Electrophoretically Deposited Graphene-Based Composite Coatings for Spacecraft Charging Mitigation

Abstract

Spacecraft charging has been recognized as an important consideration for spacecraft design, and occurs due to interaction between hazardous space plasmas and spacecraft surface. Spacecraft can experience charging throughout operation due to high flux of incident electrons (ex. during geomagnetic sub-storm). As a result, different materials/components may experience a range of potentials which may lead to plasma-induced arcs, damaging spacecraft components. Graphene are emerging two-dimensional (2D) carbon materials with excellent physical and chemical properties, such as high conductivity, high tensile strength, high transparency, and high carrier mobility. These excellent properties make graphene potentially useful for applications in energy storage, aerospace, coatings and polymer markets and thermal protection. Substrates constituted by graphene harness the thermal and mechanical properties to create novel coatings with superior performance, hence broadening the graphene application spectrum. Of particular interest is the potential capability of graphene-based materials to provide increased protection against spacecraft charging in the space plasma environments. Furthermore, the work function of graphene can be tuned by either metal doping or functionalization, thereby facilitating autonomous or passive electron emission and increasing the electron yields and enhancing the possibility of emission through negative electron affinity. By enabling charge dissipation between the various components at modest potential differences, discharge arcing may be preventedWithin this context, Faraday Technology is developing a graphene-based composite coating with high electron yields over a wide range of incident electron energies. This approach utilizes electrophoretic deposition to deposit graphene-based coatings onto test substrates, which may maintain integrity of spacecraft by autonomous electron emission in relevant environments. Next, an electrochemical process is used to decorate the graphene surface with various low work function metals (alkali, alkaline earth, transition). This approach offered significant improvements in the electron yield (290% increase over the undecorated coating) and substantially extended the range (~9 times) of incident electron energies between crossover points as shown in Figure 1/Table 1.Acknowledgements: The financial support of DOD Air Force Contract No.: FA9453-19-P-0573 is acknowledged. Figure 1