稀土化合物催化内酯开环聚合(Ⅲ)──氯化钕-环氧化合物体系催化ε

Bulk polymerization of ε-caprolactone(CL) with neodymium chloride-epoxide sys tem has been studied. It was found that the addition of epoxide can greatly increase the catalytic activity of neodymium chloride. The catalytic activity sequence of NdCl₃ combined with epoxide is: NdCl₃-ethylene oxide > NdCl₃-proplene oxide > NdCl₃-epichlorohydrin≈NdCl₃-allyl glycidyl ether. The catalytic activity of NdCl₃-proplene oxide system increases,but molecular weight of resulting polycaprolactone(PCL) decreases at higher proplene oxide/ neodymium chloride molar ratio.The molecular weight of PCL can be controlled by catalyst concentration. Higher polymerization temperature can greatly increase the catalytic efficien cy. At 30℃, PCLwith molecular weight as high as 28. 9×10⁴can be prepared easily with an activity of 44×10⁴g PCLper molar neodymium, and at 60℃, the molecular weight of PCLand catalytic efficiency increased to 42×10⁴and 10⁶g PCL/mole Nd respectively.     

低位错密度4 inch GaSb(100)单晶生长及高质量衬底制备

采用液封直拉法(LEC)生长了4 inch直径(100)GaSb单晶并进行了衬底晶片的加工制备.通过优化热场,可重复生长出非掺和掺Te 整锭(100)单晶,单晶锭的重量为5~8 kg, 成晶率可达80;以上.4 inch(100)晶片大部分区域的位错腐蚀坑密度小500 cm-2,其(004)双晶衍射峰的半峰宽为29弧秒,表明晶片衬底的完整性相当好.晶体生长过程中固液界面较为平坦,因而晶片表现出良好的横向电学均匀性.经研磨和机械化学抛光,制备出具备良好平整度和表面粗糙度的开盒即用衬底晶片.通过控制本征受主缺陷浓度和掺杂浓度,制备出具有良好近红外透光率的n型GaSb单晶衬底.     

固定化肌红蛋白的类酶活性电化学研究

肌红蛋白(Mb)位于肌肉的肌细胞中,其功能是可逆地结合氧气,将氧气贮存于肌肉细胞中。从结构上来看,Mb以血红素作为必须的活性中心,与一些以血红素为辅基的酶(如辣根过氧物酶、细胞色素P450等)的结构相似,含有一个供底物结合的空缺配位点。因此Mb常作为研究酶的结构与功能关系的     

SrCl2 as an efficient cocatalyst for acidic hydrolysis of methyl glycosides

SrCl2 was found to be the most efficient cocatalyst for the acidic hydrolysis of methyl glycosides after 26 kinds of most representative metal salts were screened. The SrCl2-cocatalyzed acidic hydrolysis of methyl glycosides is highlighted by short reaction times, less byproducts and high yields. A possible mechanism for the SrCl2-cocatalyzed hydrolysis is also proposed.     

Effective Field Based on the Exchange Interaction in Gd3Ga5O12 under Low and Moderate Magnetic Field at Low Temperature

The roles of the exchange interaction between different magnetic ions in the gadolinium gallium garnet Gd3 Ga5O12 are systematically investigated. The effective field based on the exchange interaction is expressed as functions of the temperature T and applied field He. Furthermore, the effects of T and He on the magnetic moment and the entropy of GdsGa5O12 are studied in the ranges of 0 〈 He 〈 9 T and 3 〈 T 〈 40K. The computational results are consistent with the experimental data. Our study reveals that the applied field and temperature have important influences on the exchange interaction of Gd3 Ga5 O12 at low temperature.     

GaN单晶薄膜的湿法化学刻蚀研究

ＭＯＣＶＤ用高压汞灯对ｎ－ＧａＮ处延层进行了辐照湿法化学刻蚀研究，这种外延怪是在Ａｌ２Ｏ３衬底上用ＭＯＣＶＤ方法生长的。结果表明：在紫外光照下，ｎ－ＧａＮ层在２５％的ＫＯＨ水溶液中腐蚀较有效。这种腐蚀很可能是通过紫外光增强氧化和还原反应而产生的。     

基于GaAs-AlGaAs非对称耦合量子阱材料的半导体弱光开关

提出了一种基于在GaAs-AlGaAs非对称耦合量子阱材料子带跃迁的量子干涉的半导体弱光开关，分析了驰豫速率γ21对光开关的影响，这种半导体弱光开关是半导体超晶格材料共振隧穿作用导致的子带跃迁的Fano干涉的结果，由于半导体结构与材料可以人为地选择，相干强度可以控制和改变，这种半导体弱光开关比采用原子系统更实用，这也是一种在半导体材料中实现一束光控制另一束光的方法。     

旋光晶体在偏光干涉实验中电光效应的研究

研究了旋光晶体在偏光干涉实验中的电光效应，给出了旋光晶体在偏光干涉实验中出射光强与晶体旋光性之间关系的表达式I—Ao^2cos^2[β-（π/λ）（n1-nr)l]，以及与旋光晶体电光效应之间关系的表达式I—Ao^2cos^2[β-（π/λ）（n1-nr)l (π/λ）（n2-n1)l]。根据这些表达式给出的关系，将典型的旋光晶体La3Ga5SiO14制作成了电光Q开关，像那些用无旋光性晶体制作的Q开关一样工作良好。在中等功率输出的激光器中，La3Ga5SiO14晶体电光Q开关有可能取代氘化磷酸二氢钾(DKDP)晶体电光Q开关。