Phase diagram of the polystyrene/near-critical water system

柴田 基樹*; 竹中 幹人*; 元川 竜平; 熊田 高之; 上田 祐生; 宮崎 司*; 中西 洋平*; 阿部 淳*; 岩瀬 裕希*; 柴山 充弘*; et al.

Polymer, 340, p.129203_1 - 129203_7, 2025/12

https://doi.org/10.1016/j.polymer.2025.129203

The development of effective plastic degradation methods is crucial to address environmental pollution. Hydrothermal liquefaction using near-critical water is a promising technology, but the fundamental dissolution and decomposition mechanisms remain poorly understood. This study investigates the thermodynamics of a polystyrene (PS)/water system under near-critical conditions to elucidate this mechanism. We performed in situ small-angle neutron scattering (SANS) to observe the swelling of PS particles in deuterated water (DO) at various temperatures under pressures of 10 MPa and 25 MPa. By applying the (FHS) theory to the swelling data, We quantitatively determined the Flory-Huggins interaction parameter as a function of temperature and pressure by applying the FHS theory to the swelling data. Based on these results, we constructed a phase diagram of the PS/DO system. The diagram reveals that miscibility increases with increasing pressure. This work provides a thermodynamical properties of water solutions of polymers under near-critical conditions for optimizing industrial hydrothermal recycling processes.

Confined water distribution in the ionomer within the catalyst layers of polymer electrolyte fuel cells; A Small-angle neutron scattering study

岩瀬 裕希*; 有馬 寛*; 原田 雅史*; 熊田 高之

Chemical Engineering Journal, 510, p.161321_1 - 161321_11, 2025/04

https://doi.org/10.1016/j.cej.2025.161321

The humidity dependence of the structure of catalyst-coated membranes in polymer electrolyte fuel cells (PEFCs) was investigated using small-angle neutron scattering (SANS). The results showed that the water volume in the ionomer linearly increases with humidity from an intermediate humidity (50% RH), reaching values similar to those observed in the polymer electrolyte membrane (PEM) at 80% RH. Time-resolved SANS reveals that the catalyst layer binds water more strongly than the PEM. Water distribution in the ionomers within the catalyst layers of an operating PEFC (80 degree, 80% RH) increased with the increase in the current density, affecting its PEFC performance. The behavior of the water distribution in the catalyst layers was closer to that of the water distribution in the gas diffusion layers than that in the PEM.

Low-background ultrahigh-purity aluminium window for small-angle neutron scattering using monochromatic cold neutrons

熊田 高之; 元川 竜平; 岩瀬 裕希*

Journal of Applied Crystallography, 57(Part 3), p.728 - 733, 2024/06

https://doi.org/10.1107/S160057672400373X

We found that intensity of small-angle neutron scattering (SANS) from ultrahigh-purity aluminium (5N-Al) was lower than that from aluminium alloys by a factor of 40 in maximum, and thus replaced a 500 mm-diameter aluminium alloy neutron window by the 5N-Al window at SANS-J. We succeeded in decreasing the intensity of background in range of the magnitude of scattering vector Q between 0.02 and 0.2 nm by a factor of 10 in maximum. This result indicates that, the 5N-Al window, which is made thicker to compensate lower tensile strength, generates much lower background than the aluminium alloy windows. The 5N-Al window is suitable for large-diameter neutron window in SANS diffractometers and windows in their environmental apparatus, which cannot be made of single crystalline silicon due to its poor fracture strength, processability, and/or affinity with metallic materials.

Development of a DO/HO vapor generator for contrast-variation neutron scattering

有馬 寛*; 高田 慎一; 笠井 聡*; 大内 啓一*; 森川 利明*; 宮田 登*; 宮崎 司*; 青木 裕之; 岩瀬 裕希*; 廣井 孝介; et al.

