A three-step synthesis process of submicron boron carbide powders using microwave energy

Abstract

In this study, a three-step synthesis process is proposed for the production of submicron B4C powders. The initial step is the mechanical activation of a Mg–C–B2O3 mixture, which is carried out by using a high-energy planetary ball mill. The second phase is the microwave-assisted combustion synthesis, used to fabricate the MgO–B4C composite powders. The final stage is an acid leaching for removing the MgO phase. The results of DSC, XRD, and SEM analyses indicated that mechanical activation was a vital process for microwave synthesis and that no starting powders were remained unreacted after microwave heating. A considerable reduction in reaction temperature was obtained from DSC analysis after mechanical activation process. TG results indicated that separated milling of Mg with B2O3 powders would avoid the formation of gases during exothermic reactions. Finally, it was found that submicron boron carbide powders with an average crystallite size about 114 nm were produced with a high purity after acid leaching.