O níquel desempenha um papel importante na catálise como uma alternativa ao uso de metais nobres; no entanto, a preparação de nanopartículas de níquel com o tamanho e composição bem controlados não é uma tarefa fácil. O trabalho descrito nessa dissertação compreende a preparação e caracterização de um novo catalisador heterogêneo cotendo nanopartículas de níquel e o estudo da atividade catalítica em reações de hidrogenação em fase gososa e líquida. O catalisador foi preparado por pulverização catódica (magnetron sputtering deposition), que permitiu a deposição de nanopartículas com diâmetro médio de 2,5 ± 0,3 nm sobre um suporte de sílica, sem a utilização de solventes ou estabilizantes. Diferentes tempos de pulverização catódica permitiram a obtenção de catalisadores com diferentes concentrações de metal sobre o suporte. O catalisador preparado foi caracterizado por microscopia eletrônica de transmissão (MET), difração de raios X (DRX), espectroscopia de fotoéletrons excitados por raios X (XPS) e espectroscopia de absorção de raios X (XAS). As análises por técnicas de raios X mostraram que o catalisador oxida parcialmente sua superfície após ser exposto ao ar ambiente. Utilizando XAS, foi possível mostrar que o catalisador como preparado possui 61% de níquel metálico e 39% de níquel óxido. O catalisador exposto ao ar por um ano ainda apresentava 49% de níquel metálico. O desempenho dos catalisadores foi estudado na reação modelo de hidrogenação de cicloexeno, utilizando hidrogênio molecular como agente redutor. Para a hidrogenação em fase líquida, o catalisador não se mostrou ativo nas condições estudadas e não pode ser ativado mesmo após pré-tratamento com hidrogênio molecular. Já na hidrogenação em fase gasosa, o catalisador apresentou atividade catalítica, sendo mais ativo quando submetido a um processo de ativação com fluxo de hidrogênio e aquecimento até 200 ºC. O catalisador perde atividade ao ser utilizado por um longo período ou utilizado em sucessivos ciclos de aquecimento em condições reacionais, mas a atividade pode ser recuperada quando o catalisador é tratado termicamente sob fluxo de hidrogênio. / Nickel plays an important role in catalysis as an affordable alternative for noble metals; however, it is one of the most difficult metal nanoparticles to prepare with well-controlled size and composition. This master thesis comprises the development and characterization of a new heterogeneous catalyst containing nickel nanoparticles and the catalytic studies for hydrogenation reactions in liquid and gas phase. The catalyst was prepared by magnetron sputtering deposition, allowing the deposition of nanoparticles of 2.5 ± 0.3 nm on silica, without using solvents and stabilizers. Different sputtering times allowed the preparation of catalysts with different loading of metal on silica. The catalyst prepared has been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The analysis by X-ray techniques revealed that the catalyst partially oxidize its surface after being exposed to ambient air. By XAS technique, it was possible to show that the catalyst as prepared has 61% of metallic nickel and 39% of nickel oxide. The as prepared catalyst was exposed to air for a year still contains 49% of metallic nickel. The performance of the catalyst was studied in cyclohexene hydrogenation model reaction, using molecular hydrogen as reducing agent. The catalyst was not active for the liquid phase hydrogenation under the studied conditions, and could not be activated by a pre-treatment with hydrogen. In the gas phase hydrogenation, the catalyst showed catalytic activity being more active when submitted to an activation process with hydrogen flow and heating to 200 ºC. The catalyst loses activity when used for a long time on stream or used in consecutive heating cycles under reaction conditions, but the activity can be regenerated when the catalyst is heat-treated under hydrogen flow.

