Two types of non oxide ceramics

Non oxide ceramics

Non oxide ceramics mainly refer to nitride ceramics, carbide ceramics, Boride ceramics and silicide ceramics. They are generally combined by strong Covalent bond. Non oxide ceramic raw materials rarely exist in nature. It requires artificial synthesis of raw materials, and then ceramic products are made by ceramic process; When synthesizing raw materials and sintering ceramics, oxides are easily generated, so they must be carried out in a protective gas. High chemical stability, high melting point, high strength, good thermal conductivity, semi conductivity, and easy oxidation and decomposition at high temperatures.

① Silicon carbide ceramics There are two crystal forms of silicon carbide (SiC) ceramics, one is α- SiC, belonging to Hexagonal crystal family, is high-temperature stable; Another type is β- SiC, which belongs to face centered Cubic crystal system, is stable at low temperature. β- SiC can be converted into β- SiC crystal form. Silicon carbide ceramics have high high-temperature strength, low high-temperature creep, high hardness, wear resistance, corrosion resistance, oxidation resistance, high thermal conductivity, high conductivity, and good thermal stability, making them excellent high-temperature structural ceramic materials above 1400 ℃. At first, it was mainly used as refractory materials and abrasive abrasives, such as nozzle bricks for steelmaking, furnace lining, kiln furniture, grinding wheels, etc. Later, it was gradually used in some technical fields as high-temperature structural materials or heating elements, such as rocket exhaust nozzles, gas turbine blades, electrodes of magnetohydrodynamic generators, electric furnace heating elements, etc.

② Silicon nitride ceramic silicon nitride (Si3N4) is a Covalent bond compound, which has two crystal forms, namely α - Si3N4 and β- Si3N4. α- Si3N4 is a needle like crystal, β- Si3N4 is granular crystal, both belong to Hexagonal crystal family. Due to the excellent performance of S13 N4 ceramics, they have been widely used in many industrial fields. Utilizing its high-temperature and wear-resistant performance, it is used in the rotor, stator, and vortex tube of gas turbines in ceramic engines; In water-free ceramic engines, they are used as piston caps, spark plugs, piston covers, cylinder liners, auxiliary combustion chambers, and parts for piston turbine combined aviation engines in diesel engines. Because of its good thermal shock resistance, corrosion resistance, small friction coefficient and small thermal expansion coefficient, it is widely used in metallurgy and Hot working industries for temperature measurement thermowells, molds, crucibles, combustion nozzles, heating body clamps, high-temperature blowers and valves; Used as a splitter ring in the steel industry for steelmaking horizontal continuous casting machines; Utilizing its corrosion resistance, good wear resistance, and good thermal conductivity, it is widely used in the chemical industry as ball valves, sealing rings, filters, and heat exchanger components. Utilizing its good wear resistance, high strength, and low friction coefficient, it is used in the mechanical industry as bearing balls, plating, ball seat groups, high-temperature bolts, molds, plunger pumps, sealing materials, etc. In addition, it is also used in electronic, military and nuclear industries, such as switching circuit substrates, film capacitors, high-temperature insulators, radar radomes, missile tailpipes, gun barrel linings, support for nuclear reactors, isolators and carriers of nuclear fission products.

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