Papers by Keyword: Electrochemical (EC)

Abstract: Experimental and numerical investigations have been performed on the relationships between coating parameters, residual stresses, micro-cracks and the near surface strength of electrochemically deposited hard chromium coatings. The experimental investigations included: X-ray measurements of residual and externally-applied stresses; crack density measurements using microscopy; and load-bearing measurements using ball-on-plate tests. The numerical investigations in combination with analytical conclusions focused on the influence of different crack lengths and densities on the effective elastic modulus of the chromium coating and the stress-enhancing or shielding effect of micro-crack networks respectively. The results show that the residual stresses and crack networks are influenced by the current density used during deposition. Coatings with high tensile residual stresses have low crack densities. This correlation is associated with stress relaxation by formation of micro-cracks and, to a lesser extent, to a direct reduction in residual stresses due to the deposition process. The load bearing capacity is dominated by the crack density and can be significantly increased by shot-peening-induced compressive residual stresses. Thus, optimization of hard chromium deposition parameters for applications needing high surface strength should predominantly focus on minimizing the crack density.

Abstract: It is hardly possible to obtain rare earth doped CaWO₄ thin films directly through electrochemical techniques. A novel post processing has been proposed to synthesize CaWO₄:Eu³⁺ thin films at room temperature. X-ray diffraction, X-ray photoelectron spectrometry, spectrophotometer were used to characterize their phase, composition and luminescent properties. Results reveal that Eu³⁺-doped CaWO₄ films have a tetragonal phase; the content of Eu in the near surface region is much higher than that of the bulk; under the excitation of 310 nm, a sharp emission peak at 616 nm has been observed for Ca_0.9WO₄:Eu_0.1³⁺ thin films.

Abstract: Lead selenide (PbSe) is quite an important semiconductor material with several superior physical properties, e.g. optical and electrical ones. In this paper, PbSe nanocrystals (NCs) with different morphologies such as sphere, rod and hexagon were successfully prepared by an ultrasonic electrochemical method, using sodium citrate as the coordination agent, at room temperature. The crystal structure and the morphology of the as-prepared PbSe NCs were confirmed by means of the Transmission Electron Microscopy (TEM) and X-ray diffractometer (XRD). The ultraviolet-visible Spectrophotometer (UV) was performed to analyze the optical properties of the PbSe NCs. Results show that the nanospheres were about 60 nm in diameter, and the nanorods were 20 nm in diameter with a slenderness ratio of 25. The possible mechanism for the nanorods growth was discussed. The energy gap of the PbSe NCs deduced from the UV-visible spectra was much larger than their bulk counterparts, due to the quantum size effect.

Abstract: This research is to study the effect of deteriorated level on the ions migration in inhibiting the concrete damaged by ASR using electrochemical technique. Cylindrical concrete specimens made by reactive sandstone with 10 cm diameter and 5 cm height were prepared at the ages of 7, 14, 28, 90, and 180 days curing in a 38°C and 100% R.H. storage environment. The accelerated lithium migration technique (ALMT) was performed using LiOH H2O and Ca(OH)2 as electrolytes for anode and cathode, respectively. 9 A/m2 current density was used to drive lithium ion into and remove sodium ion out of the concrete. The results show that the rates of ions migration increase with increasing the deteriorated level of specimen. Furthermore, a linear relationship exists between the non-steady state migration coefficient of Li+ and the deteriorated level of specimen.

Abstract: Steel including sulfide inclusion was used as cathode, while high density graphite rod was used as anode. Sulfide inclusion in steel surface was removed by molten salt electrolysis in molten CaCl2 at 850 under the stationary voltage. The influences of the voltage and electrolytic time on the process of reaction were investigated. The distributions of the sulfide inclusion were investigated by SEM. The desulfurated ratio was investigated by quantitative metallographic analysis, Cyclic voltammetry was performed to characterize reactions of cathode. The results show that the voltage and the time of electrolysis were in direct proportion with desulfurated ratio. The higher voltage and the longer electrolysis time is, the greater the desulfurated ratio is.

Abstract: A novel conducting copolymer, was successfully achieved by electrochemical oxidation of the monomer mixtures of 3, 4-ethylenedioxythiophene (EDOT) and triphenylene (TP) in the acetonitrile solvent system containing 0.1 mol/L LiClO4. The resulting copolymer possesses the advantages of both polytriphenylene and poly(3, 4-ethylenedioxythiophene), such as good redox activity, considerable fluorescence property and relatively high electrical conductivity. Ultraviolet-visible, FT-IR and scanning electron microscopy were used to characterize and investigate the structure of the copolymers. Fluorescence spectra revealed that the copolymer dissolved in common organic solvents was a good blue light emitter, with a strong emission at 439 nm. All these results indicate that the copolymer films as obtained have many potential applications in various fields, such as organic light-emitting diodes (OLEDs).

Abstract: SDBS modified graphene was prepared by electrochemical method using Sodium dodecylbenzenesulfonate (SDBS) as electrolyte and graphite rod as electrode. The anode graphite rod was corroded and deposited at the bottom of the electrolyte solution. The obtained graphene was characterized by Atomic force microscopy (AFM), Raman and Fourier transform infrared spectra (FT-IR). AFM images indicated that most of the layers had the thickness of less than 2 nm, suggesting the fromation of single layer of graphene. The resulting graphene showed very good dispersion stability both in water and in organic solvents (ethanol, acetone).

Abstract: La1-xMgxNi2.8Co0.7 (x=0.1, 0.3, 0.5) hydrogen storage alloy was synthesized by solid diffusion method. The microstructure of the alloy was analyzed by XRD when the content of Mg was changed. When x equaled to 0.3, there was relative much La2Ni7 phase in the alloy and the alloy exhibited better integrated electrochemical performance. Its maximum discharge capacity reached 355.4mAh/g and capacity retention after 50 cycles（S50）was 77.80%. The results showed the existence of La2Ni7 phase would be conductive to the integrated electrochemical performance of the alloy.

Abstract: Organic wastewater pollution control was one of the focus researches for environmental workers. In this study, high active electrode was made and hydrogen peroxide production via cathodic reduction of oxygen was studied, the H2O2 generated in the optimization of research and the effect of dye wastewater degradation under the typical conditions were explored. The effects of mass ratio between graphite and PTFE, Na2SO4 concentration, cathodic potential, pH and gas flow rate on hydrogen peroxide output were investigated. The optimized operational parameters were as follows: graphite and PTFE 5:1, pH=6, Na2SO4 concentration 0.5 mol/L, oxygen flow rate 450mL/min, and cathodic potential -1.2 V (vs SCE). Hydrogen peroxide concentration could reach 66.17 mg/L after 2h at optimized condition. Meanwhile, dye removal could reach about 70% at the same time. Therefore, the use of active electrode as cathode has shown promising prospect in dye wastewater treatment.

Abstract: Monodispersed gold nanocubes of highly uniform size were fabricated by a simple electrochemical method. The lengths of the edges of the gold nanocubes were about 30 nm. The growth solution was prepared from two cationic surfactant solutions as micelle templates with added acetone solvent. The primary surfactant was hexadecyltrimethylammonium bromide (CTAB) and the co-surfactant was tetradodecylammonium bromide (TTAB).