Calcium-Dialuminate/Calcium-Hexaluminate/Corundum Composite Refractories

Calcium dialuminate (CA2) and Calcium hexaluminate (CA6) occur at CaO-Al2O3 system as important compounds. Composites combining CA2 with high melting point and high thermal expansion materials such as MgO and CaZrO3 show a lower thermal expansion due to the low thermal expansion coefficient of CA2. CA6 is considered as a promising material for its well stability in reducing atmospheres, improved corrosion resistance to alkali and low solubility in slag containing Fe2O3. Furthermore, thanks to the hexagonal platelet structure, well chemical consistence and similar thermal expansion coefficient with corundum, CA6 is introduced into the matrix of corundum ceramic as toughening phase.In this paper, CA2 and CA6 were synthesized respectively by reaction sintering and CA2/CA6/corumdom composite refractories were fabricated through adjusting the content of CA2 and CA6 in matrix in order to improve the thermal shock resistance of corundum refractories. What has been done in this paper is divided into three parts:The first part focuses on the sintering properties and reaction mechanism of CA2 and CA6 synthesized by two processing routes-CaCO3/ -Al2O3 and pure calcium aluminate/ -Al2O3, respectively. The effect of raw materials and compact pressures and reaction temperatures on the sintering properties of the product was studied. The microstructures of CA2 and CA6 were observed and the plantlet structure growth mechanism of CA6 was discussed.The second part focuses on the fabrication and properties of CA2/CA6//Al2O3 multiphase composites. The effect of the content of pure calcium aluminate or CaCO3 in the matrix on the sintering and mechanical properties , phase composition , thermal expansion, microstructure and slag resistance of CA2/CA6/Al2O3 multiphase composites were investigated.The final part focuses on the fabrication and properties of CA2/CA6/Al2O3 castable. The effect of the content of pure calcium aluminate in the matrix on the sintering and mechanical properties, phase composition , thermal expansion, microstructure and slag resistance of CA2/CA6/Al2O3 composites were investigated.