Fabrication of Gradient Structured (Ta_0.2Nb_0.2Ti_0.2Zr_0.2Hf_0.2)C-SiC Composites and Their High-Temperature Ablation Behavior

Abstract

Porous high-entropy carbide ceramics (PHECs) exhibit excellent high-temperature stability and are considered promising candidates for thermal-protection applications. However, their interconnected pore structure facilitates oxygen ingress during ablation, resulting in accelerated oxidation and structural degradation. In this work, a gradient SiC-rich dense surface layer was constructed on porous (Ta_0.2Nb_0.2Ti_0.2Zr_0.2Hf_0.2)C ceramics through phenolic-resin infiltration, carbonization, and reactive melt infiltration (RMI) of silicon. The resulting composites exhibited a hierarchical architecture consisting of a dense SiC-rich surface layer and a porous interior. The initial pore structure strongly influenced molten-Si infiltration and reaction behavior, leading to an increase in the thickness of the SiC-rich dense layer from 33.3 to 121.2 μm with increasing porosity. During ablation, oxidation of SiC generated SiO₂, which interacted with refractory transition-metal oxides to form a SiO₂-rich composite oxide layer that effectively suppressed oxygen diffusion and enhanced oxidation resistance. Consequently, the oxide-layer thickness decreased from 121.4 to 35.2 μm, accompanied by a significant reduction in the mass ablation rate. Among all samples, HEC-SiC5 exhibited the best ablation resistance, with a mass ablation rate as low as 0.23 mg/s. This work establishes a direct correlation between substrate pore architecture, molten-Si infiltration behavior, dense-layer evolution, and ablation resistance, providing a practical strategy for the design of lightweight porous HEC-based thermal-protection materials.

Keywords

(TaNbTiZrHf)C / SiC-rich gradient layer / Reactive melt infiltration / Ablation resistance

Author Contributions

Writing-Original Draft Preparation, X.W.;Writing-Review&Editing, C.L., H.O.; Conceptualization, X.W., C.L., H.O., Q.Y., T.S.; Validation, C.L., H.O., Q.Y., T.S.; Investigation, X.W., Q.Y.; Supervision, C.L., H.O., T.S.; Funding Acquisition, C.L., H.O.; Methodology, X.W.,Q.Y., T.S.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be made available on request.

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 52173299, 52372087), Natural Science Foundation of Shaanxi Province (Grant No. 2025SYS-SYSZD-062).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

[1] Ding Y, Yue X, Chen G, Si J. Review of control and guidance technology on hypersonic vehicle. Chin. J. Aeronaut. 2022, 35, 1-18. DOI: 10.1016/j.cja.2021.10.037

[2] Sziroczak D, Smith H. A review of design issues specific to hypersonic flight vehicles. Prog. Aerosp. Sci. 2016, 84, 1-28. DOI: 10.1016/j.paerosci.2016.04.001

[3] Uyanna O, Najafi H. Thermal protection systems for space vehicles: A review on technology development, current challenges and future prospects. Acta Astronaut. 2020, 176, 341-356. DOI: 10.1016/j.actaastro.2020.06.047

[4] Zhang Y, Liu B, Zhang X, Liu H, Wang X, Zhang Y, et al. Advanced characterization techniques and protective mechanism investigation methodologies for ultra-high temperature thermal protective materials. Prog. Mater. Sci. 2027, 164, 101788. DOI: 10.1016/j.pmatsci.2026.101788

[5] Guria J, Bansal A, Kumar V. Effect of additives on the thermal conductivity of zirconium diboride based composites-A review. J. Eur. Ceram. Soc. 2021, 41, 1-23. DOI: 10.1016/j.jeurceramsoc.2020.08.051

[6] Shen T, Li C, Ouyang H, Wang J, Bao L, Wu S, et al. Enhancing the ablation resistance of C/C-HfC-ZrC-SiC composites via a molten-salt-deposited TiC coating. Ceram. Int. 2026, 52, 14346-14357. DOI: 10.1016/j.ceramint.2026.02.072

[7] Serrano NL, Ruiz L, Doolittle CT, Burk D, Ghoshal A, Walck S, et al. Properties and high-temperature ablation behavior of pressureless sintered HfC-SiC-TaC ceramics. J. Am. Ceram. Soc. 2025, 109, 70357. DOI: 10.1111/jace.70357

[8] Mishra R, Singh V, Patel M, Mitra R. Thermal shock resistance and long-term ablation behaviour of the Cf-ZrB₂-SiC UHTCMCs fabricated via slurry infiltration and hot pressing. J. Eur. Ceram. Soc. 2026, 46, 118650. DOI: 10.1016/j.jeurceramsoc.2026.118650

[9] Zeng Y, Wang D, Xiong X, Zhang X, Withers P, Sun W, et al. Ablation-resistant carbide Zr_0.8Ti_0.2C_0.74B_0.26 for oxidizing environments up to 3000 °C. Nat. Commun. 2017, 8, 15836. DOI: 10.1038/ncomms15836

