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The Influence of Solvents and Salts on the Properties of High-Voltage Cathode Materials
(ESG, 2015-07-24) Kazda, Tomáš; Vondrák, Jiří; Sedlaříková, Marie; Gómez-Romero, Pedro; Musil, Michal; Čudek, Pavel; Straková Fedorková, Andrea; Kašpárek, Vít
Lithium - ion batteries play an increasingly important role in the battery industry and they have become the dominant source of energy in the recent years, especially for portable electronic devices due to their high gravimetric energy density. This article examines the influence of mixtures of solvents with different combinations of lithium salts on the stability of two types of high-voltage cathode materials: LiNi0.5Mn1.5O4 and LiCr0.1Ni0.4Mn1.5O4 produced by a solid phase reaction. These materials were combined with several different electrolytes, cycled at various loads and higher temperature. Various combinations of solvents ethylene carbonate (EC), dimethyl carbonate (DMC) and Tetrahydrothiophene 1.1-dioxide (Sulfolane) were used for these measurements. Salts LiPF6 , LiNO3 and LiTFSI were used. The influence of solvents and salts on the properties of high-voltage cathode materials was tested by cycling at different current loads and by cycling at high temperature. It was found out, by LSV analysis, that the addition of Sulfolane increases the stability of electrolyte. The addition of chromium to the cathode material LiNi0.5Mn1.5O4 causes increasing of capacity and stability at high temperature. The combination of the cathode material LiCr0.1Ni0.4Mn1.5O4 with the electrolyte 1.5 M LiPF6 EC:DMC:Sulfolane 1:2:1 w/w/w leads to increased stability in comparison with other electrolytes.
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
Mathematical model of Mobile Circulatory Module for ex-vivo lungs perfusion
(IFAC, 2015-05-13) Šolc, František; Zezulka, František; Veselý, Ivo
The article deals with mathematical modelling of a system for ex-vivo lung perfusion. The system which is modelled here is named Mobile Circulatory Module and is designed for transport of live lungs namely porcine or human lungs. Transported lungs should be used for various research or even for transplantation. The article describes mathematical model of thermal circuit and hydraulic circuit which are vital parts of the MCM to secure living conditions of the transported organ. Mathematical model is simulated with MATLAB Simulink and shows good qualitative correspondence with real behavior of the system. Based on math model there is designed control algorithm for temperature control and there is discussed control of perfusion liquid as well.
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.
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.

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