Transient natural convection induced by electrodeposition of Li+ ions onto a lithium metal vertical cathode in propylene carbonate

Transient natural convection caused by Li⁺ electrodeposition at constant current along a vertical Li metal cathode immersed in a 0.5 M LiClO₄–PC (propylene carbonate) electrolyte was compared with that by Cu²⁺ ion electrodeposition in aqueous CuSO₄ solution. The concentration profile of the Li⁺ ions was measured in situ by holographic interferometry. The interference fringes start to shift with time at a higher current density. The concentration boundary layer thickness for Li⁺ ions was successfully determined. With the progress of electrodeposition, the density difference between the electrolyte at the cathode surface and the bulk electrolyte increased to induce upward natural convection of the electrolyte. The electrolyte velocity was measured by monitoring the movement of tracer particles. The measured transient behavior of the ionic mass and momentum transfer rates normalized with respect to the steady-state value was numerically analyzed. Transient natural convection along a vertical cathode due to Li metal electrodeposition can be reasonably explained by boundary layer theory, similar to the case of Cu electrodeposition in aqueous CuSO₄ solution.     

Cadmium electrodeposition on copper substrate for cyclotron production of <Superscript>111</Superscript>In radionuclide

^natCd electrodeposition on a copper substrate was investigated for production of ¹¹¹In radionuclide. The electrodeposition experiments were carried out by alkaline plating baths. Operating parameters such as pH, temperature, and current density are also optimized. The current efficiency was measured at different current densities. The optimum conditions of the cadmium electrodeposition were as follows: 2.35 g L⁻¹ cadmium, pH = 13, DC current density of ca 4.27 mA cm⁻² at 25 °C temperature with 62.48 μm thickness. SEM photomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath.     

Surface’s weights of electrodeposited thorium samples determined by alpha spectrometry

The aim of this work was the preparation of samples with thorium on the steel discs by electrodeposition for determination of natural thorium by alpha spectrometry and for following analysis by secondary ion mass spectrometry. The samples with ²³²Th isotope were prepared by electrodeposition from solution Th(NO₃)₄·12H₂O on steel discs in electrodeposition cell with use of solutions of Na₂SO₄, NaHSO₄, KOH and ammonia oxalate by electric current of 0.75 A. Weights of electrodeposited thorium samples were calculated on the basis of intensities of peak of ²³²Th isotope in the alpha spectra. The layer thickness was calculated for following analysis of surface layers of thorium using secondary ion mass spectrometry.     

Utilization of electrodeposition for electrothermal atomic absorption spectrometry determination of gold

Gold was determined by electrothermal atomic absorption spectrometry after electrochemical preconcentration on the graphite ridge probe used as a working electrode and sample support. The probe surface was electrochemically modified with Pd, Re and the mixture of both. The electrolysis of gold was performed under galvanostatic control at 0.5 mA. Maximum pyrolysis temperature for the probe surface modified with Pd was 1200 °C, with Re 1300 °C. The relative standard deviation for the determination of 2 μg l^− 1 Au was not higher than 5.6% (n = 8) for 2 min electrodeposition. The sensitivity of gold determination was reproducible for 300 electrodeposition and atomization cycles. When the probe surface was modified with a mixture of Pd and Re the detection limit was 31 ng l^− 1 for 2 min electrodeposition, 3.7 ng l^− 1 for 30 min, 1.5 ng l^− 1 for 1 h and 0.4 ng l^− 1 for 4 h electrodeposition, respectively. The procedure was applied to the determination of gold in river water samples. The relative standard deviation for the determination of 2.5 ng l^− 1 Au at 4 h electrodeposition time at 0.5 mA was 7.5%.     

An improved method for determination of uranium isotopic composition in urine by alpha spectrometry

A comparative study of source preparation techniques to determine uranium isotopic composition by alpha spectrometry, namely electrodeposition and chemical stripping with polymeric membranae containing trioctylphosphine oxide (TOPO), is presented. The mean yield obtained for electrodeposition and TOPO deposition were 85% and 74%, respectively. The mean activity ratio²³⁵U/²³⁸U were 0.044 and 0.042 and the ratio²³⁴U/²³⁸U were 0.994 and 1.009, using electrodeposition and TOPO deposition techniques, respectively. The method of uranium separation from urine using an ion-exchange resin Dowex 1×8, chloride form and citrate form, was also studied. The obtained global yields of these methods were 50% and 41%, respectively.     

