Synthesis mechanism and microstructure characterization of ZrB2-ZrC-SiC nanocomposite synthesized via magnesium boro/carbothermal reduction at low temperatures

In this study, magnesium boro/carbothermal reduction of zirconium silicate (ZrSiO4) was employed to synthesize zirconium-based composite nanopowders of ZrB2-SiC, ZrB2-ZrC-SiC, ZrC-SiC, and ZrC. For this aim, three different temperatures of 1200 degrees C, 1300 degrees C, and 1450 degrees C were selected as the supposed temperatures for synthesis. Elemental Mg and NaCl were also selected to assist reduction process. In addition, effects of different C/Zr ratios as well as using elemental boron and B4C as two different boron sources were investigated on the final produced phases. Subsequently, XRD and SEM/EDS analyses were carried out to elaborate microstructure and phase studies. Finally, STA carried out up to 1500 degrees C to predict the most probable reactions. Despite the notion that no target phases were formed after 8 h of high energy milling under argon (Ar) atmosphere, SiC formation was observed from 1200 degrees C, though ZrC formation was postponed to 1450 degrees C. In all the three synthesis temperatures, ZrB2 formed in samples containing B4C and higher temperatures led to more formation of ZrB2 in the products. The main zirconium reduction mechanism was reduction through SiC in lower temperatures, where an excessive amount of carbon in the initial powder mixture contributed to the remaining SiC in samples after ZrC formation. Finally, the by-products were leached by stirring in hot 4.11 Molar HCl for 2 h.