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論文

Morphology evolution of $$beta$$-phase in Al-Mg-Si alloys during aging treatment

Ahmed, A.*; Uttarasak, K.*; 土屋 大樹*; Lee, S.*; 西村 克彦*; 布村 紀男*; 清水 一行*; 平山 恭介*; 戸田 裕之*; 山口 正剛; et al.

Journal of Alloys and Compounds, 988, p.174234_1 - 174234_9, 2024/06

https://doi.org/10.1016/j.jallcom.2024.174234

本研究は、Al-Mg-Si合金における$$beta$$相の成長過程を形態進化の観点から明らかにすることを目的とする。本研究では、高分解能透過電子顕微鏡(HR-TEM)、集束イオンビーム(FIB)及び光学顕微鏡(OM)を用いて、$$beta$$相の配向関係、形状、成長過程、ミスフィット値、及び$$beta$$相とAlマトリックスとの界面状態を調べた。その結果、$$beta$$相の端に$$beta$$ファセットが確認され、$$beta$$相の新しい3次元形状が2つ提案された。我々は、Mg$$_2$$Si結晶の成長過程における形態変化を説明するためにミスフィットを計算し、不安定な{111}$$beta$$ファセットが(001)$$beta$$ファセットや(011)$$beta$$ファセットと比較して高いミスフィット値を持つことを解明した。これは、Al-Mg-Si合金の微細構造変化を予測し、所望の特性を持つ材料を設計するために重要な知見である。

論文

Probing deformation behavior of a refractory high-entropy alloy using ${it in situ}$ neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

https://doi.org/10.1016/j.jallcom.2023.172635
 被引用回数：0 パーセンタイル：0(Chemistry, Physical)

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb)$$_{98}$$$$N_2$$ refractory high-entropy alloy (HEA) during tensile loading has been investigated using ${it in situ}$ neutron diffraction. The equivalent strain-hardening rate of each of the primary $$<hkl>$$-oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses.

論文

Single crystal growths and magnetic properties of hexagonal polar semimetals $$R$$AuGe ($$R$$ = Y, Gd-Tm, and Lu)

車地 崇*; 厳 正輝*; 鬼頭 俊介*; 池内 和彦*; 中村 充孝; 池田 暁彦*; 有馬 孝尚*

Journal of Alloys and Compounds, 947, p.169475_1 - 169475_8, 2023/06

https://doi.org/10.1016/j.jallcom.2023.169475
 被引用回数：1 パーセンタイル：54.26(Chemistry, Physical)

We study structural and magnetic properties of rare-earth based semimetals ${it R}$AuGe (${it R}$ = Y, Gd-Tm, and Lu) using flux-grown single crystals. We evaluate the crystal electric field parameters based on the Stevens operators to reasonably reproduce the temperature dependence of magnetic susceptibilities and specific heat for RAuGe (${it R}$ = TbTm). The estimated energy scale of the Ising gap ($$sim$$ 11 meV) in TmAuGe is consistent with an excitation observed in an inelastic neutron scattering experiment. These findings suggest an opportunity for interplay between conduction electrons and nontrivial spin structures in the family of magnetic polar semimetals ${it R}$AuGe.

論文

Antiferromagnetism and mixed valency in the new Kondo lattice compound Ce$$_{3}$$Rh$$_{4}$$Sn$$_{7}$$

Opletal, P.; Duverger-N$'e$dellec, E.*; Miliyanchuk, K.*; Malick, S.*; Hossain, Z.*; Custers, J.*

Journal of Alloys and Compounds, 927, p.166941_1 - 166941_7, 2022/12

https://doi.org/10.1016/j.jallcom.2022.166941
 被引用回数：2 パーセンタイル：32.54(Chemistry, Physical)

