Fabrication of porous alumina ceramics from powder mixtures with sol–gel derived nanometer alumina: Effect of mixing method

This work concerns a systematic study investigating the effect on microstructure, porosity and bending strength of the addition of small amounts of very fine sol–gel derived nanoalumina on a micron-sized alumina powder for the production of highly porous ceramics. Different ways of mixing, with the nanomaterial being either in powder form (γ-alumina) or in sol state (boehmite sol), were investigated for this purpose. It was observed that when small amounts of nanomaterial (4–6 wt%) are added both the bending strength and open porosity increase to a level depending significantly on mixing method and level of dispersion of nanoparticles into the coarse matrix. The increase in strength can reach 100% in case the nanomaterial is added in powder form and 500% in case of mixing in sol state.