Direct CVD Growth of Robust Carbon Nanofiber-Based Super Black Coatings on Complex-Curvature and Commercial Anodized Al(6061) for Enhanced Stray-Light Suppression in Optical Baffle Systems

We report a scalable method for fabricating carbon nanofiber (CNF)-based super black coatings directly on commercial Al(6061) substrates via a catalyst-integrated thermal CVD process. Anodization and sealing treatments facilitate in situ Ni catalyst incorporation into the porous oxide layer, eliminating the need for external deposition. Notably, black anodized Al(6061) introduces a Cr-rich surface layer, which enhances catalyst stability and CNF growth uniformity. The presence of the Cr–Ni interface improves coating robustness under mechanical agitation and UV exposure, confirming its role in structural stabilization. Optimized growth parameters produce dense, vertically aligned CNFs with broadband, omnidirectional absorption, averaging 99% across 300–2500 nm and 98.5% from 2500–15,000 nm. Electrical conductivity, confirmed through four-point probe measurements, supports antistatic functionality. The coatings exhibit hydrophobicity, confirmed by water contact angle measurements, providing resistance to moisture and surface contamination. When applied to optical baffles, the CNF coating reduces stray light by over 10 dB compared to conventional black anodized coatings, as verified by BRDF-based LightTools/Zemax simulations and experimental validation across multiple angles of incidence. This multifunctional coating platform offers a practical, high-performance solution for aerospace optics, energy harvesting, and thermal management systems, where broadband absorption, mechanical durability, and environmental resilience are essential.