La production d'eau chaude via des capteurs solaires photothermiques est une technique en expansion qui permettra de limiter l'utilisation des sources conventionnelles d’énergie (combustibles fossiles, nucléaire…). Le cuivre noir (CuO) s’avère être un matériau possédant des propriétés optiques sélectives intéressantes pour cette application. Ainsi, son utilisation au sein d’un absorbeur sous forme d’un matériau « tandem » est une solution envisagée. Le défi que nous avons tenté de relever au cours de ce travail, a été de réaliser ce type de matériau par dépôt électrophorétique (EPD) de nanoparticules de CuO déposé sur un substrat métallique de type wafer de silicium recouvert de platine ou d’or. Ce substrat « modèle » a été utilisé dans un premier temps, car il facilite la mise en œuvre de techniques de caractérisation telles que l’analyse par diffraction X en incidence rasante (GIXRD) ou l’analyse en coupe par microscopie électronique à balayage. Pour ce faire, la stabilisation de la suspension colloïdale de CuO, qui est une condition sine qua non pour la réalisation d’un dépôt électrophorétique, a été étudiée dans un solvant organique tel que l'isopropanol par ajout de Mg(NO3)2, ainsi que dans l’eau en utilisant du polyethylenimine comme dispersant. Ces deux adjuvants agissent comme des agents stabilisants et apportent aux nanoparticules une charge positive ce qui permet la réalisation d'un EPD cathodique. Afin d’optimiser la formulation des suspensions, la stabilité colloïdale en fonction de la teneur en stabilisant a été étudiée avant tout dépôt, par diffusion dynamique de la lumière (DLS) couplée à la vélocimétrie laser à effet Doppler.Différents revêtements contenant du CuO ont été obtenus en faisant varier les paramètres classiques de l’EPD (temps de dépôt, champ électrique, concentration en nanoparticules) pour pouvoir contrôler l'épaisseur finale et la morphologie. Par conséquent, la sélectivité optique et le rendement du tandem résultants peuvent être optimisés en jouant sur l’ensemble de ces paramètres. Des dépôts homogènes ont été obtenus pour [CuO] =5x10-4 g/cm3 pour les deux milieux. Les meilleures conditions sont 50 V.cm-1// 30mn pour la suspension d'IPA et 2 V.cm-1 // 120 mn pour la suspension en milieu aqueux. La composition et l'épaisseur des dépôts sont analysées par GIXRD, et par microscopie électronique (SEM-EDS). Pour les conditions optimisées, les matériaux tandem obtenus à partir de la suspension d'IPA+CuO possèdent une densité de 1.69 g/cm3 avec une grande rugosité. Au contraire, des surfaces homogènes et régulières sont obtenues en milieu aqueux et les dépôts présentent une densité beaucoup plus élevée d’environ 5.7 g/cm3.L’absorptance (α) et l’émittance (ԑ) ont été calculées à partir des spectres de réflectance de l'UV-VIS-NIR et de l’Infrarouge lointain, respectivement. L'efficacité (ƞ) du revêtement tandem obtenu en milieu aqueux est comprise entre 0.8-0.87 tandis qu’elle est seulement de 0.7 dans l’IPA. De plus, la faisabilité de l’EPD sur d’autres substrats métalliques plus conventionnels en vue d’une application (acier, aluminium, cuivre) a été explorée. L'efficacité des dépôts a pu être améliorée par des post-traitements de deux types. D’une part, en pyrolysant à 400°C sous atmosphère inerte le polymère (PEI) incorporé