Papers by Keyword: Electrical Impedance

Abstract: Cement composites such as mortars and concretes with electrically conductive properties, have different uses, such as electromagnetic shielding, electrical grounding, cathodic protection, vehicle traffic monitoring, and the detection of strains and cracks in buildings. However, for these composites to have their electrical conductivity increased, it is necessary to incorporate electrically conductive materials, such as metals and carbon. Nonetheless, such materials tend to be expensive, which makes the manufacture of the composite more expensive. In this sense, using waste materials can help reduce costs and minimize impacts on the environment. Therefore, cement mortars were produced in this research with waste of brake linings from heavy vehicles, which may contain metallic and carbon-based materials. The mortars produced had part of the sand replaced by up to 70% crushed waste, which was submitted for analysis of compressive strength and electrical impedance. Preliminary results showed a decrease in the impedance (showing a trend of increasing electrical conductivity) of mortars with brake lining waste compared to mortars without waste, as well as a decrease in compressive strength. Finally, the use of brake lining waste in the production of cement composites can help reduce the consumption of natural resources as well as minimize the disposal of waste in landfills, which in both cases contributes to the sustainability of the environment.

Abstract: Electric impedance is widely used in imaging and detection techniques. The applications range from non-destructive testing, structural health monitoring, and geophysical imaging to medical imaging. The frequency of the signal used for the measurement ranges from less than 1 Hz to about 1 GHz. This paper addresses the measurement and evaluation of the phase dependent electrical resistance, inductance, capacitance, and impedance of a shape memory alloy (SMA) spring (BMX 150, Toki Corporation). The material characteristics can be obtained by means of their electromechanical impedance. Experimental procedures are implemented and the electrical characteristics are obtained for a wide range of frequency. The electrical resistance, inductance, impedances of the austenite and martensite phase are determined, also the quality factor of the Bio Metal coil to be (9.465 – 9.95) Ω and (10.358 – 10.8) Ω, (0.458 – 0.38) μH and (0.458 – 0.36) μH and, (9.47 – 10.24) Ω and (10.36 – 11.11) Ω respectively for the frequency range of 100 kHz - 1MHz. The quality factor of the Bio Metal ranges between 0.03 and 0.2 during heating and, 0.028 and 0.022 during the cooling phase. The experimental results herein show that an equivalent circuit of the SMA spring is a series resistor-inductor circuit with a parasitic capacitance effect. The electromagnetic behaviour of SMA is determined using a finite element tool.

Abstract: Diffusion welding is being used in aircraft, optic and electrical industry, where special alloys or combinations of metal or non-metal materials are often used. The alloys and materials come from limited sources and therefore they are expensive as well. These reasons lead to the fact that the destructive testing of diffusion bonded joints is not sufficient for the industry and the used components in operation. The paper discusses about the testing methods suitable for the diffusion bonded joints, which are commonly used in our research of diffusion welding and which are planned to be used afterwards.

Abstract: Dye Sensitized Solar Cells (DSSC) technology using inorganic electrolytes post problem in solvent evaporation and iodine sublimation (corroding contacts) causing instability of cells. Application of low molecular oligomers is progressing recently for an improved performance. The electrolyte system was aimed for improving electrochemical stability using quasi-solid-state electrolytes from organic capped polymers. A photo-electrochemical cell was developed from bio-based polyurethane diol (PU) polymer electrolyte with Sodium iodide (NaI) as conducting electrolyte transport material. In this study, polyurethane-diol was modified with NaI cations in the hydrothermal chemical reaction to form modified polyurethane-diol electrolyte. The chemical structure of polyurethane-diol and NaI have achieved highest conductivity of 8.06x10^-5 S.cm^-1 where structural of polyurethane-diol with NaI shown redox Fermi vectorial energy transfer evaluated for performance of efficiency. Stable cell for DSSC system require material properties to be invidually optimized in views of various elemential performances and solar cell of FTO/TiO-Pc/PU-NaI-I₂/Ac give a response under light intensity of 100 mW cm⁻² and indicated efficiency of power generation of 4 mW where photovoltaic effect of current density, Jsc of 0.04 mA.cm⁻² and open circuit voltage, Voc of 0.4 V respectively.

Abstract: The electrical impedance of Y₂NiMnO₆ ceramics sintered at 1400 °C for 6 to 24 hours were investigated. The electrical properties of Y₂NiMnO₆ ceramics were examined in dc bias from 0 volt to 1.5 volt at room temperature. At frequencies below 10⁵ Hz the high electric impedance decreased significantly with longer sintering time, indicating that the grain and grain boundary effects. Increasing dc bias also reduced impedance at the lower frequencies, with polarisation affect at higher frequencies. This behaviour suggests a decrease in the relaxation time of the mobile charge carriers with increasing dc bias and describes a thermally activated relaxation phenomena in the Y₂NiMnO₆ ceramics.

