Polymer-derived HfSiCO monolithic ceramics and fibers using Starfire’s SHP-199

The introduction of the first commercially available polycarbohafnium precursor opened new pathways in the polymer-to-ceramic route towards ultra-high temperature ceramics. We present a straightforward chemical crosslinking method to produce HfSiCO ceramics by reacting SHP-199 with tetraethoxysilane (TEOS), catalyzed by the intrinsic acidity of SHP-199. This sol-gel–like process produces robust HfSiCO monoliths and fibers with a 92% ceramic yield, excellent thermal stability, and structural integrity up to 1600 °C. While pyrolyzing SHP-199 alone results in nearly pure HfC, the SHP-199/TEOS mixture investigated here forms a multiphase ceramic containing HfO ₂ , SiO ₂ , and HfSiO ₄ , but no SiC or HfC. Strong Raman signals of carbon at 1600 °C suggest kinetically hindered reduction of the oxide. This work demonstrates the development of a synergistic Hf-Si network and provides an accessible pathway to high-temperature HfSiCO ceramics and fibers.