Significant effect of sorbed water on the electrical and dielectric behavior of graphite oxide

This paper reports the unexpectedly strong effect of 4 wt% additional sorbed water on the electrical and dielectric properties (50 Hze2 MHz) of graphite oxide (GO) containing 18 wt% sorbed water. Water contents of 18 and 22 wt% (designated GO18 and GO22, respectively) are compared, with the former obtained by heating at 60 C (3 h) immediately before testing. The additional water increases the conductivity and decreases the conductivity anisotropy. It enhances the conductivity at any frequency, but enhances the relative dielectric constant (real part) at <200 Hz. Above 200 Hz, it decreases the dielectric constant. Concerning the specimen-contact interface, the interfacial resistivity and specific interfacial capacitance are decreased. The negative of the relative dielectric constant (imaginary part) is greatly increased by the additional water. Reduced graphite oxide (RGO) exhibits higher conductivity than GO22, which exhibits much higher conductivity than GO18. Compared to RGO, GO22 exhibits lower conductivity, higher interfacial resistivity and higher specific interfacial capacitance. The relative dielectric constant (real part) is higher for GO22 than RGO at <500 Hz (due to the water), but is lower for GO22 at >500 Hz. The through-thickness electrical/dielectric properties of GO22 are modeled with GO18, additional water and air in parallel. © 2017 Elsevier Ltd. All rights reserved.