Composition control of ternary FeCoNi deposits using cyclic voltammetry

Ternary FeCoNi alloys were electroplated through mean of cyclic voltammetry in simple chloride baths with pH of 2.0. The anodic process in the voltammetric curves was found to completely depress the anomalous deposition of binary alloys while this anomaly was still obvious for the deposition of ternary FeCoNi alloys. From the energy-dispersive X-ray results, the Fe/Co ratio in the ternary FeCoNi deposits was equal to the Fe²⁺/Co²⁺ ratio in the deposition solutions when the Ni²⁺ content was continuously changed. The composition of ternary FeCoNi deposits could be precisely predicted and easily controlled by adjusting the Ni²⁺/(Fe²⁺+Ni²⁺+Co²⁺) ratio in the plating solutions although a synergistic effect in depressing the codeposition of Ni onto the FeCoNi matrix due to the coexistence of Co²⁺ and Fe²⁺ was clearly demonstrated in this work.     

Application of elimination voltammetry in the study of electroplating processes on the graphite electrode

The electrode reaction mechanism of electrolytical coating by nickel on paraffin impregnated graphite electrode (PIGE) was investigated by cyclic voltammetry (CV) and elimination voltammetry with linear scan (EVLS). The EVLS, a relatively new method of processing electrochemical signals obtained by voltammetry, is able to eliminate some individual chosen currents from total voltammetric currents measured at different scan rates. During the electrodeposition of metals on the graphite electrode, hydrogen evolved from aqueous acidic solutions interferes with the plating process. The elimination of kinetic current arising due to hydrogen evolution enables one to study other processes proceeding at the electrode. Cyclic voltammograms for metal coating deposition/dissolution on the graphite electrode were measured at three scan rates (12.5, 25 and 50 mV/s) and the EVLS functions were calculated for one or two eliminated currents. The results indicate the occurrence of surface reactions with the adsorption of intermediates on graphite. The application of EVLS provides deeper insight into the mechanism of electrode reaction during metal deposition.     

Study of the electrochemical deposition of Sn-Ag-Cu alloy by cyclic voltammetry and chronoamperometry

The electrochemical deposition of Sn-Ag-Cu alloy from weakly acidic baths onto glassy carbon electrodes (GCE) was studied by cyclic voltammetry (CV) and chronoamperometry (CA). The properties of the electrodeposits were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometery (EDS) and X-ray diffraction (XRD). Test results indicate that the two cathodic peaks in the CV curves, at −0.6 V and −0.85 V during the forward scan towards the negative potentials, correspond to the irreversible deposition of a solid solution of tin, silver and copper. The underpotential deposition (UPD) of Sn occurs at −0.6 V during the cathodic period and the amount of Ag and Cu in the Sn-Ag-Cu alloy decreases with increasingly negative cathodic potentials. During the forward scan, towards the positive potentials used in CV testing, cathodic peaks at −0.85 V appear in the CV curves for baths containing mixtures of tin salts and triethanolamine (TEA). This corresponds to a reduction of transient complex ions [Sn(TEA)_x]²⁺ on the surface of the cathode. Furthermore, the formation and reduction of [Sn(TEA)_x]²⁺ is a diffusion controlled process. On the surface of the GCE, the actual nucleus growth mechanism of the Sn-Ag-Cu alloy is represented by the progressive nucleation model.     

Effects of substrate roughness on the orientation of cylindrical domains in thin films of a polystyrene-poly(methylmethacrylate) diblock copolymer studied using atomic force microscopy and cyclic voltammetry

This paper describes the orientation of cylindrical domains in thin films of a polystyrene-poly(methylmethacrylate) diblock copolymer (PS-b-PMMA; 0.3 as the PMMA volume fraction) on gold and oxide-coated Si substrates having different surface roughness. Atomic force microscopy images of PS-b-PMMA films having thickness similar to the domain periodicity permitted us to study the effects of substrate roughness and block affinity on domain orientation. PS-b-PMMA films on gold substrates showed metastable vertical domain orientation that was attained more slowly on rougher substrates. In contrast, the domains were horizontally oriented on oxide-coated Si regardless of surface roughness and the annealing conditions examined. In addition, cyclic voltammetry data for PS-b-PMMA films on gold substrates whose PMMA domains were etched suggested that the metastable vertically oriented domains reached the underlying substrates. These results indicate that PS-b-PMMA films containing vertically oriented cylindrical domains can be obtained by using rough gold substrates upon annealing under controlled conditions.     

