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981.
982.
Yani Zhang Yongdong Xu Jianjun Lou Litong Zhang Laifei Cheng Jianjun Lou Zhijun Chen 《International Journal of Applied Ceramic Technology》2005,2(2):114-121
Carbon fiber-reinforced silicon carbide matrix composites have the potential to overcome the shortcoming of the currently used carbon/carbon friction materials in aircraft brakes. In this article, the carbon/silicon carbide (C/SiC) composites were prepared by chemical vapor infiltration method, and the brake disks with different densities and component content were finally obtained. The friction coefficient and friction stability can be significantly improved by increasing both material density and carbon content. When the density of C/SiC composite is 2.3 g/cm3 , the coefficient of friction measured is 0.23, the coefficient of friction stability remains about 0.43, the liner wear rate is less than 9.3 μm/cycle, and the weight wear rate is less than 9.1 μm/cycle. The rapid increase of friction coefficient approaching the end of braking is mainly related to the increasing of surface temperature in a short time and the enhanced adhesion and abrasion of contact conjunctions and asperities. The C/SiC composites exhibited a good stability of braking against fading versus the braking number and surface temperature. The surfaces of C/SiC brake disks were covered with wear debris including the fragment of carbon fibers after the braking tests. The wear on the surfaces is significantly determined by cyclic mechanical and thermal stresses, which result in the micro-cracks in the SiC matrix, the thin flakes of the surface materials as well as the grooves. 相似文献
983.
The solid solution of CaTi1−x
Zr
x
O3 (x = 0–0.15) was successfully synthesized by the polymerized complex (PC) method. This study has exhibited the advantage of
the PC method to prepare a highly active CaTiO3 compared with the conventional solid-state reaction (SSR) method. More importantly, further improvement in phase purity and
large surface area was achieved by the doping of Zr4+, leading to remarkable enhancement of photocatalytic activities compared to pure CaTiO3. The quantum yield for H2 evolution over the most active photocatalyst, Pt (1.0 wt%)/CaTi0.93Zr0.07O3, was 1.91% and 13.3% in photoreactions from pure water and aqueous ethanol solution, respectively for 0.1 g photocatalyst,
which was about 3.3 and 2.5 times compared to that of PC-derived CaTiO3. 相似文献
984.
985.
986.
987.
988.
In this study, a thiirane resin was synthesized by the reaction of corresponding epoxy resin with KSCN. The synthetic conditions influencing the conversion of epoxy group were systematically investigated, such as the reaction temperature, reaction media, reaction time and the ratio of KSCN to epoxy group. It was found that the conversion of epoxy group increased with the increasing reaction temperature, improving the solubility of the mediate, extending reaction time, and the enhancing ratio of salt (KSCN) to epoxy group. Wherein, the reaction temperature and the ratio of the KSCN to epoxy group were more effective. For example, when the molar ratio of KSCN to epoxy group was equal to 2.0, the conversion of epoxy group got the maximum value, 0.65. In addition, the hot plate method was used to measure the gelling time of the resultant thiirane resin at different temperatures. It was found that the gelling time was reduced to 47–85% times as the corresponding epoxy resin depending on the conversion of the epoxy group, and the curing activation energy was diminished from 39 kJ/mol of epoxy resin to 17 kJ/mol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4023–4027, 2006 相似文献
989.
高岭土尾砂综合利用工艺研究 总被引:1,自引:0,他引:1
高岭土是制瓷工业的主要原料,在开采用加工过程中生产大量尾砂,污染环境且导致资源浪费,通过本试验研究,从尾砂中分选出工业上可综合利用的长石,云母等系列产品,并实现了无尾矿选矿新工艺。 相似文献
990.
The graft polymerization of methyl methacrylate and butyl acrylate onto poly(vinyl chloride‐co‐vinyl acetate) with atom transfer radical polymerization (ATRP) was successfully carried out with copper(I) thiocyanate/N,N,N′,N′,N″‐pentamethyldiethylenetriamine and copper(I) chloride/2,2′‐bipyridine as catalysts in the solvent N,N‐dimethylformamide. For methyl methacrylate, a kinetic plot of ln([M]0/[M]) (where [M]0 is the initial monomer concentration and [M] is the monomer concentration) versus time for the graft polymerization was almost linear, and the molecular weight of the graft copolymer increased with increasing conversion, this being typical for ATRP. The formation of the graft polymer was confirmed with gel permeation chromatography, 1H‐NMR, and Fourier transform infrared spectroscopy. The glass‐transition temperature of the copolymer increased with the concentration of methyl methacrylate. The graft copolymer was hydrolyzed, and its swelling capacity was measured. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 183–189, 2005 相似文献