Surface modification and microwave absorption properties of lightweight CNT absorbent

Ultra-thin electromagnetic absorption materials promise great application potential in stealth technology and integrated microwave device. However, the large thickness of the current low-density carbon-based composites is still a critical issue to hinder their practical application. Herein, the carbon nanotubes (CNTs) were oxidized by using mixed acid and strong oxidant, and the lightweight resin-based CNTs coatings were fabricated via a facile method. The composite coatings after modification demonstrate an excellent microwave absorption performance at low thickness. With the low filler loading of 2.3 wt%, the maximum absorption is as strong as 20.4 dB and the effective absorption bandwidth (reflection loss ≤ − 10 dB) reaches 4.51 GHz covering 45.1% of the entire measured bandwidth at only 1.2 mm thickness. Compared with the CNTs coatings before modification, the CNTs coatings after modification possess broader effective absorption bandwidth, and the optimal filler loading of the absorbent shifts to a lower concentration. This work provides a feasible approach for the preparation of composite coatings with high-performance absorption.