Opportunities and limitations for direct crystallization of zeolite coatings on aluminium surfaces from alkaline reaction mixtures

摘要

Zeolite coatings may be very useful for a variety of applications related to separation, catalysis, sensing, heating/cooling, etc. These materials may be prepared on a variety of supports, such as metals, ceramics and silicon wafers by using different synthesis techniques. Stainless steel [1] and copper [2] have been commonly used as metal supports. Aluminum and its alloys are also very attractive as supports for many applications, due to their high strength-to-weight ratio, easy to shape in desired form and high thermal conductivity. However, aluminum is generally known to remain thermodynamically stable only in solutions with pH ranging from about 5 to 8.5. Although aluminum has corrosion resistance owing to the development of a strong adherent and continuous film on its surface on exposure to the atmosphere or aqueous solutions, when this metal gets in contact with alkaline solutions, the passive films are dissolved. This makes the formation of zeolite coatings on aluminum surfaces a rather complicated process.