[10] Ni D, Cheng Y, Zhang J, Liu J, Zou J, Chen B, et al. Advances in ultra-high temperature ceramics, composites, and coatings. J. Adv. Ceram. 2022, 11, 1-56. DOI: 10.1007/s40145-021-0550-6

[11] Li K, Guo L, Wang J, Chen H, Li Y, Zhang R. Synergistic enhancement of strength and ablation resistance in HEC ceramics by SiC and short carbon fiber reinforcement. Surf. Interf. 2026, 86, 108714. DOI: 10.1016/j.surfin.2026.108714

[12] Sengupta P, Manna I. Advanced High-Temperature Structural Materials for Aerospace and Power Sectors: A Critical Review. Trans. Indian Inst. Met. 2019, 72, 2043-2059. DOI: 10.1007/s12666-019-01598-z

[13] Zhang X, Guo L, Liu H, Zhang Y, Fu Q, Yin X, et al. Advanced anti-ablation C/C composites: structural design strategies and future perspective. Mater. Today. 2024, 80, 710-736. DOI: 10.1016/j.mattod.2024.09.004

[14] Wang Y, Csanadi T, Zhang H, Dusza J, Reece M, Zhang R. Enhanced hardness in high-entropy carbides through atomic randomness. Adv. Theory. Simul. 2020, 3, 2000111. DOI: 10.1002/adts.202000111

[15] Castle E, Csanádi T, Grasso S, Dusza J, Reece M. Processing and properties of high-entropy ultra-high temperature carbides. Sci. Rep. 2018, 8, 8609. DOI: 10.1038/s41598-018-26827-1

[16] He H, Yang J, Guo W, Zhang S, Bai S. Microstructures and formation mechanism of continuous carbon fiber-reinforced (TiZrHfNbTa)C high-entropy ceramic composites fabricated via high-entropy alloy reactive melt infiltration. Ceram. Int. 2023, 49, 36997-37008. DOI: 10.1016/j.ceramint.2023.09.032

[17] Harrington T, Gild J, Sarker P, Toher C, Rost C, Dippo O, et al. Phase stability and mechanical properties of novel high entropy transition metal carbides. Acta Mater. 2019, 166, 271-280. DOI: 10.1016/j.actamat.2018.12.054

[18] Shen T, Li C, Ouyang H, He M, Wu S, Liu J, et al. Tailoring of PyC/TiC interface for Cf/(TiZrHfNbTa)C-SiC composites with enhanced mechanical performance and durability in extreme environments. J. Mater. Sci. Technol. 2026, 270, 267-278. DOI: 10.1016/j.jmst.2026.01.046

[19] Demirskyi D, Borodianska H, Suzuki T, Sakka Y, Yoshimi K, Vasylkiv O. High-temperature flexural strength performance of ternary high-entropy carbide consolidated via spark plasma sintering of TaC, ZrC and NbC. Scr. Mater. 2019, 164, 12-16. DOI: 10.1016/j.scriptamat.2019.01.024

[20] Zhou J, Zhang J, Zhang F, Niu B, Lei L, Wang W. High-entropy carbide: a novel class of multicomponent ceramics. Ceram. Int. 2018, 44, 22014-22018. DOI: 10.1016/j.ceramint.2018.08.100

[21] Wang Y, Reece M. Oxidation resistance of (Hf-Ta-Zr-Nb)C high entropy carbide powders compared with the component monocarbides and binary carbide powders. Scr. Mater. 2021, 193, 86-90. DOI: 10.1016/j.scriptamat.2020.10.038

[22] Ni N, Ding Q, Shi Y, Jiang J, Li L, Zhang R, et al. Ablation behavior of high-entropy carbides ceramics (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C upon exposition to an oxyacetylene torch at 2000 °C. J. Eur. Ceram. Soc. 2023, 43, 2306-2319. DOI: 10.1016/j.jeurceramsoc.2023.01.017

[23] Ye B, Wen T, Chu Y. High-temperature oxidation behavior of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high-entropy ceramics in air. J. Am. Ceram. Soc. 2020, 103, 500-507. DOI: 10.1111/jace.16725

[24] Peng Z, Sun W, Xiong X, Zhang H, Guo F, Li J. Novel refractory high-entropy ceramics: Transition metal carbonitrides with superior ablation resistance. Corros. Sci. 2021, 184, 109359. DOI: 10.1016/j.corsci.2021.109359

[25] Jin X, Fan X, Lu C, Wang T. Advances in oxidation and ablation resistance of high and ultra-high temperature ceramics modified or coated carbon/carbon composites. J. Eur. Ceram. Soc. 2018, 38, 1-28. DOI: 10.1016/j.jeurceramsoc.2017.08.013

[26] Zhang B, Yin J, Zheng J, Liu X, Huang Z, Dusza J, et al. High temperature ablation behavior of pressureless sintered Ta_0.8Hf_0.2C-based ultra-high temperature ceramics. J. Eur. Ceram. Soc. 2020, 40, 1784-1789. DOI: 10.1016/j.jeurceramsoc.2019.11.043

