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論文

Revealing the ion dynamics in Li$$_{10}$$GeP$$_{2}$$S$$_{12}$$ by quasi-elastic neutron scattering measurements

堀 智*; 菅野 了次*; Kwon, O.*; 加藤 祐樹*; 山田 武*; 松浦 直人*; 米村 雅雄*; 神山 崇*; 柴田 薫; 川北 至信

Journal of Physical Chemistry C, 126(22), p.9518 - 9527, 2022/06

 被引用回数:2 パーセンタイル:63.19(Chemistry, Physical)

Understanding Li-ion conduction in superionic conductors accelerates the development of new solid electrolytes to enhance the charge-discharge performances of all-solid-state batteries. We performed a quasi-elastic neutron scattering study on a model superionic conductor (Li$$_{10+x}$$Ge$$_{1+x}$$P$$_{2-x}$$S$$_{12}$$, LGPS), to reveal its ion dynamics on an angstrom-scale spatial range and a pico-to-nanosecond temporal range. The observation of spectra at 298 K confirmed the high lithium diffusivity. The obtained diffusion coefficient was in the order of 10$$^{-6}$$ cm$$^{2}$$s$$^{-1}$$ at temperatures ${textgreater}$ 338 K and was higher than the reported diffusion coefficient over a longer time scale, as determined by the pulse-field gradient nuclear magnetic resonance method. This difference indicates that there are impediments to ionic motion over a longer time scale. The dynamic behavior of the Li ions was compared with that observed for the Li$$_{9}$$P$$_{3}$$S$$_{9}$$O$$_{3}$$ phase, which possesses the same crystal structure type, but a lower ionic conductivity. The LGPS phase possessed a high lithium mobility over a distance of $${sim}$$ 10 ${AA}$, as well as a larger fraction of mobile Li ions, thereby indicating that these features enhance lithium conduction over a longer spatial scale, which is important in all-solidstate batteries.

論文

Magnetism of Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ with andalusite structure

柿本 和勇*; 高田 早紀*; 太田 寛人*; 原口 祐哉*; 萩原 雅人; 鳥居 周輝*; 神山 崇*; 三田村 裕幸*; 徳永 将史*; 畠山 温*; et al.

Journal of the Physical Society of Japan, 91(5), p.054704_1 - 054704_7, 2022/05

 被引用回数:1 パーセンタイル:68.58(Physics, Multidisciplinary)

The magnetism of Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ from $${x = 0.09}$$ to $${0.91}$$ with the andalusite structure was examined. Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ at low temperatures was found to show a weak ferromagnet-like behavior for $${x < 0.3}$$ and a spin glass behavior for $${x > 0.3}$$. The small spontaneous magnetization observed in the weak ferromagnet-like samples may be caused by the existence of Dzyaloshinsky-Moriya interaction and the difference in the magnitude of the magnetic moments of Fe$$^{3+}$$ in the octahedral and trigonal bipyramidal sites. The appearance of the spin glass behavior implies that the dilution of Fe ions by Al ions in Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ causes the competition between ferromagnetic and antiferromagnetic interactions. The $$x$$ dependence of the site occupancy of Fe ions suggests that Fe$$_{2}$$GeO$$_{5}$$ with the andalusite structure cannot be synthesized.

論文

Sinusoidal magnetic structure of andalusite-type AlxFe$$_{2}$$-xGeO$$_{5}$$ with $$x$$ = 0.09 and 0.15

