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 degrees C and the spark plasma sintering (SPS) furnace at 575 degrees 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 degrees C, but some graphite remained in the system.