XPS STUDY ON THE DISPERSION OF CARBON ADDITIVES IN SILICON-CARBIDE POWDERS

Ceramic powder mixtures composed of silicon carbide and processing additives such as boron, carbon and binding agents were investigated by X-ray photoelectron spectroscopy. The novelty of this work consists in the application of a surface analysis technique to the study of ceramic green bodies. The analysis of freeze-dried powders, obtained from aqueous suspensions of the mixtures, reveals a strong C 1s lineshape dependence on the carbon dispersion and the milling procedure, which are important factors in the fabrication of high-density SiC components. In fact, the deconvolution of C1s bands allows a quantification of the spectral contribution of four carbon species assigned to C-Si, C-C, C-H and C-O species, so that a relative measure of the dispersion of carbon on the surface of the SiC particles is obtained. When carbon black or graphite are used as carbon additives it appears that carbon black is more dispersed than graphite at shorter milling times. For all samples studied, a good correlation is shown to exist between the intensity of the C-C carbon component in the C1s band and the density after sintering.