GROWTH AND STRUCTURE OF OXIDE ON SINGLE CRYSTALS OF MAGNESIUM.
CORNELL UNIV ITHACA N Y
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The kinetics of oxide film formation on the basal and prismatic planes of single crystals of high purity Mg were investigated utilizing an ultrahigh vaccum microbalance system. Experiments showed that a parabolic rate law accurately describes the film growth in an average thickness range of 50-1000 angstroms. The parabolic rate constant varies approximately as the 16 power of the oxygen pressure. The oxidation kinetics obtained by the addition of impurities of various valencies into the oxide via the metal crystal substantiate the hypothesis that the defect nature of the oxide is an equilibrium determined primarily by the formation of cation vacancies at the oxide-oxygen interface. Oxide films of 100-200 angstrom thickness were stripped from the metal and examined by electron transmission and dark field microscopy, and by selected area electron diffraction. The films were free of cracks and had a mosaic structure. The observed structure of the oxide was used to establish the validity of the cation vacancy diffusion model. Author