An alternative model for the oxidation of copper

The reaction of copper with oxygen is modeled by assuming that internal oxidation is the rate-limiting step in the reaction. This modeling successfully calculates the reaction rate without any parameters. It also calculates the profiles of the oxide layer as observed in secondary ion mass spectrometry using oxygen isotope labeling. Agreement of the rate calculations with the experimentally determined rates is excellent from 1050/degree/C down to about 80/degree/C. For this range of temperatures, the largest deviation from the experimental values is a factor of about 3. This is within the experimental scatter. In contrast, the best calculation that is obtained by the traditional product layer calculation deviates from the experimental values by a factor of about 1000. For this temperature range, the calculations and the experimental observations were compared by using the parabolic rate behavior. Below 80/degree/C, deviations are observed owing to the tendency of the oxidation to follow the rate behavior, which has been described as the ''log-law.'' It is demonstrated that the log-law behavior is not a separate mechanism from the parabolic behavior. With the described model it does not require separate mathematics. Both parabolic and log-law behaviors are calculated from the same set of equations that describemore » the internal oxidation mechanism. 35 refs., 4 figs., 3 tabs.« less