Preparation and characterization of ZrB2-SiC composite powders from zircon via microwave-assisted boro/carbothermal reduction

ZrB2-SiC composite powders were successfully synthesized via microwave-assisted boro/carbothermal reduction technique using zircon (ZrSiO4), activated carbon (C) and boron oxide (B2O3) as raw materials. They were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). Thermodynamic analysis on the synthesis process was carried out, and the effects of SiC bedding powder, reaction temperature, soaking time and n(B2O3):n(ZrSiO4) molar ratio on the formation of ZrB2-SiC composite powders were examined. The results showed that phase pure ZrB2-SiC composite powders were successfully synthesized at 1573 K which was 200 K lower than that required by using the conventional boro/carbothermal reduction method. In the final composite powders, fibrous SiC phases with 0.1-0.5 mu m in diameter and 1.4-4.2 mu m in length were homogeneously distributed among spherical ZrB2 particles with the average size of 0.1-1 mu m. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.