Initial stages of copper electrodeposition from acidic sulfate solution in the presence of alklpyridinium hydrosulfate ionic liquids

The effect of two alklpyridinium hydrosulfate based ionic liquids(ILs)including N-butylpyridinium hydrogen sulfate(BpyHSO4)and N-hexylpyridinium hydrogen sulfate(HpyHSO4)as additives on the nucleation and growth of copper from acidic sulfate bath was investigated using cyclic voltammetry,chronoamperometric and scanning electron microscopy techniques.Results from cyclic voltammetry indicated that the two studied additives had a blocking effect on copper electrodeposition process and this effect initiated by HpyHSO4was more pronounced in comparison to BpyHSO4.Dimensionless chronoamperometric current-time transients for the electrodeposition of copper from the bath free of additives were in good accord with the theoretical transients for the limiting case of instantaneous three-dimensional nucleation with diffusion-controlled growth of the nuclei.However,the instantaneous nucleation mechanism observed in the additive-free bath was changed to a more progressive one when additives were present in the bath.Surface morphology analysis indicated that alklpyridinium hydrosulfate ILs can induce the formation of leveled and finer grained deposits by the adsorption of additive at the first stages of deposition process,leading to decrease of the nucleation and growth rate of nuclei.     

Synthesis of PVP stabilized Cu/Pd nanoparticles with citrate complexing agent and its application as an activator for electroless copper deposition

A simple method has been developed to synthesize Cu/Pd nanoparticles in aqueous solution in ambient condition with the addition of complexing agent, trisodium citrate. UV-vis spectra confirmed the complexing behavior of trisodium citrate and metal ions. The particles synthesized with trisodium citrate were well dispersed with particle size ranging between 3-4 nm while the particles without trisodium citrate were larger and aggregated, as demonstrated by transmission electron microscopy (TEM). X-ray diffraction patterns (XRD) indicated the formation of bimetallic nanoparticles without impurities in the complexing agent-supplemented system. In contrast, large amounts of PdO and Cu(OH)(2) were precipitated along with the formation of particles in the complexing agent-free system. X-ray photoelectron spectroscopy (XPS) revealed small amounts of oxidized Pd on the surface of particles and the existence of zerovalent Cu and oxidized Cu in particles with trisodium citrate. With a simpler process for electroless copper deposition, the Cu/Pd nanoparticle activator with less Pd metal used exhibited comparable catalytic activity to conventional Pd/Sn colloidal activator. In summary, application of Cu/Pd nanoparticles synthesized with the complexing agent as an activator suggested a novel, simpler and inexpensive process in PCB industry.     

Potentiometric determination of free acidity and uranium in uranyl nitrate solutions using sulfate as complexing agent

In this paper free acid and uranium present together in the range of 0.05–3.0 meq and 20–250 mg, respectively, have been determined by potentiometric titration, using Na₂SO₄ and (NH₄)₂SO₄ complexants and NaOH and Na₂CO₃ as titrants. The results are presented as percentage recovery of free acidity and uranium over the range studied. It has been shown that percentage recovery of free acidity suggests a bias which varied from –5% to +74% at different free acidity and uranium concentrations for the Na₂SO₄–NaOH, Na₂SO₄–Na₂CO₃ and (NH₄)₂SO₄–NaOH complexant — titrant combinations. The percentage recovery of uranium always showed a positive bias which could be up to +8% for extreme free acidity — uranium ratios in the case of Na₂SO₄–Na₂CO₃ complexant — titrant combination. For the other Na₂SO₄–NaOH and (NH₄)₂SO₄–NaOH complexant — titrant combinations a positive bias of up to only +4% has been noticed.     