Journal of Applied Crystallography, 56(6), p.1802 - 1812, 2023/12

https://doi.org/10.1107/S1600576723009780

The contrast-variation technique in neutron scattering experiments plays a pivotal role in distinguishing partial structures within multi-component complexes, facilitating the elucidation of distinct sample constituents. This differentiation is achieved using different isotopes, namely hydrogen and deuterium, which possess varying neutron scattering characteristics. This study presents a novel vapor generator designed for neutron scattering experiments, enabling continuous control of the DO/HO ratio of the vapor. This feature is especially useful for contrast-variation studies. The generator features two saturators and four mass flow controllers, allowing for the rapid and independent generation of DO/HO vapors. Additionally, the incorporation of the two-temperature method ensures accurate dew point control within a margin of 0.2Cdp. This setup proves useful for conducting time-resolved experiments and can accelerate research on functional polymers, such as polymer electrolyte membranes for fuel cells, where water potential assumes critical importance.

Study of the and shell gap for Ti and V by the first high-precision multireflection time-of-flight mass measurements at BigRIPS-SLOWRI

飯村 俊*; Rosenbusch, M.*; 高峰 愛子*; 角田 佑介*; 和田 道治*; Chen, S.*; Hou, D. S.*; Xian, W.*; 石山 博恒*; Yan, S.*; et al.

Physical Review Letters, 130(1), p.012501_1 - 012501_6, 2023/01

https://doi.org/10.1103/PhysRevLett.130.012501

The atomic masses of Sc, Ti, and V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For Ti and V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species Ti and V. With the new precision achieved, we reveal the nonexistence of the empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied p orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the d and g orbits and compare the results with conventional shell model calculations, which exclude the g and the d orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at .

Molecular dynamics simulations to quantify the interaction of a rigid and impenetrable precipitate with an edge dislocation in Cu

津川 聖人*; 早川 頌*; 岩瀬 祐樹*; 沖田 泰良*; 鈴木 克幸*; 板倉 充洋; 愛知 正温*

Computational Materials Science, 210, p.111450_1 - 111450_9, 2022/07

https://doi.org/10.1016/j.commatsci.2022.111450

Precipitation strengthening has been utilized to improve the properties of metallic materials so far. Since interactions between precipitates and dislocations are micro-mechanisms responsible for this phenomenon, a molecular dynamics (MD) simulation is a powerful tool for quantifying this phenomenon. In this study, we introduced a method to simulate a rigid and impenetrable precipitate against a direct contact with a dislocation using a single interatomic potential representing the bulk material. The total force exerted on all atoms in the precipitate region was divided by the number of atoms in the region. This average force was then applied to each atom in the region to simulate one super particle that moved depending on the total force exerted by the matrix atoms on the precipitate atoms. We used MD simulations to quantify the interaction of a precipitate with an edge dislocation. After the dislocation overcame the precipitate, an Orowan loop was formed along the outer circumference of the precipitate. The energy of the loop was 2.1 0.1 eV/b, which was higher than that obtained using the elasticity. The hardening caused by the precipitate was larger than that caused by voids of the same size. The proposed method can be applied to simulate interactions of precipitates with dislocations in any type of metallic material, especially when a dislocation bypasses a precipitate without changing its structure, except when a strong repulsive force acts between them.

Activity enhancement of platinum oxygen-reduction electrocatalysts using ion-beam induced defects

木全 哲也*; 垣谷 健太*; 山本 春也*; 下山 巖; 松村 大樹; 岩瀬 彰宏*; Mao, W.*; 小林 知洋*; 八巻 徹也*; 寺井 隆幸*

Physical Review Materials (Internet), 6(3), p.035801_1 - 035801_7, 2022/03

https://doi.org/10.1103/PhysRevMaterials.6.035801

High activity is one of the primary requirements for the catalysts in proton exchange membrane fuel cell applications. Previous computational studies suggested that the catalytic activity of Pt nanoparticles could be enhanced by a Pt-carbon (C) support interaction. We have recently found that an enhanced electronic interaction occurs at the interface between an argon-ion (Ar)-irradiated glassy carbon (GC) surface and Pt nanoparticles. Here, we report a more than two-fold increase in specific activity (SA) for the Pt nanoparticles on the Ar-irradiated GC substrate compared to that on the non-irradiated GC substrate. The mechanism of this activity enhancement was investigated by local structure analysis of the interface. Ar irradiation of the carbon support led to the formation of the Pt-C bonding, thus protecting the deposited Pt nanoparticles from oxidation.

