In Situ Microscopy and Spectroscopy Study of the Early-Stage Oxidation of Metals and Alloys

Oxidation, with effects both beneficial and deleterious, plays an enormous role in technology, from causing serious corrosion problems, to providing protection against corrosion attack. Acquiring the ability to manipulate the microscopic processes governing the surface oxidation via either controlling the reaction environment or modifying the materials has huge technological implications. However, current understanding of the microscopic processes of metal and alloy oxidation has been greatly limited by the inability of traditional experimental techniques to perform in situ measurements of the structures, chemistry, and kinetics as the reaction progresses. The work presented therefore encompasses an atomic-scale study of the reaction ranging from the initial stage of oxygen surface chemisorption to the subsequent stages of oxide nucleation and growth. These studies exploit the unique in situ capabilities of microscopy and spectroscopy to dynamically measure the surface structure and surface chemistry under a wide range of oxidation conditions, which are coordinated closely by a number of theoretical modeling techniques ranging from the first-principles calculations to continuum elastic theory for developing direct insight into the reaction mechanism, including oxygen adsorption sites, diffusion path, reaction barrier, and surface/interface effects. Due to the decisive role of the environment in determining the reaction behavior, incorporation of the temperature and pressure effect into the first-principle thermodynamics calculations allows for identifying how the interplay between thermodynamics and kinetics determines the final structure, composition, and oxidation mechanism and also provides the baseline for tailoring the structures and composition of materials to steer the reaction toward the desired direction.