Effect of Anionic Electrolytes and Precursor Concentrations on the Electrodeposited Pt Structures

Electrodeposition of functional metal surfaces has received great attention because of their useful applications. Recently, interesting electrodeposition behavior of Pt at −0.8 V (vs. Ag/AgCl) was reported, where underpotential deposited H (H_upd) layers played a unique role in the electrodeposition. Here, we report the effect of anionic electrolytes and precursor concentrations on the electrochemical deposition behavior of Pt. Depending on these two experimental parameters, two distinct Pt structures, monolayer Pt films and Pt spheres, were electrodeposited at −0.8 V. In addition to the underpotential deposited H (H_upd) layers formed at −0.8 V, the adsorption of Cl⁻ also plays a significant role in determining the electrodeposited Pt structures. When the PtCl₄²⁻ concentration was low and the Cl⁻ concentration was high enough for the adsorption of PtCl₄²⁻ to be blocked by the H_upd and Cl⁻ layers, monolayer Pt films were electrodeposited. Otherwise, further electrodeposition of Pt spheres over the monolayer Pt films occurred. The effect of other halide ion adsorption and the controlled growth of Pt spheres during the Pt electrodeposition were also investigated. The electrochemical deposition behavior of Pt demonstrated in this work provides insight into the fabrication of functional Pt surfaces.     

Electrodeposition and determination of nano-scale uranium and plutonium using alpha-spectroscopy

Summary A simple method was used to design and set up an electrodeposition device for the alpha-emitting nuclides. The designed electroplating facility is leak proof and simple in operation and dismantled. The effect of current, pH of electrolyte, and the plating time on the electrodeposition efficiency have been investigated in a sodium bisulphate, sulphuric acid electrolyte in order to determine the optimum conditions. It was shown that a current of 900-1000 mA, plating time of 80-90 minutes and pH range of 2-2.3 are the best conditions for deposition of nano-scale uranium and plutonium. In these circumstances, it was possible to deposit 0.004 ng ^. g^-1 Pu and 60 ng ^. g^-1 U in an electroplating planchette. The device and modified procedures were successfully applied for soil samples. Prior to electrodeposition of the elements, a column extraction chromatography has been used to separate the Pu and U and eliminate most matrix and interferences in environmental samples.     

Studies on gaseous electrodeposition of recoiled nuclides from thorium series

A point source of²¹²Pb was prepared from²²⁸Th source by the gaseous electrodeposition method. A conical tube was placed between the electrodes and it served as a metallic shade to make lines of electric force converge to the collector cathode. The source was utilized to measure the rate of²⁰⁸Tl emission and the rate of electrodeposition in various gaseous matrices. The mechanism of the mass transfer of recoiled species from the source to the collector was also revealed predominantly to be migration of the recoiled ions.     

Speciation of Aluminium in Mixtures of the Ionic Liquids [C3mpip][NTf2] and [C4mpyr][NTf2] with AlCl3: An Electrochemical and NMR Spectroscopy Study

This paper reports on the electrodeposition of aluminium on several substrates from the air‐ and water‐stable ionic liquids 1‐propyl‐1‐methylpiperidinium bis(trifluoromethylsulfonyl)amide ([C₃mpip][NTf₂]) and 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C₄mpyr][NTf₂]), which contain anhydrous AlCl₃. At an AlCl₃ concentration of 0.75 molal, no evidence for aluminium electrodeposition was observed in either system at room temperature. However, aluminium electrodeposition becomes feasible upon heating the samples to 80 °C. Aluminium electrodeposition from bis(trifluoromethylsulfonyl)amide‐based ionic liquids that contain AlCl₃ has previously been shown to be very dependent upon the AlCl₃ concentration and has not been demonstrated at AlCl₃ concentrations below 1.13 molal. The dissolution of AlCl₃ in [C₃mpip][NTf₂] and [C₄mpyr][NTf₂] was studied by variable‐temperature ²⁷Al NMR spectroscopy to gain insights on the electroactive species responsible for aluminium electrodeposition. A similar change in the aluminium speciation with temperature was observed in both ionic liquids, thereby indicating that the chemistry was similar in both. The electrodeposition of aluminium was shown to coincide with the formation of an asymmetric four‐coordinate aluminium‐containing species with an ²⁷Al chemical shift of δ=94 and 92 ppm in the [C₃mpip][NTf₂]–AlCl₃ and [C₄mpyr][NTf₂]–AlCl₃ systems, respectively. It was concluded that the aluminium‐containing species that give rise to these resonances corresponds to the electroactive species and was assigned to [AlCl₃(NTf₂)]^?.     

