Silicon nitride ceramic materials can be used for high-temperature engineering components, advanced refractory materials in the metallurgical industry, corrosion-resistant parts and sealing parts in the chemical industry, and cutting tools and cutting tools in the machining industry. Since silicon nitride can form a strong bond with silicon carbide, aluminum oxide, germanium dioxide, boron nitride, etc., it can be used as a bonding material and modified with different ratios. The relative molecular mass is 140.28. Gray, white or off-white. It is a high temperature insoluble compound, has no melting point, and has high resistance to high temperature creep. The binder-free reaction sintered silicon nitride has a softening point of 1800 ° C or higher; hexagonal system