(668f) Fabrication by Controlled Convective Assembly of Particulate Films for Membrane and Thin Film Applications

The method of convective assembly, particularly improved by controlled evaporation and substrate withdrawal, shows promise for facile assembly (``coating'') of thin particulate films. Limitations of current productivity by the method include lack of fundamental understanding of assembly dynamics at the three-phase region, which leads to difficulty in film thickness control, especially near the thin film (monolayer) limit, and lack of fundamental understanding behind orientational control over particle deposition in the case of non-spherical particles. Despite such shortcomings, the method is capable of easily producing multilayered films for use in any number of applications, for example as precursor films to separation membranes. For membrane precursors, the aim is often to make ``oriented monolayers'', i.e. a particle film as thin and complete as possible (high flux characteristics) with uniformly oriented particles (high separation characteristics). However, the technique may still be useful, as it can be shown quantitatively that resulting multilayered films from plate-like and flake-like materials do show preferential particle orientation. Especially with the development of synthesis techniques for smaller crystallites, the precursor film thickness issue may be circumvented, making the convective assembly route (of multilayered films) more attractive from the points of view of both scalability and ease, in addition to the added benefit that multilayers better ensure a more continuous (gap-free) precursor film structure.