18-October-2024
Silicon Carbide (SiC) ceramic is a polycrystalline industrial material, and its production process mainly includes three key steps: powder preparation, shaping, and sintering. This material can be divided into three types based on the sintering process: pressureless sintered SiC, reaction sintered SiC, and recrystallized SiC.
The preparation process of reaction sintered SiC(RBSIC) involves mixing a carbon source with SiC powder, then shaping the green body through slip casting, dry pressing, or cold isostatic pressing. Subsequently, in a vacuum or inert atmosphere, the green body is heated to above 1500°C, causing solid silicon to melt into a liquid state, which then infiltrates the porous green body through capillary action. The liquid silicon or silicon vapor reacts with the carbon in the green body to form β-SiC, which combines with the original particles to form the final product. The advantage of this process is its lower sintering temperature, lower cost, and higher degree of material densification, with almost no volume shrinkage, making it suitable for manufacturing large-sized and complex-shaped structural parts, such as high-temperature kiln furniture materials, radiation tubes, heat exchangers, and desulfurization nozzles.
Pressureless sintered SiC(PSSIC) is sintered at a temperature range of 2000~2150°C under atmospheric pressure by adding appropriate sintering aids. This technology is quite mature and is widely used in the manufacturing of wear-resistant and corrosion-resistant seals, sliding bearings, and other components.
The preparation of recrystallized SiC(RSIC) involves mixing SiC particles of different particle sizes in a certain ratio and then shaping them. In a high temperature above 2100°C and under a protective atmosphere, the fine particles gradually evaporate and precipitate at the contact points of the coarse particles, forming new grain boundaries and bridge structures, eventually forming a sintered body with a certain porosity. This material does not contain any metallic phase or glassy phase and has a high porosity, thus possessing excellent high-temperature resistance and thermal shock resistance. It is suitable for high-temperature kiln furniture, heat exchangers, or combustion nozzles, etc.
