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采用溶胶凝胶-非均相沉淀法将二氧化硅(SiO2)包裹到碳化硅颗粒(SiCp)表面,并分析了加水量和 pH 值对正硅酸乙脂(TEOS)水解速率的影响。采用差示量热扫描(DTA-TG)分析复合粉体在加热过程中的物理和化学变化行为,并以此制定煅烧温度及烧成制度,进行常压烧结制备 SiCp-SiO2陶瓷复合材料;运用 X 射线衍射(XRD)、扫描电子显微镜(SEM)手段对样品性能和形貌进行表征;以阿基米德原理测试样品的密度,研究 SiCp-SiO2复合材料的烧成机制及影响因素。结果表明,采用溶胶凝胶-非均相沉淀的方法,可以将 SiO2 包裹到 SiCp 表面,获得复合粉体中的 SiCp 和 SiO2 两相之间混合均匀。过量的水有助于加快 TEOS的水解速率,先酸后碱催化的二步水解法可以大大缩短水解反应周期。复合粉体最佳烧结温度为 1500 ℃。
Silica (SiO2) was coated on the surface of SiCp by sol-gel-heterogeneous precipitation method. The effect of water addition amount and pH value on the hydrolysis rate of TEOS was also analyzed. The differential scanning calorimetry (DTA-TG) was used to analyze the physical and chemical behaviors of the composite powders during the heating process. Based on this, the calcination temperature and sintering system were determined and SiCp-SiO2 ceramic composites were prepared by atmospheric pressure sintering. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the properties and morphologies of the samples. The density of the samples was measured by Archimedes’ principle. The sintering mechanism and influencing factors of SiCp-SiO2 composites were investigated. The results show that SiO2 can be coated on the surface of SiCp by sol-gel-heterogeneous precipitation to obtain uniform mixing of SiCp and SiO2 phases in the composite powder. Excess water helps to accelerate the rate of hydrolysis of TEOS. After acid-base, the two-step base-catalyzed hydrolysis can greatly shorten the hydrolysis reaction cycle. The optimum sintering temperature of composite powder is 1500 ℃.