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Joint effect of the tube sizes and Fe-filling process on microwave dielectric properties of carbon nanotubes

Li, Junying, Zhu, Yong, Wang, Xin, Zhang, Jie, Ding, Yimin, Zhang, Xiaolei, Quan, Jiamin, Wang, Ning
Carbon 2017 v.119 pp. 386-393
carbon nanotubes, dielectric properties, dispersibility, ferric oxide, polymers
To explore the effect of tube sizes and filling process on dielectric properties of carbon nanotubes (CNTs), CNTs with various diameters and lengths were applied to synthesize Fe-filled CNTs through wet-chemical method. The permittivities of the composites of CNTs and paraffin rely on the dispersion state (agglomeration) of CNTs in polymer matrices. During the filling process, CNTs with diverse tube parameters and dispersibility experienced different structural transformations, and different iron oxides (either Fe3O4 or Fe2O3) particles (depending on the dispersibility of CNTs) were observed adhering to walls of CNTs after filling. The discrepancies along with the dispersibility of CNTs per se alter the order of the permittivity (from high to low) within samples. The smallest agglomerates and the largest permittivity were obtained for CNTs with diameters of 10–20 nm and lengths of 10–30 μm, both before and after the filling of CNTs. The role that the shape parameters played in the dielectric properties during the whole filling process was analyzed. The frequency-dependent permittivity spectrum was also examined and it obeyed Jonscher’s universal dielectric relaxation law.