Comparison between cyclic voltammetry and chronoamperometry when coupled with EQCM for the study of the SEI on a carbon film electrode

Cyclic voltammetry (CV) and chronoamperometry have been conducted with the electrochemical quartz crystal microbalance (EQCM) to characterize electron-beam deposited carbon film electrodes in LiClO₄-containing mixed electrolytes of ethylene carbonate (EC) and dimethyl carbonate (DMC). For a system whose electrolyte viscosity changes in the course of experiments, such as the above combination of electrode and electrolyte, the mass change per mole of electrons transferred (MPE) of the species on quartz crystals depends on the potential scan rate of CV. Chronoamperometry with a short period is more desirable for the estimation of the MPE of the solid electrolyte interphase (SEI) because the viscosity-induced frequency change, which hinders the correct MPE estimation, constitutes a small portion of the measured frequency change under this experimental condition.     

Study on the influence of anionic and cationic surfactant on Au-colloid modified electrode function by cyclic voltammetry and electrochemical impedance techniques

The influence of different surfactants on Au-colloid modified electrode function has been investigated by using cyclic voltammetry and electrochemical impedance techniques. Colloidal Au was self-assembled onto the gold electrode through the thiol-groups of 1,6-hexanedithiol (HDT) monolayer. It was found that some HDT molecules stood on the gold electrode and some molecules lay on the electrode by using the quartz crystal microbalance (QCM). A cathodic peak at about 0.486 V (vs. SCE) was observed at the bare gold electrode and the Au-colloid modified electrode. Cyclic voltammetry was used to investigate the influence of different surfactants on the cathodic peak of Au-colloid modified electrode. Electrochemical impedance technique was also used to study the electron transfer ability of the redox probe on Au-colloid modified electrode after being immersed in different surfactants. The results showed that anionic surfactant and cationic surfactant exhibit different behaviors, the reason of which was discussed.     

On the use of cyclic voltammetry for the screening of oxide catalysts for NO decomposition and reduction

It has been claimed [J. Zhu, D. Xiao, J. Li, X. Yang, Y. Wu, Electrochem. Commun. 7 (2005) 58] that cyclic voltammetry of perovskite-like oxides in a LiClO₄/propylene carbonate electrolyte is a strong tool for selecting those oxides more active for NO decomposition and reduction. This claim is fundamentally wrong, since it is based on: (1) a travesty of Nernst's equation, in which the peak separation in a cyclic voltammogram, a purely kinetic parameter, is substituted for the thermodynamic equilibrium potential (2) a wrong claim that the electron transfer between a transition metal cation in an oxide and a neighbouring oxygen vacancy, a process that occurs within the oxide, without any electron transfer through the electrode-electrolyte interface, is responsible for the voltammetric peaks of lithium insertion/deinsertion observed in cyclic voltammetry (unexplainably, lithium insertion/deinsertion is not mentioned at all in the article) (3) an unproven relationship between the charge of the voltammetric peaks of lithium insertion/deinsertion and the concentration of oxygen vacancies in the oxide (4) an unproven correlation between the reversibility of the lithium insertion/deinsertion process at room temperature and the catalytic process of NO decomposition at 850 °C. Therefore, at present cyclic voltammetry has not been shown to be a useful tool for the screening of catalysts for NO decomposition and reduction.     

