9805188 Evans This GOALI project will relate the results of quantum mechanical calculations to macroscopic adhesion measurements made on the same oxide/metal interfaces with the long range goal of understanding and improving coatings for automotive applications. Greater reliance is being placed on these coatings to serve thermomechanical functions. Functions such as thermal and abrasion protection have already been realized, but the coatings have yet to achieve their full potential because of limited basic understanding about their cohesion and adhesion. Most coatings are non-equilibrium assemblages of metals and oxides, with their interfaces exerting a dominant influence on performance. Segregants have a dramatic effect on the adhesion of such interfaces. Segregant-free interfaces are typically ductile and tough, whereas segregants of carbon, sulfur, etc. can lead to weak, brittle interfaces. The interactions that cause segregant embrittlement have yet to be clarified and understood. The research has two synergistic elements: 1) It puts in place the linkages needed to connect the physics of bond rupture with continuum level interface fracture mechanics. This would be done through a combination of measurements performed on metal/oxide interfaces relevant to coatings, in conjunction with first principles bonding calculations, coupled with crack growth simulations; and 2) The results would have direct relevance to coating technology through the laboratory and field testing conducted at GM in both their Research Laboratory and Powertrain Division. %%% The GOALI research would exploit new capabilities in first principles bonding calculations to develop a basic understanding of the adhesion of interfaces having technological importance for coatings used in the automotive industry. It would involve a collaboration between the PI and J. R. Smith of General Motors, as well as with Hutchinson (Harvard) and Ruhle (Stuttgart). The GOALI collaboration will inclu de quarterly meetings involving the industrial and academic researchers, the graduate student spending time between semesters at the GM research facility, and Dr. Smith acting as co-advisor to the graduate student. In addition, GM will provide a summer internship for an undergraduate to conduct projects at GM. This project is co- funded by the Ceramics Program of the Division on Materials Research and the Office of Multidisciplinary Activities of the Mathematical and Physical Sciences Directorate. ***
