Date: Thursday, Feb 9th
Presenter: Prof. David C. Johnson, Department of Chemistry, University of Oregon
We have developed a synthetic approach to new materials that uses composition control on an Angstrom length scale to control solid-state reaction pathways, leading to the self-assembly of new nanostructured compounds consisting of two or more compounds with different crystal structures that are interleaved on the nanoscale. By avoiding compounds on equilibrium phase diagrams, we have prepared hundreds of new metastable compounds with designed nanostructure, including structural isomers. Many of these materials have unprecedented physical properties, including the lowest thermal conductivities ever reported for a fully dense solid, systematic structural changes dependant on nanostructure, and unusual electrical behaviour. We believe the ability to prepare entire families of new nanostructured compounds and equilibrating them to control carrier concentrations permits a new "thin film metallurgy" or nanochemistry in which nanostructure and composition can both be used to tailor physical properties.