Flexible, Stretchable, and Lightweight Hierarchical Carbon-Nanotube-Decorated Carbon Fiber Structures for Microwave Absorption

Abstract

Highly flexible, bendable, stretchable, and ultralightweight microwave absorbers (MA) that can handle harsh environments are essential for conformal surface coating in aerospace and defence industries. Hence, crystalline carbon nanotubes (CNTs) are grown on carbon fibers (CFs) using the chemical vapour deposition technique (CVD) and embedded in polyurethane (PU) to obtain MA. The fabricated MA is flexible, highly stretchable (>400%), has a low percolation threshold (0.1 wt %), ultralightweight (0.35 wt %), and thin nanocomposite for enhanced microwave absorber performance. The thickness of MA is optimized to achieve the impedance matching condition by utilizing the CST microwave studio simulation and verified experimentally. The minimum reflection loss (RL) of −52.53 dB with effective absorber bandwidth (EAB) covering the complete X band at a 2.4 mm thickness is obtained for just 0.35 wt % CFCNT. The negligible change in RL and EAB after 1000 bending cycles and 2 h of water-bath sonication confirms the operating efficiency of MA in harsh environmental conditions. The mechanism of microwave absorption in the case of CF and CFCNT-based MA is elucidated concerning microwave properties, electrical conductivity, and morphology. The CST microwave studio simulation is also extended from the X band to the Ku band (12.4–18 GHz) for broadband microwave absorber application.