9306253 Williams This project explores how atomic bonding across interfaces is affected by elemental bonding. The specific technique used is charge-transfer imaging, a new microanalytical tool developed under prior NSF research. The electron energy-loss spectrum is sensitive to the bonding state. This is measured as a function of segregation phenomenon and compared to theoretical models. Changes in the spectra due to charge transfer effects are imaged directly and compared to conventional electron images of the defect structure and compositional maps of the segregant distribution. The images have sub-nanometer resolution by using the latest advances in electron energy-loss spectrometry in the field emission gun electron microscope. Metal systems under study include nickel aluminide with boron addition to improve toughness and copper with bismuth impurity, known to cause brittleness. %%% For the first time it may be possible to verify theories that purport to explain phenomena associated with grain boundary segregation. The data are valuable input to advanced computer simulations used in theoretical descriptions of bonding across interfaces. ***
