ORIENTED GROWTH OF SILICA MOLECULAR-SIEVE CRYSTALS AS SUPPORTED FILMS

Continuous films, between 200 and 500 mum thick, built up of monocrystals of silica molecular sieves of the MFI-type on silicon [001] wafer platelets, were prepared. In the proper concentration range and with tetrapropylammonium ions (TPA+) as the template, a continuous silica gel layer was first formed on the platelet which acted as a precursor phase for the crystallization of a film of laterally oriented crystals. In the case of a mixture of TPA+ and Na+ ions, separate gel spheres were formed on the platelet resulting in a random orientation of the crystals in the film.