Modeling and Simulation of Artificial Core-Shell Based Nanodielectrics for Electrostatic Capacitors Applications
Comsol
October 13, 2011
The need for high storage capacitors led to
the development of polymer based capacitors.
Polymers have high processability, mechanical
flexibility, electrical breakdown strength and
compatibility with printed circuit board (PCB)
technologies but usually have very low permittivity
(K). The permittivity of the polymer as well as its
dielectric strength can be tuned to desired
characteristics by introducing metallic nano fillers. In
the 2010 COMSOL Multiphysics conference, we
presented characteristics of capacitors fabricated with
Au (core) and SiO2 (shell) nano composites,
dispersed in Polyvinyl Pyrrolidine (PVP) polymer
solution. Effective Medium Theories (EMT) of
Maxwell-Garnett, Bruggeman and Looyenga models
were employed to calculate K value. It was found
that with increase in volume loading of the Au
nanofiller, K value of the composite increases. The
dielectric permittivity of modified PVP increased
from 7 to 1400 at percolation threshold using AuSiO2 core-shell nanoparticles. In this work, the Au
nanoparticle and SiO2 shell are replaced by silver
(Ag) and polystyrene (PS) shell, respectively. The
usage of polymer coating instead of SiO2 cuts down a
step in the preparation of core-shell nanoparticles,
thus making the process simpler and cost effective.
Removal of SiO2 layer increases the polarization
around the metallic core as a result of improvement
in the acting electrical potential. This modification
also leads to significant cost reduction in the
fabrication process ingredients as Ag is less
expensive than Au. Improved electrical performance
can also be achieved, since Ag presents higher
conductivity than Au. In COMSOL Multiphysics
software, the AC/DC module is selected and the Inplane electric currents are applied to the physical
model. The modified EMT is applied to the polymer
core-shell to calculate the effective electrical
properties of the composite. The percolation data
analysis is used to predict the maximum theoretical K
value of the composite and results of both 2D and 3D
models under different amount of filler loading are
presented.
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Tags: Engineering, Manufacturing
