Direct transfer of kinetic data from a microbalance into a tube reactor for CVD BN on SiC fabrics

BN deposition from B,B',B "-trichloroborazine/Ar gas mixtures is investigat ed in a microbalance system with a parallel flow arrangement, and in a tube reactor for the deposition on the fiber surface of SiC fiber fabrics. The deposition rates, r(dep), in the microbalance system were simulated by nume rical solution of all differential equations necessary for the description of the hydrodynamic problem (computer code Fluent). The molar deposition ra te, r(dep), was described by a Langmuir-Hinshelwood type formula r(dep) = k (r)Kc/(1 + Kc), in which k(r) [mol m(-2) s(-1)] = 4.66 x 10(9) exp(-E-a(1)/ (RT)), E-a(1) = 299 kJ mol(-1); K [m(3) mol(-1)] = 2.22 x 10(-3) exp(E-a(2) /(RT)), E-a(2) = 130.2 kJ mol(-1) The evaporation rate of the precursor was also simulated. The experiments were carried out in the deposition range: total pressure p = 250-1000 Pa, deposition temperature T-dep = 1050-1233 K, concentration of the precursor c = 10(-4)-10(-3) mol m(-3). The deposition on fabrics was carried out in a tube reactor under similar deposition cond itions. The deposition was simulated with the data obtained in the microbal ance system. Characteristic numbers are derived where. in the case of the L angmuir-Hinshelwood formula. a constant deposition rate can be reached.