Decomposition of α-aluminum hydride power. 3. Simultaneous photolytic-thermal decomposition

The simultaneous effects of uv photolysis and thermal decomposition (coirradiation) on α-AlH3 powder have been investigated between 60 and 1500C. From the kinetic analysis, this temperature range can be divided into two distinct regimes; the first region from 60 to 1100C delineates a transition between the photolysis and coirradiation, and the second region from 110 to 1500C involves only coirradiation. The fractional decomposition (α) vs time curves are sigmoidal in shape between 110 and 1500C much like the thermal decomposition data at these temperatures. The transition-region curves change with temperature and/or light intensity to resemble either the low-temprature photolysis or the high-temperature coirradiation curves. The high-temperature coirradiation α(t) curves are faster and have induction, acceleratory, and decay periods similar to those for the thermal decomposition, but different kinetics are applicable with lower activation energies (kJ/mol): (51.1 vs 107.0, 130.1 vs 158.0, and 132.8 vs 164.0, respectively). In the transition region, an empirical relationship describes the induction period, but the acceleratory period has the same linear relationship with time as the high-temperature coirradiation. The synergistic effect of uv light and heat is evidenced in the lower activation energies and faster decomposition rates noted for reactions involving the additional uv light stimulus. The changing interaction of light- and heat-induced species and the complex behavior of the resultant kinetics is noted during the transition region. 4 figures, 4 tables