Effects of different aluminum sources on morphologies and properties of ceramic floor tiles from red mud

Ceramic floor tiles with various surface morphologies of mullite were prepared from red mud and kaolin, α-Al2O3, ρ-Al2O3, γ-Al2O3 and Al(OH)3 as alumina sources. AlF3 and V2O5 were used as catalyst to promote the formation of mullite crystals at low temperature. Influence of Al2O3 crystal types and sintering temperature on microstructure and development of mullite, and performance of ceramic floor tiles were investigated. Results indicate that both the abilities of α-Al2O3, ρ-Al2O3, γ-Al2O3 and Al(OH)3 reacting with SiO2 and the reactivities of them increase successively, therefore the amount of generated needle-like mullite rise in that order. The better dispersion of acicular mullite throughout the ceramic matrix could significantly improve the properties of the ceramics. The ceramic floor tile with Al(OH)3 sintered at 1230 ℃ was found to possess the optimal performance. Under this condition, bulk density, flexural strength, porosity and water absorption of the ceramic floor tile were 1.83 g/cm3, 185.46 MPa, 18.56% and 7.37% respectively, meeting the requirements of building material. The results of this study will improve our understanding of recycling red mud for the fabrication of ceramic materials.