Studying Loading-Temperature Effects in Electric Conductivity of Graphene-Epoxy Nanocomposites

Multilayered graphene nanoplatelets (MLGs) have been prepared by using the electrochemical technique, starting from thermally-expanded-graphite flakes. Structural properties of MLGs have been tested by SEM, X-ray diffraction, and nitrogen absorption technique. Electrical conductivity
$(\sigma=\varepsilon_{0}\ \varepsilon_{2}\ \omega)$
of MLG nanocomposites based on a DGEBA-epoxy resin have been determined by measuring complex dielectric permittivity
$(\varepsilon/\varepsilon_{0}=\varepsilon_{1}+j\ \varepsilon_{2})$
within the frequency
$(\omega/2\pi)$
range of 4–100 Hz, temperature
$(T)$
range of 90–350
$\mathrm{K}$
for mass loadings
$(\varphi_{m})$
varied from 0 to 5%. The later correspond to volume loadings
$(\varphi_{v})$
of 0-2.7 %. The dependences of
$\sigma$
versus
$\omega, T$
, and
$\varphi_{v}$
and possible mechanisms of composite's conductivity have been discussed and a phenomenological model to describe charge transport on graphene-epoxy interfaces has been proposed.