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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 0.1wt%. The maximum flexural strength of green bodies with only 2wt% organics in the slurry could be up to 15.3MPa. The sintering shrinkage, bulk density, coefficient of linear expansion and flexural strength of sintered ceramics are 5.2%, 1.95g/cm3, 0.58×10−6 k−1 (200°C) and 67.4MPa, respectively. The dielectric constant and loss (1MHz) are 3.26 and 7.8×10−4, respectively. [ABSTRACT FROM AUTHOR]

A non-aqueous gel casting process based on the mixed solvent (ethanol and polyethylene glycol) and low-toxicity N,N-dimethylacrylamide (DMAA) was developed for an aluminum nitride (AlN) ceramic. In the present work, rheological properties of non-aqueous concentrated AlN suspensions were investigated in the presence of mixed solvent, dispersant, milling time, monomer and solid loading, in order to screen for the most suitable experimental conditions to obtain a good rheological behavior for gel casting. The results showed that the 50 vol% slurry with 0.2 wt% dispersant concentration, 2 h milling time, 6 wt% -monomer content, and a solvent ratio of 3:1, can meet the requirements for the casting process of AlN ceramic slurries. After being dried at 100 °C for 1 h, the optimum bulk density and maximum flexural strength of the AlN green bodies were as high as 1.97 g/cm 3 and 18.68 MPa, respectively. SEM photographs revealed that the green body had a relative uniform microstructure when the solid loading was 50 vol%. The shrinkage and deformation of shaped sintered bodies prepared through gel casting were small after sintering. The sintering shrinkage, apparent porosity, bulk density and flexural strength were 14.8%, 0.22%, 3.21 g/cm 3 and 310 MPa, respectively. [ABSTRACT FROM AUTHOR]