HOMOGENEOUS DISTRIBUTION OF SINTERING ADDITIVES IN LIQUID-PHASE SINTERED SILICON-CARBIDE

The addition of sintering additives to silicon carbide particles by el ectrostatic adsorption of colloidal Al2O3 and Y2O3 sols has been studi ed as a way to achieve an optimum homogeneity in the microstructure. T he adsorption behavior of the sol particles was examined by electropho retic measurements and X-ray fluorescence analysis. Both Al2O3 and Y2O 3 sols could simultaneously be adsorbed on the SIC particle surfaces. Viscosity measurements showed that the colloidal sol particles had a s tabilizing effect on the slip, and hence slips with relatively high so lid loadings could be prepared without adding extra dispersing agent. Liquid-phase-sintered silicon carbide materials (LPS-SiC) with 2 wt% A l2O3 and 1 wt% Y2O3 were prepared by freeze granulation/ pressing and sintering at 1880 degrees C for 4 h. The homogeneity of the green comp acts was quantified using a spot analysis technique in an electron pro be microanalyzer. It was clearly shown that the addition of sols gave a more homogeneous microstructure than the reference sample with Y2O3 and Al2O3 added as powders. The addition of sintering additives as sol s also enhanced the sintering behavior.