Development and application of silicon nitride ceramics

Advanced structural ceramics can be classified according to their use:

(1) mechanical ceramics;

(2) Thermal machine ceramics;

(3) bioceramics;

(4) Nuclear ceramics and others. According to chemical composition, it can be divided into: (1) oxide ceramics (Al2O3, ZrO2, MgO, CaO, BeO, TiO2, ThO2, UO2); (2) nitride ceramics (Si3N4, Sailong ceramics, AlN, BN, TiN); (3) carbide ceramics (SiC, B4C, ZrC, TiC, WC, TaC, NbC, Cr3C2); (4) boride ceramics (ZrB, TiB2, HfB2, LaB2, etc.); (5) other structural ceramics (Mullet ceramics, MoSi ceramics, sulfide ceramics, composite ceramics, etc.).

Because advanced structural ceramics have a series of excellent properties such as high temperature resistance, high strength, high hardness, high wear resistance, corrosion resistance and oxidation resistance, they can withstand the harsh working environment in which metal materials and polymer materials are difficult to handle, and have become many emerging science and technology. The key to achieving this has broad application prospects in energy, aerospace, machinery, transportation, metallurgy, chemical, electronics and biomedical. Fountyl Fangtai new material produces high-end microporous ceramic suction cup porous ceramic, replacing imported.

Nitride ceramics are new high-temperature, high-strength, wear-resistant engineering structural ceramics that have been rapidly developed in the past 20 years. The difference between silicon nitride ceramics and general silicate ceramics is that the combination of nitrogen and silicon belongs to the bonding of covalent bond properties, and thus has the characteristics of strong bonding force and good insulation property.

The sintering of silicon nitride is different from the sintering process of general ceramics. The reaction sintering method is adopted. The silicon nitride ceramics produced by this method cannot achieve high density, and generally can only reach about 79% of the theoretical density. Thick-walled parts. One of the effective methods for increasing the density of silicon nitride ceramics is to perform pressure sintering at a high temperature, whereby a hot-pressed silicon nitride ceramic can be obtained, and the room temperature bending strength is generally 800 to 1000 MPa. If a small amount of hot-pressed silicon nitride with cerium oxide and aluminum oxide is added, the room temperature bending strength can reach 1500 MPa, which is among the best in ceramic materials and has high hardness. It is one of the hardest substances in the world; it is extremely resistant to high temperature and strength. It can maintain the high temperature up to 1200 °C without falling. It will not melt into a melt after heating, and will not decompose until 1900 °C. It has amazing chemical resistance and can withstand almost all inorganic acids (except hydrofluoric acid) and Less than 30% caustic soda solution can also resist the corrosion of many organic acids, and at the same time it is a high-performance electrical insulating material. Because of its small thermal expansion coefficient and strong resistance to temperature jerk, silicon nitride ceramics have excellent mechanical properties and have occupied an important position in the application of engineering technology.