Effects of Pressure, Temperature, and Particles Size on O2 Diffusion Dynamics in Silica Nanoparticles

The O2 diffusion process in silica nanoparticles is experimentallystudied in samples of average radius of primary particles ranging from 3.5 to 20 nmand specific surface ranging from 50 to 380 (m2/g). The investigation is done in thetemperature range from 98 to 177 °C at O2 pressure ranging from 0.2 to 66 bar bymeasuring the interstitial O2 concentration by Raman and photoluminescencetechniques. The kinetics of diffusion can be described by the Fick’s equation with aneffective diffusion coefficient depending on the temperature, O2 pressure, andparticles size. In particular, the dependence of the diffusion coefficient on thepressure and nanoparticles size is more pronounced at lower temperatures and isconnected to morphological and physical factors.