Crystal-like atomic arrangement and optical properties of 25LaO-75MoO binary glasses composed of isolated MoO

Masuno, Atsunobu*; Munakata, Sae*; Okamoto, Yoshihiro; Yaji, Toyonari*; Kosugi, Yoshihisa*; Shimakawa, Yuichi*

Inorganic Chemistry, 63(12), p.5701 - 5708, 2024/03

https://doi.org/10.1021/acs.inorgchem.4c00176

Transparent and brown LaO-MoO binary glasses were prepared in bulk form using a levitation technique. The glass-forming range was limited, with the primary composition being approximately 25 mol% LaO. This glass exhibited a clear crystallization at 546 C, while determining its glass transition temperature was difficult. Notably, despite its amorphous nature, the glass possessed a density and packing density comparable to those of crystalline LaMoO. X-ray absorption fine structure and Raman scattering analyses revealed that the glass structure closely resembles LaMoO due to the presence of isolated MoO units, whereas disordered atomic arrangement around La atoms was confirmed. The glass demonstrated transparency ranging from 378 to 5500 nm, and the refractive index at 1.0 m was estimated to be 2.0. The optical bandgap energy was 3.46 eV, which was slightly smaller than that of LaMoO. Additionally, the glass displayed a transparent region ranging from 6.5 to 8.0 m. This occurrence results from the decreased diversity of MoO units and connectivity of Mo-O-Mo, which resulted in the reduced overlap of multiphonon absorption. This glass formation, with its departure from conventional glass-forming rules, resulted in distinctive glasses with crystal-like atomic arrangements.

Recrystallization of bulk nanostructured magnesium alloy AZ31 after severe plastic deformation; An in situ diffraction study

Liss, K.-D.*; Han, J.-K.*; Blankenburg, M.*; Lienert, U.*; Harjo, S.; Kawasaki, Takuro; Xu, P. G.; Yukutake, Eitaro*; Kawasaki, M.*

Journal of Materials Science, 23 Pages, 2024/00

https://doi.org/10.1007/s10853-023-09250-4

Automation of precise gas control for material-process researches; Application to synchrotron radiation real-time observation of surface reactions

Nakamura, Takafumi*; Yamamoto, Yukio*; Arakawa, Masakazu*; Maruyama, Akio*; Yoshigoe, Akitaka

Sangyo Oyo Kogakukai Rombunshi, 11(2), p.109 - 114, 2023/09

https://doi.org/10.12792/jjiiae.11.2.109

Surface chemistry experimental end-station at BL23SU in SPring-8 is widely used to study various surfaces and interfaces of functional materials by means of soft X-rays synchrotron radiation. To analyze surface chemical reactions between gas and solid surfaces, an accurate control of flow-rates of gases is essential. This paper describes a computerized automatic gas flow control system to improve the accuracy and reproducibility of gas-surface reaction experiments in the pressure range of ultra-high vacuum (molecular flow) conditions. The system uses feedback control to operate the slow-leak valve to control the gas-pressure. As a result, the system achieved results equivalent to those of a skilled experimenter.

Work function lowering of LaB by monolayer hexagonal boron nitride coating for improved photo- and thermionic-cathodes

Yamaguchi, Hisato*; Yusa, Ryunosuke*; Wang, G.*; Pettes, M. T.*; Liu, F.*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Abukawa, Tadashi*; Moody, N. A.*; Ogawa, Shuichi*

Applied Physics Letters, 122(14), p.141901_1 - 141901_7, 2023/04

https://doi.org/10.1063/5.0142591

A lowering of work function for LaB by monolayer hexagonal BN coating is reported. Photoemission electron microcopy (PEEM) and thermionic emission electron microscopy (TEEM) both revealed that the hBN coated region of a LaB(100) single crystal has lower work function compared to the bare (i.e., non-coated) and graphene coated regions. A larger decrease of work function for the hBN coated LaB(100) compared to graphene coated LaB(100) was qualitatively supported by our density functional theory (DFT) calculations. Adding an oxide layer in the calculations improved consistency between the calculation and experimental results. We followed up our calculations with synchrotron-radiation X-ray photoelectron spectroscopy (SR-XPS) and confirmed the presence of an oxide layer on our LaB.

Assessment report on research and development activities in FY2021 Activity: "Research and development in science and technology using neutron and synchrotron radiation" (Ex-ante evaluation)

Materials Sciences Research Center

JAEA-Evaluation 2022-013, 105 Pages, 2023/03

JAEA-Evaluation-2022-013.pdf:13.08MB

Japan Atomic Energy Agency (hereafter referred to as "JAEA") consulted an assessment committee, "Evaluation Committee of Research Activities for Research and Development in Science and Technology Using Neutron and Synchrotron Radiation" (hereafter referred to as "Evaluation Committee") for ex-ante evaluation of "Research and Development in Science and Technology Using Neutron and Synchrotron Radiation", in accordance with "General Guideline for the Evaluation of Government Research and Development (R&D) Activities" by Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in Ministry of Education, Culture, Sports, Science and Technology" and "Regulation on Conduct for Evaluation of R&D Activities" by JAEA. In response to the JAEA's request, the Committee assessed the research program and activities on Research and Development in Science and Technology Using Neutron and Synchrotron Radiation in Materials Sciences Research Center (MSRC) and Neutron Science Section (NSS) in Materials and Life Science Division (MLSD) of J-PARC Center during the period from April 2022 to March 2029. The Committee evaluated the management, research and development activities based on the explanatory documents prepared by MSRC and NSS and oral presentations with questions-and-answers by the Director General and the Division Heads of the MSRC and the Deputy Director General and the NSS Section Leader of J-PARC Center. This report summarizes the results of the assessment by the Evaluation Committee with the Committee report attached.

