Centrum výzkumu a využití obnovitelných zdrojů energie

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    Comparison of Methods for the Measurement of Piezoelectric Coefficients
    (IEEE, 2013-04-03) Fialka, Jiří; Beneš, Petr
    The charge constant of piezoelectric material is one of the crucial constant values. At the present time, the measurement of this value is mostly realized by means of three techniques: the frequency method, the laser interferometer technique, and the quasi-static method. These techniques have been practically applied to piezoelectric ceramic samples. Our paper presents comparison of the individual methods with regard to their accuracy and the demands placed on the instrumentation and preparation of the piezoelectric material samples. A soft ceramic product marketed under the production code of NCE51 was used in the experiments. The methods are described in detail, including the process of sample preparation, description of the experiments, and procedure of alculating coefficients from the measured values.
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    Hybrid Energy System - Optimization and New Concept
    (Lublin University of Technology, 2014-09-16) Morávek, Jan; Mastný, Petr
    Paper presents a research related to the design of a new concept of hybrid energy system. It describes actually used concepts and the benefits of new design. Subsequently, the problems of the proper systems setting and working conditions are discussed and the new concept of the systems settings is presented. Research is further enhanced by comparing with the simulation model assuming the weather data acquired for the test location. The measured data are compared with the results of simulation.
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    Electrochemical Behaviour of Nanoscale Ni Modified Screen-Printed Carbon Electrodes in Corrosion Tests and Hydrogen Evolution Electrocatalysis
    (ESG, 2015-09-01) Škantárová, Lenka; Oriňáková, Renáta; Straková Fedorková, Andrea; Bača, Petr; Sedlaříková, Marie; Oriňák, Andrej
    Corrosion resistence and electrocatalytic aktivity were examined for Ni nanoparticles ( NiNPs) coated screen printed carbon based electrodes ( SPCEs) being a novel alternative to unmodified electrodes. Corrosion as well as hydrogen evolution reaction (HER) measurements were performed in 1 mol/L H2SO4 using potentiodynamic polarization method, moreover electrochemical impedance spectroscopy (EIS) measurements were carried out
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    Negative lead-acid battery electrodes doped with glass fibres
    (ESG, 2015-03-01) Bača, Petr; Křivík, Petr; Vaculík, Sebastian; Tošer, Pavel
    Negative lead-acid battery electrodes doped with microscopic glass fibres show similar properties during accelerated partial state of charge cycling as those doped with carbon or titanium dioxide, including a long cycle life of up to 84,000 cycles. The optimum amount of this additive in the negative active mass seems to be between 2 and 3 wt. %.
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    Effect of Heat Treatment on the Corrosion and Mechanical Properties of Electrolytical Composite Ni-B Coatings
    (ESG, 2014-08-01) Oriňáková, Renáta; Oriňák, Andrej; Kupková, Miriam; Sabalová, Mária; Straková Fedorková, Andrea; Kabátová, Margita; Kaľavský, František; Sedlaříková, Marie
    Electrodeposition of composite coatings with nickel matrix and boron micro-particles was investigated. Nickel - boron layers were deposited potentiodynamically at 12.5 mV/s on cylindrical samples prepared from iron powder in a stirred heterogeneous system formed by a Watts type nickel plating bath and dispersed boron micro-particles. The effect of boron powder amount in plating bath and heat treatment on the corrosion resistance and hardness of the composite Ni-B coatings was evaluated. Corrosion properties of coated cylindrical iron samples were investigated in 1 mol dm-3 NaCl solution using potentiodynamic polarization method. The structure of coating layers was established using scanning electron microscopy (SEM) and light optical microscopy (LOM). The content of incorporated boron particles increased with the boron amount in plating bath. Homogeneous distribution of boron particles in deposited coating layer was observed for both as-deposited samples and samples heat treated at 400 °C. Boron particles were not observed on the surface of the deposits heated at higher temperatures. Generally, addition of boron micro-particles to the nickel matrix as well as the heat treatment deteriorated the corrosion resistance of iron samples coated with composite Ni-B films. The dependence of the corrosion properties of composite layers on boron particle loading was not proved. The decrease of microhardness on the surface but increase of microhardness on the cross- section of composite Ni-B coating layer due to the heat treatment was observed.