Kinetic Studies of Boron and Aluminum Species

Abstract

We measured the temperature and pressure dependence of the rate constants of several key chemical reactions important in the combustion of boron and aluminum including: BO + O2, BO + H2, BH + D2, Al + CO2, and Al + O2. Elementary reaction rate constants are obtained in our high temperature reactor using laser pump-and-probe techniques. For several reactions, we monitor the products to confirm proposed reaction mechanisms. We find that the oxidation reactions of BO and Al are fast at combustion temperatures and proceed by O-atom transfer. The reactions of BO + O2 and Al + O2 proceed by complex formation followed by rapid decomposition of the complex. There are two product channels in the reaction of Al + CO2. Near room temperature complex formation dominates while above 750 K the dominant reaction is direct O-atom transfer. The reaction of BO + H2 proceeds by direct H-atom transfer while the reaction of BH + D2 involves complex formation. The experimental studies of the reactions BO + H2 and BH + D2 are combined with ab initio studies of the potential energy surface to provide further insight into the reaction mechanisms.