Abnormal grain growth; A Spontaneous activation of competing grain rotation

Liss, K.-D.*; Xu, P. G.; Shiro, Ayumi*; Zhang, S. Y.*; Yukutake, Eitaro*; Shobu, Takahisa; Akita, Koichi*

Advanced Engineering Materials, 9 Pages, 2023/00

https://onlinelibrary.wiley.com/doi/10.1002/adem.202300470

Evaluation of doped potassium concentrations in stacked two-Layer graphene using real-time XPS

Ogawa, Shuichi*; Tsuda, Yasutaka; Sakamoto, Tetsuya*; Okigawa, Yuki*; Masuzawa, Tomoaki*; Yoshigoe, Akitaka; Abukawa, Tadashi*; Yamada, Takatoshi*

Applied Surface Science, 605, p.154748_1 - 154748_6, 2022/12

https://doi.org/10.1016/j.apsusc.2022.154748

Immersion of graphene in KOH solution improves its mobility on SiO/Si wafers. This is thought to be due to electron doping by modification with K atoms, but the K atom concentration C in the graphene has not been clarified yet. In this study, the C was determined by XPS analysis using high-brilliance synchrotron radiation. The time evolution of C was determined by real-time observation, and the C before irradiation of synchrotron radiation was estimated to be 0.94%. The C 1s spectrum shifted to the low binding energy side with the desorption of K atoms. This indicates that the electron doping concentration into graphene is decreasing, and it is experimentally confirmed that K atoms inject electrons into graphene.

Nanoscale structural analysis of ferroelectrics using pair distribution function

Yoneda, Yasuhiro

Oyo Butsuri, 91(12), p.729 - 735, 2022/12

https://doi.org/10.11470/oubutsu.91.12_729

It is important to determine whether a sample is a single phase or not in order to improve the quality of ferroelectrics. Therefore, we have succeeded in developing a detection method for trace amounts of segregated phases by using two-body correlation distribution function (PDF) in addition to X-ray diffraction, which has been conventionally used to detect impurities. In the X-ray diffraction pattern of the BaTiO-BiFeO solid solution, it appears as a single phase with a rhombohedral structure. However, when the PDF was calculated from the obtained diffraction pattern, it was found that not only the component derived from the rhombohedral crystal structure calculated from the average structure but also the BaTiO component was mixed and segregated. By using PDF in this way, it has become possible to detect fine segregation phases on the order of nanoscale.

A Study on stress measurement of weld part using double exposure method

Suzuki, Kenji*; Kura, Komoe*; Miura, Yasufumi*; Shiro, Ayumi*; Toyokawa, Hidenori*; Saji, Choji*; Kajiwara, Kentaro*; Shobu, Takahisa

Zairyo, 71(12), p.1005 - 1012, 2022/12

https://doi.org/10.2472/jsms.71.1005

This paper describes a stress measurement from a welded part of an austenitic stainless steel using synchrotron X-rays. Difficulty measuring the X-ray stress of the welded part is caused by the broadening of the diffraction spot in the radial and circumferential directions. The bending strains of the rectangular bar made of the welded part were measured using synchrotron white X-rays and the double exposure method. To improve the energy resolution, monochromatic synchrotron X-ray of 70 keV was used. The diffraction pattern showed the sharp arc like a pattern from texture material. The diffraction profile was obtained from the integral of the diffraction intensity in the direction of the circumference. The diffraction angle was determined using the double exposure method. As a result, the distribution of the residual stresses of the welded part could be measured.

Structural change by phosphorus addition to borosilicate glass containing simulated waste components

Okamoto, Yoshihiro; Shiwaku, Hideaki; Shimamura, Keisuke*; Kobayashi, Hidekazu; Nagai, Takayuki; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*

Journal of Nuclear Materials, 570, p.153962_1 - 153962_13, 2022/11

https://doi.org/10.1016/j.jnucmat.2022.153962

Simulated nuclear waste glass samples containing phosphorus, which increase the solubility of molybdenum, were prepared and analyzed using synchrotron X-ray Absorption Fine Structure (XAFS) analysis for some constituent elements and Raman spectroscopic analysis of their complex structure. Changes in local structure and chemical state due to different phosphorus additions and waste loading rates were systematically studied. Consequently, no crystalline phase due to the molybdate compound was observed even at a maximum waste content of 30 wt% (corresponding to 1.87 mol% MoO). Oxidation proceeded when the waste-loading rate was increased, whereas the reduction proceeded when phosphorus was added. In some cases, the effects of oxidation and reduction were offset. The local structure around specific elements can be classified as follows; Zn that is affected mainly by the waste-loading rate, Ce that is affected by both the waste-loading rate and phosphorus addition, and Zr element that is not affected by either of them. From the comparison between the analytical results of Mo and other elements, it was considered that the added phosphorus exists as a free PO structural unit and may deprive the alkali metal coordinated to the molybdate ion.