This past decade, 2D materials beyond graphene, and most specifically transition metal dichalcogenides (TMDCs) have gained remarkable attention due to their novel applications in electronics and optoelectronics applications. This work reports large-area growth and structural, optical, and electronic transport properties of few-layer MoS2 thin films fabricated using a hybrid approach based on the magnetron sputtering method. In the first part of this dissertation, properties of optimally annealed MoS2 on different substrates such as amorphous BN, SiO2, Si, Al2O3 are discussed using diffraction, spectroscopic, and transport techniques. Later, we show that the physical properties of large-area sputtered MoS2 thin films can be dramatically improved by an ex-situ high-temperature sulfurization process as it leads to the formation of defect-free MoS2 by removing sulfur vacancies. Sharp film-substrate interface along with high bulk structural order is demonstrated as inferred from diffraction and spectroscopic methods. We show that sulfur vacancies can obscure the MoS2 A-B exciton peaks along with a sharp increase in dc conductivity of MoS2. In the last part of my dissertation, we outline the growth of a novel thermoelectric material (SnSe) and new magnetic inverse-Heuslers (of nominal composition MnxFeSi) using the co-sputtering method. These are some of the first attempts, to our knowledge, to grow such materials in thin-film form. Detailed structure-property relations are thoroughly discussed.

Alkali activated materials are a promising generation of binders, which can be significantly recognized by having lower carbon footprint, being waste originated, and having unique chemistry and thermodynamics. It appears that alkali activated materials can be engineered to exhibit high-tech and intelligent performances with less effort compared to Portland cement-based binders, if appropriately formulated. In addition, alkali activated materials have several inherent properties such as adjustable microstructure and strength, and heat and chemical resistances. Based on these explanations, the focus of this doctoral thesis was on the fabrication and characterization of multifunctional and smart alkali activated nanocomposites. The investigated alkali activated system was composed of fly ash, ground granulated blast-furnace slag (GGBS), and sodium-based silicate and hydroxide. Carbon nanotubes (CNTs) were incorporated into the alkali activated matrix to constitute a functional complex nano system. Multi-walled carbon nanotubes (MWCNTs) were utilized for colloidal, mechanical and microstructural studies and single-walled carbon nanotubes (SWCNTs) applied for electrical, thermoelectric and sensing assessments. The colloidal and mechanical performances and microstructural characteristics have been assessed for the alkali activated nanocomposites, which were fabricated by a dispersion of MWCNTs (0.05 wt.%) into sodium-based silicate and hydroxide solutions and their combination. The highest MWCNTs’ dispersibility and in-solution stability and smallest dimension of agglomerations were observed in the sodium silicate dispersion media. Accordingly, the highest compressive and flexural strengths were accomplished for mentioned nanocomposites, ≈60 MPa & ≈10 MPa, respectively. The reason for the mechanical improvement was the effective reinforcement of MWCNTs when dispersed in sodium silicate. The MWCNTs were more functional in pore refinement and crack propagation control of the nanocomposites’ microstructure. Thermoelectric properties and thermoelectric power generation performances have been studied for the alkali activated nanocomposites and the resultant generator device. SWCNTs were used for the alkali activated thermoelectric generator fabrications. A single piece of nanocomposite with SWCNT content of 1 wt.% could achieve a Seebeck coefficient of ≈16 μV·K-1 and power factor of 0.4 μW·m-1·K-2. The thermoelectric generator device consisted of 10 serially interconnected alkali activated thermoelements (p-type elements). The highest generated thermoelectric voltage and power with inclusion of 1 wt.% of SWCNTs in the nanocomposites were ≈7 mV and ≈0.7 µW, respectively at ΔΤ of 60 K. In the last phase of this doctoral research the idea of ion discrimination and the potential of being a sensor have been conceptualized and demonstrated for SWCNT alkali activated nanocomposites. The alkali activated sensors were produced by incorporation of 0.1 wt.