Resistance of amorphous TiAlCrZrSi/polyimide high entropy alloy films to atomic oxygen erosion

Abstract

To alleviate the atomic oxygen (AO) degradation of the polyimide deployed in the low Earth orbit (LEO) environment, we fabricate a set of amorphous TiAlCrZrSi/polyimide films under various negative bias values via the 3rd generation co-filter cathode vacuum arc (C-FCVA). Our rational technical design realizes the noninterference regulation and filtration of mixed multielement plasma compositions. In addition, the atomic size difference (δ, 0.075–0.081), mixing enthalpy (ΔHmix, −48.98 to −46.84 kJ mol−1), and mixing entropy (ΔSmix, 12.83–12.91 J K−1 mol−1) are all within the range of parameters required for the formation of amorphous TiAlCrZrSi high-entropy alloys (HEAs). Moreover, the TiAlCrZrSi/polyimide (no bias) film can realize an equilibrium of AO resistance and durability (Ey = 2.02 × 10−26 cm3 atom−1), which is only 0.67 % of that calculated for pristine polyimide. This can be attributed to the excellent AO penetration barrier ability of the generated HEA oxide scales. Furthermore, the thickening of HEA films can reduce the sensitivity of residual defects to AO undercutting erosion, as discussed by the existing empirical theoretical models.