柿本 和勇*; 太田 寛人*; 原口 祐哉*; 萩原 雅人; 鳥居 周輝*; 神山 崇*; 香取 浩子*

Journal of the Physical Society of Japan, 91(5), p.054707_1 - 054707_9, 2022/05

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

Neutron diffraction experiments on polycrystalline andalusite-type Al$$_{2}$$Fe$$_{2-x}$$GeO$$_{5}$$ with $$x = 0.09$$ to $$0.15$$ were performed. The magnetic Bragg peaks with the propagation vector of $$kappa$$$$_{x=0.09}$$ = (0, 0.150(1), 0) for the sample with $${x = 0.09}$$ and $$kappa$$$$_{x=0.15}$$ = (0, 0.141(1), 0) for the sample with $${x = 0.15}$$ were observed, which means that an incommensurate magnetic order was realized for each sample. The calculation of the magnetic structure factors by the Pawley method and the analysis of the irreducible representations revealed that both samples have a magnetic structure in which the magnetic moments rotate in the crystallographic $$ab$$-plane with sinusoidal modulation along the $$b$$-axis. By the Luttinger Tisza method, we determined the sign of the nearest-neighbor exchange interaction consists that reproduce the magnetic structure obtained by the irreducible representation analysis.

論文

Structural phase transition in cobalt oxyfluoride Co$$_{3}$$Sb$$_{4}$$O$$_{6}$$F$$_{6}$$ observed by high-resolution synchrotron and neutron diffraction

下野 聖矢*; 石橋 広記*; 永吉 祐輔*; 池野 豪一*; 河口 彰吾*; 萩原 雅人; 鳥居 周輝*; 神山 崇*; 市橋 克哉*; 西原 禎文*; et al.

Journal of Physics and Chemistry of Solids, 163, p.110568_1 - 110568_7, 2022/04

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

The structural phase transition from cubic ($$Ibar{4}3m$$) to a $$c > a$$ tetragonal ($$Ibar{4}$$) at $$T_{rm S}$$ $$sim$$ 180 K was found in non-centrosymmetric oxyfluoride Co$$_{3}$$Sb$$_{4}$$O$$_{6}$$F$$_{6}$$ by high-resolution neutron and synchrotron powder diffraction. To investigate this phase transition, specific heat, magnetization, and dielectric measurements were performed. Although the specific heat and dielectric constant showed anomalies at $$T_{rm S}$$, a phase transition to ferroelectricity was not observed in the polarization hysteresis loop down to 30 K. The rotation of the CoO$$_{2}$$F$$_{4}$$ octahedron was observed at $$T_{rm S}$$ from the structural analysis using synchrotron and neutron powder diffraction data. It was found that the magnetic phase transition from paramagnetic to G-type antiferromagnetic occurred at $$T_{rm N}$$ $$sim$$ 67 K, at which a peak was observed in the specific heat measurements, via magnetic structure analysis using neutron powder diffraction data. The magnetic moments of Co$$^{2+}$$ were aligned along the tetragonal $$c$$-axis direction with a Co$$^{2+}$$ moment of 2.80(1) $$mu_{rm B}$$ at 13 K.

論文

The Performance of neutron diffractometers at long and short pulse spallation sources; Comparison between ESS and J-PARC

新井 正敏*; Andersen, K. H.*; Argyriou, D. N.*; Schweika, W.*; Zanini, L.*; Harjo, S.; 神山 崇*; 原田 正英

Journal of Neutron Research, 23(4), p.215 - 232, 2021/12

The general performance of diffractometers at the first long pulse spallation source ESS, is compared with their counterparts at J-PARC, a short pulse spallation source. The difference in the inherent pulse structure of these neutron sources presents opportunities for new concepts for instrumentation, where performance does not scale simply with source power. The article describes advantages and disadvantages of those diffractometers, adapting to the very different source characteristics. We find that the two sources offer comparable performance in flux and resolution when operating in high-resolution mode. ESS offers significant advantages in tunability and flexibility, notably in the ability to relax resolution in order to increase flux for a given experiment. On the other hand, J-PARC instruments perform very well in spite of the lower source power and allow better access to epithermal neutrons, of particular interest for PDF analysis of diffraction data.

