A method for gelcasting high-strength alumina ceramics with low shrinkage

A new kind of nontoxic, water-soluble copolymer consisting of isobutylene and maleic anhydride was used to gelcast alumina ceramics at room temperature in air. The polymer acts as both a dispersant and a gelling agent. The influence of the polymer on zeta potential, rheological and gelling behavior of the alumina slurry was studied. Copolymers with a lower molecular weight had greater dispersing ability. Copolymers with a larger molecular weight had greater gelling ability. Alumina slurries with solids loading up to 58 vol% were prepared by adding copolymer (0.3 wt%, relative to the powder) with both short and long molecular chains. Increasing solids loading from 50 to 58 vol% decreased the linear shrinkage from 4.63% to 1.50% after drying, and from 14.51% to 13.18% after sintering, respectively. A solids loading of 56 vol% was associated with the highest flexural strength, as high as 534 MPa.