dans le revêtement. Le carbone résiduel obtenu à l’issue de cette pyrolyse a permis d’augmenter l’absorbance. D’autre part, en déposant sur la surface des revêtements une couche de nanoparticules de SiO2 qui joue le rôle de couche anti-réflexion et permet également de protéger la surface. Les deux voies ont été réalisées avec succès et le rendement le plus élevé obtenu pour ces revêtements est de 0.9. / The production of hot water by using efficient photothermal solar collectors is growing in importance to limit the use of fossil fuels. Black copper (CuO) has proved to be one of the viable solar-selective coatings owing to its nearly intrinsic properties. The formation of a tandem absorber based on CuO thin film deposited onto a highly IR reflecting metallic substrate is processed by electrophoretic deposition (EPD).In this way, the stabilization of a CuO colloidal suspension is studied previously by adding Mg(NO3)2 in isopropanol (IPA) or polyethylenimine (PEI) in water suspension. Both acts as positively charging agents and allow the realisation of a cathodic EPD. The colloidal stability as a function of the stabilizing agent content is studied prior to EPD, by dynamic light scattering (DLS) coupled with laser doppler velocimetry.CuO tandem absorbers are obtained by varying different EPD parameters to control the final thickness and also the morphology. Consequently, the optical selectivity of the tandem material is tuned and optimized. The deposition yield is compared relative to the different applied voltage range, deposition time and nanoparticle concentrations. Homogeneous deposits are obtained for [CuO]=5x10-4 g/cm3 from both suspensions. The optimum applied voltage is found to be 50 V.cm-1 for IPA suspension and 2 V.cm-1 for H2O suspension, for deposition times of 30 mins and 120 mins, respectively. The composition and the thickness of the coatings are analysed by Grazing Incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM) and the density is obtained from energy-dispersive X-ray spectroscopy (EDX). For the previously mentioned optimized conditions, CuO tandem absorbers derived from IPA suspension possess a density of 1.69 g/cm3 with high surface roughness. In contrast, homogeneous and regular surfaces is obtained from water suspensions having a higher density of 5.7 g/cm3.Moreover, absorptance (α) and emittance (ԑ) are calculated from the reflectance spectra of the UV-Vis-NIR and the Fourier transform InfraRed (FTIR) spectroscopy, respectively. α and ԑ were combined to determine the efficiency (ƞ) of the tandem material. Tandems obtained from water suspension has ƞ=0.8 -0.87 while from IPA ƞ=0.7. Besides, the applicability of this EPD is checked by performing other deposit of CuO on metallic substrates of different types.CuO tandems obtained from water suspensions are clearly more prominent to be used as solar selective tandem absorbers due to the high calculated ƞ value reported. The efficiency of such selective tandem absorbers was further enhanced by carbonization (pyrolysis under inert atmosphere) of the polymer (PEI) embedded in the coating. Otherwise, a thin film of SiO2 nanoparticles was deposited at the surface of the selective tandem absorbers to protect them. Both routes were successfully processed and proved to raise ƞ to 0.9.

