Silicon Nitride Ceramic Processing

Silicon nitride ceramic is an inorganic material ceramic that does not shrink when sintered and has properties such as high strength, low density and high temperature resistance. It is a covalently bonded compound, the basic structural unit is [ SiN4 ] tetrahedron, the silicon atom is located in the center of the tetrahedron, around which there are four nitrogen atoms, which are located in the four vertices of the tetrahedron, and then in the form of every three tetrahedrons share one atom, forming a continuous and strong network structure in three-dimensional space.

Silicon nitride ceramics can be produced by the direct reaction of monolithic silicon with nitrogen or ammonia, and the earliest silicon nitride ceramics were produced by the nitridation reaction of Si powder blanks in 1955.

With the discovery of excellent mechanical properties, thermal properties, chemical stability and biocompatibility of silicon nitride ceramics, as well as the further development of powder preparation technology, sintering equipment, technology, silicon nitride ceramics are gradually being used in machining, automotive, aerospace, electronic circuits, wearable and other fields.

Silicon nitride ceramics have many advantages that metal materials and polymer materials do not have

1. Heat-resistant, at atmospheric pressure, Si3N4 has no melting point, and decomposes directly at about 1870℃.

2. High mechanical strength, hardness close to corundum, self-lubricating grinding. Room temperature flexural strength can be as high as 980MPa or more, can be compared with alloy steel, and the strength can be maintained to 1200 ° does not decline.

3. High thermal stability, small coefficient of thermal expansion, high thermal conductivity, thermal shock resistance from room temperature to 1000 ℃ thermal shock will crack.

4. chemically stable, corrosion resistance, in addition to hydrofluoric acid does not react with other inorganic acids, the concentration of caustic soda (NaOH) solution below 30% of the corrosion, but also resistant to the erosion of many organic substances, a variety of non-ferrous molten metal (especially aluminum liquid) does not wetting, can withstand strong radiation irradiation. 800 ° C dry atmosphere does not react with oxygen, more than 800 ° C, began to generate the surface of the Silicon oxide film as the temperature rises silicon oxide film gradually become stable, around 1000 ℃ can be generated with oxygen dense silicon oxide film can be maintained to 1400 ℃ basic stability.

5. Low density, small specific gravity, only 2/5 of steel, good electrical insulation.

6. Silicon nitride ceramics have good microwave performance, dielectric properties and high temperature strength, can be used as missiles and aircraft radomes.