論文

Analysis and mapping of detailed inner information of crystalline grain by wavelength-resolved neutron transmission imaging with individual Bragg-dip profile-fitting analysis

櫻井 洋亮*; 佐藤 博隆*; 足立 望*; 諸岡 聡; 戸高 義一*; 加美山 隆*

Applied Sciences (Internet), 11(11), p.5219_1 - 5219_17, 2021/06

 被引用回数:2 パーセンタイル:53.25(Chemistry, Multidisciplinary)

As a new method for evaluating single crystal and oligocrystal, pulsed neutron Bragg-dip transmission analysis/imaging method is being developed. In this study, a single Bragg-dip profile fitting analysis method was newly developed, and applied for analyzing detailed inner information in a crystalline grain position-dependently. In the method, the spectrum profile of a single Bragg-dip is analyzed at each position over a grain. As a result, it is expected that changes of crystal orientation, mosaic spread angle and thickness of a perfect crystal can be evaluated from the wavelength, the width and the integrated intensity of the Bragg-dip, respectively. For confirming this effectiveness, the method was applied to experimental data of position-dependent Bragg-dip transmission spectra of a Si-steel plate consisting of oligocrystals. As a result, inner information of multiple crystalline grains could be visualized and evaluated. The small change of crystal orientation in a grain, about 0.4$$^{circ}$$, could be observed by imaging the Bragg-dip wavelengths. By imaging the Bragg-dip widths, both another grain and mosaic block in a grain were detected. Furthermore, imaging results of the integrated intensities of Bragg-dips were consistent with the results of Bragg-dip width imaging. These small crystallographic changes have not been observed and visualized by previous Bragg-dip analysis methods.

論文

Commissioning of Versatile Compact Neutron Diffractometer (VCND) at the B-3 beam port of Kyoto University Research Reactor (KUR)

森 一広*; 奥村 良*; 吉野 泰史*; 金山 雅哉*; 佐藤 節夫*; 大場 洋次郎; 岩瀬 謙二*; 平賀 晴弘*; 日野 正裕*; 佐野 忠史*; et al.

JPS Conference Proceedings (Internet), 33, p.011093_1 - 011093_6, 2021/03

京都大学研究炉(KUR)のB-3ビームポートは、過去には単結晶回折計が設置されていたが、近年はユーザーが減少し、アクティビティが低下している状況にあった。そこで本研究グループでは、近年の中性子利用に関するニーズを再調査し、B-3ビームポートに新たに多目的小型中性子回折計(VCND)を構築した。VCNDは、1.0オングストロームの入射中性子波長を利用して6度から130度までの散乱角を測定でき、既に水素吸蔵合金の研究等への利用が開始されている。講演では、今後の改修計画等についても説明する。

論文

Visualization of the boron distribution in core material melting and relocation specimen by neutron energy resolving method

阿部 雄太; 土川 雄介; 甲斐 哲也; 松本 吉弘*; Parker, J. D.*; 篠原 武尚; 大石 佑治*; 加美山 隆*; 永江 勇二; 佐藤 一憲

JPS Conference Proceedings (Internet), 33, p.011075_1 - 011075_6, 2021/03

Since the hardness of fuel debris containing boride from B$$_{4}$$C pellet in control rod is estimated to be two times higher as that of oxide, such as UO$$_{2}$$ and ZrO$$_{2}$$, distribution of such boride in the fuel debris formed in the Fukushima-Daiichi Nuclear Power Plants may affect the process of debris cutting and removal. The high neutron absorption of boron may affect the possibility of re-criticality during the process of debris removal. Therefore, boride distribution in fuel debris is regarded as an important issue to be addressed. However, boron tends to have difficult in quantification with conventionally applied methods like EPMA and XPS. In this study, accelerator-driven neutron-imaging system was applied. Since boron is the material for neutron absorption, its sensitivity in terms of neutron penetration through specimens is concerned. To adjust neutron attenuation of a specimen to suit a particular measurement by selecting the neutron energy range, we focused on the energy resolved neutron imaging system RADEN, which utilizes wide energy range from meV to keV. Development of a method to visualize boron distribution using energy-resolved neutrons has been started. In this presentation the authors show the status of the development of a method utilizing energy-resolved neutrons and provide some outcome from its application to the Core Material Melting and Relocation (CMMR)-0 and -2 specimens.

