SURFACE CHARACTERIZATION OF METAL PLATES EXPOSED TO ATOMIC OXYGEN IN-SPACE

The oxides formed on plates of Al, Cu, Ni, Ta, Zr and Si by exposure t o atomic oxygen in space on NASA's (National Aeronautics and Space Adm inistration) Long Duration Exposure Facility have been examined using variable angle spectroscopic ellipsometry, X-ray photoelectron spectro scopy, Fourier transform infrared spectroscopy, and Rutherford backsca ttering spectroscopy. A portion of each metallic specimen was shielded from direct exposure to space by an aluminum bar, and both the shield ed and exposed regions of each sample were analyzed. Characterization of the metal samples revealed the stoichiometry, film thickness, and d egree of porosity of the surface oxide layer for each material. The ox ide films on the exposed regions of the metal samples were as thin as 354 angstrom for Ni and as thick as 1221 angstrom for Si. The shielded portions of each plate were covered by a very thin non-porous oxide f ilm, except in the case of Cu which was thick and highly porous. The p orosity of the oxide films on the exposed regions of the samples was f ound to be negligible in the case of Si and Al and as high as 81% poro us for the Zr sample.