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Inorganic material ceramics - silicon carbide ceramics

wallpapers News 2020-05-18
Silicon nitride ceramic is a kind of inorganic material ceramic which does not shrink when sintering. Silicon nitride is very strong, especially 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.

Silicon nitride ceramic material has high thermal stability, strong oxidation resistance and high dimensional accuracy. Because of the silicon nitride is the covalent compound high bond strength, and oxide film formed in the air, and so also has good chemical stability, oxidation under 1200 ℃, 1200 ~ 1600 ℃ generated protective film to prevent further oxidation, and is not aluminum, lead, tin, silver, brass, nickel and so on many kinds of molten metal or alloy by infiltration or corrosion, but can be magnesium, nickel chromium alloy, such as stainless steel liquid and the corrosion.

Silicon nitride ceramic materials can be used in high temperature engineering parts, metallurgy industry and other aspects of advanced refractory materials, chemical industry corrosion resistant parts and sealing parts, machining industry tools and cutting tools.
There are two production methods of silicon nitride ceramic products, reaction sintering and hot pressure sintering. The reaction sintering method is to form the silicon powder or the mixture of silicon powder and silicon nitride powder according to the general ceramic production method. Then in the nitriding furnace, pre-nitriding at 1150~1200℃, after obtaining a certain strength, can be carried out mechanical processing on the machine tool, and then further nitriding at 1350~1450℃ for 18~36h, until all into silicon nitride. The resulting product is precise in size and stable in volume. The hot pressing sintering method is to combine si3n4 powder with a small amount of additives (such as MgO, Al2O3, MgF2, AlF3 or Fe2O3, etc.) and sintering under the pressure of over 19.6mpa and 1600~1700℃. Generally, the products produced by hot pressing sintering method have higher density and better performance than those produced by reaction sintering.

As an excellent high temperature engineering material, silicon nitride ceramic material can give full play to its advantage in the high temperature field. The future development direction of Si3N4 is: (1) give full play to and make use of the excellent features of Si3N4; (2) in Si3N4 powder sintering, develop some new flux, research and control the best composition of the existing flux; We improve the powder making, molding and sintering process; In order to make more high performance composite materials, the synthesis of Si3N4 and SiC was studied. The application of Si3N4 ceramics in automobile engines has opened a new stage for the development of new high-temperature structural materials.

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Tag: Silicon nitr