According to the microstructure, refractory fiber can be classified into amorphous and polycrystalline:

     The amorphous refractory fiber is an aluminum silicate fiber having an AL2O3 content of 45-60%. It is obtained by quenching the high temperature solution during the fibrillation process and has an amorphous glassy structure. Fibers made from natural raw materials (kaolin or refractory clay) are called ordinary aluminum silicate refractory fiber; fibers made from pure alumina and silica as raw materials are called high-purity aluminum silicate refractory fiber; Adding about 5% chromium oxide is called chromium-containing aluminum silicate fiber; AL2O3 is about 60% is called high-alumina fiber.

     The method for producing the amorphous refractory fiber includes blowing method and spun method, and is collectively referred to as a melting method. The blowing method is to melt the raw material in an electric arc furnace or an electric resistance furnace at 2000 °C or higher, and then spray the solution stream with compressed air or superheated steam to obtain a fiber. The spun method is to drop the solution stream on a multi-stage rotary furnace and spin it into fibers by centrifugal force.

     Above is the introduction of amorphous refractory fiber. Next episode we will introduce poly crystalline refractory fiber.