REG: X-Ray Powder Diffractometer for Characterization of Ultrafine Materials and Novel Structures

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ABSTRACT Jackie Y. Ying CTS-9411901 A X-ray powder diffractometer will be purchased and dedicated to support several research projects in the Departments of Chemical Engineering and Chemistry at Massachusetts Institute of Technology. The projects include structural tailoring of ultrafine materials generated through nanocrystalline synthesis, sol-gel processing, and pillaring of layered structures. The common theme of these programs lies in the design of nanoscale structure, which consists of nanometer-sized crystallites or two-dimensional layered structures, high volume fraction of surfaces and interfaces, and microporous network. X-ray diffractometry will be used in the identification of crystalline phases, and in the characterization of crystallite size, lattice strain, film thickness, interlayer spacing, and thermal stability. Novel nanostructures are targeted towards the following applications: (1) high activity catalysts for SO2 removal, (2) microporous molecularly mixed multicomponent catalysts for partial oxidation and hydrodesulfirization, (3) low-temperature sinterable, high strength Si3N4-based structural composites, ad (4) high permselectivity dense metallic membranes for hydrogen purification and membrane reaction. The first three projects are currently funded by NSF. The proposed diffractometer will be also used in the phase identification and structural determination of new nitrides and oxygen ion conductors. Ternary nitrides which have interesting metallic and magnetic properties will be synthesized via ammonolysis of solid state oxide precursors. Accurate structural characterization of these polycrystalline powders will be performed with X-ray Rietveld refinement. Similar structural determination is also proposed for novel layered bismuth oxides with intrinsic oxygen vacancies. They have great potential as low-temperature superionic oxygen ion conductors, which will be very useful in fuel cell and air separation technologies. Research is funded through gran ts from Division and American Chemical Society Petroleum Research Fund. ***