What are the effects of aluminum-silicon ratio and impurity composition in the production of electromelt mullite?

According to Al? O? -SiO? Binary phase diagram of the system, mullite composition in Al? O? 79%, SiO%21% or so is more appropriate, but considering the presence of a certain amount of impurities in the raw material, they will be reduced in temperature. O? And SiO? Reactions, corresponding changes in Al? O? /SiO2 ratio, so the actual Al? O? /SiO? The ratio will be slightly lower.
As for TiO? , CaO, MgO, R? O and other impurities, except a small amount of titanium can enter the mullite solid solution and exist in the glass phase, the rest can not be reduced to remove. Therefore, the increase of impurities will increase the content of vitreous and corundum, and make mullite form a coarse crystal structure, which will increase the porosity content of crystal making, reduce the thermal shock stability and erosion resistance, and prone to cracks.
Zircon mullite
In order to further improve the chemical attack resistance, thermal shock resistance and reduce the coefficient of expansion of mullite, it can be used in Al? O? -SiO? Introducing ZrO into the system? To achieve the purpose of improving the structure of mullite, mullite containing zirconium dioxide is zirconium mullite. Zircon mullite is generally prepared by electromelting.
ZrO? There are two functions of being introduced into mullite: 1. Forming a solid solution, activating the lattice and forming a vacancy; It can promote sintering; Using the ZrO? The phase transition toughening mechanism improves the high temperature mechanical properties when ZrO? When the mass fraction is between 15% and 30%, the stress-induced phase transformation is the main toughening method. ZrO? When the value is greater than 30%, the main toughening method is micro-crack.
Zirconium mullite is mainly used in the new type of casting steel slide plate, continuous casting ladle and long water mouth and the key parts of glass kiln.