Sodium citrate as an eco-friendly complexing agent for the bioscouring treatment of the cellulosic/lignocellulosic fabrics

A 50% of cotton–50% of flax fabric was subjected to an enzymatic treatment (bioscouring) in ultrasound for removing the compounds which could negatively affect the further specific technological processes as whitening and dyeing. During the scouring process, some parameters of the fabrics are improved. Even EDTA is usually used as a chelating agent in the pretreatments of the fabrics, recent studies aimed to identify new biodegradable complexing agents. In this study, we present the results obtained for bioscouring treatment of the cellulosic/lignocellulosic fabrics in the presence of sodium citrate as a complexing agent. The treatments were made in 0.1 M phosphate buffer of pH 8 and ultrasound media. The samples were immersed in an aliquot containing the commercial pectinolytic product BEISOL PRO, Denimcol Wash-RGN as a surfactant and sodium citrate or EDTA (ethylenediaminetetraacetic acid). The reactions were conducted by varying the enzyme concentration and action time using a central, rotatable second-order compound program. All the parameters determined after bioscouring [weight loss, hydrophilicity, whiteness index, yellowness index, tensile strength, elongation at break, the relative absorbance (A₁₇₃₁) from FT-IR spectra, color strength (K/S) and color difference (ΔE*ab)] of the investigated samples showed in the case of sodium citrate (an eco-friendly biodegradable compound) treatments better or comparable values to treatments conducted using EDTA (non-biodegradable compound).     

添加剂丙烯基硫脲对镍电沉积的影响研究

采用循环伏安、线性扫描和恒电位阶跃电化学方法结合扫描电镜研究了不同浓度的丙烯基硫脲(ATU)对NH₃-NH₄Cl-H₂O体系镍在玻碳电极上的电沉积过程的影响. 循环伏安测试、线性扫描以及恒电位暂态曲线一致表明ATU的加入对镍电沉积具有阻化作用,并且随着ATU浓度的增加其阻化作用增强;恒电位暂态曲线结果表明,镍的电结晶是按瞬时形核三维生长机理进行的,随外加电位负移,晶体向外生长速率增大;ATU的加入没有改变镍的形核方式,但形核数密度增大,并且减小晶体向外生长的速率;扫描电镜结果表明,ATU的加入可以细化晶粒,得到整平、致密的镍沉积层.     

Parameters of electrical double layer on the boundary copper electrode/water-organic solution of copper sulfate

By the method of impedance spectroscopy the properties of the phase boundary of Cu|H₂O + i-C₃H₇OH + CuSO₄ system were investigated. The impedance hodographs were obtained, in the form of circles with displaced centers. The capacity values of electrical double layer, exchange currents, and resistance of the electrolyte solution depending on the mole fraction of 2-propanol were determined. The role of organic component in the formation of the electrical double layer in the studied system is elucidated.     

Cyclopentanone thiosemicarbazone, a new complexing agent for copper determination in biological samples by adsorptive stripping voltammetry.

A selective and sensitive stripping voltammetric method for the determination of trace amounts of copper(II) with cyclopentanone thiosemicarbazone (CPTSC) is presented. The method is based on the adsorptive accumulation of the resulting copper-CPTSC complex on a hanging mercury drop electrode, followed by the stripping voltammetric measurements at the reduction current of the adsorbed complex at -0.37 V vs. Ag/AgCl. The optimal conditions for the stripping analysis of copper include pH 9.3, deposition time of 120 s, and a deposition potential of -0.1 V (vs. Ag/AgCl). The peak current is linearly proportional to the copper concentration over a range 3.14 x 10(-9) M to 1.57 x 10(-6) M with a limit of detection of 1.57 x 10(-9) M. The technique has been applied to the determination of copper in biological samples, like urine and whole blood.     

