The effect of degassing modes on the self-propagating reactions for the SiO2-Al-C system in the presence of reaction promoters

The combustion synthesis process activated by organic polymers (Teflon and polystyrene) in the SiO2/Al/C system is investigated under the counter-current and co-current degassing conditions. It is found that the combustion parameters, i.e. wave velocity and temperature, and final product microstructure are influenced by the degassing mode considered as well as the type and amount of promoters added to the starting mixture. In particular, the combustion wave results to accelerate during its propagation when adopting the forward infiltration configuration and in absence of polystyrene. In addition, under the same degassing condition, the produced gases are found to provide a specific orientation on the growth direction of thread-like SiC crystals during final product formation. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.