Andalusite : An Attractive Raw Material for its Excellent Thermal Shock Resistance
Volume 1, Issue 1, Pages 93 - 102
Andalusite, a natural aluminosilicate mineral provides high thermal shock resistance to refractory products. At high temperature (> 1200 °C), andalusite single crystal grains are transformed into a composite made of a 3:2 mullite single crystal with a capillary network filled with silica rich liquid. Because of the specific microstructure and the presence of the liquid phase, during thermal shocks, the mullitized andalusite crystals exhibit a behaviour typical of composite materials : microcracks are deflected by mullite/glass interfaces and stopped in glass zones. During a further heating, cracks generated by a thermal shock are healed. The composite microstructure of mullitized andalusite crystals seems to be a strong advantage in order to increase thermal shock resistance. It can explain the good behaviour of fired andalusite bricks regarding thermal cycling.