Use of tetracycline as complexing agent in radiochemical separations

The use of the antibiotic agent tetracycline for analytical purposes in solvent extraction procedures is presented. Individual extraction curves for the lanthanides, zinc, scandium, uranium, thorium, neptunium and protactinium were obtained. Separation of those elements one from another, and of uranium from selenium, bromine, antimony, barium, tantalum and tungsten was carried out. In all cases benzyl alcohol was the diluent used to dissolve tetracycline hydrochloride. Sodium chloride was used as supporting electrolyte for the lanthanide separations and sodium perchlorate for the other elements mentioned. Stability or formation constants for the lanthanide complexes as well as for thorium complex with tetracycline were determined by using the methods of average number of ligands, the limiting value (for thorium), the two parameters and the weighted least squares. For the lanthanides, the stability constants of the complexes Ln(TC)₃ go from 9.35±0.22 for lanthanum up to 10.84±0.11 for lutetium. For the Th(TC)₄ complex the formation constant is equal to 24.6±0.3. Radioisotopes of the respective elements were used for the determinations. When more than one radioelement was present in an experiment, a multichannel analyser coupled to Ge(Li) or NaI(Tl) detectors was used for counting the activities. When only one radioisotope was used, counting of the radioisotopes was made with a single-channel analyser (integral mode counting) coupled to a NaI(Tl) detector. Uranium was determined by activation analysis (epithermal neutrons). Radioisotopes of the elements were obtained by irradiation in the IPEN swimming-pool reactor. The natural radioisotope^{2 3 4}Th was used as label in the thorium experiments. In some separation procedures such as in the case of the pair uranium-neptunium, and of the pair scandium-zinc, the separation was obtained by properly adjusting the pH value of the aqueous phases, before the extraction operation. In other cases, addition of masking agents to the extraction system was required in order to perform the separation between the elements under study. In this way ethylenediaminetetraacetic acid (EDTA) was used as masking agent for scandium and the lanthanides in order to allow separation of uranium from those elements. Diethylenetriaminepentaacetic acid (DTPA) was used as masking agent for thorium in order to extract uranium into the organic phase. Separations of protactinium from thorium, and of uranium from protactinium and thorium, were accomplished by using sodium fluoride as masking agent for protactinium and DPTA as masking agent for thorium and protactinium at the same time. In the case of the separation of the lanthanides one from another it is necessary to resort to a multi-stage extraction procedure since the stability constants for those elements are too close.     

Simultaneous ion-chromatography of alkali, alkaline earth and heavy metal ions with conductivity and indirect UV detection: Comparison of eluents containing organic complexing acids and copper sulfate

Summary The simultaneous ion-chromatography of mono-and divalent metal ions on the weak cation-exchange column Nucleosil-PBDMA (polymer coated silica with polybutandiene-maleic acid) with conductivity and indirect UV-detection is presented. The influences of eluents containing organic complexing acids (-hydroxy-isobutyric, tartaric, citric, oxalic, pyridine-2,6-dicarbonic acid and EDTA etc.) as well as UV-absorbing, displacing counterions [Cu(II), Ce(III) etc.] on the retention times of metal ions was investigated in detail. With the combination of citric acid-PDCA as eluent all alkali and alkaline earth ions could be completely separated within 12 min. Alkali, alkaline earth and heavy metal ions [Cu/Zn/Co/Fe(II)] were separated by the combination of tartaric and oxalic acid as eluent in a single run. Trace amounts of Na, K and Ca were successfully separated from the Mg-matrix by an EDTA-PDCA eluent. For the IC with indirect UV-detection the eluent consisting of CuSO₄ or CuCl₂ was used to separate Na, K, Mg and Ca with baseline resolution within 10 min.The detection limits of metal ions with conductivity detection were found beween 0.5 g/l for Li and 8 g/l for Cs. They were 10 times more sensitive than those with indirect UV-detection.This IC-method was applied to determine alkali, alkaline earth and Mn ions in the water, food, ore-cinder and sole-brine samples with satisfactory results.Dedicated to Prof. Dr. G. Schulze on the occasion of his 60th birthday     

Inhomogeneous electrodeposition of copper in a magnetic field

Normally, magnetoconvection driven by the Lorentz force increases the limiting current in the mass-transport limited regime, roughly as the one-third power of the applied magnetic field. Here we show that an applied field can actually diminish the rate of copper electrodeposition at low overpotentials. The effect is related to the formation of a vortex at the leading edge of the flow. Similar, but weaker effects are due to gravity.     

