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 μm in diameter and 1.4–4.2 μm in length were homogeneously distributed among spherical ZrB2 particles with the average size of 0.1–1 μm.