Papers by Keyword: Impedance Spectroscopy

Abstract: The binary solid electrolyte Li₂WO₄-LiI with incorporation of nanosize Al₂O₃ was prepared in solid state reaction and characterized by Electrical Impedance Spectroscopy (EIS), Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared (FTIR) spectroscopy. Maximum electrical conductivity of 3.35x10^-3 Scm^-1 was recorded for the sample containing 20 wt. % of LiI. Enhancement of electrical conductivity up to 5.8x10^-3Scm^-1 was achieved when 0.5 wt. % of Al₂O₃ was added into the optimum composition of the binary Li₂WO₄-LiI system. Tetrahedral structure of WO₄ that appear at wave number of 906 cm^-1 and 955 cm^-1 in the FTIR spectroscopy confirmed. The existence of conducting pathway for migrations of Li ions in system that contributes to high electrical conductivity.

Abstract: Magnesium is one of the lightest metals and magnesium alloys have quite special properties, interest to which is continuously growing. In particular, their high strength-to-weight ratio makes magnesium alloys attractive for various applications, such as transportation, aerospace industry etc. However, magnesium alloys are still not as popular as aluminum alloys, and a major issue is their corrosion behavior.The present research investigated the influence of the PEO treatment on the corrosion behavior of MRI 230M magnesium alloy. Plasma electrolytic oxidation (PEO) of an MRI 230M alloy was accomplished in a silicate-base electrolyte with KF addition using an AC power source.The corrosion behavior of both treated and untreated samples was evaluated by open circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), linear polarization tests, linear sweep voltammetry (Tafel extrapolation) and chemical methods, such as mass loss and hydrogen evolution, in neutral 3.0 wt% NaCl solution.According to the tests results, PEO process can affect the corrosion resistance of MRI 230M magnesium alloy, though its action is not always unambiguous. An attempt to explain the influence of the PEO treatment on the corrosion behavior of the alloy is presented.

Abstract: Barium titanate with 10% barium ferrite substitution (BaTiO₃-BaFe₁₂O₁₉) has been synthesized by the solid state reaction route. Formation of the BaFe₁₂O₁₉ phase confirmed its existence in the composite. Impedance spectroscopy study of the composite sample was performed at different temperatures of 25, 40, 80, 120 and 160 °C. BaFe₁₂O₁₉ substituted sample shows a single semicircle at lower temperature and two overlapped arcs at 120 and 160 °C due to grain and grain boundary. The impedance plots were fitted based on a parallel R-CPE circuit. The grain boundary resistance behaves like the positive temperature coefficient of resistivity (PTCR) for donor-doped BaTiO₃ semiconductor. The highest capacitance is contributed by the grain boundary at 80 °C.

Abstract: To date gel and film type polymer electrolytes have been widely synthesized due to their wide range of electrical properties. However, these types of polymer electrolytes exhibit poor mechanical stability and poor electrode-electrolyte contact hence deprive the overall performance of a battery system. Therefore, in order to indulge the advantages of polymer as electrolyte, a new class of liquid-type polymer electrolyte was synthesized and investigated. To date this type of polymer electrolytre has not been extensively studied. This is due to the unavailability of liquid polymer for significance application. In this study, liquid poly (methyl methacrylate) (PMMA) electrolyte was synthesized using the simplest free radical polymerization technique using benzoyl peroxide as the initiator. It was found that this liquid PMMA oligomer has potential as electrolyte in proton battery when doped with small volume of various molarity of hydrochloric acid (HCl) in which the highest ionic conductivity achieved was 10^-7 S/cm at room temperature. The properties of this liquid PMMA oligomer were further investigated using Fourier Transform Infrared Spectroscopy (FTIR).

