W.Liang
,
X.X.Ma
,
X.G.Zhao
,
J.Zhang
,
D.X.Zou
金属学报(英文版)
The Ti-48Al alloy was pack siliconized with 15i+85Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by XRD and SEM equipped with XEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spallation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h.
关键词:
TiAl-based alloy
,
null
,
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
赵敏
,
姚子华
,
张荣珍
,
高俊刚
高分子材料科学与工程
用X射线能谱微区分析方法对PVC/PP-g-MA H共混物进行了研究,得到了共混物断面氯元素的面分布图,并对面分布图像进行了相分析,从 亚微观层次揭示了PVC/PP-g-MAH共混物的相结构。通过对元素面分布图的面积计算,研究 了共混组成与相容性的关系,并初步探讨了共混物力学性能与面分布的相关性。
关键词:
X射线能谱
,
微区分析
,
面分布
,
相结构
,
PV C/PP-g-MAH
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