Over the past years, the synthesis of zeolite films has attracted considerable attention due to their potential applications as membranes, sensors, and insulators with low dielectric constant. Therefore, the preparation of high quality defect free zeolite films with controlled film orientation and thickness is highly desired. Silicalite-l nanocrystals were functionalised via ultrasonic treatment in alcohol (methanol, ethanol, 2-propanol and I-butanol) suspensions. The formation of methoxy groups on the external surface of silicalite-l was confirmed by nitrogen adsorption porosimetry analysis. Pressure-area Langmuir isotherms and BAM analysis confirmed the enhanced hydrophobicity of alcohol modified silicalite-l nanocrystals and film formation at the air-water interface, respectively. Silicalite-l films were successfully fabricated onto silicon substrates for the first time using the Langmuir-Blodgett (LB) method. SEM and AFM characterisations confmned that the monolayer nature of the LB films extended over an area of several mm2 • Secondary growth of the monolayers LB seeds produced smooth and continuous polycrystalline zeolite film with preferred b-orientation evidenced by XRD analysis. In addition, we have also demonstrated the synthesis of continuous and homogeneous silicalite-l films by steaming of spin-coated precursor coatings according to the SEM images. This simplified method benefits from the limited amount of structure directing template used, facile recovery of the supported films and negligible amounts of waste products. We have also shown the first successful use of synchrotron IR spectroscopy in grazing incidence mode for the characterisation of zeolite precursor LB and spin-coated films on gold-coated glass substrates. The spectra confirmed the existence of incipient zeolite nanoparticles with MFI type structure in clear silicalite-l synthesis solution. The supported LB zeolite precursor particles were used as seed layers to prepare highly crystalline and uniformly oriented silicalite-l films by secondary growth. HR-TEM images confirmed that the steamed LB precursor films were ultra-thin, < 10 nm thick but structural characterisation is required. The results confirmed the nm dimensions of the silicalite-l precursor species.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:502443 |
| Date | January 2008 |
| Creators | Wee, Lik Hong |
| Publisher | Manchester Metropolitan University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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