GRAPHENE-BASED TRANSPARENT AND CONDUCTING COATING FOR SPACECRAFT APPLICATION

Abstract

Graphene has attracted a tremendous amount of attention over the past few years because of its outstanding electrical, mechanical, and chemical properties. Additionally, graphene exhibits remarkable flexibility and chemical stability. Various efforts have been made to use these fascinating properties for macroscopic applications, such as transparent conducting films that can replace indium tin oxide (ITO). This thesis presents the deposition, optimization, and analysis of optically transparent and electrically conductive graphene-based thin films for space applications, with a focus on mitigating accumulated electrostatic charges. In Geostationary Earth Orbit (GEO) environments, the spacecraft is susceptible to environmental hazards, particularly electrostatic charges. Polymeric materials are commonly used as the outermost layer in spacecraft passive thermal control. Despite their excellent radiation and chemical resistance as well as their thermal stability, these films are prone to spacecraft charging. This can result in electrostatic charge build-up, eventually causing spacecraft charging and hence serious damage to delicate spacecraft electronics. The surface resistivity needed to mitigate ESC build-up on insulators is in the range of 106 to 1010 Ω/sq. The goal of the present study is to develop reduced graphene oxide (rGO) film on space-suitable polymer/glass substrates deposited through a simple and cost-effective technique. Though graphene can be synthesized by liquid and mechanical exfoliation, epitaxial growth, and chemical vapor deposition (CVD) methods; the production yield in these routes are very low. So, for the industry-based synthesis, here graphene oxide (GO) is synthesized by Modified Hummer’s Method, and reduced by various green and synthetic reducing agents to select the best-suited reducing agent for the intended spacecraft application. The wet process methods such as spray-coating, spin-coating, and dip-coating are low in cost and simple in operation. For the present work, a spray-based coating is selected with optimized substrate heating temperature, pressure, carrier gas and flow rate. The resulting coatings were then characterized for morphology, structure, thickness, electrical conductivity, optical, and thermo-optical properties, proving the coatings met the desired specifications without significantly altering the substrate’s inherent properties. Following the successful development on Kapton® substrates, the coatings were applied to rigid and flexible Optical Solar Reflector (OSR) substrates.