% of SWCNTs based on the results of conducted percolation study. The sensors displayed an ion discrimination potential by transmitting signals with a detectable difference in geometry and magnitude in exposure to the introduced analytes. The discrimination criteria were analytes’ type, concentration, and volumetric quantity. The SWCNT alkali activated sensors showed a higher magnitude of relative resistance in exposure to the sulphuric acid compared to the magnesium sulphate. In addition, the obtained signals in sulphuric acid exposure had a curvature shape but the signals of magnesium sulphate were rectangular. The introduced sensors were applicable for the sulphuric acid concentration detection in a range of 0.001 to 0.1 M. The sensors did not have any upper threshold limit, however the lower threshold limit for sulphuric acid concentration detection was 0.001 M. There was a direct relation between the exposed quantity of sulphuric acid and relative resistance of the alkali activated sensors. The finding of this doctoral research can be utilized for development of alkali activated nanocomposites with industrial implementations. That may include nano reinforced structural elements, thermoelectric generators for green energy production and sensors for structural health monitoring of concrete infrastructures.:Chapter 1. Motivation and innovation 1 1.1. Introduction 1 1.2. Alkali activated materials and geopolymers 1 1.3. Mechanical properties 2 1.3.1. Challenge 2 1.3.2. Novelty 4 1.4. Thermoelectricity 5 1.4.1. Challenge 6 1.4.2. Novelty 6 1.5. Sensing concept 7 1.5.1. Challenge 8 1.5.2. Innovation 10 1.6. Aim 10 1.7. Strength and shortcoming 11 1.8. Structure 11 Chapter 2. Methodology 17 2.1. Materials 17 2.1.1. Carbon nanotubes 17 2.1.2. Surfactants 18 2.1.3. Precursors 19 2.1.4. Activators 20 2.1.5. Analytes 20 2.2. Methods 21 2.2.1. Two-part activation technology 21 2.2.1.1. MWCNTs and naphthalene sulphonate concentrations 21 2.2.1.2. Fabrication methodologies of nanofluids and nanocomposites 21 2.2.1.2.1. Na2Si3.5O9 based nanofluids and nanocomposites (strategy I) 22 2.2.1.2.2. NaOH based nanofluids and nanocomposites (strategy II) 22 2.2.1.2.3. Combined (Na2Si3.5O9+NaOH) nanofluids and nanocomposites (strategy III) 23 2.2.1.3. Dispersion of nanofluids 23 2.2.1.4. Mixing of nanocomposites 24 2.2.2. One-part activation technology 24 2.2.2.1. SWCNTs and SDBS concentrations 25 2.2.2.2. Fabrication methodology of nanofluids 25 2.2.2.2.1. Thermoelectricity 25 2.2.2.2.2. Sulphate sensing 25 2.2.2.2.3. Sulphuric acid sensing 25 2.2.2.3. Fabrication methodology of nanocomposites 26 2.2.2.3.1. Thermoelectricity 26 2.2.2.3.2. Sulphate sensing 26 2.2.2.3.3. Sulphuric acid sensing 26 2.3. Characterizations 27 2.3.1. Optical microscopy 27 2.3.2. Integral light transmission (ILT) 27 2.3.3. Scanning electron microscopy (SEM) 27 2.3.4. Transmission electron microscopy (TEM) 28 2.3.5. Fourier-transform infrared spectroscopy (FTIR) 28 2.3.5.1. Alkaline nanofluids 28 2.3.5.2. Chemiresistor nanocomposites 29 2.3.6. Mercury intrusion porosimetry (MIP) 29 2.3.7. Roughness measurements 29 2.3.8. pH measurements 29 2.3.9. Mechanical properties 29 2.3.10. Thermoelectric acquisitions 30 2.3.11. Thermoelectric generator acquisitions 31 2.3.12. Sensing and discriminating acquisitions 31 Chapter 3. Dispersion of CNTs 33 3.1. Introduction 33 3.2. MWCNTs dispersibility 33 3.3. MWCNTs dispersion stability 36 3.4. MWCNTs and naphthalene sulphonate interactions 38 3.5. Potential physisorption 42 3.6. Conclusion 44 3.7. Perspective 44 Chapter 4. Microstructure refinement 45 4.1. Introduction 45 4.2. Mechanical reinforcement 45 4.3. Reinforcement mechanism 49 4.3.1. Morphology 49 4.3.2. Porosity 55 4.4. Conclusion 60 4.5. Perspective 61 Chapter 5. Thermoelectricity 63 5.1. Introduction 63 5.2. Thermoelectric properties 63 5.3. Thermoelectric generator 65 5.3.1. Power output 65 5.3.2. Stability performance 69 5.4. Mechanical properties 70 5.5. Multifunctional behaviour 71 5.6. Conclusion 73 5.7. Perspective 74 Chapter 6. Sulphate discrimination 77 6.1. Introduction 77 6.2. Percolation threshold 77 6.3. Sulphate discrimination 80 6.4. Concentration differentiation 84 6.5. Quantity differentiation 86 6.6. Conclusion 88 6.7. Perspective 89 Chapter 7. Sulphuric acid sensing 91 7.1. Introduction 91 7.2. Electrical properties 91 7.3. Morphology of the SWCNTs’ conductive network 92 7.4. Sensing properties 96 7.4.1. Exposure to ultrapure water 96 7.4.2. Exposure to sulphuric acid 97 7.4.2.1. pH influence 100 7.4.2.2. Surface composition change 103 7.4.3. Sensor sensitivity 106 7.5. Microstructure dependency 109 7.5.1. SWCNTs and matrix interactions 109 7.5.2. Matrix porosity 113 7.5.3. Matrix roughness 115 7.6. Conclusion 118 7.7. Perspective 119 Summary 121 References 123 Publications from this doctoral research 151

