Silicon nitride ceramics are an inorganic material that does not shrink during sintering.It is made of silicon powder as a raw material. First, the desired shape is made by the usual molding method, then preliminary azotized in nitrogen under 1200℃, so that a part of the silicon powder reacts with nitrogen to generate silicon nitride, and then a second azotizing in a high temperature furnace of 1350℃ to 1450℃ to react into silicon nitride. Silicon nitride with 99% theoretical density can be made by thermal pressure sintering method. The thermal conductivity of Si3N4 ceramics at room temperature ranges from 10 to 16 W.m-1.K-1.
| Molecular formula | Si3N4 |
| Relative molecular mass | 140.28 |
| Color | Gray, gray black |
| Crystal system | hexahedral |
| Preparation method | heat pressing |
| Relative density | 99.5% |
| Density | 3.2+/-0.02 g/cm3 |
| Moh's hardness | 9~9.5 |
| Melting point | 1900℃ , Usually decomposed at 1900℃ at normal pressure |
| Thermal expansivity | 2.8~3.2×10-6/℃ (20~1000℃) |
| Heat capacity | 0.71J/(g·K) |
| Thermal conductivity | 15~ 20W/(m·K) |
| Modulus of elasticity | 300~320 GPa |
| Fracture toughness | 6.0~7.0 MPa.m |
| Flexural strength | 650~750 Mpa |
| Webpark Module | 10~12 |
| Solubility | Insoluble in water.Solute in hydrofluoric acid |
| oxidizing temperature | The temperature of starting oxidation in the air is 1300 to 1400℃ |
