反应熔渗法制备Hf-Si基涂层-基体一体化改性C/C复合材料的微观结构及烧蚀性能OA

To enhance the ablation resistance of C/C composites under ultra-high-temperature and long-duration conditions,a non-embedded reactive melt infiltration technique was employed to fabricate a Hf-Si-based coating-matrix integrated modified C/C composite.Microstructural analysis revealed that the coating and matrix primarily consist of HfC,SiC,and HfSi2,with strong interfacial bonding formed between them through chemical reactions.Within the materials,the matrix density and composition exhibited a gradient distribution along the infiltration direction.Specifically,regions proximal to the infiltration source were denser and rich in HfC-HfSi2 phases,whereas distal regions were more porous,with the matrix consisting mainly of SiC and Si-HfSi2 eutectic structure.The surface coating was continuous and dense,with a uniform thickness of approximately 120 µm.It featured a distinct bilayer architecture composed of an outer SiC layer and an inner HfC-HfSi2-SiC layer.An in-depth investigation of the reaction mechanism revealed that the HfC-SiC-HfSi2 coating-matrix integrated structure formed through a synergistic effect of melt infiltration-reaction and vapor permeation-deposition.The composite exhibited exceptional ablation resistance when exposed to an oxyacetylene flame.After ablation tests conducted at 2500℃for 60,180,600,and 3540 s,the linear ablation rates were-3.52,-1.35,-0.85,and 0.118 μm/s,respectively.This outstanding performance is attributed to the in-situ formation of a dual-layer oxide barrier.A dense,continuous HfO2 layer generated from the surface coating works in concert with a multiphase HfO2-SiO2-HfSiO4 oxide layer generated from substrate oxidation.Together,these layers effectively retard inward oxygen diffusion and suppress the oxidative ablation process.This work proposes a viable strategy for designing and fabricating high-performance integrated thermal protection structures.