Electrolytic Bath Research Articles

Electrodeposition of Dense Tungsten Films from Molten KF-KCl-WO3 and Csf-Cscl-WO3

Tungsten metal is known for its robustness, especially high melting and boiling points and hardness. However, its hardness and brittleness make it difficult to work. Thus, electrodeposition of dense tungsten films is worth investigating. There are a number of reports on the electrodepositon of tungsten from high temperature molten salts such as fluorides, chlorides, oxides, etc. It is known that dense and coherent tungsten deposits are more easily obtained from molten fluorides compared to molten chlorides. Although good tungsten deposits can be electrodeposited from molten oxides, the operation temperature tends to be high, typically over 1123 K. One drawback of typical fluoride melts like LiF-NaF-KF is difficulty in removing the adhered molten salts by water washing because LiF and NaF have limited solubility to water.From this background, we proposed new electrolyte baths, molten KF-KCl and CsF-CsCl. Since all the components salts of KF, KCl, CsF and CsCl have large solubility to water, adhered salts to deposited films can be easily removed by water washing.First, electrodeposition of tungsten was investigated in eutectic KF–KCl melt to which WO3 was added at 923 K. Cyclic voltammograms at copper and gold electrodes indicated the deposition of tungsten metal at more negative potential than 1.55 V vs. K+/K. The effects of electrolysis conditions on the morphology of deposits were studied by changing the cathodic current density from 12.5 to100 mA cm-2. As shown in Fig.1 (a), a dense tungsten film with a thickness of approximately 20 µm was obtained on a copper substrate electrode at 12.5 mA cm−2 for 120 min. From the Raman spectra of molten KF–KCl and molten KF–KCl–WO3 at 923 K, the coordination structure of W(VI) complex ion was indicated to be fac-[WO3F3]3−.Secondly, eutectic CsF-CsCl melt was used to lower the operation temperature. After adding 2.0 mol% of WO3, the electrodeposition was investigated using copper and gold electrodes at 823-923K. As shown in Fig.1 (b), a dense and smoother tungsten film was obtained by galvanostatic electrolysis at 12.5 mA cm−2 for 120 min at 873 K. Figure 1

The Interesting Complicacy of the New Age Metallic Coatings with Carbonaceous Additives

Metallic coatings have been traditionally used to protect the underlying substrate against corrosion. Recent reports have illustrated that use of carbonaceous material such as graphene, graphene oxide, carbon nanotubes as additives in conventional coating have led to significant enhancement in the corrosion resistance behaviour of the composite coatings. In this talk, the author will discuss the evolution of microstructure, morphology, phase constitution and corrosion behaviour of electrodeposited ZnCo coatings as a function of the amounts of graphene oxide contained in them. The as-deposited ZnCo-graphene oxide composite coatings were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDS). XRD based analysis of the coatings revealed that all the coatings contained Zn phase along with intermetallic phase (Zn10. 63Co2.34). A gradual increase in the volume fraction of the intermetallic phase was observed upon graphene oxide addition. Morphological characteristics and changes in the surface roughness were studied using SEM and AFM. A compact and smooth morphology was observed for initial graphene oxide additions while a higher graphene oxide concentration produced surface cracks due to graphene oxide agglomeration in the electrolytic bath. Weight loss measurements of control sample containing only the intermetallic phase revealed that the intermetallic was more corrosion resistant. The coatings were studied using electrochemical impedance spectroscopy (EIS) in 3.5 wt. % NaCl to understand the characteristics of corrosion product layer. Corrosion current in the coatings was found to decrease for initial graphene oxide addition while for higher additions a sudden increase in corrosion rate was observed. The impermeability of the graphene oxide and a relative increase in the volume fraction of nobler intermetallic phase lead to the initial reduction in corrosion rate. While, after an optimum graphene oxide addition which yielded the lowest corrosion rate, the incorporation of agglomerated graphene oxide lead to cracks and surface defects primarily due to non-uniform deposition. The surface morphology was analyzed using SEM after they were exposed to the electroactive media (3.5 wt.% NaCl). A continuous zinc dissolution was observed in the case of pristine ZnCo coatings while formation of pits was evident for maximum graphene oxide addition. Figure 1

