Experimental and numerical analysis of electrophoretic deposition on charge selective surfaces in external electric fields

Abstract

In this paper, we present chronopotentiometric results of direct current (DC) membrane electrophoretic deposition (DC-M-EPD) experiments and analyse the influence of the parameters solid concentration, particle size and electrical conductivity of colloidal fumed silica model suspensions on voltage–current curves. The expected streamline patterns are numerically modelled based on coupled mass balances, Ohmic law, Navier–Stokes and Nernst-Planck equations. The results confirm that overlimiting current condition is an obligatory condition for the formation of EPD green deposits under suitable DC-M-EPD conditions. Furthermore, micro-EPD experiments in external alternating current (AC) fields (micro-AC-EPD) using video microscopy come to the conclusion that the observed formations of microvortices are in accordance to the numerically modelled streamline patterns. Finally, the formation of AC-EPD microdeposits exhibiting a torus-like microstructure is substantially explained based on microfluidic streamline pattern analysis.

Keywords:

• Electrophoretic deposition
• AC and DC electric fields
• Heterogeneous surface charge
• Chronopotentiometry
• Numerical analysis

Acknowledgments

We would like to express our gratitude to Rolf Hempelmann and Harald Natter for the possibility of using the chronopotentiometric equipment. We are deeply indebted to Rolf Clasen whose help, stimulating suggestions, knowledge, experience and encouragement helped us in all the times of study and analysis of the project in the pre and post research period.

This paper is dedicated to Professor Rolf Clasen on the occasion of his 65th birthday.