R. Dobrozemsky, Susanne Menhart, K. Buchtela:
"Residence times of water molecules on stainless steel and aluminum surfaces in vacuum and atmosphere";
Journal of Vacuum Science & Technology A, 25 (2007), 3; S. 551 - 556.

Kurzfassung englisch:
The adsorption and desorption phenomena of water molecules on stainless steel and aluminum
surfaces have been studied by means of tritium tracer technique TTT with special emphasis on
potential differences in the residence times in atmosphere and vacuum. Samples with a geometrical
surface area of about 2 cm2 have been exposed in an atmospheric environment loaded with a vapor
pressure of HTO tritium-labeled water of known specific activity, and the adsorbed amount of
water has been determined by liquid-scintillation counting technique. In previous studies it was
found that, in atmosphere, adsorbed water quantities and their reproducibility depend significantly
on the cleanliness of the surfaces. Furthermore, it was observed that desorption into atmosphere or
exchange with atmospheric humidity is a rather slow process with a few percent of the adsorbed
water molecules staying even for several days and with the water coverage versus time t
characterized approximately by a 1/ t law with 0.4. In this work, TTT measurements of water
desorption have been extended into high vacuum. HTO-covered specimens have been transferred
into a vacuum chamber soon after HTO exposure and have been kept under high vacuum for a
certain vacuum desorption time which was varied from minutes to several days. It was found that
water desorption from stainless steel and aluminum surfaces in vacuum is slower than in atmosphere
with the residual coverage again described approximately by a 1/ t law but now with 0.14
stainless steel and 0.17 Al . Water desorption rates calculated from coverage versus time are
within the range of outgassing data reported in literature, indicating that the TTT method can be a
powerful tool for the characterization of potential new vacuum materials even if just small
specimens are available.

Erstellt aus der Publikationsdatenbank der Technischen Universitšt Wien.