Composite materials are multifunctional materials having unique mechanical and physical properties that can be tailored to meet the requirements of a particular application. Aluminium based Metal Matrix Composites (MMC) always draw the attention of researchers due to its unique characteristics such as better strength to weight ratio, low wear rate and lower thermal expansion coefficient. There are various methods for manufacturing of MMC that can be grouped into two major categories: (a) Solid sate method such as powder metallurgy, co-extrusion and (b) Liquid state method such as stir casting. All of these methods for production of composites have their own advantages and disadvantages. Porosity, and poor wettabilty of dispersoids with matrix are few common problems in solid state route. Formations of undesirable phases, and segregation of dispersoids are common problems in liquid state processing route. Friction Stir Processing (FSP) technique, a derivative technique of Friction Stir Welding (FSW) has emerged as a major solid state technique to produce composites. However, there are several challenges associated with it. Most of the past work has been on limited volume of material. Researchers have tried to combine FSP technique with powder metallurgy technique to overcome aforementioned challenges associated with these techniques. Where on one hand, powder metallurgy ensures the uniform dispersion of dispersoids in the matrix, on the other hand FSP on sintered billet removes the pores and other defects. The combination of these two techniques leads to a more controlled and uniform properties. However, at the same time, it can be noted that the combination of these processes is tedious and time consuming. In this study, an attempt is made to achieve bulk dispersion of a second phase into an aluminium matrix using FSP technique. A 5 mm thickness composite is attempted in this work. To achieve this objective proper and uniform mixing of the particles is required. To achieve this, new tools and processing steps are to be designed and analyzed for a better understanding of material flow around the tool pin and the effect of different tool pin geometries on the material flow. Keeping this objective, a detailed study is carried out on material flow during FSW process using aluminium as base metal. A marker material technique is employed to understand the material flow. A strip of copper is selected as the marker material. Material flow can be qualitatively predicted during the process by observing the distribution of marker material in the weld nugget. Three different kinds of tools, each with an additional feature are designed for this purpose (a) Plain frustum shape pin (b) threaded frustum shape pin and, (c) Triflute pin . The material flow due to the plain pin tool can be considered as primary flow during the FSP. Three different kinds of flow zones are observed in the weld nugget in the case of plain tool. It is found that higher numbers of geometrical features (threads and flutes) not only enhance the material flow but also lead to the additional flow currents and more thorough and uniform mixing. A closer study of the weld nugget revealed that the copper marker particles and the matrix were diffusion bonded. Based on the reaction time available and temperature in the weld nugget a diffusion layer thickness of 4 nm is expected between copper and aluminium. However, the diffusion layer thickness was found to be 3.5 μm, which is nearly three orders of magnitude higher. This can be attributed to the enhancement of diffusion due to simultaneous application of strain and temperature. As copper is soluble in the aluminium, an insoluble marker material tin was used for study of flow in the weld nugget. However, the effect of insolubility and lower melting point had some unexpected effect on the processing loads. The normal load during steady state tool traverse in conventional butt-welding is found to be around 2.7 KN while it attains an average value of 14.7 KN when a thin strip of tin is sandwiched between these plates. However, a drop in the torque of around 13.12 NM is observed when tin was sandwiched between the plates as compared to the case when no insert was present. On closer examination of the flow behavior, it is seen that the tin melted, squeezed out and formed a lubricious layer between the tool and the work piece. This reduced the torque significantly and a concomitant drop in temperature was observed. The interaction between the tool and the colder aluminium work piece would thus result in much larger normal and transverse load Based on the expected and unexpected results of flow pattern in the weld nugget, a new FSP tool and processing steps were developed to manufacture MMC. Tungsten, which is the highest melting point metal is chosen as the dispersing phase. Further, as tungsten has high melting point, the kinetics of intermetallics formation would be low for the given FSP processing time at the processing temperature. This would lead to tungsten acting as a more ductile strengthening particle, which is expected to should give some unique characteristics to the MMC. Tungsten powder with an average diameter of 414 nm was dispersed in aluminum matrix with three different proportions after optimizing all the process parameters. It is noted that the mechanical properties are significantly influenced as the tungsten content in the matrix increases. In practice, MMC shows relatively low ductility compared to the parent metal. However in this case the composite exhibited even better ductility than the as received aluminium plates (rolled sheets). The composite showed around 129 MPa of yield strength along with 21% ductility when tungsten content is 3.8 at.