Poly(dihexadecyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene) film formation by cyclic voltammetry: dependence of the optical properties and morphology on the thickness

The voltammetric, morphologic and spectral properties of poly(dihexadecyl-4H-cyclopenta[2,1-b:3.4-b′]dithiophene), synthesised on ITO electrode in acetonitrile/dichloromethane mixed solvent by cyclic voltammetry, strongly depend on the film thickness. The polymerisation occurs through two successive steps: the electrode covering and a further growing of the film on the polymer coated electrode. The rate of the film growing is higher in acetonitrile-rich solvent and is a linear function of the monomer concentration during both the electrode covering and the subsequent growing step.     

Effects of polyethylene glycol and gelatin on the crystal size, morphology, and Sn-sensing ability of bismuth deposits

The influences of citric acid (CA), ethylenediaminetetraacetic acid (EDTA), polyethylene glycol (PEG), and gelatin on the deposition behavior of Bi were systematically investigated through the linear sweep voltammetric (LSV) analysis. Based on the LSV results, deposits plated from a typical solution containing 0.05 M Bi(NO₃)₃·5H₂O and various combinations of complex agents and additives with pH = 3.5 at 1 and 30 mA cm⁻² were characterized by scanning electron microscopic (SEM) and X-ray diffraction (XRD) analyses. The adhesion of deposits and the formation of dendrites were respectively improved and inhibited by the adsorption of PEG onto Bi deposits. With adding the above four compounds, a synergistic effect was shown to reach a nano-sized, sphere-like, porous morphology of a Bi deposit at 30 mA cm⁻². The crystal size and morphology of Bi deposits were found to affect the sensing ability of Sn²⁺ through the square-wave anodic stripping voltammetric (SWASV) analysis.     

Effects of viscosity ratio and composition on development of morphology in chaotic mixing of polymers

This study investigated the effects of viscosity ratio (p) and composition on morphology development in an immiscible polymer system mixed under chaotic flow conditions. It was seen that morphology of the dispersed phase developed through a widely accepted route involving transitions from lamellas to fibrils and to droplets. It was found in experiments with p≥1 that the dispersed phase converted into droplets very rapidly with narrow droplet size distribution when p∼1. For higher values of p, the speed of morphological transitions slowed down, the droplet size distribution became wider, and much larger droplets were formed. Similar effects were observed at higher concentration of the dispersed phase. No self-similar scaling behavior was observed in the droplet size distribution, which can be attributed to the lack of self-similarity in the breakup of lamellas into fibrils.     

Effects of morphology and composition on catalytic performance of double metal cyanide complex catalyst

Double metal cyanide (DMC) complexes based on Zn₃[Co(CN)₆]₂ were prepared using different zinc salts and complexing agents and They were characterized by elemental analysis, IR and XRD. The catalytic properties of DMC complexes were determined in polymerization of propylene oxide. Great differences in morphology of DMC complexes was were correlated with preparation route as well as with the kind of zinc salts employed. The catalytic activity was strongly dependent on the morphology of DMC complexes and composition of catalysts. The study revealed that the amorphous catalyst made from ZnCl₂ and t-BuOH had the highest activity (up to 26 kg polymer/g catalyst). The DMC catalyst was non-stoichiometric. Polymerization of propylene oxide (PO) catalyzed by DMC proceeded in a controlled manner. The molecular weight of each polymer was controlled by the monomer/initiator ratio, the values of molecular weight distribution (MWD) were in the range of 1.23–1.48. The polymer has an atactic structure and a head-to-tail regiosequance.     

Electrodeposition and morphology of Ni, Co and Ni-Co alloy powders: Part II. Ammonium chloride supporting electrolyte

Polarization characteristics of the processes of Ni and Co powders and Ni-Co alloy powders electrodeposition from ammonium chloride containing supporting electrolyte and their morphologies are investigated as a function of Ni²⁺ and Co²⁺ ions concentrations. It is found that the shape of the polarization curves in all cases is practically defined by the shape of the polarization curve for hydrogen evolution. It is shown that correct polarization curves, as well as the morphology of electrodeposited powders are sensitive to the ratio of Ni²⁺/Co²⁺ ions concentration. Characteristic feature of powder particles obtained from chloride containing electrolytes is the presence of cone-shaped cavities. In the case of Ni powder cauliflower and spongy type particles are detected, while Co powder contains only spongy type particles. In all cases of alloy powder formation anomalous type of co-deposition is detected.     

