Synthesis and dielectric behavior of various novel metal oxide decorated reduced-graphene oxide composites
Synthesis and dielectric behavior of various novel metal oxide decorated reduced-graphene oxide composites
Files
Date
2017-04-01
Authors
Rama Krishna, Jammula
Journal Title
Journal ISSN
Volume Title
Publisher
University of Hyderabad
Abstract
Developing novel dielectric materials has always been an interesting area in material’s
research owing to their importance especially in capacitive energy storage. In this context, at
the time of problem formulation for this thesis work (i.e., during the year 2012), the dielectric
behavior of graphene filled polymers has attracted good attention. However, at that time there
were no reported works on “dielectric behavior” of metal oxides (time tested dielectric
materials) and graphene containing nanocomposites. Therefore in this thesis work elucidation
of various aspects of dielectric behavior of reduced-graphene oxide (r-GO) and metal oxide
containing nanocomposites has been taken up. Owing to the presence of residual oxygen
functional groups and defects in r-GO, it is hypothesized that it will have a unique influence
on the dielectric behavior of metal oxides and r-GO containing nanocomposites. As
anticipated, a unique and strong interfacial polarization (Maxwell-Wagner polarization) was
observed in metal oxide decorated r-GO nanocomposites synthesized by molecular level
mixing technique which resulted in homogenous distribution of metal oxide particles on the
surfaces of r-GO sheets. In this thesis work, CuO/r-GO, ZnO/r-GO, MgO/r-GO and NiO/r-
GO nanocomposites were synthesized and their dielectric behavior in correlation with their
morphology, crystallinity/phase and composition has been elucidated. This thesis also
provides a comprehensive treatment to understand the dielectric behavior, especially the
dielectric relaxation in metal oxide and r-GO containing nanocomposites. The treatment
involves fitting experimental results with suitable theoretical models (for example, Havriliak-
Negami relaxation model) that enable the intricate examination of physical mechanisms that
controlled the dielectric behavior of the nanocomposites under consideration. Percolation
effect on the dielectric permittivity was elucidated in the case of NiO/r-GO nanocomposite
which exhibited a giant dielectric permittivity of 3688. This work will pave a way to
understand and control the possible physical mechanisms that might take place at a very
small length scales and in turn will be useful to control the dielectric behavior of graphene
based nanocomposites in particular and nanocomposites, in general