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Thermoelectric materials are capable of direct conversion of thermal energy to electrical energy and vice versa. Their applications include thermoelectric coolers, generators, as well as sensors. Conventional thermoelectric devices consist of multiple units of p-type and n-type semiconducting elements, in which electrical current and heat flux flow parallel to each other. In contrast, transverse thermoelectric devices could decouple electrical current and heat flux such that they flow perpendicular to each other. Transverse thermoelectricity could be realized in single-phase anisotropic materials or composite materials with engineered anisotropy. Studies have shown that composite transverse thermoelectric materials could provide a better performance than their single-phase counterparts. In this dissertation proposal, two configurations of transverse thermoelectric composites are examined using both analytical and numerical methods. Mathematical models are established to calculate the effective properties of anisotropic thermoelectric composites by analyzing the representative unit cells using the Kirchhoff circuit law (KCL) and the Thevenin’s theorem followed by tensor transformation. Thermoelectric figure of merit (ZT), power factor, as well as cooling performance (maximum cooling temperature ΔTmax) of transverse thermoelectrics are studied. Comparisons between the mathematical models and numerical simulation showed good agreement, while some discrepancies are observed and discussed. Since transverse composite thermoelectrics can decouple the electrical and thermal transports, they can offer new opportunities for device design including thin film sensors and cascading coolers, as well as for performance enhancement such as improved power factors. / Mechanical Engineering

The development of organic-inorganic hybrid materials is of great interest in thermoelectrics for its potential to combine the desirable characteristics of both classes of materials. Thermoelectric materials must combine low thermal conductivity with high electrical conductivity, but in most materials, thermal and electrical conductivity are closely related and positively correlated. By combining the low thermal conductivity, flexibility, facile processing, and low cost of organic components with the high electrical conductivity and stability of inorganic components, materials with beneficial thermoelectric properties may be realized. Here, we describe the synthesis and characterization of anthracene-containing organic-inorganic hybrid materials for thermoelectric purposes. Specifically, POSS-ANT was synthesized when aminopropylisobutyl-POSS was functionalized with a single anthracene unit via DCC-mediated amide formation. Acrylate-POSS was functionalized with multiple anthracene units in a Heck coupling reaction to synthesize System 1. System 2 was developed through a two-step synthetic process. In the first reaction, (3- acryloxypropyl)methyl dimethyoxy silane was functionalized with anthracene at the 9- position through a Heck coupling reaction. The second reaction was a base-catalyzed solgel process to form polymeric nanoparticles. Finally, System 3 was synthesized through a similar process to System 2, though polymers formed in the initial step. The System 3 precursor was to be developed through a potassium carbonate-catalyzed ether synthesis from 3-(bromopropyl)trimethoxysilane and 9-anthracene methanol, followed by a basecatalyzed sol-gel process to form nanoparticles. The precursor was never isolated because of premature polymerization during the precursor synthesis step, and polymeric nanoparticles were obtained for System 3 during the sol-gel process. These materials were characterized by TEM to reveal the nanostructures that formed upon evaporation from solution. Future work will focus on the characterization of thermoelectric parameters and incorporation into thermoelectric devices.

