. Corni et al Jounal of the European Ceramic Sociery 28(2008)1353-1367 Fig. 4. SEM micrographs of diamond/borosilicate glass composite coatings after sintering. These coatings have been electrophoretically co-deposited on stainless steel substrates from(a)1.5g/100 ml diamond and 1.0g/100 ml borosilicate glass in ethanol and(b)3.0 g/100 ml diamond and 1.0g/100 ml borosilicate glass in ethanol.(Published with permission of Elsevier. dispersants(citric acid and triethylamine)to be added in order to for use in gas separations, b ordered mesoporous silicate(MPS) obtain the required particle dispersion and high suspension sta- for energy-efficient adsorption systems (e.g. desiccant and bility. Novaket al +produced a firm and pore-free SiC fibre-Sic cooling systems),67 PZT coatings for embedded components or particle composite by EPD. They studied the effect of suspension for optical switches, 68-73 TaO N, on Ti for its catalytic activity composition on the deposition results and they observed that the in oxygen reduction reactions, yttrium silicate(YSI)coatings suspension ph, the solid loading and the particle size(micro or on C/C-Si-Sic composites for protection against oxidation at nano)have all a strong influence on the process and on the prop- high temperatures, 7 boron films and MgB2 films obtained by erties of the fresh Sic deposits. In a recent investigation, Wang heat treatment of Mg/B coatings for diffusion of the Mg into the et al. deposited smooth, uniform, dense diamond/borosilicate boron film, 76, 77 Pb-Zr-Ti-Nb-Si-O ferroelectric thick films78 glass composite coatings onto stainless steel by electrophoretic and aluminium coatings on Fe CrAl substrates. 79 Moreover, the co-deposition. They also demonstrated that is possible to control electrophoretic deposition of high-temperature superconducting the coating microstructure and composition by tailoring the EPd films with controlled thickness on substrates of various sha Ispension, in fact, for this system, the concentration ratio of the and dimensions has gained increasing interest. 8 two materials in the coating(borosilicate glass and diamond) was found to be in direct correlation with the diphasic susper 3. 2. 2. Porous materials concentration. The coatings were sintered to spread the glass EPD has been increasingly used to coat textile and porous over the diamond particle surface and to protect the diamond substrates with ceramic particles to produce a range of poro particles from oxidization or graphitization. The microstructure materials that can be applied for filters, porous carriers, bioactive of the sintered EPD coatings is shown in Fig 4 scaffolds, photocatalysis and hollow fibre fabrication. Zhito- EPD has also found successful applications in the pro- mirsky and Gal-Or 2 electrophoretically deposited submicron duction of bioactive coatings for biomedical implants and alumina and zirconia powders on carbon fibres and were able to devices. For example, the improvement of EPD for deposi- obtain hollow ceramic fibres after burning out the inner carbon tion of bioactive hydroxyapatite and related calcium phosphate core. Moreover Zhitomirsky demonstrated that hydroxyap- films on biocompatible metallic substrates(e.g. TiAl4V alloys atite(HA)coated carbon fibres can produce, after burning out and Fecralloys)u and the deposition of zirconia layers the fibrous carbon substrates, hollow HA fibres of various diam- on dental crowns and bridges have been recently reported. eters. a similar study was carried out by Wang et al.84 wh The deposition of bioactive glass and polyetheretherketone performed repeated HA deposition on carbon rod in order to (PEEK)/bioactive glass composite coatings on shape memory obtain a thick, uniform and crack-free HA film. It was observed alloy substrates has also been successfully achieved. that the uniformity of the coatings and the avoidance of cracking Some other significant recent developments include: the were the result of the repeated deposition process which fills up fabrication of BaTiO3 thick films for sensor and actuator cracks and hinders crack propagation. After burning out the car- applications, 5.36 ZnO thick films for gas sensors, MgO- bon rod a uniform and crack-free HA ceramic tube is produced, devices, S8 LiCoO2 electrodes for rechargeable lithium as sh modified Bao.6 Sro4TiO3 thick films for tunable microwave as shown in Fig. 5.84 EPD has also been applied by Maet al. >to prepare bioactive batteries, 9,0 LiNio. Mn1sO4 thick-film electrodes for use in porous hydroxyapatite(HA)scaffolds. They demonstrated that high voltage lithium-ion batteries, V2O5 microparticles for the pores were interconnected and that pore size was between cathodes for Li-secondary batteries, 62 MgO thick films for several microns and hundreds of microns. Moreover these scaf- electronics,63carbon-polytetrafluoroethylene thin films for gas folds exhibited excellent mechanical properties. Hamagami et diffusion electrodes, BaNd2 Tis O14 thick films for microwave al.86 87 studied the fabrication of highly ordered macroporous communication devices,S zeolites for supported membranes bioactive ceramic coating onto titanium by EpD followed by aI. Corni et al. / Journal of