吉井 賢資; 池田 直*
Journal of Alloys and Compounds, 804, p.364 - 369, 2019/10
伊覇 航*; 垣花 将司*; 松田 進弥*; 本多 史憲*; 芳賀 芳範; 竹内 徹也*; 中島 美帆*; 天児 寧*; 郷地 順*; 上床 美也*; et al.
Journal of Alloys and Compounds, 788, p.361 - 366, 2019/06
Ferromagnetic ordering of EuCuP is investigated on a single crystal sample grown from tin flux. Application of hydrostatic pressure up to 8 GPa stabilizes ferromagnetic ordering, suggesting divalent Eu is stable. The Hall effect and resistivity measurements show that EuCuP is a low-carrier ferromagnetic metal with a characteristic resistivity cusp appearing at the ferromagnetic transition temperature.
西村 克彦*; 松田 健二*; Lee, S.*; 布村 紀男*; 島野 寛基*; Bendo, A.*; 渡邊 克己*; 土屋 大樹*; 並木 孝洋*; 戸田 裕之*; et al.
Journal of Alloys and Compounds, 774, p.405 - 409, 2019/02
Temperature and time dependences of magnetization of Al-1.0%Zn-4.2%Mg, Al-2.6%Zn-3.2%Mg, Al-4.1%Zn-1.1%Mg, and Al-5%Zn (at.%) alloys were measured in the range between 10 and 310 K after various periods of natural aging and peak-aged heat treatments. Enhanced diamagnetic contributions on the magnetization were observed for the as-quenched Al-Zn-Mg alloys for the first time. The enhanced diamagnetism observed in Al-2.6%Zn-3.2%Mg and Al-4.1%Zn-1.1%Mg were found to largely alter in natural aging, while that of Al-1.0%Zn-4.2%Mg little changed. After peak-aged heat treatments, the diamagnetism of Al-Zn-Mg was largely reduced. The binary Al-5%Zn showed neither enhanced diamagnetism nor natural aging effect on the magnetization. Isothermal time variations of magnetization of Al-Zn-Mg alloys at 300 K were found to be related with solute-vacancy clustering.
茂呂 拓哉*; Kim, J.*; 山中 暁*; 村山 一郎*; 加藤 孝典*; 中山 忠親*; 武田 雅敏*; 山田 昇*; 西畑 保雄; 福田 竜生; et al.
Journal of Alloys and Compounds, 768, p.22 - 27, 2018/11
Relaxor-based ternary Pb(InNb)O-Pb(MgNb)O-PbTiO (PIN-PMN-PT) ceramics near a morphotropic phase boundary were grown, and their electrical properties at various temperatures were investigated in the electrothermodynamic cycle for the future environment-friendly automotive applications. Structural disordering, depending on the PIN content, influenced the diffuse phase transition between the tetragonal and cubic structures and contributed to the power-generating behavior. The net power-generating energies (P) were 2.43-3.01 mW/cm at temperatures above 200C and were maintained at above 1 mW/cm over a temperature range of approximately 100 degrees. Therefore, the PIN-PMN-PT system has a possibility of a wider usage temperature range, the disordering of the perovskite crystal structure can be controlled, and it will be a candidate for the application of pyroelectric energy conversion system.
細川 伸也*; 木村 耕治*; 山崎 倫昭*; 河村 能人*; 吉田 亨次*; 乾 雅祝*; 筒井 智嗣*; Baron, A. Q. R.*; 川北 至信; 伊藤 晋一*
Journal of Alloys and Compounds, 695, p.426 - 432, 2017/02
Inelastic X-ray scattering (IXS) was performed on polycrystalline MgZnY and MgZnY alloys with synchronized long-period stacking ordered (LPSO) phase for investigating the impurity effects in the microscopic elastic properties. Inelastic neutron scattering (INS) was also carried out on the former alloy. LA modes were clearly observed in the IXS spectra of both the LPSO alloys, while TA modes can mainly be detected in the second Brillouin zone. Broader inelastic signals and larger quasielastic peaks are characteristic due to the phonon scattering by the Zn/Y impurities. Only the TA excitation energies increase by adding the impurities, which indicates a harder stiffness of the bond angles relating to the L1-type clusters in the LPSO alloys. New dispersion-less excitation modes are observed at about 10 meV by adding the Zn/Y impurities. By comparing with the INS data, the contributions of the impurities to these excitations are discussed using differences in the scattering cross-sections between neutrons and X-rays.
