Key role of the interface gel-support in the synthesis of zeolitic coatings

The synthesis of zeolite Y on stainless steel using a seeded synthesis mixture brings new information on the initial steps of the formation of a zeolitic coating. Initially, an amorphous gel layer is deposited on the support. The modifications carried out on the interface constituted by this layer on the support induce direct Changes on the coating. The coverage and the final crystal size for instance can be tuned with the seed content. Crystal growth is thought to occur directly from the seeds present on the support. The zeolite layer is stabilized when crystals grow individually and perpendicularly to the support and bind with the surface via a hematite interface. This initial zeolite layer can then be used in a secondary growth process during which intergranular voids can be closed. To induce growth on the support, the seeds must be well dispersed in the synthesis gel. Here seeds are thought to be constituted of a preliminary local ordering of the synthesis gel in which nanoaggregates of gel are formed from the Q(0) and Q(1) silicate species.