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Comparison of parameters of selected types of commercial lithium-ion batteries
Špina, Martin ; Libich, Jiří (referee) ; Bača, Petr (advisor)
This thesis deals with operation principles of Lithium-ion battery. It evaluates its characteristics, advantages, and disadvantages. Technological processes and materials used in manufacturing and recycling are also discussed. Practical part of the thesis evaluates initial capacity of given Li-ion cells at different loads. Batteries are then cyclically charged and discharged, and its capacity and other parameters are determined. Electrochemical impedance spectroscopy data are also taken and evaluated for batteries in new-like condition, used batteries and cycled batteries as the capacity fades.
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Accelerated testing of lightfastness of indoor furniture coatings
Kulhánková, Michaela ; Drábková, Klára (referee) ; Dzik, Petr (advisor)
This bachelor thesis deals with the study of the current methods of testing and evaluation of lightfastness of interior paints. Their fading is caused mainly by the influence of solar radiation. The first part provides the basic information needed to understand the experiment. In the second part, wood samples with various white varnishes and coatings were subjected to accelerated testing of lightfastness. The experiment was performed by exposing these samples to xenon lamp through the window glass filter in the solar chamber. Changes in the color of the samples were evaluated based on the measurement of the reflection spectra from which the colorimetric quantities were calculated and then displayed in the color space CIE 1976 L*a*b*. The conclusion was focused on the final real life of the samples, their mutual comparison and evaluation of the most suitable materials.
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Degradation test of polymer material
Chleboun, Jiří ; Gvritishvili, Roman (referee) ; Vaněk, Jiří (advisor)
Basic knowledge of photovoltaic energy transformation, devices and materials, used in photovoltaics are summarized in this master’s thesis. Sort of degradation factors and its consequences of the photovoltaic panels are described there. Detail reviews of degradation tests are processed at the end of theoretical part. The main purpose of this research is selected covering materials dielectric properties change monitoring. These covering materials were influenced of accelerated thermal aging and increased humidity.
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Durability of Polyehtylene Ribbons from Netwrap
Huljak, Pavel ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
This diploma thesis deals with the measurement of mechanical properties and accelerated aging of monoaxially stretched polyethylene strips coming from three types of polymeric mesh, which serves to pack hay on baling machines. The strength of the strips is evaluated from two points of view. The first one is static tensile strength measured before and after accelerated aging at 23 °C and 40 °C, the second one determines the strength as the weight that causes the strip failure on a simple machine at 23, 40, 60 and 80 ° C. The results show that the smallest static strength has the least stabilized strip, which, on the other hand, revealed the highest strength in a dynamic loading. The change of supermolecular structure was evaluated by calorimetric measurements. The data shown only very little change of inner structure due to the average response of the whole crystalline phase comprising relatively wide distribution of crystallites. It is more than probable that supermolecular structure had been changed but the method is not sensitive to see the change of orientation of lamellae and macromolecular chains in them.
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Influence of aging on sandwich materials properties
Smékal, Aleš ; Löffelmann, František (referee) ; Klement, Josef (advisor)
The first part of the master’s thesis deals with sandwich materials. Starting with composition of parts which the sandwich panel is made of. The thesis continues with loading distribution and testing of entire sandwich panel. The impact of environment is considered as well. The second part is its goal – determine degradation of the properties of sandwich panels with metal sheets and core after 15 years aging in the common atmosphere and aging in moistheat and salt environment by experiment.
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Degradation test of polymer material
Darebný, Tomáš ; Špinka, Jiří (referee) ; Vaněk, Jiří (advisor)
Basic knowledge of photovoltaic energy transformation, devices and materials, used in photovoltaics are summarized in this bachelor’s thesis. Sort of degradation factors of the photovoltaic panels and the norm ČSN EN 61215, are described there. The main purpose of this research is monitoring the change of volume and surface resistivity of selected covering materials. These covering materials were influenced of increased humidity.
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Physical-chemical property characterisation of thin reflective layers on silicon substrates
Rozsívalová, Zdeňka ; Studýnka, Jan (referee) ; Krčma, František (advisor)
This thesis deals with surface analysis and characterization of optical features of thin films created by hexamethyldisiloxane (HMDSO) plasma polymerization on silicon wafers. The RF plasma industrial deposition equipment was used for the thin layers formation. These thin films serve as protective coatings on the reflective layer in the car light or solar panels. Theoretic part gives basic information about plasma, its occurrence, features, diagnostics and applications. Thin layers, their production and characterization are discussed here, too. Theoretic description of monomer material (including the group of other organosilicones) is also presented here. The FTIR spectroscopy and elipsometry are mentioned as the main methods for thin films characterisation. Because material during its practical use degrades due to external conditions, the influence of them on the thin layer properties is studied using the accelerated aging of created films. Industrial deposition chamber AluMet 1800V made by Leybold Optics, Ltd. installed in Zlin Precision company was used for the thin films production. Thin films were created under different conditions that were selelected near to the real conditions used in technology. Various applied powers (2-5 kW) were used for the deposition under different monomer flows. Further, the influence of oxygen addition on the created film properties was investigated. The deposition process was monitored by optical emission spectroscopy. The spectrometer Jobin Yvon Triax 320 with CCD detector was used. The selected part from every samples set was exposed by UV radiation (48 hours at radiation density of 0.68 W/m2 at 340 nm) to simulate the probable conditions during the layers real use. The surface properties were investigated by measurement of reflected light spectral intensity in the visible range at different angles. The angle between incident and reflected beam was varied in the interval of 40 - 150° with 10° step. The influence of sample preparation conditions as well as their aging effect was studied at the selected angles. Spectral reflectance doesn´t depend significantly on applied discharge power and oxygen addition. The significant shift of reflectance into the red part of spectrum was observed at UV exposed samples more or less independently on the applied discharge power of monomer flow rate. Addition of oxygen during the deposition suppresses this effec significantly. Characterization of thin layer structure was done by FTIR spectroscopy. No significant changes were observed in the structure at different discharge powers of monomer flow rates except total absorption intensities that are proportional to the layr thickness. The oxygen addition, of course, changes the structure significantly. These results are only preliminary because the layers were very thin (deposition conditions were near to the common process standard) and thus the signal/noise ratio was relatively low.
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Influnce of chemical composition on mechanical properties of LLDPE stretch film
Vojáček, Jakub ; Tocháček, Jiří (referee) ; Poláček, Petr (advisor)
Thesis summarizes the problems of production and use of stretch film. The change of strength, ductility and relative relaxation effect in different times of drawing from role in three weeks was observed. Further, change of strength and ductility due to changes in the rate of deformation, exposure to accelerated aging in a UV chamber and changes in the loading direction were observed. Mechanical tests were realized on a tensile tester, relaxation tests on DMA and crystallinity changes were observed on the DSC. Relationship between chemical composition of stretch film and mechanical and thermomechanical properties were studied. It was found that chemical composition essential for stretch film properties. However, due to the impossibility to distinguish effects of chemical composition and process parameters was impossible to find clear relation describing this relationship.
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