The effect of solid volume fraction on properties of ZTA composites by gelcasting using DMAA system

The effect of solid volume fraction in slurries on properties of zirconia toughened alumina (ZTA, mass ratio of Al₂O₃-ZrO₂ is 75:25) green and sintered bodies prepared by gelcasting process was investigated. A low-toxicity gel system based on the polymerization of low-toxicity N,N-dimethyl acrylamide (DMAA) was used for the gelcasting. Effect of monomer mass fraction on viscosity of slurries and effect of solid volume fraction on properties of green and sintered bodies were investigated. The solid loading of suspension that can meet requirements for the casting process is as high as 54vol.%. However, it is found that the highest bending strength and fracture toughness of ZTA composites can reach 643.3MPa and 6.3MPam^1/2, respectively, when the solid loading was 50vol.%. The reason for this phenomenon is that the microstructure of the sintered samples is to a large extent determined by the rheological behavior of the suspension. SEM photographs revealed that the green body and sintered ZTA composites had a uniform microstructure when the solid loading was 50vol.%. When the solid loading was over 50vol.%, hard agglomerations formed which had a significant influence on the mechanical properties of ceramic bodies.