Fe₃O₄Nanoparticles Embedded Hollow Mesoporous Carbon Nanofibers and Polydimethylsiloxane-Based Nanocomposites as Efficient Microwave Absorber

Abstract

The combined effect of both hollow, mesoporous structure of carbon nanofiber and Fe3O4 nanoparticles on the microwave absorption properties of polydimethylsiloxane nanocomposites have been investigated. Nanofibers with above characteristics were prepared via coelectrospinning the solutions of polyacrylonitrile/FeCl3 and poly(methyl methacrylate) followed by stabilization and carbonization at elevated temperatures. Carbonized nanofibers contained Fe3O4 nanoparticles with average crystallite size of ∼12.3–14.6 nm and exhibited a surface area of 126.4–377.7 m2/g. Catalytic graphitization surrounding Fe3O4 nanoparticles was seen in high-resolution transmission electron microscopy and also supported by a decrease in intensity ratio of D to G bands in Raman spectra. Microwave absorption properties of nanocomposites were investigated in a vector network analyzer using a coaxial waveguide in the frequency range of 2–18 GHz and found to be dependent on thickness, filler loading, and Fe3O4 content of the nanofibers. At an absorber thickness of 7.5 mm with 25 wt % carbon nanofibers (consisting 5 wt % Fe3O4), the absorption bandwidth was found to be a maximum of 4.33 GHz with reflection loss of −25 dB. However, corresponding bandwidth was increased to 4.51 GHz with reflection loss of −44 dB for nanocomposite with 25 wt % carbon nanofibers (but containing 7.5 wt % Fe3O4) at only 5.5 mm absorber thickness.