Use of Mullite
Mullite (3Al2O3 · 2SiO2) is the only binary Al2O3-SiO2 phase material that exists at atmospheric pressure. Due to the scarcity of natural mullite, sintering and electric melting of mullite have been widely developed.
Mullite is a high-grade raw material with advantages such as uniform thermal expansion, good thermal shock resistance, high fire resistance under pressure, low creep, high hardness, and good chemical corrosion resistance
Mullite ceramics mainly include ordinary mullite ceramics and high-purity mullite ceramics.
Ordinary mullite porcelain: Made from natural minerals of the aluminosilicate series as the main raw material, using the reaction sintering method of making mullite petrified during the sintering process or the method of synthesizing mullite before forming and sintering.
Due to the low purity of raw materials and high impurity content, in addition to A12O3 and SiO2, its components also contain impurities such as TiO2, Fe2O3, CaO, MgO, Na2O, K2O, etc. Therefore, there is a considerable amount of glass phase in the product, resulting in poor mechanical and thermal properties, which hinders the full utilization of the excellent properties of mullite ceramics at high temperatures. Therefore, ordinary mullite ceramics in industry can only be used as general refractory materials in situations where temperature and high temperature strength requirements are not high.
High purity mullite ceramics: mullite ceramics without glass phase prepared by reaction sintering of high-purity Al2O3 powder and high-purity SiO2 powder or by synthesizing ultrafine high-purity mullite powder.
High purity mullite is a high-quality refractory raw material with characteristics such as uniform expansion, excellent thermal shock stability, high load softening point, low high-temperature creep value, high hardness, and good chemical corrosion resistance. In particular, the high performance high-purity mullite ceramics have a bending strength of 570MPa and a fracture toughness KIC of 5.7MPa at 1300 ℃, which are 1.6 times higher than those at normal temperature. This kind of strength and toughness not only do not decay but increase significantly with the increase of temperature, which is an excellent characteristic of high-purity mullite ceramics as high-temperature mate