論文

Origin of magnetovolume effect in a cobaltite

Miao, P.*; Tan, Z.*; Lee, S. H.*; 石川 喜久*; 鳥居 周輝*; 米村 雅雄*; 幸田 章宏*; 小松 一生*; 町田 真一*; 佐野 亜沙美; et al.

Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03

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

層状ペロブスカイトPrBaCo$$_{2}$$O$$_{5.5}$$は、熱膨張のない複合材料を作るために必要な負の熱膨張(NTE)を示す。NTEは、自発的な磁気秩序と密接に関連していることがわかっていた(磁気体積効果: MVE)。今回、われわれは、PrBaCo$$_{2}$$O$$_{5.5}$$の連続的な磁気体積効果が、本質的には不連続であり、大きな体積を持つ反強磁性絶縁体(AFILV)から、小さな体積をもつ強磁性卑絶縁体(FLISV)への磁気電気的相転移に起因することを明らかにした。また、磁気電気効果(ME)は、温度,キャリアドーピング,静水圧,磁場などの複数の外部刺激に対して高い感度を示した。これは、これまでよく知られている対称性の破れを伴う巨大磁気抵抗やマルチフェロイック効果などのMEとは対照的であり、輝コバルト鉱のMEは同一の結晶構造で起こる。われわれの発見は、MEとNTEを実現するための新しい方法を示しており、それは新しい技術に応用されるかもしれない。

論文

Strong lattice anharmonicity exhibited by the high-energy optical phonons in thermoelectric material

Wu, P.*; Fan, F.-R.*; 萩原 雅人*; 古府 麻衣子; Peng, K.*; 石川 喜久*; Lee, S.*; 本田 孝志*; 米村 雅雄*; 池田 一貴*; et al.

New Journal of Physics (Internet), 22(8), p.083083_1 - 083083_9, 2020/08

 被引用回数:4 パーセンタイル:49.85(Physics, Multidisciplinary)

熱電材料SnSeは、過去数年間で世界的な関心を呼び、その固有の強い格子非調和性は、その優れた熱電性能の重要な要素と見なされている。一方、SnSeにおける格子非調和性の理解は、特にフォノンダイナミクスがこの動作によってどのように影響を受けるかに関して、依然として不十分である。そのため、中性子全散乱,非弾性中性子散乱,ラマン分光法、および凍結フォノン計算により、Na$$_{0.003}$$Sn$$_{0.997}$$Se$$_{0.9}$$S$$_{0.1}$$の格子力学の包括的な研究を行った。格子非調和性は、対分布関数,非弾性中性子散乱、およびラマン測定によって確かめられた。熱膨張と多重フォノン散乱の影響を分離することにより、後者は高エネルギー光学フォノンモードで非常に重要であることがわかった。フォノンモードの強い温度依存性は、この系の非調和性を示している。さらに、我々のデータは、Sドーピングにより、高エネルギー光学フォノンの線幅が広がることを明らかにした。私たちの研究は、SnSeの熱電性能は、フォノンエンジニアリングを介して格子熱伝導率への高エネルギー光学フォノンモードの寄与を減らすことによってさらに強化できることを示唆する。

論文

Development of three-dimensional distribution visualization technology for boron using energy resolved neutron-imaging system (RADEN)