On the role of NO2 ions in passivity breakdown of Zn in deaerated neutral sodium nitrite solutions and the effect of some inorganic inhibitors: Potentiodynamic polarization, cyclic voltammetry, SEM and EDX studies

As a first step towards studying pitting corrosion of Zn in deaerated neutral sodium nitrite solutions (pH 6.9), we have reported the results of potentiodynamic polarization and cyclic voltammetry measurements on the passivity and passivity breakdown of Zn in these solutions. Measurements were conducted under the influence of various experimental conditions, complemented by ex situ scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) examinations of the electrode surface. The voltammograms involve active/passive transition prior to the initiation of pitting corrosion as a result of breakdown of the passive film by NO₂⁻ ions. The active region displays one anodic peak due to the formation of ZnO passive film on the anode surface. SEM examinations confirmed the existence of pits on the electrode surface. The potential at which pits initiated (E_pit) was determined, together with a pit transition potential (E_ptp) that appeared as an abrupt current discontinuity on the reverse potential scan (hysteresis loop), and a protection potential (E_prot) that appeared at the end of the hysteresis loop. The value of E_pit shifted negatively as either C_nitrite or temperature was increased, while it increased with the increase in potential scan rate. The effect of adding some environmentally acceptable inorganic inhibitors, as tungstates, molybdates and silicates (water glass), on the pitting corrosion behaviour of Zn in nitrite solutions has also been studied. The mechanism of inhibition was discussed.     

Effect of plating mode, thiourea and chloride on the morphology of copper deposits produced in acidic sulphate solutions

The influence of plating mode, chloride and thiourea (TU) on morphology of copper deposits has been studied. All experiments were conducted on disc electrodes rotating at 500 rpm and an average current density of 4 A dm⁻² to produce 10 μm thick deposits. In additive-free solutions, the use of pulsed current (PC) improved deposit morphology and brightness over DC plating. In the presence of thiourea (no Cl⁻), the deposits obtained by DC and PC plating were similar under most plating conditions. The presence of thiourea generally improved deposit quality over that obtained in additive-free solutions, but caused the formation of microscopic nodules and the deposits to appear slightly cloudy, resulting in lower reflectances than that of a polished uncoated copper surface. The addition of Cl⁻ to thiourea-containing solutions strongly influenced deposit morphology at both microscopic and macroscopic scales depending on chloride concentration and pulse conditions. It prevented nodule formation and created microscopically bright and reflective deposits, but caused extreme macroscopic roughness. Nevertheless, PC plating at 50 Hz in solutions containing appropriate amounts of thiourea and Cl⁻ was found to yield macroscopically and microscopically smooth deposits with reflectance similar to that of a polished uncoated copper substrate.     

Influence of anode material on the electrochemical oxidation of 2-naphthol: Part 1. Cyclic voltammetry and potential step experiments

The anodic oxidation of 2-naphthol has been studied by cyclic voltammetry and chronoamperometry, using a range of electrode materials such as Ti-Ru-Sn ternary oxide, lead dioxide and boron-doped diamond (BDD) anodes. The results show that polymeric films, which cause electrode fouling, are formed during oxidation in the potential region of supporting electrolyte stability. IR spectroscopy verified the formation of this organic film. While the Ti-Ru-Sn ternary oxide surface cannot be reactivated, PbO₂ and BDD can be restored to their initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In fact, during the polarization in this region, complex oxidation reactions leading to the complete incineration of polymeric materials can take place on these electrodes due to electrogenerated hydroxyl radicals. Moreover, it was found that BDD deactivation was less pronounced and its reactivation was faster than that of the other electrodes.     

