Silicon nitride ceramic is a superhard substance and an insulating material. It has lubricity, wear resistance, strong corrosion resistance, oxidation resistance at high temperature, and resistance to cold and heat shock. According to the experimental results: silicon nitride ceramics will not break when heated to above 1000°C in the air, cooled rapidly and then heated rapidly. Silicon nitride ceramics are high-temperature-resistant and high-strength structural ceramics with broad development prospects. Silicon nitride ceramics occupy an important position in high-tech ceramics, which have high performance (such as high strength, high hardness, good thermal shock resistance, high fatigue toughness, high room temperature bending strength, wear resistance, chemical corrosion resistance and very Good high temperature stability, oxidation resistance, etc.), compared with other ceramics, silicon nitride ceramics have a small specific gravity, low thermal expansion coefficient, good thermal shock resistance, and high fracture toughness. It is an ideal high-temperature structural material and high-speed cutting Tool ceramic materials. Therefore, silicon nitride ceramics have a wide range of uses in aerospace, automobile engine, machinery, chemical industry, petroleum and other fields, and have also created a new situation for the development of new high-temperature structural materials.

Preparation Technology of High Performance Silicon Nitride Ceramics

1. Selection of silicon nitride powder

There are two types of silicon nitride powder, one is α-Si ₃ N ₄ powder; the other is β-Si ₃ N ₄ powder. There are two main methods of preparing commercial silicon nitride powder on the market:

(1) Silicon powder direct nitriding method. The direct nitriding method of silicon powder is relatively mature in industrial production, can be produced on a large scale, and the production cost is relatively low. Therefore, most enterprises at home and abroad use this method to produce silicon nitride powder. However, the disadvantage of this method is that the silicon nitride powder produced by it tends to contain impurity elements such as Fe, Ca and Al.

(2) Silicon imine pyrolysis method. The silicon nitride powder prepared by the preparation method has extremely high α-phase content and excellent sintering activity, and is very suitable for sintering and preparation of high-performance silicon nitride ceramics .