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排序方式: 共有8628条查询结果,搜索用时 15 毫秒
41.
概括目前我国摩托车零件电镀所用镀层组合,对照有关金属覆盖层的国家标准,认为摩托车零件应用多层镍组合,并提供了工艺配方。 相似文献
42.
Cobalt catalysts supported on silica aerogel have been prepared using sol–gel chemistry followed by drying under supercritical ethanol conditions. Three different loadings of cobalt were synthesized: 2, 6, and 10% by weight. Transmission electron micrographs indicate that the metallic cobalt exists as discrete particles 50–70 nm in diameter for the 2 and 6% loadings. The 10% catalyst shows long needles of cobalt. BET and BJH measurements indicate that the catalysts retain the silica aerogel properties of high surface area (∼800 m2/g), large pore volume (∼5 cm3/g), and an average pore diameter in the mesoporous regime (∼25 nm). The catalysts were evaluated for Fischer–Tropsch activity in a laboratory-scale packed bed reactor. All three catalysts were active with the 10% Co catalyst achieving more than 20% CO conversion which corresponds to a rate of 1.53 g CO per g-cat per hour. The catalysts were selective for the C10+ hydrocarbons with more than 50% of the carbon contained within this fraction. A significant portion of the C9–C15 hydrocarbon product was observed as 1-olefins which reflects the enhanced mass transport within the very porous aerogel support. 相似文献
43.
离子束加速电压对真空电弧沉积Ti(C,N)涂层性能的影响 总被引:2,自引:0,他引:2
利用等离子辅助真空电孤沉积技术分别在高速钢片和单晶硅片制备了Ti(C,N)涂层,通过X-射线衍射和扫描电镜研究了不同离子加速电压对单晶硅片上涂层结构和组织形貌的影响,并测定了高速钢片上涂层的显微硬度,同时进行了耐磨性实验。结果表明:涂层主要由TiN和Ti(C,N)组成,随着离子束加速电压的增大,涂层的沉积速度增大,Ti(C,N)的衍射峰不断宽化,晶格尺寸发生变化,但其表面形貌不受影响;当离子束加速电压为1500V时,涂层有较高的耐磨性和显微硬度,当离子束加速电压为2500V时,涂层的耐磨性和显微硬度都有所下降: 相似文献
44.
A new CVD method without vacuum condition(CVDWV)was designed in this study,ithad been found that by modifying the flow rate of the carrier gas(N_2)and the temperature of sur-face reaction,silicon saturator and sample tube,the amount of silica deposited on the external sur-face of the zeolite could be precisely controlled,The changes in the physicochemical properties ofzeolite,such as pore-opening size,acidity and reaction property were investigated.The results ob-tained showed that:modification of the improved CVD method did not change the internal structureand acidity of the zeolite,but could bring about significant change of pore-opening size and reactionproperty as desired. 相似文献
45.
Benjamin F. Myers 《Journal of the American Ceramic Society》1992,75(3):686-693
The hydrolysis of uranium oxycarbide (UCO) was studied by injecting water vapor into a fuel element containing a known number of high-temperature, gas-cooled reactor (HTGR) coated particles with exposed fuel kernels. The experiments were conducted in the High Flux Isotope Reactor (HFIR) at temperatures between 700° and 1000°C, a system pressure of 200 kPa, and partial pressures of water vapor between 21 and 199 Pa. The general sequential response of the exposed fuel kernels to water vapor addition consisted of (1) a rapid release of stored fission gas with a concomitant increase in the steady-state release and (2) a period of constant steady-state release. Upon cessation of the addition of water vapor, a decline in the release to prehydrolysis values generally occurred. The release of stored fission gas was dependent on the square of the partial pressure of water vapor. The ratio of the constant steady-state release to the prehydrolysis value was independent of the partial pressure of water vapor. The time constant for the decline in the release was the same in all of the hydrolysis tests. 相似文献
46.
47.
化学镀镍复合配位剂的研究 总被引:1,自引:0,他引:1
采用对比试验和正交试验,以镀速、孔隙率、镀液稳定性和镀层硬度为评价指标,研究了单一配位剂及复合配位剂对镀液和镀层性能的影响,得到了复合配位剂的最优组合:8.4g/L乳酸,6g/L苹果酸,9g/L柠檬酸,8g/L丁二酸,1g/L丙酸。采用该复合配位剂的工艺配方可提高镀液使用寿命,获得性能优良的镀层。 相似文献
48.
49.
The initial rate of colloid deposition onto semi‐permeable membranes is largely controlled by the coupled influence of permeation drag and particle‐membrane colloidal interactions. Recent studies show that the particle‐membrane interactions are subject to immense local variations due to the inherent morphological heterogeneity (roughness) of reverse osmosis (RO) and nanofiltration (NF) membranes. This experimental investigation reports the effect of membrane roughness on the initial deposition of polystyrene latex particles on a rough NF membrane during cross flow membrane filtration under different operating pressures and solution chemistries. Atomic force microscopy was used to characterize the roughness of the membrane and observe the structure of particle deposits. At the initial stages of fouling, the AFM images show that more particles preferentially accumulate near the “peaks” than in the “valleys” of the rough NF membrane surface. 相似文献
50.
内蒙古花敖包特银铅锌矿床成矿特征研究与物化探勘查进展 总被引:1,自引:0,他引:1
花敖包特铅锌银矿床是近年来新发现的位于大兴安岭南段西坡银多金属成矿带上一重要矿床。自2000年通过土壤地球化学测量与激电测量发现本矿床以来,相继对该矿床进行了一系列地质基础理论研究以及有效勘查,包括通过各种地质方法揭示矿体成矿规律、探查矿体控制要素,运用物探勘查技术(高精度磁测、瞬变电磁法以及激电测量等)、化探勘查技术(土壤地球化学测量以及深穿透地球化学技术等)以及三维地质建模技术对矿区深部及其外围进行勘查,取得了一些新的认识,通过这些勘查研究显示本矿床在深部和外围仍具有良好的成矿前景。 相似文献