High temperature sintering of SiC with oxide additives:: III.: Quantitative vaporization of SiC-Al2O3 powder beds as revealed by mass spectrometry

This high temperature mass spectrometric study is aimed at the quantitative vaporization of powder beds of SiC-Al2O3 and related triphasic SiC-Al2O3-C and SiC-Al2O3-Si powder mixtures. The quantitative evaluation of reaction enthalpies showed that the different vaporization processes are not equilibrium processes and all the vaporization reactions are kinetically hindered. The multiple Knudsen cell method is used to determine directly the condensation coefficients of the Al(g), Al2O(g), CO(g) and SiO(g) species. Further, the comparison with previous equilibrium pressures calculated using thermodynamics allows the calculation of the evaporation coefficients of these species from the condensation coefficients and the measured mass spectrometric pressures. Supersaturated or undersaturated resultant pressures for each species are used as a criteria in the choice of suitable powder beds. (C) 2002 Elsevier Science Ltd. All rights reserved.