Nous avons étudié la croissance de films organiques de pérylène tetracarboxylique diimide (PTCDI) et de phthalocyanine de palladium (Pd(Pc)) sur les surfaces métalliques Pt(001), Pt(111) et Au(001). Une étude de l'hétérostructure Au/PTCDI/Pd(Pc)/Au ayant précédemment conclu à un effet redresseur, nous nous sommes plus particulièrement intéressés à la réalisation de cette hétérostructure pour des épaisseurs nanométriques par dépôt en phase vapeur sous ultravide, ainsi qu'à sa caractérisation par différentes techniques d'analyse des surfaces (AES, LEED, REELS, UHV-STM et STS). Il était important de réaliser des couches organiques ordonnées afin d'optimiser le transport de charges dans ces couches.<br /> A l'aide des cinétiques de dépôt réalisées par spectroscopie d'électrons Auger (AES) et de la microscopie à effet tunnel (STM), nous avons identifié les modes de croissance des deux types de molécule en films minces. Nous montrons que PTCDI et Pd(Pc), déposés sur un substrat de platine (Pt(111) et Pt(001)) à différentes températures, croissent suivant le mode Stransky-Krastanov : après la formation d'une première couche désordonnée, les molécules se regroupent dans des îlots cristallins. Les propriétés électroniques de films moléculaires de différentes épaisseurs déposés sur Pt(001) ont pu être déduites par spectroscopie de pertes d'énergie d'électrons lents en mode réflexion (REELS) montrant une lente ouverture du gap. Nous observons la formation de monocouches désordonnées en raison d'une forte interaction molécule-platine comparativement à l'interaction molécule-molécule. Ce résultat étant en opposition avec notre critère initial d'obtention de couches ultraminces ordonnées, nous nous sommes donc intéressés au substrat Au(001). Dans ce cas, il a été démontré que les couches déposées donnent généralement des surstructures organisées.<br />Nous avons utilisés les vitesses de dépôt précédemment déterminées dans le cadre des dépôt sur platine afin d'étudier par AES et STM les monocouches de PTCDI et Pd(Pc) sur la face (001) de l'or. La monocouche de Pd(Pc) déposée à température ambiante s'ordonne en fonction de la quantité adsorbée en une maille carrée ou rectangulaire, orientée suivant les directions <110> et < 10> du substrat. Le film de PTCDI forme une maille rectangulaire dont les paramètres sont proches de ceux obtenus par diffraction des rayons X sur des monocristaux de PTCDI.<br /> Finalement, le dépôt d'une fraction de monocouche de PTCDI sur la surstructure carrée de Pd(Pc) adsorbée sur Au(001) conduit à la formation d'une maille de PTCDI commensurable avec la maille de Pd(Pc). Les courbes I-V obtenues par STS pour le système W / PTCDI / Pd(Pc) / Au(100) sont semblables à une caractéristique de diode (coefficient redresseur compris entre 13 et 24), mais l'origine de cet effet reste pour le moment à déterminer.

In this thesis, two recently discovered polymorphs of LiFeSO4F, adopting a tavorite- and triplite-type structure, were investigated as potential candidates for use as cathode materials in Li-ion batteries. The studies aimed at enriching the fundamental understanding of the synthetic preparations, structural properties, and electrochemical functionality of these materials. By in situ synchrotron X-ray diffraction (XRD), the formation mechanism of the tavorite-type LiFeSO4F was followed starting from two different sets of precursors, FeSO4∙H2O + LiF, and Li2SO4 + FeF2. The results indicated that the formation of LiFeSO4F is possible only through the structurally related FeSO4∙H2O, in line with the generally recognized topotactic reaction mechanism. Moreover, an in-house solvothermal preparation of this polymorph was optimized with the combined use of XRD and Mössbauer spectroscopy (MS) to render phase pure and well-ordered samples. Additionally, the triplite-type LiFeSO4F was prepared using a facile high-energy ball milling procedure. The electrochemical performance of as-prepared tavorite LiFeSO4F was found to be severely restricted due to residual traces of the reaction medium (tetraethylene glycol (TEG)) on the surface of the synthesized particles. A significantly enhanced performance could be achieved by removing the TEG residues by thorough washing, and a subsequent application of an electronically conducting surface coating of p-doped PEDOT. The conducting polymer layer assisted the formation of a percolating network for efficient electron transport throughout the electrode, resulting in optimal redox behavior with low polarization and high capacity. In the preparation of cast electrodes suitable for use in commercial cells, reducing the electrode porosity was found to be a key parameter to obtain high-quality electrochemical performance. The triplite-type LiFeSO4F showed similar improvements upon PEDOT coating as the tavorite-type polymorph, but with lower capacity and less stable long-term cycling due to intrinsically sluggish kinetics and unfavorable particle morphology. Finally, the Li+-insertion/extraction process in tavorite LiFeSO4F was investigated. By thorough ex situ characterization of chemically and electrochemically prepared LixFeSO4F compositions (0≤x≤1), the formation of an intermediate phase, Li1/2FeSO4F, was identified for the first time. These findings helped redefine the (de)lithiation mechanism which occurs through two subsequent biphasic reactions, in contrast to a previously established single biphasic process.

