An Experimental Derivation of Partial Structure Functions of Amorphous Pd_<80>Si_<20> Alloy Using Combination of X-ray, Electron and Neutron Diffraction Experiments

Three partial interference functions corresponding to Pd-Pd, Pd-Si and Si-Si correlations have been separated using the combination of three total interference functions observed by neutron, X-ray and electron diffraction experiments respectively. The number-concentration correlation functions were calculated from the partial Pd-Pd, Pd-Si and Si-Si correlation functions

A Geometrical Relaxation Model on Structure Change and Kinetics during Low-Temperature Annealing of Amorphous Metals

The atomic scale structure relaxation in melt-quenched amorphous metals has been simulated in a computer using a geometrical relaxation model of the dense random packing of hard spheres. The atomic arrangement and kinetics during the geometrical relaxation has been compared with the experimental behaviors on the low-temperature annealing of amorphous alloys

Observation of Nitrogen Induced Amorphization of the V-Cu System by EXAFS, X-ray and Neutron Diffractions

Mechanical alloying (MA) of V_Cu_ powders which is characterized by a positive heat of mixing was carried out under the N_2 gas atmosphere. The structure factor S^X(Q) observed by X-ray diffraction gradually changes into a structure characteristic of an amorphous state with increasing milling time. This indicates the amorphization induced by nitrogen. The S^N(Q) by neutron diffraction after 200 hours of milling also confirmed the formation of an amorphous phase with the residual pure Cu. Since the coherent scattering length of the V atom in the neutron diffraction is negligibly small, crystalline peaks can be easily identified as the fcc Cu. A drastic change of the EXAFS profile around a V atom was more clearly observed than that around a Cu atom. These results allow us to conclude that the bcc solid solution is formed at the early stage of milling and then that the amorphization gradually proceeds in the subsequent stage of milling by incorporating N atoms into the bcc solid solution

Short-Range Structures of Amorphous and Liquid Iron and Pd_<0.8>-Si_<0.2> Alloy

A comparison has been made on the short-range structures of iron and Pd_-Si_ alloy between the amorphous and the liquid states. It is suggested that the short-range structure of amorphous Fe film has higher degree of ordering in comparison to liquid Fe. The atomic configuration in the nearest neighbour in amorphous Pd_-Si_ alloy is close to that in Pd_3Si crystal and is not completely reproduced by the Percus-Yevick Hard Sphere model with high packing fraction corresponding to instantaneous freezing of the liquid structure

Electronic Structures of Amorphous Co-P and Ni-P Alloys by γ-ray Compton Scattering

γ-ray Compton scattering has been applied to study the electronic state of electro-deposited and melt-quenched amorphous Ni_P_ alloys, and electro-deposited amorphous Co_P_ alloy. Based on experimental Compton profiles, it is conclused that the charge transfer occurs from phosphorus atom to 3d band holes of transition metals, but 3d states may not be completely filled with electrons even in amorphous Ni_P_ alloy

コウシュウハ イオンプレーティング ホウ ニ ヨル ハクマク ケイセイ ニ カンスル ケンキュウ

The nanostructural hydrogenated graphite (CnanoHx) was synthesized from graphite by ball milling under hydrogen (H2) atmosphere. In this product, characteristic hydrogenated states in the form of polarized hydrocarbon groups (―CH, ―CH2, and ―CH3) are realized in the nanoscale. By synthesizing the composite of CnanoHx and lithium hydride (LiH), known as the Li―C―H system, hydrogen was desorbed at 350 °C, which is a lower temperature compared to the decomposition temperature of each component. It is considered that this hydrogen desorption would be induced by destabilization of each hydrogen absorbed state due to an interaction between the polarized C―H groups in CnanoHx and LiH. Therefore, in order to understand the hydrogen absorption/desorption mechanism of the Li―C―H system, it is an important issue to investigate the change in the C―H groups during hydrogen absorption/desorption reactions in the composite. The correlations among atoms contained in this composite are examined by neutron diffraction measurements, where the protium/deuterium (H/D) isotopic substitution was used to clarify the location of hydrogen atoms in this composite. Some C―D and Li―D correlations are found from the radial distribution function [RDF(r)] obtained by the neutron diffraction for the CnanoDx and LiD composite. After dehydrogenation, C―C triple bond and Li―C bond, ascribed to lithium carbide (Li2C2), are observed. Furthermore, the RDF(r) corresponding to rehydrogenated composite indicates the presence of not only the Li―D correlation but also the C―D one

外国産胡麻の成分に関する研究(自然科学)

