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乙苯氧化脱氢钨硅酸催化剂的研究 总被引:1,自引:0,他引:1
考察了钨硅酸及其盐对乙苯氧化脱氢制苯乙烯的催化行为。认为表面积碳物是活性中心,苯乙烯的收率随积碳物C/H增大而增加;载体的比表面积对活性有明显影响。还发现有苯甲酸生成,CO_2主要来自表面积碳物的氧化。 相似文献
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H4PMo11Vo40杂多酸及其镧盐的合成与性质 总被引:3,自引:0,他引:3
本文提出主要用~(51)V NMR、CV并辅以IR、XRD、DTG、元素分析等作为有效地核查纯度和表征催化剂的手段。 相似文献
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Songqing Zhao Yuzi Liu Shufang Wang Zhen Liu Ze Zhang Huibin Lu Bolin Cheng 《Applied Surface Science》2006,253(2):726-729
B-doped ZnO thin films have been fabricated on fused quartz substrates using boron-ZnO mosaic target by pulsed-laser deposition technique, and the mechanical properties have been studied by nanoindentation continuous stiffness measurement technique and transmission electron microscope (TEM). Nanoindentation measurement revealed that the hardness of B-doped ZnO films, 9.32 ± 0.90 to 12.10 ± 1.00 GPa, is much greater than that of undoped ZnO films and very close to that of traditional semiconductor Si. The mean transmittance (%) is larger than 81% in the visible range (380-780 nm) for all the films, and the Hall effect measurement showed that the carrier density is around 2 × 1020 cm−3 and the resistivity lower than 3 × 10−3 Ω cm. TEM characteristics show undoped thin films have more amorphous area between grains while the B-doped ZnO films have thin grain boundaries. We suggest that the grain boundaries act as the strain compensation sites and the decrease in thickness of grain boundaries enhances the hardness of the B-doped ZnO films. 相似文献
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Tsutomu Takeichi Hiroshi Yada Yuzi Takayama Masami Morikawa 《Journal of separation science》1995,18(10):630-634
A chiral stationary phase prepared by bonding L -valine-t-butylamide to XE-60 has been coated on glass and metal capillaries. The performances of the chiral glass and metal columns were equivalent to those of commercial fused silica capillary columns. The thermal stability of the glass column was examined up to 280°C. It was found that no appreciable change in separation factor (α value) was observed up to 230°C. The α values gradually decreased between 240 and 260°C, and enantiomer separation was no longer achieved at 280°C. It was concluded that the allowable upper limit temperature of the chiral stationary phase is between 230 and 240°C in the isothermal mode, and ca 260°C in temperature-programmed mode. 相似文献
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在358K下用200ml/min的空气氧化碱性悬浮液合成了MFe_2O_(4+δ)(δ≥0,M=Fe、Co、Ni、Mn),并在573K下用40ml/min的H_2还原MFe_2O_(4+δ)制备了氧缺位铁酸盐MFe_2O_(4-δ)(δ>0)。用XRD、Mssbauer谱等测试方法对铁酸盐的结构进行了表征,考察了铁酸盐的组成及第二金属组分(Co、Ni、Mn)对铁酸盐还原性能的影响。在H_2还原3h内,铁酸盐氧缺位程度随还原时间增加而增大,晶格常数也相应增大;5h以上,铁酸盐将被还原为MO-FeO或α-Fe,晶格常数几乎不变。按Fe、Co、Ni、Mn顺序,MO与FeO的相互作用能力、MO-FeO固溶体的稳定性及铁酸盐还原为MO-FeO的能力均增强,MO-FeO进一步还原为α-Fe的能力却减弱。 相似文献
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Bing Shi Jon M. Hiller Yuzi Liu Chian Liu Jun Qian Lisa Gades Michael J. Wieczorek Albert T. Marander Jorg Maser Lahsen Assoufid 《Journal of synchrotron radiation》2012,19(3):425-427
X‐ray optics called multilayer Laue lenses (MLLs) provide a promising path to focusing hard X‐rays with high focusing efficiency at a resolution between 5 nm and 20 nm. MLLs consist of thousands of depth‐graded thin layers. The thickness of each layer obeys the linear zone plate law. X‐ray beamline tests have been performed on magnetron sputter‐deposited WSi2/Si MLLs at the Advanced Photon Source/Center for Nanoscale Materials 26‐ID nanoprobe beamline. However, it is still very challenging to accurately grow each layer at the designed thickness during deposition; errors introduced during thickness measurements of thousands of layers lead to inaccurate MLL structures. Here, a new metrology approach that can accurately measure thickness by introducing regular marks on the cross section of thousands of layers using a focused ion beam is reported. This new measurement method is compared with a previous method. More accurate results are obtained using the new measurement approach. 相似文献
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Tsutomu Takeichi Akiko Kobayashi Yuzi Takayama 《Journal of polymer science. Part A, Polymer chemistry》1992,30(12):2645-2652
Aromatic oligoamides of DP = 5 and 11 that have all meta-phenylene linkages were prepared by controlling the ratio of isophthaloyl chloride and diamines [m-phenylenediamine and bis(3-aminophenyl)acetylene], and then end-capped with aniline or 2-aminobiphenylene. Aromatic oligoamides having para-phenylene linkages were also prepared similarly using terephthaloyl chloride as a monomer. The oligoamides that have all m-phenylene linkages were soluble in organic solvents such as N-methyl-2-pyrrolidone and N,N-dimethylacetamide, though the oligoamides having p-phenylene linkages were much less soluble. The oligoamides having acetylene units in the backbone showed exotherm due to crosslinking. The onset of the exotherm appeared at 310-340°C for the oligoamides having all m-phenylene linkages, and 330-370°C for the oligoamides having p-phenylene linkages. They were melt-processed at 350 or 380°C for 1 h, giving tough and insoluble films from oligoamides having all m-phenylene linkages and brittle films from oligoamides having p-phenylene linkages. The films showed excellent thermal properties. For example, viscoelastic analyses showed little decrease of mechanical property up to 370°C, and Tg was not observed below the temperature. Thermogravimetric analyses also showed that thermal stability of the melt-processed films were excellent. © 1992 John Wiley & Sons, Inc. 相似文献
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污染环境中三维竞争系统的生存阈值 总被引:4,自引:0,他引:4
本文用积分均值法,首次讨论了带有毒素影响的三维竞争系统的Lotka-Volterra模型,得到了各种群平均持续生存与绝灭的阈值.文中所得结论对环境污染以及生物种群影响的理论研究和实际应用有重要意义.文[5,6]的主要结论包含在本文的结果中. 相似文献