A Lightweight shape-memory alloy with superior temperature-fluctuation resistance

Song, Y.*; Xu, S.*; 佐藤 駿介*; Lee, I.*; Xu, X.*; 大森 俊洋*; 長迫 実*; 川崎 卓郎; 鬼柳 亮嗣; Harjo, S.; et al.

Nature, 638, p.965 - 971, 2025/02

https://doi.org/10.1038/s41586-024-08583-7

In advanced applications like aerospace and space exploration, materials must balance lightness, functionality, and extreme thermal fluctuation resistance. Shape-memory alloys show promise with strength, toughness, and substantial strain recovery due to superelasticity, but maintaining low mass and effective operation at cryogenic temperatures is challenging. We hereby introduce a novel shape-memory alloy that adheres to these stringent criteria. Predominantly composed of Ti and Al with a chemical composition of TiAlCr, this alloy 25 is characterized by a low density (4.3610 kg/m) and a high specific strength (18510 Pam/kg) at room temperature, while exhibiting excellent superelasticity. The superelasticity, owing to a reversible stress-induced phase transformation from an ordered body-centered cubic parent phase to an ordered orthorhombic martensite, allows for a recoverable strain exceeding 7%. Remarkably, this functionality persists across a broad range of temperatures, from deep cryogenic 4.2 K to above room temperature, arising from an unconventional temperature dependence of transformation stresses. Below a certain threshold during cooling, the critical transformation stress inversely correlates with temperature. We interpret this behavior from the perspective of a temperature-dependent anomalous lattice instability of the parent phase. This alloy holds potential in everyday appliances requiring flexible strain accommodations, as well as components designed for extreme environmental conditions such as deep space and liquefied gases.

Giant barocaloric effects in sodium hexafluorophosphate and hexafluoroarsenate

Zhang, Z.*; 服部 高典; Song, R.*; Yu, D.*; Mole, R.*; Chen, J.*; He, L.*; Zhang, Z.*; Li, B.*

Journal of Applied Physics, 136(3), p.035105_1 - 035105_8, 2024/07

https://doi.org/10.1063/5.0211085

バロカロリック材料を用いた固体冷凍は、環境に優しく高効率であるため、過去10年間にわたり世界的に注目されてきた。ここでは、室温付近で立方晶から菱面体晶への相転移を起こすヘキサフルオロ燐酸ナトリウム(NaPF)とヘキサフルオロ砒酸ナトリウム(NaAsF)における巨大バロカロリック効果を報告する。われわれは中性子粉末回折により、NaPFの低温相の構造が空間群Rの菱面体構造であることを明らかにした。NaPFとNaAsFには3つのラマン振動モード(F, E, A)が存在する。相転移温度はNaPF及びNaAsFにおいてそれぞれdT/dP=250K/GPa及び310K/GPaの割合で圧力とともに変化する。NaPFとNaAsFの圧力誘起エントロピー変化は、それぞれ約45.2JkgKと35.6JkgKと決定された。飽和駆動圧力は約40MPaであった。高圧下の中性子粉末回折から、バロカロリック効果は立方晶から菱面体晶への圧力誘起相転移に関係していることが示唆された。

The meson in nuclear matter from theory and experimental data

Gubler, P.; Bratkovskaya, E.*; 市川 真也; Song, T.*

EPJ Web of Conferences, 291, p.04003_1 - 04003_4, 2024/02

https://doi.org/10.1051/epjconf/202429104003

核物質における中間子の性質変化に関する最近の理論的及び実験的な研究を総括し、今後の展望について議論する。われわれの研究の最近の結果についても紹介する。

Microscopic origin of the spin-reorientation transition in the kagome topological magnet TbMnSn

Huang, Z.*; Wang, W.*; Ye, H.*; Bao, S.*; Shangguan, Y.*; Liao, J.*; Cao, S.*; 梶本 亮一; 池内 和彦*; Deng, G.*; et al.