Abstract: Ag/AgCl electrodes as an important sensor are used in modern clinical detection and biomedical measurement, which have been widely applied in electrocardiograph (ECG), electroencephalogram (EEG), electromyography (EMG), electricity impedance technology (EIT) and so on. In this study, the electrode pairs were gel-to-gel connected. After a stimulating current, the alternating current (AC) or the direct current (DC), was injected through the electrode pair, the electrical potential was recorded, then impedance data of Ag/AgCl electrode was obtained. The results showed that the AC impedance of electrode increased, and then gradually decreased with the increase of current size. It was found that the DC impedance data of Ag/AgCl electrode was changed greatly after the electrode pair was injected into the alternating current. With the long time continuous measurement, the AC impedance of electrode pair gradually increased within the 12 hours. However, the significant fluctuations of AC impedance were observed after 12 hours. Comparing with the AC impedance, the DC impedance of electrode pair exhibited a great increase with the increase of measurement time.

Abstract: This paper deals with the effect of power line impedance characteristics on the retained voltage magnitude after a two-phase fault at electric power distribution or transmission networks. Specifically, the effect of resistance-to-reactance (R/X) ratio of power line conductors or cables on voltage magnitude during two-phase faults is studied with analytical mathematical expressions. The basic aim of this investigation is to create a tool for the automatic recognition of the type and the location of faults on electric power networks.

Abstract: The building materials are evaluated for their mechanical behavior, durability and most recently, about the risk of environmental contamination. Some heavy metals can be found in the waste added in cementitious matrices. The techniques of introducing the wastes in cementitious matrices allow the stabilization and solidification of the contaminants. However, this immobilization should be monitored and the effectiveness of this method is investigated by carrying out leaching tests, among other procedures. The objective of this study was to analyze the influence of heavy metals in the hydration process of cementitious matrices by way of tank tests carried out on mortar, previously contaminated with the heavy metals Zn²⁺, Cr³⁺ and Pb²⁺ at a concentrations of 20, 40, 80 and 160 ppm and to propose the use of electrical impedance spectroscopy (EIS) coupled to represents the leaching mechanisms. In the electric test was used an alternating current, varying the frequency of 200 kHz to 2 MHz. For assess the leaching behavior were performed the tank test (NEN 7375). The results showed that the heavy metals how the zinc and lead, can retard the setting time of the mortars and this was observed in the impedance spectrums throughout cure time of mortars. During the tank test the electrical impedance of the contaminated mortars were lower than the reference mortar and the output of portlandite caused an increase in the electrical impedance values. The electrical test is a not destructive technique, faster than the leaching tests and in the future, it can be performed to aid environmental testing.

Abstract: Legendre polynomial method which describes the structure and incorporates automatically the boundary conditions in constitutive and propagation equations is used to model acoustic wave cylindrical resonators. It is the first time this method is applied to study standing rather than propagative waves. The advantage of this approach is, in a unique formulation, to take into account electric sources. The analytical and numerical resolutions are presented to highlight the potentialities of the Legendre polynomial approach. The vibration characteristics of piezoelectric discs with regard to diameter to thickness D/H ratios are analyzed by the three dimensional modeling approach through both modal and harmonic analyses. Resonance and antiresonance frequencies, electric input impedance, dispersion curves, field profiles and electromechanical coupling coefficient, easily obtained, are presented for PZT5A resonator piezoelectric discs. To validate our approach, the results using our 3D polynomial modelling of acoustic wave resonator are compared with those obtained by an approximated analytical method. The developed software proves to be very efficient to retrieve the radial modes of all orders.

Abstract: The use of piezoelectric material as transducer is prevalent. Piezoelectric bending mode element can be used for vibration energy harvesting because it can convert mechanical energy into electrical energy. In this article, electrical impedance characterization and equivalent circuit of triple-layer piezoelectric bender are discussed. Triple-layer piezoelectric bending device is fabricated, measured and modeled. This paper is aimed to explore simple but practical equivalent circuit models, expressed using electrical parameters of triple-layer piezoelectric bender and investigate the applicability of the Van Dyke circuit model and the complex circuit model in modeling the specimen’s equivalent circuit. The models produced impedance curves that closely matched the impedance measured for piezoelectric sample. The impedance characterization can provide a good understanding on the electrical behaviors of the triple layer piezoelectric bender when analyzing the performance of piezoelectric device.