Diploma thesis deals with the research of oxide interphase of ceramic composite in dependence on the amount of precursor used in sol – gel method for deposition of titanium dioxide thin layer on corundum.

Práce popisuje přípravu tenkých transparentních vrstev oxidu titaničitého metodou sol-gel procesu s reverzními micelami, které jsou jedinečným uskupením zajišťujícím uniformní velikost připravených částic. Neionogenní tenzid byl použit jako templát. Pomocí materiálového tisku, tedy specializovanou formou inkoustového tisku, byly připraveny tenké filmy oxidu titaničitého nanesením 1–4 vrstev. Po kalcinaci byly připravené vrstvy oxidu titaničitého charakterizované šířkou zakázaného pásu. Struktura vrstev byla popsána optickou mikroskopií a SEM. Fotokatalytická aktivita byla ověřena oxidační reakcí 2,6-dichlorindofenolu a rozkladem kyseliny stearové, která byla přímo natištěna na vrstvy oxidu titaničitého. Fotoindukovaná změna hydrofility byla studována pomocí měření kontaktního úhlu smáčení vody. Fotokatalytická účinnost připravených filmů rostla s počtem vrstev oxidu titaničitého.

The first part of this diploma thesis is dealing with conductivity of liquid electrolytes. The second part is about third generation gel electrolytes and thein conductivity. The electrolytes were inorganic salts LiClO4, LiBF4 and NaClO4 in an aprotic propylene carbonate (PC) -used as a solvent. Nanosized Al2O3 and TiO2 particles were, proportionally to the sample's volume, added to the both – blend and gel samples in an amount expressed by weight percentage (wt). Both liquid and gel electrolytes contained following amount on nanosorbent: 3,46% wt, 7,17% wt, 10,0% wt and 12,0% wt. The liquid electrolytes were gelled using commercially available precursor Superacryl (Spofa dental s.r.o.).

The present master´s thesis deals with the electrical properties of nanocomposite materials. Samples for the experiment are made epoxi resin and oxides TiO2 and Al2O3 as nanofillers in different percent performace. The samples nanocomposites are measured temperature dependence of the resistivity inside, dissipation factor and relative permittivity. It discusses the effect of the filler on the resulting electrical properties of the polymer.

Hybrid electric vehicles use lead acid batteries operating under partial charge. Battery life of these batteries is dependent on the speed of development of lead sulphate (PbSO4) to the negative electrodes. Different admixtures are affected battery life. This work deals with the influence of titanium dioxide on the negative active material in lead battery. Mainly devoted to the influence of the applied pressure.

The theoretical part of this doctoral thesis deals with determination of mercury and its species in aquatic systems. Special attention is paid to the use in situ sampling technique diffusive gradients in thin films technique (DGT) and its development. Current resin gels used for determination of mercury by DGT technique Duolite GT-73, Chelex-100 and Spheron-Thiol are described. Moreover, new types of resin gels including Iontosorb AV modified by imidazole or 6-mercaptopurine and commercially available titanium dioxide. Preparations of resin gels and their basic tests in model solution according to DGT Research are described. Mercury accumulation in relation to time and basic recovery test were tested and capacity of resins was determined. All tested resins meet the requirements of basic DGT Research tests and relative standard deviations of mercury in recovery tests were lower than 10 %. The sorption capacity of resins varied from 1,5 to 6 µmol.l-1 and decreased in following order: Duolite GT-73 > ISAV-IM > Chelex-100 > Spheron-Thiol > TiO2 > ISAV-MP. Mercury sorption on resins was investigated under conditions similar to those in natural waters. It was found that the ionic strength commonly occurring in natural waters does not affect the determination of mercury. The presence of chlorides significantly affects the determination of mercury using DGT with titanium dioxide and therefore this sorbent can not be recommended for the determination of mercury in sea waters. The accumulated amount of mercury, depending on the pH shows that all the sorbents can be used in natural waters with pH in the range form 4 to 8. Mercury sorption is most affected by the presence of humic acids, especially at ion-exchange resins containing other than thiol functional groups. The exception is titanium dioxide for which physical sorption of humic acid metal complexes is typical. Cadmium and copper in model solutions in the molar balance of the excess mostly influenced the sorption of mercury on Chelex-100 and Spheron-Thiol resins. After laboratory tests, the DGT units with studied sorbents were used for the determination of mercury in natural waters of South Moravia (Svratka, Jihlava and Svitava river). Mercury concentration determined using DGT units containing Duolite GT-73 resin was comparable to the total dissolved concentration of mercury in river water provided by direct determination using AAS technique. Order of magnitude smaller concentrations than the total dissolved mercury concentration were found using DGT containing Spheron-Thiol and ISAV-MP resins. These sorbents are probably able to capture only mercury present in the form of labile complexes. This can be used for speciation analysis if more DGT units with different resins are deployed together. Subtracting the measured DGT Spheron-Thiol or ISAV-MP concentrations from the DGT Duolite GT-73 concentration, information about the amount of mercury present in the form of stabile complexes can be obtained. The amount of mercury determined after application of DGT units containing ISAV-IM, Chelex 100 or TiO2 can probably represent the mercury fraction bound in even weaker complexes than fraction determined by Spheron-Thiol and ISAV-MP DGT.

