Molecular design towards multicomponent C/C-Si(Ti,Zr,Hf,Ta)CN composites with simultaneously enhanced mechanical properties and air-plasma ablation performance

Novel multicomponent C/C-Si(Ti,Zr,Hf,Ta)CN composites were prepared through the polymer infiltration and pyrolysis process utilizing molecularly designed single-source precursors with controlled metal stoichiometries. By introducing Si(Ti,Zr,Hf,Ta)CN phase and designing its transition metal ratios, we achieved remarkable improvements in both mechanical properties and ablation resistance. The Zr/Hf-enriched composite (C/C-ST1Z3H5Ta1CN) with Ti:Zr:Hf:Ta= 1:3:5:1 exhibits exceptional flexural strength 252 ± 10 MPa) and minimal linear ablation rate (0.002 mm/s) under air-plasma testing at ∼2100 °C. Microstructural analysis shows the amorphous Si(Ti,Zr,Hf,Ta)CN matrix forms dense structures with strong interfacial bonding to carbon layers, enabling efficient stress transfer. Under ablation, the material develops a protective oxide layer with: (1) a refractory (Hf,Zr)O₂ framework as the structural skeleton, and (2) an oxidation-induced (Ti,Zr,Hf)Ta₂O₇/SiO₂ phase filling the interstices, which collectively inhibit oxygen penetration. Precursor design ensures homogeneous element distribution, preventing metal agglomeration. This study establishes that precise compositional control in polymer-derived ceramics synergistically enhances both mechanical strength and ablation resistance.