%. It is also found that the reaction between aluminum and tungsten occurs during the processing and form the Al12W intermetallic phase. Though the formation of this intermetallic phase was unlikely due to the low temperature and short time available during the process, the reaction kinetics between aluminium and tungsten would have been enhanced due to the simultaneous application of strain and temperature. Given that the metal-metal, tungsten-aluminium composite produced by FSP had unique properties and also formed intermetallics, a study on incorporation of a highly insoluble material, graphite was carried out. Further graphite with its own unique properties and very low wettability with aluminium could possibly impart completely different properties to the system. Past work on graphite aluminium composites produced by other methods did not show promise. As FSP imposes high strains at relatively high flow stresses on the processed material, it was seen that the graphite got sheared to form multi-layer graphene composites with the aluminium. The graphene sheets are formed by mechanical exfoliation of graphite particles during its incorporation in the matrix. The formation of graphene was confirmed after separating the graphite from the processed zone and TEM studies of the composite. It is seen that most of the graphite got converted into multilayer graphene. This aluminium-graphene composite exhibited enhanced ductility and UTS. As received aluminium plates exhibited only 11% ductility and around 100 MPa of UTS while this composite exhibited around 26 % ductility and 147 MPa of UTS. However, there is only a slight improvement in yield strength of this composite.

Les multicouches périodiques ont trouvé de nombreuses applications dans les domaines de l’optique, de la mécanique ou encore de l’électronique. Néanmoins, peu d’études se concentrent sur les réponses électriques des structures métal/oxyde périodiques vis-à-vis de la température. L’intérêt de ces travaux s’est porté sur la caractérisation des systèmes produits et l’étude de leurs propriétés électriques en température. Dans les systèmes TiO/Ti/TiO/TiO2 et WO/W/WO/WO3 respectivement à base de titane et de tungstène élaborés par le procédé de gaz réactif pulsé, des modèles de structures sont établis grâce à la microscopie électronique en transmission pour des épaisseurs de sous-couches comprises entre 1,3 et 50,8 nm. Puis, cette étude met en lumière une modification des comportements électriques classiques des matériaux en température, ainsi que l’existence d’une relation empirique entre la variation de résistivité électrique et les structures multicouches périodiques métal/oxyde. Cette relation montre que la résistivité de ces structures multicouches métal/oxyde peut donc être prévue grâce à la corrélation entre les conditions opératoires et les structure produites. Une fois les limites de cette relation établies, ce manuscrit propose une ouverture vers une nouvelle nanostructuration périodique. Elle combine la technique de dépôt sous incidence oblique et la technique de gaz réactif pulsé afin de produire les premiers films composés de colonnes inclinées et d’alternances périodiques métal/oxyde. / Periodic multilayers have found many applications in the fields of optics, mechanics or electronics. However, few studies focus on the electrical responses of the metal/oxide periodic structures versus temperature. The interest of this work was focused on the characterization of the multilayers and their electrical properties versus temperature. In TiO/Ti/TiO/TiO2 and WO/W/WO/WO3 systems produced by the reactive gas pulsing process, sample structures were established by transmission electron microscopy for sublayers thicknesses between 1.3 and 50.8 nm. Then, this study highlights a modification of conventional electrical behavior versus temperature. An empirical relationship was established between the electrical resistivity variation and the metal/oxide periodic multilayer structures. The correlation between the operating conditions and the produced structure allows predicting the resistivity of these metal/oxide multilayer structures. Finally, this manuscript paves the way to a new periodic nanostructuration with the combined use of glancing angle deposition and gas reactive pulsing process to produce the first films composed by inclined columns and periodic metal/oxide alternations.

