The effect of polyethylenimine on the microwave absorbing properties of a hybrid microwave absorber of Fe3O4/MWNTs

The hybrid microwave absorber of Fe3O4/multi-walled carbon nanotubes (MWNTs)modified with polyethylenimine (PEI) polymers was fabricated by chemical co-precipitation. The structure and morphology of hybrids are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron-microscopy (TEM). The effect of PEI on the distribution of Fe3O4 nanoparticles and the microwave absorbing properties of hybrid microwave absorber of Fe3O4/MWNTs were investigated. The TEM results show that Fe3O4 nanoparticles are attached homogeneously on MWNTs, which indicates that the adding of PEI is effective to control the distribution of Fe3O4 nanoparticles on the surface of MWNTs. The microwave absorbing properties results show that the maximum reflection loss (RL) of PEI modified Fe3O4/MWNTs hybrids is improved significantly, which is −30.69 dB at 7.24 GHz and −10 dB bandwidth is 1.84 GHz. However, the RL of the Fe3O4/MWNTs without PEI is −21.96 dB at 7.02 GHz and −10 dB bandwidth is 1.2 GHz.