SiCnw/PyC core-shell networks to improve the bonding strength and oxyacetylene ablation resistance of ZrB2-ZrC coating for C/C-ZrB2-ZrC-SiC composites

To enhance the bonding strength and oxyacetylene ablation resistance of the ZrB2-ZrC coated C/C-ZrB2-ZrC-SiC composites obtained by the combination of supersonic atmosphere plasma spray (SAPS) and precursor infiltration and pyrolysis (PIP), novel SiC nanowire (SiCnw)/pyrolytic carbon (PyC) core-shell structures are designed and introduced into the coating. Compared to SiC nanowires which are widely added into ceramics, metals and so on, SiCnw/PyC core-shell structures have a better cohesion. Additionally, the bonding strength of coating can be largely improved through the toughening mechanism of SiCnw/PyC structures. After being exposed to oxyacetylene ablation torch, the best ZrB2-ZrC coated C/C-ZrB2-ZrC-SiC specimens with SiCnw/PyC networks possess a linear ablation rate of −0.9 ± 0.5 μm/s and a mass ablation rate of −0.3 ± 0.6 mg/s, while the linear and mass ablation rates of the C/C-ZrB2-ZrC-SiC specimens for comparison are up to 4.2 ± 1.0 μm/s and 1.2 ± 0.8 mg/s, respectively. The significant improvement of oxyacetylene ablation resistance is attributed to a lower surface temperature during ablation, a lower thermal stress in the coating, and a better bonding strength of the coating/substrate interface owing to the introduction of SiCnw/PyC core-shell structures.

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