New baths for the deposition of manganese and cobalt oxides

New methods have been adopted for the anodic deposition of the different manganese and cobalt oxides. The deposition of the diferent oxides is usually carried out from their metal salt solutions in presence of a reducing agent. The oxides deposited are as follows: Mn₂O₃ from manganous sulphate in presence of boric, acid and formaldehyde at pH=5.5, Mn₃O₄ from manganous sulphate in presence of formic acid at pH=5.0 MnO from manganous sulphate-ammonium chloride solution in presence of telluric acid, Co₂O₃ from cobalt chloride in presence of telluric acid and sodium fluoride, Co₃O₄ from cobaltite in presence of formaldehyde and potassium chloride and finally CoO from cobalt chloride in presence of alcohol. The results of chemical analysis revealed that the purity of the oxides is 99.99% and their molecular formulae are MnO_1.5, MnO_1.33, MnO, CoO_1.5, CoO_1.33 and CoO respectively.     

Process analysis of electroless nickel deposition baths using optical spectroscopies

Summary The analytical techniques of Vis-spectrophotometry and FTIR spectroscopy have been applied to the quantitative determination of important plating bath constituents of an electroless nickel-phosphorus electrolyte under realistic bath operation conditions. In combination with multivariate calibration methods (partial-least squares (PLS)- and principal component (PCR) regression) Ni²⁺, the reducing agent H₂PO ₂ ^– and its oxidation product HPO ₃ ^– could be directly determined even in the presence of other bath constituents like malic, lactic and adipic acids. For Ni²⁺, absorbance spectra in the 500–900 nm wavelength range were used to develop a PLS calibration model that allows to compensate matrix influences on the Ni²⁺ spectrum. PLS regression was carried out in the concentration range 0.5–6 g l^–1 Ni²⁺ with independently varying bath parameters (concentration of other bath constituents, pH and temperature). Evaluation of the model by predicting the concentrations of test samples which had been drawn from real process solutions of a Ni plating bath yielded a root-mean-squared error of 0.06 g l^–1. The metal concentration of the nickel electrolyte in a compact electroplating unit was monitored in-line by measuring spectra by means of a Vis-spectrometer adapted to the process via quartz glass fiber optical cables of 50 m length. A comparison of the in-line data with potentiometric off-line reference analyses showed good agreement of both data sets with a root mean-squared error of 0.15 g l^–1. The potential of FTIR spectroscopy for process analysis of plating bath solutions could be demonstrated by measuring off-line the concentrations of H₂PO ₂ ^– and HPO ₃ ^– . For these two components calibration samples containing all other main bath constituents were used to set up a PCR calibration model with IR spectra measured in the range from 850 to 1800 cm^–1 with an ATR trough technique. The data showed — within the error of the method of about 10% — generally a good accordance with the stoichiometry of the Ni²⁺/H₂PO ₂ ^– reduction process. The correlation of both parameters which was confirmed in these experiments could allow effective bath control with minimum analytical instrumentation, e.g. only a Vis-spectrophotometer.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Electrochemical deposition of nickel from aqueous electrolytic baths prepared by dissolution of metallic powder

A new method of preparation of aqueous electrolyte baths for electrochemical deposition of nickel targets for medical accelerators is presented. It starts with fast dissolution of metallic Ni powder in a HNO₃-free solvent. Such obtained raw solution does not require additional treatment aimed to removal nitrates, such as the acid evaporation and Ni salt precipitation-dissolution. It is used directly for preparation of the nickel plating baths after dilution with water, setting up pH value and after possible addition of H₃BO₃. The pH of the baths ranges from alkaline to acidic. Deposition of 95% of ca. 50 mg of Ni dissolved in the bath takes ca. 3.5 h for the alkaline electrolyte while for the acidic solution it requires ca. 7 h. The Ni deposits obtained from the acidic bath are physically and chemically more stable and possess smoother and crack-free surfaces as compared to the coatings deposited from the alkaline bath. A method of estimation of concentration of H₂O₂ in the electrolytic bath is also proposed.

