WU Jinbo, YANG Guodong, ZHANG Jingzhe, YUAN Gaoqian, HE Hongzhang, ZHANG Haijun, LI Faliang
(The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China)

Extended Abstract: [Significance] With the widespread application of electromagnetic waves in defense and civilian sectors, the risks of information leakage and electromagnetic pollution have gradually increased, becoming a significant problem. Wave-absorbing materials play a crucial role in modern communication and information security by effectively absorbing electromagnetic radiation, which not only reduces electromagnetic interference but also prevents the leakage of sensitive information and mitigates potential health hazards. Due to their unique composition and structure, high-entropy materials exhibit excellent electromagnetic properties and are promising candidate as electromagnetic wave absorption materials. The compositional characteristics of these materials are defined by the presence of five or more major metal elements, which are evenly distributed at the nanoscale, forming single-phase or multi-phase structures that can efficiently absorb electromagnetic waves over a wide frequency range. This multi-element mixing can produce significant changes in complex dielectric constant and magnetic permeability, thereby enhancing the absorption properties of the material. Compared with traditional single-element or binary systems, high-entropy materials demonstrate superior performance and broader application prospects in electromagnetic wave absorption. From military stealth technology and radar absorption to civilian anti-electromagnetic interference, information protection, and environmental health, high-entropy materials are gradually becoming a key technology for addressing electromagnetic wave-related issues. However, despite the advantages of high-entropy materials, there are still numerous challenges in their preparation, modification and application. This article was aimed to review the research progress of high-entropy alloys, high-entropy alloy composites, and high-entropy ceramics for electromagnetic wave absorption, analyze the influencing factors, explore enhancement methods, evaluate the problems and propose future development directions.[Progress] The structural characteristics of high-entropy materials and their relationship with stability and various ion arrangements are described, whereas various high-entropy alloys or similar high-entropy derivative structures that can be generated through the combination of different elements are highlighted. Then, the specific compositions of high-entropy alloys, high-entropy alloy composites, and high-entropy ceramics, including their chemical composition, microstructure, and unique physical and chemical properties are delved, with a particular emphasis on their advantages in electromagnetic absorption. Subsequently, the main factors affecting the microwave absorption properties of high-entropy materials, such as the composition ratio, microstructure, thickness, density, and surface morphology of the materials, are analyzed. Taking high-entropy alloys as an example, how the ratio of transition metal elements influences the complex dielectric constant and magnetic permeability of materials is discussed, which in turn impacts their microwave absorption properties. Additionally, for high-entropy alloy composites, how to improve the overall absorption performance by combining them with other materials that have specific absorption properties through composite effects is introduced. The section on high-entropy ceramics focuses on their structural design and composition optimization, to exhibit desired absorption properties in a specific frequency range. Also, several feasible methods to enhance the absorption capability of high-entropy materials are evaluated, including composition design, microstructure control, and surface modification using chemical or physical means, with the aim of finding more effective solutions to improve the performance for practical applications. At the same time, the problems in the preparation, modification and application of high-entropy materials, such as high synthesis costs, complex processes and poor thermal stability, are pointed out. Finally, future research directions of these special microwave absorption materials are proposed.[Conclusions and Prospects] The current research progress on high-entropy alloys, high-entropy alloy composites, and high-entropy ceramics in the field of electromagnetic wave absorption has been reviewed. High-entropy materials not only exhibit excellent electromagnetic absorption properties due to their unique composition and structure, but also demonstrate characteristics such as ease of design and a wide range of regulation, making them highly potential for application in electromagnetic wave absorption. In the future, to further promote the practical application of high-entropy absorbing materials, research should focus more on exploring and optimizing the controllable doping technology of active metal ions in different crystal lattices of high-entropy materials, and developing more reliable means to adjust the electromagnetic parameters of materials, such as optimizing performance by adjusting the density, thickness or composition ratio of materials. Moreover, given the complex preparation process and high cost of high-entropy materials, finding a low-cost and efficient preparation method is also crucial. In terms of material properties, it is necessary to strengthen research on the stability of high-entropy materials at high temperatures to ensure their reliable performance in extreme environments. In terms of applications, with the development of technologies such as 5G communication, wireless charging and the Internet of Things, the demand for electromagnetic wave absorbing materials will become more and more widespread. High-entropy materials are expected to play more important roles in solving electromagnetic interference and information leakage problems.
Key words: high-entropy materials; high-entropy alloys; high-entropy ceramics; electromagnetic wave absorption