. Corni et al /Journal of the European Ceramic Society 28(2008)1353-136 tory and time-consuming trial-and-error approaches, due to the lack of available relationships linking the parameters of the EPD process to the final deposit properties. The intention of this review is to present a comprehensive summary of relevant previous work on EPD describing the appli cation of the technique in the processing of a range of traditional ⊕←由 and advanced materials, with the intention to highlight how EPD ← evolved from being a technique restricted only to traditional ceramics to become an important tool in advanced materials pro- cessing, including nanomaterials. The review is divided into two main parts. One is dedicated to briefly revise the mechanisms proposed to explain the phenomena involved in EPD(Section 2) and the other section presents an overview of EPD applications dividing them into traditional ceramics, advanced materials and nanotechnology(Section 3). Due to the availability of previ ous comprehensive review articles covering different aspects of Fig. 1. Two electrodes cell for electrophoretic deposition showing positively the theory and applications of EPD. the focus of the present harged particles in suspension migrating towards the negative electrode. article is to highlight the most recent published research in this materials.7-9 The increasing significance of this electrochemical technique in materials processing follows from its high versa- 2. Mechanisms of EPD tility for application with different materials and combinations of materials. its cost-effectiveness, simplicity, the requirement 2.1. Traditional approaches of only basic equipment and the ability to be scaled-up to large product volumes and sizes. -Moreover, compared with other The fundamental mechanisms of EPD have been largely processing methods based on the packing of particles, epd described in the literature mainly in the framework of the is able to produce uniform deposits with high microstructural Derjaguin-Landau-Verwey-Overbeek (DLvO) theory and in homogeneity, to provide adequate control of deposit thickness relation to the distortion of the particle double layer under the and to deposit coatings on a wide range of shapes and 3D com- application of a DC electric field, as discussed by Sarkar and olex and porous structures. -3.5,7,.8 he success of EPD as processing method for advanced mate- other theories(flocculation by particle accumulation, parti rials and the increasing opportunities being explored for its cle charge neutralization, electrochemical particle coagulation, application in a wide range of materials have been confirmed by electrical double layer(EDL) distortion and thinning mecha- the establishment of an international conference series dedicated nism) have been proposed to explain the particle interactions exclusively to EPD, the proceedings of the first two conferences and the kinetics Additional (held in 2002 and 2005)have been published. 0, II and modelling studies are being carried out in order to clarify Despite the numerous improvements of the EpD technique the mechanisms of deposition and the role of electrochemical nd the large range of applications achieved, there is need fo arameters on the complex interactions between solvent, part further theoretical and modelling work to gain a full and quan cles and electric field titative understanding of the mechanisms of EPD. In fact many 2.1 .1. Flocculation by particle accumulation experimental studies are presently carried out using unsatisfac- Hamaker and Verwey 3.14 observed similarities between for- mation of deposits by electrophoresis and gravitation. In fact, in both processes, the exerted by the arriving parti cles enables the particles close to the deposit to prevail over the inter-particle repulsion. Therefore the primary function of the applied electric field in EPD is to move the particles towards the a5100 electrode to accumulate. This mechanism can also explain the deposition of coatings onto membranes that are not serving as 2.1.2. Particle charge neutralization mechanism 1990 2000 Grillon et al. suggested that the charged particles are neu- tralized when they touch the electrode. This mechanism explains the deposition of single particles and monolayers electrophoretic deposition"in the open literature(Web-of-Science research- tion of powders charged by the addition of salts to the suspension Jul-2007), from 1960 until 2006 (e. g. the experiments described by Brown and Salt).However1354 I. Corni et al. / Journal of the European Ceramic Society 28 (2008) 1353–1367 Fig. 1. Two electrodes cell for electrophoretic deposition showing positively charged particles in suspension migrating towards the negative electrode. materials.7–9 The increasing significance of this electrochemical technique in materials processing follows from its high versa￾tility for application with different materials and combinations of materials, its cost-effectiveness, simplicity, the requirement of only basic equipment and the ability to be scaled-up to large product volumes and sizes.1–5 Moreover, compared with other processing methods based on the packing of particles, EPD is able to produce uniform deposits with high microstructural homogeneity, to provide adequate control of deposit thickness and to deposit coatings on a wide range of shapes and 3D com￾plex and porous structures.1–3,5,7,8 The success of EPD as processing method for advanced mate￾rials and the increasing opportunities being explored for its application in a wide range of materials have been confirmed by the establishment of an international conference series dedicated exclusively to EPD, the proceedings of the first two conferences (held in 2002 and 2005) have been published.10,11 Despite the numerous improvements of the EPD technique and the large range of applications achieved, there is need for further theoretical and modelling work to gain a full and quan￾titative understanding of the mechanisms of EPD. In fact many experimental studies are presently carried out using unsatisfac￾Fig. 2. Increasing number of publications featuring as the keyword “electrophoretic deposition” in the open literature (Web-of-Science® research￾Jul-2007), from 1960 until 2006. tory and time-consuming trial-and-error approaches, due to the lack of available relationships linking the parameters of the EPD process to the final deposit properties.10,11 The intention of this review is to present a comprehensive summary of relevant previous work on EPD describing the appli￾cation of the technique in the processing of a range of traditional and advanced materials, with the intention to highlight how EPD evolved from being a technique restricted only to traditional ceramics to become an important tool in advanced materials pro￾cessing, including nanomaterials. The review is divided into two main parts. One is dedicated to briefly revise the mechanisms proposed to explain the phenomena involved in EPD (Section 2) and the other section presents an overview of EPD applications, dividing them into traditional ceramics, advanced materials and nanotechnology (Section 3). Due to the availability of previ￾ous comprehensive review articles covering different aspects of the theory and applications of EPD,1–8 the focus of the present article is to highlight the most recent published research in this rapidly expanding field. 2. Mechanisms of EPD 2.1. Traditional approaches The fundamental mechanisms of EPD have been largely described in the literature mainly in the framework of the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory and in relation to the distortion of the particle double layer under the application of a DC electric field, as discussed by Sarkar and Nicholson in their key reference in EPD.1 However, numerous other theories (flocculation by particle accumulation, parti￾cle charge neutralization, electrochemical particle coagulation, electrical double layer (EDL) distortion and thinning mecha￾nism) have been proposed to explain the particle interactions and the kinetics of deposition1–3,5,12. Additional theoretical and modelling studies are being carried out in order to clarify the mechanisms of deposition and the role of electrochemical parameters on the complex interactions between solvent, parti￾cles and electric field. 2.1.1. Flocculation by particle accumulation Hamaker and Verwey13,14 observed similarities between for￾mation of deposits by electrophoresis and gravitation. In fact, in both processes, the pressure exerted by the arriving parti￾cles enables the particles close to the deposit to prevail over the inter-particle repulsion. Therefore the primary function of the applied electric field in EPD is to move the particles towards the electrode to accumulate. This mechanism can also explain the deposition of coatings onto membranes that are not serving as electrodes. 2.1.2. Particle charge neutralization mechanism Grillon et al.15 suggested that the charged particles are neu￾tralized when they touch the electrode. This mechanism explains the deposition of single particles and monolayers and the deposi￾tion of powders charged by the addition of salts to the suspension (e.g. the experiments described by Brown and Salt16). However