Solar control on irradiated Ta2O5 thin film


Baydoğan N., Zayim E.

13th International Conference on Emerging Nuclear Energy Systems 2007, ICENES 2007, İstanbul, Turkey, 3 - 08 June 2007, vol.1, pp.261-281 identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 1
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.261-281
  • Keywords: Co-60, Irradiation, Sol-gel, Solar properties, Sr-90, Ta2O 5 thin films
  • Istanbul Technical University Affiliated: Yes

Abstract

Ta2O5 thin films were prepared by sol-gel prosses on Corning 2947 glass substrates to obtain good quality films. These films were placed around the source and exposed to gamma radiation at 0.35, 2.58 and 4.5 kGy absorbed dose at room temperature using Co-60 radioisotope. Ta 2O5 coated thin films were irradiated with beta radiation at 0.13 kGy using Sr-90 radioisotope. It is suggested that the mechanism of absorption is related to an allowed indirect transition at Ta2O 5 film. When the absorbed dose of Ta2O5 films increased from 0.35 kGy to 4.5 kGy the optical band gaps of Ta2O 5 films decreased from 2.40 eV to 1.63 eV 24 hours later from the irradiation proces using Co-60 radioisotope. But, the optical band gap of irradiated Ta2O5 film increased again 44 months later from the irradiation proces. The optical band gaps of irradiated Ta 2O5 film at 0.35 kGy and 4.5 kGy are detected as 2.43 eV to 1.75 eV. The effect of gamma irradiation on the solar properties of Ta 2O5 films is compared with that of beta irradiation. Using the optical properties, the redistribution of the absorbed component of the solar radiation and the shading coefficient (sc) are calculated as a function of the convective heat-transfer coefficient in order to achieve the control of solar energy. When the absorbed dose increased the shading coefficient decreased considerably. Changes in shading coefficient of irradiated Ta2O 5 films are performed 24 hours later and 44 months later from the irradiation process in order to determine post irradiation behavior of Ta 2O5 films. Shading coefficient of irradiated Ta 2O5 films increased manifestly 44 months later from the irradiaiton. The shading coefficient of the irradiated Ta2O 5 films with Sr-90 radioisotope differ significantly from irradiated Ta2O5 film with Co-60 radioisotope. Beta irradiation is more effective than gamma irradiation on the change of shading coefficient of Ta2O5 films.