Gelcasting of alumina ceramics (1) Dispersion and rheology of the suspension

The dispersion and rheology of alumina aqueous suspension for gelcasting have been investigated. According to the dispersing mechanisms for solid powders dispersed in liquid, the suspension with least deposition and best dispersion effect have been gotten by adjusting the pH value and adding dispersants. The results showed that both pH value and amount of dispersant can affect the dispersion effect and rheology, the optimum had been achieved when pH=9 and the amount of dispersant was 0.25%(mass percent). On this basis, the solid content effect on rheology of alumina aqueous suspension has been investigated, and the high solid content of alumina aqueous suspension with 51.28%(volume percent) and 969 mPa·s viscosity has been prepared which fully fits into gelcasting.