study of Preparation of reaction bonded silicon carbide ceramics

Reaction sintered silicon carbide ceramics preparation process is relatively simple, it directly adopts a certain particle gradation of silicon carbide (generally 1-10um), and carbon mixing and molding of billet, and then at high temperatures for infiltration of silicon, part of the silicon reacts with carbon to generate SiC and the original billet in the combination of SiC, to achieve the purpose of sintering. There are various methods of silicon penetration, one is the temperature to reach the melting temperature of silicon, the liquid phase of silicon, through the role of the capillary, silicon directly into the billet and carbon reaction to generate silicon carbide, to achieve sintering. Another is that the temperature is greater than the melting temperature of silicon, the generation of silicon vapor, through the silicon vapor infiltration into the blank to achieve the purpose of sintering.

The former method of sintering residual free silicon is generally more, usually up to 10-15%, sometimes up to 15% or more, which will be detrimental to the product performance. Vapor-phase method of infiltration of silicon, due to the billet of the reserved pores can be as little as possible, the free silicon content after sintering can be reduced to less than 10%, and some good control of the process can be reduced to less than 8%, the performance of the product is greatly improved. Reaction bonded silicon carbide sintering temperature of 1450 ℃ to 1700 ℃. Carbon and SiC skeleton can be pre-turned into any shape, and sintering of the billet shrinkage of only 3% or less, which is conducive to the control of product size, greatly reducing the amount of grinding of the finished product, the use of raw materials such as SiC, C, bonding agent and so on are especially in need of special treatment, the market can be supplied. Therefore, the production cost of SiC sintered body prepared by this process is low, compared with several other processes, the price is relatively low, competitive. However, the process determines the total residual free silicon in the blank after sintering, this part of the silicon on the future application of the product has an impact on the strength of the sintered body is not as strong as other crafts, wear resistance decline. But the main thing is that free silicon can not resist the corrosion of alkali and hydrofluoric acid and other strong acid medium. Therefore its use is limited. In addition, the high temperature strength is also affected by free silicon, and the use temperature is limited to below 1200℃.

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