Effects of the loading and polymerization temperature on the capacitive performance of polyaniline in NaNO3

Polyaniline (PANI) synthesized by a potentiostatic method at 4 °C in 1 M HNO₃ with the polymerization charge density equal to/less than 0.45 C cm⁻² was demonstrated to exhibit ideally capacitive characteristics (i.e. high reversibility and high-power property) with a high specific capacitance of 210 F g⁻¹ for the application of electrochemical supercapacitors in NaNO₃. Influences of the polymerization charge density (i.e. the polymer loading) and the polymerization temperature on the capacitive characteristics of PANI films compared by both cyclic voltammetry and charge-discharge technique were reasonably correlated with their structural properties examined by X-ray photoelectron spectroscopy (XPS). The highest specific capacitance of a PANI film polymerized at 4 °C was attributed to its lowest density of structure defects. The surface morphology of these PANI films was examined by a scanning electron microscope (SEM).     

Influence of blend composition on the mechanical properties and morphology of PC/ASA/SAN ternary blends

Bisphenol A polycarbonate/acrylonitrile–styrene–acrylic/styrene–acrylonitrile copolymer (PC/ASA/SAN) ternary blends were prepared over a range of compositions via mixing PC, SAN, and ASA copolymer by melt blending. An analysis was made on the mechanical properties and morphology of the blends. Special care was taken to make comparisons of the morphologies and properties of blends with different SAN content. When a small amount SAN was introduced to PC/ASA blends, the dispersion condition of ASA in the matrix was improved and a better integrated mechanical properties was realized. Further increasing the SAN content led to a decrease of impact strength, which was due to the changing of the morphology of the blends and the inherent brittleness of matrix. The study about the effect of ASA content on the properties of PC/ASA/SAN blends showed that the blend with 20 wt% ASA had good mechanical properties.     

沉积条件对CVD法SiC涂层形貌和组成成分的影响

采用MTS-H2-Ar体系通过等温化学气相沉积(CVD)在石墨基底表面沉积了SiC涂层。研究了沉积温度、气体总压和气体流量对涂层形貌和组成成分的影响。SEM和AFM观察表明,SiC一次颗粒尺寸在100nm以内。在本实验的沉积条件变化范围内,Ar流量增大使涂层表面变粗糙,温度升高使涂层变厚。X射线衍射和拉曼光谱分析显示沉积物主要为3C型的β-SiC。气体总压和H2流量都增大时易生成游离Si。气体总压较小而H2流量较大时易生成游离C。当气体总压为5kPa,H2流量为500mL·min-1时可得到化学计量比的SiC。     

Effects of composition and reflowing on the corrosion behavior of Sn-Zn deposits in brine media

Tin-zinc deposits with the Zn content varying from 13 to 0 weight percents (wt%) (close to the eutectic point of the Sn-Zn alloy, Sn-9Zn) were electroplated onto iron-coated copper substrates from a near-neutral (pH 5.0), non-cyanide bath. The corrosion parameters, including open-circuit potential-time curves (E_OCP-t), corrosion potentials (E_CORR), and corrosion currents (i_CORR), of this series of materials before and after reflowing in N₂ at 250 °C for 10 min were determined and systemically compared in a brine medium containing 3 wt% NaCl. For the as-prepared deposits, the Sn-5Zn deposit showed an activity very close to but more active than that of Fe in this brine medium. This deposit also exhibited the highest corrosion resistance in the study of electrochemical impedance spectroscopy (EIS). For the reflowed deposits, the anticorrosive ability of Sn-Zn deposits with the Zn content <9 wt% became relatively poorer than that of their corresponding as-prepared counterparts while the Sn-9Zn and Sn-5Zn deposits with reflowing showed the best anticorrosive properties in the 3 wt% NaCl solution. The crystalline information and the surface morphologies of the deposits before and after the reflowing treatment were compared by means of the X-ray diffraction (XRD) and scanning electron microscopic (SEM) analyses.