Silicon nitride is an inorganic substance with the chemical formula Si3N4. It is an important structural ceramic material with high hardness, inherent lubricity, wear resistance, and is an atomic crystal; it is resistant to oxidation at high temperatures. It can also resist thermal shocks, and will not break even if it is heated to more than 1000°C in the air, cooled rapidly, and then heated rapidly. It is precisely because of the excellent properties of silicon nitride ceramics that people often use it to manufacture mechanical components such as bearings, turbine blades, mechanical sealing rings, and permanent molds. If silicon nitride ceramics that are resistant to high temperatures and not easy to transfer heat are used to manufacture the heating surface of engine parts, it can not only improve the quality of diesel engines and save fuel, but also improve thermal efficiency. China, the United States, Japan and other countries have developed such diesel engines.

Silicon nitride ceramic materials have excellent properties such as high thermal stability, strong antioxidant ability, and high product dimensional accuracy. Since silicon nitride is a covalent compound with high bond strength and can form an oxide protective film in the air, it also has good chemical stability. It will not be oxidized below 1200℃, and the protective film formed at 1200~1600℃ can prevent further oxidation. It is not infiltrated or corroded by many molten metals or alloys such as aluminum, lead, tin, silver, brass, and nickel, but can be corroded by molten liquids such as magnesium, nickel-chromium alloy, and stainless steel.

Silicon nitride ceramic materials can be used for high-temperature engineering parts, advanced refractory materials in metallurgical industries, corrosion-resistant parts and sealing parts in chemical industries, and knives and cutting tools in mechanical processing industries.

Since silicon nitride can form a strong bond with silicon carbide, aluminum oxide, thorium dioxide, boron nitride, etc., it can be used as a bonding material and modified in different ratios.

In addition, silicon nitride can also be used in solar cells. After the silicon nitride film is deposited by PECVD method, it can not only be used as an anti-reflection film to reduce the reflection of incident light, but also, during the deposition process of the silicon nitride film, the hydrogen atoms of the reaction product enter the silicon nitride film and the silicon wafer, playing a role in passivating defects. The ratio of silicon nitride nitrogen to silicon atoms here is not strictly 4:3, but fluctuates within a certain range according to different process conditions. Different atomic ratios correspond to different physical properties of the film. It is used for ultra-high temperature gas turbines, aircraft engines, electric furnaces, etc.