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31.
32.
血清钙、镁和微量元素与冠心病 总被引:3,自引:1,他引:3
综述了钙、镁和微量元素在动脉粥样硬化、冠心病(包括冠状动脉痉挛)研究的相关报道,以进一步研究钙、镁和微量元素与冠状动脉痉挛的关系。 相似文献
33.
The rate of the Wolff-Kishner reaction of benzophenone hydrazone in butyl carbitol increases as the cation of the alkoxide base is varied in the order K>Na>Li>Mg. The replacement of butyl carbitol by 1-decanol also accelerates the reaction, and an additional increase is caused by the presence of crown ether. On the basis of changes in the activation parameters, it is concluded that the reactivity of the hydrazone anion increases as the contact ion pair becomes more fully solvated and dissociated. 相似文献
34.
M. Benatsou B. Capoen M. Bouazaoui W. Tchana J.P. Vilcot 《Journal of Sol-Gel Science and Technology》1998,13(1-3):529-533
Er3+ doped-aluminosilicate thin films were prepared on silica and silica/Si substrates by the sol-gel process and dip-coating. The sol-gel aluminosilicate planar waveguides were prepared from silicon and aluminium alkoxides. Their structural characterization has been carried out by Raman spectroscopy, Atomic Force and Scanning Electron Microscopies. The results indicated that these films present an amorphous structure until an annealing temperature of 900°C, while at temperatures higher than 1000°C, crystallization occurs. An estimate of microcrystallite sizes using Raman spectroscopy is given, which agrees with data from scanning electron microscopy. The optical properties have been investigated by Fluorescence spectroscopy in the visible region. 相似文献
35.
手性液晶掺杂剂(S)┐4┐辛氧基┐4┐(2┐酰氧基┐丙氧基)联苯的合成马汝建李培荣国斌*(华东理工大学化学系上海200237)关键词铁电液晶材料,手性液晶掺杂剂,合成,手征性1997-02-03收稿,1997-08-07修回铁电液晶显示器所用的材料... 相似文献
36.
以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高. 相似文献
37.
38.
Shinichi Kikkawa Kazuteru Nagasaka Mark Bailey Yoshinari Miyamoto 《Journal of solid state chemistry》2007,180(7):1984-1989
Gallium oxynitride, isostructural to hexagonal gallium nitride (h-GaN), was obtained by ammonia nitridation of a precursor prepared from the addition of citric acid to an aqueous solution of gallium nitrate. Gallium oxynitride produced at 750 °C had a small amount of gallium vacancies, and was formulated as (Ga0.89□0.11) (N0.66O0.34) where the symbol □ stands for gallium vacancy. Both the gallium vacancies and oxygen substituted for nitrogen were randomly distributed within the structure. The amount of vacancies decreased with nitridation temperatures in the range of 750-850 °C. Approximately, 10 at% Li+ was doped into the gallium oxynitride, using a similar preparation with the additional presence of lithium nitrate, resulted in the random substitution of Ga3+ in an atomic ratio of Li/Ga<1 at 750 °C. Oxygen was codoped with lithium and substituted nitrogen in the wurtzite-type crystal lattice. These substitutions reduced the electrical conductivity in the gallium oxynitride semiconductor. A new oxynitride, Li2Ga3NO4, was also obtained with Li2CN2 impurity using similar preparations from a mixture of Li/Ga?1. The crystal structure was isostructural with h-GaN, and was refined as P63mc with a=0.31674(1) nm, and c=0.50854(2) nm. The Ga and Li occupancies at the 2b site were refined to be 0.6085 and 0.3915, respectively, assuming that the other 2b site was randomly occupied with 1/5O and 4/5N. When the new compound was washed for over 1 min for the removal of Li2CN2 impurities, it was decomposed to a mixture of α-GaOOH and α-LiGaO2. The as-prepared product with Li/Ga=1 showed the highest intensity in yellow luminescence among the products under excitation at 254 nm. 相似文献
39.
稀土掺杂对锂离子电池正极材料LiMn2O4结构及电性能的影响 总被引:19,自引:5,他引:19
利用微波加热技术合成稀土掺杂基锂离子电池正极材料LiMn2-xRExO4(RE=Y,Nd,Gd,Ce),通过XRD、循环伏安及恒电漉充放电测试研究了稀土掺杂离子对合成正极材料结构及电化学性能的影响。XRD测试结果表明,合适的掺杂量可以起到扩展锂离子脱嵌通道和稳定骨架结构的作用,稀土离子的引入可以部分取代原有的三价锰离子,由于稀土离子的离子半径较三价锰离子大,因此稀土掺杂锰酸锂材料的晶胞参数比未掺杂材料大,在一定程度上扩充了锂离子迁移的三维通道,更有利于锂离子的嵌入与脱嵌;循环伏安及恒电漉充放电测试结果表明稀土掺杂有效提高了LiMn2O4材料的电化学循环可逆性及循环稳定性。 相似文献
40.
Characterization and electrochemical investigation of boron-doped mesocarbon microbead anode materials for lithium ion batteries 总被引:1,自引:0,他引:1
Mao-Hui Chen Guo-Tao Wu Guang-Ming Zhu Jin-Kua You Zu-Geng Lin 《Journal of Solid State Electrochemistry》2002,6(6):420-427
The structure and anodic performance of boron-doped and undoped mesocarbon microbeads (MCMBs) have been comparatively studied
and the results obtained by XPS, XRD, SEM, Raman spectroscopy and electrochemical measurements are discussed. It is found
that boron doping introduces a depressed d
002 spacing and the larger amount of "unorganized carbon", which induces vacancy formation in the graphite planes and leads to
a quite different morphology from that of the undoped material. Electrochemical charge/discharge cycle tests indicated that
after boron doping the lithium intercalation was carried through at a somewhat higher potential, being attended by greater
irreversible capacity loss.
Electronic Publication 相似文献