麻彦龙
,
Xiao-rong ZHOU
,
孟晓敏
,
黄伟九
,
廖益
,
陈小丽
,
易雅楠
,
Xin-xin ZHANG
,
G. E. THOMPSON
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(16)64252-8
为了突出特定显微组织组成对 AA2099铝锂合金严重局部腐蚀的影响，对比研究了固溶、预冷变形及人工时效状态下 AA2099合金的腐蚀行为。通过浸泡和动电位极化在合金表面引入局部腐蚀；采用扫描电子显微镜和透射电子显微镜表征合金的显微组织和腐蚀形貌。研究表明：该合金的严重局部腐蚀敏感性与其热机械加工过程密切相关，且合金元素的存在方式影响腐蚀的扩展机理。T8状态合金的严重局部腐蚀敏感性比其他状态合金更高；当进行动电位极化时，固溶和 T3状态合金表现为晶体学腐蚀特征而 T6和 T8状态合金表现为局部区域晶粒和晶界的择优腐蚀。
关键词:
铝锂合金
,
腐蚀
,
点蚀
,
极化
,
热处理
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
Communications in Theoretical Physics
By using the wavefunctions obtained from diagonalizing the complete d(3) energy matrix at normal and various pressures, the g factor of the ground state of SrTiO3:Cr3+ and its pressure-induced shift have been microscopically calculated. Only by taking the local strains around Cr3+ in SrTiO3:Cr3+ (which are about twice the bulk ones) and corresponding P-chi dependence, can we obtain a good agreement between the calculated result of pressure-induced shift of ground-state g factor and the experimental one. The physical origins of this pressure-induced shift have been explained. It is found that the change of Dq(-1) with pressure makes main contribution to the pressure-induced shift of ground-state g factor of SrTiO3:Cr3+. By using the wavefunctions obtained from diagonalizing the complete d3 energy matrix at normal pressure, the relevant matrix elements and accordingly strain-induced splittings of t(2)(3) E-2 and t(2)(3) (4)A(2) of SrTiO3:Cr3+ have been calculated. The important results of Y-c, Z(c), P-c and Q(c) have also been evaluated. It is the admixtures of basic wavefunctions resulted from the spin-orbit interaction and/or Coulomb interaction and/or Kramers degeneracy that make the strain-induced splittings of the levels nonzero. It is found that there are nonvanishing matrix elements of operators T2 xi, T2 eta and T2 zeta between wavefunctions with positive M-s and those with negative M-s', which have important effects on the strain-induced splittings of the levels.
关键词:
crystal fields;energy spectrum;g factors;high-pressure effect;strain-induced splitting;theoretical calculations;ruby;crystal
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
Physical Review A
We study the quantum critical behavior of the XY spin chain with multisite interaction by means of a fidelity susceptibility (FS) calculation. The key ingredients (e. g., finite-size scaling behavior, universality principle) of the quantum criticality near the critical point are investigated carefully. The results show that the FS calculation is reliable to characterize the quantum critical behavior and that the multisite interaction can induce the redistribution of the criticality region.
关键词:
entanglement;model
黎学明
,
龙海平
,
杨建春
,
高放
,
杨文静
,
孔令峰
材料导报
以香草醛为原料,在乙醇介质中与1,3-二溴丙烷反应生成1,3-二(4-甲酰-2-甲氧基苯氧基)丙烷,然后在甲醇介质中进行硼氢化还原,最后在甲酸介质中聚合,合成笼形超分子主体化合物Cryptophane E.采用核磁共振谱(1H NMR、13C NMR)、质谱(MS)、紫外光谱(UV)荧光光谱、红外光谱、元素分析等测试技术对Cryptophane E进行表征,重点考察反应温度、时间及原料配比等因素对合成产率的影响,获得最佳反应条件,并深入探讨了合成机理.
关键词:
Cryptophane
,
E
,
超分子材料
,
合成
,
表征
