Browsing by Author "Outlaw, R. A."

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    Physical interaction of nitrogen with Pyrex, stainless-steel, and nickel at very low-pressure
    Outlaw, R. A.; Brock, F. J.; Wightman, James P. (American Institute of Physics, 1974)
    The physical adsorption of nitrogen on the surfaces of Pyrex, 347 stainless steel, and polycrystallinenickel was investigated over the pressure range 1×10−12–3×10−7 Torr and for the temperatures 77.4 and 87.4 °K. The metal surfaces were prepared by vacuum firing, by chemical cleaning, and, following bakeout, by electron impact desorption (EID). Work function measurements were used to indicate changes in the surface condition following electron bombardment, and a mass spectrometer was used to monitor gas composition. The isotherms revealed that the stainless surface was very heterogeneous and that the Pyrex surface area had a roughness factor of 1.7. Nitrogen isotherms were also taken on the metal surfaces after they had been exposed to oxygen. Very little change in physical adsorption on the nickel was detected, presumably because the chemisorbed oxygen was incorporated into the bulk. The chemical adsorption of N2 on nickel at room temperature and below was not observed.
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    A study of the physical adsorption of nitrogen gas on polished 347 stainless steel at very low pressures
    Outlaw, R. A. (Virginia Polytechnic Institute, 1969)
    This investigation involves the study of the physical adsorption of nitrogen gas on a polished 347 stainless steel surface in the 1 x 10⁻⁹ to 1 x 10⁻⁷ torr pressure region. Characterization studies on the polished 347 stainless steel surface were also conducted utilizing a scanning electron microscope to determine topology and an ion microprobe mass spectrometer to determine surface composition. The stainless steel surface was cleaned in vacuo by thermal bakeout to 400° C for 48 hours. Adsorption measurements were made by employing a dynamic technique. Adsorption isotherms were constructed for temperatures of 87.7° K and 77.4° K. The data were tested for fit to the Dubinin-Radushkevich equation and found to fit reasonably well. Isoteric heats of adsorption were calculated from the analog of the Clausius-Clapeyron equation and plotted against relative coverage. These data indicated that the polished steel was a very heterogeneous surface. A roughness factor was determined to be about 70. An adsorption isotherm was also constructed for nitrogen physically adsorbed on 7740 Pyrex glass at 77.4° K. This well studied experiment was repeated in order to evaluate the vacuum system and dynamic technique used before studying the polished stainless steel. An error analysis of the dynamic technique indicated a maximum uncertainty of about ±40 percent.