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建立了一个把增强颗粒球和基体空心球嵌入等效复合介质空腔中的“双层嵌套模型”,研究了颗粒增强材料自高温冷却下来时,不同相中热应力的分布特点。推出了热应力在弹性和弹塑性状态的各种表达式。研究表明,随着温度降低,增强体受到压应力,基体材料中存在的静水应力为拉应力。温度继续下降,将出现自增强颗粒与基体界面向外扩展的屈服区。随增强相体积分数增大,增强颗粒受到的压应力和基体中的静水拉应力减小,增强颗粒与基体界面屈服的起始温差增大,而基体材料全面屈服的温差却减小。 相似文献
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Zhang De-Qing Wang Shao-Jun Sun Hong-Shan Wang Xiu-Li Cao Mao-Sheng 《Journal of Sol-Gel Science and Technology》2007,41(2):157-161
Lead zirconate titanate nanopowders Pb(Zr0.52Ti0.48)O3 (PZT) were prepared by modified sol-gel process in ethylene glycol system with zirconium nitrate as the zirconium source.
The research showed that it was critical to add lead acetate after the reaction of zirconium nitrate and tetrabutyl titanate
in ethylene glycol system for preparing PZT of exact titanium content. The reaction mechanisms of the sol synthesis, preparation
of xerogel and agglutinating process were characterized through using FT-IR, NMR, TG-FTIR, and GC-MS. The experiment proved
that ethylene glycol system did not rely on hydrolysis and condensation reactions in the process of the sol formation, but
on the formation of chain or network large molecules from complexation of ethylene glycol and all Ti and minor Pd, Zr. In
the preparation of xerogel, the complexation reaction was so completed that it formed large molecules network composed of
metal and dioxyethyl. Bulk weight loss happened before 350°C in the process of sintering xerogel to prepare PZT nanopowders.
Volatile matters and vapor phase decomposition resultants were primarily oxy-compounds including ethylene glycol, aldehyde-ketone
compounds, carbon dioxide and nitrate radical conversion matters. After 350°C, primary vapor phase decomposition resultants
were carbon dioxide and minor carbonyl compound. 相似文献
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根据抗蛋白酶降解的长效肽设计思想, 合成了一系列新型结构的LHRH拮抗剂类似物. 体内生物活性评价结果表明, 所设计的多肽具有比母体肽和阳性对照更长的体内抑制睾酮作用时间和较低的最低有效剂量, 证实了该设计思想的可行性, 并为开发长效LHRH拮抗剂药物提供了新的候选化合物. 相似文献
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I2 is an effective promoter for the synthesis of 2,3-unsaturated glycosides via Ferrier glycosylation. This reaction was used in the present work for the synthesis of O-glycosylated Fmoc amino acid building blocks. This metal-free reaction afforded the desired products with good to excellent yields with good α-selectivity. 相似文献
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Copper phthalocyanine film, a p-type organic semiconductor, is synthesized by vacuum sublimation and its surface morphology is characterized by SEM. A silicon-based copper phthalocyanine film gas sensor for NO2 detection is fabricated by MEMS technology. The results show that the resistance and sensitivity of copper phthalocyanine film decrease obviously as the NO2 concentration increases from Oppm to lOOppm. However, the sensitivity nearly keeps a constant of O. 158 between 30 ppm and 70 ppm. The best working temperature of the gas sensor is 90℃ for NO2 gas concentrations of lOppm, 20ppm and 30ppm, which is much lower than that of general metal oxide gas sensor. 相似文献