This career proposal focuses on the structure of nano-scale atomic aggregates. The problem is important because embryonic clusters or particles form at the early stage of phase transformations and the cluster structure affects the phase transformation and microstructure evolution. Furthermore, metal particles are important industrial catalyst and nanoparticles are the building blocks for nanotechnology. This proposal will develop new approaches to structure characterization and atomic resolution imaging based on the new nano-area electron diffraction (NED) technique involving a nanometer-sized coherent beam of parallel electrons. NED allows diffraction patterns to be recorded from individual particles for 3-D structure determination. The results will contribute to the understanding of atomic structure in nanoparticles. In-situ capabilities will be developed using a modified analytical UHV scanning transmission electron microscope. The analytical capability will be very useful for studying alloying and phase separation in bimetallic nanoparticles. Insight about particle structure will be obtained by comparing experiment with molecular dynamics simulations. A goal of the project is to use the structural knowledge as a feedback to growth to improve the properties of the nano-particles. Materials to be studied include the model system of Ag nanoparticles and the eutectic Ag/Cu system. Later study will focus on magnetic alloys of Ag/Fe and Fe/Pt, and catalytic Pt/Ru to correlate structure with properties.
The research will be integrated with education at several levels. This project will develop novel methods that make use of a nanometer-sized coherent beam of parallel electrons to determine atomic arrangements. The technique is general, and in principle, applicable to individual macromolecules. The in-situ capabilities to be developed will be available through the Center for Microanalysis of Materials (CMM) to the broader community. Knowledge gained will be incorporated for teaching nanostructure characterization and used for outreach activities through workshops and schools. An important aspect of the project is the creation of research and education tools in the form of web-based research software and tutorials for educators who seek to incorporate nanoscience in their own curricula. The teaching materials to be developed here will also fill a gap in current materials science education by introducing students to the concept of molecular diffraction. Graduate and undergraduate researchers will be trained through hands-on workshops, conferences and collaboration on nanoscience specific projects.
