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論文

Sorption mechanism of europium(III) onto metakaolin-based geopolymers

Yildirim, A. C.*; Mei, H.*; 戸田 賀奈子*; 青柳 登; 斉藤 拓巳*

Applied Clay Science, 274, p.107853_1 - 107853_9, 2025/09

https://doi.org/10.1016/j.clay.2025.107853
 被引用回数：0

Metakaolin-based geopolymers (MKGPs) are ceramic-like materials used for nuclear waste stabilization. Therefore, understanding the sorption of ions on MKGPs is crucial where the cation exchange is considered as the main mechanism, yet the studies based on pH are limited. Thus, this study evaluates the effect of pH on the sorption mechanism of Eu(III) onto Na- and K-MKGPs. Here, time-resolved laser fluorescence spectroscopy (TRLFS) combined with parallel factor analysis, TRLFS in mixed D$$_{2}$$O/H$$_{2}$$O matrices, and extended X-ray absorption fine structure analysis. Eu(III) predominantly forms surface complexes with both MKGPs in the pH range of 4 $$sim$$11 at the open air environment, where three distinct surface species were identified at different pH values. The Eu(III) sorption mechanisms of both MKGPs are similar, involving ternary edge-sharing bidentate or monodentate inner-sphere surface complexation of Eu(III) with MKGP and silicate ions released from the MKGP up to pH 8, followed by the precipitation of europium tri-hydroxide within the pores of MKGP. The insights gained from this study will enhance the knowledge on MKGP for pollutant immobilization, thereby mitigating the spread of contaminants in the environment and expanding the potential application areas.

論文

Composition dependence of the anomalous Nernst effect in Fe$$_{4-x}$$Mn$$_{x}$$N and Fe$$_{4-y}$$Co$$_{y}$$N films

Yin, W.*; 伊藤 啓太*; 坪和 優佑*; 辻川 雅人*; 白井 正文*; 梅津 理恵*; 高梨 弘毅

Journal of Magnetism and Magnetic Materials, 628, p.173157_1 - 173157_8, 2025/09

https://doi.org/10.1016/j.jmmm.2025.173157
 被引用回数：0

Fe$$_{4}$$N exhibits a large anomalous Nernst effect (ANE), which motivates a systematic study of enhancing the anomalous Nernst coefficient (S$$_{rm ANE}$$) by modulating its electronic and magnetic structures. In this study, Mn and Co substitution effects for Fe in Fe$$_{4}$$N on S$$_{ANE}$$ were investigated. Fe$$_{4-x}$$Mn$$_{x}$$N and Fe$$_{4-y}$$Co$$_{y}$$N films in wide ranges of x and y were grown epitaxially on MgO(001) and (LaAlO$$_{3}$$)$$_{0.3}$$(Sr$$_{2}$$TaAlO$$_{6}$$)$$_{0.7}$$(001) substrates, respectively, using molecular beam epitaxy. The S$$_{rm ANE}$$ value of the Fe$$_{4}$$N film is suppressed by substituting Fe with Mn or Co. By measuring the ANE, Seebeck effect, and anomalous Hall effect, the transverse thermoelectric conductivity ($$alpha_{xy}$$) was evaluated. The composition dependence of S$$_{ANE}$$ was dominated by the change of $$alpha_{xy}$$ for both Fe$$_{4-x}$$Mn$$_{x}$$N and Fe$$_{4-y}$$Co$$_{y}$$N films. First-principles calculations were conducted for the transverse electric conductivity ($$sigma_{xy}$$) and $$alpha_{xy}$$ of Fe$$_{4}$$N and Fe$$_{3.1}$$Co$$_{0.9}$$N, and large $$alpha_{xy}$$ leading to large S$$_{ANE}$$ was predicted in Fe$$_{3.1}$$Co$$_{0.9}$$N.

論文

Unique deformation behavior of ultrafine-grained 304 stainless steel at 20 K

Mao, W.*; Gong, W.; 川崎 卓郎; Gao, S.*; 伊東 達矢; 山下 享介*; Harjo, S.; Zhao, L.*; Wang, Q.*

Scripta Materialia, 264, p.116726_1 - 116726_6, 2025/07

https://doi.org/10.1016/j.scriptamat.2025.116726
 被引用回数：0

An ultrafine-grained 304 austenitic stainless steel exhibited pronounced serrated Luders deformation at 20 K, with stress and temperature oscillations reaching 200 MPa and 20 K. ${it In-situ}$ neutron diffraction and digital image correlation revealed discontinuous Luders band propagation and burst martensite formation. During deformation, austenite phase stress remained lower than at upper yielding, indicating elastic behavior. Notably, martensite phase stress stayed lower than austenite until fracture, likely due to stress relaxation from burst martensitic transformation at 20 K. The low martensite stress delayed brittle fracture until austenite plastically yielded during uniform deformation.

