Q.S. Liu1
,
2
,
3)
,
L.C. Zhao3)
,
G.X. Dong2) and N.J. Gu1) 1) Heibei University of Technology
,
Tianjin 300130
,
China 2) Tianjin Institute of Technology
,
Tianjin 300191
,
China 3) Harbin University of Technology
,
Harbin 150001
,
China
金属学报(英文版)
Theconstruction changinginthereversetransformation ofthestress induced εMin Fe 17 Mn 10 Cr 5 Si 4 Ni alloy is carefully inspected in transmission electron microscope, and then stress induced εM procedure of reverse transformation is analyzed. The behavior of reverse transformationisdissimilar when the organization of εMis different. The reversetransfor mation ofεM withtheshapeofsingle plateandstripisrelativelyeasy,anditsreversibilityincrystallographiciseasilytocarryout,fortheεM with multilayerstructure,thereversetrans formationtakes placein isolatedlayers, fortheεMthat grows well,thereversetransforma tion isrelatively difficult becauseofthe ductile harmonization between itsinternalorganiza tion structures.
关键词:
stress induced εM
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null
,
null
刘叔仪
金属学报
<正> 作为固体脆性断裂判据的J积分,其数值与其积分路径无关,这在文献中叫“守恒性”。这个守恒性已被推广到塑性断裂,这到底有否根据?本文目的是作这个问题的证明。未用原作者的方法,但由两个旋度判据得到应力应变函数行列式给出的一些否定结论,希望这对J积分应用条件的了解有所助益。1.弹塑性J积分守恒的条件 J积分
关键词:
International Journal of Modern Physics B
The EPR g factors g(//) and g(perpendicular to) for the six-coordinated Cu2+(1) site in YBa2Cu3O6+x are theoretically investigated from the perturbation formulas for a 3d(9) ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu2+(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu2+ cluster. Based on the calculations, the effective elongation (= 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Delta g (=g(//) - g(perpendicular to)). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.
关键词:
crystal fields and spin hamiltonians;electron paramagnetic resonance;Cu2+;YBa2Cu3O6+x;single-crystals;yba2cu3o7-delta;evolution;esr
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
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断裂韧度
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止裂韧度
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韧-脆断裂转变
Journal of Superconductivity and Novel Magnetism
The zero-field splittings (D and E) and the g factor of Gd(x)Eu(1-x)Ba(2)Cu(3)O(7-delta) are theoretically investigated from the superposition model formulas or the zero-field splittings and the approximation formula of the g factor containing the admixtures of the ground (8)S(7/2) and the excited (6)L(7/2) (L = P, D, F, G) states, respectively. Based on the studies, the impurity-ligand bond angles related to the crystalline c axis in the impurity Gd(3+) center are about 1.1 degrees smaller than those in the host Eu(3+) site of EuBa(2)Cu(3)O(7-delta). The calculated D, E, g factor and the effective magnetic moment mu(eff) show reasonable agreement with the experimental data. Particularly, the improvement for the theoretical D is achieved in the present work by considering the above angular distortion.
关键词:
Crystal fields and spin Hamiltonians;EPR;Superposition model;Gd(x)Eu(1-x)Ba(2)Cu(3)O(7-delta);spin-hamiltonian parameters;gd3;superconductor;euba2cu3oy
Condensed Matter Physics
The electron paramagnetic resonance (EPR) g factors g(x), g(y) and g(z) of the orthorhombic Cu2+ (1) site in fresh PrBa2Cu3O6+x powders are theoretically investigated using the perturbation formulas of the g factors for a 3d(9) ion under orthorhombically elongated octahedra. The local orthorhombic distortion around the Cu2+ (1) site due to the Jahn-Teller effect is described by the orthorhombic field parameters from the superposition model. The [CuO6](10-) complex is found to experience an axial elongation of about 0.04 angstrom along c axis and the relative bond length variation of about 0.09 angstrom along a and b axes of the Jahn-Teller nature. The theoretical results of the g factors based on the above local structure are in reasonable agreement with the experimental data.
关键词:
crystal fields and Hamiltonians;electron paramagnetic resonance;Cu2+;PrBa2Cu3O6+x;epr;ions;crystal;spectra
Journal of Materials Science
Mn(3+x) Ga(1-x) N compounds with x = 0.0 and 0.1 were prepared by re-sintering Mn(2)N(0.86), Ga bulk and Mn powders. These compounds are deduced to be the N-deficiency ones. In Mn(3)GaN, a step-like magnetic transition, from frustrated antiferromagnetism to paramagnetism with increasing temperature, occurs at 370 K, while the same magnetic transition of Mn(3.1)Ga(0.9)N is far above 380 K. The enhanced magnetization of Mn(3)GaN at low temperatures is ascribed to the fast lowering of antiferromagnetism. The electrical resistivity of Mn(3)GaN exhibits a typically metallic conducting behavior with a positive magnetoresistance of 4-7%.
关键词:
perovskites;heat;manganese;mn3znn;phase
Journal of Alloys and Compounds
Polycrystalline Nd(Mn(1-x)Fe(x))(2)Ge(2) (0 <= x <= 1) compounds have been prepared by arc-melting. X-ray powder diffraction analysis shows that all samples crystallize in the ThCr(2)Si(2)-type structure with the space group 14/mmm. The substitution of Fe for Mn results in decreases of the lattice constants a, c and the unit-cell volume V. Magnetic properties and magnetocaloric effect of the compounds Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) have been studied by magnetic measurements. A spin reorientation transition at about 188 K is observed for Nd(Mn(0.9)Fe(0.1))(2)Ge(2). The Nd(Mn(0.8)Fe(0.2))(2)Ge(2) compound shows more complicated magnetic behavior, which is characterized by four magnetic ordering states below room temperature. The maximum values of the magnetic entropy change are 2.35 and 1.84 J kg(-1) K(-1) for x = 0.1 and 0.2, respectively, under the applied field changing from 0 to 5T. The relative cooling powers of Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) are 145.9 and 133.8 J kg(-1) under an applied field change of 5T. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Metals and alloys;Magnetocaloric;X-ray diffraction;room-temperature applications;neutron-diffraction;phase-transitions;crystal-structure;solid-solution;refrigeration;silicides;mn;0-less-than-or-equal-to-x-less-than-or-equal-to-1;mnas1-xsbx
