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The influence of glycine on the mechanism of cobalt electrodeposition on Au was studied by using different experimental techniques. From cyclic voltammetry experiments, changes in deposition kinetics were observed in the presence of glycine and as a function of pH. The early stages of deposition and the morphology of the Co films were strongly influenced by the solution pH. The electroactivity of Co(gly) + was confirmed, with slower processes related to highly coordinated cobalt ions becoming predominant with pH increase. In situ investigations were conducted at solution pH 4 and 6. The infrared spectroelectrochemical experiments showed that the concentrations of cobalt-glycine complexes increased due to changes in the interfacial pH, owing to the hydrogen evolution reaction (HER). Near-surface pH measurements during Co electrodeposition were carried out with an IrO x microelectrode, whose distance to the Au substrate was precisely controlled by using scanning electrochemical microscopy (SECM) equipment. The pH values recorded during electrodeposition were greatly influenced by the acid-base reactions of the amino acid. Although high pH values were readily reached, the accumulation of glycinate at the interface was effective at suppressing the formation of metal-hydroxide species. On the other hand, the proton-donating reactions of glycine enhanced the HER, reducing deposition efficiency. [ABSTRACT FROM AUTHOR]

High temperature oxidation behavior and associated Cr evaporation process of Co electrodeposited 22 wt.% Cr containing ferritic stainless steel designed for the SOFC interconnects was investigated using XRD and post-processed TEM compositional analysis. The electrodeposited Co layer with a thickness of 400 nm lead to a tenfold reduction in the Cr evaporation. This results from not only the prevention of direct exposure of Cr 2 O 3 to the air by Co spinel oxide formation but also the suspension of Cr transport through oxide grain boundaries due to the phase transformation of Co oxide from Co 3 O 4 to Mn x Co 3-x O 4 . [ABSTRACT FROM AUTHOR]

In the present study, WC-CoCr hard composite coatings were deposited on the hydro turbine steels using two different thermal spray techniques such as High Velocity Air Fuel (HVAF) and High Velocity Oxy Fuel (HVOF). The slurry erosion tests were performed with three different jet impingement kinetic energies and at five different impact angles. The influence of impact angle on the erosion wear behavior of the coatings was analyzed using CFD simulation technique. Erosion mechanisms were investigated in detail using SEM and laser scanning confocal microscopy. Among all the WC–CoCr coated samples, the HVAF coating sprayed at highest spray velocity has shown superior erosion resistance compared to the HVOF coatings. It could be attributed to the better adhesion, higher density, enhanced hardness and surface compressive residual stresses coupled with lower oxidation of the coated samples. The erosion wear mechanisms were found to be nearly micro-cutting and plowing with layered material removal at a lower impact angle and a low cycle fatigue linked to repeated impact leading to rounding of the edges and brittle cracking of the WC grains at normal impact conditions. [ABSTRACT FROM AUTHOR]

Reports on the electroplating of alternate layers of cobalt (Co) and copper (Cu) of individual thicknesses from an electrolyte having a low concentration of Cu and a high concentration of Co atoms. Electrodeposition technique used to prepare the Co-Cu composition modulated alloys; Investigation of the effects of surface roughness and layer interactions.

This work examines the sliding wear behaviour of nanostructured cobalt-phosphorus (Co-P) alloy electrodeposits reinforced with multiwalled carbon nanotubes (MWCNTs). Nanocrystalline cobalt-phosphorus alloy coatings reinforced with carbon nanotubes were produced by pulse electrodeposition from an aqueous bath. Tribological properties of the coatings with and without MWCNT addition were characterized. Anisotropic tribological behaviour was observed for the coatings reinforced with MWCNTs when slided against hard steel counterparts. The nanocrystalline Co-P-CNT coatings display better wear resistance and friction reduction compared with the nanocrystalline Co-P coating. The friction coefficients and wear rates of the nanocrystalline Co-P-CNT coating are influenced by the test conditions including the applied load, sliding speed and more importantly the alignment of MWCNTs in the deposits. The wear mechanisms of the nanocrystalline Co-P and Co-P-CNT alloy coatings involved in different sliding conditions are explained related to their friction and wear properties. [ABSTRACT FROM AUTHOR]