Abstract Exhaust gas emissions, e.g. nitrogen oxides (NOx), hydrocarbons (HCs) and carbon monoxide (CO), are harmful to human health and the environment. Catalysis is an efficient method to decrease these emissions. Unfortunately, the fuels and lubricant oils may contain chemical impurities that are also present in exhaust gases. Thus, catalytic materials with high activity and chemical resistance towards impurities are needed in the abatement of exhaust gas emission. In this thesis, the aim was to gain new knowledge about the effects of chemical impurities on the behaviour and activity of the catalysts. To find out these effects, the impurities existing in the exhaust gas particulate matter after combustion of biofuels and fossil fuels were analysed. The studied zeolite (ZSM-5), cerium-zirconium mixed oxides (CeZr and ZrCe) and silicon-zirconium oxide (SiZr) based catalysts were also treated with impurities to simulate the poisoning of the catalysts by, e.g. potassium, sodium, phosphorus and sulphur, using gas or liquid phase treatments. Several characterization techniques were applied to find out the effects of impurities on catalysts’ properties. The activity of catalysts was tested in laboratory-scale measurements in CO and HC oxidation and NOx reduction using ammonia (NH3) and hydrogen (H2) as reductants. The results revealed that the CeZr based catalysts had a high activity in NOx reduction by NH3 and moderate activity by H2. Sulphur was proven to enhance the activity of CeZr catalysts in NOx reduction. This is due to an increase in chemisorbed oxygen after the sulphur treatment on the catalyst surface. Instead, in HC and CO oxidation reactions, sulphur had a negligible impact on the activity of the SiZr based diesel oxidation catalyst. Thus, both CeZr and SiZr based catalysts can be utilized in exhaust gas purification when sulphur is present. ZSM-5 based catalysts were proven to be resistant to potassium and sodium. Alternatively, the activity of SiZr based catalysts decreased due to phosphorus. Thus, the removal of biomaterial-based impurities from the exhaust gases is needed to retain high catalyst activity in the exhaust gas after-treatment system. / Tiivistelmä Pakokaasupäästöissä olevat typen oksidit (NOx), hiilivedyt (HCs) ja hiilimonoksidi (CO) ovat haitallisia ihmisten terveydelle ja ympäristölle. Katalyysi on tehokas menetelmä vähentää näitä päästökomponentteja. Polttoaineet ja voiteluöljyt sisältävät epäpuhtauksia, jotka siirtyvät myös pakokaasuihin. Tästä johtuen pakokaasupäästöjen hallinnassa tarvitaan katalyyttimateriaaleja, joilla on hyvä vastustuskyky myrkyttymistä vastaan. Tavoitteena oli saada uutta tietoa kemiallisten epäpuhtauksien vaikutuksesta katalyyttien toimintaan. Biopolttoaineiden sisältämät mahdolliset epäpuhtaudet selvitettiin analysoimalla fossiilisen ja biopolttoaineen palamisessa muodostuvia partikkeleita ja vertaamalla niitä polttoaineiden hivenaineanalyysiin. Tutkimuksessa käytetyt zeoliitti (ZSM-5), cerium-zirkonium-sekaoksidi (CeZr) ja pii-zirkonium-oksidipohjaiset (SiZr) katalyytit käsiteltiin epäpuhtauksilla (kalium, natrium, fosfori ja rikki) kaasu- ja nestefaasissa. Tutkimuksessa käytettiin useita karakterisointitekniikoita, joiden avulla selvitettiin epäpuhtauksien vaikutuksia katalyyttien ominaisuuksiin. Katalyyttien toimintaa testattiin laboratoriomittakaavan kokeissa CO:n ja HC-yhdisteiden hapetuksessa sekä NOx:ien pelkistyksessä käyttäen ammoniakkia (NH3) tai vetyä (H2) pelkistimenä. Tulokset osoittavat, että CeZr-pohjaisten katalyyttien aktiivisuus NOx:ien pelkistyksessä oli hyvä käytettäessä pelkistimenä NH3:a ja kohtalainen käytettäessä vetyä. Rikki paransi CeZr-katalyyttien aktiivisuutta NOx:ien pelkistyksessä, mikä johtui kemiallisesti sitoutuneen hapen osuudesta katalyyttien pinnoilla. Vastaavasti hiilivetyjen ja CO:n hapetusreaktioissa rikki ei vaikuttanut SiZr-pohjaisten dieselhapetuskatalyyttien aktiivisuuteen. Sekä CeZr- ja SiZr-pohjaisia katalyytteja voidaan siten käyttää rikkiä sisältävien pakokaasujen puhdistuksessa. SiZr-pohjaisten katalyyttien aktiivisuus laski fosforin vuoksi. ZSM-5-pohjaiset katalyytit olivat vastustuskykyisiä kaliumille ja natriumille. Kestäviä katalyyttejä on siten kehitettävä, mikäli biopolttoaineiden sisältämien epäpuhtauksien poistaminen polttoaineista ei ole mahdollista.