Electropolishing and anodization of titanium in water/ethylene glycol baths for the production of TiO2 nanotubes

A greener methodology to grow TiO2 nanotubes in a non-corrosive, low-hazard, fluoride-free ethylene glycol/water electrolytic bath is presented. Results demonstrate that the formation of nanostructures by anodization of Ti foils in NaCl solutions requires glycol/water solutions with water contents (> 50%) and moderate voltages (< 30 V). Nanotube growth was dependent on the surface characteristics; anodization performed on mechanically polished surfaces showed that randomly oriented nanotubes grow on pits while vertically oriented TiO2 nanotubes were obtained on electropolished surfaces. An electropolishing methodology was developed to obtain surfaces with submicrometer roughness that favours the growth control of vertically oriented TiO2 nanotubes.

Microstructure-Electrochemical Behaviour Correlation for Nico-GO and Nico-Mwcnts Composite Coatings

NiCo coatings are widely used in sensors, actuators and as protective coatings. Recent studies have shown that addition of foreign particles like Al2O3, SiC and TiO2 promotes grain randomization and refinement resulting in improved corrosion resistance performance. In the present work, NiCo coating containing varying amount of graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) were electrodeposited over mild steel substrate. Microstructure and corrosion behavior of these composite coatings were then studied as a function of the volume fraction of the secondary additives. NiCo-GO & NiCo-CNT composite coating were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) for phase identification, morphology and composition respectively. Potentiodynamic polarization studies and electrochemical impedance spectroscopy (EIS) studies in 3.5 wt. % NaCl solution revealed that the corrosion behavior of the coatings was very sensitive to the concentration of GO/ MWCNTs in the coating matrix. With continuous increase in the amount of GO/CNT in the coatings, the corrosion resistance first increased followed by a decrease, indicating possibility of an optimum with respect to the amount of the additives for achieving high corrosion resistance performance. On analyzing the electrolytic bath solution, we observed that nickel ions (Ni+2) showed preferential deposition onto the graphene oxide sheets resulting in a compositional heterogeneity near and far from the graphene-metal interface in the electrodeposited coating microstructure. This compositional segregation led to a change in the relative abundance of low angle and high angle boundaries in the coating microstructure. Electron backscattered diffraction (EBSD) technique was used to study the type of grain boundaries, strain in the grain and average grain size (area) of the samples (prepared using focused ion beam FIB). The data revealed that the samples exhibiting maximum corrosion resistance (optimum CNT/ GO concentrations) also had the highest fraction of low angle grain boundaries (LAGBs) with no additional strain in the matrix. Further increase in GO concentration resulted in more grains with high misorientation angle. In case of CNTs addition, the coatings were found to be hydrophobic in nature with a grain growth along low energy (111) direction. Figure 1

Effect of Ligand-Complex Interactions on the Electrodeposition of Mixed Chromium Metal-Carbide-Oxides from Trivalent Chromium Electrolytes

