GOALI: Optical Properties and Visual Appearance of Naturally Oxidized and Anodized Aluminum Surfaces

Vanderbilt University, Nashville TN

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: The focus of the proposal is upon a wide range of scientific issues related to optical properties and visual appearance of oxidized aluminum alloy surfaces. The visual appearance of aluminum alloy products (rolled sheet, extrusions) is an important problem for aluminum industry - more than half of all customer rejec-tions occur not because of inadequate mechanical and physical properties of the manufactured products, but due to the unacceptable quality of product surfaces. The problems to be addressed by this collaboration are generic to aluminum industry, but the effort to develop basic atomic-scale scientific understanding of the relevant processes goes beyond the capabilities of individual corporations. The results will be cast in a form that is usable by industrial researchers who focus on product development. The team includes partners from universities (Vanderbilt and Alabama A&M University), industry (Alcoa Inc.), and Oak Ridge National Laboratory (ORNL). Other collaborators at the Russian Academy of Sciences will also be involved. The new knowledge will provide valuable guidance to the aluminum industry to control its production techniques to achieve desirable optical properties of aluminum products, as specified by customers. This new knowledge will also be captured into modules suitable for high schools and the public by high-school teachers that will spend several summer sessions at Vanderbilt, coordinated by Vanderbilt's Center of Science Outreach. Students engaged in research, including minority students from Alabama A&M University (a historically black university) will visit and work in a national lab (ORNL) and in an industrial setting (Alcoa Technical Center). TECHNICAL DETAILS: The problem of visual appearance and overall quality of the surface (bright-ness, distinctness of image, iridescence, and coloration) is a multiscale problem, linking the atomic-scale structure and chemical composition of the surface and subsurface regions and the meso-scale surface roughness to macroscopic optical properties. Though the phenomenological optics of light scattering from rough surfaces is well developed, the atomic-, nanometer- and micron-scale mecha-nisms that affect optical properties and visual appearance of specific surfaces and the roles of surface oxides, dopants, and defects remain wide open. An interdisci-plinary team will use a combined experimental and theoretical multiscale ap-proach to unravel these issues in a systematic way and provide a scientific basis for dealing with a costly industrial problem. The problem will be addressed using a broad combination of experimental and theoretical tools such as atomic-resolution Z-contrast transmission electron microscopy, EXAFS, atomic force microscopy (AFM), scanning near-field optical microscopy (SNOM), and laser-induced break-down spectroscopy (LIBS) supplemented by first-principles theory and computer simulations. Continuous feedback between experiment and theory at different length scales and the rich database of phenomenological information provided by Alcoa scientists will aim for a cutting-edge demonstration of multiscale, industry-relevant, basic research. The proposed research provides unique opportunities for graduate students and post-doctoral associates. They will have exposure to "basic science" research that underlies industrial concerns, and simultaneously participate in joint work with researchers at Alcoa's Technical Center and at the ORNL. Students training in microscopy at ORNL will get an opportunity to work on an electron microscope with the world's highest resolution.