Some applications of synchrotron X-ray and neutron diffraction to the crystal chemistry on microporous materials.

摘要

Synchrotron X-ray diffraction measurements were made on micro-single crystals of some Ga/Ge-containing microporous materials. The crystal structures of Ga/Ge-analogues of fibrous zeolites were at variance compared to those of aluminosilicate counterparts and revealed a new extra-framework cation position in K-GaSi-NAT, a supercell structure in RbNa-GaSi-EDI and an acentrosymetric model of Rb-GaGe-THO.; The structural model of gallosilicate TsG-1 was determined for the first time since its synthesis in 1985, and the unique pore geometry of TsG-1 suggested its potential as a selective ion exchanger.; The site-specific ion-exchange mechanism in faujasitic zeolites was investigated via in situ synchrotron X-ray powder diffraction. The results from the ex situ study formed starting models and constraints for the refinements of dynamic structural models using the in situ data.; Comparison of the ion depletion curves of the gallosilicate TsG-1 to those of mineral clinoptilolite demonstrated that TsG-1 exhibits better performance for Sr-depletion than the well-known Sr-absorber. The extra-framework cation distribution of Sr-exchanged TsG-1 was determined using high-resolution synchrotron X-ray powder diffraction data and Rietveld refinement.; Time-resolved synchrotron X-ray powder diffraction and Rietveld refinements revealed that the extra-framework cation relocations and resulting structural transformations of Cd- and Pb-exchanged zeolite rho are water-mediated phenomena, rather than previously known temperature-driven effects. The location of water molecules in partially hydrated samples was obtained using neutron diffraction data, which was crucial in the interpretation of the observations from the in situ X-ray diffraction study. In situ gas-sorption experiments suggested that the role of water molecule on the structural changes in rho is unique among other sorbates such as Kr, Co and methanol.; Location of CFC-13 molecules sorbed in the pores of faujasitic zeolites was investigated using the combination of low-temperature X-ray and neutron diffraction. Time-resolved synchrotron X-ray powder diffraction data were used to model the changes in the extra-framework cation distribution and the resulting symmetry change in an aluminogermanate analogue of gismondine.; The compressibility of RHO was measured as a function of the ions occupying the channel system up to 3.0 GPa using a diamond-anvil cell and a 200μm-focused monochromatic synchrotron X-radiation. (Abstract shortened by UMI.)