     

Voltammetric determination of nickel and palladium in plating baths

Summary A simultaneous determination of nickel and palladium in plating baths was carried out at the hanging mercury drop electrode (HMDE), using the dc and ac single-sweep techniques, direct in the bath sample diluted with ammonia buffer. The influences of Co, Pb, Zn, Cd and the concentration of ammonia buffer on the peak shapes of Ni and Pd and on their resolution were studied. The possible determination of Cd and Pb contamination in plating baths in the same solution by anodic stripping voltammetry is also indicated. The essential advantages of the described method are: its simplicity, rapidity and very small consumption of mercury. The detailed analytical procedure is given. Relative standard deviations were found to be 3.1% for Pd and 2.6% for Ni.     

Stoichiometric measurements in nickel–hypophosphite baths for electroless deposition

Titrimetric methods and ³¹P NMR spectrometry have been compared for the determination of hypophosphite (H₂PO⁻₂) and phosphite (HPO^·-₃) in both alkaline and acid solutions used in the electroless deposition of nickel-phosphorus alloys. It has been shown that reproducible and reliable redox titrimetric methods can be used to follow the charges in concentration of both species with time during the plating process. In addition, measurements of the phosphorus in the nickel deposit by conversion to phosphate in acidic solution and use of flow-injection analysis has enabled satisfactory phosphorus mass-balance in the system to be achieved.     

Origin of the yellow color of complex nickel oxides

Single-crystal optical absorption spectra of NiO, NiTiO₃, NiWO₄, NiV₂O₆, NiNb₂O₆, Ni₂SiO₄, Ni₃V₂O₈, LiNiPO₄, Li₂Ni₂Mo₃O₁₂, SrNiTeO₆, LiScSiO₄:Ni, MgSiO₃:Ni, and (Mg,Ni)₂SiO₄ are presented for the purpose of comparing the spectra of yellow and green Ni²⁺ compounds. Powder spectra of NiTiO₃, NiWO₄, NiV₂O₆, NiNb₂O₆, and Ni₃V₂O₈ in the ultraviolet region help elucidate the more intense charge transfer bands. Bright yellow color results when Ni²⁺ is in a six-coordinated site significantly distorted from octahedral symmetry. Increased absorption intensity occurs when the metal ion d-d bands are in proximity to an ultraviolet charge transfer band.     

Non-destructive method for the analysis of gold(I) cyanide plating baths Complexometric determination of nickel and indium

A method is described for rapid determination of nickel and indium in gold(I) cyanide baths containing large amounts of citric acid and/or sodium citrate, without previous destruction of organic matter. Gold is removed by extraction with ethyl acetate. In one aliquot of the solution indium is masked with thioglycollic acid and nickel is precipitated with sodium diethyldithiocarbamate, extracted into chloroform, stripped into water and determined complexometrically. In a second aliquot indium and nickel are precipitated together with the same reagent and stripped into water, then nickel is masked with 1,10-phenanthroline, and indium is determined by direct titration with EDTA.     

Kinetics of the formation of solid phase in electrolyte for electroless nickel deposition

The effect of 1-(3-methyl-4-phenylpyrazolyl)-3-phenylthiourea (PPTU) on the kinetics of formation of particles of the solid phase in the bulk of electrolyte for nickel plating is investigated by photocolorimetry and photon correlation spectroscopy. It is established that PPTU favors the formation of larger particles as compared to the solution containing no additive and, depending on the concentration, can accelerate or slow down the formation and growth of metal particles and affect the location of the process.     

