Preparation and high-temperature performance of HfC-based nanocomposites derived from precursor with Hf-(O,N) bonds

A novel precursor was synthesized by reacting hafnium chloride with dicyandiamide and dimethylformamide. The precursor was characterized via FT-IR and NMR , as well as TG. Subsequently, the precursor was annealed in Ar over a range of temperatures from 1000   °C to 2000   °C, and the microstructural evolution of the ceramics was investigated by XRD , XPS , and TEM. The results show that the carbothermal reduction of the precursor starts at 1150   °C and the ceramic yields at 1500   °C reach 44.6   wt%. The obtained powders exhibit a uniform distribution and are composed of N-doped HfC and graphite. The N-doped structure postponed the oxidation of the HfC(N) ceramics. The HfC(N) ceramics were first oxidized to yield HfO 2 , carbon, and nitrogen, and then the carbon was oxidized with the evolution of CO 2 . The presented synthesis method is believed to be applicable to the preparation of other high-performance ceramics.