Alumina Powder Dispersions in Molten Urea for the Preparation of Macroporous Alumina Ceramics by Freeze Casting

Alumina powder dispersions in molten urea medium were prepared using ammonium poly (acrylate) dispersant. The dispersant concentration for achieving very good dispersion of the powder was optimized through rheological measurements. The optimum dispersant concentration for alumina powder dispersion in molten urea (1.25 wt.% of alumina) is higher than that required in aqueous medium (0.35 wt%). The dispersions with alumina loading as high as 55 vol.% having low viscosity could be achieved in molten urea medium at 135 °C. The viscosity and yield stress of the alumina powder dispersions in molten urea is low enough for casting.