Bath Chemistry Research Articles

Cobalt Oxide Nanorod Anode for Lithium Ion Battery

Nanomaterials with one-dimensional (1-D) structure have been extensively studied as electrode materials for such functional electrochemical devices as sensors, supercapacitors, and rechargeable batteries. In particular, the nanorod electrode is considered as one of the most promising options for thin film lithium batteries because of its enhanced structural stability during lithiation/delithiation cycling and rate capability.Template–assisted methods using anodic aluminum oxide or polycarbonate have been usually used for the synthesis of nanorod electrodes. However, the use of template typically makes the preparation procedure complex and resulted often in unintended aggregation of nanorods after the template removal.This work focuses on the preparation of the cobalt-based nanorod arrays for the anode in lithium ion batteries by a template-free electrochemical synthesis of cobalt nanorod and its subsequent oxidation. Cobalt electro-deposit showed different growth habit depending on the deposition parameters of temperature, current density and bath chemistry, and well-defined 1-D nanorod structure was successfully fabricated under their careful control. The following thermal oxidation of the cobalt nanorod led to cobalt/cobalt oxide bilayer composites with little change in its macroscopic structure.In this presentation, the morphology and structure of the as-prepared pure cobalt nanorod and its oxidized product (i.e., cobalt / cobalt oxide nanorod composite) will be presented. Moreover, the electrochemical properties of nanorod composites will be discussed on the basis of the cyclic voltammograms, galvanostatic charge-discharge curves, and electrochemical impedance spectra. The rate performance and long-term cycling stability of the nanorod composites will be particularly highlighted.

Electrophoretic Deposition of Cobalt Ferrite and Platinum Cobalt Nanoparticles as Electrocatalysts

Cobalt ferrite and platinum cobalt nanoparticles were deposited using electrophoretic deposition (EPD) from two different bath chemistries. The first bath contained 2 g/L particles suspended in 90 vol.% water and 10 vol.% isopropanol with 0.4 g/L hexadecyltrimethlyammonium bromide. The second bath contained 2 g/L particles suspended in 100 % ethanol. The deposits were tested for electrocatalytic properties for the oxidation of ammonium sulfite to ammonium sulfate. Linear sweep voltammetry showed that both EPD deposits of cobalt ferrite and platinum cobalt nanoparticles had electrocatalytic activity.

Study of role of phosphate coating properties on electrophoretic paint performance by EIS and simulated corrosion tests

The influence of phosphate bath chemistry on phosphate coating properties and, eventually, on corrosion resistance properties of electrophoretic (ED) painted steel samples was examined. Two types of zinc phosphate bath chemistry with different concentration of zinc and nickel ions, and different values of total acid, free acid, and accelerator content were studied. The phosphate bath with higher value of acid ratio (total acid/free acid), nickel ion concentration, and accelerator point produced the best phosphate coating on steel surface with globular microstructure, small crystal size, high P ratio, and uniform coverage. Phosphate coated and only alkali cleaned samples were cathodic ED painted. Their corrosion resistance properties were evaluated by salt spray test, cyclic corrosion test and electrochemical impedance spectroscopy. The relative increase in corrosion resistance of painted sample due to best phosphate coating was 1·4 to 1·8×. Paint adhesion of samples significantly deteriorated when painted without phosphate pretreatment.

Influence of coating bath chemistry on biomimetic calcium phosphate coatings

Magnesium alloys are an emerging class of biodegradable medical implant materials. However, control of their degradation rate and biocompatibility are key issues that need to be addressed prior to their use in clinical applications. In this article, a two-step method to biomimetically deposit corrosion-resistant calcium phosphate coatings on magnesium alloy AZ31 is described. A decrease in the overall dissolution of the magnesium substrate of up to 99·8% was observed for the coated samples in comparison with non-treated magnesium AZ31. Surface characterization of the coatings was performed by attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the composition, morphology and corrosion resistance of the biomimetic calcium phosphate coatings depend strongly on the coating bath composition.

