IGNITION CRITERIA FOR SELF-PROPAGATING COMBUSTION SYNTHESIS

Ignition criteria for gasless self-propagating combustion synthesis ha ve been investigated through an ignition temperature analysis. The cal culations were based on the dimensionless energy and mass continuity e quations where the dimensionless parameters associated with the rate o f local heat generation (beta), activation energy (gamma), the rate of surface heat loss by convection (omega), the rate of surface heat los s by radiation (delta), and the rate of reaction (A) were incorporated . The relative significance of each of these parameters on the ignitio n of the self-propagating combustion reaction was evaluated to be gamm a > beta > delta > omega. The ignition region, transition region, and nonignition region were identified for selected conditions. The correl ations between ignition behavior and the material properties, the ther modynamic and kinetic properties, as well as the experimental conditio ns 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-propagatin g combustion reaction without external energy input. Thus, this value can be used as an approximate guide for the existence of self-sustaini ng combustion. The calculations provide a sound basis toward interpret ing experimental observations and developing a fundamental understandi ng of the process.