Electrolytic chromium coated steel (ECCS) is packaging steel coated with a thin layer of chromium with an outer layer of chromium oxide. This coating system provides corrosion protection in addition to good adhesion properties due the outer oxide layer. The coating for ECCS is deposited via a hexavalent chromium electrolyte which has been found to be an environmental and health hazard and is therefore subject to restrictions under REACH legislation. A new coating process based on trivalent chromium chemistry has therefore been developed.According to prior studies, coatings comparable in terms of corrosion resistance to those achieved with the traditional Cr(VI)-based process have been produced with this process [1]–[4]. However, at present there is limited understanding of the mechanism and kinetics of electrodeposition from trivalent chromium based electrolytes. This knowledge is key to optimize the process design for industrial plating lines. In the present study, we investigate the effect of the chemistry of the Cr(III) complex – as determined by the relative concentration of the formate complexing agent and temperature – on the electrodeposition of mixed chromium metal-carbide-oxide coatings on low carbon steel in a rotating cylinder electrode (RCE) setup.In this study, low carbon steel samples are electroplated in an aqueous Cr(III) based electrolyte bath with a deposition time of 0.8 s with applied current densities ranging from 20 to 90 A dm-2. The pH of the electrolyte is maintained at 2.6. A rotation speed of 776 RPM is used. SEM and XPS analysis is also performed to determine the effect of the above parameters on the microstructure and composition of the deposits. The amount of Cr deposited is determined using XRF measurements. Relative chromium metal, oxide and carbide contents are determined via XPS analysis. UV-Vis spectra of each of the electrolytes are also measured.Optical surface analysis shows that of the three regimes distinguishable as a function of current density [2], homogeneous, bright coatings are deposited in regime II (Figure 1). The current range over which acceptable coatings are deposited is significantly wider with higher relative ligand concentrations. Lower applied currents are required with lower bath temperatures. Increasing the chromium ion concentration (at a fixed relative ligand concentration) results in increased Cr metal deposition and an associated decrease in the carbide content of the coating. At higher bath temperatures, carbide formation is favoured. Results also indicate a threshold ligand-to-complex ratio at ~2.0 [HCOO-]/[Cr3+] above which a bright, homogeneous coating is deposited. This threshold corresponds with UV/Vis results which indicate the formation of a new complex species in the electrolyte at that ratio (Figure 2). Figure 1

Bulk and Surface Chemistry of Photoactive Electrodeposited Cu2O Films Using X-Ray Absorption Spectroscopy

Cu2O is an attractive photocathode for important renewable energy reactions such as water splitting and CO2 reduction. A variety of synthesis methods for Cu2O films have been reported such as physical vapour deposition techniques1,2, chemical vapour deposition3,4, hydrothermal methods5 and electrodeposition6–8. Electrodeposition is a particularly popular method due its low cost and versatility, which appears to get consistent and even film deposition on conductive substrates. However, very little is known on the effects of the synthesis conditions on structure and properties. Majority of works in the literature often show vastly different photoelectrochemical activity, morphology and conductivity type with seemingly slight variation in the synthesis conditions. These variations can be in the electrolyte bath composition, deposition temperature, time, solution pH and electrochemical conditions.While commonly used characterisation methods like XRD, SEM, XPS and Raman spectroscopy are necessary to provide basic information of Cu2O formation, they are insufficient in providing a further understanding of the composition in terms of the Cu species present in each film. In this work, we take a systematic look into the bulk and surface chemistry of electrochemically deposited Cu2O using high resolution XANES and EXAFS spectroscopy. By using HERFD-XAS, we were able to see that changing the deposition parameters altered the Cu(II) amounts. A series of quantitative analyses revealed that none of films were purely composed of Cu(I) species, with amounts of Cu(II) varying from 0.7% to 9.35% across samples.Photoelectrochemical measurements appear to show a correlation in the amount of Cu(II) and the activity of the photocathodes. Highest photocurrent generation was observed in the film with the highest Cu(II) content, however, this was at the expense of stability due to reductive decomposition to Cu metal. We propose that the Cu(II) species initially reduce to Cu metal, forming Schottky barriers at the newly formed metal semiconductor contacts, hence the increase in photocurrent. Nevertheless, this is limited by other factors including film thickness and crystallite grain size. The most stable film was consistent with the quantitative analyses from XAS, which indicated that this film had the lowest amount of Cu(II) in its structure.We concluded that there must be a compromise between activity and stability when optimising deposition parameters for electrodeposition of Cu2O as a photocathode. This work shows the importance of advanced characterisation techniques for gaining a more thorough understanding of structure and composition, and how this may correlate to the performance or functionality of a material. It serves as a guide for future development of more active Cu2O based films for photoelectrochemical processes as well as for solar cell applications.Manuscript in preparation.References1 D. S. Darvish and H. A. Atwater, J. Cryst. Growth, 2011, 319, 39–43.2 S. Dolai, S. Das, S. Hussain, R. Bhar and A. K. Pal, Vacuum, 2017, 141, 296–306.3 M. Ottosson and J.-O. Carlsson, Surf. Coatings Technol., 1996, 78, 263–273.4 C. R. Crick and I. P. Parkin, J. Mater. Chem., 2011, 21, 14712–14716.5 A. D. Handoko, C. W. Ong, Y. Huang, Z. G. Lee, L. Lin, G. B. Panetti and B. S. Yeo, J. Phys. Chem. C, 2016, 120, 20058–20067.6 A. E. Rakhshani and J. Varghese, Sol. Energy Mater., 1987, 15, 237–248.7 A. E. Rakhshani and J. Varghese, J. Mater. Sci., 1988, 23, 3847–3853.8 W. Siripala, L. D. R. . Perera, K. T. L. De Silva, J. K. D. S. Jayanetti and I. M. Dharmadasa, Sol. Energy Mater. Sol. Cells, 1996, 44, 251–260.

