The Growth of Oxide Crystallites during the Oxidation of Iron in Carbon Dioxide within the Scanning Electron Microscope

Abstract

Pure iron single crystals and polycrystalline iron sheet have been oxidised on a hot stage within the Scanning Electron Microscope (S.E.M.). The oxidant, a carbon dioxide/carbon monoxide gas mixture, was delivered to the specimen surface from a capillary tube which produced a local specimen surface pressure of up to 200 N m^-2, without significantly reducing the resolution of the S.E.M.

It is postulated that the rate controlling step for crystallite growth, at low pressure, is the dissociation of carbon dioxide at the surface, whereas at higher pressures the surface diffusion of iron is probably rate controlling. The effect of substrate orientation upon these steps is also discussed.