A REVIEW OF IN-SITU ELECTRON-MICROSCOPY STUDIES OF METAL METAL OXIDE-GRAPHITE INTERACTIONS/

Controlled atmosphere electron microscopy has been used to gain a uniq ue insight into the manner by which various additives interact with ca rbonaceous solids, particularly graphite. With this technique it is po ssible to observe directly, at the nano-scale level, changes taking pl ace in the appearance of a solid while it is undergoing reaction with a gaseous environment at elevated temperature. Based on the studies of many metal/graphite-oxygen systems, a rationale has been presented to account for both the catalytic action of some additives and the inhib iting effect of others in the reaction. This experimental approach has also been applied to the investigation of the behavior of metal/graph ite systems in both hydrogen and steam. These fundamental investigatio ns have a direct impact on a number of industrially important areas, i ncluding indirect conversion of coal into liquid fuels, removal of car bon deposits from deactivated catalysts, corrosion of graphite electro des and moderators in gas-cooled nuclear reactors and the oxidation pr otection of carbon composite structures used in aerospace applications . A review of the information gained from these studies is given along with a discussion of the interfacial phenomena associated with the di fferent modes of catalytic action encountered in these reactions.