Electron Diffraction Studies on the Oxidation of Pure Copper and Pure Zinc Between 200° and 500°C

Previous workers identified an oxide CuO ' in addition to Cu 2 O and CuO during the oxidation of copper. Studies on pure copper, electrodeposited copper, and evaporated copper show that the extra reflections characteristic of CuO ' may be interpreted as due to an oxide of lead or zinc. These impurities, although present in trace amounts, concentrate in the surface layer during oxidation or are picked up from the surrounding atmosphere. Cu 2 O is found to be the essential oxide in the surface layer for oxidations in the temperature range of 200° to 400°C, with CuO forming during longer oxidation times at 400° and 500°C. In high vacua the CuO disappears by the solid phase reaction of copper to form Cu 2 O . These observations show that at temperatures of 200° to 500°C the cuprous ion diffuses through the Cu 2 O structure. Finch and Quarrell, in a study of the oxides formed on molten zinc and evaporated zinc films, propose an oxide pseudomorphic with zinc in that its cell is distorted slightly to match that of the underlying metal. This pseudomorphic oxide changes to the normal form at higher temperatures. The present oxidation studies using super‐pure zinc rods and evaporated zinc specimens give electron diffraction patterns of zinc and normal ZnO but no evidence for the pseudomorphic oxide.