Influence of Zr-Si ratio on the RMI process and ablation behavior of C/C-SiC-ZrC composites

To address the demand for ablation-resistant materials suitable for applications in hypersonic vehicles operating in extreme environments, ultrahigh-temperature-ceramic–modified carbon/carbon composites (C/C-UHTCs) have emerged as a key research focus. In this study, we fabricate C/C-SiC-ZrC composites via reactive melt infiltration (RMI) and investigated the effects of different Si-Zr alloy compositions on the RMI mechanism and ablation behavior of the materials. Under identical conditions, an increase in the Zr concentration results in a decrease in the material density and a concomitant increase in the porosity. The elevated Zr concentration in the alloy modifies the element-diffusion mechanism during RMI, thus affecting the overall RMI process. Ablation experiments reveal that the samples fabricated with ZrSi₂ and ZrSi via RMI exhibit similar ablation rates, which are significantly lower than that of the sample prepared with Zr₂Si. This divergence stems from the formation of relatively uniform and dense ceramic layers on the surfaces of the samples obtained by the RMI of ZrSi₂ and ZrSi, which provide protection during ablation. This study provides both theoretical and experimental backing for the fabrication and process optimization of C/C-ZrC-SiC composites prepared via RMI.