silicon carbide ceramics properties and functions
The properties of special ceramic materials are determined by two factors. First of all, the material structure, the main chemical bond properties, crystal structure. They determine the properties of ceramic materials, such as high temperature resistance, semiconductor and insulation. Secondly, the microstructure includes distribution, grain size, shape, pore size distribution, impurities, defects, etc.
Ordinary ceramics are made from clay, feldspar and quartz by compounding and sintering. This kind of ceramics is hard in texture, no oxidation and rust, corrosion resistance, non-conductive, high temperature resistance, good processability, low cost, but low strength. Generally, the maximum temperature of use is not more than 1200 ℃. This kind of ceramics is widely used in electrical, chemical and other industries due to its large production and variety.
Silicon carbide ceramic is made of silicon carbide powder by powder metallurgy method through reaction sintering or hot pressing sintering process. Silicon carbide ceramics are characterized by high temperature strength, good thermal stability, wear resistance and creep resistance. It is suitable for casting metal parts such as thermowells, gas turbine blades, etc. At the same time, because of its high heat conduction capacity, it is also suitable for heat exchanger materials under high temperature conditions, and can also be used to make various pump sealing rings.
Silicon nitride ceramics have rich raw materials and good processability. They can be used to produce accurate parts of various sizes with low cost, especially those with complex shapes. The yield of silicon nitride ceramics is higher than that of other ceramic materials. Silicon nitride ceramics have good temperature resistance and high hardness, which is second only to diamond, boron nitride and other materials. When the engine is made of silicon nitride ceramic materials, the engine efficiency can be increased by 30% due to the increase of working temperature to 1370 ℃. Meanwhile, the fuel can be fully burned, and the pollution composition of exhaust gas will be greatly reduced, which not only reduces energy consumption, but also reduces energy consumption environmental pollution.
There are many kinds of other special ceramic materials. They have their own characteristics and can be made into various functional components. Lithium oxide ceramics are high-temperature materials, talc ceramics are high-frequency insulating materials, thoria ceramics are dielectric materials, barium titanate ceramics are photoelectric materials, and cermets such as borides, nitrides and silicides are ultra-high temperature materials. Ferrite ceramics are permanent magnets, memory magnets, magnetic heads and other materials. Rare earth cobalt ceramics are memory materials. Semiconductor ceramics are sub sensitive elements and solar cells.