Effect of a new condensation product on electrodeposition of zinc from a non-cyanide bath

Zinc electrodeposition from sulphate chloride bath was carried out in presence of condensation product formed between chitosan and veratraldehyde. The bath constitutents and operating parameters such as pH, temperature and current density were optimized through Hull cell experiments. Current efficiency and throwing power were measured. Polarization study revealed high shift of potential towards negative direction in the presence of addition agents. Corrosion resistance test revealed good protection of base metal by zinc coating obtained from developed electrolyte. SEM photomicrographs showed fine-grained deposit in the presence of condensation product. The IR spectrum of the deposit showed inclusion of the condensation product during electroplating. The consumption of brightener in the lab scale was 5 mLL⁻¹ for 1000 amp-h.     

Influence of additives on electrodeposition of bright Zn-Ni alloy on mild steel from acid sulphate bath

The influence of a condensation product (CP) of veratraldehyde (VRTD) and p-amino benzoic acid (PABA) on Zn-Ni alloy electrodeposited onto mild steel was studied in acidic sulphate solutions. Ethylenediaminetetraaceticacid (EDTA) and cetyltrimethylammoniumbromide (CTAB) were used as complexing and wetting agents, respectively. The effect of bath constituents, pH, current density and temperature on nature of deposit were studied through Hull cell experiments. The bath constituents and operating parameters were optimized. Deposit properties and corrosion resistance were discussed. Throwing power, current efficiency and polarization studies were carried out. SEM photomicrographs of the deposit obtained from optimum bath revealed fine-grained deposit of the alloy in the presence of condensation product and hence modified the morphology of zinc-nickel alloy deposit. IR spectrum of the scrapped deposit showed inclusion of addition agent.     

A new condensation product for zinc plating from non-cyanide alkaline bath

Zinc electroplating from non-cyanide alkaline solution is carried out in the presence of condensation product formed between DL-alanine (DLA) and glutaraldehyde. The bath constituents and bath variables are optimized through standard Hull cell experiments. The current efficiency and the throwing power are measured. High shift of potential towards more cathodic direction was observed in presence of addition agents. Corrosion resistance test reveals good protection of base metal by zinc coating obtained from the developed electrolyte. SEM photomicrographs show fine-grained deposit in the presence of condensation product. IR spectrum of the scraped deposit shows the inclusion of the condensation product in the deposit during plating. The consumption of brightener in the lab-scale is 6 mLL^-1 for 1000 amp-hour.     

Effect of condensation product on electrodeposition of zinc on mild steel

Electrodeposition of zinc on steel was obtained from acid chloride bath containing condensation products (CP) of 3,4,5-trimethoxy benzaldehyde (TMB) and chitosan (CTN). The effect of bath constituents, pH, current density and temperature on the nature of deposit was studied by Hull cell experiments. The bath composition and operating parameters were optimized. The adhesion, ductility and corrosion resistance of the deposits were discussed. Throwing power and current efficiency values under different plating conditions were measured. SEM photomicrographs of the deposit were taken to study the surface morphology. The inclusion of addition agent in the deposit was investigated from IR spectrum of the scrapped deposit. The consumption of brightener in the lab scale is 10 mLL⁻¹ for 1000 amp-h.     

Polynitroaniline as brightener for zinc-nickel alloy plating from non-cyanide sulphate bath

Electro-polymerization of orthonitroaniline was carried out on graphite electrode in hydrochloric acid medium. Zinc-nickel alloy deposition was carried out in the presence of polynitroaniline in acid sulphate bath. The bath constituent and bath variables were optimized through Hull cell experiments. The current efficiency and throwing power were measured. High shift of potential towards more cathodic direction was observed in presence of addition agent. Corrosion resistance test revealed good protection of base metal by zinc-nickel coating obtained from the developed electrolyte. SEM photomicrograph shows fine-grained deposit in the presence of addition agent. The consumption of brightener in the lab-scale was 0·01 gL⁻¹ for 1000 amp-h.     

Influence of polymer additive molecular weight on surface and microstructural characteristics of electrodeposited copper

Electrodeposition of copper was done with different molecular weight (MW) polyethylene glycol (PEG) as an additive in the plating bath. The adsorbed layer formed of PEG and chloride ion (Cl⁻) in the presence of copper ions has a definite role in controlling the deposition mechanism and the coating characteristics. The adsorption behaviour and suppressor nature of PEG with different MW (200–20000) on the physicochemical and the surface morphological features of the copper deposit were characterized. The results reveal that depending on the adsorption capacity of the intermediate complex, the deposit properties show gradation. There is a range of morphology with particular grain structure for different MW PEG addition. Grain size and the roughness decreased with increase in PEG MW. The concentration of Cl⁻ ion in the plating bath is also significant in determining the deposit mechanism of the bath as revealed from the shift in cathodic potential. The adsorbing power of the complex depends not only on PEG MW but also on Cl⁻ ion concentration. XRD analysis of the copper deposit obtained with low MW PEG showed (220) as the major plane and with high MW PEG the prominent orientation was (111) and (200).     