阿部 雄太; 土川 雄介; 甲斐 哲也; 松本 吉弘*; Parker, J. D.*; 篠原 武尚; 大石 佑治*; 加美山 隆*; 永江 勇二; 佐藤 一憲

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08

Boron carbide is used as a neutron-absorbing material in Fukushima-Daiichi Nuclear Power Station (1F), producing borides that are twice as hard as oxides (such as UO$$_{2}$$ and ZrO$$_{2}$$). The high neutron absorption of boron affects the evaluation of re-criticality during the process of debris retrieval. Therefore, it is important not only to determine the presence of boron but also to investigate the distribution of boron inside the material in a non-destructive manner during decommissioning. To address the uncertainties in the core material relocation behavior of boiling water reactor (BWR) during a severe accident (SA), solidified melt specimens of a simulated fuel assembly were prepared by plasma heating. If core material melting and relocation (CMMR) specimens can be used to estimate the B distribution in 1F Unit-3, that will provide valuable information in the decommissioning of 1F. To address this, the authors focused on the energy-resolved neutron imaging system, RADEN, which utilizes a wide energy range, from meV to keV. This is an innovative three-dimensional analysis technology for boride distribution that affects the evaluation of hardness and re-criticality. In the calibration standard samples (Zr$$_{x}$$B$$_{1-x}$$ and Fe$$_{x}$$B$$_{1-x}$$), there was a good correlation between boron concentration and the energy-dependence of the cross sections of cold and epi-thermal neutrons. In the CMMR specimens, boron distribution was confirmed from the contrast difference between cold and epi-thermal neutrons. In the future, the results of calibration standard samples will be applied to the results of CMMR specimens. With this method, three-dimensional boron distribution will be measured, and the understanding of boride distribution 1F Unit-3 will be improved, which may be reflected in an improved SA code.

論文

The Energy-resolved neutron imaging system, RADEN

篠原 武尚; 甲斐 哲也; 及川 健一; 中谷 健; 瀬川 麻里子; 廣井 孝介; Su, Y. H.; 大井 元貴; 原田 正英; 飯倉 寛; et al.

Review of Scientific Instruments, 91(4), p.043302_1 - 043302_20, 2020/04

 被引用回数:30 パーセンタイル:95.17(Instruments & Instrumentation)

The energy-resolved neutron imaging system, RADEN, has been installed at the pulsed neutron source in the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. In addition to conventional neutron radiography and tomography, RADEN, the world's first imaging beam-line at a pulsed neutron source, provides three main options for new, quantitative neutron imaging techniques: Bragg-edge imaging to visualize the spatial distribution of crystallographic information, resonance absorption imaging for elemental composition and temperature information, and polarized neutron imaging for magnetic field information. This paper describes the results of characterization studies of the neutronic performance and installed devices at RADEN and shows the results of several demonstration studies for pulsed neutron imaging.

論文

Crystal structures of highly hole-doped layered perovskite nickelate Pr$$_{2-x}$$Sr$$_{x}$$NiO$$_{4}$$ studied by neutron diffraction

梶本 亮一; 中島 健次; 藤田 全基*; 石角 元志*; 鳥居 周輝*; 石川 喜久*; Miao, P.*; 神山 崇*

Journal of the Physical Society of Japan, 88(11), p.114602_1 - 114602_6, 2019/11

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

A high-resolution time-of-flight powder neutron diffraction study of the layered nickel oxide Pr$$_{2-x}$$Sr$$_{x}$$NiO$$_{4}$$ with $$x = 0.7$$ and $$0.9$$ was performed to characterize the crystal structures of these highly hole-doped nickelates. For the sample with $$x = 0.7$$, the Ni-O bond lengths decrease uniformly with decreasing temperature, and the atomic displacement parameters are similar to those for $$x = 1/3$$. In contrast, for the sample with $$x = 0.9$$, the out-of-plane Ni-O bond length shows a sharp thermal contraction in the high-temperature region, which is suggestive of changes in the orbital occupation accompanied by the development of checkerboard-type charge correlations. Furthermore, the $$x = 0.9$$ sample is characterized by a large atomic displacement parameter for the apical O atoms along the out-of-plane direction, which is interpreted as the existence of two types of Ni$$^{3+}$$ sites with different orbital occupancies. The distinct difference between the $$x = 0.9$$ sample and the lower-concentration compounds should be related to the development of checkerboard-type charge ordering in the metallic matrix and possible orbital ordering at the Ni$$^{3+}$$ sites at $$x sim 1$$ in the hole-doped layered nickel oxides.

