The advancement of cutting-edge technologies, including hypersonic vehicles, aerospace transportation platforms, and fusion energy systems, is driving the transition in electromagnetic stealth requirements from room-temperature conditions to extreme environments. However, traditional wave-absorbing materials suffer severe performance degradation at temperatures above {500}^{\circ }\mathrm{C} or under corrosive and irradiated conditions. Owing to their unique thermodynamic stability and tunable multielement structures, high-entropy materials provide a promising route to address these challenges. This review systematically summarizes the electromagnetic-wave absorption behavior and structural evolution of high-entropy alloys, high-entropy ceramics, and high-entropy MAX/MXene materials under extreme conditions such as oxidation (550-1600℃), salt-spray exposure, cryogenic temperatures, and thermal shock. Particular emphasis is placed on elucidating the mechanisms enabling efficient electromagnetic dissipation, including composition design, microstructural engineering, and multi-mode coupling. Reported studies indicate that these materials can achieve reflection losses below -30 dB and effective bandwidths exceeding 10 GHz across a variety of systems while maintaining excellent environmental stability. Future research opportunities include machine-learning-assisted multi-objective optimization, scalable fabrication strategies, and the development of sustainable high-entropy absorber systems for practical deployment in extreme environments.

Improving the corrosion resistance of environmental barrier coatings (EBCs) to molten calcium-magnesium-aluminosilicate (CMAS) salt is an urgent requirement for aeroengine blades. In this work, a novel high-entropy (Ho_0.2Er_0.2Tm_0.2Yb_0.2Lu_0.2)₂Si₂O₇ ((5RE_0.2)₂Si₂O₇) environmental barrier coating material was developed, and molten CMAS corrosion resistance of (5RE_0.2)₂Si₂O₇) was systematically investigated at 1500 °C. The prepared (5RE_0.2)₂Si₂O₇ ceramic possesses a single and stable β-phase structure with high-temperature stability from room temperature to 1500 ℃. The thermal conductivity of (5RE_0.2)₂Si₂O₇ ranges from 1.46 to 3.49 W·m⁻¹·K^-1 at room temperature to 1500 ℃. A rapid reaction of (5RE_0.2)₂Si₂O₇ with molten CMAS produced Ca₂RE₈(SiO₄)₆O₂ apatite at 1500 ℃. The reaction layer thickness was only 95.9±8.6 μm which effectively inhibited the infiltration and diffusion of molten CMAS salt. In contrast, Yb₂Si₂O₇ ceramic, when exposed to molten CMAS at 1500 ℃, showed no reaction. Instead, the molten CMAS salt penetrated into the interior of Yb₂Si₂O₇ along grain boundaries and voids, forming bubble cracking and ultimately, structural degradation. These results suggest that the high-entropy (5RE_0.2)₂Si₂O₇ ceramic material is a potential candidate for next-generation EBC with excellent resistance to CMAS corrosion.

ZrB₂-20SiC (ZS20) composite and its derivatives doped with 5 vol% Sc₂O₃, Y₂O₃, and La₂O₃ were densified using hot press sintering to investigate the influence of rare earth oxides on their high temperature oxidation and ablation behavior. Isothermal oxidation testing at 1773 K indicate that rare earth oxides modification lowers activation energy and slightly accelerates weight gain during the initial phase. As oxidation progresses, the weight gain of ZS20 increases sharply. The sample doped with La₂O₃ (ZS20L5) exhibits the lowest oxidation weight gain, with a porosity of only 1.8% after oxidation. Cyclic ablation tests at the middle-low temperature zones indicate that ZS20L5 exhibits the lowest linear and mass ablation rates. Thermodynamic analyses demonstrate that La₂O₃ preferentially reacts with SiO₂ to form La₂Si₂O₇, which demonstrates a more effective oxygen barrier property compared to ZrSiO₄. Additionally, La₂O₃ enhances the fluidity of the glass phase, effectively filling cracks, sealing pores, and blocking the penetration of oxygen.

Thermal protection coatings for aerospace applications require robust mechanical properties, exceptional thermal insulation, and high impact resistance to safeguard critical hot-section components and thereby extend their service life. Previous studies have confirmed that high-entropy titanate (La_0.3K_0.1Ca_0.2Sr_0.2Ba_0.2)TiO_3+δ (HE-LKTO) materials have excellent thermal protection properties and mechanical properties. To evaluate the viability of the HE-LKTO for Thermal protection coatings, a novel high-entropy titanate coating with a non-equimolar A-site composition was fabricated via atmospheric plasma spraying. The as-sprayed coatings subsequently underwent a comprehensive analysis of their microstructure and phase structure. Guided by the experimental results, the coating prepared under the optimized conditions was systematically investigated for its thermal protection performance via plasma flame thermal shock testing. The failure mechanism was revealed by analyzing the coating’s dynamic behavior under extreme heat flux. Results show that the HE-LKTO coating prepared at 36 kW exhibits the optimal microstructure: the sprayed particles achieve complete melting and effective spreading, resulting in the lowest surface roughness and porosity. In addition, HE-LKTO coating maintains structural integrity at ablation temperatures of 1400 ℃, exhibiting excellent high-temperature protection performance. At the extreme temperature of 1600 ℃, however, the coating began to spall as a result of accumulated thermal stress induced by the mismatched thermal expansion coefficients between the coating and substrate, as well as crack propagation along interlamellar boundaries and interface separation. This work not only validates the great potential of HE-LKTO as thermal protection coatings but also provides crucial insights into its failure mechanism, laying a foundation for future performance enhancement.