Ultralight and rigid PBO nanofiber aerogel with superior electromagnetic wave absorption properties

Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic (EM) wave absorption materials. In this study, an ultralight and rigid poly(p-phenylene benzobisoxazole) nanofiber (PNF) based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy (CoNi) nanoparticles and carbon nanotubes (CNTs) as magnetic and conductive fillers, respectively. A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method, and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel. CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles. The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss, magnetic loss, multiple reflection, scattering, and absorption. When its thickness was 4 mm, the CoNi/CNT/PNF aerogel showed a minimal reflection loss of −44.7 dB (at 6.88 GHz), and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band (12.32 GHz, from 5.68 GHz to 18 GHz). In addition, the rigid aerogel exhibited an ultralow density (0.107 g/cm³), excellent thermal insulation, and flame retardancy, demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.