Structural and Compositional Evolution of Polymer-Derived SiHfCN and Ti3C2-SiHfCN Ceramics

In this study, SiHfCN ceramics were synthesized from a single-source precursor obtained by reacting Durazane 1800 with tetrakis(dimethylamido)hafnium(IV) (TDMAH). In a separate preparation, Ti3C2 MXene was incorporated into this precursor to produce MXene-SiHfCN composite ceramics. The samples were pyrolyzed at 1000 °C and heat-treated at 1600 °C in N2 to investigate amorphous-to-crystalline transformations. Both SiHfCN and MXene-SiHfCN formed a single-phase amorphous structure after pyrolysis at 1000 °C. At 1600 °C, SiHfCN partially crystallized into α/β-Si3N4 and HfCxN1−x phases within an amorphous/crystalline Si3N4 matrix. In contrast, the MXene–SiHfCN matrix remained largely amorphous, evolving into SiOCN with localized Si2ON2 crystallization. Additional phases, including HfCxN1−x, Hf oxide/oxycarbide, and a Ti carbonitride-rich phase (TiC0.63N1.06O0.18Si0.99Hf0.11), were identified within the amorphous SiOCN. No SiC was detected in either system, indicating suppression of carbothermal reduction of Si3N4 up to 1600 °C in N2. While SiHfCN exhibited pronounced macroscopic cracks, MXene-SiHfCN showed no such large cracks, though local microscopic cracking was observed. These results demonstrate that Ti3C2 MXene incorporation stabilizes the amorphous matrix, modifies phase evolution, and mitigates severe cracking, offering new insights into non-oxide PDC nanocomposites for ultra-high-temperature applications.