Understanding the interaction in functionalized multi-walled carbon nanotube/polyaniline composite by impedance study at low temperature

Abstract

The impedance, modulus spectroscopy and dielectric properties of polyaniline (PANI) and composite with multi-walled carbon nanotube (MWCNT) of different degrees of functionalization are studied from 300 to 4.2 K in the frequency range 40 Hz–5 MHz. At low temperature (T ⩽ 100 K), grain and grain boundary relaxation peaks are observed in PANI. In composites, MWCNT forms a network between less and highly conducting grains, increases dc conductivity, and shows no relaxation peak at low temperature. The chemical functionalization of MWCNT increases the polar interaction between MWCNT and PANI, shifts the relaxation peaks towards lower frequency and slows the relaxation process. The relaxation process is manifested as non-Debye type and it tends towards Debye type with increasing temperature in functionalized muti-walled carbon nanotube (fMWCNT) PANI composites, and explained by Bergman’s theory. The relaxation barrier energy at the interface of fMWCNT and PANI increases with increasing degree of functionalization which is the effect of enhanced interfacial (Maxwell Wagner–Sillars) polarization. In MWCNT composite, the real part of dielectric constant shows high negative value below 10 K at lower frequency ( < 950 Hz) and it becomes positive due to functionalization of MWCNT. An additional crossover from positive to negative occurs in both MWCNT and fMWCNT, PANI composite above temperature 60 K and frequency 500 Hz. This crossover shifts towards higher temperature and frequency with increasing degree of functionalization. The negative value and crossover of dielectric constant are explained by Drude–Sommerfeld model.

Magnetic field driven dielectric relaxation in non-magnetic composite medium: A low temperature study

“…The relaxation frequency does not vary with increasing magnetic field for composites at constant temperature; however, it shifts towards higher frequency with increasing the degree of functionalization of MWNT in different composites. The relaxation peak frequency increases from 63 Hz to 160 Hz when the duration of functionalization increases from 0 h to 96 h. The functionalization of MWCNT enhances the interfacial polarization and increases the boundness (attachment of charge carrier with other atom, related to the spring constant of potential which holds the charge in place) of charge carrier between fMWCNT and PANI [13]. The enhanced boundness of charge carriers help to relax fast with applying magnetic field and relaxation frequency shifts towards higher value.…”

Strategies for the effective design and regulation of carbon-based metacomposites: a review

“…Meanwhile, Luo et al chose the insulating polymer POE as the substrate to achieve negative permeability and permittivity. 67 In addition, the negative dielectric properties of CNTs combined with various matrixes such as phenolic resin, 68 polypropylene, 63 polyaniline, 69 polydimethylsilane, 70 and polypyrrole 71 were reported.…”