INFLUENCE OF REACTION MIXTURE POROSITY ON THE EFFECTIVE KINETICS OF GASLESS COMBUSTION SYNTHESIS

The effective activation energies for the self-propagating high-temper ature synthesis of Ti5Si3 were determined for samples with porosities ranging from 30% to 62%. A low-activation-energy regime was found for highly porous samples, while relatively high effective activation ener gies of 200-250 kJ/mol were measured far samples with porosity less th an 50%. The same effect was also observed in two other systems, involv ing syntheses of TiC and MoSi2. The limiting role of interparticle hea t transfer in propagation of the combustion front for highly porous sa mples is suggested as a possible explanation for the observed phenomen on.