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Relationship between thermo-oxidative stability and soil quality indicators
Svatoň, Karel ; Doležalová Weissmannová, Helena (referee) ; Kučerík, Jiří (advisor)
This diploma thesis focuses on the use of thermogravimetry as quick and low-cost method in the analysis of soil quality. Most of the currently used methods for analyzing some soil properties are, unlike thermogravimetry, demanding especially for pretreatment and analysis time. Previous research has shown an interesting correlation between thermogravimetry data and some soil properties, but to obtain these correlations, it is necessary to keep the analyzed soils at 76% relative humidity. The aim of this work was to determine whether similar correlations can also by achieved at lower relative humidities. Therefore, soil samples in this work were thermogravimetrically analyzed at 43% relative humidity. That humidity is closer to laboratory conditions and it is also easier to be reached by most of commercially available thermogravimeters. Next aim of this thesis was to find whether thermogravimetric data correlate with other soil properties, especially microbiological indicators of soil quality. Results showed that thermogravimetry of soil samples correlates with standard methods even at 43% humidity. Furthermore, it was found that they also correlate with selected microbiological parameters, such as anaerobic ammonification or urease activity. These results suggest the possibility of using thermogravimetry analysis at broader spectrum of soil properties, without the need for pretreatment of samples and at different (relevant) soil moisture.
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Výzkum interakce vodíku s vakacemi, dislokacemi a hranicemi zrn v Ti
Knapp, Jan ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
This thesis deals with the system of titanium and hydrogen. Interstitial hydrogen alloys and hydrides are subject to intensive investigation, both theoretical and experimental. It has been proved, that absorbed hydrogen lowers the formation energy of defects in metals, and thus works as the so called 'defactant'. Surfactants on the surfaces of liquids lower the surface tension; defactants in solids lower the formation energy of defects. It has also been proved, that titanium absorbs hydrogen readily, when exposed to high temperature, or high pressure (fugacity); while different loading conditions lead to different features of the final sample. Beside ordinary coarse grained titanium, ultra-fine grained titanium shall be studied in present work, due to its high content of defects. Positron Annihilation Life-time Spectroscopy, a non-destructive technique sensitive on open-volume defects, shall be of prime importance in our investigation. We shall further use the X-ray diffraction, Micro-hardness measurements and Differential Scanning Calorimetry together with Thermogravimetry. Lastly, we shall strongly benefit from using existing computational tools like the Vienna ab-initio Simulation Package, or Pos330; a program for positron life--times calculations.
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Determination of moisture content in electrical insulating materials
Šebesta, Petr ; Rozsívalová, Zdenka (referee) ; Frk, Martin (advisor)
This work is based on determination of moisture content in electrical insulating materials materials and ways to measure the moisture. In the theoretical section describes the methods of thermal analysis, and subsequently described in detail Thermogravimetry method, which is used in the measurement. Measurements are made using the Moisture Analyzer RADWAG 60 W/H connected with a PC, using a variety of samples from inorganic to organic. A great variety of samples was chosen because of demonstrations thermogravimetric methods and a better understanding of wetting and drying of different materials.
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Interaction Between Hyaluronan and Amphiphilic Molecules
Venerová, Tereza ; Burget, Ladislav (referee) ; Čeppan, Michal (referee) ; Pekař, Miloslav (advisor)
This work is focused on interaction between hyaluronan (Hya) and amphiphilic molecules. Using fluorescent probes method were carried out screening of the interaction of various surfactants with Hya. For further examination was chosen cetyltrimethylammonium bromide (CTAB). Interactions in this system have also been studied using fluorescence correlation spectroscopy (FCS), and additionally were performed initial tests of the cytotoxicity of the system. As an alternative CTAB were also used hydrophobically modified amino acids. Results showed their self-aggregation, but their interactions with hylauronanem was not as strong as with CTAB. The interaction of gel systems Hya-CTAB have also been studied, and was found to contain a hydrophobic domain capable solubilize hydrophobic substance. Thermogravimetric have been established that are able to contain up to 98% wt. water and rheologically were characterized their mechanical properties. These are tunable due to molecular weight (MW) of the hyaluronate. With increasing value of MW increases mechanical strength of the gel and decreases its fluidity.