Aujourd’hui, les énergies renouvelables comme l’énergie éolienne, l’énergie solaire, l’énergie hydroélectrique et la thermoélectricité jouent un rôle essentiel dans la couverture de nos besoins en énergie. Parmi ces différentes sources d’énergie, la thermoélectricité, qui permet de convertir la chaleur en électricité ou inversement, attire une grande attention grâce à son large champ d’application. Les actuelles avancées dans la recherche thermoélectrique visent l’amélioration du rendement de conversion des modules thermoélectriques, à travers l’optimisation des propriétés thermoélectriques intrinsèques des matériaux utilisés (coefficient de Seebeck, conductivité électrique et conductivité thermique). Pour cela, différentes approches ont été étudiées (dopage, nouveau alliages, nanostucturation …). Parmi ces approches, la nanostructration des matériaux a été largement étudiée pour mener à bien cet objectif. Dans ce travail de thèse, nous nous sommes intéressés à étudier l’effet de la nanostructuration de surface des matériaux (silicium mesoporeux et oxyde de titane déposé en couches minces) par faisceaux laser ultra-court (picoseconde et femtoseconde) sur l’évolution de leurs propriétés thermoélectriques. Dans un premier temps, nous nous sommes focalisés sur l’étude des différents phénomènes physiques impliqués durant l’interaction laser-matière ainsi que sur la formation des différentes nanostructures résultantes (en forme de ripples, spikes, dots et autres) en fonction de la dose laser appliquée (la fluence et le nombre de pulses). La formation de ces nanostructures a été étudiée suivant deux régimes (stationnaire et dynamique). Après l’optimisation des paramètres conduisant à la formation de ces nanostructures, la caractérisation du coefficient de Seebeck et la conductivité électrique avant et après la nanostructuration de ces matériaux a été réalisée grâce à un nouveau dispositif de mesure (ZT-meter) développé au laboratoire GREMI. Les résultats de mesures montrent une importante amélioration du coefficient de Seebeck et la conductivité électrique après la nanostrucutration. Un facteur d’augmentation de la puissance thermoélectrique a été observé pour les deux matériaux étudiés ; notamment dans le cas de couches minces d’oxyde de titane (jusqu’à 500 fois). / Today, renewable energies such as wind, solar, hydropower and thermoelectricity play an essential role to cover our energy needs. Among these different sources of energy, thermoelectricity, which offers the ability to convert a heat into electricity or vice versa, has attracted a great attention due to its wide field of potential applications. The current advances in thermoelectric research are focusing on the improvement of the conversion efficiency of thermoelectric devices through optimizing and improving the thermoelectric properties of the thermoelectric materials (Seebeck coefficient, electrical conductivity and thermal conductivity). For this, different approaches (doping, new materials, nanostucturing...) have been investigated in the literature. Among these approaches, nanostructuring of materials is the most studied in the literature in order to improve the thermoelectric properties of materials. In this thesis work, we aimed to study the effect of surface nanostructuring of materials (mesoporous silicon and titanium oxide deposited in thin film) by ultra-short laser beams (picosecond and femtosecond) on the evolution of their thermoelectric properties. First, we focused on the study of various physical phenomena involved during the laser-matter interaction that yield to the formation of very different nanostructures in form of ripples, spikes, dots and others as function of the applied laser dose (fluence and number of pulses). The formation of these nanostructures has been studied in two regimes (stationary and dynamic). After optimizing the laser parameters leading to the formation of such nanostructures, a characterization of Seebeck coefficient and the electrical conductivity before and after the nanostructuring of these materials was carried out by using a new experimental setup (ZT-meter) designed and validated in GREMI laboratory. The results of measurements showed an important improvement of Seebeck coefficient and electrical conductivity after nanostructuring. This important improvement observed with the both materials leaded to a strong increase in the thermoelectric power factor (reaching roughly 50000%).