Aeronautical industry is interested in using damage tolerant, high strength and lightweight materials in the manufacture of some structural components that must attend tight requirements. Carbon nanotubes doped multiscale composites are good new generation material candidates to improve aeronautical grade composites. This project includes comprehensive characterization studies of electrophoretic deposition treated carbon nanotubes doped carbon fiber polymer composites with different stacking sequences. For comparison purposes, spray-on treated carbon nanotubes doped carbon fiber composites and non-doped reference composites with different stacking sequence are also studied. The goal of the project is to verify the link between the effects of carbon nanotubes addition, micro-nanostructure and macro material properties. To achieve this goal, several thermal loading damage analyses and investigations on micron and sub-micron scale were performed. In this thesis, the readers will be able to find the necessary theoretical background information, experimental procedure, results and conclusions gained throughout this project. / <p>Validerat; 20120621 (anonymous)</p>

This diploma thesis deals with the preparation of doped piezoceramic materials based on BaTiO3 using electrophoretic deposition. Five rare earth oxides, i.e. Er2O3, Dy2O3, Eu2O3, Tb407 and CeO2, were used as dopants in amounts of 1, 3, and 5 wt. %. The prepared deposits were evaluated in terms of preparation methodology, high temperature dilatometry, X-ray diffraction analysis, relative density, mean grain size, hardness and fractographic analysis. The study of dilatometric curves described the sintering behavior and its changes at different material compositions. X-ray diffraction analysis revealed a tetragonal phase in all samples; the tetragonality of the BaTiO3 crystalline cell decreased with dopant content. By a suitable choice of dopant, it was possible to significantly increase the relative density of sintered samples, their hardness and at the same time prevent the samples from coarsening of the microstructure during heat treatment. A relative density up to 98 %, a mean grain size below 1 m and a hardness of over 10 GPa were achieved. Analysis of the fracture surfaces revealed that the fracture mode was transcrystalline for the most of studied materials; only the samples doped with cerium dioxide had fracture surfaces with both transcrystalline and intercrystalline fracture modes. Based on the obtained results, a suitable composition of the material for the intended use in a layered piezoceramic harvester was identified, which, in addition to the BaTiO3 layers, consists of functionally-protective Al2O3 and ZrO2 layers.

This master‘s thesis deals with study of basic physical, microstructural and mechanical properties of doped piezoceramic materials based on BaTiO3 prepared by electrophoretic deposition. The dopants used were rare earth oxides, i.e. Eu2O3, Er2O3, CeO2, Dy2O3 and Tb4O7 in amounts 1, 3 and 5 wt. %. The influence of dopants and their amount on density, phase composition, mean grain size, hardness, elastic modulus, fracture toughness, and flexural strength was examined. Suitable dopant choice enabled decrease in mean grain size and increase in relative density, hardness, elastic modulus, fracture toughness and flexural strength of sintered specimens. Relative densities up to 99 %, mean grain size below 1 m, hardness up to 13,1 GPa, elastic modulus up to 199 GPa, fracture toughness above 1 MPa·m1/2 and flexural strength above 115 MPa were achieved.

The work was focused on the preparation of layered ceramic materials and their characterizations. The direct measurment of weight deposite for enhanced description of one component system was studied within this work. The kinetics of electrophoretic deposition obtained from theoretical calculation and from experimental values were confronted. It was prepared a lot of depositions for described kinetic of electrophoretic deposition with applied constant currents. The relative density and porosity were determined on the annealled and sintered bodies. The hardness measurments were performed on sintered bodies and then resulted values were confronted with the used currents. A ceramic composite based on Al2O3 and ZrO2 was prepared by using of precision describtion of electrophoretic deposition kinetic.

Z důvodu rozdílných koeficientů délkové teplotní roztažnosti jednotlivých vrstev vzniká ve vrstvách keramického vrstevnatého kompozitního materiálů reziduální napětí. V průběhu chladnutí vrstevnatého kompozitu ze slinovací teploty jednotlivé vrstvy smršťují různými rychlostmi v závislosti na velikosti koeficientu délkové teplotní roztažnosti. Jestliže jsou tyto vrstvy spolu pevně spojeny vzniká v jednotlivých vrstvách různě velké trvalé zbytkové napětí. Velikost residuálního napětí je dána objemovým podílem obou složek v kompozitu. Tato práce byla zaměřena na přípravu a popis 7-mi a 9-ti vrstevných keramických laminátů složených ze střídajících se vrstev dvou rozdílných materiálů. Keramické lamináty byly připraveny pomocí metody suspenzního lití a elektroforetické depozice. U připravených laminátu byl sledován vznik tzv. hranových trhlin (edge cracks) ve vrstvách obsahujících tlaková zbytková pnutí. Výsledky pozorování přítomnosti hranových trhlin pro různou konfiguraci velikosti zbytkových napětí a tloušťky vrstev byly srovnány s teoretickou předpovědí vytvořenou pomocí parametrického 2D modelu. Vliv vzniklých hranových trhlin na průběh lomu byl studován pomocí 3D rekonstrukce lomového povrchu po ohybové zkoušce připravených vrstevnatých kompozitů.