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Oxidation behavior adjustment for TiAl intermetallics by Al-Y multilayers
Handrk, Jiří ; Tkachenko, Serhii (referee) ; Jan, Vít (advisor)
Mechanické vlasnosti intermetalika na bázi titan hliník Ti-46Al-7Nb-0.7Cr-0.1Si-0.2Ni jsou konstatní do teploty 700 °C. Nad touto teplotou slitina oxiduje. Cílem této práce bylo zlepšit oxidační vlastnosti pomocí kovové multivrstvy na bázi yttrium hlinik. Pro depozici vrstev byla použita metoda PVD. Na vzorky byly naneseny vrstvy čistého ytria nebo kombinace yttrium, hliník. Vzorky byly následně žíhány v inertní atmosféře na 700°C a 900°C nebo nebyly. Kvalita nanesených vrstev byla zkoumána pomocí scratch testu a EDS analýzi. Dále byly vzorky izotermicky oxidovány na 900°C po dobu 100 hodin. Na vzorcích byly po oxidaci prováděny měření pevnosti v tříbodovém obybu a měření hmotnosti. Chemické složení oxidické vrstvy bylo vyhodnoceno pomocí EDS. Žádná z vrstev s nebo bez žíhání neprokázaly zlepšení oxidických vlastností. Vyšší teplota žíhání prokýzala zlepšení mechanických vlastnotí vrstvy, ale zhoršení materiálu.
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Thermo-oxidative stability of mixtures of vegetable oils
Kovačíková, Barbora ; Lehocký,, Marián (referee) ; Zemanová, Jana (advisor)
Rostlinné oleje se používají v mnoha odvětvích chemického průmyslu. V průběhu zpracování konkrétního produktu, ve kterém jsou rostlinné oleje použity, dochází často ke zvyšování teploty. Vyšší teplota urychluje průběh auto-oxidace což negativně ovlivňuje stabilitu olejů nebo výrobků z nich připravených. Mezidruhové mísení olejů je poměrně častým jevem jak při samotné výrobě tak i ve finálním výrobku. Cílem této práce bylo stanovit termo-oxidační stabilitu šesti čistých rostlinných olejů a jejich binárních směsí. První část práce zkoumá oleje a připravené směsi pomocí metody diferenciální kompenzační kalorimetrie. Tato metoda umožnila pochopení vztahů mezi termo-oxidačním chováním olejů a jejich směsmi pomocí stanovení teplot degradace. Přímá souvislost mezi obsahem mastných kyselin a stabilitou byla prokázána pouze zčásti, stejně tak jako původní předpoklad, že přídavek stabilnějšího olej zvýší stabilitu oleje méně stabilního. V několika případech docházelo dokonce ke snížení stability pod teplotu degradace obou čistých olejů. Ve druhé části byl zjišťován mechanismus pro-oxidační fáze vedoucí k degradaci olejů pomocí termogravimetrie, která ukázala přírůstek hmotnosti ve vzorcích oleje způsobeného absorpcí kyslíku a tvorbou peroxidů předcházející degradaci. V tomto případě již bylo možné pozorovat jistou souvislost mezi obsahem mastných kyselin a vzrůstem hmotnosti, pouze však jen pro čisté oleje. Ani v tomto případě nebyla prokázána aditivita vlastností způsobujících stabilitu směsí rostlinných olejů.
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Application of thermal analysis in energetics
Skala, Šimon ; Šnajdárek, Ladislav (referee) ; Moskalík, Jiří (advisor)
This bachelor´s thesis deals with the thermal analysis. The first part contains general information about thermal analysis. The second part provides overview basic types of thermal analysis methods. In the third part there are described in detail two main thermal analysis methods. The last section is focused on realization and evaluation of thermogravimetric analysis of sample of a brown coal.
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Thermal analysis of fuels
Šrámek, Zbyněk ; Hrnčířová, Michaela (referee) ; Moskalík, Jiří (advisor)
The main goal of this thesis is to introduce the field of thermal analysis as an independent scientific discipline. The first section is mostly informative and introduces into a concept of thermal analysis. The second part describes the most fundamental and essential methods of thermal analysis and the last section is focused on evaluating a real thermogravimetric experiment which deals with biomass sample.
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