Preparation of fluorinated carbon nanotube with heterogenous fluorine pattern and the electromagnetic response

The heterogeneous interface structures are widely recognized for the favorable impact on optimizing microwave absorption (MA) properties of microwave absorbers. However, the facile construction of heterogeneous interface and deep exploration of the electromagnetic response is challenging. Herein, we presented an approach of direct fluorination utilizing F2/N2 to construct heterogenous interface on single walled carbon nanotubes (SWCNTs), and the electromagnetic effect was disclosed. By molecular fluorination, fluorinated SWCNTs with heterogeneously aggregated fluorine pattern (M-CNTs-F) were fabricated. The aggregated fluorine pattern on M-CNTs-F lead to stronger polarization loss strength compared to pristine SWCNTs and the discrete-fluorine pattered sample, as well as gradual prolongation of relaxation time (tau) with increase of fluorine content. Consequently, MCNTs-F demonstrates superior MA property with minimal reflection loss (RLmin) and effective absorption band (EAB) value of -49 dB and 5.6 GHz at 1.76 mm with filler content only 2 wt%. Surprisingly, M-CNTs-F also exhibit preferable low frequency MA performance. Based on aforementioned foundations, M-CNTs-F were furtherly architected to construct CNT-contained composite foam, achieving RLmin and EAB value of -66 dB and 10.36 GHz, respectively. Our study highlights the superiority of direct fluorination in constructing heterogeneous interface, and emphasizes the critical role of heterojunction pattern in MA modification.