Experimental Study of Combustion Synthesis in Air of ZrB2-Mullite Composite from Different Zirconium Silicate Sources

Abstract

ZrB₂-mullite composite was synthesized by combustion synthesis (CS) from two different reactant systems: commercial ZrSiO₄-B₂O₃-Al, and zircon sand (mineral tailing)-B₂O₃-Al. The reactant mixture was activated by high-energy ball milling for 2 hours. The reaction was carried out under an air atmosphere and initiated with an oxy-acetylene flame. The standard Gibbs energy minimization method was used to calculate the equilibrium composition of the reacting species. The effects of different starting materials on the resulting combustion products were investigated and discussed. The as-synthesized products were characterized by X-Ray diffraction (XRD) and scanning electron microscope (SEM) coupled with energy dispersive X-Ray (EDS) detector. Examination of the self-propagated velocity showed that the reactivity was marginally higher when using commercial ZrSiO₄. The results also showed that both reactant systems successfully produced ZrB₂-mullite composite by the combustion reaction but that the commercial ZrSiO₄-B₂O₃-Al reactants system exhibited fewer undesirable phases than zircon sand-B₂O₃-Al due to a better conversion of the reactants into combustion products.