Оптимизация технологии вытапливания жира страуса в присутствии электроактивированной жидкости

Introduction. The fundamental competitiveness of all food industries is based on two key points. The first one is the effective use of traditional and new raw materials. The second one is a constant upgrade of the technical base by introducing innovative technological solutions and modern equipment. In this aspect, the fat processing industry is no exception. The development of a comprehensive and sustainable processing of ostrich fat can help to obtain rendered fat with specufic properties that can be used in functional foods and cosmetics. The research objective was to improve the parameters of ostrich fat rendering by using electrolyzed fluid in order to obtain a functional fat product of high quality indicators.&#x0D; Study objects and methods. The research featured ostrich fat obtained by wet melting in the aqueous phase of electrolyte (catholyte). A saline solution of sodium chloride (4 g/100cm3) was subjected to electrochemical treatment in an electrolytic bath with a direct current of 0.5–0.6 A and a voltage of 40–42 V. For fat extraction, we used catholyte with the following parameters: pH 9–11, redox potential between –600 and –700 mV. A two-factor experiment helped to improve the technological parameters of fat rendering. Catholyte hydrogen index X1 (Z1) and fat melting temperature X2 (Z2) were chosen as the primary technological parameters.&#x0D; Results and discussion. The processing temperature of raw fat had a significant effect on the fat yield. When the catholyte hydrogen index and the temperature were increased, it had a negative effect on fat extraction. The acid value of ostrich fat was significantly affected by the pH of catholyte. The inactivating effect of catholytic action on the enzymatic processes resulted in low values of peroxide fat.&#x0D; Conclusion. The research provided the following optimal range for producing ostrich fat with improved consumer properties: hydrogen index = 10.5–11.0, melting temperature = 60.0–100.00°C.

Distortion-Free Sensing of Neural Activity Using Graphene Transistors.

Graphene solution-gated field-effect transistors (g-SGFETs) are promising sensing devices to transduce electrochemical potential signals in an electrolyte bath. However, distortion mechanisms in g-SGFET, which can affect signals of large amplitude or high frequency, have not been evaluated. Here, a detailed characterization and modeling of the harmonic distortion and non-ideal frequency response in g-SGFETs is presented. This accurate description of the input-output relation of the g-SGFETs allows to define the voltage- and frequency-dependent transfer functions, which can be used to correct distortions in the transduced signals. The effect of signal distortion and its subsequent calibration are shown for different types of electrophysiological signals, spanning from large amplitude and low frequency cortical spreading depression events to low amplitude and high frequency action potentials. The thorough description of the distortion mechanisms presented in this article demonstrates that g-SGFETs can be used as distortion-free signal transducers not only for neural sensing, but also for a broader range of applications in which g-SGFET sensors are used.

