Zeolite hybrid films for space decontamination

Abstract

A bi-layer film composed of a thick layer of ZSM-5 zeolite (MFI-structure type) and a thin layer of EMC-1 zeolite (FAU-structure type) was synthesized on aluminum alloys widely used in aerospace industry. The bottom MFI layer was obtained by direct hydrothermal synthesis while secondary growth method was used for the top FAU layer. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results revealed that both layers are highly crystallized, uniform and well-intergrown with a total film thickness around 10μm. 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 hybrid 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. The process described in this paper for the formation of a MFI/FAU bi-layer film can be easily extended to other hybrid coating film.