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Silicon nitride ceramic is an inorganic material that does not shrink when sintered. It uses silicon powder as a raw material, and first makes the required shape by the usual molding method, and performs preliminary nitriding in nitrogen and at a high temperature of 1200°C, so that part of the silicon powder reacts with nitrogen to form silicon nitride, and then The second nitriding is carried out in a high-temperature furnace at 1350 ° C to 1450 ° C, and the reaction becomes silicon nitride. Silicon nitride with a theoretical density of 99% can be obtained by hot pressing sintering. The thermal conductivity of Si3N4 ceramics at room temperature ranges from 10 to 16 W / mK.
Main Feature
Si3N4 has a low coefficient of thermal expansion and high thermal conductivity , so it has excellent thermal shock resistance. Has high strength and impact resistance Much lighter than steel and engineering superalloys due to the low theoretical density of Si3N4
High temperature resistance, the strength can be maintained at a high temperature of 1200°C without falling, it will not melt into a melt after being heated, and it will not decompose until 1900°C, and has amazing chemical corrosion resistance, and can withstand almost all inorganic acids and 30 The caustic soda solution below 100% is also resistant to the corrosion of many organic acids; it is also a high-performance electrical insulating material.
Typical Application
Ball bearings, steam nozzles, glow plugs and other high temperature applications
Material Properties
| molecular formula | Si 3 N 4 |
| relative molecular mass | 140.28 |
| color | gray, gray black |
| crystal system | Hexagonal crystal system , the crystal is hexahedral |
| Preparation method of ceramic sheet | hot pressing |
| Relative density | 99.5% |
| density | 3.2+/-0.02 g/ cm3 |
| Moh's hardness | 9~9.5 |
| melting point | 1900°C (under pressure). Usually decomposes at 1900°C under normal pressure |
| Thermal expansion coefficient | 2.8~3.2×10-6/℃(20~1000℃) |
| specific heat capacity | 0.71J/g·K |
| Thermal conductivity | 15~20W / m·K |
| Elastic Modulus | 300~320GPa |
| Fracture toughness | 6.0~7.0 MPa.m |
| Bending strength | 650~750 MPa |
| Weber modulus | 10~12 |
| Solubility | Insoluble in water. Soluble in hydrofluoric acid. |