L'objectif de ce travail était l'élaboration par ablation laser pulsé (PLD) et la caractérisation de couches minces d'oxydes dans le système K-Nb-O, et plus précisément d'une phase de structure bronze de tungstène quadratique (TTB) sous forme de nanorods, potentiellement intéressante dans le contexte de la recherche de nouveaux piézoélectriques sans plomb. Malgré une forte compétition de croissance entre les différentes phases, l'étude approfondie des conditions de dépôt a montré la possibilité d'obtenir les phases KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB) et KNbO3, en films minces après une phase d’optimisation essentielle. Nous avons déterminé l'influence des conditions de dépôt sur la formation et la nanostructuration de ces composés en couches minces. En particulier, il a été démontré que la température et la composition de la cible PLD avaient une forte influence sur la croissance de la phase de structure TTB. Une étude plus approfondie de ces phases a révélé que toutes avaient une morphologie spécifique liée à leur structure anisotrope, que nous avons pu contrôler par la croissance épitaxiale sur les substrats SrTiO3 orienté (100) et (110). L'existence d'une activité piézoélectrique dans des couches minces de la phase TTB, mise en évidence par PFM, lui confère un intérêt certain. Cette phase TTB a également été obtenue dans le système Na-K-Nb-O, très connu pour ses propriétés piézoélectriques et ferroélectriques, ouvrant la voie sur de nouvelles recherches. / The purpose of this work was the elaboration by pulsed laser deposition (PLD) and the characterization of thin films of oxides in the K-Nb-O system, and more precisely that of a tetragonal tungsten bronze phase (TTB) as nanorods, of potential interest as a new lead free piezoelectric. In spite of a strong growth competition between the different phases, the detailed study of the deposition conditions showed that it is possible to obtain KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB ) and KNbO3 in thin films form after an important optimization step. We have determined the influence of these deposition conditions on the formation and the nanostructuration of these compounds as thin films. In particular, it was shown that the temperature and the PLD target’s composition has a strong influence on the growth of the TTB structure. A further study of these phases revealed that all have a specific morphology related to their anisotropic structure, that we have controlled by the epitaxial growth on the (100) and (110) SrTiO3 substrates. The existence of a piezoelectric activity in the TTB thin films, evidenced by PFM, gives a great interest to this phase. This TTB phase was also obtained in the Na-K-Nb-O system, well known for its piezoelectric and ferroelectric properties, opening the way to new research.

La rationalisation des processus chimiques élémentaires aux surfacesest d'intérêt primordial pour de nombreux phénomènes naturels ou d'intérêttechnologique. D'un point de vue fondamental, la façon dont l'énergie, concomitanteà toute réaction chimique, est distribuée parmi les degrés de liberté des moléculesformées et/ou transférée à la surface est loin d'être systématisée. Dans ce travail,des simulations, reposant sur la méthode des trajectoires quasi-classiques (QCT),sont réalisées pour examiner cette problématique lors de recombinaisons demolécules d'hydrogène (H2) et d'azote (N2) résultant de l'abstraction d'atomesadsorbés via collision par un atome provenant de la phase gazeuse sur des surfacesde Tungstène - W(100) et W(110) - à taux de couverture non nul. Ces processussont ici étudiés pour leur intérêt en physique des interactions plasma-paroi. Dessurfaces d'énergie potentielle, construites à partir de calculs de structure électroniquebasés sur la théorie de la fonctionnelle densité (DFT), sont utilisées pour simuler,dans le cadre de la mécanique classique - incluant les corrections semi-classiquespertinentes - les processus ultrarapides dit de "Eley-Rideal" et par "atomes-chauds"(sub-picoseconde). La mise en place de modèle effectifs, pour tenir compte de ladissipation de l'énergie aux phonons de la surface et aux excitations électroniques(paires électron-trou), permet de rationaliser la dynamique non-adiabatique del'abstraction atomique aux surfaces métalliques. / The rationalization of elementary processes at surfaces is of prime importance for numerous natural and technological areas. From a fundamental pointof view, the way the energy concomitant to any chemical reaction is distributed among the desorbing molecules degrees-of-freedom and the surface is far frombeing fully pictured. In this work, quasiclassical molecular dynamics (QCT)simulations have been carried out to investigate this issue for the recombination ofH2 and N2 resulting from atomic adsorbate abstraction by atom scattering off theW(100) and W(110) covered surfaces, these processes being of relevance inplasma-wall interactions. Potential energy surfaces, built from density functional(DFT) theory calculations, have been used to simulate, within the framework ofclassical dynamics (including semi-classical corrections), the subpicosecond Eley-Rideal and Hot-Atom processes. The implementation of effective models to accountfor energy dissipation to surface phonons and electron-hole pair excitations, have allowed to rationalize the non-adidabatic dynamics of atom abstraction at metalsurfaces.

