Papers by Keyword: Impedance

Abstract: An electrically conducting polyaniline doped with ferricyanic acid was synthesized by oxidative polymerization of the aniline salt of ferrocyanic acid. Composites based on acidic-modified natural vermiculite, phenylenediamine, and polyaniline doped with ferricyanic acid have been fabricated using the method of molecular layering. The composites structures were studied by the method of X-ray diffraction analysis, while their electroconductivity – by means of impedance spectroscopy.

Abstract: This article is about electrochemical analysis system of passive films corrosion properties of the thermal power equipment heating surfaces. It was found that forecasting the low carbon steel corrosion rate in thermal power systems is possible based on the multiple regression equations, which includes the amount of silicon oxide and iron hydroxide phases in the films, the fraction of free area and the active component of impedance of the films in the alkaline electrolyte and mercury. Construction of the regression equation should be carried out with the preliminary classification of data on the quantities of the active component of the film impedance of mercury and an alkaline electrolyte.

Abstract: Possibilities of tin powders obtainment from the choline chloride-ethylene glycol ionic liquid are considered. The tin reduction from an ionic liquid mechanism is confirmed via chronovoltametry, chronopotentiometry, transient potential and impedance spectroscopy methods. Said mechanism includes the trichlorostanite complexes reduction at current densities up to 5 mA / cm², recovery from a polyanionic adsorbed layer at current densities of 5-12 mA/cm² and recovery from a mixed layer including polyanions bound and by electrolyte ions at current densities exceeding 12 mA/cm². Tin ions reduction from the mixed coating layer facilitates forming of encapsulated tin powder particles with shape of symmetrical dendrites. Powders obtainment from an ionic liquid allows to reduce the resulting powder dispersion.

Abstract: Barium titanate (BTO) samples were prepared by nanomilling based solid state reaction method. Dielectric behavior of BTO sample has been investigated by temperature dependent impedance spectroscopy. The impedance analysis of BTO samples confirm that hopping of electrons and defects coexisted in sample and contribution of grain and grain boundary to dielectric behavior is discussed. A single semicircular arc obtained by Nyquist plots whose radius decreased with increase in temperature illustrates the prominent role of grains. The activation energy of defects was calculated from Arrhenius plot. These defects may be due to oxygen vacancies and hopping between Ti⁺⁴ to Ti⁺³ ions.

Abstract: A single phase perovskite, Y_xSr_1−xTi_0.6Fe_0.4O_3-δ (x= 0.06-0.09), was fabricated at 1350°C in air by sol-gel method. The effects of Y-and Fe-doping into SrTiO₃ on phase structure, electrical conductivity, ionic conductivity and its impedance behavior were investigated. The optimized Y_0.07Sr_0.93Fe_0.4Ti_0.6O_3-δ sample exhibits an electrical conductivity of 0.135 S·cm^-1 at 800 °C. Y-doping decreases the migration energy for oxygen ions, leading to a significant increase in ionic conductivity. The ionic conductivity of Y_0.09Sr_0.91Ti_0.6Fe_0.4O_3-δ sample varies from 0.0052 S· cm^-1 at 600°C to 0.02 S·cm^-1 at 800°C. Impedance characteristics over a wide frequency range of 0.01Hz-100 KHz reveal that the resistance of ionic conduction is predominantly influenced by grain boundary, the relaxation time of which decreases with increase of Y-doping amount.