Electroless cobalt films were deposited from a neutral pH glycinate solution without additives using morpholine borane (MB) as a reducing agent. The rate of deposition rises with increase in concentration of solution components (Co ions, MB and glycine), and pH. The efficiency of cobalt discharge increases when the deposition is performed from the Co(II) complex with glycine. XPS data indicate that boron and oxygen are incorporated into the cobalt films. Two forms of boron (elemental and its oxide) were detected in the electrolessly deposited cobalt films. [ABSTRACT FROM AUTHOR]

Data are reported on the successful metallisation of cubic boron nitride by chemical reduction of solutions containing nickel and cobalt ions. The processes of growth of these two types of films differ substantially from each other. While in cobalt plating no screw-like dislocation mechanism film growth is observed, in nickel plating growth is by a screw-like dislocation mechanism. The titanium film deposited as a pretreatment on grains of cubic boron nitride does not influence the rate and structure of subsequent cobalt and nickel deposition. Thus, the metallised super-hard material obtained is useful for embedding into composite materials for the production of abrasive materials. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy was used to evaluate the oxide films formed on cobalt-coated Crofer 22 APU ferritic stainless steel after thermal oxidation at 800 °C in air for different times (i.e. 2, 50, 100 and 500 h). Impedance spectra of the oxide films exhibited two or three semicircles depending on the oxidation time, which correspond to the presence of two or three individual oxide layers. Coupled with scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD), the individual oxide layer corresponding to each semicircle was determined unambiguously. Impedance spectrum analysis of the oxide films formed on the sample after thermal exposure at 800 °C in air for 2 h led to the identification of the low-frequency and high-frequency semicircles as being from Cr2O3 and Co3O4, respectively. SEM/EDS and XRD analysis of the 500-h sample clearly revealed the presence of three oxide layers, analyzed to be Co3−x Cr x O4, CoCr2O4, and Cr2O3. Although the SEM images of the 50-h and 100-h samples did not clearly show the CoCr2O4 layer, impedance plots implied their presence. The oxide scales were assigned to their respective semicircles and the electrical properties of Co3−x Cr x O4, CoCr2O4 and Cr2O3 were determined from the impedance data. [ABSTRACT FROM AUTHOR]

Co nanowire arrays were pulse electrodeposited into nanoporous alumina templates via the dendrite pores of a thinned barrier layer formed by exponentially non-equilibrium anodization, either without or with Cu pre-plating. Electrolyte acidity (pH) dependence of the microstructure and magnetic properties of the prepared Co nanowires was investigated and compared. The process of Cu pre-plating prior to electrodeposition of Co nanowires along with an adjustment of the pH value was shown to significantly improve the magnetic properties of the Co nanowires and ultimately result in a high coercivity (about 3000 Oe) and squareness up to 98% at pH ∼ 5.7. The improvement of magnetic properties may be caused by the rotation of the hexagonal close packed c-axis of more crystal grains along with the wire axis, which supplements the shape anisotropy of the nanowires. The angular dependence of the coercivity (Hc(θ)) of both types of prepared Co nanowires was also studied. [ABSTRACT FROM AUTHOR]

Abstract: The electrodeposition of cobalt–antimony thermoelectric semiconductor films was investigated in a non-aqueous solution of ethylene glycol (EG)–CoCl2–SbCl3 at 393K. By controlling the bath composition and cathodic current density, Co–Sb alloys containing 0–94mol% of Co were obtained at 50–300 Am−2. The resistance polarization caused by the formation of semiconductor film was observed in the polarization curve measured in the EG–CoCl2–SbCl3 (90.0–9.3–0.7mol%) bath. In this bath, the Co–Sb (23.6–76.4mol%) alloy was obtained by maintaining the constant potential electrolysis at 0.1V. This alloy included CoSb3 and exhibited a p-type thermoelectric conversion by the given temperature difference. [Copyright &y& Elsevier]

