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Journal of Inorganic Materials

Journal of Inorganic Materials

   

Preparation and Electromagnetic Wave Absorption Properties of 3D Network-Structured Fly Ash Microbeads @Carbon Nanotubes Composites

ZHANG Xiaomin1,2,*, TONG Liangyu1, GAO Hongjie2, CHEN Xu1, YAN Huhu1, GAO Yang1   

  1. 1. School of Resource Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China;
    2. School of Materials Science and Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China
  • Received:2025-04-26 Revised:2025-06-09
  • About author:ZHANG Xiaomin (1975-), male, PhD, professor. E-mail: xmzhang@xauat.edu.cn
  • Supported by:
    Shaanxi Province Key Research and Development Program Project (2024GX-YBXM-420); Xianyang City Science and Technology Bureau Key Research and Development Program Project (2021ZDYF-GY-0034); Xi'an University of Architecture and Technology 2024 National-level Undergraduate Innovation and Entrepreneurship Project (202410703063)

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Abstract: With the rapid development of 5G communication and miniaturization of electronic devices, the development of lightweight, broadband and high-efficiency electromagnetic wave absorbing materials has emerged as a critical solution to the challenges posed by electromagnetic pollution and information leakage. Traditional absorbing materials face significant limitations, such as high density, narrow absorption band and poor environmental compatibility, while the resource utilization of industrial solid waste provides an innovative path for the design of high-performance absorbing materials with both economic and ecological benefits. In this study, magnetic fly ash (MFA) beads were derived from the solid waste of coal-fired power plants through magnetic separation. Additionally, magnetic fly ash @carbon nanotubes (MFA@CNTs) composite wave-absorbing materials with a three-dimensional interpenetrating network structure were successfully constructed by chemical vapor deposition (CVD) using in situ-loaded Fe-based nanoparticles on the surface of the MFA beads as catalysts. Microstructural characterization showed that the bamboo-like CNTs grown on the surface of the MFA microbeads formed a porous structure by inter tubular winding and bridging with the silicate framework. The composite material achieves minimum reflection loss (RLmin) of -44.52 dB at 8.8 GHz (with thickness of 2.99 mm) and effective absorption bandwidth (EAB, RL < -10 dB) covering 4.72 GHz (with thickness of 1.7 mm). The performance enhancement mechanism can be attributed to the following: (1) the magnetic component (Fe₃O₄) present in the MFA beads interacts with the conductive network of the CNTs, thereby establishing a magneto-electrical coupling effect to optimize the impedance matching; (2) the defective structure of the bamboo-like CNTs induces multiple polarization relaxation (including interfacial and dipole polarizations), significantly enhancing the dielectric loss; and (3) the 3D porous network extends the propagation path of electromagnetic wave, thereby promoting multiple reflection and scattering losses. This study not only provides a new paradigm for high-value utilization of industrial solid waste, but also lays a theoretical and technical foundation for the design of lightweight broadband wave-absorbing materials.

Key words: MFA@CNTs composites, 3D network structure, electromagnetic wave absorption

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