L Besra, M. Liu/ Progress in Materials Science 52(2007)1-61 1. Introduction The electrophoretic deposition(EPD)technique with a wide range of novel applications in the processing of advanced ceramic materials and coatings, has recently gained increas- ing interest both in academia and industrial sector not only because of the high versatility of its use with different materials and their combinations but also because of its cost -effec. tiveness requiring simple apparatus. Electrophoretic deposition(EPD) has been known since 1808 when the russian scientist ruess observed an electric field induced movement of clay particles in water. But the first practical use of the techniques occurred in 1933 when the deposition of thoria particles on a platinum cathode as an emitter for electron tube application was patented in USA. Although the basic phenomena involved in EPD are well known and have been the subject of extensive theoretical and experimental research, the EPD of ceramics was first studied by Hamaker [1] and only in the 1980s did the process receive attention in the field of advanced ceramics. There is general agree- ment in the scientific community that further r&d work needs to be done to develop a full, quantitative understanding of the fundamental mechanisms of EPD to optimise the working parameters for a broader use of EPD in materials processing. This paper presents a review of electrophoretic deposition and its application in various fields of processing 2. Electrophoretic deposition-definition Electrophoretic deposition(EPD) is one of the colloidal processes in ceramic produc tion and has advantages of short formation time, needs simple apparatus, little restriction of the shape of substrate, no requirement for binder burnout as the green coating contains few or no organics Compared to other advanced shaping techniques, the epd process is very versatile since it can be modified easily for a specific application. For example, depo- sition can be made on flat, cylindrical or any other shaped substrate with only minor change in electrode design and positioning. In particular, despite being a wet process, EPD offers easy control of the thickness and morphology of a deposited film through simple adjustment of the deposition time and applied potential. In EPD, charged powder particles, dispersed or suspended in a liquid medium are attracted and deposited onto a conductive substrate of opposite charge on application of a DC electric field. The term electrodeposition is often used somewhat ambiguously to refer to either electroplating or electrophoretic deposition, although it more usually refers to the former. Table 1 presents the distinction between the two processes [2] The basic difference between an electrophoretic deposition process(EPD)and an electro- lytic deposition process(ELD) is that the former is based on the suspension of particles in a solvent whereas the later is based on solution of salts, i.e., ionic species [3]. There can be two types of electrophoretic deposition depending on which electrode the deposition occurs When the particles are positively charged, the deposition happens on the cathode and the pro- cess is called cathodic electrophoretic deposition. The deposition of negatively charged par- ticles on positive electrode(anode)is termed as anodicelectrophoretic deposition. By suitable modification of the surface charge on the particles, any of the two mode of deposition is pos- ble. Fig. I presents a schematic illustration of the two electrophoretic deposition process. With regard to technological application the potential of electrophoretic deposition (EPD) as a materials processing technique is being increasingly recognised by scientists and technologists. In addition to its conventional applications in fabrication of wear1. Introduction The electrophoretic deposition (EPD) technique with a wide range of novel applications in the processing of advanced ceramic materials and coatings, has recently gained increas￾ing interest both in academia and industrial sector not only because of the high versatility of its use with different materials and their combinations but also because of its cost-effec￾tiveness requiring simple apparatus. Electrophoretic deposition (EPD) has been known since 1808 when the Russian scientist Ruess observed an electric field induced movement of clay particles in water. But the first practical use of the techniques occurred in 1933 when the deposition of thoria particles on a platinum cathode as an emitter for electron tube application was patented in USA. Although the basic phenomena involved in EPD are well known and have been the subject of extensive theoretical and experimental research, the EPD of ceramics was first studied by Hamaker [1], and only in the 1980s did the process receive attention in the field of advanced ceramics. There is general agree￾ment in the scientific community that further R&D work needs to be done to develop a full, quantitative understanding of the fundamental mechanisms of EPD to optimise the working parameters for a broader use of EPD in materials processing. This paper presents a review of electrophoretic deposition and its application in various fields of processing. 2. Electrophoretic deposition – definition Electrophoretic deposition (EPD) is one of the colloidal processes in ceramic produc￾tion and has advantages of short formation time, needs simple apparatus, little restriction of the shape of substrate, no requirement for binder burnout as the green coating contains few or no organics. Compared to other advanced shaping techniques, the EPD process is very versatile since it can be modified easily for a specific application. For example, depo￾sition can be made on flat, cylindrical or any other shaped substrate with only minor change in electrode design and positioning. In particular, despite being a wet process, EPD offers easy control of the thickness and morphology of a deposited film through simple adjustment of the deposition time and applied potential. In EPD, charged powder particles, dispersed or suspended in a liquid medium are attracted and deposited onto a conductive substrate of opposite charge on application of a DC electric field. The term ‘electrodeposition’ is often used somewhat ambiguously to refer to either electroplating or electrophoretic deposition, although it more usually refers to the former. Table 1 presents the distinction between the two processes [2]. The basic difference between an electrophoretic deposition process (EPD) and an electro￾lytic deposition process (ELD) is that the former is based on the suspension of particles in a solvent whereas the later is based on solution of salts, i.e., ionic species [3]. There can be two types of electrophoretic deposition depending on which electrode the deposition occurs. When the particles are positively charged, the deposition happens on the cathode and the pro￾cess is called cathodic electrophoretic deposition. The deposition of negatively charged par￾ticles on positive electrode (anode) is termed as anodic electrophoretic deposition. By suitable modification of the surface charge on the particles, any of the two mode of deposition is pos￾sible. Fig. 1 presents a schematic illustration of the two electrophoretic deposition process. With regard to technological application the potential of electrophoretic deposition (EPD) as a materials processing technique is being increasingly recognised by scientists and technologists. In addition to its conventional applications in fabrication of wear L. Besra, M. Liu / Progress in Materials Science 52 (2007) 1–61 3