Investigation of Freeze Lining in Copper-Containing Slag Systems: Part III. High-Temperature Experimental Investigation of the Effect of Bath Agitation

Freeze-lining technologies have been employed to protect the cooling walls of reactors from chemically aggressive molten reactants. To date, the designs of freeze linings for pyrometallurgical reactors have been based on the basic assumption that the interface between the deposit and the bath remains at the liquidus temperature of the bulk liquid. There is, however, increasing evidence that interface temperature between stagnant deposit and bath is less than the liquidus of the bulk liquid. A previous study also demonstrated that the effects of bath chemistry need to be taken into account in freeze-lining designs. To investigate the fundamental processes involved in the formation and stability of the deposit, experimental laboratory studies have been undertaken in the Cu-Fe-Si-Al-O slag system in equilibrium with metallic copper using an air-cooled probe technique. In the current study, the effects of bath agitation on the microstructure, morphologies of the phases, and formation of various layers across the freeze-lining deposit were studied at steady-state conditions. It appears that the changes in the fluid flow pattern through changes in shear intensities result in corresponding changes in the deposit microstructure, formation of the sealing primary phase layer, thus influencing the interface temperature between freeze-lining deposit and the liquid bath.

Codeposition mechanism in Sn/Ag nanoparticle composite plating

Mechanism of the Ag nanoparticle codeposition in Sn/Ag–nanoparticle composite plating was studied using a rotating disk electrode. The bath chemistry of the Ag–nanoparticle/Sn2+–pyrophosphate colloidal solutions and the kinetics of the Sn matrix deposition were also discussed. The dialysis experiments of the plating baths showed that the composition of the Ag nanoparticles were stoichiometric, AgSn0.54+(NP), and that their structure was Ag core/Sn4+–pyrophosphate complex shell type. The current density–potential relationships of the Sn matrix deposition showed a two-step features. The first current plateau at around −1.4V vs. Ag/AgCl was related to the diffusion limited current of SnP2O72−. The Ag codeposition rate was controlled by Tafel kinetics and reached the diffusion limited values, showing that the codeposition rate of the AgSn0.54+(NP) is controlled by electrochemical reactions. The electrochemical kinetic parameters and the diffusion coefficient of the AgSn0.54+(NP) were estimated by fitting the experimental data to the Tafel equation taking into account the concentration of the electroactive species at the cathode. The diameter of the AgSn0.54+(NP) was calculated to be 4.2nm by substituting the diffusion coefficient estimated here into the Einstein–Stokes equation. The diameter was agreed with the results from the transmission electron microscope examination and the small angle X-ray scattering analysis.

Application of Thermodynamic Models for Better Understanding and Optimizing the Hall–Heroult Process

During the last decade, important improvements have been made in the application of thermodynamic models for studying the molten cryolite system used in the Hall–Heroult process. This approach allows a better understanding and paves the way for furthering developments in bath chemistry and molten metal processing. In this article, thermodynamic modeling is used to explore the operating windows in the reduction of alumina in molten cryolite. The impact of a range of concentrations of AlF3, CaF2, and Al2O3 in conventional or “lithium-free” baths is also discussed. Subsequently, the model was also used to evaluate the impact of additions of lithium fluoride to the bath. Conditions allowing an operation at lower cell voltages and lower bath temperatures were identified. The modeling approach described in this article is considered as an important innovation to revisit fundamentals, to constantly re-examine paradigms, and to identify potential modifications in bath chemistry for improving energy efficiency and productivity of modern prebaked Hall–Heroult cells.

Branched titania nanotubes through anodization voltage control

Titania nanotubes are attractive for many applications such as energy generation, storage and delivery, gas sensing, and water purification. Here, we demonstrate branched titania nanotube formation during potentiostatic anodization of titanium films or foils in a single electrochemical bath by stepping down the anodization voltage V anod below a threshold value. The linear dependence on the titanium nanotube diameter with V anod and the lack of nanotube formation for V anod < 20 V constrains homogeneous branching to occur only V 2 ≤ V 1 2 − V 0 , where V 1 and V 2 are the initial and final anodization voltages and V 0 is a voltage offset dependent on the anodization bath chemistry. Our technique circumvents the constraints of multi-bath and multi-temperature methods for branching, and provides a versatile means for creating hierarchically sized and/or interconnected titania nanotubes for applications.

