What are the characteristics of pressureless sintering of SiC ceramics?

In recent years, with the development of sintering of silicon carbide products, the pressureless sintering process is adopted for silicon carbide ceramics, and the sintered products have excellent properties, so it has become a promising sintering method. It mainly includes:

Through pressureless sintering, the molding pressure of SiC ceramics is 140MPa, the holding time is 90s, the amount of binder is 3% of the total mass of materials, the sintering process of SiC ceramics containing C and B4C elements as sintering aids belongs to solid-state sintering, the sintering process is mainly controlled by diffusion mechanism, the sintering temperature is 2150 ℃, and the content of Al is 0_ 2O_ 3、K_ 2O、Na_ The sintering process of SiC ceramics is mainly controlled by interfacial reaction. The sintering temperature is 1350 ℃.

In addition, the density of SiC ceramics prepared by pressureless sintering process is 3.16g/cm-3 (relative density is 98.75%) and compressive strength is 550MPa. Add appropriate content of C + B_ The pressureless sintering process of silicon carbide with 4C sintering additive is simple and easy to control. The volume shrinkage of the ceramics after sintering is about 30% compared with that of the green body. The silicon carbide ceramics with higher density and better mechanical properties can be obtained.

Silicon carbide porous ceramic materials are prepared by molding and special high temperature sintering process with corundum sand, silicon carbide, cordierite and other raw materials as the main materials. It has the following characteristics:

• The porosity is high. The important characteristic of porous silicon carbide ceramics is that there are more uniform and controllable pores. There are two kinds of pores: open pores have the functions of filtering, absorbing, absorbing and eliminating echo, while closed pores are beneficial to blocking heat, sound and the transfer of liquid and solid particles.
• High strength. Porous ceramic materials are usually made of metal oxides, silicon dioxide, silicon carbide, etc. after high temperature calcination, these materials have high strength. In the process of calcination, the boundary part of raw material particles melt and bond, forming ceramics with high strength.
• The physical and chemical properties are stable. Silicon carbide porous ceramic material can resist acid, alkali corrosion, high temperature and high pressure. It is a kind of green and environmental protection functional material.
• High filtration precision and good regeneration performance. Porous ceramic materials used as filter materials have narrow pore size distribution range, high porosity and specific surface area. The filter materials are in full contact with the ceramic materials, and the pollutants such as suspended solids, colloids and microorganisms are blocked on the surface or inside of the filter media, and the filtration effect is good. After being used for a period of time, silicon carbide porous ceramic filter material can recover its original filtration capacity by backwashing with gas or liquid.