Experimental studies on self-propagating high-temperature synthesis of Si-SiC composite from reactants of SiO2 derived from corn cob ash/C/Mg

This work was an experimental study of the self propagating high-temperature synthesis (SHS) of Si-SiC composite using reactant powders of SiO2 derived from corn cob ash (CCA), elemental carbon, and elemental magnesium in the molar ratios 2:1:4, respectively. The in-situ SHS reaction was carried out under a static argon environment using an ignition source of Fe2O3: Al ignited by a tungsten-wire heated by electric current. The thermodynamic and formation reaction mechanisms to the final Si-SiC composite were investigated. The synthesized product powders were leached in two steps with HCl:CH3COOH and HF:H2O solutions, respectively. The microstructure and chemical composition of all product powders, both (as synthesized and as leached) were characterized using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and an X-ray diffractometer (XRD). The XRD analysis results of the leached product powders clearly showed the formation of Si and SiC phases. SEM observation revealed the agglomerated morphology of the SiSiC composite powders. All these results suggested that CCA would be a promising low-cost silica source for the synthesis of Si-SiC composite.