Cobalt, electrodeposition

At a pH above roughly 3, cobalt is deposited through a pH-dependent mechanism by the formation of a cobalt hydroxide complex (Co(OH)2 or CoOH [9, 10]. At a constant potential, the cobalt deposition current decreases with decreasing pH, indicating an increase in the inhibition of cobalt deposit. Therefore, dendrites should be suppressed at a lower pH. At a pH below roughly 3, cobalt electrodeposition occurs through the direct reduction of Co and is practically independent of pH [10]. 

O. E. Kongstein, G. M. Haarberg and J. Thonstad, Current efficiency and kinetics of cobalt electrodeposition in acid chloride solutions. Part 1 The influence of current density, pH and temperature . Journal of Applied Electrochemistray, 2>1 (2007), 669-674. 

Rios-Reyes CH, Granados-Neri M, Mendoza-Huizar LH (2009) Kinetic study of the cobalt electrodeposition onto glassy carbon electrode from ammonium sulfate solutions. Quim Nova 32 2382-2386. doi 10.1590/S0100-40422009000900028... 

The polarization curves corrected for IR drop for the processes of pure cobalt (Co), pure nickel (Ni), and Co-Ni aUoy (powders) electrodeposition from ammonium chloride-ammonium hydroxide containing supporting electrolyte are presented in Fig. 5.3 (in this case the total concentration of cations in aU investigated solutions was 0.1 M). As can be seen, cobalt electrodeposition (Co) commences at about —1.1 V, while sharp increase of current density (massive Co... 

Effect of pulsed current plating on structure and properties of gold-cobalt electrodeposits, W. Fluehmann,... 

Gold-cobalt electrodeposits— microstructure and surface topography, S. J. Harris and E. C. Darby, Gold... 

The effects of heating on the microstructure and surface topography of gold-cobalt electrodeposits, S. J. Harris, E. C. Darby, K. Bridger, and A. E. Mason, Trans. Inst. Met. Finish., 1976, 54,115. 

Solvent for Electrolytic Reactions. Dimethyl sulfoxide has been widely used as a solvent for polarographic studies and a more negative cathode potential can be used in it than in water. In DMSO, cations can be successfully reduced to metals that react with water. Thus, the following metals have been electrodeposited from their salts in DMSO cerium, actinides, iron, nickel, cobalt, and manganese as amorphous deposits zinc, cadmium, tin, and bismuth as crystalline deposits and chromium, silver, lead, copper, and titanium (96—103). Generally, no metal less noble than zinc can be deposited from DMSO. 

Wearmouth has described the production of nickel-cobalt, nickel-manganese, and nickel-chromium alloy coatings for non-decorative uses. The nickel-cobalt and nickel-manganese are electrodeposited direct from sulphamate-based solutions, the nickel-cobalt alloys offering higher hardness than the nickel-manganese alloys, which are restricted to a relatively... 

Mitchell, J. A., The Electrodeposition of Cobalt, Iron, Antimony and Their Alloys from Acidic Aluminum Chloride 1 -methyl-3-ethylimidazolium Chloride Room-Temperature Molten Salts, Ph.D. Dissertation, 1997, University of Mississippi University, MS. 

Chonglun F., Piron D.L., Paradis R, Hydrogen evolution on electrodeposited nickel-cobalt-molybdenum in alkaline water electrolysis, Electrochim. Acta, 39(18), 2715-2722,1994. 

Batley and Matousek [390,778] examined the electrodeposition of the irreversibly reduced metals cobalt, nickel, and chromium on graphite tubes for measurement by electrothermal atomisation. This method offered considerable potential for contamination-free preconcentration of heavy metals from seawater. Although only labile metal species will electrodeposit, it is likely that this fraction of the total metal could yet prove to be the most biologically important at the natural pH [779]. 

The Russell group has applied the template synthesis approach to nanoporous films generated from UV-treated PS-fo-PMMA copolymers [43, 147,233,235,241], which were pre-aligned perpendicular to the substrate by an electric field. Through direct current electrodeposition, they fabricated high-density vertical arrays of ferromagnetic cobalt nanowires (Fig. 10a) [43]. Through subsequent work, they also demonstrated the successful replication... 

Kuan-Xin, H., et ah, Electrodeposition of nickel and cobalt mixed oxide/carbon nanotube thin films and their charge storage properties. Journal of The Electrochemical Society, 2006. 153(8) p. A1568-A1574. 

A very early use of anodic alumina as a template involved colonization of the alumina by depositing nanometals in the pores [39]. Somewhat later, Kawai and Ueda templated cobalt and nickel in alumina by electrodeposition [40]. Other metals were deposited by Andersson et al. [41] and Patel et al. [42]. The use of anodic alumina as a template increased after Furneaux et al. developed a convenient voltage-reduction method for detaching the porous anodized alumina from the underlying aluminum [38]. 

It is interesting to note that Brenner and Riddell (2-4) accidentally encountered electroless deposition of nickel and cobalt during electrodeposition of nickel-tungsten and cobalt-tungsten alloys (in the presence of sodium hypophosphite) on steel tubes in order to produce material with better hardness than that of steel. They found deposition efficiency higher than 100%, which was explained by an electroless deposition contribution to the electrodeposition process. 

Although the concept of phase is well defined thermodynamically, here phase refers to a mechanically separable homogeneous part of an otherwise heterogeneous system. The concept of phase change refers here to a change in the number present or in the nature of a phase or phases as a result of an imposed condition such as temperature or pressure. To clarify and illustrate the topic at hand, we use the specific cases of electrolessly deposited nickel and electrodeposited cobalt. 

Another example of phase change is the one exhibited by electrodeposited cobalt. In this case the transformation is from fee- to hep-tj pe lattice structure as a result of hydrogen inclusion during depKJsition on the one hand and subsequent out-diffusion on the other hand. 

In Figure 17.9 the saturation GMR in Co/Cu electrodeposited multilayers with 20-A-layer cobalt and varying thickness of the Cu layers is given as obtained experimentally (6b) together with a fitted RKKY type of theoretical curve. For illustration... 

The multilayered Cu/Co systems discussed here can be grown as described next (6b). Electrolyte composition is based on a cobalt/copper ratio of 100 1 and consists of a solution of 0.34 M cobalt sulfate, 0.003 M copper sulfate, and 30g/L boric acid. The pH is fixed around 3.0, and there is no forced convection while deposition is carried out. The electrodeposition may usually be carried out potentiostatically at 45°C between —1.40 V versus SCE for the cobalt and —0.65 V versus SCE for the copper with an 3 cell potential interrupt between the cobalt-to-copper transition to avoid cobalt dissolution, which can occur when there is no interrupt. 

For the period from the beginning of 1975 to the middle of 2004, more than 750 citations pertaining either directly or peripherally to the electrodeposition of cobalt were retrieved from a literature search by means of SciFinder Scholar, but the overwhelming majority of those references were to works involving cobalt-containing alloys. Consequently, in this summary, mention is restricted to articles concerning just the deposition of... 

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