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991.
Effect of Microstructure on the Tribological and Mechanical Properties of CuO-Doped 3Y-TZP Ceramics 总被引:1,自引:0,他引:1
Shen Ran Louis Winnubst Dave H. A. Blank Henry R. Pasaribu Jan-Willem Sloetjes Dik J. Schipper 《Journal of the American Ceramic Society》2007,90(9):2747-2752
Dense 8 mol% CuO-doped 3Y-TZP ceramics were prepared by pressureless sintering for 8 h at 1500° and 1550°C, respectively. Transmission electron spectroscopy revealed that the ceramic sintered at 1500°C exhibits grain boundaries free of any amorphous phase, while crystalline copper-oxide grains were found in the zirconia matrix, whereas the sample sintered at 1550°C contains a Cu-rich amorphous grain boundary layer. The tribological behavior of these materials was tested under dry-sliding conditions using a pin-on-disk tribometer. The material sintered at 1500°C showed self-lubrication resulting in a low coefficient of friction ( f ) of 0.2–0.3 and a low specific wear rate ( k ) ≪ 10−6 mm3 ·(N·m)−1 . In contrast, the material sintered at 1550°C showed poor tribological behavior ( f =0.8–0.9; k ≫ 10−6 mm3 ·(N·m)−1 under the same conditions. The difference in the tribological behavior of these two materials was interpreted on the basis of mechanical properties and microstructural characteristics. 相似文献
992.
993.
994.
High Quality and Yield in Potassium Titanate Whiskers Synthesized by Calcination from Hydrous Titania 总被引:2,自引:0,他引:2
Ningzhong Bao Liming Shen Xin Feng Xiaohua Lu 《Journal of the American Ceramic Society》2004,87(3):326-330
Hydrous titanium dioxide (TiO2 · n H2 O) was used to prepare K2 Ti2 O5 single crystals, K2 Ti4 O9 whiskers and K2 Ti6 O13 whiskers at 820°, 940°, and 1110°C, respectively, by calcination. At T < 820°C, dehydration of hydrous titania, decomposition of potassium carbonate, and reaction between titanate and potassium oxide occurred simultaneously, ending with a crystallization reaction of K2 Ti2 O5 single crystals at 820°C. Subsequently, K2 Ti2 O5 single crystals convert into K2 Ti4 O9 whiskers at 940°C, and K2 Ti4 O9 whiskers further convert into K2 Ti6 O13 whiskers at 1110°C. The reaction temperatures for the generations of these types of potassium titanates were all 10°–40°C lower than the corresponding temperatures when anatase was used as the reactant. The whiskers synthesized in the present study exhibited uniform size, good morphology, and a high yield. 相似文献
995.
With superimposing a sine vibration of displacement on the extruding direction of a polymer melt, the characterization formula of the shear rate of a polymer melt within a capillary was set up. By making use of the experimental equipment of a constant velocity type dynamic rheometer of capillary (CVDRC) designed by the authors, the calculating steps of the shear rate of the polymer melt at the wall of the capillary under a vibration force field were established. Through measuring and analyzing the instantaneous data of capillary entry pressure, capillary volume rate, and their phase‐difference under the superimposed vibration, the polymer melt's shear rate at the wall of the capillary can thus be calculated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1056–1061, 2005 相似文献
996.
997.
Freestanding and crack-free titania–silica aerogels with high titanium content (i.e., Ti/Si = 1) were successfully prepared by adjusting the hydrolysis of the two alkoxide precursors to a comparable rate during the sol–gel processing. Two titania–silica aerogels were prepared by ethanol and CO2 supercritical drying methods. Well-dispersed, nanometer-sized anatase crystal domains (ca. 10 nm) were crystallized by high temperature, ethanol supercritical drying. The crystalline domains were solidly anchored to the aerogel network by Ti–O–Si bonds. Titania–silica aerogels prepared by CO2 supercritical drying method were devoid of TiO2 crystals. A molecular-level mixing was achieved and anatase TiO2 was only crystallized with difficulty by high temperature calcination (1073 K). Both aerogels were mesoporous and displayed similar open pore structure that is readily accessible to reactant molecules. However, only the titania–silica aerogel with anatase TiO2 prepared by ethanol supercritical drying was active for the gas phase, photocatalytic oxidation of volatile organic compounds (i.e., isopropanol and trichloroethylene). Catalysts prepared from Degussa P25 TiO2 displayed lower activity under similar reaction conditions. 相似文献
998.
通过研究XML在数据集成方面的相关技术,提出了一个基于XML企业电子商务异构数据集成框架,可以无缝地与面向对象系统、数据仓库系统等进行接口,能够较好地实现系统之间动态资源共享和交流,为企业之间对各种分布异构数据库资源提供了全局、统一、动态和高效的访问. 相似文献
999.
岩体是一种具有节理、裂隙等缺陷的材料体,这些缺陷是岩体渗流的主要通道。通常节理裂隙被认为是一组平行板分布,当原始地应力不变时,岩体的渗流状态保持不变。当岩体由于开挖卸荷或其它原因而导致岩体的应力状态发生变化,这时岩体的节理及裂隙等的隙宽或许将会变成楔形,从而使得岩体裂隙中的水头分布方式与平行板的线性分布不同。因此,在立方定律的基础上,推导了楔形裂隙中水头分布的公式,并与前人的研究结果进行了对比,同时探讨了其对边坡安全系数计算的影响,研究表明,所得公式更为合理。 相似文献
1000.
针对大坝预警指标阈值确定方法不完善、监控指标指导作用不强等问题,本文基于霍尔三维结构,系统阐述了大坝预警理论,构建了预警指标体系。通过将大坝监测数据正态分布计算转换成查询柯尔莫哥洛夫分布表,提出了基于小概率法的大坝多源监测预警阈值拟定方法。结合某水库观测数据,拟定该大坝表面沉降及渗流量的预警阈值,分析结果表明,该方法能够有效评估监测指标与历年来抵御不利工况的能力,更好的反映大坝运行状况,极大地提高了监测信息的预警价值。 相似文献