Ni–Co alloy electrodeposition from the cathode powder of Ni-MH spent batteries leached with a deep eutectic solvent (reline)

Choline chloride based-deep eutectic solvents (DES), namely: choline chloride (ChCl): urea (U), reline, ChCl: glycerol (G), and ChCl: ethylene glycol (EG), ethaline, were used as leaching media for the cathode powder of spent Ni-MH batteries. It is shown that the best metal extraction was obtained with the reline DES. The resulting solution was used as electrolytic bath for the electrochemical deposition of a Ni–Co alloy onto a glassy carbon electrode (GCE). A theoretical model that involves the simultaneous presence of two contributions, to the total current density, namely: three-dimensional nucleation and diffusion-controlled growth of the bimetallic phases, and the residual water reduction on the growing surfaces of the bimetallic (Ni–Co) nuclei, was implemented for the analysis of the potentiostatic current density transients. From this analysis, the potential dependence of kinetic parameters was obtained. SEM images of the GCE, after the potentiostatic electrodeposition, showed the formation of nuclei distributed all over the substrate surface. From EDX and XRD analysis it is shown that these nuclei were composed by Ni, Co and oxygen.

Enhancement in the corrosion resistance behaviour of amorphous Ni[sbnd]P coatings by incorporation of graphene

In the current study, amorphous nickelphosphorusgraphene (NiPG) composite coatings were electroplated on mild steel substrate. Coatings were electroplated from nickel sulphate bath containing phosphorus acid and exfoliated graphene in amounts of 50 mg/l, 100 mg/l, 150 mg/l, and 200 mg/l. Phase constitution, composition, surface morphology and corrosion parameters were investigated as a function of the graphene content. Experimental results exhibited that NiP and NiPG composite coatings possessed improved corrosion resistance than the mild steel substrate and addition of graphene enhanced the corrosion resistance performance when compared to the pristine coating. It was observed that an optimum exists with respect to the amount of graphene dispersed in the electrolyte bath for achieving high anti-corrosion property from the coating produced using the respective plating bath. Lower amount of graphene in dispersion produced uniform surface morphology which acted along with the graphene impermeability to yield high corrosion resistance performance. Higher quantity of graphene in dispersion, on the other hand, caused their agglomeration thus producing rough and defective surface morphology which along with non-uniform distribution of graphene yielded higher corrosion rates.

Process parameters affecting the efficiency of indium electrowinning results from sulfate baths

Since indiumisconsidereda strategic material, a study for developing and optimizing a recovery process by electrowinning has been performed. The possibility of using electrolytic baths based on sulfates instead of chlorides has also been evaluated. Nowadays, chlorides are widely used because they generally present greater current efficiencies;however, the dangers of chlorine gasrequireexpensive-sealed systems to avoid human health and environmental issues. The use of sulfatesdoes not present the same problems;therefore the electrowinning process optimization can represent a definite indium recovery improvement. For this purpose, the effects of electrolyte composition, temperature, current density and pH on the quality of the deposit, specific energy consumption (SEC) and current efficiency (CE) have been assessed. The sulfate electrolytic solutionhas been then appropriately modified with organic additives, mineral salts and complexing agents to optimize the indium recovery by electrowinning. ACE of about80% and SEC equal to 2.7 kWh/kg have been obtained, operating with a pH in the range 2.2–2.3 at 40 °C and using 25 A/m2 current density with an electrolytic solution containing 60 g/l of In3+, 30 g/l of Na2SO4, 20 g/l of Al2(SO4)3 and 20 g/l of H3BO3.

