γ-Fe2O3-MWNT/poly(p-phenylenebenzobisoxazole) composites with excellent microwave absorption performance and thermal stability

Ferromagnetic gamma-Fe2O3 nanoparticles were successfully loaded into multi-walled carbon nanotubes (MWNTs) as probed by transmission electron microscopy. Upon incorporation of the gamma-Fe2O3-MWNTs into poly(p-phenylenebenzobisoxazole) (PBO), a conjugated polymer with high mechanical strength and outstanding thermal and oxidative stability, microwave absorbing materials were obtained. Attributed to the special structure of the gamma-Fe2O3-MWNTs, synergistic effects on dielectric loss and magnetic loss, and a better matched characteristic impedance of the composites were achieved. The optimal minimum reflection loss reached -32.7 dB at 12.09 GHz on a composite containing 12 wt% gamma-Fe2O3-MWNTs with a thickness of 2.7 mm, and the corresponding bandwidth below -5 dB was 6.2 GHz. This demonstrated its potential applications as a low-density microwave absorbing material operating under extreme environments.