Pagrindinis disertacijos tikslas – optinio ZnMgRE (RE = Y, Ho, Er) kvazikristalų atsako tyrimais atskleisti jų elektroninės posistemės ypatumus. Disertaciją sudaro eksperimentiniai rentgeno-difrakciniai (XRD) ir optiniai spektroskopiniai tyrimai, kvazikristalų elektroninės posistemės modelio konstravimas ir teorinis jų optinio atsako aprašymas. Atliktais eksperimentiniais XRD tyrimais buvo siekiama atskleisti kvazikristalų atvirkštinės gardelės vektorius, apibrėžiančius potencinį kvazikristalinį lauką, veikiantį į elektroninę posistemę. Optiniai spektroskopiniai tyrimai buvo atlikti kombinuotu spektroskopinės elipsometrijos ir atspindžio spektroskopijos metodu, paremtu darbe pasiūlyta inkaro lango duomenų analizės schema. Naudotas spektroskopinių tyrimų metodas įgalino atskleisti patikimus ZnMgRE optinio laidumo spektrus plačioje, 0.01 – 6 eV, spektrinėje srityje. Darbe išplėstas ZnMgRE elektronų posistemės modelis, kuris anksčiau buvo pasiūlytas kvazikristalų fotoemisinio atsako analizei. Nepriklausomų Fermi paviršiaus sankirtų su Bragg’ų plokštumomis schema formuluota išplėstiniame juostiniame atvaizdavime. Teorinė optinio laidumo skaičiavimų schema, anksčiau pasiūlyta kristalinių junginių optinio laidumo skaičiavimams, šiame darbe išplėsta įskaitant įvairias Fermi lygmens padėtis pseudotarpo atžvilgiu. Teoriniai ZnMgRE optinio laidumo skaičiavimai, atlikti darbe pasiūlyto elektroninės posistemės modelio rėmuose, detaliai atkartoja eksperimentinius optinio laidumo spektrus... [toliau žr. visą tekstą] / The main goal of the dissertation was to reveal the electronic structure of ZnMgRE (RE = Y, Ho, Er) quasicrystals by investigations of their optical response. The thesis comprises experimental X-ray diffraction (XRD) and optical spectroscopy studies of the quasicrystals, a construction of their electron subsystem model, and a theoretical description of their optical response. The XRD studies were carried out to determine the reciprocal quasicrystalline lattice vectors, which define the atomic potential field acting on an electron subsystem. The optical spectroscopy studies were carried out by the combined spectroscopic ellipsometry and reflectance spectroscopy technique, based on a suggested anchor-window method. High-accuracy ZnMgRE optical conductivity spectra were recorded in the wide, 0.01 – 6 eV, spectral range. The model of ZnMgRE electron energy spectrum, previously suggested for an interpretation of experimental ZnMgRE photoemission spectra, was developed. The nearly-free-electron gas model of independent intersections was formulated in the extended zone presentation. A scheme of the theoretical optical conductivity calculations was extended to account for various positions of the Fermi level with respect to a pseudogap. The experimental ZnMgRE optical conductivity spectra can be reproduced in detail by theoretical calculations performed within the framework of the suggested electron energy spectrum model. The set of the electron energy spectrum parameters determined... [to full text]