Electrochemical synthesis of ZnO-WO3 nanocomposites and their photocatalytic activity

Heterometal oxide nanoparticles of ZnO-WO3 (ZWO) were synthesized using a facile dual step hybrid electrochemical–thermal technique. The role of surfactant additives during synthesis was investigated by introducing three different surfactants:Cetyltrimethyl ammonium bromide (Cetrimide), sodium dodecyl sulphate (SDS), and polyethylene glycol (PEG) into the electrolytic bath. X-ray diffraction and surface morphology studies indicate that the nanoparticles are cubic with an average crystallite size of 30–40 nm. Photocatalytic behaviour of these nanomaterials was tested using Methylene Blue (MB) and Eriochrome Black-T (EBT) as sample pollutants. The best results were observed for the photocatalyst generated in the presence of SDS as an additive and calcined at 650 οC. High degree of decolourisation of both dyes resulting in complete mineralisation is due to the photocatalytic activity of ZWO which is greater than that of commercially obtained TiO2-P25 photocatalysts. This proves that the electrochemical synthetic route with its low cost and high efficiency is an excellent technique for the bulk synthesis of heterometal oxide photocatalysts which could effectively be used in effluent water treatment.

Supporting PtRh alloy nanoparticle catalysts by electrodeposition on carbon paper for the ethanol electrooxidation in acidic medium

Pt80Rh20 and Pt60Rh40 alloy catalysts were electrodeposited at constant current density from different electrolytic baths on commercial carbon paper in order to be tested for the ethanol oxidation reaction (EOR) and as anodes in a direct ethanol fuel cell (DEFC). Pt and Rh anodes prepared in the same form were also examined for comparison. As measured by energy-dispersive X-ray microanalyses, the electrodeposited Pt:Rh atomic ratios were the same as those of the precursors in the bath. X-ray diffraction showed the PtRh alloy formation with mean particle sizes of 8.3 and 7.0 nm for Pt80Rh20 and Pt60Rh40, respectively, and a Pt lattice contraction caused by the Rh addition. The X-ray photoelectron spectroscopy analyses suggested a Pt lattice strain due to Rh alloying because the Pt4f binding energies were shifted to higher values with respect to that of pure Pt. The onset potentials of the alloy oxidation, CO stripping and ethanol oxidation in the cyclic and linear sweep voltammograms indicated that Pt60Rh40 was the most active for the CO and the ethanol electrooxidation. The apparent activation energies for the EOR on that alloy were also the lowest one, in agreement with its highest activity. These results were explained by the bifunctional mechanism, assuming that Rh contributed with hydroxylated species to favor the removal of the CO-type adsorbed species on Pt sites, and by the effect of Rh on the Pt electronic structure, the lattice strain being dominating over the charge transfer between Rh and Pt. Tests carried out in single DEFCs showed the feasibility of using the Pt60Rh40 electrodeposited electrodes on carbon as the anode in a real fuel cell environment.

Role of Additives in Electrochemical Deposition of Ternary Metal Oxide Microspheres for Supercapacitor Applications.

A simple two-step approach has been employed to synthesize a cobalt–nickel–copper ternary metal oxide, involving electrochemical precipitation/deposition followed by calcination. The ternary metal hydroxide gets precipitated/deposited from a nitrate bath at the cathode in the catholyte chamber of a two-compartment diaphragm cell at room temperature having a pH ≈ 3. The microstructure of the ternary hydroxides was modified in situ by two different surfactants such as cetyltrimethylammonium bromide and dodecyltrimethylammonium bromide in the bath aiming for enhanced storage performance in the electrochemical devices. The effect of the surfactant produces a transition from microspheres to nanosheets, and the effect of micelle concentration produces nanospheres at a higher ion concentration. The ternary hydroxides were calcined at 300 °C to obtain the desired ternary mixed oxide materials as the electrode for hybrid supercapacitors. X-ray diffraction analysis confirmed the formation of the ternary metal oxide product. The scanning electron microscopy images associated with energy-dispersive analysis suggest the formation of a nanostructured porous composite. Ternary metal oxide in the absence and presence of a surfactant served as the cathode and activated carbon served as the anode for supercapacitor application. DTAB-added metal oxide showed 95.1% capacitance retention after 1000 cycles, achieving 188 F/g at a current density of 0.1 A/g, and thereafter stable until 5000 cycles, inferring that more transition metals in the oxide along with suitable surfactants at an appropriate micellar concentration may be better for redox reactions and achieving higher electrical conductivity and smaller charge transfer resistance. The role of various metal cations and surfactants as additives in the electrolytic bath has been discussed.

