Alumina/zirconia ceramic membranes fabricated by temperature induced forming technique

It is well known that the fabrication technique of porous ceramic composites has a significant effect on their microstructure and properties. In the present study, alumina/zirconia ceramic composites doped with magnesia were fabricated by temperature induced forming technique using tri-ammonium citrate and polyacrylic acid (PAA) as dispersant and gelling agents, respectively. The zirconia content was up to 20 wt% and added at the expense of alumina while the magnesia content was up to 2 wt% over the total mass. The optimum amount of ammonium citrate tribasic needed for dispersing the ceramic slurry was determined by measuring zeta potential of slurries. The prepared green alumina/zirconia composites were subjected for solid state sintering at 1550 °C for 1 h. The densification parameters, phase composition, average pore diameter, microstructure and cold crushing strength of sintered alumina/zirconia ceramics were investigated by the suitable techniques. The results revealed that the addition of tri-ammonium citrate to ceramic slurries enhanced the zeta potential which reached ?28.3 mV by adding 1 wt.-%. The bulk density was decreased while the apparent porosity was increased with the increase of zirconia content. The apparent porosities of sintered porous composites were in the range of 38.8–48.5%. The average pore diameter for the composite containing 15% zirconia was 1.79 μm and pore volume was 0.11 ml/g. The obtained microstructure exhibited zirconia grains located on the grain boundaries of Al₂O₃ matrix. The existence of zirconia in addition to magnesia hindered the growth and deformation of the matrix. The cold crushing strength of porous composites was decreased from 16.0 to 8.5 to MPa by increasing the zirconia content from 5 to 20 wt.-%.