Faujasite-type films synthesized by seeding

Thin and continuous Faujasite-type films were synthesized on a-alumina wafe rs using a seeding technique. Surface modified wafers were seeded with coll oidal zeolite Y crystals prior to film growth in a synthesis mixture. The e ffects of hydrothermal treatment on film thickness, morphology and preferre d orientation of the crystals constituting the film were investigated using scanning electron microscopy and X-ray diffraction. During hydrothermal tr eatment a precipitate formed rapidly, leaving an almost clear solution in t he upper part of the reactor. Experiments at 60-100 degrees C were performe d with the sample placed in the upper part of the synthesis solution. An in crease in the film growth rate with increasing temperature was observed. Ad sorbed seeds were shown to be oriented with the {1 1 1} pyramid, parallel t o the substrate surface. A change in the orientation with film growth was n oted, probably due to the attachment of secondary crystals to the growing f ilm surface. In one experimental series, film growth was effected at the bo ttom of the tube at 100 degrees C. Faster film growth and multilayered film s were obtained. A decrease in the film thickness after prolonged hydrother mal treatment was observed in all experimental series. This is probably due to the dissolution of the film and formation of zeolite P in the synthesis solution. The thicknesses of the films synthesized in this work are in the range of 150-2700 nm. The films are promising candidates for use in membra ne applications. (C) 2000 Elsevier Science B.V. All rights reserved.