Some commonly used spatial industry materials were studied in order to understand their ageing in GEO environment. Among these materials, a white commercial paint was the subject of several analyses. The material was submitted to proton irradiation with a total dose equivalent at the surface to 20 years in geostationnary orbit. Several testing methods were used to characterize materials: reflectance measurements, SEM and optical observations, AC impedance and direct conductivity measurements. The first observation was a yellowing of the white paint after irradiation. This is confirmed by binocular and SEM observations with the apparition of a contrast between the non irradiated and the irradiated part of the same sample. Moreover, reflectance spectra reveal the presence of two absorption bands, one around 500 nm, coherent with the yellowing of the material, and the second one in the near infrared. Absorptivity calculations verify this tendency with Delta alphas = +0.4 at the end of the test. On another hand, by comparing AC impedance and DC conductivity measurements, it was evidenced that conductivity of the paint is decreasing after irradiation. This result is obtained by measuring the sample at ambient temperature. The effect of the temperature on the conductivity of the material was studied, and it was showed that for T > 100 degree C, the irradiated paint was more conductive than the non irradiated one. An activation energy was deduced from conductivity values: This activation energy can be correlated to the presence of neutral oxygen vacancies in the zinc oxide pigment (5) (6). These vacancies are created in the irradiated material by ionisation of vacancies with lower energy states.


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    Title :

    Evolution of thermo-optical properties and conductivity of a white space paint in geostationnary environment


    Contributors:
    Tonon, C. (author) / Lavielle, D. (author) / Le Guevel, M. (author) / Duvignacq, C. (author)


    Publication date :

    2003


    Size :

    7 Seiten, 9 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English