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Defect equilibria and thermophysical properties of CeO$$_{2-x}$$ based on experimental data and density functional theory calculation result

渡部 雅; 中村 博樹; 鈴木 紀一; 町田 昌彦; 加藤 正人

Journal of the American Ceramic Society, 105(3), p.2248 - 2257, 2022/03



Phase transition and domain formation in ferroaxial crystals

林田 健志*; 上村 洋平*; 木村 健太*; 松岡 悟志*; 萩原 雅人; 廣瀬 左京*; 盛岡 仁*; 長谷川 達夫*; 木村 剛*

Physical Review Materials (Internet), 5(12), p.124409_1 - 124409_10, 2021/12

The ferroaxial order, which is characterized by a rotational structural distortion in a crystal, has been recently proposed as one of ferroic orders. Though the domain formation is a characteristic feature in ferroic materials, there has been little study done concerning that for the ferroaxial order. Here, we investigate ferroaxial domains that are formed through a ferroaxial transition in two representative ferroaxial materials, NiTiO$$_{3}$$ and RbFe(MoO$$_{4}$$)$$_{2}$$. We spatially resolve their domain structures using an optical method based on electric-field- induced optical rotation, that is, electrogyration (EG). In NiTiO$$_{3}$$, multi-domains are constructed when crystals undergo a ferroaxial transition and the domain size depends on the cooling rate around the transition temperature. Furthermore, the ferroaxial domain structure obtained by the EG measurement is well matched with that by scanning X-ray diffraction (XRD). RbFe(MoO$$_{4}$$)$$_{2}$$ also exhibits multi-domain states in which domain patterns are different each time a crystal undergoes a ferroaxial transition. In addition, the temperature dependence of the EG signal well obeys that of the order parameter of a first-order phase transition. These results ensure the effectiveness of the EG effect to elucidate the nature of ferroaxial order.



田口 茂郎; 田口 克也; 牧野 理沙; 山中 淳至; 鈴木 一之; 高野 雅人; 越野 克彦; 石田 倫彦; 中野 貴文; 山口 俊哉

日本保全学会第17回学術講演会要旨集, p.499 - 502, 2021/07



Morphological reproductive characteristics of testes and fertilization capacity of cryopreserved sperm after the Fukushima accident in raccoon (${it Procyon lotor}$)

小松 一樹*; 岩崎 亜美*; 村田 康輔*; 山城 秀昭*; Goh, V. S. T.*; 中山 亮*; 藤嶋 洋平*; 小野 拓実*; 木野 康志*; 清水 良央*; et al.

Reproduction in Domestic Animals, 56(3), p.484 - 497, 2021/03



Effect of grain boundary on the friction coefficient of pure Fe under the oil lubrication

足立 望*; 松尾 泰貴*; 戸高 義一*; 藤本 幹也*; 日野 正裕*; 光原 昌寿*; 大場 洋次郎; 椎原 良典*; 梅野 宜崇*; 西田 稔*

Tribology International, 155, p.106781_1 - 106781_9, 2021/03

 被引用回数:0 パーセンタイル:0(Engineering, Mechanical)

Recent theoretical researches revealed that grain boundary affects tribological properties through the change in adsorption properties of additives in lubricants. Therefore, the effects of the grain boundary on the tribological properties were investigated by friction test of pure iron films under oil lubrication. We found that a friction coefficient decreases with increasing the fraction of the grain boundary in the lubricants forming chemisorbed film on sample surface. This suggests that the grain boundary enhances the formation of the chemisorbed films and reduces the friction coefficients by protecting the sample surface.


Spin glass behavior in EuCu$$_2$$Si$$_2$$ single crystal grown by the flux method

竹内 徹也*; 芳賀 芳範; 谷口 年史*; 伊覇 航*; 安次富 洋介*; 屋良 朝之*; 木田 孝則*; 田原 大夢*; 萩原 政幸*; 中島 美帆*; et al.

