Robust FARADAYIC CNT Based Coating for Scattered Light Suppression

Space-borne instruments, such as telescope housings and baffles where stray light reduction is vital requires the reduction of the stray light from optical payloads. Low reflective coatings (with reflectivity of ~0.1% or less) in the broad spectral range (visible- near infrared) have to be developed. These black coatings should also withstand aggressive space environments and launch conditions with marginal impact on their adhesion and optical performance. A promising candidate with an outstanding diffuse absorptance is chemically vapor deposited layers of carbon nanotubes. However, these coatings are typically grown by expensive and thermally based techniques and can be difficult to apply to 3D structures. Phase I will demonstrate the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity CNT black coatings based on the use of pulse and pulse reverse electrophoretic deposition. This technology will enable the conformal deposition of CNT black coatings on complex shapes and sharp edges on commonly used spacecraft materials such as aluminum and titanium substrates. In Phase I, Faraday will develop an electrophoretic bath formulation and manipulate the pulsed electric field parameters to deposit dense, vertically aligned multi-walled carbon nanotubes onto test substrates, and characterize the deposited coatings to show the potential of achieving the desired reflectivity of 0.1% or less, monitor the thickness uniformity and morphology and demonstrate the potential for durability in severe launch conditions. Finally, a preliminary techno-economic will be completed to show the potential to reduce the cost of existing processes while maintaining required optical properties. Phase II would optimize the deposition parameters, elucidate their effect on scattered light suppression and thermal-structural performance, process alpha-scale components, and, to the extent possible, perform a system-level validation.