Availableonlineatwww.sciencedirect.com Science Direct E噩≈RS ELSEVIER Joumal of the European Ceramic Society 28(2008)1353-1367 www.elsevier.comlocate/jeurceramsoc Electrophoretic deposition: From traditional ceramics to nanotechnology Ilaria Corni, Mary P. Ryan, Aldo r boccaccini Department of Materials, Imperial College London, Prince Consort Road, London Sw7 2BP UK Available online 25 January 2008 Electrophoretic deposition(EPD)is attracting increasing interest as a materials processing technique for a wide range of technical applications This technique enables the production of unique microstructures and nanostructures as well as novel and complex material combinations in a variety of macroscopic shapes, dimensions and arrangements starting from micron-sized or nanosized particles. This review presents a comprehensive summary of relevant recent work on EPd describing the application of the technique in the processing of several traditional and advanced materials (functional and structural ceramic coatings, composite and porous materials, laminated ceramics, functionally graded materials, thin films and nanostructured 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 processing and nanotechnology. Moreover the fundamental EPD mechanisms and novel theories proposed C 2007 Elsevier Ltd. All rights reserved Keywords: Electrophoretic deposition; Films: Composites; Suspension; Fuel cells 1. Introduction EPD was discovered in 1808 by the Russian scientist Ruess and it was first used in a practical application in 1933 to deposit Electrophoretic deposition(EPD) is an electrochemical thoria particles on a platinum cathode as an emitter for elec method attracting increasing interest as a material processing tron tube applications. In the following years, e.g. until the technique -EPD is usually carried out in a two electrode early 1990s, EPD was mainly used for the processing of tra cell, as schematically shown in Fig. 1. The mechanism of elec- ditional ceramics, including enamels and porcelain, and very trophoretic deposition involves two steps. In the first step an limited work was carried on the EPD of engineering ceramics. 6 electric field is applied between two electrodes and charged par- However, in the last 15 years the interest in electrophoretic depo- ticles suspended in a suitable liquid move toward the oppositely sition as a technique to produce advanced materials has widely charged electrode(electrophoresis). In the second step the parti- increased, both in academia and in the industrial sector, and since cles accumulate at the deposition electrode and create a relatively then a wide range of new applications of EPd for processing a compact and homogeneous film(deposition ). In order to effec- variety of bulk materials and coatings has been reported.-6EPD tively apply this technique to process materials, it is essential has demonstrated the possibility to realize unique microstruc- to produce a stable suspension containing charged particles free tures and nanostructures as well as novel and complex materials to move when an electric field is applied. Therefore EPD can combinations in a variety of macroscopic shapes, dimensions <30 um particle size) or as a colloidal suspension, including the number of published scientific papers, identified searching metals, polymers, ceramics and glasses. After the deposition, the tool Web of Science by the keyword "electrophoretic depo- a heat-treatment step is normally needed to further densify the sition, from only a few papers per year in the 1970s to just under deposit and to eliminate porosity two hundred papers published in 2006 Recently, EPD has been employed for the processing of func- tional and composite ceramics, layered and functionally graded materials, thin films, high performance ceramic and composite Corresponding author. TeL. +44 2075946731: fax: +44 2075946757 coatings and biomaterials and also for the deposition of nanopar E-mail address: a boccaccini@ic ac uk(AR. Boccaccini) ticles and carbon nanotubes to produce advanced nanostructured 0955-2219/S-see front matter o 2007 Elsevier Ltd. All rights reserved.Available online at www.sciencedirect.com Journal of the European Ceramic Society 28 (2008) 1353–1367 Electrophoretic deposition: From traditional ceramics to nanotechnology Ilaria Corni, Mary P. Ryan, Aldo R. Boccaccini ∗ Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP, UK Available online 25 January 2008 Abstract Electrophoretic deposition (EPD) is attracting increasing interest as a materials processing technique for a wide range of technical applications. This technique enables the production of unique microstructures and nanostructures as well as novel and complex material combinations in a variety of macroscopic shapes, dimensions and arrangements starting from micron-sized or nanosized particles. This review presents a comprehensive summary of relevant recent work on EPD describing the application of the technique in the processing of several traditional and advanced materials (functional and structural ceramic coatings, composite and porous materials, laminated ceramics, functionally graded materials, thin films and nanostructured 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 processing and nanotechnology. Moreover the fundamental EPD mechanisms and novel theories proposed to clarify the processes involved are explained. © 2007 Elsevier Ltd. All rights reserved. Keywords: Electrophoretic deposition; Films; Composites; Suspension; Fuel cells 1. Introduction Electrophoretic deposition (EPD) is an electrochemical method attracting increasing interest as a material processing technique.1–3 EPD is usually carried out in a two electrode cell, as schematically shown in Fig. 1. The mechanism of elec￾trophoretic deposition involves two steps. In the first step an electric field is applied between two electrodes and charged par￾ticles suspended in a suitable liquid move toward the oppositely charged electrode (electrophoresis). In the second step the parti￾cles accumulate at the deposition electrode and create a relatively compact and homogeneous film (deposition). In order to effec￾tively apply this technique to process materials, it is essential to produce a stable suspension containing charged particles free to move when an electric field is applied. Therefore EPD can be applied to any solid that is available as a fine powder (e.g. <∼30m particle size) or as a colloidal suspension, including metals, polymers, ceramics and glasses. After the deposition, a heat-treatment step is normally needed to further densify the deposit and to eliminate porosity.1–5 ∗ Corresponding author. Tel.: +44 2075946731; fax: +44 2075946757. E-mail address: a.boccaccini@ic.ac.uk (A.R. Boccaccini). EPD was discovered in 1808 by the Russian scientist Ruess and it was first used in a practical application in 1933 to deposit thoria particles on a platinum cathode as an emitter for elec￾tron tube applications.1 In the following years, e.g. until the early 1990s, EPD was mainly used for the processing of tra￾ditional ceramics, including enamels and porcelain, and very limited work was carried on the EPD of engineering ceramics.6 However, in the last 15 years the interest in electrophoretic depo￾sition as a technique to produce advanced materials has widely increased, both in academia and in the industrial sector, and since then a wide range of new applications of EPD for processing a variety of bulk materials and coatings has been reported.1–6 EPD has demonstrated the possibility to realize unique microstruc￾tures and nanostructures as well as novel and complex materials combinations in a variety of macroscopic shapes, dimensions and arrangements. Fig. 2 shows the extraordinary increase of the number of published scientific papers, identified searching the tool Web of Science® by the keyword “electrophoretic depo￾sition”, from only a few papers per year in the 1970s to just under two hundred papers published in 2006. Recently, EPD has been employed for the processing of func￾tional and composite ceramics, layered and functionally graded materials, thin films, high performance ceramic and composite coatings and biomaterials and also for the deposition of nanopar￾ticles and carbon nanotubes to produce advanced nanostructured 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.12.011