報告書

燃料ピンバンドル変形解析コードBAMBOOへの被覆管局所変形モデルの導入

上羽 智之; 伊藤 昌弘*; 石谷 行生*

JAEA-Technology 2025-002, 25 Pages, 2025/06

JAEA-Technology-2025-002.pdf:2.06MB

ワイヤスペーサ型の高速炉燃料集合体では、バンドル-ダクト相互作用(Bundle-DuctInteraction; BDI)が厳しくなると、ワイヤを介して被覆管に加わる接触荷重によって被覆管断面の扁平化が生じるようになる。特に、バンドル最外周のピンは、ワイヤを介してダクトから被覆管に加わる荷重が大きくなって、この扁平化が顕著になることがある。この場合、扁平化はワイヤが被覆管にめり込んで被覆管が局所的に窪む状態となる。このような被覆管の局所変形をモデル化し、BDI解析コード"BAMBOO"のピンバンドル変形解析において被覆管の局所変形を考慮できるようにした。炉外バンドル圧縮試験では、バンドル最外周ピンとダクトの間にワイヤが存在するにもかかわらずピンとダクトの隙間がワイヤ径を下回ることが確認されているが、被覆管の局所変形モデルを組込んだBAMBOOコードによるバンドル圧縮試験の解析においても、バンドル最外周ピンの被覆管の局所変形によってバンドル圧縮試験結果と同様の傾向を再現できた。

論文

Magnetism of kagome metals (Fe$$_{1-x}$$Co$$_x$$)Sn studied by $$mu$$SR

Cai, Y.*; Yoon, S.*; Sheng, Q.*; Zhao, G.*; Seewald, E. F.*; Ghosh, S.*; Ingham, J.*; Pasupathy, A. N.*; Queiroz, R.*; Lei, H.*; et al.

Physical Review B, 111(21), p.214412_1 - 214412_17, 2025/06

https://doi.org/10.1103/PhysRevB.111.214412

We study the magnetic properties of the metallic kagome system (Fe$$_{1-x}$$Co$$_x$$)Sn by a combination of muon spin relaxation ($$mu$$SR), magnetic susceptibility, and scanning tunneling microscopy (STM) measurements in single crystal specimens with Co concentrations $$x$$ = 0, 0.11, 0.8. In the undoped antiferromagnetic compound FeSn, we find possible signatures for a previously unidentified phase that sets in at $$T^{*}sim 50$$~K, well beneath the Neel temperature $$T_{N}sim 376$$~K as indicated by a peak in the relaxation rate 1/$$T_1$$ observed in zero field (ZF) and longitudinal field (LF) $$mu$$SR measurements, with a corresponding anomaly in the ac and dc susceptibility, and an increase in the static width 1/$$T_2$$ in ZF-$$mu$$SR measurements. No signatures of spatial symmetry breaking are found in STM down to 7~K. Related to the location and motion of muons in FeSn, we confirmed a previous report that about 40% of the implanted muons reside at a field-cancelling high symmetry site at $$T < 250$$~K, while an onset of thermal hopping changes the site occupancy at higher temperatures. In Fe$$_{0.89}$$Co$$_{0.11}$$Sn, where disorder eliminated the field-cancellation effect, all the implanted muons exhibit precession and/or relaxation in the ordered state. In Fe$$_{0.2}$$Co$$_{0.8}$$Sn, we find canonical spin glass behavior with freezing temperature $$T_gsim 3.5$$~K; the ZF and LF-$$mu$$SR time spectra exhibit results similar to those observed in dilute alloy spin glasses CuMn and AuFe, with a critical behavior of $$1/T_1$$ at $$T_g$$ and $$1/T_1to 0$$ as $$Tto 0$$. The absence of spin dynamics at low temperatures makes a clear contrast to the spin dynamics observed by $$mu$$SR in many geometrically frustrated spin systems on insulating kagome, pyrochlore, and triangular lattices. The spin glass behavior of CoSn doped with dilute Fe moments is shown to originate primarily from the randomness of doped Fe moments rather than due to geometrical frustration of the underlying lattice.

