Composite modification of fine SiC powder by 3-aminopropyl triethoxysilane and sodium polystyrene sulfonate and its slip casting study

Composite modification of fine SiC powder was implemented by 3-aminopropyl triethoxysilane (KH550) and sodium polystyrene sulfonate (PSS) to improve the dispersion stability of fine powder in water. KH550 was adopted as preliminary modifier and then PSS was used for second modification of KH550-SiC powder. Adsorption studies proved the preliminary modification of KH550 contributed to the adsorption of PSS on SiC particle surface and PSS saturated adsorption capacity was 4.473 mg/g. After KH550 and PSS composite modification, the zeta potential, stability and dispersibility of fine SiC powder were improved. The absolute value of zeta potential of KH550-PSS-SiC particle reached the maximum value of 46.4 mV at pH 12. KH550-PSS-SiC suspension had better stability at the pH range of 2-12. Subsequently, KH550-PSS-SiC powder was mixed with coarse SiC powder to prepare recrystallized SiC (RSiC) green body by slip casting. When the mass ratio of KH550-PSS-SiC powder to coarse SiC powder was 2:3, RSiC slurry with the solid loading of 70 vol% and the viscosity of 636.0 mPa·s was obtained and then dense RSiC green body was produced. The density of the prepared RSiC green body was 2.6603 g/cm3 and the relative density was 82.70%.