The main goal of the dissertation was to reveal the electronic structure of ZnMgRE (RE = Y, Ho, Er) quasicrystals by investigations of their optical response. The thesis comprises experimental X-ray diffraction (XRD) and optical spectroscopy studies of the quasicrystals, a construction of their electron subsystem model, and a theoretical description of their optical response. The XRD studies were carried out to determine the reciprocal quasicrystalline lattice vectors, which define the atomic potential field acting on an electron subsystem. The optical spectroscopy studies were carried out by the combined spectroscopic ellipsometry and reflectance spectroscopy technique, based on a suggested anchor-window method. High-accuracy ZnMgRE optical conductivity spectra were recorded in the wide, 0.01 – 6 eV, spectral range. The model of ZnMgRE electron energy spectrum, previously suggested for an interpretation of experimental ZnMgRE photoemission spectra, was developed. The nearly-free-electron gas model of independent intersections was formulated in the extended zone presentation. A scheme of the theoretical optical conductivity calculations was extended to account for various positions of the Fermi level with respect to a pseudogap. The experimental ZnMgRE optical conductivity spectra can be reproduced in detail by theoretical calculations performed within the framework of the suggested electron energy spectrum model. The set of the electron energy spectrum parameters determined... [to full text] / Pagrindinis disertacijos tikslas – optinio ZnMgRE (RE = Y, Ho, Er) kvazikristalų atsako tyrimais atskleisti jų elektroninės posistemės ypatumus. Disertaciją sudaro eksperimentiniai rentgeno-difrakciniai (XRD) ir optiniai spektroskopiniai tyrimai, kvazikristalų elektroninės posistemės modelio konstravimas ir teorinis jų optinio atsako aprašymas. Atliktais eksperimentiniais XRD tyrimais buvo siekiama atskleisti kvazikristalų atvirkštinės gardelės vektorius, apibrėžiančius potencinį kvazikristalinį lauką, veikiantį į elektroninę posistemę. Optiniai spektroskopiniai tyrimai buvo atlikti kombinuotu spektroskopinės elipsometrijos ir atspindžio spektroskopijos metodu, paremtu darbe pasiūlyta inkaro lango duomenų analizės schema. Naudotas spektroskopinių tyrimų metodas įgalino atskleisti patikimus ZnMgRE optinio laidumo spektrus plačioje, 0.01 – 6 eV, spektrinėje srityje. Darbe išplėstas ZnMgRE elektronų posistemės modelis, kuris anksčiau buvo pasiūlytas kvazikristalų fotoemisinio atsako analizei. Nepriklausomų Fermi paviršiaus sankirtų su Bragg’ų plokštumomis schema formuluota išplėstiniame juostiniame atvaizdavime. Teorinė optinio laidumo skaičiavimų schema, anksčiau pasiūlyta kristalinių junginių optinio laidumo skaičiavimams, šiame darbe išplėsta įskaitant įvairias Fermi lygmens padėtis pseudotarpo atžvilgiu. Teoriniai ZnMgRE optinio laidumo skaičiavimai, atlikti darbe pasiūlyto elektroninės posistemės modelio rėmuose, detaliai atkartoja eksperimentinius optinio laidumo spektrus... [toliau žr. visą tekstą]

Matériaux multiferroïques ont suscité beaucoup d'intérêt au cours des dernières années. Notre étude est consacrée à un système prototype: manganite d'yttrium. En particulier, nous nous concentrons sur les propriétés ferroélectriques sous forme massive monocristalline et sous forme de couches minces. Manganite d'yttrium appartient à la classe des composés ABO3. La plupart des études théoriques de la ferroélectricité à ce jour se sont concentrées sur perovskite cubique ABO3. Manganite d'yttrium est hexagonale et est un ferroélectrique impropre. Nous nous sommes intéressés à étudier théoriquement et expérimentalement comment ces deux fonctions se comportent sous forme de film mince.

Summary Serpentinites from the northern Vermont were examined for the distribution and abundance of As. XRD and electron microprobe showed the samples are composed of antigorite, chromite, magnetite, and carbonate minerals (magnesite, dolomite, calcite). The concentration in As when the samples were dissolved in H3PO4 was 10% of the concentration in As when the samples were dissolved in concentrated HF/HNO3, suggesting that As is mainly incorporated in the structure of antigorite. X-ray absorption near-edge structure spectra showed that the As is As(III) in the samples. Extended X-ray absorption fine structure spectra suggested that the As has a tetrahedral coordination and is located in the Si-site in serpentine.

Electrical and structural properties of Bismuth thin films were studied simultaneously. Electrical properties of the Bismuth thin films have been characterized by measuring temperature dependent conductivity and Hall effect. Structural analysis were carried out by X-ray diffraction technique and using a room temperature Atomic Force Microscope (RT-AFM).