Peculiarities of metal electrodeposition inside a flow-through porous electrode with low initial conductivity in oxidant containing solution

The earlier developed dynamic model of a flow-through electrode is used for studying how the variations in initial conductivity of a porous matrix κ_s,ini and a metal deposit affect the rate of metal deposition from an oxidant-containing solution for the direct-flow operation mode of the porous electrode. It is found that in contrast to an oxidant-free solution in which the decrease of κ_s,ini improves the uniformity of deposit distribution inside the porous cathode and increases the deposit final mass m _f, the opposite situation is observed in the presence of an oxidant, namely, a decrease in κ_s,ini, under otherwise similar conditions reduces the deposit mass and leads to its specific spatial distribution. The final metal deposit is divided into two separate fragments (rear and front) with a region of low conductivity of the initial porous matrix in between. Dynamics of the current and metal redistribution within the porous electrode, the reasons for the formation and stabilization of the rear fragment of coating, the correlation between the metal deposition rate and changes in the anodic zone position and intensity are discussed. It is shown that with the appearance of a specific profile of deposit distribution, the dependence of m _f on the metal conductivity develops a limit that differs considerably from the deposit final mass for an equipotential porous electrode.     

Impedance of a passive iron electrode in a solution containing a reducing agent

Frequency dependences of impedance of a passive iron electrode in 0.5 M Na₂SO₄ solutions with and without 0.01 M K₄[Fe(CN)₆] are obtained by a pulsed method and the Fourier transform. At 1–1000 Hz, the results in 0.5 M Na₂SO₄ satisfactorily agree with our previous results obtained by a lock-in method. With the [Fe(CN)₆]^4- ions present, the impedance decreases faster at lower frequencies. The impedance of the oxide film/solution interface relaxes longer the film impedance. These conclusions are similar to those obtained earlier.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 97–101.Original Russian Text Copyright © 2005 by Klyuev, Rotenberg, Batrakov.To the Centennial of B.N. Kabanov.     

Study of copper electrodeposition from acidic sulfate and perchlorate electrolytes using faradaic impedance spectroscopy and quartz microbalance methods

Copper electrodeposition from acidic sulfate and perchlorate electrolytes is studied. Some measurements are performed with addition of gelatine as a surface active agent. In the course of microgravimetric studies, decrease of the derivative of the electrode mass variation by the consumed charge is found, as compared to the value corresponding to the current efficiency of 100%. The latter is in part related to the effect of the double layer structure on the rate of the consecutive stages of copper recharge (Cu²⁺ + e → Cu⁺) and deposition (Cu⁺ + e → Cu). This effect is most pronounced in the case of solutions containing surface active agents that cause hyperpolarization and extension of the monovalent copper stability range as a result of their adsorption on the electrode surface. The faradaic impedance spectra obtained in sulfate and perchlorate electrolytes evidence at least the difference in the rate constants of recharge and copper deposition in these electrolytes. In both cases, the recharge rate constant is considerably lower than the deposition rate constant. The difference between these constants decreases noticeably at the addition of surface active agents.     

Kinetic Monte Carlo simulations of nucleation and growth in electrodeposition

Nucleation and growth during bulk electrodeposition is studied using kinetic Monte Carlo (KMC) simulations. Ion transport in solution is modeled using Brownian dynamics, and the kinetics of nucleation and growth are dependent on the probabilities of metal-on-substrate and metal-on-metal deposition. Using this approach, we make no assumptions about the nucleation rate, island density, or island distribution. The influence of the attachment probabilities and concentration on the time-dependent island density and current transients is reported. Various models have been assessed by recovering the nucleation rate and island density from the current-time transients.     

Percolation effects with copper electrodeposition in ion-exchange material

The effect of preliminary doping of sulfo cation-exchange material KU-23 15/100S with a chemically deposited metal (Ag, Cu) on the rate of copper ion electroreduction is investigated. It is shown that the threshold dependence of the reaction current of copper electroreduction on the amount of doped metal is due to the formation of a single percolation cluster in an ion-exchange grain and, as a result, to the appearance of electron conductivity. It is established that preliminary doping changes the nucleation mechanism from a gradual to an instantaneous one. Results from a local X-ray spectral microanalysis provide the basis for concluding that copper electrodeposition is uniform throughout the volume of an ion-exchange grain. The average size of the copper particles formed is 100 nm.