材料期刊网

NUMERICAL SIMULATION METHODS AND THEIR APPLICATION IN MATERIAL HOT-WORKING

J. T. Niu , H. T. Li , X. D. Meng and P. Karjaleinen 1) Analysis and Measurement Center , Harbin Institute of Technology , Harbin 150001 , China 2) Department of Mechanocal Engineering , The University of Oulu , Finland

金属学报(英文版)

With the development of modern science and technology, especially computer science, the numerical simulation method has been widely used in material hot-working. Mary achievements have been made in this field by using the numerical simulation method. The numerical simulation method, especially finite element method fully described in this paper.Applications of the numerical simulation method in material hot-working are also discussed. Finally, the future of the numerical simulation method is outlined.

关键词: numerical simulation , null , null

Comparative analysis of the difference of local structure between EPR theory and X-ray diffraction experiment for NiSiF(6)center dot 6H(2)O crystal

Journal of Alloys and Compounds

The local structure for NiSiF(6)center dot 6H(2)O crystal has been investigated by diagonalizing the complete energy matrices, By simulating the EPR and optical spectra, the local structure parameter theta(0) = 54.8901 is determined at room temperature and is different from theta(0)' = 55.0899 obtained by X-ray diffraction experiment, suggesting that: (i) the H(+) ions lead to a deviation of the equivalent position of effective charge of H(2)O molecule from O(2) ion, (ii) the neighboring [siF(6)](2) octahedral clusters lead to a deflection of the H(2)O molecules towards them. The deviation angle Delta theta(0) = -0.1999 is reported for file first time. Furthermore, the local structure NiSiF(6)center dot 6H(2)O crystal has been determined it 4.2 and 77 K. (c) 2007 Elsevier B.V. All rights reserved.

关键词: Local structure;Complete energy matrices;EPR theory;X-ray diffraction;experiment;NiSiF(6)center dot 6H(2)O crystal;electron-paramagnetic-resonance;nickel fluosilicate;magnetic-resonance;optical absorption;field;pressure;cobalt;fe-3+;zinc;ion

Theoretical investigations of the g factors and the local structure for the trigonal Zr(3+) center in X-ray irradiated YSZ

Journal of Alloys and Compounds

The electron paramagnetic resonance (EPR) g factors g(parallel to) and gperpendicular to and the local structure for the trigonal Zr(3+) center in X-ray irradiated yttria-stabilized zirconia (YSZ) are theoretically investigated from the perturbation formulas of the g factors for a 4d(1) ion in trigonally distorted octahedra. Based on the studies, in this trigonal center (characterized as [ZrO(6)](9-) cluster associated with two oxygen vacancies V(o) along the [ 111] axis), the O(2-) ions in the ligand triangles are found to displace towards the neighbouring Vo by about 0.42 Angstrom due to the electrostatic attraction of the V(o). The above displacement is comparable with that (approximate to 0.36 Angstrom) obtained from neutron diffraction measurements and those (approximate to 0.24-0.37 Angstrom) based on the optical spectral analysis and crystal-field calculations in the previous works. Particularly, partial quenching of the spin-orbit (SO) coupling interaction (i.e., gamma(SO) approximate to 0.44) due to the dynamic Jahn-Teller effect (DJTE) and its influence on the g factors, which were ignored by the previous authors, are taken into account in the present work. The validity of the results is discussed. (C) 2004 Elsevier B.V. All rights reserved.

关键词: electron paramagnetic resonance (EPR);defect structure;crystal-fields;and spin Hamiltonian;Zr(3+);yttria-stabilized zirconia (YSZ);oxide fuel-cells;paramagnetic-resonance spectra;yttria-stabilized;zirconia;spin-orbit interaction;single-crystals;electron traps;ions;epr;fabrication;impurity

Comparison between Double Crystals X-ray Diffraction and Micro-Raman Measurement on Composition Determination of High Ge Content Si1-xGex Layer Epitaxied on Si Substrate

Lei ZHAO

材料科学技术（英文）

It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction (DCXRD) and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.

关键词: Si1-xGex , high , Ge , content , composition , determi

First-principles investigations of the stability and electronic structure of ZrV2Hx (x=0.5, 1, 2, 3, 4, 6 and 7)

Acta Materialia

A calculation of the electronic structure and formation energy for ZrV2Hx (x = 0.5, 1, 2, 3, 4, 6 and 7) is performed using a plane-wave pseudo-potential method. It is found that in ZrV2Hx hydrogen forms stronger covalent bonds with vanadium than with zirconium if Zr atoms are in the neighborhood of V. A detailed analysis of how the densities of states change with the hydrogen count x in ZrV2Hx shows the changes in the bonding and anti-bonding interactions of H with V and Zr. However, the covalent anti-bonding interactions between H and V seem to be mainly responsible for the variation in the formation energy of ZrV2Hx with x. The value of projected density of states of V 3d at the Fermi level can be used as a rough comparative measure for these antibonding interactions and therefore allows us to predict the changes in stability of ZrV2Hx with x. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: electronic structure;formation energy;plane-wave pseudo potential;hydrogen storage alloy;intermetallic compounds;convergence acceleration;population analysis;laves phases;total-energy;transition;hydrides;superconductivity;magnetism

