Gradient profile prediction in functionally graded materials processed by electrophoretic deposition

Electrophoretic deposition (EPD) allows the formation of plate-shaped binary functionally graded materials (FGM) by depositing from a powder suspension to which a second suspension is continuously added during the process. The deposition yield is described as a function of time and starting composition of both suspensions, resulting in a model of the EPD process that allows predicting the composition gradient in the green deposit as well as in the sintered material. The model presented enables calculation of the composition gradient in the FGM material from the starting composition of the suspensions, the EPD operating parameters and the powder-specific EPD characteristics. The powder-specific parameters, i.e. the effective charge, the electrophoretic mobility, the specific conductivity of the intermicellar liquid and the specific resistance of the deposit, incorporated in the model were experimentally determined from EPD of the individual homogeneous powder suspensions. The model was verified for the ZrO₂-Al₂O₃ system by the actual preparation and analysis of two different FGM materials. Because of the excellent correlation between the predicted and the measured concentration profiles, the described model allows to precisely engineer and design the composition profile in FGM materials produced by EPD.