論文

Neutron spectrum change with thermal moderator temperature in a compact electron accelerator-driven neutron source and its effects on spectroscopic neutron transmission imaging

石川 裕卓*; 甲斐 哲也; 佐藤 博隆*; 加美山 隆*

Journal of Nuclear Science and Technology, 56(2), p.221 - 227, 2019/02

 被引用回数:2 パーセンタイル:28.74(Nuclear Science & Technology)

We simultaneously measured neutron spectra and the temperature of a polyethylene moderator at the Hokkaido University Neutron Source (HUNS) driven by a compact electron accelerator to observe the effect of any temperature change on the reliability of spectroscopic transmission measurement. The ratio of the neutron effective temperature and the moderator temperature was constant in HUNS case, although both increased by 4-5 K within one hour after the start of accelerator-operation. This indicated that the neutron effective temperature was well estimated by the moderator temperature. The effect of the temperature change can be easily avoided by excluding data collection before the moderator warms up. These results suggested that the monitoring of moderator temperature is recommended in such neutron sources with a thermal neutron moderator to guarantee reliability of spectroscopic transmission measurement without sacrifices of cost, simplicity and maintainability.

論文

Quantum paramagnet near spin-state transition

富安 啓輔*; 伊藤 菜緒子*; 岡崎 竜二*; 高橋 佑生*; 小野寺 貢*; 岩佐 和晃*; 野島 勉*; 青山 拓也*; 大串 研也*; 石川 喜久*; et al.

Advanced Quantum Technologies (Internet), 1(3), p.1800057_1 - 1800057_7, 2018/12

スピンクロスオーバーとしても知られるスピン状態転移は、様々な物質において重要な役割をもつ。理論的に、低スピンと高スピン状態の境界近傍では、従来とは異なる物理状態を引き起こすと予想されている。しかしながら、外場を印加せずに、基底状態としてほぼ縮退した臨界の状態を実現する系は、いまだに実験的には確認されていない。本研究は、LaCoO$$_{3}$$へのSc置換が、非磁性の低スピン状態を不安定化させ、トランスポートギャップのエンハンスメントと磁気格子膨張、Co-O距離の縮みを伴う異常な常磁性状態を生み出すことを明らかにした。これらの現象は、通常の低スピン・高スピン状態の混合状態ではよく説明できず、スピン状態転移の境界で生じる量子重ね合わせで記述することができる。

論文

Investigation of the electronic structure and lattice dynamics of the thermoelectric material Na-doped SnSe

Wu, P.*; Zhang, B.*; Peng, K. L.*; 萩原 雅之*; 石川 喜久*; 古府 麻衣子; Lee, S. H.*; 組頭 広志*; Hu, C. S.*; Qi, Z. M.*; et al.

Physical Review B, 98(9), p.094305_1 - 094305_7, 2018/09

 被引用回数:7 パーセンタイル:41.03(Materials Science, Multidisciplinary)

熱電材料であるNaドープしたSnSeについて、ARPES, 中性子回折, 中性子非弾性散乱でその電子構造と格子ダイナミクスを測定した結果を報告する。

論文

Measurements of neutronic characteristics of rectangular and cylindrical coupled hydrogen moderators

甲斐 哲也; 加美山 隆*; 平賀 富士夫*; 大井 元貴; 広田 克也*; 鬼柳 善明*

Journal of Nuclear Science and Technology, 55(3), p.283 - 289, 2018/03

 被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)

Extensive simulation calculations were performed in the design studies of the coupled hydrogen moderator for the pulsed spallation neutron source of the Japan Proton Accelerator Research Facility (J-PARC). It was indicated that a para-hydrogen moderator had an intensity-enhanced region at the fringe part, and that pulse shapes emitted from a cylindrical para-hydrogen moderator gave higher pulse-peak intensities with narrower pulse widths than those from a rectangular one without penalizing the time-integrated intensities. To validate the peculiar distribution and advantages in pulse shapes experimentally, some measurements were performed at the neutron source of the Hokkaido University electron linear accelerator facility. It was observed that the neutron intensity was enhanced at edges of the para-hydrogen moderators, whereas it decreased at the same part of the ortho-rich-hydrogen moderator, where the dimension of those moderators was 50 mm in thickness and 120 mm in width and height. The spatial distribution and pulse shapes were also measured for a cylindrical coupled para-hydrogen moderator that has the same dimensions as for the coupled moderator employed for J-PARC. The measured results from the cylindrical moderator were consistent with the results obtained in the design studies for the moderator for J-PARC.