論文

Neutron diffraction study of the crystal and magnetic structures of antiferromagnetic manganese deuteride at high temperatures and high pressures

町田 晃彦*; 齋藤 寛之*; 青木 勝敏*; 小松 一生*; 服部 高典; 佐野 亜沙美; 舟越 賢一*; 町田 真一*; 佐藤 豊人*; 折茂 慎一*

Physical Review B, 111(22), p.224413_1 - 224413_6, 2025/06

https://doi.org/10.1103/yf8k-cy61

Mn金属を高温高圧で水素化することにより形成される反強磁性Mn重水素化物、fcc$$gamma$$-MnDxとhcp$$epsilon$$-MnDxの結晶構造と磁気構造をin-situ中性子粉末回折により調べた。重水素原子はfcc及びhcp金属格子の八面体格子間を部分的に占有していた。N$'{e}$el温度は$$gamma$$-MnD$$_{0.34}$$で543(10)Kであった。$$epsilon$$-MnD$$_{0.62}$$では、飽和磁気モーメントは0.82(1)$$mu_B$$、N$'{e}$el温度は347(3)Kであった。$$gamma$$-MnD$$_{0.34}$$と$$epsilon$$-MnD$$_{0.62}$$について決定されたN$'{e}$el温度は、以前の研究で提案されたそれぞれのSlater-Pauling曲線によって予測されたものと一致した。更新されたN$'{e}$el温度は、電子バンド構造計算に基づくより正確なSlater-Pauling曲線の開発に示唆を与える。

論文

Electrocatalytic nitrous oxide reduction reaction at Sn-modified Pd-Pt single crystalline electrodes in acidic media

加藤 優*; Zheng, J.*; Deng, Y.*; 斎藤 史恵*; 鵜沼 佑規*; 岡 紗雪*; 田村 和久; 八木 一三*

ACS Catalysis, 15(10), p.7710 - 7719, 2025/04

https://doi.org/10.1021/acscatal.5c00379
 被引用回数：0

Nitrous oxide (N$$_{2}$$O) is a greenhouse and an ozone-depleting gas. Electrocatalytic N$$_{2}$$O reduction reaction (N$$_{2}$$ORR) is known to be catalyzed at noble metal electrodes such as Pd and Pt, and the surface modification of such noble metals with Sn is known to increase the N$$_{2}$$ORR in acidic media. However, the role of Sn at the surface remains unclear. In this work, N$$_{2}$$ORR activity was investigated for single-crystalline Pt, Pd, and Pd-Pt electrodes with the (111) or (100) plane in the presence and absence of Sn at the electrode surface in acidic media. In situ X-ray crystal truncation rod (CTR) measurements of Sn-modified Pt(111) and Pd(111) electrodes revealed the presence of metallic Sn and SnO at their surfaces. The surface Sn modification enhances the N$$_{2}$$ORR activity for Pd-Pt(100) or Pd(100) electrodes but not for the Pt(111), Pd-Pt(111), or Pt(100) electrodes.

論文

Role of solute hydrogen on mechanical property enhancement in Fe-24Cr-19Ni austenitic steel; An ${it in situ}$ neutron diffraction study

伊東 達矢; 小川 祐平*; Gong, W.; Mao, W.*; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.

Acta Materialia, 287, p.120767_1 - 120767_16, 2025/04

https://doi.org/10.1016/j.actamat.2025.120767
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Incorporating solute hydrogen into Fe-Cr-Ni-based austenitic stainless steels enhances both strength and ductility, providing a promising solution to hydrogen embrittlement by causing solid-solution strengthening and assisting deformation twinning. However, its impacts on the relevant lattice defects evolution (${it i.e.}$, dislocations, stacking faults, and twins) during deformation remains unclear. This study compared the tensile deformation behavior in an Fe-24Cr-19Ni (mass%) austenitic steel with 7600 atom ppm hydrogen-charged (H-charged) and without hydrogen-charged (non-charged) using ${it in situ}$ neutron diffraction. Hydrogen effects on the lattice expansion, solid-solution strengthening, stacking fault probability, stacking fault energy, dislocation density, and strain/stress for twin evolution were quantitatively evaluated to link them with the macroscale mechanical properties. The H-charged sample showed improvements in yield stress, flow stress, and uniform elongation, consistent with earlier findings. However, solute hydrogen exhibited minimal influences on the evolution of dislocation and stacking fault. This fact contradicts the previous reports on hydrogen-enhanced dislocation and stacking fault evolutions, the latter of which can be responsible for the enhancement of twinning. The strain for twin evolution was smaller in the H-charged sample compared to the non-charged one. Nevertheless, when evaluated as the onset stress for twin evolution, there was minimal change between the two samples. These findings suggest that the increase in flow stress due to the solid-solution strengthening by hydrogen is a root cause of accelerated deformation twinning at a smaller strain, leading to an enhanced work-hardening rate and improved uniform elongation.

