A kinetic investigation of CVD mullite coatings on Si-based ceramics

Chemically vapor deposited (CVD) mullite coatings were deposited on SiC substrates using the AlCl3, SiCl4, CO2, H-2 System in a hot-walled vertical type reactor. An empirical kinetic model was developed indicating that an intermediate gaseous reaction was kinetically significant to the growth rate of mullite on SiC. The kinetically limiting equation was defined between a temperature range of 673-1327 K and 30-400 mbar where temperature was defined as a function of reactor position. The growth rate and crystal structure of mullite were dependent upon temperature, pressure, reactant concentration, and reactant ratios. (C) 2001 Elsevier Science Ltd. All rights reserved.