Effect of acidification and spiralization on the microstructure and microwave absorbing properties of carbon nanotubes

In this work, acidified and helical carbon nanotubes were prepared by magnetron sputtering, and their electromagnetic parameters and absorption properties were analyzed. Their mechanism of electromagnetic wave-absorbing attenuation was investigated through the finite element method. The acidification and spiralization treatments reduced the diameter of the carbon nanotubes, introduced a large number of internal defects and oxygen-containing functional groups, reduced the effective conductivity, increased the penetration depth, promoted the dielectric polarization relaxation, and made the dielectric parameters more suitable for electromagnetic wave absorption, resulting in an improvement in the impedance matching characteristics and electromagnetic wave absorption performance. The finite element calculations indicated that carbon nanotubes with a helical structure exhibited a more uniform distribution of the scattering electromagnetic field and a smaller intensity. As the small ratio of length to diameter decreased, the intensity of the scattering field gradually decreased and their distribution became more uniform. Furthermore, the acidified helical carbon nanotubes exhibited excellent absorption properties with a maximum absorption bandwidth of 5.60 GHz at a matching thickness of 1.53 mm, and a minimum reflection loss of − 32.14 dB at 12.60 GHz at a matching thickness of 1.79 mm. Therefore, acidified helical carbon nanotubes showed great potential in the application of microwave absorption.