Processing of highly concentrated polyacrylamide-coated silicon carbide suspensions

By using a polyacrylamide (PAAM)-coated silicon carbide (SiC) powder, at pH=5, homogeneous and stable suspensions of proper rheological property and low viscosity, containing 55 vol.% solids, were prepared. Stability, Zeta-potential and the rheological property of suspensions were studied. To further improve the solids content, two sizes of powders were mixed and graded. When 52 wt.% coarse and 48 wt.% PAAM-coated SiC powder were mixed, the solids content of suspensions was 65–70 vol.%, and the suspensions were of proper rheological property, homogeneity and stability. The results showed that rheological property of suspensions containing coarse particles were shear thinning at a low shear rate and thickening at a high shear rate when the solids content was between 60 and 65 vol.%.