| Among the many ceramic materials, silicon carbide has excellent electrical, physical and chemical properties, such as high hardness, high temperature stability, low coefficient of expansion and good thermal conductivity,making SiC material and SiC-based ceramic composite materials in national defense, chemical, mechanical, metallurgy, electronics and other areas shows the superiority that the other materials can not be replaced, so it has been the research focus for materials scientists around the world. However, a single composition, and the preparation of superior SiC ultrafine powder depends largely on equipment and raw materials and the output is not high, so it is not easy to realize industrialization led to the high cost of the preparation of SiC powders,making SiC materials are expensive, and the promotion and application of the high-performance SiC materials are severely limited.In this paper, selecting TEOS as the silicon source and carbon source of sucrose,which both are wide sources and inexpensive, using pour-type hydrolysis precipitation method to replace the traditional titration-type sol-gel method, it is not only the process for preparation of the precursor system is simple and work efficiency is improved, but also successfully have prepared monodisperse nano-scale SiC precursor, which is one of the main features in this paper; at the same time, the introduction of continuous synthesis method has also significantly improved the yield of SiC powder, and have prepared granular ultrafine SiC powder which is component single, uniform particle size distribution, which have simple operation, and is suitable for industrial production as is the another important feature in this paper. Therefore, studies in this paper has laid a theoretical basis for low-cost mass production of SiC ultrafine powder. And it will play a positive role in promoting the industrialization of the production for high performance SiC materials, this studies in this paper is of great significance.Many studies show that improving the uniformity of the starting material affect synthesis temperature and morphology, to large extent. In this paper, TEOS and sucrose are used as the main raw material, anhydrous ethanol is used as co-solvent and ammonia is used as catalyst. It continuously synthesize superior performance, ultra-fine SiC powder through the hydrolysis-precipitation type. Thesis studied the hydrolysis of TEOS polymerization mechanism, the content of de-ionized water, the content of ammonia as catalyst,the content of anhydrous ethanol, and the impact which the hydrolysis temperature and hydrolysis time effect the former body size; paper also examined the thermodynamics of SiC powder prepared through Continuous synthesis Preparation,and the impact on the SiC powder phase composition which amount of added sugar, synthetic temperature, and push the boat speed effect. The results show that the optimum precursors for the hydrolysis-precipitation method into the type SiC as follows:hydrolysis temperature is 25℃, hydrolysis time is 1h; the best ratio of ingredients: TEOS:ETOH:H20:NH3.H2O=100:150:100:20, the best synthesis process of continuous synthesis for preparing SiC powder as follows:the speed of pushing boat is 0.5cm/min, synthesis temperature is 1550℃, and came to the best content of sucrose.It can be prepared ultra-fine particle size of about 100nm granular SiC powder and SiC powder particle shape is rules, join a small, decentralized nature of good through the continuous synthesis process, and tested calculated that yield is 90g/h with continuous Preparation of SiC powder synthesis, is suitable for promoting industrialization. |
PDF Full Text Request