Degradation of ECOM-1 material under electron irradiation

The impact of ionizing radiation from outer space on the materials of the outer surfaces of spacecraft (SC) leads to the degradation of their functional properties. In particular, polymer composite materials used as a thermoregulatory coating for spacecraft are subjected to high dose loads. The article investigates the changes in the spectral reflectance of samples of the ECOM-1 material as a result of a series of four stages of irradiation in vacuum with electrons with energies of 40 keV and exposure of the samples between the next radiation exposure in room conditions. EKOM-1 is a composite material based on an acrylic copolymer filled with ZnO particles, and therefore one of the channels for its degradation, especially when irradiated with medium-energy particles, is the radiation-stimulated decomposition of the ZnO molecule. To interpret the experimental results, an elementary model of accumulation and annealing of radiation defects is presented. In the elementary model proposed below, it is postulated that the rate of change in the defect concentration $n(х,t)$ is proportional to the normalized energy release function $S_{normal}(x)$ in the ECOM-1 sample under electron irradiation. The calculation results, which demonstrate the nature of the change in the concentration of color centers during irradiation, showed that the concentration of defects with the time of irradiation reaches a certain level of saturation, which depends on the intensity of irradiation. This is due to the fact that during irradiation, along with the formation of defects, their annihilation occurs, for example, due to interaction with electrons thermalized in the material. The presented model requires its development, and at present can only serve to illustrate the process of accumulation of defects in the irradiated material.