| Popis: |
Atomic Force Microscopy (AFM) was used in order to investigate the crystal growth of sodalite zincophosphate (SOD-ZnPO). For the first time, in situ growth experiments studying an inorganic zeotype were performed.On the {100} face of SOD-ZnPO, an interlaced spiral growth mechanism was observed that was a consequence of a difference in condensation rates between the phosphorus and zinc species adding at the crystal edge. It was found that zinc condensation was slower, and therefore rate limiting. Growth rates on this face were found to be directly influenced by solution stoichiometry, and the importance of solution ageing was also determined. On the {111} face, the importance of extra-framework cations in the growth process was investigated. Monolayer terraces that were propagated by through-extra-framework species bonding were observed as well as bilayers that grew by through-framework bonding. That the cation assisted mechanism was observed suggested the importance of extra-framework species in the growth of nanoporous materials. Lateral Force Microscopy (LFM) was used to investigate the friction of growing terraces and step edges on the {100} face of SOD-ZnPO. On terraces, anisotopic friction was observed that was related to the anisotropic growth. It was found that scanning across rows of zinc atoms on a crystal surface caused an enhanced friction compared to scanning along rows of phosphorus, due to the different friction experienced scanning the different T units. At step edges, enhanced energy was imparted to the tip as a direct result of an increase in growth rate. This was attributed to an increase in shear strength due to increased kink density at higher growth rates. |
