Influence of AlN buffer layer thickness on structural properties of GaN epilayer grown on Si (111) substrate with AlGaN interlayer

We present the growth of GaN epilayer on Si (111) substrate with a single AlGaN interlayer sandwiched between the GaN epilayer and AlN buffer layer by using the metalorganic chemical vapour deposition. The influence of the AlN buffer layer thickness on structural properties of the GaN epilayer has been investigated by scanning electron microscopy, atomic force microscopy, optical microscopy and high-resolution x-ray diffraction. It is found that an AlN buffer layer with the appropriate thickness plays an important role in increasing compressive strain and improving crystal quality during the growth of AlGaN interlayer, which can introduce a more compressive strain into the subsequent grown GaN layer, and reduce the crack density and threading dislocation density in GaN film.     

Microstructure and strain films using in-plane grazing analysis of GaN epitaxial incidence x-ray diffraction

This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.     

多源异构土地基础数据一体化管理检索方法研究

为了从多源异构的复杂土地基础数据中快速准确地提取用户所需信息,提出了基于元数据的一体化管理检索方法.在元数据信息提取、元数据加权索引、实体同义词扩展检索3个环节中,结合土地领域专业知识和用户实际需求,设计和开发了共享元数据表结构、加权元数据中字段相对重要性和信息熵因子,构建地名实体和专题数据层实体同义词库,并集成到包括中文分词、实体识别、同义词扩展、索引检索和相似度计算的一体化管理检索框架中,解决了多源异构土地基础数据统一管理和精确检索的问题.实践表明,该方法较传统的通用信息检索方法具有更好的适用性和更高的准确率.     

镍系胶体催化丁二烯聚合反应的研究Ⅰ: 催化剂的相态

研究了Ni(naph)~2-Al(i-Bu)~3-(BF~3·OEt~2+n-C~8H~1~7OH)催化体系的相态。通过Tyndall效应、电镜观察和超过滤实验,证明镍催化体系在溶有丁二烯的加氢汽油中以小颗粒分散,粒径在1～100nm之间,为胶体催化剂,属高度分散的多相催化体系。催化剂的活性中心位于胶粒表面,催化剂颗粒是无定形的。催化剂各组分配比影响胶粒形态,其中以较佳配比所得到的催化剂颗粒较小、分布均匀,催化丁二烯聚合反应活性高。     

镍系胶体催化丁二烯聚合反应的研究Ⅱ: 催化剂组分的 电导率和紫外光谱

在加氢汽油介质中Ni(naph)~2-Al(i-Bu)~3-(BF~3·OEt~2+n-C~8H~1~7OH)体系为胶体催化剂的基础上,本文从电导率、UV-Vis光谱对催化剂各组分之间的相互作用作进一步的分析。得出催化剂组分以离子对的形式参与反应;Ni^0在Ni(naph)~2-Al(i-Bu)~3陈化液中以团簇粒子形式存在,因吸附Ni^+naph^-而稳定,因加入BF~3·OEt~2而失去稳定性、聚结为胶粒,活性中心位于胶粒表面的观点。     

投料顺序对动态硫化PP／EPDM性能影响及其机理的研究

针对ＰＰ降解在ＰＰ／ＥＰＤＭ动态硫化中对体系产生的不利影响。考察了四种不同投料顺序对ＰＰ／ＥＰＤＭ动态硫化物的冲击韧性，加工流动性，交联程度和断面形貌等宏观和微观性能，并进行了不同ＥＰＤＭ含量的动态硫化和非硫化ＰＰ／ＥＰＤＭ的性能比较。结果表明，优化投料顺序能实现对动态硫化体系中化学反应对象和化学反应程度的有效干预。     

β-环糊精键合蚀刻开管毛细管电色谱柱的制备与评价

研究环糊精键合蚀刻毛细管柱的制备方法，考察了电渗流性质及其电色谱性能；其电渗流大小和方向都可调控；有效分离了碱性蛋白和硝基苯酚位置异构体；对安息香和氨基酸衍生物对映异构体能部分分离。     

2,4,6-三硝基苯酚改性锆铝复合氧化物固定相分离富勒烯的色谱性能研究

制备了用于分离C60和C70的2，4，6－三硝基苯酚改性锆铝复合氧化物高效液相色谱固定相，考察了流动相中甲苯的含量、柱温及流速对C60和C70分离的影响，同时比较了酸腐蚀前后锆铝复合氧化物基质对分离的影响，结果表明，2，4，6－三硝基苯酚改性酸腐蚀后锆铝复合氧化物填料对富勒烯表现出较强的分离能力，具有作为富勒烯制备分离的潜力。     

飞行时间二次离子质谱(TOF-SIMS)结合化学衍生法分析杂环新化合物的结构

飞行时间二次离子质谱(TOF-SIMS)分析了难挥发的杂环新化合物咪唑啉硫氰酸盐及其三种衍生物,确认出很强的氢离化及银离化准分子离子峰,通过对各种衍生物谱图的对照分析,确认出较强的含有结构特征的碎片离子峰,并对该化合物在离子轰击下的裂解规律作了分析,支持了对该新化合物结构的鉴定.     

四氮大环-金属配合物与DNA作用的电化学及谱学研究

Mononuclear copper（Ⅱ）, nickel（Ⅱ） and cobalt（Ⅲ） tetracoordinate macrocyclic complexes were synthesized and spectroscopically characterized. The crystal structure of the three compounds were determined by X-ray crystallography. The electrochemical experimental results indicate that the three complexes could interact with DNA mainly by electrostatic interaction. The interaction of tetracoordinate macrocyclic cobalt（Ⅲ） complex with DNA was studied by cyclic voltammetry and UV-vis spectroscopy. The experimental results reveal that tetracoordinate macrocyc- lic cobalt（Ⅲ） complex could interact with DNA by electrostatic interaction to form a 1 ： 1 DNA association complex with a binding constant of 7.50 ×10^3 L·mol^-1.