O níquel desempenha um papel importante na catálise como uma alternativa ao uso de metais nobres; no entanto, a preparação de nanopartículas de níquel com o tamanho e composição bem controlados não é uma tarefa fácil. O trabalho descrito nessa dissertação compreende a preparação e caracterização de um novo catalisador heterogêneo cotendo nanopartículas de níquel e o estudo da atividade catalítica em reações de hidrogenação em fase gososa e líquida. O catalisador foi preparado por pulverização catódica (magnetron sputtering deposition), que permitiu a deposição de nanopartículas com diâmetro médio de 2,5 ± 0,3 nm sobre um suporte de sílica, sem a utilização de solventes ou estabilizantes. Diferentes tempos de pulverização catódica permitiram a obtenção de catalisadores com diferentes concentrações de metal sobre o suporte. O catalisador preparado foi caracterizado por microscopia eletrônica de transmissão (MET), difração de raios X (DRX), espectroscopia de fotoéletrons excitados por raios X (XPS) e espectroscopia de absorção de raios X (XAS). As análises por técnicas de raios X mostraram que o catalisador oxida parcialmente sua superfície após ser exposto ao ar ambiente. Utilizando XAS, foi possível mostrar que o catalisador como preparado possui 61% de níquel metálico e 39% de níquel óxido. O catalisador exposto ao ar por um ano ainda apresentava 49% de níquel metálico. O desempenho dos catalisadores foi estudado na reação modelo de hidrogenação de cicloexeno, utilizando hidrogênio molecular como agente redutor. Para a hidrogenação em fase líquida, o catalisador não se mostrou ativo nas condições estudadas e não pode ser ativado mesmo após pré-tratamento com hidrogênio molecular. Já na hidrogenação em fase gasosa, o catalisador apresentou atividade catalítica, sendo mais ativo quando submetido a um processo de ativação com fluxo de hidrogênio e aquecimento até 200 ºC. O catalisador perde atividade ao ser utilizado por um longo período ou utilizado em sucessivos ciclos de aquecimento em condições reacionais, mas a atividade pode ser recuperada quando o catalisador é tratado termicamente sob fluxo de hidrogênio. / Nickel plays an important role in catalysis as an affordable alternative for noble metals; however, it is one of the most difficult metal nanoparticles to prepare with well-controlled size and composition. This master thesis comprises the development and characterization of a new heterogeneous catalyst containing nickel nanoparticles and the catalytic studies for hydrogenation reactions in liquid and gas phase. The catalyst was prepared by magnetron sputtering deposition, allowing the deposition of nanoparticles of 2.5 ± 0.3 nm on silica, without using solvents and stabilizers. Different sputtering times allowed the preparation of catalysts with different loading of metal on silica. The catalyst prepared has been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The analysis by X-ray techniques revealed that the catalyst partially oxidize its surface after being exposed to ambient air. By XAS technique, it was possible to show that the catalyst as prepared has 61% of metallic nickel and 39% of nickel oxide. The as prepared catalyst was exposed to air for a year still contains 49% of metallic nickel. The performance of the catalyst was studied in cyclohexene hydrogenation model reaction, using molecular hydrogen as reducing agent. The catalyst was not active for the liquid phase hydrogenation under the studied conditions, and could not be activated by a pre-treatment with hydrogen. In the gas phase hydrogenation, the catalyst showed catalytic activity being more active when submitted to an activation process with hydrogen flow and heating to 200 ºC. The catalyst loses activity when used for a long time on stream or used in consecutive heating cycles under reaction conditions, but the activity can be regenerated when the catalyst is heat-treated under hydrogen flow.