La fréquence des opérations de maintenance lors de l’excavation du sol par les tunneliers est problématique pour les entreprises de travaux publics. Ces opérations de maintenance engendrent des temps morts onéreux et nécessitent l'intervention d'opérateurs dans des conditions de travail hyperbares. Une des raisons aux nombreuses interventions humaines pour la maintenance est l’endommagement des outils racleurs du sol excavé (dents) qui sont placés sur la tête du tunnelier. Ces outils sont sujets à l’usure compte tenu de l’abrasivité des différents milieux qu’ils rencontrent. Le but de cette thèse est de contribuer à augmenter d’au moins 20% la durée de vie des matériaux constitutifs de ces outils, afin de réduire les différentes opérations de maintenance qui exposent les opérateurs à des risques importants. Pour atteindre cet objectif, les investigations menées dans ce travail ont porté sur plusieurs axes. Dans un premier temps, une expertise est menée pour identifier les modes d’endommagement prédominants sur les inserts à base de carbure de tungstène placés sur les dents ; ensuite, de nouveaux matériaux avec des propriétés mécaniques et des microstructures optimisées, développés dans le cadre du projet européen NeTTUN, sont caractérisés sur des bancs d’essais représentatifs. Ces essais ont permis de bien comprendre les mécanismes d’usure des nouveaux matériaux à base de carbure de tungstène. Les résultats de ce travail peuvent ensuite donner lieu à de nouvelles orientations en matière de choix de matériaux pour renforcer les dents de tunnelier. / The frequency of maintenance operations during the excavation of the ground by the tunnel boring machines (TBM) is problematic for civil engineering companies. These maintenance operations provoke expensive timeouts and they bring in excavation operators in risky hyperbaric work conditions. One of the reasons which leads to the numerous human interventions for the maintenance is the damage of drag bits located on the cutting wheel of the TBM. These drag bits undergo wear due to the abrasiveness of the various media they meet. The purpose of this thesis is to contribute to increase by 20 % at least the lifetime of the materials of the dag bits, in order to reduce the various maintenance operations which expose the operators to important risks. To achieve this goal, the investigations led in this work concerned several axes. At first, an expertise is led to identify the wear modes prevailing on the carbide inserts located on the drag bits; then, new materials with enhanced mechanical properties and optimized microstructures, developed in the framework of the European project NeTTUN, are characterized on representative lab testing devices. These tests allowed us to understand well the wear mechanisms of the newly developed grades of tungsten carbides. The results of this work can lead to new strategies for the selection of materials to reinforce the drag bits.