Abstract: CoRuPt and CoPtRu catalysts were prepared on carbon paper (CP) using various electrochemical processes including Sn sensitization, Pd activation, Co electrodeposition and galvanic displacement. The Sn–Pd process is a surface treatment that guarantees a larger number of nucleation sites on CP for subsequent Co electrodeposition by modifying the surface to be more hydrophilic. Co particles were deposited on Sn-Pd-treated CP (SCP) by controlling deposition potential and time. Then, Pt and Ru galvanic displacements were performed on the Co particles to form CoRuPt/SCP and CoPtRu/SCP catalysts. Electrochemical measurements confirmed that the CoRuPt/SCP – 1 catalyst with a 1.02 Pt/Ru surface molar ratio showed a peak potential of 741 mV (vs. NHE) for methanol oxidation and 637 mV for carbon monoxide stripping. These values were 80 and 8 mV lower, respectively, than those of a PtRu/C commercial catalyst. [Copyright &y& Elsevier]

Abstract: ZnO has received a lot of attention in for the degradation and complete mineralization of environmental pollutants. In this study, efficient ZnO-based visible-light photocatalysts are synthesized via a low-cost method by increasing the Co concentration at the outermost surface of ZnO:Co thin film under an annealing process. The simply adjusted Co concentration gradient (≈1.5% increase) into the surface of ZnO:Co is driven by thermal diffusion. Co ions substitute Zn sites in the ZnO lattice. The band gap narrowed due to sp–d exchange interactions between the conduction band electrons and the d electrons of Co. The annealing process enhances the grain size and the degree of crystallinity of the diffused Co/ZnO:Co, which contributes to the absorption edge red-shift. Photocatalytic activities such as the photo-degradation of methylene blue and the inactivation of bacteria are obviously enhanced. The proposed low-cost method significantly increases the efficiency of ZnO for the generation of the photocatalytic effect under visible-light exposure. [Copyright &y& Elsevier]

Abstract: A comprehensive physicochemical model for cobalt deposition onto a cobalt rotating disk electrode in sulfate-borate (pH 3) solutions is derived and statistically fit to experimental EIS spectra obtained over a range of CoSO4 concentrations, overpotentials and rotation speeds. The model accounts for H+ and water reduction, homogeneous reactions and mass transport within the boundary layer. Based on a thermodynamic analysis, the species CoSO4(aq), B(OH)3(aq), B3O3(OH)4 −, H+ and OH− and two homogeneous reactions (B(OH)3(aq) hydrolysis and water dissociation) are included in the model. Kinetic and transport parameters are estimated by minimizing the sum-of-squares error between the model and experimental measurements using a simplex method. The electrode response is affected most strongly by parameters associated with the first step of Co(II) reduction, reflecting its control of the rate of Co deposition, and is moderately sensitive to the parameters for H+ reduction and the Co(II) diffusion coefficient. Water reduction is found not to occur to any significant extent under the conditions studied. These trends are consistent with that obtained by fitting equivalent electrical circuits to the experimental spectra. The simplest circuit that best fits the data consists of two RQ elements (resistor-constant phase element) in parallel or series with the solution resistance. [Copyright &y& Elsevier]

Cobalt-phosphorous (Co-P) was coated in alkaline solution on the E-glass fiber/fabric over a range of coating time (0-30 minutes, in intervals of 5 minutes) and temperature (50-90°C, in intervals of 10°C). The effects of coating time and temperature on the structural, compositional, morphological, thermal and magnetic properties of Co-P coated glass fiber/fabric were investigated by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), surface area and vibrating sample magnetometer device (VSM). The X-ray diffraction studies exhibit that the intensity of cobalt (Co) peak increases with increasing the coating time and temperature. The EDAX results also reveal that the Co content is high and phosphorous (P) content is low at the higher coating time. However, the Co and P content both are high at the higher coating temperature. The surface morphology of the Co-P coated fiber/fabric was evaluated by SEM. From TGA it is evident that the Co coating increases the thermal stability of glass fiber. The magnetic properties of Co coated glass fiber increases with an increase of coating time. The bath temperature of 75°C, 15-20 minutes deposition time, pH of 8.5 and stabilizer concentration of 25 g/l are the optimum conditions to get a good and uniform coating of Co on the glass fiber. Carbon nanotubes (CNTs) were successfully coated on the Co-coated glass fiber at a temperature of 700°C by chemical vapour deposition. The CNT coated glass fiber/fabric was characterized through SEM, transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, surface area, electrical conductivity, and so forth. Finally the performance of CNT coated glass fiber was evaluated through the measurement of modulus in the composite structure. [ABSTRACT FROM AUTHOR]

