IGNITION CRITERIA FOR SELF-PROPAGATING COMBUSTION SYNTHESIS

Ignition criteria for gasless self-propagating combustion synthesis have been investigated through an ignition temperature analysis. The calculations were based on the dimensionless energy and mass continuity equations where the dimensionless parameters associated with the rate of local heat generation (beta), activation energy (gamma), the rate of surface heat loss by convection (omega), the rate of surface heat loss by radiation (delta), and the rate of reaction (A) were incorporated. The relative significance of each of these parameters on the ignition of the self-propagating combustion reaction was evaluated to be gamma > beta > delta > omega. The ignition region, transition region, and nonignition region were identified for selected conditions. The correlations between ignition behavior and the material properties, the thermodynamic and kinetic properties, as well as the experimental conditions were discussed. The calculations indicated that only those systems with DELTAH/C(p) > 1.5 X 10(3) (K) will give rise to a self-propagating combustion reaction without external energy input. Thus, this value can be used as an approximate guide for the existence of self-sustaining combustion. The calculations provide a sound basis toward interpreting experimental observations and developing a fundamental understanding of the process.