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Open AccessArticle

Dielectric Relaxation in the Hybrid Epoxy/MWCNT/MnFe2O4 Composites

1
Vilnius University, Sauletekio Ave. 3, LT-001222 Vilnius, Lithuania
2
Center for Physical Science and Technology, Sauletekio Ave. 3, LT-001222 Vilnius, Lithuania
3
Institute for Nuclear Problems, Belarusian State University, Minsk 220006, Belarus
4
Institute of Photonics, University of Eastern Finland, Yliopistokatu 7, FI-80101 Joensuu, Finland
*
Author to whom correspondence should be addressed.
Polymers 2020, 12(3), 697; https://doi.org/10.3390/polym12030697
Received: 14 February 2020 / Revised: 20 March 2020 / Accepted: 20 March 2020 / Published: 21 March 2020
(This article belongs to the Special Issue Epoxy Resins and Composites)
The electrical properties of epoxy/MWCNT (multi-walled carbon nanotubes)/MnFe2O4 hybrid composites loaded with MWCNTs (below, 0.09 vol.%, and above, 0.58 vol.%, percolation threshold) and varying concentrations of MnFe2O4 up to 10 vol.% were studied in a wide frequency range (20 Hz–40 GHz) at different temperatures (20 K–500 K). At low frequencies, the dielectric permittivity and the electrical conductivity of composites with fixed amounts of MWCNT are strongly dependent on MnFe2O4 content. For MWCNT concentrations above the percolation threshold (i.e., 0.58 vol.%), the electrical conductivity highly decreases with the increase of the MnFe2O4 fraction. In contrast, for the epoxy/MWCNT just below the onset of electrical conductivity (0.09 vol.% of MWCNTs), there exists an optimal concentration of MnFe2O4 inclusions (i.e., 0.025 vol.%), leading to a dramatic increase of the electrical conductivity by three orders of magnitude. The electrical transport in composites is mainly governed by electron tunneling at lower temperatures (below 200 K), and it is highly impacted by the matrix conductivity at higher temperatures (above 400 K). The electrical properties were discussed in terms of the Maxwell–Wagner relaxation and distributions of relaxation times. A non-invasive platform based on dielectric relaxation spectroscopy was proposed for enhancing the synergetic effect coursed by using multiple nanoinclusions in polymer composites just below the percolation threshold. View Full-Text
Keywords: epoxy; carbon nanotubes; electrical properties; MnFe2O4; DC conductivity; transport epoxy; carbon nanotubes; electrical properties; MnFe2O4; DC conductivity; transport
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MDPI and ACS Style

Meisak, D.; Macutkevic, J.; Plyushch, A.; Kuzhir, P.; Selskis, A.; Banys, J. Dielectric Relaxation in the Hybrid Epoxy/MWCNT/MnFe2O4 Composites. Polymers 2020, 12, 697.

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