Journal of the Physical Society of Japan, 89(3), p.034705_1 - 034705_15, 2020/03

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Single crystals of EuCu$$_2$$Si$$_2$$ have been grown by the flux method and Bridgman method. The Eu ions of the Bridgman-grown crystal are nearly trivalent and fluctuate depending on the temperature. On the other hand, the Eu ions of flux-grown sample are divalent and thermally stable and show spin-glass behavior at low temperatures. Crystallographic analyses identified random replacement of Cu sites by Si only for the flux-grown samples. Such structural randomness leads to spin-glass features.


Intrinsic 2D ferromagnetism in V$$_{5}$$Se$$_{8}$$ epitaxial thin films

中野 匡規*; Wang, Y.*; 吉田 訓*; 松岡 秀樹*; 真島 裕貴*; 池田 啓祐*; 平田 靖透*; 竹田 幸治; 和達 大樹*; 小濱 芳允*; et al.

Nano Letters, 19(12), p.8806 - 8810, 2019/12

 被引用回数:22 パーセンタイル:91.07(Chemistry, Multidisciplinary)

The discoveries of intrinsic ferromagnetism in atomically thin van der Waals crystals have opened a new research field enabling fundamental studies on magnetism at two-dimensional (2D) limit as well as development of magnetic van der Waals heterostructures. Here we demonstrate that V$$_{5}$$Se$$_{8}$$ epitaxial thin films grown by molecular-beam epitaxy exhibit emergent 2D ferromagnetism with intrinsic spin polarization of the V 3d electrons although the bulk counterpart is originally antiferromagnetic. Moreover, thickness-dependence measurements reveal that this newly developed 2D ferromagnet could be classified as an itinerant 2D Heisenberg ferromagnet with weak magnetic anisotropy.


Research and development on membrane IS process for hydrogen production using solar heat

Myagmarjav, O.; 岩月 仁; 田中 伸幸; 野口 弘喜; 上地 優; 井岡 郁夫; 久保 真治; 野村 幹弘*; 八巻 徹也*; 澤田 真一*; et al.

International Journal of Hydrogen Energy, 44(35), p.19141 - 19152, 2019/07

 被引用回数:12 パーセンタイル:67.04(Chemistry, Physical)

Thermochemical hydrogen production has attracted considerable interest as a clean energy solution to address the challenges of climate change and environmental sustainability. The thermochemical water-splitting iodine-sulfur (IS) process uses heat from nuclear or solar power and thus is a promising next-generation thermochemical hydrogen production method that is independent of fossil fuels and can provide energy security. This paper presents the current state of research and development of the IS process based on membrane techniques using solar energy at a medium temperature of 600$$^{circ}$$C. Membrane design strategies have the most potential for making the IS process using solar energy highly efficient and economical and are illustrated here in detail. Three aspects of membrane design proposed herein for the IS process have led to a considerable improvement of the total thermal efficiency of the process: membrane reactors, membranes, and reaction catalysts. Experimental studies in the applications of these membrane design techniques to the Bunsen reaction, sulfuric acid decomposition, and hydrogen iodide decomposition are discussed.



礒崎 尚彦; 森本 憲次; 古川 竜一; 坪井 雅俊; 矢田 祐士; 三好 竜太; 内田 豊実; 池澤 和美*; 黒澤 健二*

日本保全学会第16回学術講演会要旨集, p.225 - 228, 2019/07



Crystal structure change of katoite, Ca$$_{3}$$Al$$_{2}$$(O$$_{4}$$D$$_{4}$$)$$_{3}$$, with temperature at high pressure

興野 純*; 加藤 正人*; 佐野 亜沙美; 町田 真一*; 服部 高典

Physics and Chemistry of Minerals, 46(5), p.459 - 469, 2019/05

 被引用回数:1 パーセンタイル:12.33(Materials Science, Multidisciplinary)