Structure and growth of oxides on polycrystalline nickel surfaces

The oxidation of polycrystalline nickel (Ni) metal surfaces after exposure to oxygen gas (O₂) at 25 and 300 °C and pressures near 130 Pa, was studied using X‐ray photoelectron spectroscopy (XPS). Oxide structures involving both divalent (Ni²⁺) and trivalent (Ni³⁺) species could be distinguished using Ni 2p spectra, while surface adsorbed O₂ and atomic oxygen (O) species could be differentiated from bulk oxide (O^2?) using O 1s spectra. Oxide thicknesses and distributions were determined using QUASES^?, and the average oxide thickness was verified using the Strohmeier formula. The reaction kinetics for oxide films grown at 300 °C followed a parabolic mechanism, with an oxide thickness of greater than 4 nm having formed after 60 min. Exposure at 25 °C followed a direct logarithmic mechanism with an oxide growth rate about four to five times slower than at 300 °C. Reaction of a Ni (100) single crystal under comparable conditions showed much slower reaction rates compared to polycrystalline specimens. The higher reaction rate of the polycrystalline materials is attributed to grain boundary transport of Ni cations. Oxide thickness was measured on a microscopic scale for polycrystalline Ni exposed to large doses of O₂ at 25 and 300 °C. The thickness of oxide was not strongly localized on this scale. However, the QUASES^? analysis suggests that there is localized growth on a nanometric scale—the result of island formation. Copyright © 2007 John Wiley & Sons, Ltd.     

Impedance measurements for nickel deposition in sulfate and chloride electrolytes

From the analysis of the impedance of nickel deposition, the electrode kinetics is shown to be dependent on the type of anion. In chloride electrolytes a slow electrode activation with cathodic polarization is predominant. In sulfate solutions a low-frequency capacitive feature, favored by a pH decrease, appears to result from interactions between the nickel and hydrogen discharges. An interpretation is proposed where the ad-ion Ni_ads^I acts as both a reaction intermediate and a catalyst associated with a propagating kink site, and where the adsorbed species H_ads^*, generated by the presence of Ni_ads^I, inhibit the hydrogen evolution. It is concluded that the active area is closely connected to the coverages by adsorbates.     

Growth of iron cobalt oxides by atomic layer deposition

Thin films of iron cobalt oxides with spinel-type structure are made by the atomic layer deposition (ALD) technique using Fe(thd)3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione), Co(thd)2, and ozone as precursors. Pulse parameters for ALD-type growth are established and such growth can be achieved at deposition temperatures between 185 and 310 degrees C. Films have been deposited on amorphous soda-lime glass and single-crystalline substrates of Si(100), MgO(100), and alpha-Al2O3(001) which all provide crystalline films, but with various orientations and crystallite sizes. Application of an external magnetic field during the film growth does not influence film growth characteristics (growth rate, crystallinity, topography etc.). Magnetization data are reported for phase-pure films of spinel-type structure with composition Fe2CoO4.     

Interwoven nickel(II)-dimethylglyoxime nanowires in 3D nickel foam for dendrite-free lithium deposition

Metal skeletons, such as Nickel Foam (NF) has attracted worldwide interests as stable host for lithium metal anode because of its high stability, large specific surface area and high conductivity. However, most metal skeletons have lithophobic surface and uneven current distribution that result in sporadic lithium nucleation and uncontrolled dendrites growth. Herein, we describe a sequential immersing strategy to generate interwoven Nickel(II)-dimethylglyoxime (Ni-DMG) nanowires at NF to obtain composite skeleton (NDNF), which can be used as an stable host for Li metal storage. The Ni-DMG has proved effective to realize uniform lithium nucleation and dendrite-free lithium deposition. Combing with the three dimensional (3D) hierarchical porous structure, the composite host shows a significantly improved coulombic efficiency (CE) than pristine commercial nickel foam. Moreover, the corresponding Li||Li symmetrical cells can run more than 700 h with low voltage hysteresis 22 mV at 1.0 mA/cm², and Li@NDNF||LiFePO₄ full-cell exhibits a high capacity retention of 82.03% at 1.0 C during 630 cycles. These results proved the effectiveness of metal-organic complexes in governing Li metal growth and can be employed as a new strategy for dendrite-free Li metal anode and safe Li metal batteries (LMBs).     

Kinetic regularities of the chemical vapor deposition of nickel layers from bis-(ethylcyclopentadienyl)nickel

Physicochemical regularities of the nickel layers chemical vapor deposition from bis-(ethylcyclopentadienyl)nickel were studied. Dependences of the growth rate of nickel layers on the deposition temperature, gas-flow linear rate, partial pressures of reagents, and substrate roughness, and also dependences of the thickness of a grown layer on time and on the position of a substrate on a susceptor were obtained.     