The thesis was focused on preparation of bioceramic composite materials containing Ca-phosphates and zirconia fibers using electrophoretic deposition. A series of experiments were aimed at determining the appropriate composition of the suspensions. High-energy milling was used for preparing deposits with good physical and mechanical properties using EPD. The influence of milling time, the amount of monochloroacetic acid in isopropanol slurry indifferent electrolyte LiCl and ZrO2 were evaluated on the course deposition and the resulting properties of the deposits. Influence of sintering temperature, the milling time and the fiber content of ZrO2 on the chemical and structural composition was determined by X-ray analysis, measurement of density and structural analysis using a scanning electron microscope. Mechanical and bioactive properties of sintered deposits were determined depending on the milling time and content of ZrO2 fibers.

The doctoral thesis is orientated to preparation of advanced ceramic materials by electrophoretic deposition (EPD). The vertical mode of EPD in constant current regime was used in this study. The morphology of prepared materials (image structural analysis), physical properties (EPD yields, relative density, roughness of deposit surface) and mechanical properties (hardness, fracture toughness, elastic module) were characterized on the prepared deposits from alumina (Al2O3), zirconia (ZrO2) or their composites. It was found that the surface charge of alumina or zirconia particles was opposite (inversion charge) in stabilized isopropanolic dispersions than in case of water dispersions. The model of alumina or zirconia particles “inverse” stabilization was proposed. This type of EPD was further studied in presence of different acidic stabilizers. The obtained results from the experimental work (-potential and electric conductivity of dispersions, EPD yields, relative density of deposits, roughness of deposit surface etc.) showed the monochloracetic acid as the optimal type of acidic stabilizer. The kinetic of EPD process from dispersions containing isopropanol, monochloracetic acid and Al2O3 or ZrO2 particles and its influence on the final properties of prepared deposits was studied. The new method of kinetic measurement was developed. Due to good knowledge of EPD kinetic the ceramic laminates (Al2O3/ZrO2) with optimized layer thickness were prepared. The internal stresses and their influence on crack trajectory in ceramic laminates contained 100-150 strongly bonded layers were studied. It was found that the dominant role of crack deflection played the internal compressive stresses, i.e. with increasing of amount of internal compressive stresses the crack deflection was also increased. This work brought a new knowledge in the area of non-aqueous ceramic dispersion stabilization and preparation of heterostructured ceramic materials.