論文

Measurement and analysis of long-term variation of atmospheric $$^{7}$$Be activity concentrations in Dazaifu (western Japan)

楢崎 幸範*; 迫田 晃弘; 赤田 尚史*; 伊藤 久徳*; 百島 則幸*

Journal of Environmental Radioactivity, 284, p.107612_1 - 107612_7, 2025/04

https://doi.org/10.1016/j.jenvrad.2024.107612
 被引用回数：0 パーセンタイル：0.00(Environmental Sciences)

大気中$$^{7}$$Be濃度を1999年から2020年まで太宰府市で連続測定し、その変動を解析した。22年間の日変動の範囲は不検出から18mBq/m$$^{3}$$であ、月ごとの大きな変動と平滑化された年変動が特徴的であった。日平均の$$^{7}$$Be濃度のとして、5.0$$pm$$2.6mBq/m$$^{3}$$が30-40$$^{circ}$$Nの地表面レベルの代表値と考えられた。二元配置分散分析(ANOVA)の結果、$$^{7}$$Beの月及び年の変動率に統計的有意性が認められた。$$^{7}$$Be濃度の月変動は年変動の約4倍であった。頻度解析の結果、月変動は主要な12か月周期と微小な6か月周期からなることがわかった。月変動の主な要因である夏季の$$^{7}$$Be濃度の大幅な減少は、日本の他の地点でも観測され、太平洋の安定した高気圧が日本の南海上に停滞した後、低い$$^{7}$$Be濃度の気団が流入したためと考えられた。年変動は、主に$$^{7}$$Beを生成する宇宙線の強度に影響を与える11年の太陽活動周期の影響を受けていた。

論文

Neutron spectroscopy study on crystalline electric field excitations in NdB$$_4$$

山内 宏樹; 目時 直人; 綿貫 竜太*; Hong, T.*; Fernandez-Baca, J. A.*; 萩原 雅人; 益田 隆嗣*; 吉沢 英樹*; 伊藤 晋一*

Journal of the Physical Society of Japan, 94(5), p.054705_1 - 054705_8, 2025/04

https://doi.org/10.7566/JPSJ.94.054705

The $textit{f}$-electron states of NdB$$_4$$ were determined by observing crystalline electric field (CEF) excitations with inelastic neutron scattering experiments. Our analysis yields CEF excitation energies of 2.8, 12.4, 17.2, and 25.4 meV. The $textit{f}$-electron states are simply described by one of $$J$$-multiplets $$left|pm J_z rightrangle$$ with negligibly small mixing. The ground state is the pseudo-quartet consist of the ground doublet dominated by $$left|pm frac{5}{2} rightrangle$$ and the first excited doublet dominated by $$left|pm frac{7}{2} rightrangle$$ at 2.8 meV, which is consistent with magnetic specific heat and entropy reported in earlier study. The simple $textit{f}$-electron states in NdB$$_4$$ are the consequence of the strong uniaxial and in-plane isotropic CEF potential due to the local structure of Nd$$^{3+}$$ ions with point symmetry $$C_{2v}$$.

論文

Mechanical multiplexer of nuclear spin states

中堂 博之; 横井 直人*; 松尾 衛; 針井 一哉*; 鈴木 淳*; 今井 正樹; 佐藤 正寛*; 前川 禎通*; 齊藤 英治*

Physical Review Letters, 134(13), p.130603_1 - 130603_5, 2025/04

https://doi.org/10.1103/PhysRevLett.134.130603
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

A spin 1/2 is the simplest system that has been believed to support a single two-level quantum system, represented by a single resonance. We experimentally demonstrate that a spin-1/2 nucleus of $$^{19}$$F in C$$_{6}$$F$$_{6}$$ exhibits an extra resonance corresponding to the emergence of the states, by mechanically rotating a sample and a coil in nuclear magnetic resonance (NMR) measurements. On the basis of the Floquet formalism, we identify the emergence of the extra two-level state due to the temporal periodicity generated by the mechanical rotation (mechanical spin multiplexing) and derive an operator algebra analogous to the planar rotor algebra in an effective description of the system. The observed multiplexing allows a single spin 1/2 to carry more than two states and potentially enabling the processing of multiple quantum bits on a single spin.

