On the effects of hot spot formation during MW-assisted synthesis of Cf/SiC composites by reactive melt infiltration: Experimental simulations through high temperature treatments

Synthesis of SiC-based composites using microwave(MW)-assisted reactive infiltration is a promising way to obtain these materials at lower costs due to a reduction in processing time and energy consumption. Hot spots are likely to form during this process due to the different dielectric properties of the various phases and the exothermic nature of the reaction between Si and C. To study these effects C-f/SiC composites were subjected to high-temperature treatments (1800, 2000, 2200 degrees C) to simulate hot spots within the material. Microstructural changes were evaluated after the thermal treatments and thermo-mechanical properties were measured and correlated to the microstructural changes. Our results indicate that evaporation of silicon is the primary damaging mechanism, causing a decrease in the bending strength of the composite due to formation of porosity and a volume increase. These effects are countered by the densification of carbon phases that improve the intrinsic thermal properties of the material.