NSF-EC Activity: Dynamics of Layered, Multifunctional Surfaces

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Abstract: 0099695 Univ. of Santa Barbara Carlos G. Levi A multidisciplinary scientific team will undertake a collaborative program to investigate the dynamics of layered, multifunctional surfaces. The focus is on coating systems that provide both thermal insulation and oxidation/corrosion protection for thermostructural components. The overarching intellectual challenge is establishing a science-based protocol for optimizing functionality while integrating thermomechanically and thermochemically disparate materials that experience large temperature extremes. These systems are inherently metastable and evolve via morphological changes, diffusional interactions and thermomechanically-induced stresses that generally degrade performance and limit durability. The program aims to develop a fundamental understanding of the underlying mechanisms that could provide a basis for designing superior, durable surfaces. The scientific themes involve phase equilibria between oxides and intermetallics, diffusive and thermal transport phenomena in oxides, fundamental mechanisms of deformation and basic mechanistic aspects of oxide growth. Specific objectives seek to elucidate (a) the role of composition on the mechanisms of surface diffusion in fluorite-structured oxides, as well as boundary diffusion in intermetallics; (b) the thermomechanical behavior of individual layers, as they relate to chemistry and microstructure, and complexities associated with their interaction; (c) the interplay between processing and material parameters via microstructural modifications; and (d) the mechanisms governing thermal transport in porous multicomponent oxides. The materials systems of interest are ceramics based on zirconia and rare earth oxides, as well as Ni-based intermetallics alloyed with platinum group metals. The synthesis technologies are predominantly vapor-based, with precursor methods and melt processing used in generating model specimens. Thermodynamic, kinetic and mechanics modeling activities will be an essential complement of the experimental activities. The program offers a balanced set of educational, scientific and technological benefits. The technological motivation derives from the drive to expand the limits and durability of structural materials, wherein durable multifunctional surfaces represent a materials challenge of highest priority. These material systems are essential to the pursuit of improved efficiency and reduced environmental impact for gas turbines, a predominant source of power for global electrification, aircraft and marine transportation, as well as numerous industrial processes. The societal and economic benefits are thus self-evident but are presently limited because of insufficient scientific understanding to guide needed improvements in materials design, processing and performance. The complexity and richness in fundamental issues associated with the dynamics of these layers provide the scientific motivation as well as the need for an interdisciplinary research approach. The team assembled has an unprecedented combination of expertise and available facilities to undertake this research. They are all closely involved in working with students and motivated by the unique educational opportunity afforded by the NSF-EC program. Accordingly, the projects will be defined to foster collaboration among American and European students. Mechanisms will be provided for extended reciprocal visits of students working together on a given topic, to experience first hand how research is done at the partner institution. By working on a broad