*5.1.3. Electrodeposition of cobalt 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) than conventional polycrystalline Co [63].

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 compounds. The hardness increased with the yttrium content.
