Surface properties and dispersion behaviors of SiC nanopowders

The surface properties of commercially available SiC nanopowders, purchased from three different vendors, are expected to vary in terms of their microstructure and chemistry. Studying the behavior of SiC nanopowder suspensions should clarify the correlation between the surface properties and the dispersion medium. The two impurity phases of the surface structures of the nanopowders, siliconoxycarbide (SiO_xC_y) and free carbon (mixed D and G bond structure), were analyzed by X-ray photoelectron spectroscopy and Raman spectroscopy. The role played by the particle surface state was further studied by chemical elemental analysis of silicon-rich (C/Si<1), stoichiometric (C/Si=1), and carbon-rich (C/Si>1) nanopowders. Suspensions prepared from silicon-rich and stoichiometric nanopowders were easily dispersed in ethanol and isopropanol and were stable over time. Conversely, the carbon-rich nanopowder barely dispersed in solvents, which is correlated with the presence of an inert free carbon layer on the particle surface, as well as the very fine particle size.