Tenké vrstvy oxidu titaničitého byly imobilizovány na sodnovápenatá skla a skelný uhlík použitím jak techniky materiálového tisku tak metodou chemického napařování. Pro přípravu titaničitých solů byly použity metody sol-gelu a nebo hydrotermální syntézy. Struktura připravených vrstev byla zkoumána rastrovací elektronovou mikroskopií a mikroskopií atomárních sil. Krystalická struktura připravených TiO2 byla analyzovány pomocí XRD metody. Fotoindukováná superhidrofility pripravených vzorků byla charakterizována měřením kontaktních úhlů. Fotokatalytická aktivity připravených vzorků byla testována na fotokatalytické oxidaci 2,6-dichlorindofenolu a kyseliny mravenčí. V případě sol-gel vrstev byl zkoumán vliv množství naneseného TiO2 a množství PEG, který byl do solu přidán jako praskliny potlačující činidlo. V případě hydrotermálních vrstev byl zkoumán vliv času a teploty syntézy a množství vrstev na výslednou účinnost vzorku. U chemicky napařených vzorků byl zjišťován vliv intenzity záření. Byla porovnána fotokatalitická aktivita vrstev připravených materiálovým tiskem a chemickým napařováním a byl vyhodnocen nejaktivnější vzorek.

This thesis deals with novel trends in solder paste technology. It focuses on nanoparticle applications used as a tool for improving a state of the art lead free solder alloys. The recently published results about the impact of different types of nanoparticles on properties of newly-emerged nanocomposite solders are discussed and summarized in the thesis. Preparation, practical application and testing of new solder paste based on low temperature SnBi alloy with an admixture of titanium dioxide are also discussed. Finally, properties of solder joints using these solder pastes are investigated and the results are evaluated.

PhD (Physics) / Department of Physics / Dye sensitized solar cells (DSSCs) have attracted rapid interest over the recent years with prospect of emerging as a viable alternative to conventional silicon based solar cells. The photoanode of DSSCs comprises of dye molecules anchored to the surface of semiconductors such as TiO2. However, the major drawback of Titanium dioxide (TiO2) is its wide band gap (3.0 eV to 3.2 eV) which limits its photocatalytic activities to the ultraviolet region of the electromagnetic spectrum. Understanding the interaction of dye molecules with the surfaces of TiO2 is crucial for optimizing light-harvesting, photoconversion function and photocurrent densities in DSSCs. The three polymorphs of TiO2 are anatase, brookite and rutile. The optical properties of brookite semiconductor have not been much studied although brookite has been reported to have good photocatalytic properties. In this work, Density functional theory (DFT) computational approach was used through various computational softwares which are CASTEP, GAUSSIAN, GAUSSUM, GPAW, ASE, and AVOGADRO with B3LYP, LANL2DZ, PBE, and GGA functional to explore the photocatalytic properties of the typical ruthenium N3 complex, polyenediphenyl-aniline dye moiety, croconate dye molecules and three modelled surfaces of brookite which are (TiO2)5, (TiO2)8 and (TiO2) 68 for application in DSSCs. We also studied the absorption of the corresponding dye molecules on the three surfaces of brookite TiO2. Our findings showed strong binding ability, good electronic coupling, efficient charge separation, spontaneous electron injection and good spectral properties upon adsorption of the dye molecules to brookite TiO2 semiconductor clusters. Our findings on the optical absorption spectra of ruthenium N3 dye, croconate dye and polyenediphenyl-aniline dye molecule absorbed on (TiO2)5 and (TiO2)8 brookite cluster shows bathocromatic shift of the absorption maxima to higher wavelength and improve optical response of TiO2 brookite cluster. A red spectra shift and absorption over a wide range of the solar spectrum in the visible and near infra-red region of the solar spectrum was achieved upon absorption of the ruthenium N3 complex and polyenediphenyl-aniline dye molecules on (TiO2)5 and (TiO2)8 brookite cluster. The results generally suggest that the absorption of dye molecules on TiO2 brookite cluster improves its spectra responsivity in the UV region and makes it possible to absorb over the whole spectrum range, that is, the UV, visible and near infra – red region of the solar spectrum. Our findings also showed good electron injection kinetics from the dye to TiO2 brookite clusters, which suggests higher photocurrents density and open circuit voltage in DSSCs. / NRF