加藤ザクロ石の高圧下で高温分解メカニズムを明らかにするために8GPaにおける高温中性子回折実験を行った。200-400$$^circ$$Cの温度域で異常な熱膨張が観測されたものの、約850$$^circ$$Cまで連続的に膨張した。その後、900$$^circ$$Cでザクロ石は分解した。これは分解温度が圧力により300$$^circ$$Cから900$$^circ$$Cへと上昇することを示している。常温常圧に戻すと、脱水後は消失していた加藤ザクロ石がAl$$_{2}$$O$$_{3}$$、Ca(OD)$$_{2}$$とともに、再び現れた。構造解析の結果、8GPaにおいて、850$$^circ$$Cまでの昇温でCaO$$_{8}$$及びAlO$$_{6}$$多面体がそれぞれ8% and 13%膨張するのに対し、四面体空隙はその影響を受け10%縮むことが分かった。同時に、隣接するD-D距離は一定なのに対し、O-D距離は分解直前に劇的に減少する。このことは、D-D間反発により生じたO-D距離の減少が、O-D結合を不安定化させ、加藤ザクロ石の高温分解を引き起こすことを示している。



佐々木 宏和*; 西久保 英郎*; 西田 真輔*; 山崎 悟志*; 中崎 竜介*; 磯松 岳己*; 湊 龍一郎*; 衣川 耕平*; 今村 明博*; 大友 晋哉*; et al.

古河電工時報, (138), p.2 - 10, 2019/02



Isotope-selective microscale imaging of radioactive Cs without isobaric interferences using sputtered neutral mass spectrometry with two-step resonant ionization employing newly-developed Ti:Sapphire lasers

坂本 哲夫*; 森田 真人*; 金成 啓太*; 富田 英生*; Sonnenschein, V.*; 齊藤 洸介*; 大橋 雅也*; 加藤 弘太郎*; 井口 哲夫*; 河合 利秀*; et al.

Analytical Sciences, 34(11), p.1265 - 1270, 2018/11

 被引用回数:7 パーセンタイル:39.71(Chemistry, Analytical)

Characterization of radionuclides in Fukushima is important to determine their origins and current state in the environment. Radionuclides exist as fine particles and are mixed with other constituents. A measurement method with both micro-imaging capability and highly selective element detection is necessary to analyze these particles. We developed such an imaging technique using a time-of-flight secondary ion mass spectrometry and wavelength tunable Ti:Sapphire lasers for resonance ionization of target elements without mass interference. This is called resonant laser ionization sputtered neutral mass spectrometry. The instrument has high lateral resolution and higher ionization selectivity using two-step resonance excitation of Cs with two lasers at different wavelengths. Optimization of the wavelength for resonance ionization using a Cs compound was performed, and a real environmental particle containing radioactive Cs was analyzed. Isotope images of three kinds of Cs were successfully obtained without interfere from Ba isotopes for the first time.


Convergence behavior in line profile analysis using convolutional multiple whole-profile software

熊谷 正芳*; 内田 知宏*; 村澤 皓大*; 高村 正人*; 池田 義雅*; 鈴木 裕士; 大竹 淑恵*; 浜 孝之*; 鈴木 進補*

Materials Research Proceedings, Vol.6, p.57 - 62, 2018/10

 被引用回数:0 パーセンタイル:0.2

The convergence behavior of the parameters related to microstructural characteristics $$a$$-$$e$$ was studied during optimizations in a common line profile analysis software program based on the convolutional multiple whole profile (CMWP) method. The weighted sums of squared residual (WSSR) was a criterion of the optimization. The parameters $$b$$ and $$d$$, which are related to the dislocation density and to the crystallite size, respectively, strongly affect the line profile shape. Therefore, the distributions of WSSRs on the space parameters $$b$$ and $$d$$ were first observed. The variation trajectory of parameters $$b$$ and $$d$$ during iterative calculations with several values of parameter $$e$$ was then observed, along with the variations when all of the parameters were variable. In the case where only three parameters were variable, we found that a smaller initial value of $$e$$ should be chosen to ensure stability of the calculations. In the case where all parameters were variable, although all of the results converged to similar values, they did not precisely agree. To attain accurate optimum values, a two-step procedure is recommended.


Effects of magnetic field and pressure on the valence-fluctuating antiferromagnetic compound EuPt$$_2$$Si$$_2$$

竹内 徹也*; 屋良 朝之*; 安次富 洋介*; 伊覇 航*; 垣花 将司*; 中島 美帆*; 天児 寧*; 本多 史憲*; 本間 佳哉*; 青木 大*; et al.