論文

Inverse pole figure mapping of bulk crystalline grains in a polycrystalline steel plate by pulsed neutron Bragg-dip transmission imaging

佐藤 博隆*; 塩田 佳徳*; 諸岡 聡; 戸高 義一*; 足立 望*; 定松 直*; 及川 健一; 原田 正英; Zhang, S.*; Su, Y.; et al.

Journal of Applied Crystallography, 50(6), p.1601 - 1610, 2017/12

 被引用回数:12 パーセンタイル:74.86(Chemistry, Multidisciplinary)

A new mapping procedure for polycrystals using neutron Bragg-dip transmission is presented. This is expected to be useful as a new materials characterization tool which can simultaneously map the crystallographic direction of grains parallel to the incident beam. The method potentially has a higher spatial resolution than neutron diffraction imaging. As a demonstration, a Bragg-dip neutron transmission experiment was conducted at J-PARC on beamline MLF BL10 NOBORU. A large-grained Si-steel plate was used. Since this specimen included multiple grains along the neutron beam transmission path, it was a challenging task for existing methods to analyze the direction of the crystal lattice of each grain. A new data-analysis method for Bragg-dip transmission measurements was developed based on database matching. As a result, the number of grains and their crystallographic direction along the neutron transmission path have been determined.

論文

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

中島 健次; 川北 至信; 伊藤 晋一*; 阿部 淳*; 相澤 一也; 青木 裕之; 遠藤 仁*; 藤田 全基*; 舟越 賢一*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

J-PARC物質・生命科学実験施設の中性子実験装置についてのレビューである。物質・生命科学実験施設には23の中性子ビームポートがあり21台の装置が設置されている。それらは、J-PARCの高性能な中性子源と最新の技術を組み合わせた世界屈指の実験装置群である。このレビューでは、装置性能や典型的な成果等について概観する。

論文

Colossal negative thermal expansion induced by magnetic phase competition on frustrated lattices in Laves phase compound (Hf,Ta)Fe$$_2$$

Li, B.; Luo, X. H.*; Wang, H.*; Ren, W. J.*; Yano, S.*; Wang, C.-W.*; Gardner, J. S.*; Liss, K.-D.*; Miao, P.*; Lee, S.-H.*; et al.

Physical Review B, 93(22), p.224405_1 - 224405_6, 2016/06

 被引用回数:37 パーセンタイル:84.95(Materials Science, Multidisciplinary)

Competition between ferromagnetic and antiferromagnetic phases on frustrated lattices in hexagonal Laves phase compound Hf$$_{0.86}$$Ta$$_{0.14}$$Fe$$_2$$ is investigated by using neutron diffraction as a function of temperature and magnetic fields and density-functional-theory calculations. At 325 K, the compound orders into the 120$$^{circ}$$ frustrated antiferromagnetic state with well-reduced magnetic moment and an in-plane lattice contraction simultaneously sets in. With further cooling down, however, the accumulated distortion in turn destabilizes this susceptible frustrated structure. The frustration is completely relieved at 255 K when the first-order transition to the ferromagnetic state takes place, where a colossal negative volumetric thermal expansion, $$-123 times 10^{-6}$$/K, is obtained. Meanwhile, the antiferromagnetic state can be suppressed by few Tesla magnetic fields, which results in a colossal positive magnetostriction. Such delicate competition is attributed to the giant magnetic fluctuation inherent in the frustrated antiferromagnetic state. Therefore, the magnetoelastic instability is approached even under a small perturbation.

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