KINETIC-PARAMETERS FOR HETEROGENOUS BORON COMBUSTION REACTIONS VIA THE CLUSTER BEAM APPROACH

In the Cluster Beam method, singly ionized clusters of controlled size and composition are used as experimental ''models'' of macroscopic su rfaces. Within this framework, it is possible to predict product distr ibutions and kinetic parameters for elementary surface reactions over a wide range of temperatures and surface compositions. In some cases w e can also derive thermodynamic information relevant to elementary rea ction products and reaction intermediates. The fundamental assumptions , experimental methods, and data analysis techniques are described, an d estimates are given for the reliability of Cluster Beam predictions. Our predictions are compared with the single case where good surface reactivity data are available from more conventional experiments. The technique is illustrated with detailed results for boron oxide cluster ion reactions with HF, which are used to predict kinetics related to boron oxide layer removal in fluorine-containing propellants, fut ls, and explosives. Kinetic parameters and product distributions are then presented for elementary reactions of pure boron with a number of spec ies including oxidizers, hydrocarbons, CS2, D-2, BF3, and HF. While th ere are clearly varying degrees of uncertainty associated with our pre dictions, we believe that in the continued absence of surface chemistr y data, our results provide a valuable tool for refining our picture o f the elementary chemistry important in boron volatilization and combu stion.