An experimental study of the molecular O2diffusion process in high purity non-porous silicananoparticles having 50 m2/g BET specific surfaceand 20 nm average radius was carried out in thetemperature range from 127 to 177 C at O2 pressurein the range from 0.2 to 66 bar. The study wasperformed bymeasuring the volume average interstitialO2 concentration by a Raman and photoluminescencetechnique using a 1,064 nmexcitation laser to detect thesinglet to triplet emission at 1,272 nm of the molecularoxygen in silica. A dependence of the diffusion kineticson the O2 absolute pressure, in addition to temperaturedependence, was found. The kinetics can be fit by thesolution of Fick’s diffusion equation using an effectivediffusion coefficient related to temperature and O2external pressure. The fit results have evidenced that thetemperature and pressure dependencies can bedisentangled and that the pressure effects are morepronounced at lower temperatures. An Arrhenius temperaturelaw is determined for the effective diffusioncoefficient and the activation energy and pre-exponentialfactor are found in the explored experimental range.The reported findings have not been evidenced previouslyin the studies in bulk silica and could probably beoriginated by the reduced spatial extension of theconsidered system.
|Numero di pagine||6|
|Rivista||Journal of Nanoparticle Research|
|Stato di pubblicazione||Published - 2013|
All Science Journal Classification (ASJC) codes