Electrokinetic Behavior and Stability of Silicon Carbide Nanoparticulate Dispersions

Abstract

The stability of aqueous suspensions containing SiC nanoparticles prepared by inductively coupled plasma has been studied. Physicochemical analyses indicated that the as‐prepared samples consisted of monocrystalline spherical particles of the 3C‐SiC polytype with a mean diameter of about 40 nm. HRTEM clearly showed that the particles were covered by an amorphous surface layer which according to XPS was mainly composed of carbon. DTA and TG analyses showed that the free carbon was eliminated by heating the sample at 650°C in air, but the resulting powder exhibited an excess of amorphous SiO 2 on the particle surfaces. This silica coating was leached out by using a 5% HF solution. It has been determined, by evaluating an effective Hamaker constant, that the most stable aqueous suspensions are obtained by using the sample containing the amorphous SiO 2 surface layer. Finally, evidence of the presence of a strong hydrophobic force was detected in the original sample and in the one prepared by heating at 650°C and further leaching with HF.