Investigating mechanochemical behavior of Cr2O3–B2O3–Mg–C quaternary system

Abstract

Fundamental aspects of reaction behavior and formation path in the Cr2O3–B2O3–Mg–C quaternary system have been studied to synthesize chromium boride–chromium carbide nanocomposite. In order to find the influence of simultaneous presence of magnesium and carbon on final products, various powder mixtures were chosen according to following reaction: B2O3+Cr2O3+(9− x) Mg+x C. The value of x varied from 0 to 4. In the absence of carbon (x=0), CrB2 was synthesize through mechanically induced self-propagating reaction (MSR). In the presence of 8molMg and 1mol C (x=1), the dominant boride phase was CrB while no chromium carbide was detected. By increasing C content (x=2), the magnesiothermic reduction occurred in MSR mode; whereas, the synthesis of Cr3C2 initiated after combustion reaction and completed gradually during milling for 6h. Further increase in C amount (x=3) resulted in formation of Mg3(BO3)2 as unwanted phases as well as CrB and Cr3C2. In the presence of 6molMg and 4mol (x=4), no mechanical reaction was observed even after 8h of milling. Optimum value of x for the formation of CrB–Cr3C2 nanocomposite was 2. Based on the morphological evolutions, it is evident that the mechanosynthesized powder is made up of nanometric particles.