Determination of cadmium, chromium and copper in high salt samples by LA-ICP-OES after electrodeposition—preliminary study

A novel method is presented for determination of heavy metal ions in a high-saline matrix. It is based on the electrodeposition of the ions and subsequent laser ablation coupled to inductively coupled plasma optical emission spectrometry (LA-ICP-OES). Three arrangements for electrodeposition were worked out, two of them with stationary working electrodes. Materials for use in the working electrodes, and conditions for electrodeposition of Cd, Cr and Cu (pH, deposition current, time of electrolysis) were studied. Nickel was found to be the best electrode material. The metals accumulate on the surface of electrode and were then evaporated/ablated with a Nd:YAG laser focused into the ICP-OES spectrometer. The detection limits are 0.13 mg?L^?1 for Cd, 0.15 mg?L^?1 for Cu, and 1.9 mg?L^?1 for Cr in case of a stationary bottom working electrode, and 0.25 mg?L^?1 for Cd, 0.05 mg?L^?1 for Cu, 0.8 mg?L^?1 for Cr when using a rotating electrode. The relative standard deviation is in range from 3.8 to 10.3%. Waste water was analyzed in this way by the standard addition method.     

Determination of silver in solution with a piezoelectric detector after electrodeposition

Silver in solution is determined in situ by frequency change of a piezoelectric quartz crystal due to electrodeposition on the electrode of the crystal immersed in the solution. A test solution containing EDTA for masking other metal ions flows through a thermostated cell which contains the crystal with platinum-plated electrodes. The frequency change is proportional to the silver concentration in the range 10^?6?3 × 10^?5 M after electrodeposition for 10 min, and 2 × 10^?7?1 × 10^?6 M for 1 h.     

Gold nanoparticles-carbon nanotubes modified sensor for electrochemical determination of organophosphate pesticides

An electrochemical sensor was developed for the detection of organophosphate pesticides based on electrodeposition of gold nanoparticles on a multi-walled carbon nanotubes modified glassy carbon electrode. Cyclic voltammetry was employed in the process of electrodeposition. Field emission scanning electron microscope and X-ray diffraction techniques were used for characterization of the composite. Organophosphate pesticides (e.g. parathion) were determined using linear scan voltammetry. A highly linear response to parathion in the concentration range from 6.0?×?10^?5 to 5.0?×?10^?7 M was observed, with a detection limit of 1.0?×?10^?7 M estimated at a signal-to-noise ratio of 3. The method has been applied to the analysis of parathion in real samples.     

Radiometric determination of uranium in natural waters after enrichment and separation by cation-exchange and liquid-liquid extraction

Preconcentration of uranium from natural water samples using Chelex-100 cation-exchange resin, its selective extraction by tributylphosphate and electrodeposition on stainless steel discs is reported. The validity of the separation procedure and the chemical recoveries were checked by addition of uranium standard solution as well as by tracing with ²³²U. The average uranium yield for the cation-exchange was (97±2)%, for the liquid-liquid extraction was (95±2)% and for the electrodeposition was more than 99%. Employing high-resolution a-spectroscopy, the measured activity of ²³⁸U and ²³⁴U radioisotopes was found to be ~7 mBq^.l^-1 and ~35 mBq^.l^-1 for ground- and seawater samples, respectively. The energy resolution (FWHM) of the α-peaks was 22 keV, the minimum detectable activity (MDA) was estimated to be 1 mBq^.l^-1 (at 95% confidence limit). This revised version was published online in July 2006 with corrections to the Cover Date.     

Role of Complex Formation in Mass Transport during Nickel Electrodeposition from Low-Concentration Formate–Chloride Electrolytes

Nickel electrodeposition from 0.2 M formate–chloride solutions is studied. Depending on electrolyte pH₀, the highest current density of the electrodeposition of compact nickel deposits varies from 3 (pH₀3.5) to 40 A dm^–2(pH₀2.0). With the current efficiency for nickel taken into account, this corresponds to nickel deposition rates of 3 to 25 A dm^–2. One of the reasons for the high permissible current densities is good buffer properties of the electrolyte. Computer calculations show that the considerable acceleration of the nickel electrodeposition is due to mass transport accelerated by the formation of complex [NiL]⁺cations. The complex formation also affects the intensity of interaction between nickel and hydrogen ions transported to the cathode. The current by nickel increases due to the participation of formic acid molecules in the hydrogen evolution.     

