Slurries containing well-dispersed ceramic particles are essential for further processing, such as tape casting and infiltration to a woven fabric, to produce high quality products. In this study, various types of suspensions were prepared with 4 different types of commercial dispersants to examine the dispersion mechanism and determine the optimum conditions for the microsized α- and 50 nm-sized β-SiC systems in a toluene/ethanol mixed solvent. According to the sedimentation and rheological results, 3 and 20 wt.% of a polyester/polyamine co-polymeric dispersant were found to be the most effective dispersant for α- and β-SiC suspensions, respectively. An electrostatic mechanism did not play a major role in the mixed solvent system when a dispersant was added. The optimum amount of dispersant for the slurry was less than that for the suspension due to the dispersing effect of the polyvinyl butyral (PVB) binder. Due to the high specific surface area of the nano-sized β-SiC powder, 40 wt.% binder resin was needed to achieve a tape with desirable properties, while 15 wt.% of binder was adequate for the slurry with α-SiC with a lower surface area. Overall, the tape properties, such as green morphology and density, were strongly related to the dispersion state of the slurry.

Keywords: SiC, Dispersion, Zeta potential, Tape casting.