Effect of Al2O3 particle size on preparation and properties of ZTA ceramics formed by gelcasting

Zirconia-toughened alumina (ZTA) ceramics were prepared using three different kinds of Al2O3 powders (marked PW-A average particle size: 7.53 μm, marked PW-B average particle size: 1.76 μm, marked PW-C average particle size: 0.61 μm) by gelcasting. Effect of Al2O3 particle size on zeta potential, dispersant dosage and solid volume fractions of ZTA suspensions as well as the mechanical properties of ZTA green bodies and ceramics were investigated. The optimum dosages of dispersant for ZTA suspensions prepared by PW-A, PW-B and PW-C are 0.4 wt%, 0.5 wt% and 0.7 wt%, respectively. The highest solid volume fractions of ZTA suspensions can reach 62 vol% (SP-A), 60 vol% (SP-B) and 52 vol% (SP-C), respectively. The green bodies show a bending strength as high as 20 MPa, which can meet the requirement of machining. The Al2O3 powder with fine particle size is beneficial to the improvement of mechanical properties. The ZTA ceramics prepared by PW-B Al2O3 powder show the highest bending strength (680 MPa) and toughness (7.49 MPa m1/2).