Strain in electroless copper films monitored by X-ray diffraction during and after deposition and its dependence on bath chemistry

X-ray diffraction based strain measurements have been carried out during the deposition and subsequent relaxation of electroless (autocatalytic) polycrystalline copper films. Thin polymer substrates were mounted on the surface of an electrolyte-filled plating cell, and the X-rays traversed the substrate to scatter of the growing Cu layer. The plating cell was rotated back and forth by up to 70° in order to find the strain of Cu crystallites within and perpendicular to the plane of the film ( sin 2 ψ method). Three types of plating solutions were investigated. A Ni-free solution C leads to compressive strain during steady-state film growth, followed by an exponential relaxation of the film to a residual tensile strain. Electrolytes A and B contain Ni ions, and the resulting Cu(Ni) films have nearly constant strain with small counteracting strain variations during and after film growth. Cyanide-stabilized solution A yields films with a slight compressive strain, while solution B, stabilized by an aromatic nitrogen compound, yields films with tensile strain. Different and reproducible evolution patterns observed for these three electrolyte types establishes in situ X-ray diffraction strain monitoring as a method to evaluate chemical formulations for electroless deposition.

Improving the CoNiMnP Electrodeposition Process Using Taguchi Design of Experiments

Thin film magnetic materials with out-of-plane anisotropy are important for microelectromechanical systems (MEMS) actuation and other applications requiring forces at a distance. Electrodeposited magnetic alloys are the most easily integrated option because they do not require high temperature processing or exotic seed layers. However, electrodeposition processes can be inconsistent and optimizing such processes is difficult because of the large number of factors typically involved: seed layer, bath chemistry, physical bath parameters, and current density. Such problems are well-suited to Taguchi design of experiments, which we used to determine and optimize factors with the largest influence on residual stress and out-of-plane magnetic properties of CoNiMnP films. A new process recipe resulted which yielded a maximum energy density of , a remanence of , and a coercivity of . These results provide improved properties for immediate application in magnetic MEMS and should guide future work in the optimization of CoNiMnP and other electroplated cobalt alloys.

Improvement of the corrosion behavior of electrodeposited CoFeCu thin films

The limited range of Cu that must be added to achieve reasonable magnetic and corrosion properties during the deposition of CoFeCu alloy-based thin films is a stringent control issue in manufacturing. The use of limited amount of phosphorus added in the bath to confer better corrosion properties on the thin film is considered in this work. Potentiodynamic polarization technique in 2.5 wt.% NaCl solution was used to study the corrosion properties of electrochemically deposited CoFeCu thin films that contained varying amounts of phosphorus. The results indicate that the addition of limited amount of phosphorus improves the passivity of the CoFeCu thin film. The range of the amount of phosphorus required to be added in the alloy for best corrosion properties was defined. For the bath chemistry and composition studied, the level of corrosion resistance improvement was found to be limited to a phosphorus-alloy content of between 3.0 and 5.3 at. wt.%. (above this phosphorus-alloy content, a fully amorphous alloy is thought to be deposited).

Testing of Aluminium Carbide Formation in Hall-Heroult Electrolytic Cell

The trend in the aluminium smelting industry today is to operate cells with graphitized carbon cathode linings, increased current density and acidic bath chemistry. The resulting problem is an accelerated wear of graphitized cathode blocks, thought to be caused by formation and subsequent dissolution of Al4C3 at the cathode lining surface. The cycle of formation and subsequent dissolution Al4C3 is recognized as one of the most important mechanism causing pothole and surface wear, which results in limiting of the cell lifetime and loss efficiency. A special laboratory test method was developed to elucidate the mechanism of Al4C3 formation in electrolytic cell. The Al4C3 formation in the region between the carbon surface and aluminium as well as between the carbon surface and electrolytic bath has also been studied using X-ray diffraction, as well as optical and scanning electron microscopy. Solid Al4C3 layer was observed at the carbon surface. A possible mechanism which explains the presence of Al4C3 at the metal-bath interface is the transfer of dissolved carbide in the bath from metal-carbon interface.

