Optical Properties and Radiation Stability of Polymethylphenylsiloxane Varnish Modified with SiO2 Nanoparticles

The article is focused on examining the optical properties of the polymer binder based on polymethylphenylsiloxane varnish. The varnish was modified with SiO₂ nanoparticles of various concentrations. The diffuse reflectance and transmittance spectra within 200 to 2500 nm were measured in vacuum (2·10^–6 Torr) before and after irradiation with accelerated electrons (in situ, E = 30 keV, F = 2·10¹⁶ cm⁻²). Additionally, solar absorptance was calculated and the shift in the optical absorption edge was established. The post-modification increase in reflectance has been recorded in the UV and visible regions. In the near-IR region, the reflectance coefficient was found to increase or decrease in accordance with the nanoparticles’ concentration. The irradiation of the varnish samples with electrons leads to the formation of the absorption band within 200 to 600 nm. The nanoparticle-based modification leads to the decrease in the intensity of the induced absorption band. The nanoparticle concentration values suitable for the varnish radiation stability were established. Additionally, it was confirmed that the modification of varnish with SiO₂ nanoparticles provides 1.6 fold increase in its radiation stability when exposed to radiation.