Obtaining Mn-Co Alloys in AISI 430 Steel from Lithium-Ion Battery Recycling: Application in SOFC Interconnectors

The recycling of exhausted lithium-ion batteries from mobile phones originate five solutions with different Co and Mn proportions that were used as electrolytic solutions to obtain Mn-Co spinel coatings on the surface of AISI430 stainless steel. The coatings are intended to contain chromium volatility in the working conditions of Solid Oxide Fuel Cells (SOFC) metallic interconnectors. Potentiostatic electrodeposition was the technique used to obtain Mn-Co coatings from low concentration electrolytes at pH = 3.0 and potential applied −1.3 V. Charge efficiency data were used for sample optimization. Three optimized samples were subjected to oxidation heat treatment at 800 °C for 300 h and then characterized by XRD, SEM and EDS. The results showed that the addition of manganese ions instead of cobalt ions in the electrolytic bath produces more stable and well-distributed deposits as the ratio of the two ions becomes equal in the electrolytic bath. Thin, homogeneous and stable spinel coatings (Mn, Co)3O4 2.8 μm and 3.9 μm thick were able to block chromium volatility when exposed to SOFC operating temperature.

Grain boundary engineering in Ni-carbon nanotube composite coatings and its effect on the corrosion behaviour of the coatings

Coatings have been traditionally used for protection against corrosion. One possible way to enhance the corrosion resistance performance of coatings is by grain boundary engineering (GBE). This study illustrates the role of optimum amount of carbon nanotubes (CNTs) in modifying the grain boundary constitution in nickel-CNT composite coatings thereby enhancing its corrosion resistance performance. Compact and crack free Ni-CNT composite coatings were electrodeposited on mild steel substrates using electrolyte bath with different concentrations of dispersed CNTs (4, 6, 8, 10, 20, 30, 40, 50, 70 and 100 mg/L). Corrosion performance of coatings exposed to 3.5 wt.% NaCl medium was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy techniques. Among the 10 different Ni-CNT composite coatings, relatively low corrosion rates were observed for two distinct CNTs concentrations. Microstructural characterization conducted using the electron back scatter diffraction method (EBSD) suggested that the grains in all coatings grew with 〈110〉 orientation. Ni-CNT3 coating (from 8 mg/l of CNT in electrolyte) which showed low corrosion rate (corrosion current density of 0.98 µA/cm2) primarily contained very high fraction of low angle grain boundaries. Ni-CNT8 coating (from 50 mg/l of CNT in electrolyte) which exhibited the lowest corrosion rate (corrosion current density of 0.66 µA/cm2) contained high fraction of Σ3 coherent twins. Ni-CNT10 coating (from 100 mg/l of CNT in electrolyte) which exhibited the highest corrosion rate (corrosion current density of 14.08 µA/cm2) contained random high energy high angle grain boundaries (HAGBs) along with high energy symmetrical and asymmetrical tilt boundaries.

Fabrication of Long-Range Ordered Aluminum Oxide and Fe/Au Multilayered Nanowires for 3-D Magnetic Memory

Large-scale long-range ordered anodic aluminum oxide and multilayered nanowires (NWs) are attractive to 3-D nanostructured material applications, such as high-density 3-D magnetic memory. This article demonstrates long-range ordered aluminum oxide made by simple and inexpensive double imprinting with line-patterned stamp and uniform iron-gold multilayered NWs fabricated by galvanostatic electrochemical deposition with a single electrolyte bath. These two structural features show potential for future high-density recording systems that require long-range ordered devices separated from each other by insulation to eliminate crosstalk.

