Effects of porosity and pore size on the properties of AgO-decorated porous diatomite ceramic composites

Porous diatomite ceramics with different porosity and pore size were prepared by sintering compacts consisting of diatomite, different amounts of sodium carbonate or pore former with different particle size. Subsequently, AgO-decorated porous diatomite ceramic composites were synthesized by chemical oxidation using porous diatomite ceramics with different porosity and pore size as the carrier. The AgO contents of the composites were investigated as a function of porosity and pore size. The porosity and pore size of porous ceramics varied with the addition amount of sodium carbonate and particle size of pore former. The AgO content of the composites increased with the increase of the porosity. The pore size seriously influenced the content of AgO deposit on porous ceramics. When the pore size of porous ceramics was in the submicron range (<1 μm), only a thin layer of submicron AgO particles could be deposited onto the external surface, but AgO particles could not further deposit into the inner layer. For pore formers smaller than 400 μm, the AgO contents of the composites increased with increasing size of pore former. However, the AgO content of the composites decreased when the size was larger than 400 μm. XRD results showed the composites were composed of cristobalite, tridymite, AgO and Ag2O.