Zeolite Hybrid Coatings on Metal Alloys for Chemical Resistance, Hydrophilicity and Microbiocidal Activity

Polycrystalline zeolite membranes, films, and coatings have been demonstrated to be useful in membrane separations, membrane reactors, sensors, adsorption, catalysis, low-k dielectrics, corrosion-resistant coatings, hydrophilic coatings, antimicrobial coatings, heat pumps, and thermoelectrics. For these applications pure phase zeolites are used and their application is dependent on the type of zeolite and their silicon-to-aluminum ratio. High-silica-zeolites (HSZ) are chemically resistant, thermally stable and have surface hydrophobicity. Low-silica-zeolites (LSZ) are hydrophilic, have a large ion exchange capacity and are not significantly chemically resistant. The development of a hydrophilic and ion exchangeable zeolite coating that is chemically and thermally stable is very desirable. We have developed a method to generate zeolite hybrid coatings of tunable thickness incorporating desirable features from both HSZ and LSZ species. The hybrid coating is a purely crystalline, mixed zeolite composite coating made from low-silica zeolite (zeolite Y) seed crystals imbedded in a matrix of high-silica zeolite (MFI). The LSZ-HSZ zeolite hybrid coatings functionally demonstrate features characteristically limited to pure LSZ (zeolite Y) and HSZ (MFI) coatings. The mixed zeolite phase of the hybrid coatings were confirmed by XRD and SEM. Hydrophilicity was determined by contact angle measurements. The hybrid coatings were shown to be extremely chemically resistant, readily silver ion exchangeable and microbiocidal. This zeolite hybrid coating has great utility and its function and application can be easily tuned by changing the zeolite species used to generate it.