1989.39.133, Vol.39, No.1, pp.133-138, 1998.01, The Monte Carlo simulations were carried out to clarify the ordering mechanisms in fee-based Ni-Mo alloys of Ni4Mo, Ni3Mo and Ni2Mo. When the pairwise atomic interactions up to the eighth coordinate shells are taken into account, the simulation results are consistent with the experimental changes in electron diffraction pattern during the ordering processes in Ni4Mo, Ni3Mo and Ni2Mo alloys. In the early stage of ordering, subunit cell clusters of D1(a), D0(22) and Pt2Mo structures are first generated to form the short range ordered (SRO) state. The selective growth of stable D1(a) and/or Pt2Mo-type ordered domains is involved in the transition to the long range ordered (LRO) state in the following stage.. |
| 237. |
S Hata, S Matsumura, N Kuwano, K Oki, Short range order and its transformation to long range order in Ni4Mo, ACTA MATERIALIA, 10.1016/S1359-6454(97)00314-5, Vol.46, No.3, pp.881-892, 1998.01, The short range ordered (SRO) state and the time-evolution of the long range ordered (LRO) structure of D-1a in a Ni4Mo alloy were investigated by Monte Carlo simulation based on an f.c.c. Ising model and by transmission electron microscopy (TEM). The simulation using appropriate values for pair wise atomic interactions up to the fifth nearest neighbors bears diffuse intensity maxima at {1 1/2 0} positions in the Fourier power spectrum for the early stage of SRO, and then the maxima shift to {4/5 2/5 0} for the stable D1(a) structure as the long range ordering proceeds. The present results are in good agreement with the temporal change in electron diffraction due to the SRO-LRO transition in a quenched Ni4Mo. The SRO state obtained in the simulation contains microclusters of subunit cells of D1(a), DO22 and Pt2Mo structures. If such a mixed state of microclusters is projected onto a two-dimensional {100} plane in a similar way to high resolution TEM, the mixed stale exhibits locally a dot-pattern analogous to the projected N2M2-type (chalcopyrite-like) structure, which gives rise to superlattice reflections at {1 1/2 0}. This suggests that a statistically averaging view of the mixture of microclusters leads to the concept of. static concentration waves of k = 1 1/2 0, which has been often employed to describe the SRO state. The formation of DO22 and Pt2Mo-type subunit cells in addition to stable D1, is explained in terms of their structural relationship. The transformation from SRO to LRO is attributed to continuous growth of D1,segments into ordered domains. (C) 1998 Acta Metallurgica Inc.. |
| 238. |
M ITAKURA, Y HISATSUNE, H SATO, N KUWANO, K OKI, CRYSTAL-STRUCTURES OF H-PD5CE AND PD5LA AND THEIR ELECTRICAL RESISTIVITIES AT LOW-TEMPERATURES, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Vol.27, No.4, pp.684-685, 1988.04, the crystal structure ofPd_5La was analyzed be powder X-ray diffraction and electron microscopy, and it was found that Pd_5La is almost isomorphic with H-Pd_5Ce. The electrical resistivity was examined for Pd_5La, H-Pd_5Ce and L-Pd_5Ce in the range between 77 K and 300 K. The temperature dependence of resistivity suggested that H-Pd_5Ce and L-Pd_5Ce have a dense Kondo state.. |
