Effect of initial composition on boron carbide production by SHS process followed by acid leaching

Abstract

Abstract In this study, iron-free boron carbide powders (B 4 C) were produced from the milled SHS (self-propagating high temperature synthesis) products followed by leaching in an aqueous hydrochloric acid (HCl) media. The SHS mixtures were composed of boron oxide (B 2 O 3 ), carbon black and magnesium. Thermochemical simulations were performed to estimate the effect of initial composition on the SHS process. In the SHS experiments, it was found that the formations of boron carbide and magnesium borates were directly related with B 2 O 3 and carbon black contents in the initial SHS mixture. The aqueous HCl leaching of the SHS products did not only eliminate the unwanted byproducts (i.e. MgO, Mg 3 B 2 O 6 and Mg 2 B 2 O 5 ) but also enhanced substantially the pore structure of the particles. Even though the leached SHS particles ( d 0.5 = 7.96 μm) were much coarser than that of the commercial powder ( d 0.5 = 1.73 μm), the surface area of the leached product (15.56 m 2 /g) was found to be larger than that of commercial one (4.92 m 2 /g).