. Corni et al /Journal of the European Ceramic Society 28(2008)1353-136 100ym 。Hn111175 6. Microstructure of of Al2O3 and Y-TZP, prepared by electrophoretic deposition of suspensions of Fig. 5. SEM picture of a uniform and crack-free HA tube produced by EPD each material by Ferrari et al. 104(Published with permission of Elsevier. after burning out the carbon rod substrate according to Wang et al. &4(Published with permission of Elsevier. which EPD is carried out. Developments achieved in this field up to year 2000 are reviewed by Van der Biest and heat treatment.The biocompatibility of these materials was eval- Vandeperre' and more recent progresses in FGM fabrication uated and demonstrated in vitro using a simulated body fiuid have been reported by Put et al. 95 showing the manufac (SBF). Yabutsuka et al 8s deposited wollastonite particles on ture of graded wC-Co composites using a suspension of c porous ultrahigh molecular weight polyethylene (UHMWPE) powder in acetone with variable Co powder content. Other substrates producing a composite. When this composite was significant developments achieved by the same group con- soaked in SBF for 14 days an apatite film grew from the wol- sisted of anodic co-deposition of Al2O3 and CeO2-stabilized lastonite inside the pores to the top surface of the composite. zirconia powders to produce cylindrical and tubular-shaped The apatite presented high adhesive strength to the composite Al2O3/zirconia FGM components% and the production of func probably due to an interlocking effect. This material might be tionally graded Si3N4-TiCo s Nos composites using Si3N4 as a employed for hard and soft tissue implants for its mechanical matrix and TiCo. s No s as the hard phase. Other studies on the properties and high bioactivity. EPD has been also applied to EPD production of nickel-alumina, 98 alumina-zirconia, 99-101 fabricate biodegradable polymer foams coated with bioactive Al2O3-ZrO2-Ti(C, N) 02 and hydroxyapatite- bioactive glass 103 mina membranes with uniform porous structure and suitable size Further efforts have been devoted to the devel lopment of EPD for application in microfiltration. Huang and Yang produced fabrication approaches for laminated ceramic composites uniform and dense zeolite membranes on an alumina support and particular in the system zirconia/alumina, due to the high frac Negishi et al.deposited lanthanum cobaltite on a porous alu- ture resistance of these structures. 104 As an example, a general mina tube by EPD and they were able to obtain dense membranes overview of the microstructure of Al203/Y-TZP layered com- after a sintering step. Sun et al.deposited by EPD a well- posites with 10 layers obtained by Moreno and Ferrari is adherent Y-AlO3 washcoat on metallic wire-mesh monoliths shown in fig. 6. The studies of moreno and ferrari. 104 fis- for applications in environmental catalysis and other industrial cher et al. 105 and Uchikoshi et al. 106 have been focused on catalysis process(e.g, air pollution abatement devices and auto- the optimization of EPD from aqueous suspensions for the motive emissions controls). In related applications, Yanagida et production of laminated ceramics. Water should always be pre- al. prepared a TiO2 coating on stainless steel mesh by EPD ferred over organic solvents due to environmental and economic examine the synergy effect on photocatalysis of both 1, 4-dioxane considerations. 107 In some cases however. other solvents and ethylene glycol diformate acetone, ethanol, must be used. For example You et al. reported the fabrication of SiC/TiC laminated structures by elec 3.2.3. Laminated, functionally graded and composite trophoretic deposition from acetone-based suspensions. Based materials on the promising results achieved so far, a significant growth of EPD has been employed successfully to fabricate ceramic R&D work related to the electrophoretic deposition of laminated laminates, fibre reinforced ceramic composites and functionally and functionally graded coatings is anticipated graded materials(FGMs). Laminated materials can be pro duced via EPD moving the deposition electrode to a second 3.2.4. Ceramic layers for solid oxide fuel cells suspension for deposition of a layer of different composi Numerous investigations have recently concentrated on solid on when the desired thickness of the first layer is reached. oxide fuel cells(SOFCs)as new electric power generation By changing back and forth, a layered material is readily systems. 