On the preparation of organosilanized silicon carbide aqueous suspension

Abstract The functionalization of ceramic nanoparticles with organosilanes is commonly employed to improve the surface adhesion mechanism for specific applications, especially in polymer composites. However, this surface modification changes the behavior of the nanoparticles in suspension, which is important for applications that require preparation involving aqueous medium. In the present study the influence of organosilanization on the size and stability of SiC particles in aqueous medium was evaluated. Initially, SiC particles were organofunctionalized using (3-aminopropyl) triethoxysilane through two different reaction routes (SiCSil I and SiCSil II). XPS spectroscopy of solid particles showed higher content of nitrogen atoms arising from the organosilanization reaction in the SiCSil II, prepared in ethanol. Compared to the unmodified SiC aqueous suspension, the organosilanized SiC aqueous suspensions presented much higher particle sizes, with the largest particle size distribution, assigned mainly to the organosilanization of SiC agglomerates. Subsequently, polyethylenimine (PEI) was tested as a dispersant for the aqueous suspensions, aiming to increase the repulsion forces among the particles and induce their de-agglomeration. The addition of PEI to SiC and SiCSil II particle aqueous suspensions resulted in a drastic reduction in the particle size (up to 40% (D50) at pH 5.5) and narrowest particle size distribution over a wide pH range. This fact was attributed to the PEI electrosteric effect on aqueous suspensions containing SiC or SiCSil II, which was supported by dynamic laser scattering and zeta potential results.