SGER: Surface Reactivity of Nanostructured Light Weight Metals

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TECHNICAL: This SGER project will examine the role of substrate microstructure on the structure and electrical characteristics of native oxide films formed under ambient temperature conditions. This examination is intended to examine the hypothesis that observed differences in surface reactivity between the nanostructured, ultra-fine grained and normal coarse grained metals arise as a result of electrochemical differences, as evidenced by variations in local surface charge, these believed to arise from differences in amorphous oxide film thickness and structure between regions of native oxide films formed immediate above high angle grain boundaries and amorphous films which are formed above the substrate at distances removed from these boundaries. Furthermore as the grain boundary surface area per unit volume increases with nanostructuring, the differences between matrix and boundaries associated surface oxide surface and charge will become of increasing importance. The primary intellectual merit of these studies resides in the attention given to understanding the immediate region and interface lying between the native oxide film and the substrate, this being at length scales between 0.5 and 2 nm, and how this nanoscale structure is affected by the substrate microstructure, in particular by the presence of grain boundaries intersecting the metal substrate. EFM and HRSEM will be used, the former within a length scale below that previously attained. Finally the results obtained within this nanoscale region will be compared with those obtained at distances far removed from substrate defect. High Risk/High Payoff: The risk resides within the length scale capabilities of the techniques used for the examination. The EFM and HRTEM procedures required will be operating at and beyond the margin previously obtained - EFM being applied at 0.5-2 nm in the vicinity of the substrate grain boundary, while HRTEM will be examining the interface and atomic structure of amorphous films approximately 0.5-1 nm thick lying on a metallic substrate. While it is expected that these limits can be obtained, other approaches including field ion microscopy and scanning probe AFM are also under consideration. NON-TECHNICAL: Success of this high risk endeavor will provide a gateway to tailoring substrate structure and chemistry to define surface charge distribution. It can be envisioned that this knowledge will lead to enhanced osteointegration, utilization of nanostructured metals for cell growth scaffolds, self-healing mitigation of cell attachment, improved corrosion resistance, and catalytic response, all without recourse to surface treatment or coatings.