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71.
富镧和富铈混合稀土贮氢电极的性能 总被引:1,自引:0,他引:1
富镧和富铈混合稀土贮氢电极的性能*赵东江马松艳(黑龙江省绥化师专化学系绥化市152061)关键词混合稀土贮氢电极性能中图分类号O646.54混合稀土贮氢合金具有良好的电化学特性和较低的价格,成为贮氢电极研究的主要对象,已经开发出许多实用的电极材料[1... 相似文献
72.
E. Ma B. S. Lim M. -A. Nicolet M. Natan 《Applied Physics A: Materials Science & Processing》1987,44(2):157-160
The growth kinetics is characterized and the moving species is identified for the formation of Ni2Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a 100 Si substrate. The interfacial Ni2Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350–450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni2Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni2Si formation. 相似文献
73.
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75.
The thermal decomposition of cadmium acetate dihydrate in helium and in air atmosphere has been investigated by means of a
coupled TG-DTA-MS method combined with X-ray diffraction analysis. Dehydration of Cd(CH3COO)2·2H2O is a two-stage process with Cd(CH3COO)2·H2O as intermediate. The way of Cd(CH3COO)2 decomposition strongly depends on the surrounding gas atmosphere and the rate of heating. CdO, acetone and CO2 are the primary products of decomposition in air. In helium decomposition goes by two parallel and consecutive reactions
in which intermediates, Cd and CdCO3, are formed. Metallic cadmium oxidizes and cadmium carbonate decomposes giving CdO. Some of the metallic cadmium, depending
on the heating rate and the concentration of oxygen, evaporates. Acetone is partially oxidized in secondary reactions with
oxygen.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
77.
The preparation of pyrimidine-2-thione, pyrimidine-2-one, pyrimidine, and benzo[b][1,4]diazepine derivatives using traceless solid-phase sulfone linker strategy is described. Key steps involved are (i) sulfinate S-alkylation, (ii) sulfone anion alkylation with an epoxide, (iii) gamma-hydroxyl sulfone --> gamma-ketosulfone oxidation, and (iv) traceless product release by a one-pot elimination-cyclization process. Elimination-cyclization was carried out under basic conditions with thiourea, methyl thiourea, methyl urea, guanidine hydrochloride, benzamidine hydrochloride and ortho-phenylene diamine. Twenty-three compounds were prepared, and 14 of them were evaluated by the Batrachotoxin (BTX) radioligand binding assay for their binding affinity to neuronal sodium channels. Compound 7c was found to be a potential neuronal sodium channels blocker. 相似文献
78.
Haralampus-Grynaviski N Ransom C Ye T Rôzanowska M Wrona M Sarna T Simon JD 《Journal of the American Chemical Society》2002,124(13):3461-3468
Urocanic acid, UCA, is characterized by two electronic transitions in the UV-B (280-320 nm) which comprise its broad absorption spectrum and give rise to wavelength-dependent isomerization quantum yields. The absorption spectrum of UCA extends into the UV-A (320-400 nm). Given the UV-A component of sunlight is significantly greater than the UV-B component it is hypothesized even weak UV-A photochemistry of UCA could be important for in vivo responses to UV radiation. Degenerate pump-probe experiments performed on t-UCA at several wavelengths in the UV-A reveal an excited-state absorption that undergoes a rapid, approximately 1 ps decay. Photoacoustic experiments performed on both the cis and trans isomers reveal the formation of a long-lived intermediate following UV-A excitation. The efficiency and action spectra for this latter photoactive process are presented and are similar for both isomers of UCA. Cholesterol hydroperoxide assays designed to investigate the nature of the UV-A photoreactivity of t-UCA confirm the production of reactive oxygen species. The bimolecular rate constant for the quenching of singlet oxygen by t-UCA is determined to be 3.5 x 10(6) M(-1) s(-1). Taking into consideration recent theoretical calculations and jet expansion studies of the electronic structure of gas-phase t-UCA, a model is proposed to explain the isomerization and photoreactivity of t-UCA in solution over the UV-A region. 相似文献
79.
The crystal structure of new compound Ba3BPO7 was determined by ab initio method from high-resolution conventional X-ray powder diffraction data. The Rietveld refinement converged to Rp=5.92%, Rwp=8.87%, Rexp=5.00% with the following details: Hexagonal, space group P63mc, a=5.4898 (1) Å, c=14.7551(1) Å, Z=2. The basic unit of the structure is the [BaO10]-[BO3]-[PO4] polar polyhedra-chain composed of Ba1-B-P-O cluster. These chains, running along c-axis, stack in a HCP mode to build the whole structure with triangular prism channels. The channels are parallel to c-axis too, in which Ba2 and Ba3 are located. 相似文献
80.
Linear scaling local correlation approach for solving the coupled cluster equations of large systems
A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs). By restricting double excitations from spatially close occupied LMOs into their associated virtual LMOs, the number of significant excitation amplitudes scales only linearly with molecular size in large molecules. Significant amplitudes are obtained to a very good approximation by solving the CCD equations of various subsystems, each of which is made up of a cluster associated with the orbital indices of a subset of significant amplitudes and the local environmental domain of the cluster. The combined effect of these two approximations leads to a linear scaling algorithm for large systems. By using typical thresholds, which are designed to target an energy accuracy, our numerical calculations for a wide range of molecules using the 6-31G or 6-31G* basis set demonstrate that the present local correlation approach recovers more than 98.5% of the conventional CCD correlation energy. 相似文献