Polarization analysis for small-angle neutron scattering with a He spin filter at a pulsed neutron source

奥平 琢也; 上田 祐生; 廣井 孝介; 元川 竜平; 稲村 泰弘; 高田 慎一; 奥 隆之; 鈴木 淳市*; 高橋 慎吾*; 遠藤 仁*; et al.

Journal of Applied Crystallography, 54(2), p.548 - 556, 2021/04

https://doi.org/10.1107/S1600576721001643

Heスピンフィルタを中性子スピン解析子として使用することにより、パルス中性子源での中性子小角散乱実験において、偏極解析を行うことに成功した。本実験に使用したHeスピンフィルタは中性子小角散乱実験を行うために十分な立体角をカバーすることができ、He偏極緩和時間も数日と長く、これは実験を完遂するために十分な性能である。水素原子による非干渉性散乱は非常に大きく、試料の組成から計算によって非干渉性散乱量を見積もる試みが行われていたが、正確に非干渉性散乱量を決定することは難しかった。しかし本研究では試料内での中性子の多重散乱を考慮した偏極解析実験を行うことで、干渉性散乱と非干渉性散乱を正確に分離することが可能となった。現在までパルス中性子源での中性子小角散乱では、偏極解析の手法が確立されていなかったが、本成果によって、様々な種類の試料に対して干渉性散乱と非干渉性散乱を正確に分離することができるようになると予想される。

Study of quasielastic barrier distributions as a step towards the synthesis of superheavy elements with hot fusion reactions

田中 泰貴*; 森田 浩介*; 森本 幸司*; 加治 大哉*; 羽場 宏光*; Boll, R. A.*; Brewer, N. T.*; Van Cleve, S.*; Dean, D. J.*; 石澤 倫*; et al.

Physical Review Letters, 124(5), p.052502_1 - 052502_6, 2020/02

https://doi.org/10.1103/PhysRevLett.124.052502

The excitation functions for quasielastic scattering of Ne+Cm, Mg+Cm, Ca+U are measured using a gas-filled recoil ion separator The quasielastic barrier distributions are extracted for these systems and are compared with coupled-channel calculations. The results indicate that the barrier distribution is affected dominantly by deformation of the actinide target nuclei, but also by vibrational or rotational excitations of the projectile nuclei, as well as neutron transfer processes before capture. From a comparison between the experimental barrier distributions and the evaporation residue cross sections for Sg (Z=106), Hs (108), Cn (112), and Lv (116), it is suggested that the hot fusion reactions take advantage of a compact collision, where the projectile approaches along the short axis of a prolately deformed nucleus. A new method is proposed to estimate the optimum incident energy to synthesize unknown superheavy nuclei using the barrier distribution.

Proceedings of the 2016 Symposium on Nuclear Data; November 17-18, 2016, High Energy Accelerator Research Organization, Tsukuba, Ibaraki, Japan

佐波 俊哉*; 西尾 勝久; 萩原 雅之*; 岩瀬 広*; 国枝 賢; 中村 詔司

JAEA-Conf 2017-001, 222 Pages, 2018/01

JAEA-Conf-2017-001.pdf:30.89MB

2016年度核データ研究会は、2016年11月17-18日に、茨城県つくば市の高エネルギー加速器研究機構にて開催された。本研究会は、日本原子力学会核データ部会が主催、高エネルギー加速器研究機構、日本原子力研究開発機構原子力基礎工学研究センターと原子力学会北関東支部が共催した。今回、チュートリアルとして「加速器の進化」を、講演・議論のセッションとして「ImPACTプログラム 核変換による高レベル放射性廃棄物の大幅な減容・資源化の概要」、「核データ測定を行う施設と実験」、「核データの測定から応用まで」、「中性子核データの測定と基礎・利用研究の進展」の4件を企画し実施した。さらに、ポスターセッションでは、実験、評価、ベンチマーク、応用など、幅広い研究内容について発表が行われた。参加者総数は65名で、それぞれの口頭発表及びポスター発表では活発な質疑応答が行われた。本報告集は、本研究会における口頭発表10件、ポスター21件の論文をまとめている。