Fabrication and structure of TiO2 coated open-cell mullite ceramics

Abstract

TiO2 coated open-cell mullite ceramics were fabricated with coating TiO2 sol on pores of mullite, and its processing parameters were investigated. Open-cell mullite ceramics were fabricated through a gel-casting process. Two kinds of mullite precursor powders were prepared by dissolution of two kinds of aluminum salts (AI(NO3)(3)center dot 9H(2)O; type I and Al-2(SO4)(3)center dot 16H(2)O; type II) into colloidal silica sols. To produce porous mullite ceramics, both mullite precursor powders and PMMA beads (approximate to 5 mu m) were co-dispersed by electrosteric stabilized mechanism in an aqueous system and then gel-casted. The green bodies were sintered above 1300 degrees C for 3hrs in air. The PMMA was offered as pores in sintered mullite bodies. The prepared open-cell mullite ceramics were dipped in TiO2 precursor solution. The sintered bodies coated with TiO2 sols were re-sintered below 1000 degrees C for 3hrs after drying at room temperature. The TiO2 was successfully coated into the open-cell mullite ceramics. The characteristics of each TiO2 coated porous mullite ceramics were investigated by XRD, SEM, porosimetry, as functions of aluminum salt and pH of sol. It was found that the synthesis behavior and the porosity of the mullite are strongly dependent upon aluminum salt species, resulting in different grain size, morphology, and pore size.