Single crystals of a new ternary compound Ce$$_{3}$$Rh$$_{4}$$Sn$$_{7}$$ were synthesized by flux method and its crystal structure and magnetic properties were studied by single crystal X-ray diffraction and magnetic susceptibility, specific heat and resistivity measurements. Ce$$_{3}$$Rh$$_{4}$$Sn$$_{7}$$ crystallizes in a new monoclinic crystal structure, space group $$P$$2$$_{1}$$m (No. 11) with Z = 2 and lattice parameters $$a$$ = 9.8708(5) ${AA}$, $$b$$ = 4.5779(3) ${AA}$; and $$c$$ = 14.2381(7) ${AA}$, $$beta$$ = 109.535(5)$$^{circ}$$, and V = 606.35(6) ${AA}$ $$^{3}$$. The structure exhibits three inequivalent Ce-sites. A striking structural motif is the tetragonal pyramid of Rh-ions surrounding the Ce2 yielding an extreme short Ce2-Rh1 spacing of $$d$$ = 2.7486(10) ${AA}$. This strong hint to mixed valent cerium behavior is supported by the entropy analysis. We argue that the Ce2-ion is in a nonmagnetic Ce$$^{3+ delta}$$ state while the other 2 Ce-sites are in a trivalent state. At low temperatures these latter become partially Kondo screened ($$T_{rm K}$$ $${approx}$$ 4 K) and order antiferromagnetic below $$T_{rm N}$$ = 2.31 K. The ordering is accompanied by a superzone gap-opening in direction of the magnetic propagation vector Q = (0, 0, l).

論文

Stress contribution of B2 phase in Al$$_{0.7}$$CoCrFeNi eutectic high entropy alloy

Yun, D.*; Chae, H.*; Lee, T.*; Lee, D.-H.*; Ryu, H. J.*; Banerjee, R.*; Harjo, S.; 川崎 卓郎; Lee, S. Y.*

Journal of Alloys and Compounds, 918, p.165673_1 - 165673_7, 2022/10

https://doi.org/10.1016/j.jallcom.2022.165673
 被引用回数：3 パーセンタイル：32.54(Chemistry, Physical)

In this study, the deformation behavior and strengthening contribution of the FCC phase and B2 phase in Al$$_{0.7}$$CoCrFeNi eutectic high entropy alloys (HEAs) were investigated using in-situ neutron diffraction. An FCC matrix phase exhibited a slip-dominant deformation scheme, while twinning hardly contributed to deformation. Applied macroscopic stresses were rarely redistributed to the BCC A2 phase dispersed within the B2 phase, whereas the stress contribution of the B2 phase, which was initially lower than that of the FCC phase, increased significantly with an increase in plastic strain; hence, its contribution to tensile deformation became predominant. This study allows us to postulate a target value of each phase by microstructural tunning to achieve the desired properties of multicomponent phase HEAs.

論文

Strain hardening behavior of additively manufactured and annealed AlSi3.5Mg2.5 alloy

Zhang, X. X.*; Lutz, A.*; Andr$"a$, H.*; Lahres, M.*; Gong, W.; Harjo, S.; Emmelmann, C.*

Journal of Alloys and Compounds, 898, p.162890_1 - 162890_8, 2022/03

https://doi.org/10.1016/j.jallcom.2021.162890
 被引用回数：6 パーセンタイル：71.08(Chemistry, Physical)

The ductility of the Al alloys produced by additive manufacturing (AM) has become a critical property, as the AM Al alloys are increasingly used in the automotive industry. However, the ductility of as-built AM Al alloys is relatively low, even with optimized AM conditions. The post-annealing treatment provides an efficient way to improve ductility. Previous investigation has shown that the annealed AM AlSi3.5Mg2.5 alloy possesses superior ductility. However, the plastic deformation micro-mechanisms of the annealed AM AlSi3.5Mg2.5 alloy remain unclear. In this study, in-situ neutron diffraction was employed to explore the annealed AM AlSi3.5Mg2.5 alloy. The evolutions of phase stresses, dislocation density, and crystallite size in the annealed AM AlSi3.5Mg2.5 alloy during tensile deformation were analyzed. The experimental investigation reveals that the dislocation density in the Al matrix of the annealed AM AlSi3.5Mg2.5 alloy increases slowly in the early plastic deformation stage, and it reaches a saturated level upon the following uniform deformation. The crystallite size decreases quickly in the early deformation stage, and then it decreases slowly. The Kocks-Mecking model and the Voce model can capture the strain hardening behavior well. The determined physical constitutive equations can be applied in continuum mechanical computer simulations.

