Unveiling the effects of Mn, Cr, Al, and Si on the low-temperature tempering behaviors of high-carbon martensite

Zhang, Y.*; 丸澤 賢人*; 工藤 航平*; 諸岡 聡; Gong, W.; Harjo, S.; 宮本 吾郎*; 古原 忠*

Journal of Materials Science & Technology, 275, p.250 - 259, 2026/12

https://doi.org/10.1016/j.jmst.2026.04.015

This study examines how substitutional alloying elements (Mn, Cr, Al, and Si) influence low-temperature tempering reactions in high carbon martensitic steels. Through comprehensive experimental techniques including neutron diffraction et al., the work clarifies how alloying modifies tempering kinetics by affecting carbon diffusion and phase nucleation. Al and Cr strongly suppress martensite tetragonality reduction and carbon redistribution, while retained austenite decomposes in two stages that are selectively delayed by different alloying elements. Overall, the tempering sequence and kinetics are shown to be governed by alloying-dependent control of carbon mobility and phase transformations.

Bulk modulus and electron density distribution of high-pressure polymorphs of Fe-Ti-O minerals

山中 高光*; 服部 高典

Physics and Chemistry of Minerals, 53(3), p.21_1 - 21_11, 2026/09

https://doi.org/10.1007/s00269-026-01350-2

Fe-Ti-O鉱物(FeO磁鉄鉱、FeTiOウルボスピネル、FeTiOイルメナイト、FeTiO疑似ブロカイト)の高圧多形体の体積弾性率および電子密度分布を、X線および中性子回折法を用いて調べた。すべての構造において、単位格子内の空孔サイトの体積は陽イオンサイトよりもはるかに大きい。Ti原子によって部分的に占拠された陽イオンサイトは、Fe原子のみの場合よりもが小さく、Ti含有量の増加に伴い単位格子の圧縮率は増加する。空孔サイトの圧縮率は単位格子のそれに近いものの、陽イオンサイトのそれよりはるかに小さい。これらの鉱物の陽イオンサイトにおける強い電子相関を解明するため、高圧条件下での構造変化を調査した。本高圧実験により、電子スピンの高スピン-低スピン遷移、ヤーン・テラー効果、およびFe-O結合における混成といった構造変化が解明された。分子軌道計算により、八面体陽イオンサイトにおける混成が観測され、これが八面体陽イオンサイトの変形を引き起こし、高圧多形における構造変化の引き金となっている。

核医学検査薬(テクネチウム製剤)の国産化に係る基礎基盤技術の開発,2; 第3期報告書(20212025年度)

つくば特区プロジェクト6会合メンバー*

JAEA-Review 2026-012, 96 Pages, 2026/06

JAEA-Review-2026-012.pdf:20.51MB

2011年12月に内閣総理大臣によって「総合特別区域」につくば市と茨城県内の一部の地域が指定され、つくば国際戦略総合特区として、つくばの科学技術の集積を活用したライフイノベーションやグリーンイノベーションの推進による産業化を推進するため、9つの先進的な研究開発プロジェクトが進められた。2013年10月からプロジェクトの1つである「核医学検査薬(テクネチウム製剤)の国産化」が日本原子力研究開発機構をプロジェクトリーダーとして、関係機関と連携して研究開発が開始された。本プロジェクトは、診断薬として用いられている放射性同位元素のテクネチウム-99m(Tc)原料であるモリブデン-99(Mo)の国産化を目指した基礎基盤技術の確立を目的として開発を実施した。本報告書は、第3期計画(20212025年度)期間に実施した活動結果をまとめたものである。

Pulsed-neutron imaging study of a naginata from the Edo Period and spears from the Muromachi Period

及川 健一; 松本 吉弘*; 佐藤 博隆*; 渡辺 賢一*; Parker, J. D.*; 篠原 武尚; 鬼柳 善明*

JPS Conference Proceedings (Internet), 45, p.011047_1 - 011047_8, 2026/06

https://doi.org/10.7566/JPSCP.45.011047

Our Japanese sword research team is attempting to gain insight into the secrets of sword-making techniques by conducting systematic nondestructive study from the viewpoint of crystallographic structure, mainly using the energy-resolved neutron imaging system, RADEN at J-PARC. In particular, the manufacturing process of old swords 'Koto' up to the end of the 16th century is not well understood because there are few written records of the sword making process, and it would be an important clue to clarify how the crystallographic structure differs compared to after the 16th century. With the cooperation of NITROPLUS Co., Ltd., we have started the neutron imaging experiment of swords of known provenance and era from 2021. So far, they have provided us with a total of ten exhibition-class swords. In this presentation, we will report on the analysis results of Bragg-edge imaging and neutron tomography of these swords, Naginata and spear, which are sword-related weapons closely related to the Japanese sword but made in different ways.

