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931.
932.
本文报导了浸渍法制备的W-Mn/SiO_2催化剂分别在Φ28和Φ38毫米反吹式流化床上进行的条件试验和300h稳定性试验结果。并用XRD、FT-IR、BET等方法对催化剂进行了表征。结果表明,该催化剂可适用于流化床,并具有较好的CH4氧化偶联制C2烃的催化活性和稳定性。催化剂的结构研究表明,经300h反应后,该催化剂中结晶形式的Na_2WO_4和Mn_2O_3均已消失;α-方石英结构已完全转变为α-磷石英和α-SiO_2石英,但催化剂的这种结构变化尚未对生成C2烃的收率和选择性产生明显影响。 相似文献
933.
苯环上取代基的性质对双卟啉分子内能量转移的影响 总被引:2,自引:0,他引:2
金属卟啉在光合作用中起重要作用,合成其聚合物并作为光合作用模拟体系研究其能量转移和电子转移过程,已成为化学领域的重要研究课题之一.用于光合作用活性中心模拟体的金属卟啉聚合物种类很多,本文参考Little方法合成2种未见报道的苯环上分别带推电子和拉电子取代基和以柔韧碳氢链相连的中位双卟啉p-ZnTPP/p-H_2TMPP和p-ZnTPP/p-H_2TCPP(图1),探索了取 相似文献
934.
935.
The surface properties of solders play an important role in its wettability. The poor wettability of the Sn-9Zn alloy has
prohibited its commercial application. In this paper, the solid surface properties of the Sn-9Zn alloy were studied by using
X-ray photoelectron spectroscopy (XPS). It was shown from the XPS analysis that zinc is highly enriched on the surface of
the Sn-9Zn alloy. Although the zinc concentration on the surface is greater than 9%, lanthanum is accumulated on the surface
of the Sn-9Zn-1La alloy. In addition, the analysis of the valence of tin and lanthanum indicated that tin and lanthanum could
form complex oxygen-containing salts so that the anti-oxidation of the solder was enhanced, and the wettability of the solder
was improved accordingly. 相似文献
936.
采用火焰原子吸收光谱法直接测定铅精矿中高含量的银,其程序是将样品于700℃灼烧30min,以盐酸溶解后配制成溶液,用空气-乙炔火焰光度法测定样品中银的含量。该法简便、快速,结果准确。 相似文献
937.
Yuan X Chen Z Qiao J Chai J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(10):1869-1873
The photophysical processes of copolymer formed by copolymerization of beta-naphthyl-methacrylate (NMA) with vinylcarbazole (VCZ) were studied. The results show that when the solution of copolymer (NMA-VCZ) in THF is located in a low concentration range (about 10(-8) mol/l), the fluorescence emission is in good agreement with that of NMA monomer and the excimer is formed with gradual increase in concentration of copolymer (NMA-VCZ). The fluorescence of copolymer (NMA-VCZ) can be efficiently quenched both by electron donors and acceptors where the quenching effects follow the Stern-Volmer equation. The dimolecular exciplex between copolymer (NMA-VCZ) and N,N-dimethylaniline (DMA) is formed and the triple exciplex is also observed in the same system. 相似文献
938.
Polyacrylamide (PAAm) gels were synthesized using cross-linkers with their potential functionality (twice the number of double bonds of a cross-linker) varying from six to sixteen. Improved electrophoretic separation and highly desirable porosity and sieving properties were observed for most of the PAAm gels containing novel cross-linkers. An increase in the potential functionality of cross-linkers used in PAAm gels was an important factor, influencing the pore size and pore size distribution of the network. 相似文献
939.
Jiuqiang Li Jing Peng Jinliang Qiao Dongbin Jin Genshuan Wei 《Radiation Physics and Chemistry》2002,63(3-6):501-504
Two ethylene–octene copolymers (POE) were irradiated with 60Co gamma radiation and influence of irradiation atmosphere, absorbed dose and heat treatment of samples on the crosslinking were studied. Thermal properties and crystalline morphology of non-irradiated and irradiated POE were determined by using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS), respectively. The Charlesby–Pinner equation was used to describe the relationship between absorbed dose and sol fraction. The gel fraction of irradiated POE was lower and decreased with the increase of octene content when irradiated in oxygen, compared to irradiation in nitrogen atmosphere. The gel fraction increased significantly with the increasing of absorbed dose for the two copolymers. Heat treatment of samples prohibited the crosslinking of irradiated POE. The DSC results indicated that a subtle change of thermal properties of POE was observed before and after gamma irradiation at low dose. No change was found from the WAXS spectra of non-irradiated and irradiated POE. For heat-treating samples, the Charlesby–Pinner equation can not fit perfectly with the relationship between the sol fraction and absorbed dose, but it fits well with the crosslinking reaction of POE pellets. 相似文献
940.
Undoped and Ce(4+) doped TiO2 thin films were prepared by sol-gel method. The samples were characterized using scanning electron microscopy, the photocatalytic
reactivity was evaluated by degradation of methylene blue in the aqueous solution. 0.5 wt. % Ce(4+) doped TiO2 thin films calcined at 400°C show the highest photocatalytic activity.
The text was submitted by the authors in English. 相似文献