Microwave tubes are the choice of a wide range of high power and millimeter wave applications in radar, electronic warfare and communication systems. Advances in these devices are due to device innovation, improved modeling, and development of advanced materials. In a microwave tube, electron emitter is the source of electron beam and it is one of the vital components determining the life & performance of the device. High power, high frequency microwave tubes require electron emitters with high emission density. The present thesis aims at developing the materials for high emission density electron emitters. It is aimed to improve the emission density of thermionic cathodes for use in conventional microwave tubes and to develop cold emitters like ferroelectric cathodes for high power microwave devices. The work reported in the present thesis is a modest attempt of the author towards this aim. The thesis is organized in six chapters. Chapter 1 gives a brief introduction of thermionic and ferroelectric emitters. Different types of electron emission mechanisms and a brief background of thermionic and ferroelectricemitters are discussed in this chapter. The genesis of the problem taken up and its importance as well as the plan and scope of the work is also given in this chapter. In Chapter 2, the basic experimental techniques used in the present work are discussed. Preparation of mixed metal matrix and M- type dispenser cathodes and their characterization techniques has been discussed in this chapter. Subsequently, ferroelectric materials preparation and characterization for their material properties and electron emission has been discussed. A brief introduction to FEM software ANSYS, used for thermal analysis of dispenser cathodes and electrostatic field analysis of ferroelectric cathodes, has been given at the end of this chapter. Thermal analysis, development process, emission characterization, work function distribution, of W-Ir mixed metal matrix (MM type) cathodes and a simple innovative technique to estimate the barium evaporation rate from the emission data of the dispenser cathodes is presented in Chapter 3. Under normal microwave tube operating conditions, the cathode of the electron gun has to be heated up to 1050°C to obtain stable thermionic electron emission. Thermal analysis is a first step in the development process of cathodes, optimizing its structure for improved performance with respect to its operating power, warm-up time and efficiency. Thermal analysis of a dispenser cathode in electron gun environment using the FEM software ANSYS and its experimental validation are presented. Development of porous W-Ir mixed metal matrix material required for dispenser cathode applications has been discussed. Determination of pore size, pore density and pore uniformity has been carried out. The performance of the cathodes made with these pellets is at par with the results reported in the literature. The surface of mixed metal pellet is an inherently two-phase structure consisting of tungsten solid solution phase and W-Ir ε phase causing more spread in the spatial distribution of work function. W-Ir mixed metal matrix cathodes have been realized and their work function distribution has been determined form the measured I-V characteristics. Also in this chapter, a novel technique for estimation of barium evaporation rate for dispenser cathodes from their I-V characteristics is presented. Results of life test carried out on these cathodes are given at the end of the chapter. In Chapter 4, work carried out on enhancing the emission properties of mixed metal matrix cathodes by suitably modifying the impregnant mix is discussed. W-Ir MM type cathodes discussed in the previous chapter give a emission current density of ~ 7.5A/cm2 with a work function of 1.99 eV. Thesevalues are very close to that of B-type cathode. In this chapter, it is explored to suitably dope the 5BaO:3CaO:2Al2O3 impregnant mix to reduce the work function of W-Ir cathodes. Lithium and Scandium oxides have been added to the 5:3:2 imp regnant mix. Lithium oxide doped impregnated MM type cathodes have given more than 30 A/cm2 current density at 1050oC. For scandium oxide doped MM type cathodes current density has increased to 15 A/cm2 at the same temperature. In Chapter 5, Electron emission from the ferroelectric cathodes has been discussed. FEM simulation of Ferroelectric cathodes to study the electrical excitation effects on emission. Triple point electric field in FE Cathodes is very large and can lead to field emission from the metallic grid at triple points. FEM simulation has been carried out to find out the effect of grid thickness on triple junction electric field using ANSYS software. From FEM modeling it is also seen that if a dielectric layer of lower dielectric constant (εr≤10) is placed between the grid and the ferroelectric material the triple junction electric field increases three fold. Use of dielectric layer can also reduce the secondary electron coefficient (δ) and surface plasma generation. Lanthanum doped PZT has been chosen for the study and these materials have been tested in diode configuration for emission characterization in demountable vacuum systems. Repeatable electron emission has been achieved for all the three compositions of PLZT (x/65/35) material (x = 7, 8, 9). However, it has been observed that when the ferroelectric is subjected to repetitive unipolar electrical excitation, fatigue is set in and cathode material is cracking. To study the effect of domain switching on the residual stress in the ferroelectric material, XRD studies have been carried out. Shift in XRD peaks for fresh and emission tested samples has been used to calculate the residual stress developed in the samples. Details of High current switch realized using ferroelectric cathodes have been discussed. Chapter 6 gives the Summary of the work done and suggestions for further research on W-Ir mixed metal matrix cathodes and ferroelectric cathodes.

Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.

This diploma thesis focuses on electrochemical sensors to detect radiation in the blue region of the visible spectrum. As a semiconducting material for the manufacture of the sensor, a suspension of tungsten trioxide was found. The individual elements of the sensor were applied by pad printing techniques or screen printing. Using linear voltammetry and chronoamperometry, the magnitude of the generated current was measured and radiometric calibration was performed. The properties of the layers were characterized by profilometry, optical and electron microscopy.

The thesis deals with study of thin layers of transition metal dichalcogenides, especially of molybdenum disulfide. Nanostructures were fabricated on two-dimensional crystals of MoS2 and WSe2. Within followed analysis attention was paid to the photoluminescence properties. In the thesis transition metal dichalcogenides are reviewed and description of the modified process of preparation by micromechanical exfoliation is given.