Synthesis of HfBCN single-source precursor and its spinning feasibility for deriving ultra-high temperature ceramic fibers

Hafnium (Hf)-containing polymers have garnered increasing attention as single-source precursors for ultrahigh-temperature ceramics (UHTCs), but it still remains significant challenges in regulating the highly active Hf atoms. Herein, we designed and synthesised a novel polymeric Hf-B-C-N precursor (PHBCN) by the dehalogenative substitution reactions using B(NHCH₃)₃, ClCH₂CN, and HfCl₄ as raw materials. A molecular collaborative strategy was described through the coordination effects of amidinate ligands and the conjugation effects of BN₃ aromatic systems to modulate the electronic environment of Hf centers and promote the water/oxygen resistance of PHBCN. The pyrolysis of PHBCN at 1600 °C produced HfC/HfB₂ nanocomposite ceramics with Hf content of 75.71 wt% and the phase evolution of polymer-derived ceramics was systematically investigated. Moreover, the hydrolytic-oxidative stability and proper rheological properties endowed PHBCN precursor with good spinnability, which would provide a new idea for advancing Hf-based UHTC fibers.