論文

Magnetic phase diagram of helimagnetic Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ (0 $$leq$$ x $$leq$$ 0.2) hexagonal ferrite

丸山 建一*; 田中 誠也*; 鬼柳 亮嗣; 中尾 朗子*; 森山 健太郎*; 石川 喜久*; 天児 寧*; 飯山 拓*; 二村 竜祐*; 内海 重宣*; et al.

Journal of Alloys and Compounds, 892, p.162125_1 - 162125_8, 2022/02

https://doi.org/10.1016/j.jallcom.2021.162125
 被引用回数：2 パーセンタイル：16.86(Chemistry, Physical)

Hexagonal ferrite Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ is an important magnetic oxide material in both science and engineering because it exhibits helimagnetism around room temperature (300 K). In this study, the magnetic phase diagram of Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ consisting of ferri-, heli-, antiferro-, and paramagnetic phases has been completed through magnetization and neutron diffraction measurements. The magnetic phase transition temperature to paramagnetism decreases with the increase in x, and the temperature at which the magnetization reaches a maximum, which corresponds to the magnetic phase transition from heli- to ferrimagnetism, is determined for low x crystals. The temperatures at which helimagnetism appears are precisely determined by observing the magnetic satellite reflection peaks in neutron diffraction at various temperatures, which characterize helimagnetism. Based on these results, the magnetic phase diagram of the Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ system is constructed in the T-x plane. Helimagnetism appears at x $$>$$ 0.06, and magnetism with antiferromagnetic components appears as the extension phase of helimagnetism at x $$>$$ 0.19 through the coexistence region. The turn angle $$phi_{0}$$ of the helix for each x crystal is calculated from the relationship, $$phi_{0} = 2pidelta$$, where $$delta$$ is the incommensurability. The turn angle $$phi_{0}$$ decreases with the increase in temperature for the same x crystal, and increases with the increase in x at the same temperature. Furthermore, it is found that there are clear thresholds at which $$phi_{0}$$ cannot take values between 0$$^{circ}$$ < $$phi_{0}$$ < 90$$^{circ}$$ and 170$$^{circ}$$ < $$phi_{0}$$ < 180$$^{circ}$$.

論文

Anisotropic thermal lattice expansion and crystallographic structure of strontium aluminide within Al-10Sr alloy as measured by in-situ neutron diffraction

Liss, K.-D.*; Harjo, S.; 川崎 卓郎; 相澤 一也; 徐 平光

Journal of Alloys and Compounds, 869, p.159232_1 - 159232_9, 2021/07

AA2020-0822.pdf:1.94MB

https://doi.org/10.1016/j.jallcom.2021.159232
 被引用回数：6 パーセンタイル：47.82(Chemistry, Physical)

The aluminium strontium master alloy Al-10Sr has been investigated by in-situ neutron diffraction upon a heating-cooling cycle, revealing composition, crystallographic structure, lattice evolution and linear thermal expansion coefficients. Expansion of the Al matrix between (23.5 ... 26.7)$$times$$10$$^{-6}$$ K$$^{-1}$$ depends on temperature and fits well to the literature values, extrapolating to higher temperature at 800 K. Thermal expansion is highly anisotropic for tetragonal Al$$_{4}$$Sr by a factor of 1.86 with values of 20.8 and 11.1$$times$$10$$^{-6}$$ K$$^{-1}$$ in ${it a}$ and ${it c}$-axis. The even large discrepancy to the Al matrix is prone to residual intergranular phase stresses, explaining the brittleness of such composite material. Upon first heating, recovery of the initially plastically deformed materials is observed until 600 K and 700 K, for Al$$_{4}$$Sr and Al. Rietveld analysis refines the 4${it e}$ Wyckoff positions of the ${it I}$ 4/${it m m m}$ crystal structure to ${it z}$ = 0.39 revealing that local tetrahedrons are regular while local hexagons are stretched, in contrast to the literature. Its lattice parameters report to $$a_{rm I}$$ = 4.44240(48) ${AA}$, $$c_{rm I}$$ = 11.0836(15) ${AA}$ at 300 K. Furthermore, the manuscript demonstrates full technical analysis of the neutron data. Findings feed into data bases and an outlook for improving mechanical properties of Al$$_{4}$$Sr composites is given.

