A.R. Boccaccini, 1. Zhitomirsky/ Current Opinion in Solid State and Materials Science 6(2002)251-260 achieved so far, a significant growth of r&D work in the 3. Electrolytic deposition(ELD) area of EPD processing of FGM and laminated ceramic structures is anticipated Electrolytic deposition produces thin ceramic films from solutions of metal salts and it is a relatively new technique in ceramic processing. There are several basic mechanism 2.7. Nanomaterials and nanostructures of ELD of ceramic films. Cathodic electrolytic deposition has important advantages and can be used for deposition of The synthesis and characterisation of nanostructured various oxide materials. In the cathodic electrodeposition materials and nanostructures are areas of active research. method, cathodic reactions are used to generate OH-groups The main focus of the research on nanostructured material and increase the pH at the electrode. Metal ions o is to gain basic understanding of their intriguing physical complexes, which are stable in the bulk of solutions at low and chemical properties, and EPD, with its high versatility pH, are hydrolyzed by electrogenerated base at the elec and ease of application, is revealing itself as one of the trode surface to form colloidal particles. These particles processing techniques of choice in this increasingly popu- coagulate to form cathodic ceramic deposits lar research area. For example, EPD has been used for the A comprehensive review paper covering developments growth of ceramic nanotubes and nanorods and for the in ELD of ceramic materials before 2000 has been efficient deposit of nanotubes and nanosized ceramic published by Therese and Kamath [**4] particles on different substrates [*58, 59, 60,611 Several studies have recently contributed to both the A major advantage of EpD for the fabrication of fundamental understanding of the mechanisms of ELD and nanorods and nanowires is the ability to grow large areas the practical use of ELD for various applications. The most of uniformly sized and nearly unidirectionally aligned significant advances are summarized in this section nanorods of various oxides, as described by Limmer et al [* 58]. Fig 3 shows the typical structure of TiO, nanorods 3.1. Fundamental principles of the eld process grown in a polycarbonate membrane with 200-nm diameter pores by sol-gel EPD[**581 Recent progress [**64 in the understanding of the Smeets et al. [62] have recently used EPD to incorporate mechanism of cathodic electrodeposition has come from functional nanosized particles into nanoporous glass the application of the classical DLvo theory of colloidal bodies. The main advantage of the EPD technique here is stability. Electrolyte concentration in the solutions used for that it involves lower temperatures than traditional glass ELD exceeds the flocculation values for corresponding melting, and thus components with relatively low thermal ions. Therefore colloidal particles obtained by cathodic capability can be incorporated into glass hosts, as for electrosynthesis are unstable and coagulate to form a example Cds/Se nanoparticles. A related study was con- cathodic deposit. The important recent finding is that the ducted by Subramanian et al.[63], who deposited noble formation of a ceramic deposit during ELD is caused by metal particles of Au, Pt and Ir on nanostructured titania flocculation introduced by the electrolyte **64]. The films using epd study also highlighted the importance of the electric field Although the development of EPD techniques in this electrode reactions and other factors that influence the novel area(nanomaterials and nanostructures) is in the coagulation of particles near the electrode surface. In a initial stage, results so far are encouraging and indicate recent review, novel electrochemical strategies and de- great potential for future R&D efforts velopments of cathodic electrodeposition, focusing on the Fig 3. Typical structure of TiO, nanorods grown in a membrane with 200-nm diameter pores by sol-gel EPD, as produced by Limmer et al. [58], at(A) w and(B) high magnification(micrograph courtesy of Professor G Cao, published with permission of Wiley-VCH, Weinheim,A.R. Boccaccini, I. Zhitomirsky / Current Opinion in Solid State and Materials Science 6 (2002) 251–260 255 achieved so far, a significant growth of R&D work in the 3. Electrolytic deposition (ELD) area of EPD processing of FGM and laminated ceramic structures is anticipated. Electrolytic deposition produces thin ceramic films from solutions of metal salts and it is a relatively new technique in ceramic processing. There are several basic mechanisms 2 .7. Nanomaterials and nanostructures of ELD of ceramic films. Cathodic electrolytic deposition has important advantages and can be used for deposition of The synthesis and characterisation of nanostructured various oxide materials. In the cathodic electrodeposition materials and nanostructures are areas of active research. method, cathodic reactions are used to generate OH-groups The main focus of the research on nanostructured materials and increase the pH at the electrode. Metal ions or is to gain basic understanding of their intriguing physical complexes, which are stable in the bulk of solutions at low and chemical properties, and EPD, with its high versatility pH, are hydrolyzed by electrogenerated base at the elec￾and ease of application, is revealing itself as one of the trode surface to form colloidal particles. These particles processing techniques of choice in this increasingly popu- coagulate to form cathodic ceramic deposits. lar research area. For example, EPD has been used for the A comprehensive review paper covering developments growth of ceramic nanotubes and nanorods and for the in ELD of ceramic materials before 2000 has been efficient deposit of nanotubes and nanosized ceramic published by Therese and Kamath [**4]. particles on different substrates [**58,*59,*60,61]. Several studies have recently contributed to both the A major advantage of EPD for the fabrication of fundamental understanding of the mechanisms of ELD and nanorods and nanowires is the ability to grow large areas the practical use of ELD for various applications. The most of uniformly sized and nearly unidirectionally aligned significant advances are summarized in this section. nanorods of various oxides, as described by Limmer et al. [**58]. Fig. 3 shows the typical structure of TiO nanorods 3 .1. Fundamental principles of the ELD process 2 grown in a polycarbonate membrane with 200-nm diameter pores by sol–gel EPD [**58]. Recent progress [**64] in the understanding of the Smeets et al. [62] have recently used EPD to incorporate mechanism of cathodic electrodeposition has come from functional nanosized particles into nanoporous glass the application of the classical DLVO theory of colloidal bodies. The main advantage of the EPD technique here is stability. Electrolyte concentration in the solutions used for that it involves lower temperatures than traditional glass ELD exceeds the flocculation values for corresponding melting, and thus components with relatively low thermal ions. Therefore colloidal particles obtained by cathodic capability can be incorporated into glass hosts, as for electrosynthesis are unstable and coagulate to form a example CdS/Se nanoparticles. A related study was con- cathodic deposit. The important recent finding is that the ducted by Subramanian et al. [63], who deposited noble formation of a ceramic deposit during ELD is caused by metal particles of Au, Pt and Ir on nanostructured titania flocculation introduced by the electrolyte [**64]. The films using EPD. study also highlighted the importance of the electric field, Although the development of EPD techniques in this electrode reactions and other factors that influence the novel area (nanomaterials and nanostructures) is in the coagulation of particles near the electrode surface. In a initial stage, results so far are encouraging and indicate recent review, novel electrochemical strategies and de￾great potential for future R&D efforts. velopments of cathodic electrodeposition, focusing on the Fig. 3. Typical structure of TiO nanorods grown in a membrane with 200-nm diameter pores by sol–gel EPD, as produced by Limmer et al. [**58], at (A) 2 low and (B) high magnification (micrograph courtesy of Professor G. Cao, published with permission of Wiley–VCH, Weinheim, Germany)