Silicon nitride ceramic is a kind of synthetic material with strong covalent bond force between silicon and nitrogen atoms in its structure, so it has the characteristics of high strength, high hardness, corrosion resistance, oxidation resistance, wear resistance and good thermal shock resistance. It is considered to be a kind of engineering ceramic material with excellent comprehensive properties and can be used in the field of high temperature.
Silicon nitride properties
Silicon nitride ceramics have high fracture toughness and room temperature strength, even at high temperature, its strength will not decrease much, and its high temperature stability is good.
The properties of silicon nitride include:
1. Silicon nitride material has low linear expansion coefficient, good thermal conductivity and excellent thermal shock resistance.
2. The hardness of silicon nitride is very high, which is 99.5%, second only to a few superhard materials such as diamond and BN.
3. Silicon nitride has low friction coefficient, self-lubrication and wear resistance.
4. Silicon nitride has good mechanical properties, hot pressing and reaction sintering samples can obtain higher bending strength, even as high as thousands of MPA. It has good stability at high temperature, high bending strength at high temperature and little creep at high temperature.
5. Silicon nitride material has good insulation properties and is a good insulator material at high temperature.
6. The chemical property of silicon nitride is very stable, it is not eroded by all inorganic acids except hydrofluoric acid, and it can also exist stably in some bases.
7. When silicon nitride ceramics are oxidized, a dense silicon dioxide film is easily formed on the surface, which hinders the continued oxidation of silicon nitride ceramics. Its oxidation resistance temperature can reach 1400 ℃, and it can be used up to 1870 ℃ in reduction atmosphere.
8. Silicon nitride is not wetted with high temperature metal solution and molten slag, so it can be used as high temperature metal solution filter and excellent slag resistant material.
Silicon Nitride Uses in Refractory Industry
Silicon nitride ceramics are considered to be promising high temperature structural materials because of their excellent high temperature properties, such as high temperature strength, good wear resistance and corrosion resistance.
Due to the strong covalent bond and low diffusion coefficient at high temperature, silicon nitride ceramics must be manufactured with the help of high temperature, high pressure and sintering agent, otherwise it is difficult to produce high quality silicon nitride materials.
Silicon nitride generally exists in the form of bonding phase in refractories. Through nitriding and firing of metal Si, corundum or silicon carbide and other raw materials are combined together to achieve the purpose of combining difficult sintering materials. For example, silicon nitride bonded silicon carbide materials used in aluminum reduction cells are all bonded with nitrided Si3N4, and Si3N4 is often introduced into refractories in the form of powder.
1. Used in ironmaking refractories
In recent years, corundum-silicon carbide-silicon nitride-carbon products used in large blast furnaces have made great progress. Silicon nitride, silicon oxynitride or Cylon-bonded silicon carbide refractory products have been widely used in the middle part of large blast furnace and the load-bearing part of coke oven. In addition, corundum-silicon carbide-silicon nitride-carbon refractories are more and more used in torpedo cars, with good corrosion resistance, wear resistance and erosion resistance, and the service life of torpedo lining refractories is greatly improved.
2. Used in steelmaking refractories
In recent years, silicon nitride has been used in the skateboard at the bottom of the ladle. The addition of silicon nitride material to the skateboard improves the wear resistance, erosion resistance and service life of the skateboard, and reduces the cost of per ton steel for ladle refining.
3. Used in smelting refractories of aluminum, copper, zinc and other non-ferrous metals
Silicon nitride ceramic does not wet with metal solution at high temperature, so it can be used in high temperature components of non-ferrous metal smelting process, such as temperature measuring thermocouple casing, smelting furnace lining and various container linings, crucibles and so on. Silicon nitride ceramic products have good thermal shock resistance and can be used stably for a long time at high temperature or in high temperature-low temperature cycle.
4. Used in kiln furniture materials
Ceramic shed plate is a kind of silicon nitride bonded silicon carbide material prepared by reaction sintering with silicon carbide as particle raw material and metal Si as fine powder in high temperature nitrogen atmosphere, which greatly improves the properties of the material. Compared with the clay bonded silicon carbide panel, the high temperature performance of the material is greatly improved, and the problem of bulging failure caused by the oxidation of silicon carbide in the use of clay bonded silicon carbide is solved.
Silicon nitride Price
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Silicon nitride Supplier
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