Physical Review B, 109(1), p.014434_1 - 014434_9, 2024/01

https://doi.org/10.1103/PhysRevB.109.014434

TbMnSn is a correlated topological magnet with a Mn-based kagome lattice, in which a Chern gap opens at the Dirac point at low temperatures. The magnetic moment direction of the ferrimagnetic order changes from in the kagome plane to the out-of-plane upon cooling, which is essential for generating the Chern gap, but the underlying mechanism for the spin reorientation remains elusive. Here, we investigate the spin-reorientation transition in TbMnSn using neutron scattering. We provide direct evidence for the spin-reorientation transition and unveil the coexistence of two Tb modes at 200 K. To account for these results, we put forward a model based on SU(N) spin-wave theory, in which there is a temperature evolution of the ground state Tb orbitals, driven by the crystalline electric field, single-ion anisotropy, and exchange interactions between Tb and Mn ions. Our findings shed light on the complex magnetism of TbMnSn, despite its relatively simple ground state magnetic structure, and provide insights into the mechanisms for tuning magnetic topological materials.

meson properties in nuclear matter from dilepton spectra in a transport approach

Gubler, P.; Bratkovskaya, E.*; Song, T.*

EPJ Web of Conferences, 274, p.07015_1 - 07015_6, 2022/12

https://doi.org/10.1051/epjconf/202227407015

There is presently no consensus on how the meson mass and width will change once it is put in a dense environment such as nuclear matter. While many theoretical works exist, connecting them with experimental measurements remains non-trivial task, as the meson in nuclear matter is usually produced in relatively high-energy pA (p: proton, A: nucleus) reactions, which are generally non-equilibrium processes. In this presentation I will report on an ongoing project, attempting to simulate pA reactions in which the meson is produced in nuclei, making use of a transport approach. Results of simulations of 12 GeV/30 GeV p+C and p+Cu reactions will be presented and comparisons between obtained dilepton spectra and experimental data of the E325 experiment at KEK will be made. Furthermore, predictions for the ongoing J-PARC E16 experiment for both dilepton and spectra will be given and discussed.

Hydrogen absorption and desorption on Rh nanoparticles revealed by dispersive X-ray absorption fine structure spectroscopy

Song, C.*; Seo, O.*; 松村 大樹; 廣井 慧*; Cui, Y.-T.*; Kim, J.*; Chen, Y.*; Tayal, A.*; 草田 康平*; 小林 浩和*; et al.

RSC Advances (Internet), 10(34), p.19751 - 19758, 2020/05

https://doi.org/10.1039/D0RA03322G

To unveil the origin of the hydrogen-storage properties of rhodium nanoparticles (Rh NPs), we investigated the dynamical structural change of Rh NPs using dispersive X-ray absorption fine structure spectroscopy (XAFS). The variation of the Rh-Rh interatomic distance and Debye-Waller factor of Rh NPs with a size of 4.0 and 10.5 nm during hydrogen absorption and desorption suggested that they have a different mechanism for hydrogen absorption, which is that the hydrogen absorption on the inner site has a greater contribution than that on a surface for Rh 4.0 nm. In the case of Rh 10.5 nm, it is opposed to Rh 4.0 nm. This study demonstrates a powerful XAFS method for observing small local structural changes of metal nanoparticles and its importance for understanding of the hydrogen-absorption properties of Rh NPs with an interesting hydrogenation mechanism.

Current situation of OECD/NEA, Preparatory Study on Analysis of Fuel debris (PreADES) project

仲吉 彬; Journeau, C.*; Rempe, J.*; Barrachin, M.*; Bottomley, D.; Nauchi, Y.*; Song, J. H.*

Proceedings of 2019 International Workshop on Post-Fukushima Challenges on Severe Accident Mitigation and Research Collaboration (SAMRC 2019) (USB Flash Drive), 6 Pages, 2019/11

In recognition of the broad international interest in learning from post-accident examinations and other activities related to the Fukushima Daiichi Nuclear Power Station (1F), Japan recommended, to the Organization for Economic Co-operation and Development/Nuclear energy Agency/Committee on Safety of Nuclear Installations (OECD/NEA/CSNI) in 2013, that they identified and followed up on opportunities to address safety research gaps. The CSNI set up the Senior Expert Group (SEG) on Safety Research Opportunities Post-Fukushima (SAREF). In 2016-2017, Preparatory Study on Analysis of Fuel Debris (PreADES) project was recommended by the SEG on SAREF as a near-term project. The PreADES project will summarize the collected knowledge and expertise of debris characterization and identify the needs for debris analyses that will most contribute to the decommissioning of 1F. The project also aims to improve the understanding of severe accidents and reactor safety assessments as well as creating appropriate and optimal methodologies for future debris sampling, retrieval, and storage. Consequently, the project provides important input for a future international project of sample examination based on long-term considerations. The PreADES project launched discussions among interested organizations at the preliminary meeting in July 2017 about the objectives, scope, output, and direction of the project. The contents of the PreADES project were agreed as the three following tasks: Task 1: Joint study on fuel debris' expected properties and characterization, Task 2: Identifying needs and major issues for future fuel debris sampling, retrieval, and analyses, Task 3: Planning of future international R&D framework. Currently, 4th meeting took place on July in Tokyo Japan. Task 1 is almost completed and Task 2 will be summarized soon.