Ice IV from supercooled water; Reproducible crystallization, structure, and ordering

小林 大輝*; 小松 一生*; 伊藤 颯*; 町田 真一*; 服部 高典; 鍵 裕之*

Journal of Physical Chemistry C, 130(25), p.8795 - 8805, 2026/06

https://doi.org/10.1021/acs.jpcc.6c00737

氷IVは、氷の高圧下における準安定相であり、水から結晶化することは極めて稀であるため、「ウィル・オ・ザ・ウィスプ(幻灯)」という愛称で呼ばれており、これは氷の不安定で幽霊のような形態を表している。本研究では、水-油エマルジョンを用いた実験により、0.45GPaから1.1GPaの圧力下において、液体の水が均一核生成温度()で再現性よく、かつ選択的に氷IVへと結晶化することを報告する。圧力による氷Ihの融解とそれに続く再結晶化を追跡することで、以下であっても液体の水が優先的に氷IVへと結晶化することを示した。乳化氷試料における高い静水圧状態と結晶成長の抑制により、中性子回折法を用いて氷IVおよびその潜在的な水素配列状態の両方について、信頼性の高い構造解析を行うことができた。実験で達成可能な配列度は極めて低く、結晶化方法にほとんど依存しなかった。

Superior TRIP effect in a duplex stainless steel and its mechanism studied by neutron diffraction experiments

土田 紀之*; 藤田 晃徳*; 平川 直樹*; 濱田 純一*; 石丸 栄一郎*; Gong, W.; 川崎 卓郎; Harjo, S.

Materials Characterization, 236, p.116436_1 - 116436_13, 2026/06

https://doi.org/10.1016/j.matchar.2026.116436

This study investigated the transformation-induced plasticity (TRIP) effect in duplex stainless steel (DSS), focusing on the influence of deformation temperature on the mechanical properties of 24Cr-5Ni-0.18N DSS. The steel showed an excellent balance of tensile strength and uniform elongation below 183 K due to deformation-induced martensitic transformation (DIMT) of the austenite () phase. The superior TRIP effect was attributed not only to DIMT and enhanced stress and work hardening at lower temperatures, but also to changes in phase interactions and texture evolution. DIMT suppressed crystal rotation, altered stress partitioning among constituent phases, and weakened the texture of the and ' phases. In JIS-SUS329J4L, phase stress, work hardening, and KAM values increased with decreasing temperature, while the texture weakened.

Sommerfeld coefficient enhancement and magnetic short-range order in a hyperkagome 3 system

社本 真一*; 安井 幸夫*; 吉澤 香奈子*; 野田 幸男*; 高橋 美和子*; 大貫 惇睦*; 芳賀 芳範; 石角 元志*; 山内 宏樹; Huang, T.-C.*; et al.

Physical Review B, 113(23), p.235126_1 - 235126_7, 2026/06

https://doi.org/10.1103/m5pw-ghz3

-Mn shows a large Sommerfeld constant of 70 mJ,,Mn,,K, which is one of the largest values in 3-electron systems. Although the origin has been attributed to the fluctuating magnetic moment, there are no material-dependent systematic studies in the 3-electron systems except for doped -Mn. The ordered -Mn structure compounds MnTX (T = Co, Rh, Ir; X = Si, Ge) also exhibit the enhancement. We have studied the enhancement in MnTX system. The enhancement has been often accompanied with magnetic short-range order. The mechanism of the magnetic short-range order is discussed based on the phase diagrams of MnTX system. The phase diagrams are categorized in two groups. One group of MnCoSi and MnRhSi exhibits the magnetic short-range order above the Nel temperature, whereas the others do not. The two groups can be separated by the spin-orbit coupling value, regardless of the cubic lattice parameter.

