Rheology and pressure filtration of aqueous SiC suspensions of nanometer-sized bimodal particles

The consolidation behavior of mixed SiC particles (30 and 800 nm diameters) at pH 7 was examined using a developed pressure filtration apparatus at a constant crosshead speed of a piston. The addition of 30 nm SiC to 800 nm SiC changed the rheological properties of colloidal suspension from Newtonian to pseudoplastic flow through Bingham flow with increasing amount of 30 nm SiC. A phase transition from a well dispersed suspension to a flocculated suspension occurred when the applied pressure exceeded a critical pressure (ΔPtc). The ΔPtc value decreased with increasing amount of 30 nm SiC. The packing density of bimodal SiC particles was analyzed based on the partial molar volume of each powder. The larger particles were more densely packed than the smaller particles in the mixed powder compact.