Les TCOs (Transparent Conductive Oxide) trouvent des applications dans de nombreux domaines s'étendant del'électrochromie au photovoltaique en passant par l'opto-électronique. Parmi les matériaux historiques, les TCOs detype n font l'objet d'une littérature abondante tandis que les TCO de type p sont quant à eux étudiés de façon plusconfidentielle mais commencent à susciter un engouement, notamment dans l'objectif de jonctions p-ntransparentes.Sur la base de la théorie de la méthode de modulation chimique de bande de valence, le composé CuCrO2 destructure délafossite est considéré comme un candidat intéressant de TCO de type p. L'objectif de ces travaux estd'élaborer des films minces à base de CuCrO2 avec une transmittance optique acceptable et une conductivitéélectrique de type p élevée afin de envisager la possibilité de fabrication des jonctions p-n transparents pourdiverses applications.Dans ce travail, les films CuCrO2 ont été déposés par co pulvérisation cathodique magnétron en condition réactiveà partir de cibles métalliques. Une substitution partielle de Cr par Mg a ensuite été effectuée et l'influence del'épaisseur du film CuCrO2 :Mg sur ses propriétés optoélectroniques a été étudiée. Enfin, des revêtementsd'architecture sandwich CuCrO2 :Mg/Ag/CuCrO2 :Mg ont été élaborés en faisant varier le temps de dépôt de lacouche intermédiaire d'argent afin d'améliorer les performances optoélectroniques des films. / Transparent conductive oxides (TCOs) can be widely used in various domains from electrochromics to photovoltaicsowing to their unique optoelectronic properties. During the history of the development of TCOs, most attention hasbeen focused on n-type TCOs, while p-type TCOs have made slow progress. Recently, the studies on p-type TCOsraised many interest especially due to their potential application in the fabrication of transparent p-n junctions.Based on the theory of chemical method of valance band, CuCrO2 compound with delafossite structure isconsidered as an interesting candidate for p-type TCOs. The objective of this work is to synthesize CuCrO2-basedthin films with acceptable optical transmittance and high p-type electrical conductivity in order to explore thepossibility of fabrication of transparent p-n junctions for various applications.In this work, CuCrO2 films were deposited by reactive sputtering from metallic targets. Then, partial Cr substitutionby Mg was performed into CuCrO2 films and the influence of the films thickness on its optoelectronic properties wasstudied. Finally, sandwich architectural coatings of CuCrO2 :Mg/Ag/CuCrO2 :Mg were designed in order to improvethe films optoelectronic performances.

Les zirconates titanates de plomb (PZT) suscitent un intérêt considérable pour plusieurs applications industrielles, au regard de leurs excellentes propriétés piézoélectriques et électromécaniques. Le contexte actuel de l’innovation technologique est la miniaturisation et l’allègement des produits ; c’est pour cette raison que de nombreuses études sont menées depuis une vingtaine d’années sur les techniques et les procédés de synthèse de ces matériaux piézoélectriques sous forme de couches minces tout en garantissant une fiabilité accrue. Dans ce contexte, l’étude menée dans le cadre de cette thèse, a visé l’optimisation du procédé d’élaboration de films minces piézoélectriques de PZT par pulvérisation cathodique magnétron en mode DC et en mode Rf, en vue d’obtenir des capteurs d’efforts piézoélectriques. La synthèse in situ et la cristallisation ex-situ des films élaborés, par recuit classique (CFA) ou recuit rapide (RTA) confirme une structure pérovskite du PZT, complétées par une série de caractérisations morphologiques et structurales. Les domaines ferroélectriques à l’origine des propriétés piézoélectriques sont correctement visualisés par PFM et le calcul du coefficient piézoélectrique d33 des couches synthétisées sur des substrats métalliques, est réalisé par interféromètre laser. En parallèle, une approche expérimentale est menée sur l’évolution des performances piézoélectriques des films de PZT d’une part en fonction du mode d’élaboration et d’autre part en fonction de la texturation des couches, assurée par des traitements thermiques de cristallisation. / Recently, PZTs thin films have been spotlighted for various applications owing to their excellent piezoelectric and electromechanical properties. Most of the existing coating methods have been explored for the deposition of PZT. In this work, amorphous Pb(ZrxTi1-x)O3 (PZT) thin films were prepared by pulsed DC and RF magnetron sputtering in order to device a piezoelectric force sensors. The structure of a perovskite phase of PZT thin films was successfully characterized and morphological characterizations were investigated. Ferroelectrics properties of PZT thin films were determined using Piezoresponse Force Atomic technique (PFM) while the functional response of the films was characterized by measurements of piezoelectric d33 coefficients. Additionally, the coating processes and the crystallization behavior at different temperatures, of amorphous PZT thin films during either conventional furnace annealing (CFA) or rapid thermal annealing (RTA) were studied to understand the evolution of piezoelectric properties of films.

