*5.1.5. Electrodeposition of zinc nanocomposites*

Zinc deposits provide good protection to iron and steel components due to its sacrificial nature, low cost and ease of application. Nanocrystalline zinc shows improved properties such as hardness, ductility, corrosion and wear resistance. The graphene based metal materials have been widely reported that the graphene as a support material for metal nanoparticles to obtain catalytic, optoelectronic and magnetic properties. The GO sheets were reduced to be rGO sheets after electrodeposition process while Zn2+ also reduced on the surface of rGO sheets. Due to the greatly increasing in the specific surface area, the Zn/rGO film may be used as efficient catalyst for the reaction of methanol generated by carbon dioxide and hydrogen (Figure 2) [68].

*5.1.3. Electrodeposition of cobalt nanocomposites*

14 Electrodeposition of Composite Materials

than conventional polycrystalline Co [63].

compounds. The hardness increased with the yttrium content.

*5.1.4. Electrodeposition of chromium nanocomposites*

resistance of the deposited layer [65].

applications in modern industry [66].

*5.1.5. Electrodeposition of zinc nanocomposites*

Nanocrystalline cobalt and cobalt-based alloys are good candidates for the replacement of the highly toxic electroplated hexavalent chromium. They have excellent mechanical and wearresistant properties, high saturation magnetization, and good thermal stability. Nanocrystal‐ line cobalt and its alloys have higher hardness over the polycrystalline counterparts. Electrochemically prepared Co nanodeposits have three to five times higher coercivity (Hc)

Cobalt composites containing incorporated TiO2 particles are interesting materials, due to the semiconducting properties of TiO2, with applications as photocatalysts, particularly in the treatment of polluted water, but, in the same time, due to magnetic properties of Co matrix. More attention has been focused on ferromagnetism in Co-doped TiO2 anatase films, nano‐ crystals, nanorods and nanotubes, with potential applications in spintronics. The inclusion of TiO2 in a nanocomposite layer with increasing current density causes the decrease of saturation magnetization from 279.5 (a.u.) to 76.0 (a.u). Magnetic anisotropy of nanocomposite films depends on the concentration on morphology and magnetic properties of Co-TiO2 electrode‐ posited nanocomposite films [63]. According to Sivaraman et al. [64], the electrodeposited the composites exhibited a partially amorphous/nanocrystalline character, with the crystalline fractions originating from the hexagonal-close packed structure of Co. A refinement of the Co crystallite size was observed in deposits containing higher weight percentage of yttrium

Deposition of thick Cr from Cr (III) bath is cumbersome and thin Cr does not have enough wear resistance. The electrodeposition of Cr–Al2O3 nanocomposite from Cr (III) bath appears a feasible way for improvement of wear resistance, hardness, lubricity and high temperature

Cr-TiO2 nano-composites were prepared by electrodeposition. The addition of TiO2 in the coating led to improvement corrosion resistance of the composite coating as compared to the pure chromium coating. This improvement is due to the physical barriers produced by TiO2 to the corrosion process by filling crevices, gaps and micron holes on the surface of the chromium coating. This excellent corrosion resistance of the composite coatings provides wide

Juneghani et al. [67] examined Cr−SiC nanocomposite coatings with various contents of SiC nanoparticles prepared by electrodeposition in optimized Cr plating bath containing different concentrations of SiC nanoparticles. The co-deposited SiC nanoparticles are uniformly distributed into the Cr matrix which improves the corrosion and wear performance of coating.

Zinc deposits provide good protection to iron and steel components due to its sacrificial nature, low cost and ease of application. Nanocrystalline zinc shows improved properties such as

**Figure 2.** Representative SEM images of (A) Zn film and (B) Zn/rGO film. The insets are the corresponding high-reso‐ lution images [68].

Indeed, pure zinc coatings suffer from poor mechanical properties and the incorporation of a second hard phase during the electrodeposition process (e.g. ceramic nanoparticles such as ceria (Figure 3) [69], SiO2 [70] or Al2O3 [71], is of great importance.

**Figure 3.** Surface SEM image of (a) pure zinc and (b) zinc-ceria nanocomposite coatings [69].

According to Gomes et al. [72], Zn-TiO2 coatings were successfully prepared by co-deposition method. The film's surface is rough and the TiO2 agglomerates are randomly distributed on the metallic matrix formed by staked hexagonal plates oriented in different direction. These unique characteristics are essential for the thermal conversion of Zn to ZnO. The photoelectrochemical degradation of organic molecules was achieved with this type of Ti/ZnO-TiO2 photoanodes (Figure 4).

**Figure 4.** FEG-SEM images for (a) as-deposited and (b) annealed Zn-TiO2 nanocomposite films [72].
