Preparation of HfC_xN_1-x Nanoparticles Derived from a Multifunction Precursor with Hf-O and Hf-N Bonds

HfC_xN_1-x nanoparticles were synthesized using the urea-glass route, employing hafnium chloride, urea, and methanol as raw materials. The synthesis process, polymer-to-ceramic conversion, microstructure, and phase evolution of HfC_xN_1-x/C nanoparticles were thoroughly investigated across a wide range of molar ratios between the nitrogen source and the hafnium source. Upon annealing at 1600 °C, all precursors demonstrated remarkable translatability to HfC_xN_1-x ceramics. Under high nitrogen source ratios, the precursor exhibited complete transformation into HfC_xN_1-x nanoparticles at 1200 °C, with no observed presence of oxidation phases. In comparison to HfO₂, the carbothermal reaction of HfN with C significantly reduced the preparation temperature required for HfC. By increasing the urea content in the precursor, the carbon content of the pyrolyzed products increased, leading to a substantial decrease in the electrical conductivity of HfC_xN_1-x/C nanoparticle powders. Notably, as the urea content in the precursor increased, a significant decrease in average electrical conductivity values was observed for the R4-1600, R8-1600, R12-1600, and R16-1600 nanoparticles measured at a pressure of 18 MPa, yielding values of 225.5, 59.1, 44.8, and 46.0 S·cm^-1, respectively.