Silicon nitride ceramic materials: Silicon nitride (Si3N4) ceramics are inorganic non-metallic covalent bonding compounds.

The characteristics of silicon nitride ceramics are as follows: high temperature resistance, low thermal conductivity, chemical inertness, good wear resistance, thermal shock resistance, and good self-lubrication.

Its basic structural unit is tetrahedron, silicon atoms are located in the center of the tetrahedron, four nitrogen atoms are located in the four vertices of the tetrahedron, and then in the form of each three tetrahedron share a silicon atom in three-dimensional space to form a continuous and robust network structure, many of the properties of silicon nitride are because of its special structure.

Silicon nitride (Si3N4) is an important structural ceramic material. It is a high-temperature structural ceramic, with high strength, high hardness, thermal shock resistance, corrosion resistance and good chemical stability and other excellent properties. Silicon nitride ceramics have high hardness, wear resistance, Mohs hardness is second only to diamond, cubic boron nitride, boron carbide, silicon carbide, is the fifth hard atmospheric pressure solid phase. It has high thermal stability, small coefficient of thermal expansion and good thermal shock resistance. At the same time, it also has excellent oxidation resistance, can be used in the air up to 1400 and is not oxidized. In addition, silicon nitride ceramics have good wet chemical corrosion resistance, can withstand almost all inorganic acids and less than 30% caustic soda solution, and can also resist many organic acids corrosion.

The preparation methods of silicon nitride ceramics mainly include reaction sintering, hot pressing sintering, air pressure sintering, atmospheric sintering and heavy sintering. The difference of these preparation processes will affect the microstructure and properties of silicon nitride ceramics.

Silicon nitride ceramics have a wide range of applications. In the metallurgical industry, it is used as crucible, flume and other refractory materials. In the mechanical industry, silicon nitride ceramics can be used as bearings, cylinder walls, nozzles, sealing rings, etc. In the chemical industry, it can be used as corrosion-resistant, wear-resistant parts, such as ball valves, pump bodies, seals, heat exchangers, etc. In the aerospace field, silicon nitride ceramics are used as parts of rocket nozzles and engines due to their high temperature resistance and oxidation resistance. In addition, in the field of microelectronics and optoelectronics, silicon nitride also plays an important role, such as as an insulating layer, packaging materials and so on.