A controllable fabrication of flat absorber dual-layer coating with electric shielding on 6061 aluminum alloy by PEO with nanoparticles additive

In spacecraft, thermal control coatings with anti-static functionality are vital for electronic packages to ensure proper operation of devices and instruments while preventing the reduction of component lifetime due to extreme temperatures or electrostatic discharge. However, simultaneously integrating thermal control and static charge dissipation into one coating remains a huge challenge. Herein, a dual-layer black coating composed of an Al2O3-In2O3-P2O5-SiO2 glass bottom layer embedded with crystalline indium tin oxide (ITO) and a top layer with ITO and carbon nanotubes (CNTs) as sealed conductive and radiative components grows in situ on the 6061 aluminum alloy surface using a modified PEO method with nanoparticles additive under special parameters, experiencing one-step liquid-plasma-assisted particle deposition and sintering (LPDS) process. During the LPDS process, the addition of CNTs to the electrolyte promotes the deposition and sintering of ITO nanoparticles on the bottom layer, resulting in the transition from a single-layer coating to a dual-layer coating. CNTs with high absorption/emissivity assisted further by the infrared-trapping effect of the micro/nanostructure lead to flat absorber dual-layer coating. The black coating offers both high solar absorptance (~0.93) in the 0.2–2.5 μm waveband and infrared emissivity (~0.94) in the 3–20 μm waveband. Notably, CNTs with high aspect ratio connect the ITO nanoparticles to form a complete conductive channel on the coating surface, thus eliminating in-plane charges. At only 1.27 × 102 Ω, the surface resistivity of the dual-layer coating is five orders of magnitude lower than that of the single-layer Al2O3 coating (1.15 × 107 Ω). Such an all-in-one design provides a feasible and sustainable strategy for anti-static black products in space applications.