論文

Development of a bio-based adhesive by polymerization of Boc-protected vinyl catechol derived from caffeic acid

谷崎 志帆*; 久保 智弘*; Bito, Yosuke*; 森 茂樹*; 青木 裕之; 佐藤 浩太郎*

RSC Sustainability (Internet), 3(4), p.1714 - 1720, 2025/04

https://doi.org/10.1039/D4SU00629A

Catechol is a functional group that is versatile and abundant in nature, exhibiting various functions. In this report, a tert-butoxycarbonyl (Boc)-protected vinyl catechol (VC) monomer was synthesized from caffeic acid, which is a bio-abundant molecule found generally in coffee beans, in order to develop a bio-based adhesive. Reversible addition-fragmentation chain transfer (RAFT) polymerization of the Boc-protected VC afforded well-defined, bio-based catechol-containing polymers with controlled molecular weights and narrow molecular weight distributions. Specifically, it was facile to deprotect the pendent Boc groups quantitatively under acidic or thermal conditions to provide the desired P(VC) without requiring further purification. Consequently, the catechol-containing polymer as a primer showed highly strong adhesion against aluminum when coupled with a commercially available polyurethane adhesive.

論文

Electronic approach to understand the wettability of surface treated titanium with liquid sodium

浪江 将成; 斉藤 淳一; 岡 涼太郎*; Kim, J.-H.*

Vacuum, 234, p.114038_1 - 114038_9, 2025/04

https://doi.org/10.1016/j.vacuum.2025.114038
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Wettability of titanium (Ti) and surface-modified (Oxidized or Fluorinated) Ti with liquid sodium (Na) were investigated via experiments and theoretical calculations. From the experimental results, a sliding angle of Na droplet on oxidized Ti was smaller than that on untreated Ti, indicating the worsening of wettability by oxidation. In contrast, the sliding angle of Na droplet on fluoridated Ti was larger than that on untreated Ti, indicating an improvement in wettability by fluorination. Additionally, the cluster models for the interface between Na droplets and treated or untreated Ti were constructed for theoretical calculations of electronic states at the interface, covalent and ionic bonds at the interface were evaluated from the calculation results. The sliding angles obtained in the wettability tests and the strength of covalent bonding at the interface showed no correlation, but good correlation was observed between the sliding angles and ionic bonding at the interface. Thus, the wettability of surface-modified Ti with liquid Na can be theoretically understood based on the atomic interactions at the interface.

報告書

J-PARC陽子ビーム照射施設の概念設計

明午 伸一郎; 岩元 大樹; 杉原 健太*; 平野 幸則*; 堤 和昌*; 斎藤 滋; 前川 藤夫

JAEA-Technology 2024-026, 123 Pages, 2025/03

JAEA-Technology-2024-026.pdf:14.22MB

J-PARC核変換実験施設ADSターゲット試験施設(TEF-T)の設計をベースとし、J-PARC陽子ビーム照射施設の概念検討を行った。これは、文部科学省の分離変換技術評価タスクフォースの提言「ADSの工学的課題解決に加え、多様なニーズへの対応の可能性を含め、既存のJ-PARCの陽子加速器を利用可能な利点を最大限活用する施設仕様を検討することが望ましい。」を受けたものである。TEF-T設計で不要となった設備を削減する一方、多様なニーズに対応可能な設備の具体化を行った。多様なニーズとして、諸外国の大強度加速器施設の利用法の調査を行った。その結果、1)材料照射試験、2)核破砕中性子を用いた半導体機器のソフトエラー試験、3)医療用RI製造および4)陽子ビーム利用を主な利用目的と特定し、これらの利用に必要な施設の検討を行った。施設概念の検討にあたっては、2022年に施設のユーザーコミュニティを立ち上げ、ユーザーの意見を広く取り入れて施設設計に反映した。本報告書は、陽子ビーム照射施設の概念検討結果、多様なニーズとその対応、施設建設に向けたロードマップおよび今後の課題についてまとめたものである。

