4, Portland State University, Portland, Oregon, United States
2, University of California, Merced, Merced, California, United States
Atmospheric pressure and ambient temperature micro-plasmas have been used for polarization of piezo-composites towards alignment of the electric dipoles. Dielectric polarization is caused when a dipole moment is formed in an insulating material because of an external electric field. When a dielectric interacts with an electric field a shift in charge distribution takes place, aligning the positive and negative ions with the electric field. By this mechanism important circuit elements such as capacitors can be developed. The same phenomenon of plasma micro-discharge can also be used for surface modification of piezoelectric-composites towards activation and enhancement of electrical properties of the material surface. This can be achieved by chain polymerization of the surface in organic composite thin films and modification of surface energy that changes the surface bonding characteristics and towards enhancing surface charge density. The current work focuses on the development and use of a corona discharge setup for surface modification of piezoelectric flexible composites. Three quasi-stable voltage driven micro-discharge regimes with a current of 0.1 mA and voltages of 3, 3.5 and 4 kV and a pulsed regime with a voltage 2.5 kV and current of 0.5 mA has been identified for surface modification. ZnO-Epoxy-Graphene composites are prepared with a variation of ZnO volume fraction from 10% to 70%. The capacitance, resistance, impedance and dielectric constant of these composite thin films are characterized using an impedance analyzer. The micro-structure and elemental properties are characterized using a Scanning Electron Microscope, EDS and a Raman spectrometer. The surface topography of the thin films are also characterized using a Profilometer. A 35-50% enhancement in the capacitance and dielectric constant values are observed for the quasi-stable corona discharge regimes.