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Number of results: 10
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Abstract

Al2Cu phase has been obtained by melting pure metals in the electric arc furnace. It has been found that the intermetallic phase undergoes selective corrosion in the H3PO4 aqueous solutions. Aluminium is dissolved, the surface becomes porous and enriched with copper. The corrosion rate equals to 371 ± 17 g·m–2·day–1 (aerated solution) and 284 ± 9 g·m–2·day–1 (deaerated solution). The surface of Al2Cu phase after selective corrosion was characterised by using electrochemical impedance spectroscopy. It was found that the surface area of the specimens increases with temperature due to higher corrosion rate and is between 2137 and 3896 cm2.
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Abstract

The paper presents the family of three analyzers allowing to measure impedance in the range of 10 Ω<|Zx|<10 GΩ in a wide frequency range from 10 mHz up to 100 kHz. The most important features of the analyzer family are: miniaturization, low power consumption, low production cost, telemetric controlling and the use of an impedance measurement method based on digital signal processing (DSP). The miniaturization and other above-mentioned features of the analyzers were obtained thanks to the use of the newest generation of large-scale integration chips: e.g. “system on a chip” microsystems (AD5933), 32-bit AVR32-family microcontrollers and specialized modules for wireless communication using the ZigBee standard. When comparing metrological parameters, the developed instrumentation can equal portable analyzers offered by top worldwide manufacturers (Gamry, Ivium) but outperforms them on smaller dimensions, weight, a few times lower price and the possibility to work in a distributed telemetric network. All analyzer versions are able to be put into medium-volume production.
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Abstract

In this paper the method of fast impedance spectroscopy of technical objects with high impedance (|Zx| ≥1 GΩ) is evaluated by means of simulation and a practical experiment. The method is based on excitation of an object with a sinc signal and sampling the response signals proportional to current flowing through and voltage across the measured impedance. The object’s impedance spectrum is obtained with the use of continuous Fourier transform on the basis of linear approximations between samples in two acquisition sections, connected with the duration of the sinc signal. The method is first evaluated in MATLAB by means of simulation. An influence of the sinc signal duration and the number of samples on impedance modulus and argument measurement errors is explored. The method is then practically verified in a constructed laboratory impedance spectroscopy measurement system. The obtained acceleration of impedance spectroscopy in the low frequency range (below 1 Hz) and the decrease of the number of acquired samples enable to recommend the worked out method for implementation in portable impedance analyzers destined for operation in the field.
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Abstract

The suitability of low-cost impedance sensors for microbiological purposes and biofilm growth monitoring was evaluated. The sensors with interdigitated electrodes were fabricated in PCB and LTCC technologies. The electrodes were golden (LTCC) or gold-plated (PCB) to provide surface stability. The sensors were used for monitoring growth and degradation of the reference ATCC 15442 Pseudomonas aeruginosa strain biofilm in invitro setting. During the experiment, the impedance spectra of the sensors were measured and analysed using electrical equivalent circuit (EEC) modelling. Additionally, the process of adhesion and growth of bacteria on a sensor’s surface was assessed by means of the optical and SEM microscopy. EEC and SEM microscopic analysis revealed that the gold layer on copper electrodes was not tight, making the PCB sensors susceptible to corrosion while the LTCC sensors had good surface stability. It turned out that the LTCC sensors are suitable for monitoring pseudomonal biofilm and the PCB sensors are good detectors of ongoing stages of biofilm formation.
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Abstract

This paper adopts a fractional calculus perspective to describe a non-linear electrical inductor. First, the electrical impedance spectroscopy technique is used for measuring the impedance of the device. Second, the experimental data is approximated by means of fractional-order models. The results demonstrate that the proposed approach represents the inductor using a limited number of parameters, while highlighting its most relevant characteristics.
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Abstract

In this work studies ofM OVPE growth of InAlGaAs/AlGaAs/GaAs heterostructures are presented. The HRXRD and SIMS measurements indicate the high structural and optical properties as well as high uniformity oft hickness and composition ofI nAlGaAs quantum wells. This work is the .rst step towards elaboration oft he technology oft he strained InAlGaAs/GaAs heterostructures for advanced optoelectronic devices working in the visible part oft he spectrum. The investigations ofSi (n-type), Zn (p-type) .-doped GaAs epilayers and centre Si-.-doped InxGa1-xAs single quantum well (SQW) are presented. The .-doping layer was formed by SiH4 or DEZn introduction during the growth interruption. The electrical and optical properties oft he obtained structures were examined using C-V measurement, EC-V electrochemical pro.ler, Raman spectroscopy (RS), photore.ectance (PR) and photocurrent (PC) spectroscopies. Technology oft hick GaN layers grown on sapphire by HVPE is very promising as a part off reestanding GaN substrates manufacturing. Further works will be focused on the optimisation of growth, separating layers from substrates and surface polishing. The in.uence oft he growth parameters on the properties of( Ga, Al)N/Al2O3 and Mg dopant incorporation was studied.
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Abstract

In this study, the corrosion properties of Ti-6Mo-6V-5Cr-3Sn-2.5Zr alloy were investigated as a function of the cold rolling ratio and annealing temperature. The annealing treatment was carried out at temperature of 680°C, 730°C, and 780°C. The highest corrosion potential observed in the specimen with a 10% rolling ratio was 179 mV, which was more positive than that of the non-rolled specimen (–0.214 Vssc). The lowest corrosion current density (1.30×10–8 A/cm2) was observed in the non-rolled specimen which suggested that the integrity of its passive oxide layer was superior to that of the cold-rolled specimens. Time-dependent EIS evaluation revealed that the consistency of the passive oxide layer was highly affected by the subjected rolling ratio over time.
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Abstract

In this paper, the effect of the resolution of an analogue-to-digital converter (ADC) on the accuracy of timedomain low-frequency electrical impedance spectroscopy is examined. For the first time, we demonstrated that different wideband stimuli signals used for impedance spectroscopy have different sensitivities to the resolution of ADC used in impedance spectroscopy systems. We also proposed Ramp and Half-Gaussian signals as new wideband stimulating signals for EIS. The effect of ADC resolution was studied for Sinc, Gaussian, Half-Gaussian, and Ramp excitation signals using both simulation and experiments. We found that Ramp and Half-Gaussian signals have the best performance, especially at low frequencies. Based on the results, a wideband electrical impedance spectroscopy circuit was implemented with a high accuracy at frequencies bellow 10 Hz.
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Abstract

Point of present exploration was to figure out the anticorrosion activity of Acacia Cyanophylla (Saligna leaves) extract on the corrosion of mild steel in dilute sulfuric acid medium, using weight loss measurements and electrochemical impedance spectroscopy. The result of the study revealed that the extract act as a potent inhibitor on mild steel in acid medium. The increase in inhibitor concentration and immersion time showed a positive effect on inhibition efficiency. EIS exhibited one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. The increase of phase shift (n) in presence of (ACLE) lower surface roughness. This change reveals the adsorption of the inhibitor compound on the steel surface. According to the results of weight loss measurements, the adsorption of the extract on the steel surface can be described by the Langmuir isotherm. The inhibition mechanism of (ACLE) molecules involves physical interaction between the inhibitor and metal surface. Additionally, Protective film formation against acid attack was confirmed by FT-IR and AFM techniques.
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