論文

Dielectric and magnetocaloric study of TmCrO$$_{3}$$

吉井 賢資; 池田 直*

Journal of Alloys and Compounds, 804, p.364 - 369, 2019/10

https://doi.org/10.1016/j.jallcom.2019.06.359
 被引用回数：11 パーセンタイル：54.33(Chemistry, Physical)

ペロブスカイトTmCrO$$_{3}$$の誘電性と磁気熱量効果について調べた。この物質は最近、磁気秩序温度125K以下においてCrスピンの弱強磁性秩序と強誘電性が共存するマルチフェロイック物質であると報告されている。誘電応答からは、室温近傍で10000程度の大きな誘電率が観測されたものの、交流抵抗の解析などから、これは伝導キャリアの応答によるものであることが分かった。磁気熱量効果の測定からは、磁気転移温度125Kでの転移は2次であり、もしマルチフェロイックであれば期待されうる磁歪は存在しないことが強く示唆された。すなわち、この物質が強誘電性を持つことは示されなかった。

論文

Anomalous ferromagnetic ordering in EuCuP

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

https://doi.org/10.1016/j.jallcom.2019.02.213
 被引用回数：6 パーセンタイル：33.98(Chemistry, Physical)

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.

論文

Abnormally enhanced diamagnetism in Al-Zn-Mg alloys

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

https://doi.org/10.1016/j.jallcom.2018.10.037
 被引用回数：3 パーセンタイル：17.96(Chemistry, Physical)

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.

論文

Temperature stability of PIN-PMN-PT ternary ceramics during pyroelectric power generation

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

https://doi.org/10.1016/j.jallcom.2018.07.182
 被引用回数：17 パーセンタイル：66.2(Chemistry, Physical)

Relaxor-based ternary Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$-Pb(Mg$$_{1/3}$$Nb$$_{2/3}$$)O$$_3$$-PbTiO$$_3$$ (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$$_{net}$$) were 2.43-3.01 mW/cm$$^3$$ at temperatures above 200$$^circ$$C and were maintained at above 1 mW/cm$$^3$$ 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.

論文

Impurity effects in the microscopic elastic properties of polycrystalline Mg-Zn-Y alloys with a synchronised long-period stacking ordered phase

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

https://doi.org/10.1016/j.jallcom.2016.10.266
 被引用回数：3 パーセンタイル：16.72(Chemistry, Physical)

Inelastic X-ray scattering (IXS) was performed on polycrystalline Mg$$_{97}$$Zn$$_1$$Y$$_2$$ and Mg$$_{85}$$Zn$$_6$$Y$$_9$$ 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$$_2$$-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.

論文

Hydrogenation of $$L$$1$$_{2}$$-type AlNi$$_{3}$$ alloy at high pressure and temperature

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

https://doi.org/10.1016/j.jallcom.2015.01.200
 被引用回数：0 パーセンタイル：0.01(Chemistry, Physical)

We investigated the hydrogenation of the $$L$$1$$_{2}$$-type AlNi$$_{3}$$ alloy at 3 GPa and 500$$^{circ}$$C 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 (AlNi$$_{3}$$H$$_{x}$$) was formed. Because of such isotropic lattice expansion, the hydrogen-occupied sites were the body-center sites of the $$L$$1$$_{2}$$ structure (P$$m$$-3$$m$$). In this case, the hydrogen content was calculated to be $$x$$ = 1.0, which is consistent with the experimental results. The AlNi$$_{3}$$H$$_{x}$$ hydride was stable under ambient conditions.

論文

Synthesis of Be-Ti-V ternary beryllium intermetallic compounds

金 宰煥; 中道 勝

Journal of Alloys and Compounds, 640, p.285 - 289, 2015/08

https://doi.org/10.1016/j.jallcom.2015.04.050
 被引用回数：3 パーセンタイル：17.9(Chemistry, Physical)

Beryllium intermetallic compounds (beryllides) such as Be$$_{12}$$Ti and Be$$_{12}$$V 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 Be$$_{12}$$Ti phase; however, Be$$_{17}$$Ti$$_{2}$$ and Be phases were present along with the Be$$_{12}$$Ti 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$$_{2}$$ generation rates because of oxidation, as Be$$_{12}$$Ti and Be$$_{12}$$V phases have a similar oxidation tendency.