Journal of the Physical Society of Japan, 87(7), p.074709_1 - 074709_14, 2018/07

 被引用回数:7 パーセンタイル:63.33(Physics, Multidisciplinary)

Effects of magnetic field and pressure on the Kondo-like behavior in the valence-fluctuating antiferromagnetic compound EuPt$$_2$$Si$$_2$$ were studied using single-crystalline samples. Anomalous features in EuPt$$_2$$Si$$_2$$ are due to valence fluctuation and/or valence change of the Eu ions at low temperatures.


Electronic states in EuCu$$_2$$(Ge$$_{1-x}$$Si$$_x$$)$$_2$$ based on the doniach phase diagram

伊覇 航*; 屋良 朝之*; 安次富 洋介*; 垣花 将司*; 竹内 徹也*; 本多 史憲*; 仲村 愛*; 青木 大*; 郷地 順*; 上床 美也*; et al.

Journal of the Physical Society of Japan, 87(6), p.064706_1 - 064706_14, 2018/06

 被引用回数:15 パーセンタイル:78.13(Physics, Multidisciplinary)

We succeeded in growing single crystals of the series of EuCu$$_2$$(Ge$$_{1-x}$$Si$$_x$$)$$_2$$ compounds.Physical property measurements demonstrate a maximum of the antiferromagnetic transition temperature appears at $$x = 0.5$$. Antiferromagnetism then disappears around $$x = 0.7$$ followed by a heavy-fermion formation at higher concentrations. These observations follow the Doniach phase diagram as a function of $$x$$.


Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

田中 泰貴*; 成清 義博*; 森田 浩介*; 藤田 訓裕*; 加治 大哉*; 森本 幸司*; 山木 さやか*; 若林 泰生*; 田中 謙伍*; 武山 美麗*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 被引用回数:10 パーセンタイル:72.43(Physics, Multidisciplinary)

ガス充填型反跳生成核分離装置GARISを用いて$$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, $$^{48}$$Ca + $$^{248}$$Cm反応系における準弾性散乱断面積の励起関数を測定した。これらのデータから融合障壁分布を導出し、チャンネル結合計算と比較した。$$^{48}$$Ca + $$^{208}$$Pb及び$$^{50}$$Ti + $$^{208}$$Pb反応の障壁分布のピークエネルギーはそれらの反応系における2中性子蒸発断面積のピークエネルギーと良く一致し、一方$$^{48}$$Ca + $$^{248}$$Cm反応の障壁分布のピークエネルギーは4中性子蒸発断面積のピークエネルギーより少し下に現れることが判った。この結果は超重核合成の際の最適ビームエネルギーの予測に役立つ情報を与える。


Design loads and structural member modelling to shock-resistant design of buildings

井川 望*; 向井 洋一*; 西田 明美; 濱本 卓司*; 加納 俊哉*; 大田 敏郎*; 中村 尚弘*; 小室 雅人*; 竹内 正人*

Proceedings of 12th International Conference on Shock and Impact Loads on Structures (SI 2017) (USB Flash Drive), p.259 - 268, 2017/06



Criteria for performance evaluation and numerical verification to shock-resistant design of buildings

西田 明美; 向井 洋一*; 濱本 卓司*; 櫛部 敦道*; 小室 雅人*; 大橋 泰裕*; 小尾 博俊*; 坪田 張二

Proceedings of 12th International Conference on Shock and Impact Loads on Structures (SI 2017) (USB Flash Drive), p.379 - 388, 2017/06



Defect chemistry and basic properties of non-stoichiometric PuO$$_{2}$$

加藤 正人; 中村 博樹; 渡部 雅; 松本 卓; 町田 昌彦

Defect and Diffusion Forum, 375, p.57 - 70, 2017/05




川崎 将亜; 中嶌 純也; 吉田 圭佑; 加藤 小織; 西野 翔; 野崎 天生; 中川 雅博; 角田 潤一; 菅谷 雄基; 長谷川 里絵; et al.

JAEA-Data/Code 2017-004, 57 Pages, 2017/03



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