<p>The aim of this thesis was to develop wear resistant physical vapour deposited coatings of TiB₂ as well as multilayers of Cr/CrN. The correlation between deposition parameters and fundamental coating properties such as microstructure, composition, residual stress and hardness has been investigated. Finally, the influence of these properties on the coating behaviour in tribological applications has been evaluated.</p><p>It is shown that the use of electron bombardment of the growing coating during d.c. magnetron sputtering is beneficial for the growth of superhard TiB₂ coatings. Furthermore, electron bombardment results in TiB₂ coatings with significantly lower residual stresses than coatings deposited using ion bombardment. The low stresses in these coatings open up the possibility to deposit thicker PVD coatings, as confirmed in this thesis.</p><p>In addition, the use of TiB₂ coatings in tribological contacts against aluminium proved to be superior to many other commercial coatings used today, with respect to wear resistance, anti galling properties and a low friction.</p><p>Finally, a model is proposed which explains the observation that the abrasive wear resistance of multilayered Cr/CrN coatings can outperform that of the individual constituents. The model was found to satisfactory predict experimental data.</p>

<p>Spectrally selective solar absorber using composite Ni-NiO as coating materials was studied. Samples were prepared by dc magnetron sputtering unit named <i>Rulle</i>, which is a miniature copy of an industrial roll-coater unit. Using asymmetric location of the oxygen nozzele, it is possible to form the desired metallic concentration distribution along the sputtering zone under optimized conditions. This distribution can be transferred into a graded film profile by moving the substrate, obtaining good spectral selectivity. For specified mechanical settings (such as locations of gas sprays, target and pump positions etc.), the ratio of used oxygen flow to the corresponding critical oxygen flow, <b>RO</b>, is a dimensionless parameter to control the zone specification. The optimal value is around 0.80 for the <i>Rulle</i>. Optimized zone shows properties with two main parts: the metallic composite part of varied nickel volume fraction and the dielectric part. Two parts of the sputtering zone can form a graded absorbing layer with the right ratio of base and middle layer by the moving substrate technique. Distribution of normalized conductivity, <i>NC</i>, along the absorbing sputtering zone is a simple and good specification of zone property. Profile of graded film prepared by the moving substrate technique can be tailored according to <i>NC</i> distribution. XRD and XPS study confirms the <i>NC</i> results. Simulation reveals that absorption should mainly rely on the intrinsic, but less on the interference mechanism. Used metallic volume fraction of Ni-NiO is 0.3 for main absorbing layer. The front surface reflection loss due to high refractive index can be reduced by adding a layer with low refractive index on the top. Simulation shows that three-layer coatings are a good and simple coating structure. High solar absorptance of 0.97 has been achieved with low thermal emittance of 0.05 by theoretical simulation as well as experimentally prepared samples.</p>

The aim of this thesis was to develop wear resistant physical vapour deposited coatings of TiB2 as well as multilayers of Cr/CrN. The correlation between deposition parameters and fundamental coating properties such as microstructure, composition, residual stress and hardness has been investigated. Finally, the influence of these properties on the coating behaviour in tribological applications has been evaluated. It is shown that the use of electron bombardment of the growing coating during d.c. magnetron sputtering is beneficial for the growth of superhard TiB2 coatings. Furthermore, electron bombardment results in TiB2 coatings with significantly lower residual stresses than coatings deposited using ion bombardment. The low stresses in these coatings open up the possibility to deposit thicker PVD coatings, as confirmed in this thesis. In addition, the use of TiB2 coatings in tribological contacts against aluminium proved to be superior to many other commercial coatings used today, with respect to wear resistance, anti galling properties and a low friction. Finally, a model is proposed which explains the observation that the abrasive wear resistance of multilayered Cr/CrN coatings can outperform that of the individual constituents. The model was found to satisfactory predict experimental data.

