Aqueous gelcasting of silica ceramics using DMAA

A low-toxicity and water-soluble monomer N, N-dimethylacrylamide (DMAA) was used as gelling agent in gelcasting of silica ceramics. In order to prepare high solid loading and low viscosity gelcasting slurries, effects of various parameters such as zeta potential, pH value, dispersant dosage and solid loading on rheological behaviors of the suspensions were investigated. The results suggest that the best conditions are pH 7.7 and dispersant dosage 0.1 wt%. The maximum flexural strength of green bodies with only 2 wt% organics in the slurry could be up to 15.3 MPa. The sintering shrinkage, bulk density, coefficient of linear expansion and flexural strength of sintered ceramics are 5.2%, 1.95 g/cm³, 0.58×10^-6 k^-1 (200 C) and 67.4 MPa, respectively. The dielectric constant and loss (1 MHz) are 3.26 and 7.8×10^-4, respectively.