ELECTROKINETIC BEHAVIOR AND STABILITY OF SILICON-CARBIDE NANOPARTICULATE DISPERSIONS

The stability of aqueous suspensions containing SiC nanoparticles prep ared by inductively coupled plasma has been studied. Physicochemical a nalyses indicated that the as-prepared samples consisted of monocrysta lline spherical particles of the 3C-SiC polytype with a mean diameter of about 40 nm. HRTEM clearly showed that the particles were covered b y an amorphous surface layer which according to XPS was mainly compose d of carbon. DTA and TG analyses showed that the free carbon was elimi nated by heating the sample at 650 degrees C in air, but the resulting powder exhibited an excess of amorphous SiO2 on the particle surfaces . This silica coating was leached out by using a 5% HF solution. It ha s been determined, by evaluating an effective Hamaker constant, that t he most stable aqueous suspensions are obtained by using the sample co ntaining the amorphous SiO2 surface layer. Finally, evidence of the pr esence of a strong hydrophobic force was detected in the original samp le and in the one prepared by heating at 650 degrees C and further lea ching with HF.