Nanoparticles-decorated coal tar pitch-based carbon foam with enhanced electromagnetic radiation absorption capability

Abstract

In the present study, to replace existing high-density radar-absorbing materials (RAM) for civil and military aerospace applications, lightweight coal tar pitch-based carbon foam (CFoam) was developed by a sacrificial template technique. The CFoam was decorated with Fe₃O₄ and ZnO nanoparticles to improve electromagnetic (EM) radiation absorption to make it useful as RAM. To ascertain the effect of the decorated nanoparticles on the CFoam, it was characterized by scanning electron microscopy, X-ray diffraction, a vector network analyzer and a vibration sample magnetometer. It was observed that Fe₃O₄ and Fe₃O₄–ZnO nanoparticles have a positive effect on the overall properties of CFoam. The compressive strength of CFoam increases by 22% and its thermal stability increases by 100 °C, whereas its electrical conductivity decreases by almost 25%. The total shielding effectiveness (SE) of CFoam increases from −25 dB to −54 and −56 dB, respectively, for Fe₃O₄- and Fe₃O₄–ZnO nanoparticles-decorated CFoam. The enhancement in total SE for Fe₃O₄- and Fe₃O₄–ZnO-coated CFoam is basically due to the contribution of absorption losses by −42 and −45 dB. The Fe₃O₄ and Fe₃O₄–ZnO coatings increase surface resistance and magnetic properties because the ferromagnetic nanoparticles act as tiny dipoles, which become polarized in the presence of an EM field and result in the better absorption of EM radiation. This clearly demonstrates that decorated nanoparticles on conducting lightweight CFoam are useful as RAM for different applications to attenuate EM radiation.