Abstract: NiO/Co–P nanocomposite is prepared by an electroless cobalt plating technique. The as-prepared composite is characterized by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images reveal that the NiO particles are about 200nm in size, which are modified by Co–P nanoparticles of about 30nm. The electrochemical properties as anode materials for lithium ion batteries are examined by cyclic voltammetry (CV) and discharge–charge tests. The results show that, compared with the bare NiO without electroless cobalt plating, NiO/Co–P nanocomposite exhibits a smaller polarization and a better rate capability, which is attributed to the Co–P nanoparticles. [ABSTRACT FROM AUTHOR]

Co/Sn/Cu sandwich couples formed by electroplating were examined to investigate the interaction between Cu and Co across the Sn layer for various Sn thicknesses from 75 μm to 580 μm. At the Sn/Cu interface, both Cu6Sn5 and Cu3Sn are formed. Unlike in a binary Sn/Cu couple, Cu6Sn5 has a spiked structure for couples with a thinner Sn layer. At the Co/Sn interface, two phases, CoSn3 and (Cu,Co)6Sn5, were simultaneously observed after reaction at 200°C. Remarkably, the CoSn3 reaction layer was much thinner than that in the binary Sn/Co couple. Furthermore, only the (Cu,Co)6Sn5 phase was formed at 150°C. This finding indicates that CoSn3 growth is significantly inhibited in Co/Sn/Cu sandwich couples due to the Cu substrate. [ABSTRACT FROM AUTHOR]

The impact of plating parameters on the porosity of cobalt hard gold electrodeposited from a cyanide bath is presented. Both constant current and pulsed current deposition were studied by electrochemical and microscopy methods. As observed previously, pores tend to decorate grain boundaries, defects, and other morphology features. Focused ion beam scanning electron microscopy indicates that perhaps only a small fraction of pores seen on the surface of the ∼350 nm thick gold film extends to the electroplated Ni underlayer. The density of pores depends on morphology and current efficiency, both of which were found to vary significantly with plating conditions. Faceted surface features correlate with a higher pore density. For a similar morphology, the pore density increases with the hydrogen generation rate, estimated from current efficiency measurements. Pulse plating conditions, with relatively high peak current and frequency, result in deposits with lower porosity due to the capability of generating finer grains while influencing hydrogen evolution rates. [ABSTRACT FROM AUTHOR]

The shiny cobalt surface that sometimes occurs on sintered hardmetal, and the production of complex die blanks without pressing or mechanical shaping, are Ken Brookes'' diverse themes in continuing coverage of last year''s Plansee Seminar… [Copyright &y& Elsevier]

We prepared Codoped ZnO films by the electrochemical deposition. Xray diffraction XRD, high resolution transmission microscopy HRTEM, xray photoelectron spectroscopy XPS, atomic force microscope AFM, xray absorption nearedge structure XANES, vibrating sample magnetometer VSM, optical absorption, and photoluminescence PL measurements were carried out on the samples. The results showed Co atoms substituted Zn atoms in the ZnO lattice without the formation of the impurity phase. VSM measurements showed the ferromagnetic properties for the Codoped ZnO samples. When the Co doping concentration increased, the band gaps were widened and the PL peak positions shifted towards the short wavelength direction. © 2009 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of Co2S3 layers deposited on glassy carbon and ABS plastic from colloidal Co(III) compound solution was investigated by cyclic voltammetry and X-ray photoelectron spectroscopy, Auger electron spectroscopy, XRD techniques in Watts Ni electroplating and Ni2+ free background electrolytes. On the basis of experimental data, it was assumed that Co2S3 converts into NiS when it is cathodically polarised at E≈-0·2 V (SHE) in the Watts electrolyte. During this process, the sheet resistance of the layer decreases from ∼3 × 109 to ∼3 × 103 ࡎ □-1. This change goes on with the direct participation of Ni2+ ions in the electrolyte and this is probably of crucial importance for the following electrodeposition of metallic Ni initiated at more negative potentials. Contrary to Cu2–xS and Bi2S3, the layer of Co2S3 cannot be electroreduced to metallic Co in the Ni2+ free background electrolyte. [ABSTRACT FROM AUTHOR]