La photocatalyse laisse entrevoir un large champ d’applications dans de nombreux domaines parmi lesquels figurent principalement ceux du traitement et de la purification de l’eau et de l’air. Ceci constitue une des raisons pour lesquelles les études fondamentales des processus de dégradation des molécules organiques à la surface des photocatalyseurs concernent le plus souvent les phases liquides et gazeuses. Les développements plus récents des applications de la photocatalyse dans le domaine des surfaces autonettoyantes ont soulevé des problématiques fondamentales concernant les mécanismes de dégradation photocatalytique de composés solides tels que les suies et les acides gras. Ces problématiques restent encore peu abordées dans la littérature malgré les enjeux majeurs en terme environnemental et méritent donc des travaux de recherche plus approfondis. Cette thèse porte sur l’étude des modes de dégradation photocatalytique de dépôts solides d’acide stéarique (AS) sur des couches minces de dioxyde de titane. Dans ce travail, des approches expérimentales originales basées sur la microscopie optique sont mises en œuvre pour suivre la dégradation photocatalytique de ces dépôts d’AS à l’échelle microscopique sous exposition à la lumière ultraviolette. Les dépôts d’AS se présentent sous forme d’îlots microscopiques présentant une distribution de taille et de forme. Sur la base d’un nouveau modèle cinétique que nous proposons, le lien existant entre la vitesse de dégradation photocatalytique du dépôt et la distribution de taille initiale de la population d’îlots est mis en évidence. Le modèle cinétique développé permet de rationaliser nos résultats et de concilier d’autres résultats, jusqu’alors contradictoires, de la littérature. Ce travail propose en outre une étude originale sur la dégradation photocatalytique de microcristaux d’AS déposés sur des couches minces de TiO2 microstructurées qui a permis d’appréhender le rôle des radicaux libres dans le processus de dégradation photocatalytique. La démarche expérimentale est basée sur le lien étroit existant entre l’orientation des molécules, inhérente à la structure propre des microcristaux, et les directions des plans cristallographiques {hkl}. Ainsi, nous mettons en évidence une dépendance en {hkl} des vitesses de dégradation des microcristaux qui est justifiée à l’échelle moléculaire par l’affinité des radicaux pour les terminaisons chimiques exposées selon ces plans cristallographiques / Photocatalysis is widely used in a variety of applications in water and air purification. For those reasons, fundamentals research on the photocatalytical degradation processes of organic compounds on photocatalysts surfaces concern in most cases liquid and gaseous phases. The more recent development of self-cleaning surfaces has raised several issues concerning the mechanisms of photocatalytic degradation of solid deposits such as soot or fatty acids. These issues remain little addressed in the literature and therefore deserve further attention. This thesis work deals with the study of the photocatalytical degradation modes of solid deposits of stearic acid (SA) on the surface of titanium dioxide thin films. In this work, an original experimental approach based on the use of optical microscopy is implemented to monitor, on a microscopic scale, the SA deposits as a function of UV light exposure. Viewed under microscope, the SA deposits appear as microscopic islands presenting size and form distribution. On the basis of a new kinetic model we propose, the existing relationships between the degradation rate of the deposit and the initial size distribution of the islands population is demonstrated. The proposed kinetic model rationalizes our experimental results as well as several others from the literature. Additionally, an original study on the degradation of SA microcrystals, grown on microstructured TiO2 thin films, provides insight into the role of the photogenerated oxygenated radicals in the photocatalytical mechanisms. Furthermore, the anisotropy of the microcrystals structure is put in relation with that of the SA molecules orientations within the microcrystal. This explains the observed {hkl}-dependence of the degradation rate of the microcrystals