Preparation of B₄C–SiC–HfB₂ nanocomposite by mechanically activated combustion synthesis

The B₄C–SiC–HfB₂ nanocomposite was synthesized by mechanically activated self-propagating high-temperature synthesis. The starting materials, including B₂O₃, HfO₂, Mg, Si and C, were mixed to form the composite with 1:1:1 and 5:4:1 molar ratio. The powders were synthesized in the tubular furnace at 900 °C and the spark plasma sintering (SPS) furnace at 575 °C. The XRD pattern of the synthesized sample according to form the composite with 1:1:1 molar ratio showed the presence of HfB₂, MgO and HfO₂. The phase and microstructural analyses verified that the leached sample contained SiC, HfB₂ and HfO₂. Thus, the B₄C could not be successfully synthesized when the 1:1:1 M ratio was chosen. However, the B₄C–SiC–HfB₂ composite was successfully synthesized by choosing the 5:4:1 molar ratio with a combustion reaction after optimizing activation energy to 6h. The B₄C–SiC–HfB₂ nanocomposite could also be formed by SPS at 575 °C, but some graphite remained in the system.