Synergistic Effects in a ZnO Powder-Based Coating Sequentially Irradiated with Protons, Electrons, and Solar Spectrum Quanta

Mikhail M Mikhailov,Vadim V Karanskiy,Alexey N Lapin,Semyon A Yuryev

doi:10.3390/sym12061021

Abstract

The authors investigated the changes in diffuse reflectance spectra (ρλ) within 0.32–2.1 μm and integral absorption coefficient (as) of solar irradiation for a zinc oxide powder-based coating. The latter was consequently irradiated with protons (E = 3 keV, F ≤ 1 × 1016 cm−2), solar spectrum quanta (5 eq. of solar irradiation, 1 h), electrons (E = 30 keV, F = 1 × 1016 cm−2), and—repetitively—solar spectrum quanta (5 eq. of solar irradiation, 1 h). Following the irradiation procedure, the decrease in absorption coefficient varied from 0.044 to 0.036 and from 0.062 to 0.04, respectively. Additionally, it was shown that the solar spectrum quanta did not significantly affect the coating pre-irradiated with protons or electrons and did not change the value of induced absorption in the visible region (the latter being caused by the absorption of intrinsic point defects of the zinc oxide crystal lattice). The absorption coefficient degradation decreased under solar spectrum quanta irradiation, which was determined by the decrease in the concentration of free electrons that absorbed in the near-infrared (near-IR) region. ρλ spectra were measured in high vacuum in situ. A post-irradiation transfer of a coating into the atmosphere leads not only to the complete recovery of its reflectance, but also to partial translucence in comparison with the non-irradiated state.

Highlights

In outer space (OS), various forms of radiation affect external surfaces of spacecraft (SC) either simultaneously or
Protons, 30 keV electrons, and solar spectrum quanta showed the presence of synergistic effects for the TRSO-2M coating based on zinc oxide powder
The exposure of the coating to the solar spectrum quanta leads to a decrease in the degradation of the diffuse reflectance spectra in the near-IR region because of the absorption by free electrons

Summary

Introduction

In outer space (OS), various forms of radiation affect external surfaces of spacecraft (SC) either simultaneously or . These materials can be considered as open systems. Changes in their properties are pre-determined by changes of entropy. Non-equilibrium thermodynamics is based on the entropy balance equation: dS = dS1 + dS2 , where dS1 and dS2 stand for entropy flow from external space and its production inside the system, respectively. If a negative entropy flow enters the system, it can maintain an arranged configuration.

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