Cutting tools are subject to extreme environment during processing, with hightemperatures and pressures. CVD coatings are used to increase lifetime andperformance of the WC/Co composite. Residual stresses in the coatings areinteresting as they may be destructive or constructive for the material duringoperation. Blasting is used to change the as-deposited tensile stress to compressive.The usefulness of X-ray diffraction (XRD) and nanobeam diffraction (NBD) forcharacterization of strains in the different coating layers has been investigated. XRDwith different anode materials has been used to determine the macrostress in thelayers and an attempt was done to calculate the average microstrain and crystallitesize. NBD was used to study the microstrain within single grains of the differentmaterials. A specimen preparation method has been developed for the studiedsamples using the FIB.The XRD analysis shows that the measurement condition is of great importanceduring stress measurements. The macrostress of the different samples show that theZrCN type coating is less stressed than the TiCN type coating after deposition. It isalso shown that the ZrCN type coating is less affected by the blasting. Determinationof microstrain and crystallite size from XRD needs further development.The NBD is a good method to evaluate microstrain within single grains, or betweengrains oriented in the same zone axis. The analyses show more strain within thegrains after blasting. The measurements indicate more strain variation in the Al2O3layer in the TiCN system compared to the ZrCN system.

Title: Characterization of highly porous Pd-modified SnO2 sputtered thin films for H2 detection Autor: Mgr. Mykhailo Chundak Department/Institute: Department of Surface and Plasma Science Supervisor of the doctoral thesis: RNDr. Kateřina Veltruská, CSc., Department of Surface and Plasma Science Abstract: This doctoral thesis contains the study of tin dioxide and Pd-doped tin dioxide samples deposited by magnetron sputtering utilizing glancing angle deposition (GLAD). Influence of the deposition parameters on the change of morphology, crystalline structure and chemical state was studied. The samples were characterized by a variety of techniques, such as: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), synchrotron radiation photoelectron spectroscopy (SRPES), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Prepared samples showed high porosity which could be controlled by deposition parameters (angle of the deposition, gas pressure and power of magnetron discharge). Highly porous SnO2 GLAD samples and Pd modified SnO2 GLAD samples were deposited on the substrates at room temperature and 300 řC. These samples were found to be polycrystalline with certain fraction of amorphous contribution, given by preparation conditions. The size of the...

Recrystallisation is an important topic in the metal industry since the process may drastically alter the properties of the materials subjected to it. By controlling the recrystallisation process, the material properties can be adjusted as desired, which could lead to stronger materials and hence lighter constructions, decreasing our material consumption. This is currently regulated using softening curves complied from tensile tests, a method which does not show the degree of recrystallisation of a metal. This thesis work therefore explores the possibility to characterise the recrystallisation process using in situ X-ray diffraction, XRD, during heating.The method proposed is using in situ heat treatments of aluminium samples combined with XRD measurements. The results show that it is possible to follow the recrystallisation process of rolled aluminium alloy AA3003 by using in situ XRD during heating, a discovery that could facilitate development and understanding of new materials. Nevertheless, further investigations of the subject is required before the method will be profitable. / Rekristallisation är ett viktigt ämne inom metallindustrin, detta eftersom materialegenskaper drastiskt kan förändras under rekristallisationsprocessen. Genom att kontrollera rekristallisationsprocessen kan materialegenskaper skräddarsys efter applikation. Även starkare material kan tillverkas och därav kan lättare strukturer konstrueras och på så vis minskar även materialåtgången. Idag regleras rekristallisation med hjälp av mjukningskurvor sammanställda genom dragprov, en metod som inte kan visa rekristallisationsgraden av en metall. Detta examensarbete utforskar möjligheten att karaktärisera rekristallisationsprocessen genom att använda in situ röntgendiffraktion, XRD, under värmningsprocessen.Den framtagna metoden inkluderar in situ värmebehandlingar av aluminiumprover i kombination med XRD-mätningar. De erhållna resultaten från experimenten visar på att det är fullt möjligt att följa rekristallisationsprocessen av aluminiumlegering AA3003 med in situ XRD, en upptäckt som kan komma att underlätta vid utveckling och förståelse av legeringar och nya material. Dock krävs fortsatta studier i ämnet innan metoden kan anses vara lönsam.