Reduced-Graphene-Oxide-Based Thin Films: An Alternative Coating for Harsh Space Environments

Polymeric materials are commonly used as the outermost layer in spacecraft passive thermal control. However, in geostationary earth orbit environments, the polymeric layer is susceptible to environmental hazards, particularly electrostatic charges. In this study, we develop a graphene-based coating on a polymeric polyimide (Kapton^®) and discuss its suitability in simulated harsh space environments for electrostatic dissipation. An about 80-100 nm thick conducting reduced graphene oxide (rGO) coating was developed on Kapton® by a simple and cost-effective spray technique while ensuring minimal variation in the thermo-optical properties and hence the equilibrium temperature. The spaceworthiness and stability of the coating were evaluated through simulated space environment tests, including thermal cycling, thermal vacuum, relative humidity, adhesion, and aging tests. Structural, optical, and electrical properties were found to be preserved after spaceworthiness tests, demonstrating the durability of the coating in harsh space environments. Furthermore, field emission scanning electron microscopy demonstrated significant electron charging on uncoated Kapton^®, with a gradual reduction in charge buildup for GO-coated Kapton^®, and almost negligible charging on rGO-coated Kapton^® when subjected to electron bombardment at 10, 15, and 20 kV. Kelvin probe force microscopy further confirmed the enhanced electrostatic dissipative properties, showing a notable decrease in surface potential from 300 mV for uncoated Kapton^® to 60 mV for rGO-coated Kapton^®. These findings suggest that the developed graphene-based coating holds promise as a space-survivable solution for electrostatic dissipation in a spacecraft.