9704217 Hufnagel Small-angle x-ray scattering (SAXS) is one of the foremost techniques for studying the structure of materials on a scale of 1-100 nm. The ability to study materials on this scale is important both in understanding the development of the microstructure of metallic alloys, as well as for investigating the structure and dynamics of polymer solutions. The SAXS instrument is critically important to several research projects on metallic glasses, complex fluids, and polymer solutions at Johns Hopkins. Two of the primary research projects that will benefit from the SAXS instrument concern bulk metallic glasses. One of these projects seeks to develop new bulk metallic glass materials and processes through an improved understanding of the kinetics of phase separation and crystallization. The other project probes structure-property relationships in nanocrystalline composite materials, which consist of a dispersion of nanometer-scale metallic crystals in an amorphous metallic matrix. The SAXS equipment will contribute to this research by providing a means to study the nanometer-scale structure of metallic glasses, which is a critical regime in both phase transformations and micromechanical behavior. %%% Another class of materials to be examined with the SAXS instrument are soft materials such as complex fluids and polymers. Complex fluids are solutions containing surfactants, polymers, colloids or a combination of these components. The focus of this research is on the structure and dynamics of these systems. SAXS capabilities are crucial to this research program, especially for highly concentrated systems where light scattering is not applicable, The SAXS equipment will provide a means for investigating and ultimately understanding the coupling between structure and dynamics. Another area of active research is supercritical fluid-polymer solutions, where a particular interest is the conformation of polymers in such systems. Supercrit ical solvents are capable of dissolving a whole host of polymers such as fluoropolymers, random copolymers and block copolymers. The emphasis of this program will be on the structure of the polymers or supramolecular assemblies in these supercritical solvent systems. The SAXS instrument will be a powerful tool for investigating the structure of metallic alloys and polymer solutions. It will also provide a necessary adjunct to current small-angle neutron scattering (SANS) and anomalous small-angle x- ray scattering (ASAXS) investigations, which, while crucial to these programs, are limited in terms of instrument availability. ***
