Microwave absorption property of aligned MWCNT/Fe3O4

Abstract

This study investigated the microwave absorption properties of magnetic modified multiwall carbon nanotubes (MWCNTs) with different alignments to the electric field (E vector) of the incident electromagnetic (EM) waves. MWCNTs were decorated with Fe3O4 nanoparticles using the wet chemical method and the resulting MWCNT/Fe3O4 was then used as a filler in a MWCNT/Fe3O4/epoxy resin composite at different weight-to-epoxy-resin ratios (2%, 5%, and 8%) with good uniformity and alignment. For each filler concentration, three samples were produced with different alignments of carbon nanotubes using the solution-casting method. For sample one, the nanotube axis (k) was parallel to the E vector of the EM wave, for sample two, k was perpendicular to E, and the third sample contained randomly oriented nanotubes. Magnetic MWCNTs were exposed to a 0.4T magnetic field in the desired direction to achieve the desired alignment of carbon nanotubes in epoxy resin. Microwave absorption characterization of the considered ranging band (X-band) at all concentrations where the alignment of MWCNT/Fe3O4 was parallel to the incident E vector showed increased absorption. Samples with a perpendicular alignment of MWCNT/Fe3O4 to incident E had the lowest absorption. Samples containing 2wt% and 8wt% MWCNT/Fe3O4 aligned parallel to E and had reflection losses exceeding 14.4dB and 23.6dB, respectively, over a 10–11GHz range. The 5wt% parallel aligned MWCNT/Fe3O4 showed an absorbing peak of 27dB and a bandwidth broadened to 1.2GHz.