Synthesis of MFI/EMT zeolite bi-layer films for molecular decontamination

Abstract

A bi-layer film composed of a thick layer of ZSM-5 zeolite (MFI-structure type) and a thin layer of EMC-2 zeolite (EMT-structure type) was synthesized on aluminum alloys that are used widely in aerospace industry. The bottom MFI layer was obtained by direct hydrothermal synthesis while secondary growth method was used for the top EMC-2 layer. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results revealed that both layers are highly crystallized and uniform with a total film thickness around 22μm. Nitrogen sorption measurements indicated that ZSM-5 and EMC-1 layers present an accessible porosity. The high micropore volumes lead to considerably good adsorption properties towards pollutants. Such a result was confirmed by the n-hexane sorption capacity of the bi-layer film which is identical to what is expected for a corresponding powder mixture. Adhesion of zeolite films on aluminum substrate was investigated by scratch tests which highlighted a good adhesion between the bottom layer and the support as well as between the two zeolite layers. This bi-layer film is promising for technological uses in molecular decontamination.