Preparation of Porous Mullite Ceramics Using Industrial Wasted Silica Fume

The porous mullite ceramics were prepared using silica fume and alumina powders by gel-casting and pressureless sintering process.The effects of composition and sintering temperature on formation of mullite,microstructure and mechanical properties of porous mullite ceramics were investigated.XRD,SEM and strength testing were used to characterize the porous mullite materials.The results showed that,sintering temperature and Al2O3/ SiO2 ratio have important influences on the formation of mullite.The formation of mullite derived from the reaction between SiO2 in the silica fume and Al2 O3 takes place at 1300℃,while mullite content reaches maximum when temperature raised to 1450 ℃.Meanwhile,the proper over-dose of silica fume is propitious to synthesize mullite with higher purity.When the Al2 O3 /SiO2 molar ratio was 3∶2.5,the mullite content,bulk density,porosity and compressive strength of porous mullite ceramics were 90%,2.51g/cm3,20.56%and 260.93MPa,respectively.