[27] Liu T, Niu Y, Li C, Pan X, Shi M, Zheng X, et al. Ablation resistance of ZrC-MoSi₂/ZrC-SiC double-layered coating in a plasma flame. Corros. Sci. 2018, 145, 239-248. DOI: 10.1016/j.corsci.2018.10.006

[28] Zhang X, Sun Y, Guo L, Liu H, Liu T, Fu Q, et al. Bioinspired vacuum-driven approach enables mechanically robust, ablation-resistant sharp leading-edge composites. Mater. Today 2026, 92, 126-139. DOI: 10.1016/j.mattod.2025.11.031

[29] Shen T, Li C, Ouyang H, He M, Wu S, Bao L, et al. A mortise-tenon joint inspired interface structure design for synergistically enhancing the mechanical properties and thermal shock resistance of Cf/(HfNbTaTiZr)C-SiC composites. J. Adv. Ceram. 2026, 15, 9221227. DOI: 10.26599/jac.2025.9221227

[30] Li W, Cui C, Bao J, Zhang G, Li S, Wang G. Properties regulation of SiC ceramics prepared via stereolithography combined with reactive melt infiltration techniques. Ceram. Int. 2021, 47, 33997-34004. DOI: 10.1016/j.ceramint.2021.08.307

[31] Makurunje P, Sigalas I, Binner J. Scale characterisation of an oxidised (Hf, Ti)C-SiC ultra-high temperature ceramic matrix composite. J. Eur. Ceram. Soc. 2021, 41, 167-175. DOI: 10.1016/j.jeurceramsoc.2020.08.048

[32] Cai F, Ni D, Chen B, Ye L, Sun Y, Lu J, et al. Fabrication and properties of Cf/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C-SiC high-entropy ceramic matrix composites via precursor infiltration and pyrolysis. J. Eur. Ceram. Soc. 2021, 41, 5863-5871. DOI: 10.1016/j.jeurceramsoc.2021.05.026

[33] Liu R, Yang L, Miao H, Jiang M, Wang Y, Liu X, et al. Influence of the SiC matrix introduction time on the microstructure and mechanical properties of Cf/Hf_0.5Zr_0.5C-SiC ultra-high temperature composites. Ceram. Int. 2022, 48, 3762-3770. DOI: 10.1016/j.ceramint.2021.10.159

[34] Zhang Y, Wang X, Liu B, Zhang M, Fu Q, Yin X, et al. Bioinspired C/C composites with long-duration ablation resistance for thermal protection up to 2400 °C. Mater. Sci. Eng. R Rep. 2026, 168, 101157. DOI: 10.1016/j.mser.2025.101157

[35] Williams P, Sakidja R, Perepezko J, Ritt P. Oxidation of ZrB₂-SiC ultra-hightemperature composites over a wide range of SiC content. J. Eur. Ceram. Soc. 2012, 32, 3875-3883. DOI: 10.1016/j.jeurceramsoc.2012.05.021

[36] Shen T, Li C, Ouyang H, He M, Wu S, Wang L, et al. High-entropy (Ta_0.2Nb_0.2Ti_0.2Hf_0.2Zr_0.2)C-SiC Ceramics: Achieving Superior Ablation Resistance through SiC Particle Size Optimization. J. Eur. Ceram. Soc. 2026, 46, 117800. DOI: 10.1016/j.jeurceramsoc.2025.117800

[37] Wang H, Cao Y, Liu W, Wang Y. Oxidation behavior of (HfTaZrTiNb)C-xSiC ceramics at high temperature. Ceram. Int. 2020, 46, 11160-11168. DOI: 10.1016/j.ceramint.2020.01.137

[38] Lu K, Liu J, Wei X, Bao W, Wu Y, Li F, et al. Microstructures and mechanical properties of high-entropy (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C ceramics with the addition of SiC secondary phase. J. Eur. Ceram. Soc. 2020, 40, 1839-1847. DOI: 10.1016/j.jeurceramsoc.2019.12.056

[39] Yang L, Dong S, Cui T, Xin J, Chen G, Hong C, et al. Novel gradient ZrB₂-MoSi₂-SiC dense layer with enhanced emissivity and long-term oxidation resistance at ultra-high temperatures. Rare Met. 2025, 44, 2043-2058. DOI: 10.1007/s12598-024-02959-4

[40] Zhao T, Dai J, Su C, Shi Y, Sha J. Microstructure and Ablation Resistance of C/C Composites Modified by Hf-Si-based Coating-matrix Integrated Structure Fabricated by Reactive Melt Infiltration. J. Inorg. Mater. 2026, 41, 583-594. DOI: 10.15541/jim20250424

[41] Yang Q, Li C, Ouyang H, Gao R, Shen T, Huang J. Dual-porosity (Ta_0.2Nb_0.2Ti_0.2Zr_0.2Hf_0.2)C high-entropy ceramics with high compressive strength and low thermal conductivity prepared by pressureless sintering. Materials 2023, 16, 2495. DOI: 10.3390/ma16062495