XMCERA | Silicon Nitride Components

▼ Silicon Nitride Ceramic

Silicon nitride ceramic is a kind of inorganic material ceramic which does not shrink during sintering. It has the properties of high strength, low density and high temperature resistance, it’s one of the hardest substances in the world.

Low Density High strength High Strength
Heat Resistant High Thermal Conductivity

Silicon nitride ceramic is a kind of covalent bond compound, the basic structural unit is [SiN4] tetrahedron, silicon atom is located in the center of the tetrahedron, around which there are four nitrogen atoms, respectively located in the four vertices of the tetrahedron, and then in the form of three tetrahedron share one atom, to form a continuous and strong network structure in three-dimensional space.

silicon nitride rapid prototyping 1280 400

▼ Preparation Method

① Reaction sintering process

First, the silicon powder is pressed into the required shape of the green, into the nitriding furnace through the pre-nitriding (partial nitriding) sintering treatment, the pre-nitriding green has a certain strength, can be carried out a variety of mechanical processing (such as turning, planing, milling, drilling). Finally, the temperature above the melting point of silicon; The green billet is completely nitrized and sintered again, and the product with small size change is obtained (that is, after the green billet sintering, the shrinkage rate is very small, the linear shrinkage rate is < 011%). The product generally can be used without grinding.

② Hot pressing sintering method

Si3N4 powder and a small number of additives (such as MgO, Al2O3, MgF2, Fe2O3, etc.) were hot pressed and sintered at a temperature above 1600 ℃ and a pressure above 1916 MPa.

③ Atmospheric sintering process

In terms of increasing the pressure of sintering nitrogen atmosphere, the properties of increasing decomposition temperature of Si3N4 (usually at N2 = 1atm, decomposition starts at 1800℃) are used to conduct atmospheric sintering in the temperature range of 1700 — 1800℃, and then air sintering in the temperature range of 1800 — 2000℃.

▼ Related applications

• Using Si3N4’s light weight and high stiffness, it can be used to manufacture ball bearings, which have higher accuracy than metal bearings, generate less heat, and can operate in higher temperatures and corrosive media.

• The steam nozzles made of Si3N4 ceramics are wear-resistant, heat-resistant and have no obvious damage after being used in 650℃ boilers for several months.

Where high strength, low density and high temperature resistance are required, Si3N4 ceramics are suitable to replace alloy steel.

silicon nitride application combination