The use of cobalt based alloys in micro-electromechanical systems (MEMS) applications seems feasible and promising as these materials are compatible with both planar and bulk technologies involved in MEMS processing. Co–Ni, Co–Mo and Co–Ni–Mo alloys can fulfil the demand for new materials in the MEMS sector especially in the magnetic actuation field. The route to obtain these alloys must take into consideration the plating bath design, the deposition parameters and the ex situ characterisation of the deposits. A continuous feedback study based on these items allows tailoring the deposit properties until deposit optimisation is achieved. This optimisation is not only focused on finding out the more appropriate mechanical and magnetic properties, but on achieving adherent, uniform, low stressed electrodeposited layers. [ABSTRACT FROM AUTHOR]

The magnetic anisotropy of sputter-deposited CoPt/AlN multilayer films has been studied in contrast with the multilayer films consisting of magnetic and noble metals. It has been found that the as-deposited multilayer film shows enhanced in-plane magnetic anisotropy compared with CoPt alloy film of equivalent thickness. However, upon thermal annealing in a vacuum, the film undergoes a smooth transition of magnetic anisotropy from in-plane to perpendicular direction; moreover, the anisotropy field and coercivity can be controlled by controlling the annealing temperature. Structural characterization has revealed that the perpendicular magnetic anisotropy of the annealed CoPt/AlN multilayer films is mainly of magnetoelastic origin. [ABSTRACT FROM AUTHOR]

Electrochemically deposited composite coatings are of interest nowadays owing to the flexibility of the deposition process and to the increasing demand for highly wear resistant composite coatings. In electrochemically deposited coatings, a second phase such as fine tough particles is incorporated in the coating matrix to improve the surface mechanical properties. In the present work, the surface mechanical behaviour of cobalt and nickel coatings with dispersion of chromium oxide in the matrix is reported. The effect of heat treatment of these coatings on the surface mechanical properties is also studied. The surface microhardness and wear loss due to rubbing abrasion are studied before and after heat treatment in the range of 100 - 600 ° C and are reported for both systems. The composite containing 12 vol.-% chromium oxide (Cr[sub 2]O[sub 3]) in a cobalt matrix and heat treated at 500 - 600 ° C was found to exhibit high abrasive resistance. This is attributed to the formation of a glass-like layer found in the cobalt matrix. The coatings are found to be highly adherent and uniform and suitable for high temperature applications. [ABSTRACT FROM AUTHOR]

Flowery assembly of hexagonal close-packed (hcp) cobalt nanoplatelets was fabricated in high yield via a simple one-pot method without any surfactants. The process involved the reduction of the precursor of cobalt dimethylglyoximate with hydrazine in a basic medium. Thus-prepared cobalt flowers exhibited a ferromagnetic characteristic with the coercivity of 308 Oe at room temperature, much higher than that of bulk counterpart. [ABSTRACT FROM AUTHOR]

Presents an abstract of the study `Oxygen Evolution on Electrochemically Generated Cobalt Spinel Coating,' by E. Potvin and L. Brossard, to be presented at the 188th Electrochemical Society Meeting on October 8-13, 1995.

Presents an abstract of the study `Aging Effects of Electroless Cobalt Bath on the Microstructure of Co-P Films,' by E.E. Kalu, to be presented at the 188th Electrochemical Society Meeting on October 8-13, 1995.