Les gaz contenus dans les lignes d’échappement des moteurs Diesel pour la propulsion maritime peuvent atteindre des températures de l’ordre de 400 – 450 °C à la sortie du turbocompresseur. Une des voies possibles pour récupérer une partie de l’énergie contenue dans les gaz d’échappement est la thermoélectricité (effet Seebeck)avec des matériaux thermoélectriques côté chaud entre200 et 300 °C. Ce niveau de température correspond à des matériaux ayant de bonnes performances de conversion chaleur / électricité. De plus, l’eau de mer présente en abondance est une excellente source froide pour un générateur thermoélectrique (TEG). Par ailleurs, la consommation en carburant du moteur thermique est un poste de dépense majeure pour l’opérateur du bateau, et une réduction de cette consommation, même minime, peut générer des économies financières importantes.L’objectif de la thèse est de comprendre et analyser le fonctionnement d’un échangeur thermoélectrique,notamment en présence d’écoulement pulsés afin d’optimiser le fonctionnement du générateur thermoélectrique. A ce titre, plusieurs campagnes d’essais sur des maquettes de TEG ont été mises en place sur trois bancs d’essais (conçus particulièrement pour les travaux de thèse) où des mesures thermiques et électriques ont été réalisées. Le but de ces essais a été de tester les performances des modules thermoélectriques et les différents types d’échangeurs sur les points de fonctionnement d’un moteur Diesel pour déterminer (dans un premier temps) lesquels étaient les plus adaptés au fonctionnement moteur. Dans un second temps, les effets de la composition des gaz d’échappement et des écoulements pulsés sur le fonctionnement du TEG ont été étudiés. Un modèle de simulation a également été développé afin de modéliser le fonctionnement d’un générateur thermoélectrique. Des essais ont été réalisés afin de calibrer le modèle de simulation. / Thermoelectric energy (TE) harvesting (Seebeck effect)is a promising solution for waste heat recovery onboard ocean-going ships. On one hand, the marine Diesel engines reach around 400-450°C temperature at the turbocharger exhaust, corresponding to around 200-300°C on the hot side thermoelectric module (TEM)temperature, which is interesting according to recent studies on intermediate temperatures TE materials. In addition, seawater is available in abundance at low temperature, and represents an excellent heat sink. On the other hand, engine fuel consumption accounts today almost 50 % of ship operational costs; hence, a slight reduction of fuel consumption generates significant financial savings over the year.The objective of the Thesis is to understand and analyze the operation of a thermoelectric heat exchanger, especially in the presence of pulsations and to optimize the thermoelectric generator (TEG). Several test campaigns leading to different thermal and electrical measurement have been conducted. The campaigns were set up on three different test benches designed and fabricated during the thesis. The aim of these tests was to optimize the type of TEM’s and heat exchangers for Diesel engine application by investigating it’s the performances on engine operating points. In a second step, the effects of exhaust gas composition and pulsation flow on the TEG performances were investigated. A simulation model was developed to model the operation of a TEG. Tests were conducted to calibrate the simulation model.