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Deformation Behaviour of Advenced Magnesium and Aluminium Alloys
Jäger, Aleš
Aluminum and magnesium alloys are often considered as promising materials due to high strength/density ratio. In general, light alloys are very attractive structural materials for applications where environmental protection or weight reduction play essential role. Therefore, it is of interest to investigate microstrucrure and its changes during plastic deformation because it helps to understand the nature of solute effect and processes taking place during plastic deformation. The aim of this work is to reveal microstructures, deformation characteristics and micromechanisms of plastic deformation at different strain rates and temperatures in selected light alloys. Two commercially available alloys were used in this work: AZ31 rolled magnesium alloy and AA6082 extruded aluminium alloy. These alloys were studied with the help of various experimental techniques such as tensile testing, light microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction. Abstrakt Hlinikove a horcikove slitiny jsou povazovany za vysoce perspektivni materialy, protoze nabizeji velmi dobry pomer pevnosti k hustote. Tyto lehke slitiny nalezaji uplatneni pfedevsim v aplikacich, kde je kladen duraz na ochranu zivotniho prostredi a nebo snizeni hmotnosti. Detailni studium jejich mikrostruktury a deformacniho...
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Aliphatic polyester-based nanoparticles as drug delivery systems
Jäger, Alessandro ; Štěpánek, Petr (vedoucí práce) ; Sedláček, Jan (oponent) ; Sikora, Antonín (oponent)
3 SOUHRN Nanočástice vytvořené z biodegradovatelných polymerů jsou považovány za jeden z nejslibnějších systémů pro transport léčiv při biolékařských aplikacích. Tato disertační práce je proto zaměřena na syntézu a charakterizaci nových biodegradovatelných alifatických kopolyesterů PBS/PBDL (poly(butylen sukcinát-co-butylen dilinoleát) pro cílenou dopravu léčiv. Tyto polymery byly použity pro přípravu sférických nanočástic (poloměr < 60 nm) s úzkou distribucí rozměrů pomocí jednokrokové metody nanoprecipitace bez přítomnosti povrchově aktivních látek. Rozměr vytvořených polymerních nanočástic bylo možno řídit v požadovaném rozsahu volbou koncentrace polymeru, výběrem organického rozpouštědla, použitím směsi organických rozpouštědel nebo nastavením teploty a iontové síly. Optimalizací těchto parametrů bylo možno připravit nanočástice s rozměry menšími než 100 nm, výhodou tohoto postupu je možnost přípravy ve velkých množstvích. Struktura nanočástic byla podrobně charakterizována rozptylovými technikami a transmisní elektronovou mikroskopií. Kombinace statického a dynamického rozptylu světla ukázala, že nanočástice jsou porézní a tedy jejich interní struktura není kompaktní. Zachycení vody v pórech nanočástice zajišťuje na jedné straně jejich stabilitu, na druhé straně umožňuje rychlou degradaci, která byla...
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Deformation Behaviour of Advenced Magnesium and Aluminium Alloys
Jäger, Aleš
Aluminum and magnesium alloys are often considered as promising materials due to high strength/density ratio. In general, light alloys are very attractive structural materials for applications where environmental protection or weight reduction play essential role. Therefore, it is of interest to investigate microstrucrure and its changes during plastic deformation because it helps to understand the nature of solute effect and processes taking place during plastic deformation. The aim of this work is to reveal microstructures, deformation characteristics and micromechanisms of plastic deformation at different strain rates and temperatures in selected light alloys. Two commercially available alloys were used in this work: AZ31 rolled magnesium alloy and AA6082 extruded aluminium alloy. These alloys were studied with the help of various experimental techniques such as tensile testing, light microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction. Abstrakt Hlinikove a horcikove slitiny jsou povazovany za vysoce perspektivni materialy, protoze nabizeji velmi dobry pomer pevnosti k hustote. Tyto lehke slitiny nalezaji uplatneni pfedevsim v aplikacich, kde je kladen duraz na ochranu zivotniho prostredi a nebo snizeni hmotnosti. Detailni studium jejich mikrostruktury a deformacniho...
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Temperature and pressure correlation for volume of gas hydrates with crystal structures sI and sII.
Vinš, Václav ; Jäger, A. ; Hielscher, S. ; Span, R. ; Hrubý, Jan ; Breitkopf, C.
The temperature and pressure correlations for the volume of gas hydrates forming crystal structures sI and sII developed in previous study [Fluid Phase Equilib. 427 (2016) 268], focused on the modeling of pure gas hydrates relevant in CCS, were revised and modified for the modeling of mixed hydrates in this study. A universal reference state at temperature of 273.15 K and pressure of 1 Pa is used in the new correlation. Coefficients for the thermal expansion together with the reference lattice parameter were simultaneously correlated to both the temperature data and the pressure data for the lattice parameter. The new correlation is in good agreement with the experimental data over wide temperature and pressure ranges from 0 K to 293 K and from 0 to 2000 MPa, respectively. The new correlation provides significantly better agreement with the experimental data for sI hydrates compared to the original correlation. The results of both correlations are comparable in case of sII hydrates.
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Phase equilibria of carbon dioxide and methane gas-hydrates predicted with the modified analytical S-L-V equation of state
Vinš, Václav ; Jäger, A. ; Hrubý, Jan ; Span, R.
Gas-hydrates (clathrates) are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO2 separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS) [A. Yokozeki, Fluid Phase Equil. 222–223 (2004)] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO2- and CH4-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.
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