Synthesis and microstructure of binary (Zr_0.5Hf_0.5)C nanoparticles via stepwise thermo-carburization and carbothermal reduction processes

A novel strategy for synthesizing (Zr_0.5Hf_0.5)C nano-powders was proposed, and their synthesis behavior was investigated by varying the processing temperatures and durations. The (Zr_0.5Hf_0.5)C nanoparticles were prepared from a mixture of zirconium hydride (ZrH₂), hafnium oxide (HfO₂), and activated charcoal using a pressure-free spark plasma sintering system. The synthesis behaviors for stepwise thermo-carburization, carbothermal reduction, and solid solution processes were examined using a thermogravimetric differential thermal analysis (TG-DTA) with the derivative DTA method. The (Zr_0.5Hf_0.5)C powder exhibits significant particle refinement behavior, resulting in a more homogeneous size distribution without necking compared to the individual single-component mono-carbides. Furthermore, the compositional homogeneity and structural characteristics were elucidated by Raman and TEM analyses. Consequently, (Zr_0.5Hf_0.5)C powder with a size of 150 ± 34 nm and a low oxygen content of 0.437 ± 0.126 wt% was successfully synthesized at 1600 °C for 60 min.