09 The increased interest in SOFCs is due to their high obtained. Moreover FGM can also be produced using EPD by energy conversion efficiency, clean power generation, reliabil- gradually changing the composition of the suspension from ity, modularity, fuel adaptability, the fact that they are noise-free,1358 I. Corni et al. / Journal of the European Ceramic Society 28 (2008) 1353–1367 Fig. 5. SEM picture of a uniform and crack-free HA tube produced by EPD after burning out the carbon rod substrate, according to Wang et al.84 (Published with permission of Elsevier.) heat treatment. The biocompatibility of these materials was eval￾uated and demonstrated in vitro using a simulated body fluid (SBF). Yabutsuka et al.88 deposited wollastonite particles on porous ultrahigh molecular weight polyethylene (UHMWPE) substrates producing a composite. When this composite was soaked in SBF for 14 days an apatite film grew from the wol￾lastonite inside the pores to the top surface of the composite. The apatite presented high adhesive strength to the composite probably due to an interlocking effect. This material might be employed for hard and soft tissue implants for its mechanical properties and high bioactivity. EPD has been also applied to fabricate biodegradable polymer foams coated with bioactive glass particles.89 Moreover Chen et al.90 fabricated porous alu￾mina membranes with uniform porous structure and suitable size for application in microfiltration. Huang and Yang91 produced uniform and dense zeolite membranes on an alumina support and Negishi et al.92 deposited lanthanum cobaltite on a porous alu￾mina tube by EPD and they were able to obtain dense membranes after a sintering step. Sun et al.93 deposited by EPD a well￾adherent -Al2O3 washcoat on metallic wire-mesh monoliths for applications in environmental catalysis and other industrial catalysis process (e.g., air pollution abatement devices and auto￾motive emissions controls). In related applications, Yanagida et al.94 prepared a TiO2 coating on stainless steel mesh by EPD to examine the synergy effect on photocatalysis of both 1,4-dioxane and ethylene glycol diformate. 3.2.3. Laminated, functionally graded and composite materials EPD has been employed successfully to fabricate ceramic laminates, fibre reinforced ceramic composites and functionally graded materials (FGMs).1–3 Laminated materials can be pro￾duced via EPD moving the deposition electrode to a second suspension for deposition of a layer of different composi￾tion when the desired thickness of the first layer is reached. By changing back and forth, a layered material is readily obtained. Moreover FGM can also be produced using EPD by gradually changing the composition of the suspension from Fig. 6. Microstructure of a laminar material consisting of 10 alternating layers of Al2O3 and Y-TZP, prepared by electrophoretic deposition of suspensions of each material by Ferrari et al.104 (Published with permission of Elsevier.) which EPD is carried out. Developments achieved in this field up to year 2000 are reviewed by Van der Biest and Vandeperre3 and more recent progresses in FGM fabrication have been reported by Put et al.,95 showing the manufac￾ture of graded WC–Co composites using a suspension of WC powder in acetone with variable Co powder content. Other significant developments achieved by the same group con￾sisted of anodic co-deposition of Al2O3 and CeO2-stabilized zirconia powders to produce cylindrical and tubular-shaped Al2O3/zirconia FGM components96 and the production of func￾tionally graded Si3N4–TiC0.5N0.5 composites using Si3N4 as a matrix and TiC0.5N0.5 as the hard phase.97 Other studies on the EPD production of nickel–alumina,98 alumina–zirconia,99–101 Al2O3–ZrO2–Ti(C,N)102 and hydroxyapatite-bioactive glass103 FGM coatings have been successfully carried out. Further efforts have been devoted to the development of EPD fabrication approaches for laminated ceramic composites, in particular in the system zirconia/alumina, due to the high frac￾ture resistance of these structures.104 As an example, a general overview of the microstructure of Al2O3/Y-TZP layered com￾posites with 10 layers obtained by Moreno and Ferrari104 is shown in Fig. 6. The studies of Moreno and Ferrari,104 Fis￾cher et al.105 and Uchikoshi et al.106 have been focused on the optimization of EPD from aqueous suspensions for the production of laminated ceramics. Water should always be pre￾ferred over organic solvents due to environmental and economic considerations.107 In some cases, however, other solvents, e.g. acetone, ethanol, must be used. For example You et al.108 reported the fabrication of SiC/TiC laminated structures by elec￾trophoretic deposition from acetone-based suspensions. Based on the promising results achieved so far, a significant growth of R&D work related to the electrophoretic deposition of laminated and functionally graded coatings is anticipated. 3.2.4. Ceramic layers for solid oxide fuel cells Numerous investigations have recently concentrated on solid oxide fuel cells (SOFCs) as new electric power generation systems.109 The increased interest in SOFCs is due to their high energy conversion efficiency, clean power generation, reliabil￾ity, modularity, fuel adaptability, the fact that they are noise-free