the European Ceramic Society 28 (2008) 1353–1367 1357 Fig. 4. SEM micrographs of diamond/borosilicate glass composite coatings after sintering. These coatings have been electrophoretically co-deposited on stainless steel substrates from (a) 1.5 g/100 ml diamond and 1.0 g/100 ml borosilicate glass in ethanol and (b) 3.0 g/100 ml diamond and 1.0 g/100 ml borosilicate glass in ethanol.43 (Published with permission of Elsevier.) dispersants (citric acid and triethylamine) to be added in order to obtain the required particle dispersion and high suspension sta￾bility. Novak et al.42 produced a firm and pore-free SiC fibre–SiC particle composite by EPD. They studied the effect of suspension composition on the deposition results and they observed that the suspension pH, the solid loading and the particle size (micro or nano) have all a strong influence on the process and on the prop￾erties of the fresh SiC deposits. In a recent investigation, Wang et al.43 deposited smooth, uniform, dense diamond/borosilicate￾glass composite coatings onto stainless steel by electrophoretic co-deposition. They also demonstrated that is possible to control the coating microstructure and composition by tailoring the EPD suspension, in fact, for this system, the concentration ratio of the two materials in the coating (borosilicate glass and diamond) was found to be in direct correlation with the diphasic suspension concentration. The coatings were sintered to spread the glass over the diamond particle surface and to protect the diamond particles from oxidization or graphitization. The microstructure of the sintered EPD coatings is shown in Fig. 4. EPD has also found successful applications in the pro￾duction of bioactive coatings for biomedical implants and devices. For example, the improvement of EPD for deposi￾tion of bioactive hydroxyapatite and related calcium phosphate films on biocompatible metallic substrates (e.g. TiAl4V alloys and Fecralloys)44–50 and the deposition of zirconia layers on dental crowns and bridges51 have been recently reported. The deposition of bioactive glass and polyetheretherketone (PEEK)/bioactive glass composite coatings on shape memory alloy substrates has also been successfully achieved.52–54 Some other significant recent developments include: the fabrication of BaTiO3 thick films for sensor and actuator applications,55,56 ZnO thick films for gas sensors,57 MgO￾modified Ba0.6Sr0.4TiO3 thick films for tunable microwave devices,58 LiCoO2 electrodes for rechargeable lithium batteries,59,60 LiNi0.5Mn1.5O4 thick-film electrodes for use in high voltage lithium-ion batteries,61 V2O5 microparticles for cathodes for Li-secondary batteries,62 MgO thick films for electronics,63 carbon-polytetrafluoroethylene thin films for gas diffusion electrodes,64 BaNd2Ti5O14 thick films for microwave communication devices,65 zeolites for supported membranes for use in gas separations,66 ordered mesoporous silicate (MPS) for energy-efficient adsorption systems (e.g. desiccant and cooling systems),67 PZT coatings for embedded components or for optical switches,68–73 TaOxNy on Ti for its catalytic activity in oxygen reduction reactions,74 yttrium silicate (YSI) coatings on C/C–Si–SiC composites for protection against oxidation at high temperatures,75 boron films and MgB2 films obtained by heat treatment of Mg/B coatings for diffusion of the Mg into the boron film,76,77 Pb–Zr–Ti–Nb–Si–O ferroelectric thick films78 and aluminium coatings on FeCrAl substrates.79 Moreover, the electrophoretic deposition of high-temperature superconducting films with controlled thickness on substrates of various shapes and dimensions has gained increasing interest.80,81 3.2.2. Porous materials EPD has been increasingly used to coat textile and porous substrates with ceramic particles to produce a range of porous materials that can be applied for filters, porous carriers, bioactive scaffolds, photocatalysis and hollow fibre fabrication. Zhito￾mirsky and Gal-Or82 electrophoretically deposited submicron alumina and zirconia powders on carbon fibres and were able to obtain hollow ceramic fibres after burning out the inner carbon core. Moreover Zhitomirsky83 demonstrated that hydroxyap￾atite (HA) coated carbon fibres can produce, after burning out the fibrous carbon substrates, hollow HA fibres of various diam￾eters. A similar study was carried out by Wang et al.84 who performed repeated HA deposition on carbon rod in order to obtain a thick, uniform and crack-free HA film. It was observed that the uniformity of the coatings and the avoidance of cracking were the result of the repeated deposition process which fills up cracks and hinders crack propagation. After burning out the car￾bon rod a uniform and crack-free HA ceramic tube is produced, as shown in Fig. 5. 84 EPD has also been applied by Ma et al.85 to prepare bioactive porous hydroxyapatite (HA) scaffolds. They demonstrated that the pores were interconnected and that pore size was between several microns and hundreds of microns. Moreover these scaf￾folds exhibited excellent mechanical properties. Hamagami et al.86,87 studied the fabrication of highly ordered macroporous bioactive ceramic coating onto titanium by EPD followed by a