Papers by Keyword: Electrochemical Impedance Spectroscopy (EIS)

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Authors: Gaur Swati, Anand Sawroop Khanna, Raghuvir Kumar Singh Raman
Abstract: In the present study, combinations of a phosphonato silane with a precursor, Methyltriethoxy silane (MTEOS) in various ratios were applied onto the alloy Mg-6Zn-Ca. The corrosion resistance of the coated and uncoated specimens in a modified simulated body fluid (m-SBF) was characterized by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results suggest that the silane coating significantly decreases the degradation rate of the magnesium alloy, indicating its potential to be used as a corrosion barrier for magnesium alloy temporary implants.
Authors: Elida B. Castro, Jorge R. Vilche, C.L.F. Oliveira
Authors: Ting Deng, Zhong Cao, Guo Li Shen
Abstract: An electrochemical impedance biosensor was proposed for the detection of small molecule biotin based on the plasma-polymerized films (PPF) and the bioaffinity difference between an analyte (biotin) and an analogue compound (HABA) in binding avidin. Avidin formed a metastable complex with 2-[(4-hydroxyphenyl)azo]benzoic acid (HABA) immobilized on the electrode surface. When the sensor contacts a sample solution containing biotin, the avidin was released from the sensor surface to form a more stable complex with biotin in solution. The impedance spectra change recorded is proportional to the desorbed mass of avidin, and there is a clear mathematic relationship between the impedance change and the biotin concentration. The proposed electrochemical impedance bioaffinity sensor has nice response to biotin in the range of 4.8×10-9–5.6×10-4 M. The sensor could be regenerated under very mild conditions simply by reimmersion of the sensor into a biotin solution to desorb the surplus avidin.
Authors: An Tao Xu, Bing Luo, Fan Zhang, Fu Jin, Yang Yang Liu
Abstract: By adopting coating damage simulation research method with open circuit potential and electrochemical impedance spectroscopy, the influence of different damage levels of green organic composite coating to its protective performance has been studied. The research found that the variation of open circuit potential partly reflected the damage level of the coating. When K is less than or equal to 0.04, the coating still has favorable protective performance, while K is higher than 16, the protective performance of the coating is basically unavailable, but when K falls in between, the protective performance of the coating is fair good.
Authors: Adel M. Husain, Suad Khalid Al-Bahar, Safaa M. Abdul Salam
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.
Authors: Wei Bo Huang, Jing Zhang, Xin Mao Li, Ping Lu
Abstract: - Electrochemical impedance spectroscopy (EIS) was used to study the thickness and curing temperature influence on the aging behavior of polyaspartic ester (PAE) polyurea under salt fog exposure in this paper. The result has demonstrated that coating thickness and curing temperature had great influence on aging behavior of the PAE-t-HDI prepolymer-D2000H65 aliphatic polyurea (T3). The low frequency impedance after 1day exposure increased from 5.31×1010Ω·cm to 7.96×1010Ω while coating thickness was increased from 40μm to 200μm, and the low frequency impedance of 200μm coating was 7.42×1010Ω·cm2 high after 200 days exposure. The low frequency impedance after 1day and 200 days exposure increased by 0.83×1010 Ω·cm2 and 0.39×109Ω·cm2 respectively, while curing temperature were increased from 60°C to 80°C. Suggestions have been made, namely that increase the coating thickness and curing temperature can improve low frequency impedance of PAE polyurea, as a result, improve the protective properties of the coatings.
Authors: Yi Liu, Shi Cheng Wei, Yu Jiang Wang, Bin Shi Xu
Abstract: The corrosion behavior of Al-RE coating in copper accelerated acetic acid salt spray test (CASS) was studied by electrochemical impedance spectroscopy (EIS). Typical EIS spectral changes were clearly observed during the CASS process. The EIS was shown to be a very useful tool for studying corrosion resistance mechanism. Scanning electron microscope and X-ray energy dispersive spectroscopy were used to analyze the microstructure of Al-RE coatings before and after CASS test. The results revealed that the corrosion behavior of Al-RE coating could be divided into two different stages. In the first stage of CASS, there were two capacitive impedance semicircles in the complex plane plots. The high frequency semicircle responded to barrier layer, the low frequency semicircle responded to the electrochemical reaction of Al-RE coating. In the second stage of CASS, porous layer began to influence the electrochemical behavior.
Authors: Lu Zheng, Liang Bin Liu, Xiao Jing Zhou, Yu Zhong Guo
Abstract: Li (Ni1/3Co1/3Mn1/3) O2 cathode materials doped by Zn were synthesized by a co-precipitation routine, the first delithiation process of the samples with 0-4wt% of Zn doping were studied by electrochemical impedance spectroscopy (EIS) under the polarized voltage of 2.8-4.6V. The fitting results based on EIS data indicate that delithiation reactions happen within the voltage range of 3.7-4.4V ; The resistances of SEI film and charge transfer are both decreased significantly, whereas Li+ diffusion ability through layered crystalline lattice is improved largely with the increase of zinc doping from 0 to 4wt%.
Authors: M.C. Isa, Abdul Razak Daud, M.Y. Ahmad, M. Daud, S.R. Shamsudin, N. Hassanuddin, M.S. Din Yati, M.M. Muhammad
Abstract: In this paper, a study on the electrochemical behaviour and electrical properties of Al-Zn and Al-Zn-Sn alloys in tropical seawater using open circuit potential (OCP) measurement and electrochemical impedance spectroscopy (EIS) are reported. The results from both the OCP and EIS tests show that surface activation was observed in the Al-Zn alloy with the addition of 1.34 wt.% Sn which can be manifested by the shift of OCP values towards more electronegative direction. The EIS spectra of Al-Zn alloy exhibits a semicircle loop, while the EIS spectra for the Al-Zn-Sn alloy exhibits a semicircle with a semicircle inductive loop. The change in EIS spectra for Al-Zn-Sn alloy is correlated to the increase of surface activation resulting in a less stable passive layer. Equivalent circuits models were proposed to fit the impedance spectra and the corresponding electrical parameters with optimum values were deduced. The modulus impedance in the low frequency region or polarization resistance, Rpol obtained for the Al-Zn-Sn alloy, Rpol = 2.76 kΩ cm2) is slightly decreased compared to the corresponding value of the Al-Zn alloy, Rpol = 3.97 kΩ cm2), indicating a considerable reduction in the protective capability of the oxide layer on the Al-Zn-Sn alloy. It appears that the heterogeneous oxide film and pores formed on the Al-Zn-Sn alloy play a key role in reducing total resistance to the flow of electron at the alloy-electrolyte interface.
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