Recrystallized silicon carbide is made of high-purity ultrafine silicon carbide as a raw material. Under the protection of high temperature (2200~2450℃) and a certain pressure atmosphere, evaporation, condensation recrystallization occurs, and particles coexist at the contact point to form a sintered body. It does not shrink, but has a certain number of pores.
In the absence of sintering aids, the growth of the sintering neck is generally completed by surface diffusion or evaporation-condensation mass transfer. According to the classical sintering theory, the sintering completed by these two mass transfer methods will not reduce the distance between the center of mass of the contacting particles, so that no shrinkage will occur on a macroscopic scale, that is, a non-densification process. To solve this problem and obtain high-density silicon carbide ceramics, people have taken many measures, such as using heat, adding sintering aids, or hot pressing and sintering aids.
The SiC content in RSiC is above 99%, and it does not contain grain boundary impurity phases, retaining many excellent properties of SiC, such as high temperature strength, corrosion resistance, thermal shock resistance, etc., so it is widely used in high-temperature kiln tools, combustion nozzles, solar thermal converters, diesel vehicle exhaust purification devices and metal smelting, etc., which have extremely demanding performance requirements.
1) Since the sintering mechanism is an evaporation-condensation process, there is no shrinkage during the sintering process, and no residual stress will be generated to cause deformation or cracking of the product.
2) RSiC can be formed by various methods such as grouting, gel injection molding, extrusion, and pressing. Since there is no shrinkage during the sintering process, as long as the size of the blank is controlled, it is easy to obtain products with relatively precise shapes and sizes.
3) The recrystallized SiC products after sintering contain about 10% to 20% residual pores. The porosity of the material depends more on the porosity of the blank itself and does not change significantly with the sintering temperature, providing a basis for porosity regulation.
4) Under this sintering mechanism, the material has many interconnected pores and is widely used in porous fields, such as exhaust gas filtration, fossil fuel air filtration, etc., which can replace traditional porous products.
5) RSiC has very clear and clean grain boundaries, without glass phase and impurities, because any oxide or metal impurities have been volatilized at high temperatures of 2150-2300℃. The evaporation-condensation sintering mechanism can also purify SiC (the SiC content in RSiC is more than 99%). It retains many excellent properties of SiC and can be applied to application requirements under high temperature strength, corrosion resistance, thermal shock resistance, and other working conditions, such as high temperature kiln furniture, combustion nozzles, solar thermal converters, metal smelting, and other environments with extremely demanding performance requirements.