論文

Comparative study of sinterability and thermal stability in plasma-sintered niobium and vanadium beryllides

金 宰煥; 中道 勝

Journal of Alloys and Compounds, 638, p.277 - 281, 2015/07

https://doi.org/10.1016/j.jallcom.2015.03.105
 被引用回数：5 パーセンタイル：27.56(Chemistry, Physical)

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, Be$$_{12}$$Nb, Be$$_{17}$$Nb$$_{2}$$, and Be$$_{2}$$Nb, whereas that with 7.7 at.% V consisted of Be$$_{12}$$V, Be$$_{2}$$V, and V. As the sintering time increased, area fractions of the target compositions Be$$_{12}$$Nb and Be$$_{12}$$V 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.

論文

Preliminary synthesis and mechanical property of titanium beryllide pebbles with different chemical compositions

金 宰煥; 中道 勝

Journal of Alloys and Compounds, 585, p.63 - 68, 2014/02

https://doi.org/10.1016/j.jallcom.2013.09.103
 被引用回数：14 パーセンタイル：55.58(Chemistry, Physical)

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 Be$$_{12}$$Ti phase with a Be$$_{17}$$Ti$$_{2}$$ 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.

論文

Synergic effects of ion irradiations (La, Ce) and alkaline pretreatment (KOH) on hydriding kinetic property of a Mm-Ni based alloy

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

https://doi.org/10.1016/j.jallcom.2013.03.141
 被引用回数：5 パーセンタイル：31.8(Chemistry, Physical)

水素吸蔵合金の吸蔵能の1つに、水素吸蔵初期反応速度がある。今回、イオン照射による表面改質技術を目的に種々のイオンをMm-Ni系水素吸蔵合金に照射したところ希土類イオンであるLaイオン,Ceイオンが水素吸蔵初期反応速度を大きく向上させることが判明した。さらにこれらイオン照射後のサンプルをKOHアルカリ溶液にて化学処理を施した場合、イオン照射したサンプルよりも数倍の初期反応速度の向上が見られた。これら希土類元素は水素を吸収しやすい物質であるため、表面にLaやCeイオンを導入することで初期反応速度が促進されたと考えられる。さらにKOHのアルカリ溶液にて化学処理をすることで、表面酸化膜がエッチングされるとともに、カリウム原子が合金表面仕事関数を下げることで、初期反応速度が速くなると考えられる。

論文

In situ synchrotron $$^{57}$$Fe M$"o$ssbauer spectroscopy of RFe$$_{2}$$ (R = Y, Gd) hydrides synthesized under ultra-high-pressure hydrogen

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

https://doi.org/10.1016/j.jallcom.2013.03.271
 被引用回数：8 パーセンタイル：42.73(Chemistry, Physical)

An in situ $$^{57}$$Fe synchrotron radiation M$"o$ssbauer spectroscopy (SRMS) was performed on the C15 Laves RFe$$_{2}$$ (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 $$^{57}$$Fe isomer shift (IS): IS values increased for the amount of H-absorption into the RFe$$_{2}$$. 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$$_{2}$$ under high-pressure hydrogen. At the same time, two-step magnetic transitions have been also observed for the first time: ferromagnetic RFe$$_{2}$$ changed to paramagnetic RFe$$_{2}$$Hx$$_{1}$$ at the first H-absorption process, and a new ferromagnetic phase appeared in RFe$$_{2}$$Hx$$_{2}$$ at the second H-absorption process. In this conference, we report details on the SRMS experimental setup and the results.

論文

Epitaxial transformation of hcp-fcc Ti sublattices during nitriding processes of evaporated-Ti thin films due to nitrogen-implantation

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

https://doi.org/10.1016/j.jallcom.2011.10.113
 被引用回数：2 パーセンタイル：17(Chemistry, Physical)

本研究では、原子力機構のイオン導入型400kV電子顕微鏡を利用して、チタン蒸着膜への窒素イオン注入窒化過程におけるチタン副格子の六方最密-面心立方(hcp-fcc)構造変化を、透過型電子顕微鏡法及び電子エネルギー損失分光法によりその場観察・評価し、分子軌道計算による電子状態の評価と合わせて窒化チタン薄膜の形成機構及び配向の制御性に関する知見を得てきた。本発表では、窒素イオン注入によるチタン薄膜の窒化過程と電子構造から考察したhcp-fccエピタキシャル構造変態について報告する。

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