Dirac surface state-modulated spin dynamics in a ferrimagnetic insulator at room temperature

Tang, C.*; Song, Q.*; Chang, C.-Z.*; Xu, Y.*; 大沼 悠一; 松尾 衛*; Liu, Y.*; Yuan, W.*; Yao, Y.*; Moodera, J. S.*; et al.

Science Advances (Internet), 4(6), p.eaas8660_1 - eaas8660_6, 2018/06

AA2018-0166.pdf:0.7MB

https://doi.org/10.1126/sciadv.aas8660

This work demonstrates markedly modified spin dynamics of magnetic insulator (MI) by the spin momentum-locked Dirac surface states of the adjacent topological insulator (TI). As the Bi concentration is systematically tuned in 5-nm-thick (BiSb)Te TI films, the weight of the surface relative to bulk states peaks at = 0.32 when the chemical potential approaches the Dirac point. At this concentration, the Gilbert damping constant of the precessing magnetization in 10-nm-thick YFeO MI films in the MI/TI heterostructures is enhanced by an order of magnitude, the largest among all concentrations. In addition, the MI acquires additional strong magnetic anisotropy that favors the in-plane orientation with similar Bi concentration dependence. These extraordinary effects of the Dirac surface states distinguish TI from other materials such as heavy metals in modulating spin dynamics of the neighboring magnetic layer.

The Application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Kristo, M. J.*; Williams, R.*; Gaffney, A. M.*; Kayzar-Boggs, T. M.*; Schorzman, K. C.*; Lagerkvist, P.*; Vesterlund, A.*; Ramebck, H.*; Nelwamondo, A. N.*; Kotze, D.*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.425 - 434, 2018/02

https://doi.org/10.1007/s10967-017-5680-5

最新の核鑑識国際共同試料分析演習では、低濃縮ウラン試料について、10か国の核鑑識ラボラトリーが精製年代測定を実施して良好な結果を得た。これらの測定のうち、3つの異なる核種ペアを用いた精製年代測定も実施された。10か国の核鑑識ラボラトリーが提出した精製年代測定の結果は、実際の精製日と概ね一致した。また、質量分析法による結果は、放射線計測法を用いたものに比べて、高精度な結果を示した。さらに、一部のラボラトリーによって示されたU-Pa法とU-Th法による精製年代測定の結果の一致は、結果の確証性を高めた。

Measurement of neutron production cross sections from heavy ion induced reaction

執行 信寛*; 魚住 祐介*; 今林 洋一*; 板敷 祐太朗*; 佐藤 大樹; 梶本 剛*; 佐波 俊哉*; 古場 裕介*; 高田 真志*; 松藤 成弘*; et al.

JAEA-Conf 2014-002, p.81 - 87, 2015/02

https://doi.org/10.11484/jaea-conf-2014-002

高エネルギー加速器施設の遮蔽設計には、原子力機構を中心に開発されているPHITSや欧州原子核研究機構を中心に開発されているFLUKAなどのモンテカルロ法に基づく放射線輸送コードが利用されている。これら放射線輸送コードの予測精度を検証するには、核反応の素過程に関する二重微分断面積の実験データとの比較が必要である。しかし、重イオン入射反応に関する実験データは乏しく、荷電粒子生成に関するものはほとんど存在しない。そこで、放射線医学総合研究所のHIMAC加速器を用い290MeV/uのAr入射反応に対する炭素原子核からの陽子,重陽子及び三重陽子生成二重微分断面積を測定した。生成した荷電粒子は、ビーム軸に対して15, 30, 45, 60, 75及び90度方向に配置した液体有機シンチレータで検出した。各荷電粒子は、飛行時間と検出器でのエネルギー損失の情報から識別できる。実験データをPHITS及びFLUKAと比較したところ、陽子生成については実験データの傾向を再現するものの、重陽子及び三重陽子生成については、両コードで全く再現できず、各コードによる計算値の間にも大きな差があることが分かった。これは、既存の核反応模型では重陽子や三重陽子の放出に必要な核子の同伴および癒着過程を適切に取り扱えていないためと考えられる。本研究で得られる知見は、放射線輸送コードにおける核反応模型の改良に貢献することが期待できる。