Why silicon nitride can resist cold and hot shock?
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Author : Lzh
Update time : 2023-02-02 16:02:41
What is silicon nitride? Silicon nitridecan resist the impact of cold and heat. It can be heated to more than 1000 ℃ in the air and will not be broken after sharp cooling and heating. Because silicon nitride ceramics have such excellent characteristics, people often use them to manufacture mechanical components such as bearings, turbine blades, mechanical seal rings, permanent moulds, etc. Suppose silicon nitride ceramics that are high temperature resistant and not easy to heat transfer are used to manufacture the heating surfaces of engine components. In that case, it can improve the quality of engines, but This kind of engine has also been developed in China, the United States, Japan and other countries.
Physical Properties of Silicon Nitride The relative molecular weight is 140.28, grey, white or grey-white. It is a high-temperature insoluble compound with no melting point and strong resistance to high-temperature creep. The load softening point of reaction sintered silicon nitride without binder is above 1800 ℃; Hexagonal crystal system. The crystal is hexahedral. The density of Si3N4 obtained by the reaction sintering method is 1.8~2.7 g/cm3, and the density of Si3N4 obtained by the hot pressing method is 3.12~3.22 g/cm3. The Mohs hardness is 9~9.5, the Vickers hardness is about 2200, and the microhardness is 32630 MPa. The melting point is 1900 ℃ (under pressure). It is usually decomposed at 1900 ℃ under normal pressure. The specific heat capacity is 0.71 J/(g · K). The generated heat is -751.57 kJ/mol. The thermal conductivity is (2-155) W/(m · K). The linear expansion coefficient is 2.8~3.2 × 10-6/℃ (20~1000 ℃), insoluble in water and hydrofluoric acid. The temperature at which oxidation starts in the air is 1300~1400 ℃. The specific volume resistance is 1.4 at 20 ℃× 105 · m and four at 500 ℃× 108 · m. The elastic modulus is 28420~46060 MPa. The compressive strength is 490 MPa (reaction sintered). At 1285 ℃, it reacts with dicalcium dinitrate to generate calcium nitride, and at 600 ℃, the transition metal is reduced to release nitrogen oxides. The bending strength is 147 MPa. It can be made by heating silicon powder in nitrogen or reacting silicon halide with ammonia. The resistivity is 1015-1016 Ω. cm. It can be used as the raw material of high-temperature ceramics.
Production method of silicon nitride There are two production methods for silicon nitride ceramic products, namely, the reaction sintering method and the hot pressing sintering method. The reaction sintering method forms silicon powder or a mixture of silicon powder and silicon nitride powder according to the general ceramic product production method. Then, in the nitriding furnace, pre-nitriding at 1150~1200 ℃. After obtaining a certain strength, mechanical processing can be carried out on the machine tool, and then further nitriding at 1350~1450 ℃ for 18~36h until they become silicon nitride. The size of the products made in this way is accurate, and The volume is stable. The hot pressing sintering rule is that silicon nitride powder and a small number of additives (such as MgO, Al2O3, MgF2, AlF3 or Fe2O3) are pressed into hot shape and sintered at a pressure of more than 19.6 MPa and a temperature of 1600~1700 ℃. Generally, the products produced by hot pressing sintering have higher density and better performance than those produced by reaction sintering.
Price of silicon nitride Silicon nitride particle size and purity will affect the product's price, and the purchase volume can also affect the cost of silicon nitride. A large amount of large amount will be lower. The price of silicon nitride can be found on our company's official website.
Silicon nitride supplier Luoyang Tongrun Nano Technology Co. Ltd. (TRUNNANO) Luoyang City, Henan Province, China, is a reliable and high-quality global chemical material supplier and manufacturer. It has more than 12 years of experience providing ultra-high quality chemicals and nanotechnology materials, including silicon nitride, nitride powder, graphite powder, sulfide powder, and 3D printing powder. If you are looking for high-quality and cost-effective silicon nitride, you are welcome tocontact us or inquire any time.