Electrodeposition of Alloys of Rhenium with Iron-Group Metals from Aqueous Solutions

Rhenium (Re)–Me alloys (where , Fe, or Co) were deposited galvanostatically. The plating bath consisted of ammonium perrhenate, nickel or cobalt sulfamate, or iron sulfate, citric acid, and magnesium sulfamate. The effects of bath chemistry and deposition time on faradaic efficiency (FE), Re content, and partial deposition currents were determined. Rhenium contents as high as 93 atom % or FE values as high as 96% were attained in different solutions. The results are discussed, with emphasis on routes to increase the FE and Re content in the coating. The possible role of the second metal in the electrodeposition of Re is presented. A plausible mechanism by which addition of Ni, Fe, or Co to the solution enhances the rate of the deposition of Re is through a unique type of electroless deposition, in which the reducing agent is formed in situ.

Establishing relationships between bath chemistry, electrodeposition and microstructure of Co–W alloy coatings produced from a gluconate bath

Electrodeposited Fe group: W and Mo alloys have the potential to replace hard Cr coatings for use in engineering applications where wear and corrosion resistance are needed. Electrochemical studies have concentrated in the past on Ni–W alloy deposition, but now interest in Co–W alloys has developed as they possess lower coefficients of friction when in contact with another metal. The most attractive coating composition is in the range 14–20 at.% W, if controlled deposition promotes crystalline alloys of high hardness, rather than softer amorphous alloys containing >20 at.% W. This paper employs ammonia free baths with low concentrations of cobalt and sodium tungstate and varying additions of sodium gluconate to produce alloys at close to 50% efficiency. Voltammetry, UV and visible spectrometry, and potentiostatic deposition have been performed on such baths, whilst XRD, SEM and TEM observations have been made on the deposits. This aims to optimise the process and to understanding the relationships between bath contents, electrochemical kinetics and alloy composition. Efficient deposition of coatings with hardness values up to 1000 kgf mm −2 occurred from a bath containing a high concentration of gluconate. Such deposits arise from concentrations of Co–W–gluconate complexes which promote the formation of nanoscale alloy grains. Current densities up to 2.75 A dm −2 in the agitated bath promoted deposition kinetics to form these highly orientated structures. These kinetics produced nano-segregation of W which may be assisted by the migration of Co–W clusters to boundary sites during the growth of the deposit.

Improving Copper Electrodeposition in the Microelectronics Industry

Sporadic voiding within the interfacial Cu3Sn intermetallic compound (IMC) layer-sometimes referred to as ?Kirkendall voiding?-has been found to lead to degradation of solder joint reliability in board level, mechanical shock testing. It has been suggested that the voiding phenomenon is a result of the incorporation of organic impurities in the copper (Cu) deposit during electroplating. In the present study, Cu samples were electroplated galvanostatically from a generic solution, containing Cl- ions, as well as a suppressor [polyethylene glycol (PEG)], and a brightener (bis(3-sulfopropyl) disulfide, SPS) as additives. Overpotential transients were measured during electroplating with a range of current densities (0.5-40 mA cm-2) in baths with various compositions. Effects of the bath chemistry on the Cu surface morphology, as well as on the propensity for voiding after soldering, were also investigated. Elemental analysis of selected samples was performed by SIMS. Plating at 10-20 mA·cm-2 with an optimized bath composition led to Cu with a fine-grain structure and smooth appearance. Solder joints formed from these deposits remained void free after soldering and thermal aging. Lower current densities, ran in the same plating bath, led to a significant propensity for voiding, apparently because of incorporation of, principally, SPS and its breakdown products into the growing layer. Continuous plating at 10 mA cm-2 for up to 18 hours without replenishment revealed a strong dependence on bath aging, with Cu changing from ?void-proof? to clearly ?void-prone.? These trends were attributed to the different rates of consumption for PEG and SPS and changes in the contaminants being incorporated in the deposits. In general, differences in the voiding behavior of the plated Cu could be predicted by monitoring a set of characteristic overpotential transient signatures.

