Optimal of black anti-static AZO/Al2O3-SiO2-VxOy coatings for spacecraft stray light on high silicon aluminum alloys

Abstract

It is still challenging to prepare an anti-static and anti-stray astigmatism coating on the high silicon aluminum alloy (>50 wt% Si, Al-50Si) for space material under extreme environments. To address these issues, the black anti-stray light coating with enhanced conductivity on the chemical etching surface of high-silicon Al-70Si alloy were successfully fabricated by the combination of plasma electrolytic oxidation (PEO) technology and deposited aluminum doped zinc oxide (AZO) transparent conductive film by magnetron sputtering technology. The microstructures, phase, elemental compositions, light absorption performance and electrical resistivity of coatings were tested and analyzed by SEM, EDS, XRD and XPS spectroscopy. The effects of process parameters including current density and AZO sputtering times on the structure, optical and electrical properties of the film layer were systematically studied. Convection through the fixation effect in the etched Al-70Si alloy porous layer promoted the internal heat and mass transfer during PEO process which is similar to previous reported mechanism of filling of cracks and pores by nanoparticles leading to the layer densification. The PEO coating had the highest absorptivity of 0.946 and it only decreased to 0.939 after AZO sputtering, at the same time the coating has the lowest resistivity of 1.04 × 107 Ω/sq, indicating excellent anti-stray light and antistatic ability. This two-step route pave the way to improve the conductivity without compromising optical properties of PEO coating on the high silicon aluminum alloy (>50 wt% Si, Al-50Si) for space material.