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Dielectric properties of graphite‐based epoxy composites
Author(s) -
Kranauskaite Ieva,
Macutkevic Jan,
Kuzhir Polina,
Volynets Nadeja,
Paddubskaya Alesia,
Bychanok Dzmitry,
Maksimenko Sergey,
Banys Juras,
Juskenas Remigijus,
Bistarelli Silvia,
Cataldo Antonino,
Micciulla Federico,
Bellucci Stefano,
Fierro Vanessa,
Celzard Alain
Publication year - 2014
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201431101
Subject(s) - materials science , composite material , graphite , percolation threshold , epoxy , dielectric , percolation (cognitive psychology) , permittivity , composite number , electrical resistivity and conductivity , conductivity , dielectric loss , particle (ecology) , chemistry , oceanography , optoelectronics , engineering , neuroscience , geology , electrical engineering , biology
Composite materials based on epoxy resin filled with various kinds of graphite particles: exfoliated graphite, natural graphite, and coarse, medium and fine artificial graphites have been prepared. Results of broadband dielectric investigations of such materials in wide temperature (25–450 K) and frequency (20 Hz–3 THz) ranges are presented. The dielectric permittivity strongly increases with graphite particle size. The graphite particle size and shape also have a strong impact on freezing temperature, conductivity activation energy and composite electromagnetic absorption properties at room temperature. The lowest percolation threshold is observed for exfoliated graphite (EG)‐based composites. At low temperatures (below glass transition temperature of pure polymer matrix), the electrical conductivity in composites above the percolation threshold is mainly governed by electron tunnelling between graphite particles. At higher temperatures, electrical conductivity due to finite electrical conductivity of polymer matrix and by electron tunnelling from polymer matrix to graphite particles occurs in all composites. Microwave experiments show that EG is the only really effective additive, out of all investigated graphite particles, for producing electromagnetic interference shielding composite materials: 2 wt% of EG in epoxy is indeed not transparent for the electromagnetic radiation at 30 GHz.