The role of CuO–TiO2 additives in the preparation of high-strength porous alumina scaffolds using directional freeze casting

Lamellar porous Al2O3 scaffolds with initial solid loading of 30 vol% were prepared by freeze casting using micron-sized Al2O3 powders as raw material and CuO–TiO2 additives as sintering aid. The effects of the composition of CuO–TiO2 on the microstructure, porosity and compressive property of the Al2O3 scaffolds were investigated and the mechanisms for sintering promotion addressed. The sintering aid effect was prominent when CuO:TiO2 was 1:2 in mass and their amount reached 3 wt% of the total ceramic powders. The corresponding compressive strength reached 176 ± 20 MPa with the porosity being 45 ± 1 % after sintering at 1450 °C for 2 h. Activation of the Al2O3 lattice due to partial substitution of Ti4+ for Al3+ and formation of a low-melting eutectic liquid were presumed to play a significant role in the sintering and strengthening of the Al2O3 scaffolds.