Magnetocaloric effect and size-effect related thermal hysteresis reduction in MnAs(1-x)P(x) compounds

Physica Status Solidi a-Applications and Materials Science

In MnAs(1-x)P(x) compounds (x = 0.006 and 0.01), prepared by mechanical alloying, the thermal hysteresis is greatly reduced from about 10-30K in MnAs-based compounds, prepared by conventional melting, to 2K for x = 0.01 (or 4K for x = 0.006). Such obvious hysteretic reduction is ascribed to the grain-size effect, largely due to the preparation method of mechanical alloying. Meanwhile, a maximum value of the magnetic-entropy change Delta S(M) of 11.3 J/kgK for a field change of 2 T is obtained at 294.5K for MnAs(0.994)P(0.006). The study on the MnAs(1-x)P(x) system and also the effect of the preparation technology may be beneficial for the realization of magnetic refrigerants for application at room temperature. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词: magnetocaloric effect;mechanical alloying;thermal hysteresis;gd-5(si2ge2);transition;mnas

THE SYNTHESIS AND MAGNETOSTRICTION OF P rx Ce 1 x Fe 2 COMPOUNDS

Y.X.Li , G.Z.Xu , J.P.Qu , F.G.Liu and B.W.Wang Hebei University of Technology , Tianjin 300130 , China C.C.Tang.G.H.Wu and W.S.Zhan State Key Laboratory for Magnetism , Institute of Physics , CAS , Beijing 100080 , China C.Zhao Tianjin University , Tianjin 300072 , China S.X.Gao Hebei Normal University , Shijiazhuang 050091 , China

金属学报(英文版)

The synthesis and magnetic properties of Pr xCe 1 x Fe 2 have been investigated. The forma tion of Pr xCe 1 x Fe 2 is found to depend strongly on annealing temperature. Pure single phase compound can be synthesized at ambient pressure when x≤0 5. The main phase of the Laves structure can still be observed up to x=0 8. Magnetostriction increases with in creasing x and a largest saturation magnetostriction 200 ppm is observed for x=0.5.

关键词: magnetostriction , null , null

High-pressure and high-temperature synthesis and characterization of mixed valence perovskite oxides LaTi1-xLixO3

Journal of Alloys and Compounds

Perovskite oxides LaTi1-xLixO3 (x=0.2, 1/3) were synthesized using high-pressure and high-temperature method. This new synthesis route has some advantages. XRD analysis showed that the x = 0.2 sample belongs to cubic perovskite-type structure and the x = 1/3 sample belongs to orthorhombic perovskite-type structure. EPR measurement indicated that Ti ions were in mixed valence of +3 and +4. IR measurement indicated that the vibration frequency and width of BO6 Octahedron stretching vibration absorption band decreases with the increasing of x. Valence of Ti ions can be altered by high-pressure and high-temperature. (c) 2006 Elsevier B.V. All rights reserved.

关键词: high-pressure and high-temperature synthesis;LaTi1-xLixO3;EPR;mixed;valence

X70管线钢J1d和K1a与V型缺口Ak关系研究

朱杰武 , 柳永宁 , 许雁 , 冯耀荣

机械工程材料 doi:10.3969/j.issn.1000-3738.2005.06.007

在不同温度下测试了X70管线钢动态断裂韧度K1d、J1d和止裂韧度K1a以及夏氏V型缺口冲击韧度Ak,对三者的关系进行了分析.结果表明:温度和加载速率都对断裂韧度产生影响;加载速率变化引起的韧-脆断裂转变具有热激活特征,在热激活分析基础上,在应力强度因子速率K=15 MPa·m1/2s-1条件下,得出断裂韧度、止裂韧度和冲击韧度三者的关系:Ak=4.84×106T-2.8K1d(或K1a).可以用小试样Ak数据计算得到K1d和K1a.

关键词: 管线钢 , 断裂韧度 , 止裂韧度 , 韧-脆断裂转变

High-pressure and-temperature synthesis and characterization of mixed valence perovskite oxides LaTi1-xMgxO3

Materials Chemistry and Physics

Perovskite oxides LaTi1-xMgxO3 (x = 0.25, 0.5) were synthesized using high-pressure and-temperature method. LaTi0.75Mg0.25O3 is a new compound. This new synthesis route has some advantages. XRD analysis showed that the x = 0.25 sample belongs to cubic perovskite-type structure and the a = 0.5 sample belongs to orthorhombic perovskite-type structure. EPR measurement indicated that Ti ions were in mixed valence state of +3 and +4. IR measurement indicated that the vibration frequency and width of BO6 octahedron stretching vibration absorption band decreases with the increasing of x. The valence state of Ti ions can be altered by high-pressure and-temperature. (C) 2000 Elsevier Science S.A. All rights reserved.

关键词: high-pressure and-temperature synthesis;LaTi(1-x)MgxO(3) EPR;mixed;valence