遠藤 成輝*; 齋藤 寛之; 町田 晃彦; 片山 芳則
Journal of Alloys and Compounds, 645(Suppl.1), p.S61 - S63, 2015/10
We investigated the hydrogenation of the 1-type AlNi alloy at 3 GPa and 500C using in situ synchrotron radiation X-ray diffraction measurements. An isotropic lattice expansion was observed to have occurred owing to the hydrogenation, and a novel hydride (AlNiH) was formed. Because of such isotropic lattice expansion, the hydrogen-occupied sites were the body-center sites of the 1 structure (P-3). In this case, the hydrogen content was calculated to be = 1.0, which is consistent with the experimental results. The AlNiH hydride was stable under ambient conditions.
金 宰煥; 中道 勝
Journal of Alloys and Compounds, 640, p.285 - 289, 2015/08
Beryllium intermetallic compounds (beryllides) such as BeTi and BeV are the most promising advanced neutron multipliers in demonstration power reactors. We developed a new combined plasma sintering and rotating electrode method for the fabrication of beryllide rods and pebbles. Previously, we prepared a beryllide pebble with a Be-7.7 at.% Ti composition as the stoichiometric value of the BeTi phase; however, BeTi and Be phases were present along with the BeTi phase that formed as the result of a peritectic reaction due to re-melting during granulation using the rotating electrode method. This Be phase was found to be highly reactive with oxygen and water vapor. Accordingly, to investigate the Be phase reduction and applicability for fabrication of electrodes prior to granulation using the rotating electrode method, Be-Ti-V ternary beryllides were synthesized using the plasma sintering method. Surface observation results indicated that increasing plasma sintering time and V addition led to an increase in the intermetallic compound phases compared with plasma-sintered beryllide with a Be-7.7 at.% Ti composition. Additionally, evaluation of the reactivity of samples with water vapor at high temperature revealed that specimens with larger fractions of Be phases experienced larger weight gains and H generation rates because of oxidation, as BeTi and BeV phases have a similar oxidation tendency.
金 宰煥; 中道 勝
Journal of Alloys and Compounds, 638, p.277 - 281, 2015/07
Niobium and vanadium-beryllium intermetallic compounds (beryllides) were synthesized by plasma sintering under different sintering times at 1273 K. The beryllide with 7.7 at.% Nb mainly consisted of various phases of Be, BeNb, BeNb, and BeNb, whereas that with 7.7 at.% V consisted of BeV, BeV, and V. As the sintering time increased, area fractions of the target compositions BeNb and BeV increased while that of Be decreased. A comparative analysis demonstrated that the beryllide with 7.7 at.% Nb a showed higher density as well as a greater hardness than that with 7.7 at.% V, due to there being less difference between the sintering temperature and the melting point. In terms of thermal phase stability, the beryllide with 7.7 at.% Nb showed good thermal phase stability with fewer pores and a smaller unhomogenized area, because the beryllide contained a smaller area fraction of the Be phase, which may cause evaporation resulting in pore formation.
金 宰煥; 中道 勝
Journal of Alloys and Compounds, 585, p.63 - 68, 2014/02
Beryllide is well-known as the most promising candidate for advanced multipliers in demonstration fusion reactors. However, due to its brittleness, it is difficult to fabricate a pebble-type beryllide. Here, we report the synthesis and analysis of beryllide pebbles with different chemical compositions. In order to clarify the effect of the content of Ti on the fabrication of beryllide pebbles, a rotating electrode method was applied using a plasma-sintered beryllide rod jointed by two beryllide blocks and powder. The beryllide pebbles were successfully fabricated accompanied by phase changes induced by re-melting during the rotating electrode method. The SEM images of the rods and the cross-section of the pebbles demonstrated that the phases of the plasma-sintered beryllide rods with 6 at.%, 7 at.%, and 7.7 at.% Ti were transformed to the peritectic BeTi phase with a BeTi phase due to re-melting whereas pebbles with 3 at.% and 5 at.% Ti showed similar phases as the plasma-sintered beryllide rods. Additionally, the dependence of the Ti amount on crush load depicted that the pebbles with the larger area fraction of Be indicated the higher crush load as well as longer displacement because the Be contributed to increase of ductility in the pebbles.
