*5.1.2. Electrodeposition of copper nanocomposites*

as oxides i.e. TiO2 [41, 42], Al2O3 [43], CeO2 [44, 45], ZrO2 [46], graphene oxide GO [47], carbon nanotubes CNT; Al2O3/Y2O3/CNT [48], carbides like SiC [49- 51], WC [52] and nitrides such as

The Ni-TiO2 system was selected because nickel is an industrially important coating for corrosion protection [42]. Generally the volume fraction of co-deposited particles is limited for nanoparticles and usually it is inversely proportional to their size. For example, Shao et al. [43] studied the rate of incorporation of two different sizes of Al2O3 nanoparticles (50 nm and 300 nm) into a nickel deposit. Using similar operating parameters (1000 rpm, 20 mA cm−2), it was found that the percentage volume fraction of the 300 nm Al2O3 in the nickel deposit was much higher compared to the 50 nm Al2O3. The presence of nanosized particles in a metal deposit

Ni−CeO<sup>2</sup> nanocomposite coatings were prepared by co--deposition of Ni and CeO2 nanopar‐ ticles with an average particle size of 7 nm onto pure Ni surfaces from a nickel sulphate. The as-codeposited Ni−CeO2 nanocomposite coatings showed a superior oxidation resistance compared with the electrodeposited pure Ni coating at 800 °C. The co-deposited CeO2 nanoparticles blocked the outward diffusion of nickel along the grain boundaries. However, the effects of CeO2 particles on the oxidation resistance significantly decrease at 1050 °C and 1150 °C due to the outward-volume diffusion of nickel controlling the oxidation growth

According to Zeng et al [46], increasing concentration of the CeO2 nanoparticles in the bath increased the weight percent of CeO2 particles in the nanocomposite coatings, and improved the micro- hardness, and the friction, corrosion, and wear behaviour of the coatings. However,

Ni–Al2O3–SiC hybrid composite films with an acceptable homogeneity and granular structure having 9.2 and 7.7 % vol. Al2O3 and SiC nanoparticles, respectively were developed success‐ fully by M. Masoudi et al [50]. Both micro hardness and wear resistance increased owing to dispersion and grain-refinement strengthening of nanoparticles. The oxidation resistance of the Ni–Al2O3–SiC hybrid composite coatings was measured to be approximately 41 % greater than the unreinforced Ni deposit and almost 30 % better than the Ni–Al2O3 composite coatings. Ni-SiC nanocomposite coatings were applied on AZ91 magnesium alloy from Watts bath with different SiC content. Micro-hardness of specimens was measured and the results revealed a significant enhancement: from 74 Vickers for bare AZ91 magnesium alloy to 523 Vickers for coated specimen. The obtained data showed the superior corrosion resistance for the coated

The effect of incorporation of Si3N4 particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated by Kasturibai et al. [54]. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si3N4 particle content. The corrosion potential (Ecorr) in the case of Ni–Si3N4 nano-composite had shown a negative shift, confirming the cathodic protective nature of the

excessive CeO2 nano-particle loadings were detrimental to the coating properties.

may induce changes in the crystalline structure of the metallic coating.

TiN [53] and Si3N4 [54].

12 Electrodeposition of Composite Materials

mechanism [45].

AZ91 magnesium alloy [51].

coating [54].

The conventionally used reinforcements in the Cu matrix such as oxides, carbide nanoparticles etc., have resulted in considerable improvement in the mechanical properties. Copper- TiO2 nano composites were deposited from an acidic copper sulphate bath. Due to relation of optical properties and photo responsively of TiO2 nanoparticles to nanoparticle size, surface area and morphology, optimization of these parameters in order to having efficient response have crucial importance. Good quality deposits (finer grain size and more homogeneous) were obtained at rather low pH [56].

According to Quayum et al. [57], Cu-NPs /ZnO / ITO composite film electrode has been prepared by electrodeposition of Cu nanoparticles (NPs), ZnO nanorods on indium tin oxide (ITO). Cu-NPs/ZnO composite electrode had high sensitivity and stability and showed higher catalytic current for glucose oxidation in the field of biosensors.

According to Li et al. [58], Cu/C composites were successfully fabricated by three step electrodeposition. The effects of hot pressure temperature and alloy element Fe on the interface characteristic of Cu/C composite were investigated. The addition of alloy element Fe not only improves the tensile strength and the lateral shear strength of the Cu/C composite, but also changes the interface bond type from the physical bond type to the chemical bond type.

The Cu/ZnO nanocomposite films have been synthesized by cathodic electrodeposition [59]. The SEM and TEM images reveal the formation of hexagonal two-dimensional ZnO sheets and Cu nanoparticles. The Cu/ZnO nanocomposite film showed good emission current stability.

Chrobak.et al. [60], studied both elastic and magnetic properties of the Cu+ Ni nanocomposite coatings with dispersed Ni nanopowder particles obtained by applying the electrolytic deposition method. The magnetization curves M (T) showed a superparamagnetic effect at T<50 K which depends on dispersion of magnetic particles in a nonmagnetic matrix. It was also shown that the observed decrease of the apparent Young's modulus due to an increase of coating roughness.

Pavithra et al. [61], demonstrated the synthesis of very hard Cu-Graphene composite foils by a simple, scalable and economical pulse reverse electrodeposition method with a welldesigned pulse profile. Carbon as a reinforcement material, in the form of fibres, nanotubes etc., will result in superior mechanical, electrical properties and an extremely high thermal conductivity. The improved strength of metal matrix composites is due to its excellent mechanical properties of Graphene. In addition, graphene is also shown to block dislocation motion in a nanolayered metal-graphene composites resulting in ultrahigh strength [62].
