Papers by Keyword: Electrochemical Impedance Spectroscopy (EIS)

Abstract: Nanocomposite coatings were obtained by aggregation of nanoparticles from dispersion in decane on the surface of oxide coatings. Oxide coatings on magnesium alloy were formed by plasma electrolytic oxidation in silicate containing electrolyte in bipolar mode. Electrochemical properties and stability of nanocomposite coatings under conditions of prolonged exposure to chloride containing environment were studied by means of electrochemical impedance spectroscopy, potentiodynamic polarization and measurements of contact angles. The coatings possess superhydrophobic properties with the contact angle of 166o ± 3o and the rolling angle of 5o ± 3o. It was found that these nanocomposite coatings reduce the corrosion current of magnesium alloy by more than three orders of magnitude. High stability during immersion in aggressive media is due to a small contact area of the coatings with electrolyte and high adhesion of the hydrophobic agent molecules with the coating.

Abstract: The effects of shape and duration of the current pulses on the physico-chemical properties of the oxide layers on titanium formed by plasma electrolytic oxidation were examined. It was shown that in the investigated conditions transistor power source possess an advantage in comparison with thyristor one. Electrochemical properties of the heterooxide structures were examined by electrochemical impedance spectroscopy and potentiodynamic polarization methods.

Abstract: The present paper describes the modeling of the energy-storage unit - a battery that consists of several lithium-ion cells. Identification by means of frequency measurements at different operating points and subsequent verification in the time domain serve to identify both the modeling structure and the system parameters. For the frequency measurement the Electrochemical Impedance Spectroscopy (EIS) is used. The iterative character of the selected procedure is exemplified. On the basis of dynamical testing cycles, the accuracy of the battery model is verified even in case of high frequencies.

Abstract: The purpose of this paper is to investigate the electrophoretic deposited nanosilica on stainless steel for corrosion protection. The electrophoretic deposition (EPD) was carried out by pulsed direct current (PDC) of silica sol made of sodium silicate. The amplitude and frequency of the PDC were varied in the range of 0.1-0.6 V and 30-80 Hz, respectively. The corrosion protection properties of the silica films were analyzed by Electrochemical Impedance Spectroscopy (EIS) in 2 wt% NaCl solution. The experimental results showed that the silica films exhibit good characteristics as indicated by their high pore resistance and low admittance. The silica film corrosion protection characteristics were influenced by the frequency and amplitude of PDC during preparation of electrophoretic deposition.

Abstract: In this study, we compared two types of nanostructured electrodes with gold nanocolumns and flat gold electrodes by measurements with doxorubicin. Nanostructured electrodes were fabricated by electrochemical anodic oxidation followed by deposition of gold to the porous alumina. Flat gold electrodes were fabricated by physical evaporation of gold layer to the silicon substrate. All electrodes were characterized by electrochemical impedance spectroscopy and then the electrochemical determination of doxorubicin was studied by differential pulse voltammetry. The impedance spectroscopy measurements proved a bigger electroactive area for nanostructured electrodes. The gold nanocolumns have been found as an important factor in increasing of electrodes active area. This fact is very important for sensors sensitivity. Fabricated electrodes were successfully used for determination of doxorubicin.

Abstract: The inhibition behavior of a new type of mercury-free composite inhibitors for zinc corrosion in zinc-manganese dry battery was studied by single factor test and orthogonal experiment. Its inhibitor mechanism was investigated by Tafel polarization curve, electrochemical impedance spectroscopy (EIS) techniques. The performances of the coated paper and self-assembled battery were detected. The results showed that: the inhibition efficiency of the composite substituting mercury corrosion inhibitors was up to 93.33%. The performances of the coated paper and battery were consistent with standards. The composite corrosion inhibitors are a green environment- friendly corrosion inhibitor, which is expected to replace mercury in zinc-manganese dry batteries.

