M. Zhao
,
G. Zhang
,
K.S. Zhang
金属学报(英文版)
By combining the Bodner-Partom constitutive model and equivalent stress function,finite element methods and program on analyzing non-elastic deformation and stressfor thermal viscoplastic material are studied in this paper, and it's the first timethat this material model is used in a kind of engineering software-MARC. Thermalviscoplastic behavior of high temperature alloy GH536 specimen with gap is analyzedby this program. The research results show it is feasible to analyze thermal viscoplasticbehavior of specimen or structure by applying B-P model.
关键词:
effective stress function(ESF)
,
null
International Journal of Modern Physics B
The perturbation formulae of EPR parameters g factors g(x), g(y) and g(z) for the lowest Kramers doublet of 4f(1) ion in orthorhombic symmetry are established. In these formulae, the contributions of the covalency effects, the admixture between J = 7/2 and J = 5/2 states as well as the second-order perturbation (which is not considered in the previous works) via crystal-field and orbital angular momentum interactions are all included. According to these formulae, and by using the superposition model, the g-factors g., g(y) and g(z) for Ce3+ center in YBa2CU3O6+x superconductor are calculated. The results are discussed.
关键词:
YBa2Cu3O6+x;EPR;superposition model;Ce3+;crystal-field
Optical Materials
The perturbation formulas of the EPR g factors g,, g and g. for a 4f(11) 1 ion in orthorhombic symmetry are established. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various states are taken into account. The above formulas are applied to the orthorhombic Er3+ centers in YAG, YGG and LuGG garnets. By analyzing their g factors, we find that the polar angles theta(j)(') of the impurity-ligand bonds related to the Z axis of the crystals in these Er3+ centers are smaller than the host angles theta(j) in pure crystals, whereas the azimuthal angles, related to the X axis in the impurity centers are larger than the corresponding phi(j) in the hosts. The g factors and their anisotropies Delta g [= g(z) - (g(x) + g(y))/2] and delta g (= g(x) - g(y)) for Er3+ in the garnets based on the above local structural parameters are in good agreement with the observed values. In addition, the angular distortions Delta theta (= theta(j)(') - theta(j)) or Delta phi (= phi(j)(') - phi(j)) obtained by analyzing the EPR data in this work are different from Delta theta(2), or Delta phi(2) (for only the second set of ligands, i.e., j = 2) based on the superposition model crystal-field analysis in the previous 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-field;and spin hamiltonians;Er3+;garnets
Spectroscopy and Spectral Analysis
The complete high-order perturbation formula of g factor for 3d(3) ions in cubic octahedral site was derived. In the formula, both the contribution Delta g(CF) to g-shift Delta g(=g-g(s), where g(s) =2. 002 3) due to crystal-field (CF) mechanism (related to the interactions of CF excited states with the ground state) and that (Delta g(CT)) due to charge-transfer (CT) mechanism (related to the interactions of CT excited states with the ground state, which is omitted in crystal-field theory) are included. By using the formula and the parameters obtained from the optical spectra of CaZrO(3) : Mn(4+) crystal, the g factor of CaZrO(3) : Mn(4+) was calculated. The result is consistent with the experimental value. The calculations show that the contribution is opposite in sign and about 62% in magnitude compared with the contribution Delta g(CF). It appears that both CF and CT mechanisms should be considered in the calculation of g factor for the high valence 3d(3) (e. g., Mn(4+) and Fe(3+)) ions in crystals.
关键词:
electron paramagnetic resonance;g factor;charge transfer mechanism;crystal and ligand field theory;CaZrO(3);Mn(4+);atomic screening constants;scf functions;luminescence;manganese
Physica B-Condensed Matter
In this paper, by using only one adjustable parameter V' (the trigonal-field parameter), the zero-held splitting D, the g factors g(parallel to) and Delta g (= g(parallel to) -g(perpendicular to)) for CsMgCl3:V2+ crystal have been calculated from the high-order perturbation formulas based on the two spin-orbit coupling parameter model. The calculated results show good agreement with the observed values. A comparison between the calculated results from various crystal field theories are also made. It is found that the difference between signs D and Delta g for CsMgCl3:V2+ crystal is caused by the contributions from the excited multiplets, particularly those arising from the free ionic term (2)G. (C) 1998 Elsevier Science B.V. All rights reserved.
关键词:
crystal and ligand field theory;electron paramagnetic resonance;spin-orbit coupling;V2+ ion;CsMgCl3;crystal;spectra;ions
吴国杰
,
董奋强
,
崔英德
,
李妮妮
,
何春林
材料导报
研究了鱼蛋白(FP)接枝聚合丙烯酸(AA)和丙烯酰胺(AM)制备蛋白改性高吸水性树脂的方法.通过对产品吸(盐)水性能的测试,得到合成产品的合适条件为:鱼蛋白、引发剂和交联剂相对单体的量分别约为7.5%、1.0%和0.025%,丙烯酸与丙烯酰胺的质量比为9:1,丙烯酸中和度为90%,单体质量分数为18%.在此条件下制备的高吸水性树脂,其吸水倍率达1061g/g,吸盐水倍率达136g/g.并用红外光谱对产物进行了表征.
关键词:
鱼蛋白
,
丙烯酸
,
丙烯酰胺
,
接枝
,
高吸水性树脂
Physica B-Condensed Matter
The perturbation formula of g factor for 3d(7) ion in cubic octahedral crystals has been obtained from a cluster approach. In the formula, the parameters related to the configuration interaction and the covalency reduction effect can be obtained from the optical spectra of the crystal under study and so no adjustable parameters are applied. From the formula, the g factors for Co2+ in fluoroperovskites LiBaF3, KMBF3, KZnF3 and CsCdF3 are calculated. The calculated results are in agreement with the observed values. The g factor following the order of LiBaF3 : Co2+ < KMgF3 : Co2+ < KZnF3: Co2+ < CsCdF3 : Co2+ is also explained. (C) 2000 Elsevier Science B.V. All rights reserved.
关键词:
electron paramagnetic resonance;crystal- and ligand-field theory;Co2+;LiBaF3;KMgF3;KZnF3;CsCdF3;perovskite;transition;impurities;crystals