現在わが国では胡麻はほとんど輸入に依存しており,その量は年間約8万トンに達する。わが国への胡麻の輸出国は20ヶ国にもおよび,その量は年により変遷がある。本報告では,スリランカ産,ガテマラ産,タイ産,中国産,メキシコ産,スーダン産,エルサルバドル産,コロンビア産の輸入胡麻について,それらの一般成分,蛋白質のアミノ酸組成について検討した。一般成分分析では,粗灰分は4.02～6.18%で,タイ産黒胡麻が比較的多いほかは,他は余り差が認められなかった。粗脂肪含量は43.97～55.38%で,9試料中6試料は50%以上,多いものでは55%をこえるものもあった。粗蛋白質含量は16.13～23.13%で,胡麻種子の脱脂・脱水物に換算すると,含量は34.28～51.65%で,脱脂粕は高蛋白質含有資源であることが分った。粗繊維の含量は4.19～11.84%で,試料によってかなりの差があり黒胡麻に多い傾向があった。蛋白質のアミノ酸組成では,全般的にグルタミン酸,アルギニン,アスパラギン酸が多いことが分り,味覚の点での期待が考えられる。必須アミノ酸では,アルギニン,ロイシン,バリンなどの含量が比較的多かった。またそのアミノ酸組成からして,胡麻油しぼり粕中の蛋白質は高い栄養価をもつことが示唆された。本研究を行なうにあたり種種御支援をいただいた,四日市市九鬼産業株式会社に御礼を申し上げる

Spin polarization in the phase diagram of a Li–Fe–S system

「イオン摂動」による電池材料硫化鉄リチウムの状態変化を解明 --新規相・物性の開拓と革新的高容量蓄電池の開発に向けて--. 京都大学プレスリリース. 2020-01-06.Divalent and trivalent states of Fe ions are known to be stable in inorganic compounds. We focus a novel LixFeS5 cathode, in which the Li content (x) changes from 2 to 10 by an electrochemical technique. As x increases from 2, a Pauli paramagnetic conductive Li2FeS5 phase changes into a superparamagnetic insulating Li10FeS5 phase. Density functional theory calculations suggest that Fe+ ions in a high-x phase are responsible for ferromagnetic spin polarization. Reaching the monovalent Fe ion is significant for understanding microscopic chemistry behind operation as Li-ion batteries and the original physical properties resulting from the unique local structure

Abnormal Behavior of Hydrogen Response and Hydrogen Induced Linear Expansion Coefficient of Pd-Cu-Si Metallic Glassy Alloys for Thin Film Hydrogen Sensor

Thin films of Pd-Cu-Si metallic glassy alloys of varying composition were prepared by simultaneous three sources (Pd, Cu and Si) sputtering method using a rotating mechanism of substrates. Their H2 responses were observed by measuring the electric resistance changes of them exposed in N2 and H2. In addition, their linear expansion coefficients (LECs) induced by absorbed hydrogen were also measured. Contrary to a normal H2 response transient with a rapid increase in electric resistance of a thin film, several thin films indicated abnormal H2 response transients consisting of complex changes, an increase and a decrease, in electric resistance when the thin films were exposed in H2. These thin films have higher Pd/Si atomic ratios than those indicated normal H2 response transients. Additionally, by the characterization of the thin films, the existence of Pd-nanocrystals of about 2 nm in diameter was observed in the amorphous matrix which possibly includes Pd-clusters as well as Pd atoms. The mechanism of the abnormal H2 response transient can be explained by two conflicting behaviors in electric resistance of the thin films when they are exposed in H2: a decrease by the formation of electrical contacts of Pd-nanocrystals connected with volume expanded Pd-clusters by hydrogen absorption and a following increase by hydrogenation of Pd-nanocrystals. Observed time lags between two conflicting behaviors can be explained by the different transfer speeds of hydrogen relating to two kinds of pathways: inside of Pd-nanocrystals and the amorphous matrix along which hydrogen atoms transfer in the structure. The Pd-nanocrystals also affected on LEC and the H2 response significantly. The thin films with them indicated much higher LEC than the thin films without them. However, the thin films with them did not indicate the high H2 response expected from their high LEC. The result of LEC suggests that Pd-nanocrystals can absorb much more hydrogen atoms than Pd in an amorphous matrix. The Pd in an amorphous matrix is supposed to be Pd-clusters, randomly distributed Pd atoms and Pd atoms forming a trigonal prism that is a structural unit of the Pd-Cu-Si alloys. On the other hand, the high H2 response according to the high amount of absorbed hydrogen can not be expected in the thin films with Pd-nanocrystals, due to a decrease in electric resistance by forming electrical contacts of the Pd-nanocrystals

Radial Distribution Functions of Pd-Si Alloy Glasses by Pulsed Neutron Total Scattering Measurements and Geometrical Structure Relaxation Simulations

The high resolution radial distribution functions of Pd-Si alloy glasses are obtained as a function of Si content by measuring the structure factor up to a very high scattering vector value, that is to say, Q=30-50 A^ with the pulsed neutron total scattering technique using an electron LINAC neutron source. The experimental results are discussed with the computer simulation in terms of a geometrical structure relaxation model of the dense random packing of binary hard spheres