Electrophoretically Deposited Graphene-Based 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. The work function of graphene can be tuned by either metal doping or functionalization, thereby increasing the electron yields and enhancing the possibility of emission through negative electron affinity. Within this context, Faraday Technology is working on developing an electrophoretic bath formulation and manipulate the pulsed electric field parameters to deposit graphene-based coatings onto test substrates, which may maintain integrity of spacecraft by autonomous electron emission in relevant environments. As shown in the Figure, uniform graphene-based coatings have been formed on an aluminum substrate. The coatings are characterized and evaluated by optical microscopy, scanning electron microscopy, and field-emission scanning electron microscopy. Faraday will also investigate the incorporation of metal particles into graphene film to tailor the emission properties, allowing for obtaining the low work function. The demonstrated technology not only addresses the desire to introduce novel manufacturing techniques for spacecraft charging mitigation, but also provides a scalable thin film and low-cost manufacturing process that has the potential of producing low reflective coatings. Acknowledgements: The financial support of DOD Air Force Contract No.: FA9453-19-P-0573 is acknowledged. Figure 1