Elemental and chemical compositions of oxides formed at pH

Elemental and chemical surface compositions of oxides formed at pH 10 

Determination of the elemental composition of these films can now be considered, as well as consideration about their chemistries. Such analyses inevitably require that the sample be placed in a vacuum and be exposed to electron or photon radiation. On the basis of the above microscopic experiments, it is to be expected that the oxide will undergo some degree of decomposition. If volatile components such as water are the only ones removed in this process, then one 

Attempts to use scanning AES for point analyses of these films were unsuccessful. The oxygen concentration of the corrosion product was much lower than that found by XPS. probably the result of electron-beam-induced decomposition. 

SIMS studies of these same films, however, did add useful information. The film thicknesses were too low to be able to use a high-current Cs primary beam for depth profiling. An Ar beam was used instead at low currents, which would not have introduced many chemical perturbations into the film. The results of such profiling are shown in Figs. 19a-c for samples of alloy A after exposures in pH 10 solution at the corrosion potential for periods of 3, 12, and 24 h. The intensities of the oxide secondary ions NiO and CuO are shown as functions of equivalent sputter time. The depths profiled in these instances were so shallow that it was impossible to gauge them by profilometry thus only the product of sputter time and current density is given on the abscissa. As before, the RSFs for the two ions are considered to be approximately equal. 

The SIMS profiles in Fig. 19 show that, after a 3 h exposure, the depth distributions of the Cu and Ni oxides in the film seem to be the same. With increased exposure, however, there is a clear separation of them, with the region of Cu oxide located closer to the outer surface. Also, the relative concentration of Cu oxide in the film seems to increase with length of exposure. This was not 

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