Oxidation of Oxygen-Free High Conductivity Copper to Cu[sub 2]O

The effect of oxygen upon the oxidation behavior of OFHC copper was studied under conditions that assured that the involved system is Cu / Cu 2 O / O 2 . Oxidation rate was correlated through use of two parallel reaction rates : ( a ) a diffusion step (resulting in a pressure sensitive parabolic constant, k p ), and ( b ) a phase boundary reaction (pressure insensitive). Application of the equation: k p = const . ( P O 2 ) 1 / n led to values for n: 950°C, n = 2.0 ; and 1000 ° C , n = 3.4 . Theoretical considerations are outlined to emphasize that surface site saturation will lead to a cessation of the increase in k p with increased oxygen pressure when the oxygen concentration and adsorption potential are sufficient to accommodate oxygen on all available sites. Photomicrographs of the growth of CuO on Cu 2 O are included.