論文

Reduction and phase transformation of Ce-doped zirconolites

林崎 康平; 廣岡 瞬; 山田 忠久*; 砂押 剛雄*; 村上 龍敏; 齋藤 浩介

Ceramics (Internet), 8(1), p.24_1 - 24_12, 2025/03

https://doi.org/10.3390/ceramics8010024

Zirconolite is a wasteform that can immobilize Pu. Herein, zirconolites comprising Ce as a Pu simulant and Al as a charge compensator of Ce/Pu were synthesized by sintering raw CaO, ZrO$$_{2}$$, TiO$$_{2}$$, CeO$$_{2}$$, and Al$$_{2}$$O$$_{3}$$ powder mixtures at 1400$$^{circ}$$C in static air. The reduction behavior and phase transformation of zirconolites during their heat treatment in an Ar-H$$_{2}$$ gas flow were investigated. All zirconolite compositions first underwent reduction at $$sim$$ 1050$$^{circ}$$C by forming a small domain of perovskite phase. Ce-Al co-doped zirconolite showed a smaller fraction of phase transformation in perovskite than Ce-doped zirconolite, indicating the advantage of using a charge compensator to prevent perovskite formation.

論文

Multiple DNA damages induced by water radiolysis demonstrated using a dynamic Monte Carlo code

甲斐 健師; 樋川 智洋; 松谷 悠佑*; 平田 悠歩; 土田 秀次*; 伊東 佑真*; 横谷 明徳*

Communications Chemistry (Internet), 8, p.60_1 - 60_9, 2025/03

https://doi.org/10.1038/s42004-025-01453-x
 被引用回数：1 パーセンタイル：0.00(Chemistry, Multidisciplinary)

放射線DNA損傷は、直接効果と間接効果から形成される。直接効果はDNAと放射線の相互作用であり、間接効果はDNAと放射線分解化学種との化学反応である。これまで、直接効果が関与すると、DNAの10塩基対以内(3.4nm程度)に複数の損傷が形成され、修復効率が低下し、生物影響が誘発されると考えられてきた。本研究では、間接効果のみにより誘発されるDNA損傷を定量的に評価した。その結果、生成される確率は1%未満であるが、DNA近傍の水に10数eVのエネルギーが付与されるだけで、複雑なDNA損傷が形成されることが分かった。つまり、放射線とDNAが直接相互作用することなく、DNAの極近傍の水にエネルギーを与えるだけで、後発の生物影響の可能性を排除できなくなる。本研究成果は、低線量放射線影響の理解に役立つ重要な知見の一つとなる。

論文

Direct measurement of lattice behavior during femtosecond laser-driven shock front formation in copper

江頭 尚弥*; 松田 朋己*; 奥地 拓生*; 瀬戸 雄介*; 伊藤 佑介*; 菖蒲 敬久; 中新 信彦*; 佐野 智一*; 他4名*

Journal of Applied Physics, 137(10), p.105903_1 - 105903_8, 2025/03

https://doi.org/10.1063/5.0253150
 被引用回数：1 パーセンタイル：0.00(Physics, Applied)

Femtosecond laser-driven shock waves exhibit characteristic features that form distinctive microstructures not formed by plate impacts or nanosecond laser-driven shock waves. A key to understanding this phenomenon is understanding the lattice behavior inside the shock front, which is the boundary between the ambient and shock compression states. However, direct measurements of the lattice spacing inside a femtosecond laser-driven shock front have not yet been performed. Here, we report ${it in-situ}$ measurements of lattice spacing using X-ray free electron laser diffraction with a pulse width of $$<$$ 10 fs during the shock rise in single-crystal copper irradiated directly in air with a femtosecond laser pulse on the order of 10$$^{14}$$ W/cm$$^{2}$$ at a pulse width of 101 fs. The lattice spacing of the femtosecond laser-irradiated single-crystal Cu (002) plane starts to compress 6.3 ps after femtosecond-laser irradiation. It takes 15.7 ps for the plane to reach peak compression, at which point the compressive elastic-strain is 24.3%. Therefore, the shock front was found to form at an elastic compressive strain rate of 1.55$$times$$10$$^{10}$$ /s in this shock-driving situation. It is suggested that the initiation of plasticity under such ultrafast deformation at the most elastic compression is based on both dislocation multiplication and dislocation generation mechanisms.

