1. Alumina ceramics
The ceramic is a kind of ceramic with Al2O3 as the main component (Al2O3 mass fraction > 45%). According to the different main crystal phase in the ceramic body, it can be divided into corundum porcelain, corundum mullite porcelain and mullite porcelain, etc.; it can also be divided into 75 porcelain, 95 porcelain and 99 porcelain according to Al2O3 mass fraction.
Application: alumina ceramics have high melting point, high hardness, high strength, good chemical corrosion resistance and dielectric properties. But it is brittle and bad in impact resistance and thermal shock resistance, so it can't stand the drastic change of environment temperature. It can be used to make furnace tubes, linings, spark plugs of internal combustion engines of high temperature furnaces, as well as cutting tools with high hardness. It is also a good material for sleeves of thermocouple.
2. Silicon carbide ceramics
Silicon carbide ceramics are characterized by high temperature strength, high heat conductivity, wear resistant, corrosion resistant and creep resistant. They are often used as high-temperature sintering materials in the fields of national defense, aerospace and other scientific and technological fields. It is used for nozzle of rocket tail, throat for pouring metal, sleeves of thermocouple, furnace tube and other high-temperature parts.
Application: due to the high heat conductivity, it can also be used as high temperature strength parts such as blades and bearings of gas turbines, high temperature heat ex changers and nuclear fuel sealing materials, etc.
3. Silicon nitride ceramics
Silicon nitride ceramic is a kind of inorganic ceramic material which does not shrink during sintering. The strength of silicon nitride is very high, especially the hot pressed silicon nitride, which is one of the hardest materials in the world. It has the properties of high strength, low density and high temperature resistance.
Si3N4 ceramic is a kind of covalent bond compound. Its basic structural unit is [SiN4] tetrahedron. The silicon atom is located in the center of the tetrahedron. There are four nitrogen atoms around the tetrahedron, which are located at four vertices of the tetrahedron. Then, in the form of three tetrahedrons sharing one atom, a continuous and solid network structure is formed in three-dimensional space.