SEM/TEM Study of Zeolite Crystallization

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This research program deals with understanding of the mechanisms of crystallization of molecular sieve zeolite in hydrothermal systems. Taking advantage of seeding techniques in zeolite syntheses results in somewhat larger particles, as expected and desired, but the degree of success has been limited, and the seed crystals themselves are converted into polycrystalline masses with quite irregular morphology. This ongoing project continues the zeolite synthesis research to investigate the effects of seeding zeolite crystallization systems, and to study the effects on the seed crystals themselves. While circumstantial evidence that initial breeding occurs in the seeded silicalite synthesis system has been obtained, an attempt to actually observe these by microscopic techniques is being made. An attempt is also being made to demonstrate for several zeolite systems that some of these surface-bound initial bred nuclei remain on the seed crystal surface and generate the polycrystalline masses noted above. Examination of these initial bred nuclei by scanning and transmission electron microscope is attempted. An investigation of the effects that different growth environments have on the seed crystals themselves is done by these techniques and by selected area diffraction techniques. Crystals grown using the technique of late reagent addition during a crystallization also are investigated. Lastly, zeolite crystal precipitate zeolite NaA and "Silicalite" are investigated. The crystals have potential applications in sensors and in membrane separations.