Modulated morphology of Fe foils electrodeposited at a high current density by adding cations

A modified chloride bath being suitable for high speed electrodeposition was used to deposit smooth and flexible Fe foils. Their surface morphology and crystal structures were observed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results showed that the morphology and crystal structures of Fe foils changed drastically in the presence of Mn²⁺, Sm³⁺, La³⁺ and Fe³⁺ cations. Several morphology shapes were prepared in this paper. This will allow for further studying the effect of surface morphology on catalytic, magnetic and corrosive properties.     

Effect of pressure on the electrodeposition of nanocrystalline Ni-C in supercritical CO2 fluid

Electrodeposition of Ni in a Watt's bath at different applied pressure, and in the presence of CO₂ fluid was investigated. The reduction of carbon and its alloying into the Ni deposit was focused. The current efficiency of electrodeposition and the carbon content in the Ni deposit were found to vary with the applied pressure. The crystal structure of the resulting Ni-C film was characterized by performing X-ray diffraction. The composition of the deposit was analyzed using X-ray photoelectron spectroscopy. Transmission electron microscopy was employed for microstructure analysis. The results showed that nanocrystalline Ni-C deposit could be obtained. The grain size of the Ni-C film varied from 14 to 43 nm, depending on the deposition pressure and carbon content. A significant increase in microhardness from 450 to 720 Hv could be obtained for the Ni film electrodeposited from a bath of 15 MPa supercritical CO₂ fluid. In 1 M HCl solution, a higher open circuit potential and a lower anodic current density were found when the carbon content in the Ni deposit was increased.     

The composition and microstructure of electrodeposited solder on electroless nickel in the presence of gelatine

The effect of gelatine addition to the electrodeposition bath on the tin content of the solder deposits was investigated. The results showed that as little as 0.5 gl^–1 gelatine greatly enhanced the tin content of the deposits. The maximum tin content achievable for the deposit was approximately equal to the percentage of tin in the deposition bath. A lower current density and a greater metal content of the deposition bath tended to offset the effect of gelatine in promoting tin content of the deposit. Gelatine was found, with the aid of scanning electron microscopy and X-ray diffractometry, strongly to affect the morphology and facet orientation of the deposits.     

Substrate-diffusion-controlled film growth: Silver and copper on lead (111)

Silver and copper were vapour deposited onto atomically clean lead (111) surfaces under ultrahigh vacuum conditions. Low energy electron diffraction, reflection high energy electron diffraction and Auger electron spectroscopy measurements in the same chamber showed that, for a 0.1 nm min^-1 impingement of silver or copper, the deposit completely re-evaporated. At 10 nm min^-1 both silver and copper condensed onto a lead (111) surface at room temperature. The silver deposit was a continuous-layer single crystal which had an atomically flat upper surface covered by an equilibrium monolayer of substrate atoms epitaxed to it. The results for the copper experiments were similar to those for silver, except for the presence of small amounts of misoriented copper (111) and polycrystalline copper.It is proposed that substrate diffusion during the condensation of silver or copper onto lead (111) is crucial in determining the mode of film growth. It is thought that two-dimensional nucleation results from a mixed mobile layer of adsorbate and substrate atoms.     

Nickel electrodeposition on copper substrate for cyclotron production of <Superscript>64</Superscript>Cu

Natural nickel electrodeposition on a copper substrate with a gold layer was studied with the aim of production of ⁶⁴Cu radionuclide. The electrodeposition experiments were carried out in acid plating baths. The operating parameters such as pH, temperature, and current density were optimized. The current efficiency was measured at different current densities. The optimum conditions of the nickel electrodeposition are as follows: 5.7 g 1⁻¹ nickel, pH 3–4, dc current density 85.54 mA cm⁻², and 55°C, with 97% current efficiency. SEM photomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath. A 46-μm high-quality layer was deposited on a gold layer of the copper substrate.     