Spectrally selective solar absorber using composite Ni-NiO as coating materials was studied. Samples were prepared by dc magnetron sputtering unit named Rulle, which is a miniature copy of an industrial roll-coater unit. Using asymmetric location of the oxygen nozzele, it is possible to form the desired metallic concentration distribution along the sputtering zone under optimized conditions. This distribution can be transferred into a graded film profile by moving the substrate, obtaining good spectral selectivity. For specified mechanical settings (such as locations of gas sprays, target and pump positions etc.), the ratio of used oxygen flow to the corresponding critical oxygen flow, <b>RO</b>, is a dimensionless parameter to control the zone specification. The optimal value is around 0.80 for the Rulle. Optimized zone shows properties with two main parts: the metallic composite part of varied nickel volume fraction and the dielectric part. Two parts of the sputtering zone can form a graded absorbing layer with the right ratio of base and middle layer by the moving substrate technique. Distribution of normalized conductivity, NC, along the absorbing sputtering zone is a simple and good specification of zone property. Profile of graded film prepared by the moving substrate technique can be tailored according to NC distribution. XRD and XPS study confirms the NC results. Simulation reveals that absorption should mainly rely on the intrinsic, but less on the interference mechanism. Used metallic volume fraction of Ni-NiO is 0.3 for main absorbing layer. The front surface reflection loss due to high refractive index can be reduced by adding a layer with low refractive index on the top. Simulation shows that three-layer coatings are a good and simple coating structure. High solar absorptance of 0.97 has been achieved with low thermal emittance of 0.05 by theoretical simulation as well as experimentally prepared samples.

This thesis treats the reflective and structural properties of multilayer structures. Soft X-ray multilayer mirrors intended as near-normal incidence reflective optics and polarizers in the water window (λ=2.4-4.4 nm) are the main focus. Such mirrors require multilayer periodicities between 1.2-2.2 nm, a large number ~600of multilayer periods (N), and atomically flat interfaces. Bi-metallic multilayers were deposited by dual-target magnetron sputtering on Si(001) Geometrical roughness and intermixing/interdiffusion at the interfaces were investigated in connection with the impact of ion-surface interactions during growth of Cr/Ti, Cr/Sc, and Ni/V multilayers. This was achieved by comparing multilayers grown with or without high-flux low energy (Eion&lt;30 eV) ion assistance. The use of modulated ion assistance resulted in a substantial improvement of interface flatness and abruptness in each of theAb-initio calculations indicate that the stabilization of the amorphous layer structure is due to a lowering of the total energy of the system by eliminating high energy incoherent interfaces between crystalline Sc and Cr. Light element incorporation in Cr/Sc multilayers was investigated through residual gas pressure variation. It is shown that multilayers retain their structural and optical properties within the high vacuum range of 2×10-7-to-2×10-6 Torr. The incorporation of 34 at.% nitrogen at a higher residual gas pressure ( ~2×10-5 Torr) resulted in highly textured understoichiometricx/ScNy multilayers. As a result of nitrogen incorporation, interface widths as small as 0.29 nm, and near-normal incidence reflectivity enhancement (at λ=3.11 nm) by 100 % (compared to pure Cr/Sc multilayers) was achieved. Light element incorporation was also found to be advantageous for the thermal stability of the multilayers. In-situ hard X-ray reflectivity measurements performed during isothermal annealing in thex/ScNy are stable up to 350 °C. As an alternative route to metallic multilayers, single crystal CrN/ScN superlattices, grown by reactive sputtering in N atmosphere onto MgO(001), were also investigated. The superlattice synthesis at 735 °C, resulted in highly abrupt interfaces with minimal interface widths of 0.2 nm. As-deposited superlattices with only 61 periodsλ=3.11 nm as well as very high thermal stability up to 850 °C. / Denna avhandling behandlar syntes, analys, och materialvetenskap rörande så kallade multilagerspeglar för mjuk röntgenstrålning. Speglarna är