sintered silicon carbide (also known as atmospheric pressure sintering) is considered to be the most promising sintering method for SiC sintering.
Complex shapes and large sizes of SiC components can be produced by the pressureless sintering process. According to the different sintering mechanisms, the pressureless sintering can be divided into solid-phase sintering and liquid-phase sintering. Solid-phase sintering was first invented by American scientist Prochazka in 1974.He added a small amount of B and C in the sub-micron B-SiC, to achieve the silicon carbide. He added small amounts of B and C to sub-micron B-SiC and achieved pressureless sintering of silicon carbide, resulting in dense silicon carbide ceramics with a density close to 95% of the theoretical density. Subsequently, H. Hausner et al used a-SiC as the raw material and added B and C to also densify SiC. Many subsequent studies have shown that B and B compounds and Al and Al compounds can form solid solutions with SiC and promote sintering.The addition of carbon is to react with SiO2 on the surface of SiC to increase the surface energy, which is favorable for sintering. Solid-phase sintered silicon carbide ceramics.The grain boundary is relatively “clean”, basically no liquid phase exists, the grain is easy to grow at high temperatures. Therefore, when fracture is through the crystal Fracture, their strength and fracture toughness are generally not high, in 300-400MPa and 3.5-4.5MPa.M1/2.But they are more “clean” grain boundaries, high-temperature strength does not change with the increase in temperature, generally up to 1600 ℃, the strength does not change.
sintered silicon carbide in the role of additives, you can get high strength and toughness, and more forming methods.It is suitable for parts with complex shapes or large thickness. The disadvantages are higher sintering temperature, certain porosity, relatively low strength, and certain porosity.Strength is relatively low, and there is a certain volume shrinkage, these shortcomings to be gradually overcome.