Experimental studies on self-propagating high-temperature synthesis of Si-SiC composite from reactants of SiO2derived 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 SiO2derived 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 Si-SiC composite powders. All these results suggested that CCA would be a promising low-cost silica source for the synthesis of Si-SiC composite.