lämpade som optiska komponenter för instrument såsom röntgenmikroskop i våglängdsområdet 2,4 nm till 4,4 nm, även kallat vattenfönstret. Tack vare de senaste decenniernas stora teknologiska och vetenskapliga framsteg i att framställa mycket intensiva källor för mjuk röntgenstrålning, såsom tex synkrotronljuskällor, frielektronlasrar, och plasmagenererade källor, är det nu tänkbart att utnyttja denna strålning till nya tillämpningar som tidigare inte varit möjliga. Några exempel är; röntgenmikroskopi av biologiska preparat med upplösning ca 1/100 av det som är möjligt med synligt ljus, fotolitografi av Det finns flera stora utmaningar för att lyckas tillverka multilagerspeglar. Först och främst måste man hitta materialkombinationer som ger upphov till reflektion i mellanytorna mellan materialen men som inte samtidigt absorberar all röntgenstrålning. Dessutom måste materialen gå att belägga på varandra i flera hundra tunna lager, vart och ett endast ca 1 nanometer tjockt, med en ytojämnhet om endast några tiondels nanometer. Den absoluta tjockleks precision i varje I det här arbetet har fyra olika typer av multilagerbeläggningar undersökts: krom/titan (Cr/Ti), krom/skandium (Cr/Sc), nickel/vanadin (Ni/V) samt kromnitrid/skandiumnitrid (CrN/ScN). Materialvalen har baserats på teoretiska beräkningar som visat att dessa materialsystem genererar mycket god reflektans i vattenfönstret. Varje kombination av metaller är optimal för en specifik våglängd och de individuella lagertjocklekarna måste optimeras teoretiskt för varje enskilt För Cr/Sc multilager har vi visat att lagren som beläggs har en oordnad, så kallad amorf, struktur mellan metallatomerna som har sitt ursprung i att multilagrets totala energi kan sänkas om mellanytor mellan kristallint Cr och kristallint Sc kan undvikas. Studier av effekterna av kväveupptag hos Cr/Sc multilagerspeglar under sputtringsprocessen har lett till ökad förståelse av materialsystemet. Till exempel har vi visat att kvävet framförallt binder till de inre regionerna av Sc och inte så mycket till Cr-lagren eller i mellanytorna. Med kväve i strukturen har vi gjort speglar som tål höga temperaturer, vilket är av stor betydelse för tillämpningar baserade högintensiva ljuskällor. Så kallade supergitter, dvs multilager

This thesis reports on synthesis, microstructure and properties of binary and ternary carbide thin films deposited by dc magnetron sputtering. These materials are interesting since they exhibit a wide range of useful properties, such as high hardness, resistance to wear and oxidation, and high electrical conductivity. Here, an early transition metal (M) and carbon (C) have been used as the basis, often with the addition of a second M-element or an A-group element (A). In these systems nanocomposites, metastable solid solutions, multilayers, or Mn+1AXn-phases have been deposited. The Mn+1AXn-phases are a group of nanolaminated compounds with a unique mixture of metallic and ceramic properties. In general X is carbon or nitrogen, although here only carbon has been used. Epitaxial MAX-phase thin films of Ti2AlC, Ti3AlC2 and V2GeC have been deposited for the first time. They have been studied with emphasis on phase stability, phase composition and nucleation characteristics to gain deeper insights into their growth. The microstructure of the films was characterized by electron microscopy and X-ray diffraction. In addition, bond strength characteristics have been studied by soft X-ray spectroscopy and complementary calculations within DFT. Their mechanical and electrical properties have been studied, and the results are discussed on the basis of their electronic structure. Furthermore, by interleaving the Ti3SiC2 MAX-phase with TiC0.67 a multilayer structure has been formed, for which a new intrusion-type deformation behaviour has been described. A new concept in the design of nanocomposite films has been developed, whereby a solid solution of a weak carbide-forming element in the carbide structure creates a driving force for surface segregation of C. This concept has been verified both theoretically and experimentally for the Ti-Al-C and Ti-Fe-C systems. It has been shown by pin-on-disc measurements that this surface segregation leads to graphitization and consequently a very low friction coefficient for these films. Finally, it has been demonstrated that low-friction films with tunable magnetic properties can be achieved in the Ti-Fe-C system.