Modeling flow-based electrophoretic deposition for functionally graded materials

Abstract

Electrophoretic deposition is an industrially proven technique to create materials from colloidal suspensions using an electric field, including functionally graded materials. While typically the composition of the colloidal suspension is held constant during deposition, leading to deposits of uniform composition or distinct layers, several researchers have reported forming functionally graded materials via electrophoretic deposition by changing the composition during the deposition. This article explores electrophoretic deposition in a flow cell that allows arbitrary gradients in the deposited material to be formed by actively mixing two colloidal suspensions during deposition. Under certain combinations of flow rate and applied electric field, the morphology of the deposit strongly deviates from the desired uniform thickness to a distinct wedge shape. To understand this phenomenon and leverage it for improved designs, a multiphysics model is developed that describes the spatial-temporal colloidal transport of particles in the suspension and reveals that suspension flow rate is the key factor influencing deposit morphologies observed in the experiment. Crucially, a distinct transition is found in deposit morphology from wedge shaped to flat at a dimensionless electric Froude number of approximately 10.

Keywords

• Electrophoretic deposition
• Flow cell
• Numerical modelling
• Functionally graded materials
• Ceramics