The method of electrophoretic deposition (EPD) is shown schematically in Fig. 3.8. A dc electric field causes the charged particles in a colloidal suspension to move toward and deposit on the oppositely charged electrode. EPD involves a combination of electrophoresis and particle deposition on the electrode. Successful EPD to form a deposit with high packing density requires a stable suspension. Agglomerated particles in an unstable suspension move toward the oppositely charged electrode and form a low-density deposit.
Kinetics and Mechanisms of Deposition
Whereas electrophoresis is well understood, the deposition mechanism of the particles on the electrode has been the subject of much controversy, and several explanations have been put forward to explain the phenomenon.
As a positively charged oxide particle with its surrounding double layer of counter ions (the lyosphere) moves towards the cathode in an EPD cell, the electric field coupled with motion of the charged particle through the liquid causes a distortion of the double-layer envelope: the envelope becomes thinner ahead of and thicker behind the particle
.