阿部 浩之; 青根 茂雄*; 森本 亮*; 内田 裕久*
Journal of Alloys and Compounds, 580(Suppl.1), p.S219 - S221, 2013/12
三井 隆也; 増田 亮*; 瀬戸 誠; 平尾 直久*; 松岡 岳洋*; 中村 優美子*; 榊 浩司*; 榎 浩利*
Journal of Alloys and Compounds, 580(Suppl.1), p.S264 - S267, 2013/12
An in situ Fe synchrotron radiation Mssbauer spectroscopy (SRMS) was performed on the C15 Laves RFe (R=Y, Gd) under high-pressure hydrogen (H) in a diamond anvil cell. The H-absorption processes were monitored by the pressure dependence on the Fe isomer shift (IS): IS values increased for the amount of H-absorption into the RFe. In both cases, IS values showed a rapid increase at a few GPa, and once again showed a small increase at above 10 GPa. These results suggest that there are two steps in the H-absorption processes for the RFe under high-pressure hydrogen. At the same time, two-step magnetic transitions have been also observed for the first time: ferromagnetic RFe changed to paramagnetic RFeHx at the first H-absorption process, and a new ferromagnetic phase appeared in RFeHx at the second H-absorption process. In this conference, we report details on the SRMS experimental setup and the results.
Chen, Y.*; Feng, X.*; 粕壁 善隆*; 山本 春也; 吉川 正人; 藤野 豐*
Journal of Alloys and Compounds, 577(Suppl.1), p.S18 - S24, 2013/11
金 宰煥; 中道 勝
Journal of Alloys and Compounds, 577, p.90 - 96, 2013/11
Plasma sintering method has been newly suggested as a synthesis method for beryllium titanium intermetallic compounds (beryllides) as an advanced neutron multiplier in a system of water cooled solid breeder demonstration fusion reactors. Not only synthesis of the beryllide but joining the beryllide could be successfully fabricated. We report on the optimization of the main sintering conditions, on the sinterabilityof the plasma-sintered beryllides in the light of sinterability, as well as consolidation to the BeTi phase. The optimum sintering temperature for consolidation to the BeTi phase was 1273 K and the area fraction of the BeTi phase obtained when sintering at 1273 K, was approximately 83%. To increase the fraction of the BeTi phase, increasing the sintering time was inevitable and this led to an increase in the BeTi phase corresponding to 97.5%. However, as the sintering time increased, variation in grain size of the beryllides was observed. With regard to the sintering pressure, the higher the sintering pressure applied, the higher the sinterability, even though lower pressure may lead to better consolidation with respect to the absence of the BeTi phase.
金 宰煥; 中道 勝
Journal of Alloys and Compounds, 556, p.292 - 295, 2013/04
The synthesis of plasma-sintered beryllide with different Ti contents was carried out to investigate the sinterability and mechanical properties as a function of the phase composition. The electron probe microanalysis clarified that the area fraction of the BeTi phase increased up to a Be-7.7 at.% Ti and then sharply decreased while the area fraction of Be decreased. Specifically, in the Be-6 at.% Ti, BeTi and BeTi phases began to be formed. For the Be-10.5 at.% Ti, a large amount of the BeTi phase was detected. These results are in good agreement with the X-ray diffraction profiles obtained for the plasma-sintered beryllide with different Ti contents. In addition, the Vickers micro-hardness test results clearly prove that with increasing Ti content, the hardness increased but then became saturated near Be-7.7 at.% Ti. This hardness variation does not seem to be related to the grain size effect because the grain size increased with increasing Ti content.