A simple chemical method for preparation of hydroxyapatite coatings on Ti6Al4V substrate

A novel, simple and economical chemical bath method for deposition of calcium hydroxyapatite coating has been developed. The coatings were prepared from EDTA solutions in alkaline media on Ti6Al4V substrates. The method is based on thermal dissociation of the Ca(EDTA)^2- complex at 65–95 °C. Two chemical baths with and without presence of Na⁺ and Cl^- were used for the deposition. The Rutherford back scattering study shows that the coating material from bath which contained sodium and chlorine ions have their presence in the coated material. The bath which has been prepared with potassium substituting sodium and nitrate substituting chlorine produced coatings with better stoichiometry, with Ca/P=1,67. The X-ray analysis revealed that the calcium hydroxyapatite coatings have preferred crystal orientation in the 002 direction. © 2001 Kluwer Academic Publishers     

A novel lanthanum hydroxide nanostructure prepared by cathodic electrodeposition

A novel and interesting nanostructure of La(OH)₃ was prepared by electrochemical method under mild conditions without any hard templates and surfactants. In this method, La(OH)₃ was galvanostatically deposited from low-temperature nitrate bath on the steel substrate by electrogeneration of base. X-ray results showed that the obtained deposit has single crystalline hexagonal phase of La(OH)₃. Morphological characterization revealed that the product has compact morphology with capsule-like structures having approximately an average diameter of 15 nm and the length of up to 50 nm. The results showed that low-temperature cathodic electrodeposition can be recognized as an easy and facile method for the synthesis of La(OH)₃ nanocapsules.     

Morphology,structure, and magnetic properties of electrodeposited Ni films obtained from different pH solutions

Nanocrystalline nickel (Ni) films were obtained by electrodeposition from chloride aqueous solution with different pH values. The influence of electrolyte pH on the morphological, structural, and magnetic properties is studied, using scanning electron microscopy (SEM), X-ray diffraction (XRD), and alternating gradient force magnetometry (AGFM) techniques. SEM studies revealed a granular and compact structure of the surface of the electrodeposited Ni layers, and the variation of film roughness with bath pH is established. XRD analysis gives evidence of strongly textured Ni films along the (111) direction, with the face-centered cubic (fcc) structure for all baths pH. Magnetic properties such as coercivity, remanence, saturation magnetization, and squareness showed strong dependence on the baths pH and crystallite size. High coercivity was attributed to the presence of the small crystallite size of deposits. The properties of the deposit are greatly influenced by the solution pH.     

A High Performance of ENi–P Coatings on Mechanical and Tribological Properties with Influence of Bath pH on AZ91 Magnesium Alloy

Electroless nickel–phosphorus (ENi–P) coating was carried out on AZ91 magnesium alloy substrates by varying the bath solutions pH. The ENi–P coating process was carried out with sodium hydroxide as the pH adjuster. The effect of bath pH values on surface characteristics and wear resistance properties were investigated after deposition on AZ91 magnesium alloy substrates. Three suitable bath compositions with different pH were prepared for coating the substrates. Encouraging results for ENi–P deposit were obtained when the bath pH value was maintained at 6.5. A smooth and uniform microstructure was observed in the deposit obtained from bath B (6.5 pH). It also enhanced the microhardness and wettability, while the surface roughness of the ENi–P deposit reduced considerably, thereby resulting in better wear resistance and also preventing regular or early failures, and improving service life.     

Morphological and electrochemical characterization of electrodeposited Zn–Ag nanoparticle composite coatings

Silver nanoparticles with an average size of 23 nm were chemically synthesized and used to fabricate Zn–Ag composite coatings. The Zn–Ag composite coatings were generated by electrodeposition method using a simple sulfate plating bath dispersed with 0.5, 1 and 1.5 g/l of Ag nanoparticles. Scanning electron microscopy, X-ray diffraction and texture co-efficient calculations revealed that Ag nanoparticles appreciably influenced the morphology, micro-structure and texture of the deposit. It was also noticed that agglomerates of Ag nanoparticles, in the case of high bath load conditions, produced defects and dislocations on the deposit surface. Ag nanoparticles altered the corrosion resistance property of Zn–Ag composite coatings as observed from Tafel polarization, electrochemical impedance analysis and an immersion test. Reduction in corrosion rate with increased charge transfer resistance was observed for Zn–Ag composite coatings when compared to a pure Zn coating. However, the particle concentration in the plating bath and their agglomeration state directly influenced the surface morphology and the subsequent corrosion behavior of the deposits.     

Soft Magnetic Properties and Electrochemical Behavior of Nanocrystalline CoFeCu Thin Films Electrodeposited from Citrate-Added Baths