The global market for fluoropolymers, including polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), is growing rapidly due to their copious applications in the construction, automotive, medical, chemical, and electrical industries. Fluoropolymers owe their popularity partly to their excellent chemical and thermal stability and useful mechanical, piezoelectric, and ferroelectric properties. They are made into films or coatings that are used for corrosion protection or surface property enhancement. Electrophoretic deposition (EPD) has generated increasing interest in manufacturing advanced films for various applications due to its low cost, versatility, simple apparatus, and good film quality compared with other deposition techniques like dip coating, spin coating, electrospinning, or spay coating. Moreover, EPD facilitates uniform deposition on the substrates of complex shapes at a high deposition rate. The aim of this research is to develop novel biomimetic strategies for fabricating polymer films and their composite films with multifunctional particles through EPD. This method involves the electrophoresis of charged particles in a stable colloidal suspension towards an electrode, forming deposition. Fluoropolymers, however, are electrically neutral and chemically inert, and their EPD presents difficulties. Therefore, successful EPD depends on understanding how to modify the surface of polymer particles using advanced biosurfactants to impart charge and form a well dispersed, stable colloidal suspension. One strategy is to leverage the unique dispersing power of bile acids and salts as biosurfactants for EPD of PTFE and PVDF films and composite films. When doing so, it was found that the amphiphilic structure of bile salts such as sodium deoxycholate (DChNa) facilitated adsorption on the chemically inert, hydrophobic surfaces of PTFE, diamond, and carbon dots. In this strategy, DChNa acted as a charging, dispersing, film-forming agent for the co-deposition of PTFE composite films from an aqueous suspension. Water insoluble bile acids (BAs) were found to be biosurfactants for the EPD of PTFE and PVDF from organic solvents, in which lithocholic acid (LCA) was used as a co-dispersant for the fabrication of composite PTFE-diamond coatings and PTFE coatings provided corrosion protection for stainless steel in 3% NaCl solutions. The dispersing performance of four other bile acids, chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), ursodeoxycholic acid (UDCA), and cholic acid (ChA), was analyzed and compared with LCA on the deposition performance of PVDF. It was found that the PVDF deposition yield obtained using different BAs increased in the order of LCA<CDCA<DCA<UDCA<ChA. This was attributed to the difference in number, position, and orientation of OH groups in the structures of the BAs. Another biomimetic strategy for the EPD of polymers and composites was inspired by the strong adsorption of mussel protein on rock surfaces in sea water. Catecholate-type molecules, caffeic acid (CA) and catechol violet (CV), were found to be biosurfactants for dispersing, charging, and depositing PVDF films and composites. Analyses of the deposition yield data, the chemical structure of the CA and CV, and the microstructure and composition of the films suggested that the aromatic rings on the CA and CV had hydrophobic interactions with the PVDF particles and that the phenolic groups formed bidentate chelating or bridging bonding to inorganic particle surfaces. The study demonstrated the feasibility of co-depositing PVDF with nanoparticles of TiO2, MnO2, and NiFe2O4. CA was also used for preparing PVDF-HFP particles and as a co-dispersant for the co-deposition of PVDF-HFP with NiFe2O4 and CuFe2O4 nanoparticles in order to make composite films that combine the ferrimagnetic properties of spinel ferrites with the multifunctional properties of ferroelectric polymers. / Dissertation / Doctor of Philosophy (PhD)

Novel electrodeposition strategies have been developed for the fabrication of thick adherent zirconia ceramic and composite coatings for biomedical applications. The new method is based on the electrophoretic deposition (EPD) of polyelectrolyte additives combined with the cathodic precipitation of zirconia. The method enables the room- temperature electrosynthesis of crystalline zirconia nanoparticles in the polymer matrix. Adherent crack-free coatings up to several microns thick were obtained. The deposits were studied by thermogravimetric and differential thermal analysis, X-ray diffraction analysis, scanning and transmission electron microscopy, and atomic force microscopy. Obtained results pave the way for electrodeposition of other ceramic-polymer composites. Novel advanced nanocomposite coatings based on bioceramic hydroxyapatite (HA) have been developed for the surface modification of orthopaedic and dental implant metals. HA nanoparticles prepared by a chemical precipitation method were used for the fabrication of novel HA-chitosan nanocomposite coatings. The use of chitosan enables room-temperature fabrication of the composite coatings. The problems related to the sintering of HA can be avoided. A new electrodeposition strategy, based on the EPD of HA nanoparticles and electrochemical deposition of chitosan macromolecules, has been developed. The method enabled the formation of dense, adherent and uniform coatings of various thicknesses in the range of up to 60μm. Bioactive composite coatings containing 40.9-89.8 wt% HA were obtained. The deposit composition and microstructure can be tailored by varying the chitosan and HA concentrations in the deposition bath. A mathematical model describing the formation of the HA-chitosan composite deposit has been developed. X-ray studies revealed preferred orientation of HA nanoparticles in the nanocomposites. Obtained coatings provide corrosion protection of the substrates and can be utilized for the fabrication of advanced biomedical implants. For further functionalization of the HA-chitosan composite coating, Ag and CaSi03 have been incorporated into the coating. Novel HA-Ag-chitosan and HA-CaSiO3-chitosan nanocomposite coatings have been deposited as monolayers, laminates, and coatings of graded composition. The obtained results can be used for the development of biocompatible antimicrobial coatings with controlled Ag+ release rate, and nanocomposite coatings with enhanced bioactivity. / Thesis / Doctor of Philosophy (PhD)