Abstract: A Na–ion conducting solid electrolyte system was prepared by using ball milling and sintering method. The electrical conductivity study was carried out as a function of NaI concentration by Electrical Impedance Spectroscopy technique and the maximum conductivity of (1.02±0.19)×10^-4 S cm⁻¹ at room temperature was obtained for the composition 0.50 NaI:0.50 Na₃PO₄. Further characterization was performed by using and Infrared (FTIR) technique. From FTIR spectra, the variation in the peak intensity and shifting is observed due to the presence of P–O and PO₄³⁻ bands that had been shifted indicating changes in polyhedral structure which in turn led to the formation of conducting channel by corner sharing or through edges. The ionic transference number was found in the value of 0.92 which suggests that ions are the charge carriers. The optimum composition with the highest conductivity of the sample considered as a good candidate to be used as solid electrolyte in solid state sodium battery. The sodium battery with configuration: Na/NaI–Na₃PO₄/V₂O₄ was tested by the discharged characteristic at a current of 1.0 μA. The solid state sodium batteries exhibited a discharge capacity of 144mAh/g.

Abstract: The aim of this study was to obtain 4.5%mol Y₂O₃-doped ZrO₂ dense with submicrometer grain size and studying the effects of using oxygen flow during calcination in the electrical properties of bodies sintered. The powders were synthesized by the Pechini method. After synthesis, the resins were dried and the calcinations were performed in air and in oxygen flow at 600°C for 2 h. The powders were pressed with 1600 MPa and sintered by Two Step Sintering (TSS) at 1500°C / 5 min and 1200°C, 1300oC, 1400°C, remaining at these temperatures for 2 and 10 hours. The sinterized samples were characterized by X-ray diffraction, apparent density, scanning electron microscopy and impedance spectroscopy. The apparent densities were greater than 94% for all conditions of calcination and sintering. The value of the activation energy was 0.7eV for the grain and 0.9 eV for the grain boundaries.

Abstract: Paper deals with the applicability of impedance spectroscopy method to testing of cement-based composites prepared from a mix of type CEM I cement and siliceous sand, as well as by substituting 25 % of sand with shredded automobile tires and by adding acrylic polymer binder (10 % w/w of the polymer mass to cement mass). The monitoring of structural changes in the thermal stress is very important, for example for determining the reliability of the whole structure. Samples were intentionally degraded by high-temperature (in a temperature range from 25 °C to 400 °C). The primary monitored magnitudes were electrical capacitance C, the relative permittivity ε_r and components of electric impedance |Z|. Based on the Debye theory of dielectric the models were created, their applications and received parameters measured dielectric material is characterized and discussed the uniqueness of determining the values of model parameters. Development of electrical parameters and permittivity at each temperature areas reliably show thus structural changes and thus the structural reliability.

Abstract: This paper deals with the application of the method of impedance spectroscopy to testing of cement-based composites prepared from a mix of cement mortar and quartz sand, which were intentionally degraded by high-temperature treatment (in the temperatures range from 25 °C to 400 °C). The monitoring of structural changes in the thermal stress is very important, for example for determining the reliability of the whole structure. Based on the Debye theory of dielectric the models were created, their applications and received parameters measured dielectric material is characterized and discussed the uniqueness of determining the values of model parameters. Development of electrical parameters and permittivity at each temperature areas reliably show these structural changes and thus the structural reliability.

Abstract: It is known that concrete is one of the most popular building materials nowadays. There are many traditional, mainly destructive methods for monitoring its properties during its lifetime. It is clear that its properties depend significantly on the composition of concrete mixture. Concrete lifetime depends mainly on curing during the first 7 days after making the mixture. The paper shows the possibilities of applying Acoustic Emission and Impedance Spectroscopy methods during the early age of concrete.

Abstract: The present paper deals with the application of impedance spectroscopy method to test cement-based composites after their exposure to high temperatures. A type CEM I Portland cement, siliceous sand and shredded automobile tires were used to prepare mortar specimens. The specimens differentiated in whether or not a 10 % w/w acrylic polymer binder (polymer dispersion 20 % w/w to cement mass) addition to the mortar mixture was used. The specimens were exposed to high temperatures (temperature range: 25-400 °C). Monitoring of structural changes during subjection to thermal stress is an effective way to determine the reliability of specimens structure. Based on Debye's dielectric theory, the specimens were used as dielectric models. Impedance spectra were obtained, while relative permittivity, loss factor and impedance were also measured. The results concerning electrical parameters and permittivity at each temperature were an indicator of the structural changes and its reliability.