Microstructure and Ablation Resistance of C/C Composites Modified by Hf-Si-based Coating-matrix Integrated Structure Fabricated by Reactive Melt Infiltration

doi:10.15541/jim20250424

Abstract

Abstract:

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 an 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.

Key words: reactive melt infiltration, ultra-high temperature ceramic, coating-matrix integration, microstructure, ablation resistance

CLC Number:

TB332

ZHAO Tongtong, DAI Jixiang, SU Cheng, SHI Yan, SHA Jianjun. Microstructure and Ablation Resistance of C/C Composites Modified by Hf-Si-based Coating-matrix Integrated Structure Fabricated by Reactive Melt Infiltration[J]. Journal of Inorganic Materials, 2026, 41(5): 583-594.

Figures/Tables 15

Fig. 1 (a, c) Macroscopic photographs of the upper surface and cross-section of CHS; (b, d) XRD patterns of the coating and substrate

Fig. 2 XRM image slices of CHS (a) XZ plane; (b, c) YZ plane

Fig. 3 3D XRM image (a) and typical 2D image slices (b) of CHS processed using deep learning, along with the variation curves of ceramic matrix and residual pore content with penetration depth (c) Colorful figures are available on website

Fig. 4 Microstructure and EDS results of the CHS internal matrix (a-c) Lower end region; (d-f) Upper end region

Fig. 5 Microstructure and EDS results of the top surface coating on CHS (a-c) Coating surface; (d-f) Coating cross-section

Fig. 6 Formation mechanism diagram of HfC-SiC-HfSi2 coating-matrix integrated modified C/C composites

Fig. 7 Gibbs free energy changes as a function of temperature for the Hf-C and Si-C reactions

Fig. 8 (a) Temperature curves at the ablation center of the samples; (b) Mass and linear ablation rates; (c) Surface morphologies of the samples after ablation

Fig. 9 XRD patterns of the ablated samples surface (a) and enlarged patterns in the range of 2θ=26°-34° (b)

Fig. 10 Micro-morphologies of the center and edge regions of the ablated samples surface (a-c) CHS-60; (d-f) CHS-180; (g-i) CHS-600

Fig. 11 Micro-morphologies and EDS elemental mappings of the cross-section at the ablation center of the samples (a, a1) CHS-60; (b, b1) CHS-180; (c, c1) CHS-600

Fig. 12 Temperature curve at the ablation center of CHS-3540 and state diagrams of the sample and graphite fixture during (a) and after (b) ablation

Fig. 13 XRD pattern of the CHS-3540 ablation surface

Fig. 14 Macroscopic morphology (a) and microstructures (b-g) of CHS-3540 after ablation (b) Transition region; (c) Edge region; (d-f) HfO2 layer at ablation center; (g) Cross-section

Fig. 15 Comparison of line ablation rates between this work and related literature[18,20,22 -23,25 -26,34 -44] Colorful figure is available on website

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