Lure the “Enemy” Deep: An Innovative Biomimetic Strategy for Enhancing the Microwave Absorption Performance of Carbon Nanofibers

Abstract

The high conductivity inherent to the dense graphite structures of carbon nanofibers (CNFs) results in microwave reflection, making it a noteworthy topic to design structures that endow CNFs with microwave absorption capabilities. Herein, drawing inspiration from Sun Tzu's strategy of luring the enemy in deep, a novel tree−like heterostructure of CNFs (co−CPAN@PVP) was designed using coaxial electrospinning and subsequent carbonization process. The shell layer consists of a blend of polyacrylonitrile (PAN−2) and polyvinylpyrrolidone (PVP), serving as the bark of the tree, while the core layer, namely the trunk, is made of polyacrylonitrile (PAN−1). During the high−temperature carbonization, the heterostructures of “bark” result in the formation of non−uniform carbon structures on the fiber surface, creating channels that are easily penetrated by microwaves, which act as enemies. The conductive pathways formed by the carbon structure of “trunk”, in conjunction with the polarization sites of “bark”, facilitate microwave attenuation. The results show that co−CPAN@PVP with heterostructures has good impedance matching characteristic and microwave attenuation ability: The minimum reflection loss (RLmin) at 1.8 mm is −55.19 dB, and the effective absorption bandwidth (EAB) is 5.695 GHz. This research has inspired the design of heterostructures for high−performance and lightweight carbon−based microwave absorbing materials (MAMs). Moreover, it introduces a solution for recycling and reusing waste electromagnetic and thermal energy, potentially mitigating pressing environmental and energy challenges.