Electrodeposition of Alloys of Rhenium with Iron-Group Metals from Aqueous Solutions

Rhenium (Re) is a refractory metal, which exhibits unique combination of properties, making it an attractive material in a variety of applications. The mechanism of Re electrodeposition is still unknown. However, there are clear indications that codeposition of alloys with iron-group metals may lead to higher-quality coatings and higher Faradaic efficiencies (FE's). Re-Me alloys, where Me=Ni, Fe or Co, were deposited galvanostatically. The bath solution consisted of ammonium perrhenate, nickel or cobalt sulfamate or iron sulfate, citric acid, and magnesium sulfamate. The effects of bath chemistry and deposition time on the FE, Re content and partial deposition currents were determined. Rhenium contents as high as 93 at.% and FE values as high as 96% were attained. The results are discussed with emphasis on routes to increase the FE and Re content in the coating. The possible role of the 2nd metal in electrodeposition of Re is presented.

Electrodeposition of Ni–W–B nanocomposite from tartrate electrolyte as alternative to chromium plating

The effect of the bath chemistry and operating conditions on the chemical composition, microstructure and properties of Ni–W–B alloys deposited from tartrate baths on working electrode was studied for the first time by the pulsed current method. The investigations included the measurement of the current efficiencies and determination of the tungsten content in the electrodeposits. UV spectrometry was used for characterisation of complex formation. The grain size of deposits was determined by XRD. Also, the morphology of the deposits was studied by SEM. Amorphous Ni–W–B alloys were successfully obtained by electrodeposition from the tartrate bath. The corrosion behaviour of Ni–W–B coating on mild steel has been evaluated during exposure to 3·5%NaCl solution by electrochemical impedance spectroscopy. The electrochemical and corrosion behaviour of Ni–W–B alloy showed a good corrosion resistance in the 3·5%NaCl medium. The microhardness of nanocrystaline Ni–W–B is in the range between 700 and 850 HV.

69.2: Designing Strong Glass for Mobile Devices

AbstractCompared to plastic, glass is tougher, scratch resistant, offers optical quality and a richer look for consumer electronic applications. The mechanical performance of silicate glasses can be improved via ion‐exchange in molten salts. Variables that affect the ion‐exchange process, such as glass composition, thermal history, time, temperature, and bath chemistry will be discussed.

Critical Parameters of Solution Design for Electrodeposition of 2.4 T CoFe Alloys

The electrodeposition of soft, high magnetic moment alloys has become the critical fabrication step in manufacturing of magnetic recording heads. The need for ultimately high magnetic moment alloys (2.4 T CoFe) and the electrodeposition process capable of delivering magnetic structures with dimension in the range of several tens of nanometers are the new tasks that have to be addressed if the future magnetic recording devices will use the electrodeposited alloys for writing pole application. This complex challenge could be successfully achieved by fully considering the conditions at the electrochemical interface for additive adsorption and incorporation, iron hydroxide formation and incorporation, and by careful design of the bath chemistry and deposition parameters that would yield the high moment alloys with the optimum magnetic properties. In this manuscript, some of the key aspects of successful electrodeposition of 2.4 T CoFe alloys are discussed with experimental results and theoretical foundations indicating future direction for development of electrodeposited high moment alloys and nanostructures.

Impacts of support membrane structure and chemistry on polyamide–polysulfone interfacial composite membranes

Herein, we discuss the properties of polyamide thin films formed via identical interfacial polymerization conditions over porous polysulfone supports with different physical and chemical properties. Polysulfone supports were formed by nonsolvent induced phase separation (i.e., immersion precipitation) employing several casting solution and precipitation bath chemistries. Hand-cast polysulfone films (and a commercial polysulfone membrane) exhibited a wide range of pure water permeabilities, dextran rejections, water contact angles, and surface roughness statistics. These results, combined with FTIR spectra and SEM images, confirm that each support offered a different skin layer pore morphology and chemistry. Polyamide composite membranes formed thereon displayed widely varying film morphology, separation performance, and interfacial properties. More permeable, hydrophilic supports produced low permeability polyamide–polysulfone interfacial composite membranes, whereas highly porous, relatively hydrophobic supports produced more permeable composite membranes. A conceptual model was proposed to explain the potential impacts of polysulfone support membrane properties during the polyamide interfacial polymerization reaction and the resulting characteristics of polyamide–polysulfone interfacial composite membranes.