Abstract: Development of Novel Bio-degradable Electrolyte Based on Polylactide (pla) for Lithium Rechargeable Batteryarmfu� h
� r�rment, degradable polymer which is Polylactide (PLA) was chosen as the host material in the electrolyte. PLA alone had low ionic conductivity which cannot satisfy the current electrical appliance usage. Therefore, PLA is complexed with Ethylene Carbonate, Lithium perchlorate and Aluminum Oxide using THF as a wetting agent. The ionic conductivity of the electrolyte is tested with a.c impedance spectroscopy to determine its ionic conductivity. The highest ionic conductivity of pure PLA is 3.624 x 10^-12 Scm^-1. The PLA is mixed with Ethylene Carbonate to increase its amorphous nature. The result showed that PLA when mixed with 35% of EC give the highest conductivity which is 1.90 x 10^-10 Scm^-1. While the PLA mixed with 20% of Lithium perchlorate give an optimum ionic conductivity which is 5.72 x 10^-7 Scm^-1. Later, the ionic conductivity of PLA, EC and lithium salt mixture were carried out and shows the highest conductivity of 1.44 x 10^-6 Scm^-1. Lastly, with the addition of 4% aluminum oxide filler, the highest conductivity is boosted to 2.07 x 10^-5 Scm^-1. The samples were then analyzed using scanning electron microscope (SEM) to better understand the microstructure of the polymer system.

Abstract: The maturity behavior of cement mortar specimens with different concrete additives during the 28 day curing period has been examined using the AC Impedance technique. The main focus of this part of the study is to understand the impedance and capacitance behavior of the steel rebar in cement mortar using different additives during the early stages of hydration process. In this respect, two sets of specimens were prepared: One set consist of two graphite electrodes surrounded by a carbon steel rod for AC Impedance measurements. Another set consisted of two carbon steel setup that has been used for monitoring corrosion of two steel reinforcement bars embedded in cylindrical mortar specimens. The specimens are placed in a salt fog (spray) cabinet for 1,000 hrs.Galvanic current between the two coupled electrodes has been measured using zero resistance ammeter (ZRA) to monitor the extent of corrosion. The in-situ measurement was carried out in a sequential manner over a periodical basis of up to 1,000 hrs of salt fog cabinet exposure. Different mortar mixes were studied including ground granulated blast furnace slag (GGBS) and silica fume (microsilica) as additives and calcium nitrite as corrosion inhibitor and chloride as a contamination species. This data helps in understanding the corrosion activities at the rebar-concrete when interface combined with salt fog test according to (ASTM B117), which can be further correlated with the atmospheric and marine corrosion of steel rebars in concrete. The overall results have indicated the tendency of the admixture to show different hydration processes during the early stages of concrete curing. The interfacial impedance spectrums and galvanic current testing clearly identifies and documents this process for each material.

Abstract: It is important to generate aluminum oxide layer on the surface of aluminum in order to enhance the adhesion of the dye molecules in coloring aluminum industry. One of the major advantages of aluminum is the formation of a resistant oxide layer naturally, but the thickness of this layer is not high enough and it should be damaged due to lack of mechanical strength. However, the thickness of oxide layer can be increased through anodizing; this process improves its abrasion and corrosion resistance as well as its mechanical properties. In the present study, specimens of pure aluminum were anodized under galvanostatic condition in sulfuric acid electrolyte and porous nanostructured aluminum oxide layer was formed. Porosity of the anodized layer was controlled by optimizing the working conditions such as electrolyte concentration, anodizing time and current density. Finally, the specimens were electrolytically colored by applying alternating current to copper (Cu) solutions. Colored coatings were created at constant voltage and different coloring duration. The results indicated that the shade of different metal ions can be optimized by controlling the coloring parameters, the longer time of coloring results in the darker colors. The samples were examined by X-Ray Diffraction (XRD) spectroscopy and Scanning Electron Microscopy (SEM) and electrochemical test.

Abstract: It is well known that the nanoporous aluminum oxide film is an electrical insulator. In addition the homogeneity of electrodeposited nanowire arrays in nanoporous alumina templates increases drastically with the usage of AC electrodeposition in comparison to DC electrodeposition. This is revealing of the effect of dielectric properties of alumina that is used as template for electrodeposition. In this work integrated nanowire arrays of FePt alloys were successfully fabricated by alternating current electrodeposition on nanoporous alumina; also we characterize the nanoporous alumina membrane that is used as a template for FePt nanowire electrodeposition using EIS allowing the electrochemical impedance contributions from the barrier layer, nanoporous structure, and electrolyte solution resistance to be calculated through the use of an equivalent circuit model. The impedance spectra of the porous film prepared under different anodization conditions were measured. The data is attained at open circuit potential over a frequency range between 1 Hz to 100 KHz with an AC potential amplitude of 10 mV. As our result demonstrates the resistance of the bariyer layer decreases with the anodization temperature then the electrochemical process of FePt nanowires at template which fabricated on low anodization temperature will be difficult due to the higher resistance.