Abstract: Recently, many types of constructional steels have been often exposed to severely corrosive environments due to acid rain with increasing environmental contamination. To control corrosion problems, a painting protection method has been widely applied to numerous constructional steels on land as well as offshore. Therefore, development of anti-corrosive paint with good quality of corrosion resistance is very important from an economical perspective. In this study, four types of anti-corrosive paint were coated to test specimens, and then, were immersed in various salt solutions (0.1, 3 and 9% NaCl solution) for 11 days. Corrosion resistance of these samples by effect of osmotic pressure with various salt concentration was investigated with electrochemical methods such as measurement of corrosion potential, impedance and corrosion current density. Corrosion current density of these samples submerged in 0.1% NaCl solution exhibited highest value than those immersed in 3% and 9% NaCl solutions because water, dissolved oxygen and chloride ion etc. is easily to invade towards inner side of coating film due to increasing osmotic pressure compared to 3% and 9% NaCl solutions. However, corrosion current densities of all samples in the case of submerged in 9% NaCl solution exhibited higher values compared to 3% NaCl solution.Thus, a large amount of chloride ion dissolved in 9% NaCl solution plays a more critical role in corrosion behavior of coated steel rather than osmotic pressure. Consequently, the corrosion mechanism between coated steel and bare steel plates is different from each other because of presence of osmotic pressure between salt solution and coating film of coated steel plate. As a result, corrosion resistance of tcoated steel plate may be depend on the osmotic pressure as well as salt concentration

Abstract: The galvanized steel structures may be inevitably corroded rapidly in the case of exposed to corrosive environments for long time, and these corrosive environments has been accelerated with increasing the environmental contamination due to the rapid development of industrial society. However, since the galvanizing method have the various merits compared to surface coating treatment in economical point of view, the galvanized steel have been extensively used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and various industrial fields etc.. Therefore, it has been made an effort to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment etc.. In this study, comparison evaluation on the corrosion resistance of three types of the test specimens, that is, three samples of pure galvanizing, galvalume and chromate treatment were investigated using electrochemical methods in 1% NaOH solution. The samples of chromate treatment and of galvalume exhibited the lowest and highest corrosion current density respectively in 1% NaOH solution. In addition, the sample of chromate treatment revealed the highest impedance at 0.01Hz, which is considered that the oxide film by chromate treatment is deposited on the surface of pure galvanizing sample. After drawing polarization curves, the corroded surface of the pure galvanizing specimen indicated pattern like as localized corrosion, moreover, the large amount of corrosive products was observed on the surface of galvalume sample. However, the smooth pattern nearly similar to general corrosion was observed at the corroded surface of the sample of chromate treatment. Consequently, it is considered that the chromate treatment is an optimum method compared to pure galvanizing and, galvalume treatment to improve corrosion resistance in 1% NaOH solution.

Abstract: A map displaying the reflection loss (RL) properties including the frequency and intensity for Co₂Z barium ferrite composite was developed based on the matching model. In quarter-wavelength matching map, the number and the frequency positions of absorbing peaks presenting in RL curve for Co₂Z barium ferrite composite with a certain thickness could be approximately predicted by quarter-wavelength matching model. From impedance map, the intensity of absorbing peaks in measured RL curves was analyzed. Moreover, the presence of absorbing peak in RL curve could be illustrated and understood physically and clearly using a picture of interference cancellation of two EM waves reflected by the absorber layer interface and a backed metal plate.

Abstract: Measuring instruments used for non-destructive testing of structures thanks to advances in electronics and electrical engineering are still more frequently applied. Among the building materials with which the ability to perform quality control using non-destructive testing methods would be most welcome is indisputably steel reinforced fibre concrete (SFRC). The paper deals with the design of new methods and methodologies that enable determination of the concentration and orientation of steel fibres in steel fibre reinforced concrete. Especially the distribution of steel fibres in concrete is the quintessential aspect of this construction material. Initial results of experiments have demonstrated the applicability of the proposed methods and methodologies and the objective of the article is to introduce it to the scientific community.

Abstract: Corrosion of cobalt-contained metal line is one of critical defects during post-CMP cleaning process. Thus, the understanding of inhibitors is significant to eliminate corrosion. In this paper, we discuss the learning from etching rate and electrochemical measurement for the solutions using multiple corrosion inhibitors. Furthermore, TEM of cobalt pattern wafer and cleaning results are shown to demonstrate cleaning and cobalt compatibility performance.