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.