Dependence of the combustion reaction behavior and product on the B4C particle size in the Al-Ti-B4C and Al-TiO2-B4C Systems Was investigated. The results show that in both systems, the SHS reaction kinetics is primarily controlled by diffusion. Increasing the B4C particle size not only makes the ignition and self-sustainment of the SHS reaction difficult but also decreases the wave velocity and the degree of conversion. In comparison, the dependence of the SHS reaction behavior and the resultant product on the B4C particle size is much more significant in the Al-Ti-B4C system than that in the Al-TiO2-B4C system. The reason for the different dependence behaviors was investigated based on the SHS reaction mechanisms. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.