LAYERED STRUCTURE REVEALS THE CHEMISTRY BENEATH THE ZEOLITE FILMS

Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (0.3-1.2 nm in diameter). They have been widely used in catalysis, ion exchange and separation due to the inherent molecular sieving capability of zeolites. Recently, other applications of zeolites in their film forms have emerged ranging beyond the traditional use as separation membranes: from computer chips as low-k insulators, aerospace alloys as corrosion resistant coatings, to space stations as antimicrobial and hydrophilic coatings. Those novel applications are mainly motivated by some unique properties of zeolites themselves. However, the properties of the films, as a whole system, have not been taken into enough consideration in terms of their applications. Here, we present the observation of a layered structure of zeolite coatings on Al alloys. This structure is formed during the in-situ hydrothermal synthesis and explains some unique coating properties that are in conflict with the properties of zeolites themselves. At the same time, the formation of the layered structure reveals the chemistry underneath the zeolite coating, which sheds light on the corrosion protection mechanism of zeolite coating on Al alloys.Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (0.3-1.2 nm in diameter). They have been widely used in catalysis, ion exchange and separation due to the inherent molecular sieving capability of zeolites. Recently, other applications of zeolites in their film forms have emerged ranging beyond the traditional use as separation membranes: from computer chips as low-k insulators, aerospace alloys as corrosion resistant coatings, to space stations as antimicrobial and hydrophilic coatings. Those novel applications are mainly motivated by some unique properties of zeolites themselves. However, the properties of the films, as a whole system, have not been taken into enough consideration in terms of their applications. Here, we present the observation of a layered structure of zeolite coatings on Al alloys. This structure is formed during the in-situ hydrothermal synthesis and explains some unique coating properties that are in conflict with the properties of zeolites themselves. At the same time, the formation of the layered structure reveals the chemistry underneath the zeolite coating, which sheds light on the corrosion protection mechanism of zeolite coating on Al alloys