Fast local motions and their transitions in polybutadiene across the glass transition

菊地 龍弥*; 間下 亮*; 増井 友美*; 金谷 利治*; 岸本 浩通*; 中島 健次

Physical Review E, 113(6), p.065418_1 - 064518_10, 2026/06

https://doi.org/10.1103/tg7v-hw13

準弾性中性子散乱において最近開発した修正モード分布解析により、ガラス状態から液体(ゴム状)状態までの広範囲にわたるポリブタジエンの局所的な力学を調べた。サブピコ秒の高速な過程は局所拡散モデルを用いて解析し、局所拡散係数と調和ポテンシャル剛性という物理的に意味のある2つのパラメータを通じて動力学を特徴付けた。温度依存解析により、ガラス遷移付近で明確な動的遷移が見られ、これは複数のセグメントに関わる協同拡散の消失と解釈される。さらに、局所拡散モデル内の高次モードとして、エクストラファストプロセスと呼ばれる追加の緩和モードが特定された。これらの発見は、ガラス遷移を通じた局所的な運動の進化に関する統一された物理的枠組みを示唆し、サブナノメートルおよびサブピコ秒スケールでのポリマーダイナミクスを定量化するための堅牢な手法を確立するものである。

Interpretation of lanthanoid oxide and hydroxide solubilities based on their bulk and surface properties

小林 大志*; Moniruzzaman, M.*; 元川 竜平; 佐々木 隆之*

Applied Geochemistry, 202, p.106780_1 - 106780_11, 2026/05

https://doi.org/10.1016/j.apgeochem.2026.106780

The geochemical environment for lanthanide (Ln) oxides and hydroxides involves aquatic system processes where Lns are mobilized or immobilized by dissolution and precipitation. In the current study, solubility experiments were performed using lanthanum (La), europium (Eu), and thulium (Tm) oxides as starting materials in the undersaturation method and La, Eu, and Tm nitrate solutions as starting materials in the oversaturation method. After aging at 25 or 90C for given periods, the crystal structure, particle size, and solid-phase surface-charge states were investigated to interpret the La, Eu, and Tm solubilities. In aqueous systems, La is stable as La(OH)(cr), which dominates the bulk structure, surface-charge state, and solubility. In the oversaturation method at 25C, the presence of fine primary La(OH)(cr,np) particles with higher solubility was observed, suggesting the possible particle-size effect. However, in the undersaturation method at 90C, the surface-charge state was found to be more negative than that of other solid phases, resulting in lower solubility. The EuO and Eu(OH) stabilities are competitive in aqueous systems. The bulk solid phase was Eu(OH)(cr) in the oversaturation method at 25 and 90C, and in the undersaturation method at 90C, whereas the surface-charge state appeared to be controlled by EuO when aged at 90C. The stability of TmO increased further, so that TmO(cr) dominated the bulk, surface-charge state, and solubility, aged at both 25 and 90C in the undersaturation method. In contrast, Tm(OH)(am) was formed using the oversaturation method and dominated the bulk, surface-charge state, and solubility at both temperatures. These findings are expected to provide important clues for understanding the evolution of lighter-to-heavier Ln oxides and hydroxides in aqueous systems, which is important for radioactive waste disposal.

Collapse of Jahn-Teller phonons in LaSrMnO with weak magnetoresistance

Sterling, T. C.*; Savici, A. T.*; 梶本 亮一; 池内 和彦*; Khan, N.*; Weber, F.*; Reznik, D.*

Communications Materials (Internet), 7, p.121_1 - 121_11, 2026/05

https://doi.org/10.1038/s43246-026-01139-4

We investigated phonons and spin-phonon coupling in ferromagnetic colossal magnetoresistance (CMR) manganites LaSrMnO () that have a relatively small CMR associated with the melting of the magnetic order above room temperature. High-resolution neutron scattering experiments combined with density functional theory (DFT) show that the low-temperature ferromagnetic phase is conventional: neutron scattering intensities from phonons agree with DFT predictions, magnons follow sinusoidal dispersions, and no phonon-magnon hybridization occurs. Fluctuations of Mn moments and low-energy phonons involving Mn and La vibrations remain conventional in the high temperature paramagnetic phase, indicating that the Mn and La/Sr sublattices are not strongly perturbed by the melting of magnetic order. In sharp contrast, the Jahn-Teller active optical oxygen vibrations collapse entirely above the Curie temperature, in spite of the low CMR in these compositions, with at least part of the lost spectral weight reappearing as quasielastic scattering. We attribute this highly anomalous behavior to giant electron-phonon coupling (EPC) in the charge and/or orbital channel. It drives cooperative diffusive motion of quasistatic carrier-trapping oxygen sublattice distortions once ferromagnetism disappears. We hypothesize that the magnitude of magnetoresistance correlates with the rate of this diffusion rather than with the strength of Jahn-Teller EPC.