(600a) Coating Process Regimes In Particulate Film Production by Forced Convection-Assisted Drag-Out

Brewer, D. D., University of Minnesota

Operating conditions for deposition of monolayer and bilayer particulate coatings from aqueous silica dispersions are identified in the context of a drag-out operation assisted by forced convection.  Dry film thickness, uniformity, and morphology are assessed within an operating window parameterized by the capillary number and silica dispersion weight fraction.  Three film deposition regimes with respect to the capillary number are observed: convective film deposition at low process rates, film entrainment at moderate process rates, and a thin-film transition regime at intermediate process rates.  Locally ordered particulate films of variable layering thickness, including discontinuous submonolayer or mixed submonolayer and monolayer, mixed monolayer and bilayer, and multilayer are dominant under convective deposition conditions.  A map of morphologies is presented within the capillary number – weight fraction operating window, where monolayer and mixed monolayer/bilayer films are demonstrated in the thin-film transition regime at intermediate dispersion weight fraction.  These operating maps are constructed using a model silica dispersion, and are therefore relevant to particulate coatings of other inorganic materials.