H.M.Lu
金属学报(英文版)
Growth and ordering of coherently strained Ge-rich islands in Ge/Si single layer and multilayer systems and the influence of island arrangements on the evolution of the surface morphology of Si cap layers during deposition by low-pressure chemical vapour deposition(LPCVD) on Si(001) substrates at 700℃ have been investigated by TEM of cross-section and plan-view specimens. At distances between the Ge layers of 35-50nm, vertical order of GeSi islands is observed for Ge-Si bilayer systems and for Ge-Si multilayer systems consisting of 5 layer pairs whereas lateral ordering parallel to <100> substrate directions is observed for the latter case only. In agreement with earlier results the vertical ordering in the multilayer system can be understood as result of the elastic interaction between island nuclei forming in the layers with close islands in a buried layer below. The lateral ordering along <100> may be attributed to the anisotropy of the elastic interaction. Characteristic for all Si surfaces are the spatial correlation between the presence of island-induced lattice strain and the appearance of arrays of larger square-shaped pyramids with distinct faceting and facet edges along <110>. The results reflect the importance of the control of growth parameters and of the island-induced strain state for the evolution of the Si top layer surface morphology during LPCVD growth.
关键词:
Si-Ge heteroepitaxy
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null
,
null
李晓敏
硅酸盐通报
文章研究了晶体Er∶Lu2O3的生长、光谱特性、热传导率和能级跃迁表现.室温下采用971 um的半导体激光器泵浦,获得了1.4W的2.85μm连续激光输出,斜效率为36％.这超越了斯托克斯系数,因为低能级返回高能级粒子循环利用的的上转换过程,产生了目前为止效率最高的3μm激光输出.在激光二极管泵浦下,获得了5.9W的激光输出,斜效率为27％.
关键词:
热交换法
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热传导率
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3μm激光器
那木吉拉图
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阮永丰
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苏小平
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杨海
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杨鹏
,
李楠
人工晶体学报
本文在CF4气氛中以提拉法成功地生长出高质量的掺入Tm3+、Ce3+的LiLuF4和LiYF4晶体,对比了Ar和CF4气氛中生长的LiYF4晶体的红外光谱特性,讨论了CF4气氛对LiM(M=Y,Lu)F4晶体生长的影响.同时测试了Tm3+、Ce3+在LiLuF4和LiYF4晶体中的有效分凝系数,从离子半径和晶胞畸变的角度,讨论了Tm3+、Ce3+在LiLuF4和LiYF4晶体中有效分凝系数差别的产生原因.
关键词:
LiYF4
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LiLuF4
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晶体生长
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有效分凝系数
Solid State Communications
The spin-Hamiltonian (SH) parameters (g factors g parallel to, g perpendicular to and hyperfine structure constants (177)A parallel to, (179)A parallel to, (177)A perpendicular to, (179)A perpendicular to) of 5d(1) ion Hf3+ in zircon-type orthophosphate MPO4 (M = Sc, Lu, Y) crystals are calculated from two microscopic SH theory methods, the perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM). The calculated results show that when the high-order (i.e., the third-order rather than the conventional second-order) perturbation formulas in PTM are used, the calculated values from both PTM and CDM methods are not only close to each other, but also in good agreement with the experimental values. This suggests that the two microscopic SH theory methods based on crystal-field theory are effective to the explanations of SH parameters for 5d(n) ions in crystals. The covalence effect, the signs of constants A(i) (i = parallel to or perpendicular to) and the core polarization constants K obtained from the calculations are also discussed. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
insulators;point defects;crystal and ligand fields;electron;paramagnetic resonance;electron-paramagnetic-res;phosphate single-crystals;epr parameters;cr3+ ions;laser;ruby
Pengfei Zhang Litong Zhang Xiaowei Yin
材料科学技术（英文）
To improve the corrosion resistance of porous Si3N4 used in the high temperature environments, which contain water vapor and volatile species, porous Si3N4-Lu2Si2O7 composite ceramics were fabricated by a process of oxidation bonding and pressureless sintering in flowing N2 atmosphere at the temperatures lower than 1550°C. The pores in ceramics were formed by removing the pore-forming agent (phenolic resin). SiO2 derived by the oxidation of Si3N4 at 1250°C in air reacted with Lu2O3 at various sintering temperatures, leading to the formation of Lu2Si2O7 with excellent oxidation and corrosion resistance. The phase composition, microstructure, and mechanical properties of the porous ceramics depended on the sintering temperatures. Si3N4-Lu2Si2O7 composite ceramics with the porosity of 52% and the pore size of 0.2μm were obtained by oxidation bonding at 1250°C for 1 h and pressureless sintering at 1550°C for 2 h using 4 wt pct Lu2O3 additive.
关键词:
Porous ceramics
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氮化硅
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焦硅酸镥
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无压烧结
Xinbin HU
,
Mei ZHANG
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Xiaochun WU
,
Lin LI
材料科学技术（英文）
Based on the local equilibrium assumption, coarsening behavior of M23C6 carbide at 700℃ in H13 steel was simulated by DICTRA software. The results from the calculations were compared with transmission electron microscopy (TEM) observations. The results show the interfacial energy for M23C6 in H13 steel at 700℃ is thus probably 0.7 J•m-2, which fits the experiments well. The influence of composition and temperature on the coarsening rate was also investigated by simulations. Simulations show a decrease in the coarsening rate when V/Mo ratio is increased, while the coarsening rate increases with increasing temperature.
关键词:
DICTRA Simulation
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碳化物粗化
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界面能
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H13钢
Yong LIU
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Baiyun HUANG
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Kechao ZHOU
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Hongwu OUYANG
,
Yuehui HE
材料科学技术（英文）
In order to overcome the shortcomings of conventional hot pressing, a novel near net-shape technique, called radial hot pressing, for P/M parts with large height-to-diameter (H/D) ratio was introduced. Effects of processing parameters on the microstructures and density of P/M TiAl base alloy valves were studied. Results show that the radial hot pressing is an effective technique for manufacturing valves with a H/D ratio of about 10:1, and the perfect joint interface between the Mo sheet and the parts is helpful for subsequent HIPing.
关键词:
Near net-shape technique
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null
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null
刘红斌
,
龚承元
,
苏建勇
,
朱孟府
,
马军
,
张西正
膜科学与技术
doi:10.3969/j.issn.1007-8924.2002.03.014
介绍了工业规模的EDI膜堆和1 m3/h RO-EDI高纯水设备的研制情况,进行了设备的稳定性试验和EDI产水的水质分析,并与离子交换树脂进行了技术经济性能比较.
关键词:
电去离子
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反渗透
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制药用水
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高纯水