Electrodeposition of lead on to a graphite probe for electrothermal atomic absorption spectrometry

A simple system for controlled potential electrodeposition on to a graphite probe electrode is described. Totally pyrolytic graphite was found to be better for electrodeposition than microporous glassy carbon or electrographite coated with pyrolytic graphite. Lead can be deposited by anodic and cathodic processes as PbO₂ and Pb, respectively. Potentials of + 1.2 to + 2.0 V were best for anodic deposition and – 0.8 to– 2.0 V were best for cathodic deposition. With an electrodeposition time of 120 s, AAS sensitivity gains of × 9 and × 3.5 were achieved for anodic and cathodic deposition, respectively, in comparison with the results obtained by direct injection of 20 1 sample volumes on to the probe. The lead cathodic process was unaffected by NaCl concentrations up to 10^–2 M, but only 10^–3 M NaCl could be tolerated by anodic deposition.     

Electrolytical microcell for on-line preconcentration of trace metals in flow systems

Summary The separation of trace metals from solutions of electrolytes by electrodeposition in a 30 l electrolytical flow-through cell was studied. The working electrode of the flow cell was made from powdered spectral or glassy carbon. The electrodeposition is complete for Cu²⁺, Cd²⁺, Mn²⁺ and Pb²⁺, partial for Zn²⁺, Fe³⁺ and Ni²⁺. Mn²⁺ and Pb²⁺ can also be deposited by anodic oxidation on the working electrode. The deposition is complete up to sample flow rates of 3–4 ml/min. The deposited elements are dissolved by short-circuiting the electrodes and flushing the cell with diluted acid. The dissolved elements are determined on-line by flame AAS. Data evaluation through peak area measurement is discussed.     

Determination of heavy metals by electrothermal atomic absorption spectrometry after electrodeposition on a graphite probe

Traces of heavy metals were separated and preconcentrated electrochemically at a controlled potential on the graphite ridge probe. After the electrolysis, the electrode-probe was inserted in the graphite furnace for atomization of metal deposit by an automatic system. Conditions for the electrodeposition, such as pH of solutions, the deposition potential and concentration of electrolyte, were optimized. Detection limits improved with increased time of electrodeposition and were 16 ng l⁻¹ Cu, 1.0 ng l⁻¹ Cd, 6.0 ng l⁻¹ Pb, 64 ng l⁻¹ Ni, 14 ng l⁻¹ Cr (III) and 17 ng l⁻¹ Cr (VI) for a 10-min deposition. This method was applied for the determination of copper, cadmium, lead, nickel and of chromium species in seawater.     

Electrolytic determination of nanomolar concentrations of silver in solution with a piezoelectric quartz crystal

Silver in solution is determined in situ by the frequency change of a piezoelectric quartz crystal on electrodeposition on the electrode of the crystal. The electrolyte solution flows through a cell containing the platinum-plated electrode (cathode) of the quartz crystal, a coiled platinum-wire anode and a silver—silver(I) chloride reference electrode, and is electrolyzed at —0.2 V vs. $\text{Ag}\text{AgCl}$. The frequency change is proportional to the silver concentration in the range 10^-5–5 × 10^-7 M after electrodeposition for 5 min, and in the range 10^-8–10^-9 M by recycling 20 ml of the solution over the electrodes for 3 h.     

常温下从离子液体电解液中电沉积金属钴

研究了离子液体镀液中Co、Zn的共沉积行为。ZnCl2-EMIC -CoCl2电解液的循环伏安曲线上出现了三个电流峰,对应的电极电位分别为250mV、50mV、-200mV（vs. Zn2+/Zn）。结合EDS成分分析,可断定这三个电流峰分别对应着Co的电沉积、Co电极上Zn的欠电位沉积和Co-Zn合金的电沉积。恒电位沉积表明,当控制阴极电位在100 mV（vs. Zn2+/Zn）左右时,可得到高纯度的钴镀层;若进行恒电流沉积,则当电流密度为85mA/cm2左右时能够得到高纯度的钴镀层。对Co、Zn的共沉积机理研究表明,Co的电沉积过程和Zn 在Co上的欠电位沉积过程均受扩散过程控制。     

Preparation of thin arsenic and radioarsenic targets for neutron capture studies

A simple method for the electrodeposition of elemental arsenic (As) on a metal backing from aqueous solutions has been developed. The method was successfully applied to stable As (⁷⁵As). Thin (2.5 mg cm⁻²) coherent, smooth layers of the metalloid on Ti foils (2.5 μm thickness) were obtained. Electrodeposits served as targets for ⁷⁵As(n,γ) ⁷⁶As neutron capture experiments at Los Alamos Neutron Science Center (LANSCE). Respective ⁷³As(n,γ) ⁷⁴As experiments are planned for the near future, and ⁷³As targets will be prepared in a similar fashion utilizing the new electrodeposition method. The preparation of an ⁷³As (half-life 80.3 days) plating bath solution from proton irradiated germanium has been demonstrated. Germanium target irradiation was performed at the Los Alamos Isotope Production Facility (IPF).