Ceramic fiber is a kind of fibrous lightweight refractory integrating traditional thermal insulation material, refractory material and excellent performance. Its main chemical composition is aluminum silicate, which can be divided into two categories according to its mineral composition: glassy fiber and polycrystalline fiber. Glassy fiber is an amorphous solid fiber formed by molten liquid state in cooling; Polycrystalline fibers are usually formed by colloidal injection method (or wire throwing method) and calcined at high temperature.

The diameter of ceramic fiber is generally 2mm-5mm, and the length is mostly 30mm~50mm. The fiber surface is smooth cylindrical, and the cross section is usually circular. Its structural characteristics are high porosity (generally greater than 90%), and the pore diameter and specific surface area are large. Because the air in the pores has good heat insulation effect, Therefore, the size of pore size and the nature of pores (open or closed pores) in fibers have a decisive impact on their thermal conductivity. In fact, the internal structure of ceramic fiber is a mixed structure composed of solid fiber and air. Its microstructure is characterized by continuous existence in both the solid phase and the gas phase. Therefore, in this structure, the solid material exists in the form of fiber and forms a continuous skeleton, while the gas phase exists continuously in the gap between the fiber material and the skeleton. It is precisely because of this structure that the ceramic fiber has high porosity, large pore diameter and specific surface area, so that the ceramic fiber has excellent heat insulation performance and small bulk density. The manufacturing method of ceramic fiber is as follows:

Chemical vapor phase reaction method: the chemical vapor phase reaction method uses Bo as raw material, melts and spins b:o fiber, and then heats it in low temperature and ammonia gas to make Bo react with ammonia gas to form ammonia 4 intermediate compound, and then heats the unstable fiber to 1800 ℃ in ammonia gas and mixed gas of ammonia and nitrogen under tension to convert it into BN fiber. Its strength can be as high as 2.1gpa, and its modulus can reach 345gpa.