New volatile strontium and barium imidazolate complexes for the deposition of group 2 metal oxides

We report the synthesis, characterization, and experimental density function theory-derived properties of new volatile strontium and barium imidazolate complexes, which under atomic layer deposition conditions using ozone as a reagent can deposit crystalline strontium oxide at 375 °C.     

Simultaneous determination of pH, chloride and nickel in electroplating baths using sequential injection analysis

A sequential injection analysis system was developed to quantify pH, chloride and nickel in electrolytic baths, in the ranges 1-5 pH units, and 0.1-1.0 and 0.1-1.6 mol l⁻¹, respectively. To enable pH and chloride determination, potentiometric detection with two ion-selective electrodes in a tubular configuration was used. Nickel concentrations were assessed using colorimetric detection at 660 nm. pH was determined prior to nickel determination and just after sample injection (500 μl) into a 0.025 mol l⁻¹ phosphate buffer carrier stream at pH 6.3 and a 9.10 ml min⁻¹ flow rate. For chloride determination, on-line dialysis through a cellulose membrane was used to enable sample dilution and matrix separation. A 2⁵⁻¹ fractional factorial design based on the carrier solution composition and the levels of the hydrodynamic parameters was used for system optimization. At the optimized settings a sampling rate of 40 samples h⁻¹ was attained, with precision and accuracy statistically indistinguishable from those achieved with conventional procedures.     

Simple and low-cost electrochemical sensor based on nickel nanoparticles for the determination of cabergoline

Cabergoline (CAB) is an ergot alkaloid derivative with dopamine agonist activity. In this work for the first time the electrocatalytic oxidation of CAB was carried out with nickel nanoparticles-modified carbon paste electrode using cyclic voltammetry, chronoamperometry, chronocoulometry and amperometry methods. At first, nickel nanoparticles were synthesized by non-aqueous polyol method and these nanoparticles were mixed with graphite powder to form modified carbon paste electrode. The resulting modified electrode was characterized by scanning electron microscope images. In the presence of 0.1 M NaOH a good redox behavior of the Ni(III)/Ni(II) couple at the surface of the electrode can be observed. CAB was successfully oxidized at the surface of the modified electrode. The electrocatalytic oxidation peak current of this drug was linearly dependent on its concentration. The proposed sensor exhibited a high sensitivity and was successfully applied for the determination of CAB in real samples.     

Synthesis of an efficient catalyst based on nickel and chromium oxides for hydrogenation reactions

The dissolution of nickel metal in nitric acid in the presence of the dichromate anion as the oxidizer is reported. The formation of Ni(II) and Cr(III) nitrates takes place in two steps with the intermediate formation of nitrous acid. A new method to synthesize the nickel-chromium oxide catalyst from nickel and chromium nitrate solutions is suggested, in which the solutions are obtained by an environmentally friendly technology from nickel metal, chromium(VI) oxide, and nitric acid. The catalyst is highly active and selective in benzene hydrogenation and in CO preferential hydrogenation in the presence of CO₂.     

Pulsed electrochemical deposition of nickel oxides on multi-walled carbon nanotubes from EDTA alkaline solutions: a SEM,XPS, and voltammetric characterization

A study regarding the electrodeposition of nickel oxide particles on the activated multi-walled carbon nanotubes from 2 M NaOH solution containing Ni(NO₃)₂ and EDTA was carried out. The electrodeposition process was carried out using an optimized double-pulse sequence of potentials: E ₁ = ?0.2 V vs. SCE (t ₁ = 0.3 s) and E ₂ = 0.7 V vs. SCE (t ₂ = 0.03 s). Spectroscopic XPS investigations and SEM analysis were used in order to characterize the surface and morphology of the studied modified electrode. Cyclic voltammetry and chronoamperometry were used in order to evaluate the electrochemical/amperometric performance of the GC/MWCNT-Ni electrode toward the oxidation of some aliphatic alcohols in strong alkaline medium.