High-Entropy Diborides-Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study

The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS-SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf Mo Ti Ta Nb )B -SiC and (Hf Mo Ti Ta Zr )B -SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content