Effects of Interfacial Layers on Magnetization Dynamics of [Fe75Co20Cu5/Cu(x)]30 Multilayer Nanowires

A series of highly ordered multilayer [FeCoCu/Cu( x )]30 ( $0 \le x \le 40$ nm with FeCoCu layer thickness fixed 1000 ± 100 nm) nanowire arrays in alumina membrane (200 nm diameter) was fabricated by electrodeposition from a single electrolytic bath. The body-centered cubic (bcc) phase of FeCoCu-alloy separated by a well-defined face-centered cubic (fcc) phase of Cu spacer is confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. The objective of the present investigation is to tune the magnetic properties through inter- and intra-wire interactions between the FeCoCu layers separated by non-magnetic Cu( x ) layers in the multilayer nanowire array. Ferromagnetic resonance (FMR) study was performed in a flip-chip geometry to explore the magnetization dynamics. FMR measurements confirm the decrease of resonance field ( $H_{r}$ ), whereas resonance linewidth ( $\Delta H$ ) and FMR absorption increase with the increase in the Cu layer thickness. It may be argued that through inter-/intra-nanowires interactions, the Landau–Lifshitz–Gilbert damping provides the most physically sensible magnetization relaxation in multi-layered nanowires system. The values of the Gilbert damping parameters (intrinsic and extrinsic), obtained from the FMR linewidth analysis, exhibit a decrease from FeCoCu nanowire to [FeCoCu/Cu(5 nm)] nanowire. With further increase in the Cu thickness, both these parameters were observed to have increased.

New insight into the electrodeposition of NiCo layered double hydroxide and its capacitive evaluation

Although the peculiarities of electrodeposition in the preparation of metal hydroxides is quite attractive, adequate interpretation of this process still lacks. Here, a novel interpretation of the electrodeposition of nickel cobalt double layered hydroxides (NiCo-LDHs) is proposed. Different from the traditional strategies implemented in the pure nitrate or nitrate-assisted electrolytic baths, the sulfate solution with thiourea (TU) additive is used. Benefited from the chelating and inducing effects of TU, honeycomb-shaped NiCo-LDH nanosheets can be successfully electrodeposited on nickel foam (NF). When performed as free-standing electrodes, these integrated electrodes show a robust capacitive performance. Specifically, NC2S12-15/NF (deposition for 15 min) electrode can deliver remarkable electrochemical properties, such as large capacity (1198 F g−1 at 1 A g−1), excellent rate performance (1000 F g−1 at 100 A g−1) and good cycling stability. Additionally, the NC2S12-15/NF//activated carbon (AC) hybrid capacitor (HC) can sustain extraordinary cycle life (88.3% retention for 10,000 cycles) and high energy density (29.1 Wh kg−1), further demonstrating the qualified capacitive behavior of NC2S12-15/NF electrode. This work provides a new insight into the electrodeposition of metal LDHs based on the design of the electrolyte solution.

Formation of Coatings on Details from Valve Metals Alloys by Micro-Arc Oxidation in Internal Cavities of Counter Electrodes

It is shown that micro-arc oxidation (MAO), implemented according to traditional schemes in electrolytic baths with mechanical and pneumatic mixers, does not provide the formation of uniform ceramic coatings on the surfaces of holes, grooves and slots in the details from the alloys of the metals of valve group, and is characterized by a significant cost and relatively low safety. Fundamental possibility of MAO realization in the inner cavities of the special counter electrodes by passing solutions of electrolytes through them is installed. The calculated and experimental researches of MAO, applied to the processing of ball details from aluminum and titanium alloys, are conducted. The most rational design parameters of counter electrodes, as well as the rational parameters of the flow of electrolyte solutions in the clearances between the surfaces of details and counter electrodes are revealed. Innovative schemes for MAO of spherical details are developed. By measuring the thickness and hardness of the formed coatings it is proved that MAO, in the internal cavities of the counter electrodes, provides for the formation of more uniform ceramic coatings on the details from alloys of valve metals, in comparison with the traditional MAO in electrolytic baths with pneumatic and mechanical mixers.