金 宰煥; 中道 勝
Journal of Alloys and Compounds, 546, p.171 - 175, 2013/01
This study compares arc-melted and plasma-sintered beryllides, investigating the effects of density, hardness, microstructure, and annealing on stability. From the electron probe micro-analyzer and X-ray diffraction analysis results, it was obvious that the plasma-sintered samples, including those with 3 and 5atm% Ti, were composed of Be and BeTi phases, while BeTi and BeTi phases were additionally observed for the Be-7atm% Ti sample. In case of the arc-melted beryllides, it consisted of Be and BeTi in the 3atm% Ti and 5atm% Ti samples, whereas the BeTi phase surrounded BeTi as a peritectic phase for Be-7atm% Ti. Density and hardness measurements confirmed that the plasma-sintered beryllides were sintered with higher density and hardness than the arc-melted beryllides. In addition, the annealing treatment at 1473 K for 5 h was carried out to investigate the homogenization of the compositional structure. From the results of observation analysis for the specimens denoted as Be-3atm% Ti and Be-5atm% fabricated by both methods, there was no change on compositional structure. However, for arc-melted Be-7atm% Ti, the Be phase was almost diminished, whereas there was a slight increase in the BeTi phase and a slight decrease in the BeTi phase. In the case of the plasma-sintered Be-7atm% Ti specimen, it was clarified that the BeTi and BeTi phases were homogenized into the BeTi phase.
遠藤 成輝; 齋藤 寛之; 町田 晃彦; 片山 芳則; 青木 勝敏
Journal of Alloys and Compounds, 546, p.270 - 274, 2013/01
In the present study, we clearly determined the phase diagram of TiH at high pressures and high temperatures, and were the first to report the equation of state (EoS) of TiH with an fcc phase. Compression induced strain inhibited the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine. Thus, the phase boundary was appropriately determined using a sample which was treated at high temperature to remove strain. The obtained phase boundary was considerably lower than the experimental data reported by Vennila et al (2008). Additionally, we successfully obtained the high temperature Birch-Murnaghan EoS of TiH, and reported the thermoelastic parameters of fcc TiH.
松村 大樹; 岡島 由佳*; 西畑 保雄; 水木 純一郎
Journal of Alloys and Compounds, 509(Suppl.2), p.S849 - S852, 2011/09
栗原 正義*; 尾上 順*; 平田 勝; 鈴木 知史
Journal of Alloys and Compounds, 509(4), p.1152 - 1156, 2011/01
相ウランにおける遷移金属(TM)の固溶挙動を、相対論DV-X分子軌道法を用いて検討した。固溶性の評価には、遷移金属のd軌道のエネルギー(Md)、及び、遷移金属とウランの原子軌道間の軌道結合次数(OOP)を用いた。この分子軌道法による計算結果から、U 6dとTM dとの相互作用が、-U/TM合金の最大固溶度(MSS)について、重要な役割を果たしていることがわかった。また、MSSの値は、d-d軌道相互作用による安定化エネルギーにより説明され、MdとOOPはこの安定化エネルギーに影響していることがわかった。
竹内 正行; 中島 靖雄; 星野 国義*; 河村 文雄*
Journal of Alloys and Compounds, 506(1), p.194 - 200, 2010/09
Corrosion resistance of nickel-base alloys in HNO-HF mixtures was investigated to apply them to FLUOREX process, which is advanced hybrid process of fluoride volatility and solvent extraction for next-generation spent nuclear oxide fuel reprocessing. Many types of Ni-Cr and Ni-Cr-X (X= Mo, W, Nb, Ti, Si, Cu) ingots were experimentally manufactured and the desirable chromium and third element contents in nickel-base alloys were discussed in narrow range to improve the corrosion resistance in hot HNO-HF mixtures. From the results of corrosion tests, Ni-45Cr-0.25Mo alloy exhibited the best corrosion resistance in this study. The corrosion rate was 0.17mm/y in 8M HNO-0.1M HF solutions at 373K and it provided good performance as corrosion resistant materials. In conclusion, it was found that the control of higher chromium content and a small amount of molybdenum in nickel-base alloys are significant to improve the corrosion resistance in HNO-HF mixtures.
齋藤 寛之; 岡島 由佳; 米田 安宏; 町田 晃彦; 川名 大地; 綿貫 徹; 片山 芳則; 青木 勝敏
Journal of Alloys and Compounds, 496(1-2), p.L25 - L28, 2010/04
The hydrogenation process of aluminum is observed at high pressure and temperature by angle-dispersive X-ray diffraction method. At 10 GPa and 600 C, single crystals of AlH about 20 m in size are found to grow through three steps: self-pulverization of aluminum, hydrogenation of pulverized aluminum, and solid-state grain growth of hydride. The self-pulverization seems to be the precursor of the hydrogenation reaction because it occurs at pressure temperature conditions where AlH is thermodynamically stable.