CoFeCu thin films were electrodeposited from baths with natural pH (instead of pH～2.8 used in conventional baths) and containing different sodium citrate dosages. ChemEQL V.3.0 software was employed to study speciation diagrams of citrate-added CoFeCu bath with natural pH. At low sodium citrate dosage, Co⁺⁺, Fe⁺⁺, and Cu⁺⁺ species were dominant in CoFeCu bath with natural pH (around 5.2). However, as dosage of sodium citrate in the bath increased, the concentration of complexed species (especially Co(C₆H₅O₇)^?, Fe(C₆H₅O₇)^?, and Cu(OHC₆H₅O₇)^2?) significantly raised. Cyclic voltammetry (CV) studies showed that the formation of complexed species in the bath shifted reduction potential of metals towards more negative potentials. Moreover, in order to deposit cobalt and iron simultaneously with copper, it was necessary to increase the reverse potential (E _λ ) value gradually with sodium citrate dosage, otherwise, only copper would have deposited from citrate-added CoFeCu bath. Scanning electron micrographs illustrated that using natural pH (about 5.2) remarkably decreased the number of microvoids in the deposited films compared with the film deposited from conventional baths with pH level of 2.8. EDS, XRD, and VSM were also used for characterization of the deposited films. All deposited films exhibited nanocrystalline structures, and increasing sodium citrate into the baths led to reduction in grain sizes (D) and coercivity (H _c) of the CoFeCu thin films. Plotting log(H _c) versus log(D ⁶) demonstrated that films coercivity followed the “D ⁶ law”. There were only two phase structures (FCC (Co) or BCC (Fe)) observed in the X-ray diffraction patterns of the films. In addition, films with double-phase structures (FCC+BCC) showed finer grain sizes and therefore exhibited lower coercivity in comparison with single-phase (FCC or BCC) films. CoFeCu thin films deposited at higher dosages of sodium citrate (>20 g/L) were poor in diamagnetic copper and consequently showed higher saturation magnetizations.     

Properties of electrochemically deposited CdTe thin films: annealing effect

CdTe thin film have been deposited onto stainless steel and fluorine doped tin oxide coated glass substrates from aqueous acidic bath using electrodeposition technique. The different preparative parameters, such as deposition time, bath temperature, pH of the bath have been optimized by photoelectrochemical (PEC) technique get good quality photosensitive material. The deposited films are annealed at different temperature in presence of air. Annealing temperature is also optimized by PEC technique. The film annealed at 200 °C showed maximum photosensitivity. Different techniques have been used to characterize the as deposited and also annealed (at 200 °C) CdTe thin film. The X-ray diffraction (XRD) analysis showed the polycrystalline nature and a significant increase in the XRD peak intensities is observed for the CdTe films after annealing. Optical absorption shows the presence of direct transition with band gap energy 1.64 eV and after annealing it decreases to 1.50 eV. Energy dispersive analysis by X-ray study for the as-deposited and annealed films showed nearly stoichiometric compound formation. Scanning electron microscopy reveals that spherically shaped grains are more uniformly distributed over the surface of the substrate for the annealed CdTe film. Photovoltaic output characteristics and spectral response of the annealed film have been carried. The fill factor and power conversion efficiency (η) of the cell are found to be 71 and 3.89 %.     

Flat Absorber Phosphorous Black Nickel Coatings for Space Applications

A new process of flat absorber black nickel alloy coating was developed on stainless steel by electrodeposition from a bath containing nickel,zinc and ammonium sulphates;thiocyanate and sodium hypophosphite for space applications.Coating process was optimized by investigating the effects of plating parameters,viz concentration of bath constituents,current density,temperature,pH and plating time on the optical properties of the black deposits.Energy dispersive X-ray spectroscopy showed the inclusion of about 6% phosphorous in the coating.The scanning electron microscopy studies revealed the amorphous nature of the coating.The corrosion resistance of the coatings was evaluated by the electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques.The results revealed that,phosphorous addition confers better corrosion resistance in comparison to conventional black nickel coatings.The black nickel coating obtained from hypophosphite bath provides high solar absorptance (α s) and infrared emittance (ε IR) of the order of 0.93.Environmental stability to space applications was established by the humidity and thermal cycling tests.     

Synthesis and characterization of electroless Ni-P coated graphite particles

Electroless alkaline bath is used to coat Ni-P graphite particles of average size, 150 μm. Amorphous nickel and graphite phases are observed in X-ray diffraction of the coated particles. The crystallite size from diffraction peaks is found to be 9·56 nm. The microstructural studies are carried out with field emission scanning electron microscope (SEM) on the uncoated and coated graphite particles. Uncoated particles showed irregular and fractured surfaces while the surface of coated particles revealed the presence of Ni-P globules. Sizes of Ni-P globules are observed to be in the range 175–250 nm. The presence of Ni and P are confirmed by the energy dispersive spectrometer results. The effect of coating bath composition is studied and an increasing trend in deposition is observed up to 50 gl⁻¹ of stabilizer as well as up to 20 gl⁻¹ of the reducing agent, however, the trend reverses afterwards. The phenomena of nucleation and growth of the Ni-P layer over the graphite surface have been demonstrated through SEM studies and a model has been proposed to demonstrate the growth mechanism of Ni-P globules.