Abstract An investigation on the oxidation of copper under an oxygen pressure of 76 mm Hgat 200-900℃ has been carried out. It is shown that, the oxidation of copper at 200-350℃ obeys a cubic law; at 400-550℃ the initial growth of the oxide layer is para-bolic, but departure from this law is evident at a later stage and the rate of oxidationbecomes increasingly smaller; in the temperature range of 600-900℃, however, the para-bolic rate law applies for the whole period of oxidation. From the results obtained be-tween 600℃ and 900℃, an activation energy of oxidation of 30,700 cal/mol has beenfound. The surface scale of copper is shown to be consisted of two layers, the outer layeris made of small-grained CuO whereas the inner one is composed of coarse-grained Cu_2Owith a somewhat open texture. From 300℃ to 550℃, the surface scaling exhibits arugged appearance, with the degree of ruggedness increasing with increased time andtemperature of oxidation. At 600℃ and 650℃, the scaling surface has been observedto be covered with rather dense CuO whiskers. Under the examination of electronmicroscope the oxide whiskers generally remain erect and straight, but a few of themappear to fall suddenly into a tangled bush under the action of the electron beam. Itwould appear that not all of the oxide whiskers are as perfect as is generally believed tobe dislocation-free single crystals. The different oxidation behaviors of copper at the different temperatures as observedare discussed in the light of surface morphology and gross defects such as cracks andcavities which may be present in the oxide layer. Moreover, on the assumption of Frank'smechanism of whisker growth, an explanation of the possibility of the presence of imper-fectly structured CuO whiskers is given.
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