Brief analysis of the nature and type of synthetic mullite

Mullite is a binary compound stably formed under normal pressure in the AL2O3-SiO2 binary system. The chemical formula is 3AL2O3, 2SiO2, and the theoretical composition is AL2O3, 71.8%, and SiO2 28.2%. Mullite is the name of the mineral, named after its natural minerals were discovered earlier on the island of Mull on the west coast of Scotland. Mullite is usually artificially combined by a sintering method or an electrofusion method. Synthetic mullite was first produced by capacitive method in 1926, and the sintering method was successfully developed in 1928. At present, the annual consumption of fused mullite in the world is 10,000-20,000 tons, and the sintered mullite is 500,000-600,000 tons.

 

Synthetic mullite is a high-quality refractory raw material, which has the characteristics of uniform expansion, excellent thermal shock stability, high load softening point, low temperature creep value, high hardness and chemical corrosion resistance. The mullite brick made of mullite is very easy to use.

The crystal structure of mullite is an orthorhombic system, which is a structure of sillimanite (AL2O3.SIO2) with oxygen vacancy defects, which is very similar to the crystal structure of sillimanite.

 

There are many types of synthetic mullite. According to the synthetic method, there are sintered mullite and fused mullite; according to the raw material, there are low-aluminum mullite, medium-aluminum mullite, high-alumina mullite and zirconium mullite; The types include calcined kaolin (low aluminum), calcined kyanite (medium aluminum), all-day fuel mullite (high aluminum), and high-purity mullite.