論文

Redox control in arsenic accumulation with organic matter derived from a varved lacustrine deposit in the Jurassic accretionary complexes

益木 悠馬*; 勝田 長貴*; 内藤 さゆり*; 村上 拓馬*; 梅村 綾子*; 藤田 奈津子; 松原 章浩*; 南 雅代*; 丹羽 正和; 吉田 英一*; et al.

Journal of Hazardous Materials, 485, p.136843_1 - 136843_10, 2025/03

https://doi.org/10.1016/j.jhazmat.2024.136843
 被引用回数：0 パーセンタイル：0.00(Engineering, Environmental)

滋賀県東部の姉川上流域には、伊吹山の斜面崩壊でせき止められて生じた2つの湖成層の河岸段丘が分布する。このうち、下位の湖成層は、植物遺体のC-14年代測定から完新世中期に形成されたことが明らかとなった。また、湖成層の岩相は、mmスケールの縞状構造に富む層が10cmオーダーでシルト質粘土層と互層し、化学分析からヒ素が大陸地殻の約30倍の濃度(77$$mu$$g/g)で濃集する。さらに、蛍光X線やX線吸収分光などを用いた微小領域測定から、縞状構造は1年に1枚の縞を刻む年層であること、ヒ素は春季と秋季の循環期に堆積したこと、ヒ素は硫化物として存在し非晶質有機物と共存することなどが示された。これらの結果から、年縞のヒ素濃集は、季節変動に伴う有機物の供給と、続成過程における有機物分解によるレドックス変動によって生じたことが明らかとなった。

論文

鉄水素化物の中性子回折の10年

青木 勝敏*; 町田 晃彦*; 齋藤 寛之*; 服部 高典

高圧力の科学と技術, 35(1), p.4 - 11, 2025/03

https://doi.org/10.4131/jshpreview.35.4

鉄は水素と反応して、高温高圧下で体心立方、面心立方、六方最密充填、二重六方最密充填構造の固溶体を形成する。中性子回折は、金属格子中に溶解した水素原子の占有位置と占有率を決定するための最も強力なツールである。水素の占有位置や占有率を含む構造パラメータは、中性子回折データのリートベルト解析によって精密化される。本原稿では、10年以上にわたって蓄積してきた鉄水素化物のリートベルト精密化に関するノウハウを紹介する。

論文

Spontaneous magnetic field and disorder effects in BaPtAs$$_{1-x}$$Sb$$_x$$ with a honeycomb network

足立 匡*; Ogawa, Taiki*; 小宮山 陽太*; 須村 拓也*; Saito-Tsuboi, Yuki*; Takeuchi, Takaaki*; Mano, Kohei*; Manabe, Kaoru*; 川端 幸樹*; 今津 毅士*; et al.

Physical Review B, 111(10), p.L100508_1 - L100508_6, 2025/03

https://doi.org/10.1103/PhysRevB.111.L100508
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Chiral superconductivity exhibits the formation of novel electron pairs that breaks the time-reversal symmetry and has been actively studied in various quantum materials in recent years. However, despite its potential to provide definitive information, effects of disorder in the crystal structure on the chiral superconductivity has not yet been clarified, and therefore the investigation using a solid-solution system is desirable. We report muon-spin-relaxation ($$mu$$SR) results of layered pnictide BaPtAs$$_{1-x}$$Sb$$_x$$ with a honeycomb network composed of Pt and (As, Sb). We observed an increase of the zero-field $$mu$$SR rate in the superconducting (SC) state at the Sb end of $$x=1.0$$, suggesting the occurrence of a spontaneous magnetic field due to the time-reversal symmetry breaking in the SC state. On the other hand, a spontaneous magnetic field was almost and completely suppressed for the As-Sb mixed samples of $$x=0.9$$ and 0.2, respectively, suggesting that the time-reversal symmetry-breaking SC state in $$x=1.0$$ is sensitive to disorder. The magnetic penetration depth estimated from transverse-field $$mu$$SR measurements at $$x=1.0$$ and 0.2 behaved like weak-coupling $$s$$-wave superconductivity. These seemingly incompatible zero-field and transverse-field $$mu$$SR results of BaPtAs$$_{1-x}$$Sb$$_x$$ with $$x=1.0$$ could be understood in terms of chiral $$d$$-wave superconductivity with point nodes on the three-dimensional Fermi surface.

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