Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-06-28T19:58:26Z No. of bitstreams: 1 FICHA_CATALOGR?FICA_EMBUTIDA_Disserta??o Cristiano_Jaeger Stradolini_Processo Poliol.pdf: 3080490 bytes, checksum: 6539be3aad396dd1f8b30cd3389b1469 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-07-06T13:07:04Z (GMT) No. of bitstreams: 1 FICHA_CATALOGR?FICA_EMBUTIDA_Disserta??o Cristiano_Jaeger Stradolini_Processo Poliol.pdf: 3080490 bytes, checksum: 6539be3aad396dd1f8b30cd3389b1469 (MD5) / Made available in DSpace on 2018-07-06T13:12:44Z (GMT). No. of bitstreams: 1 FICHA_CATALOGR?FICA_EMBUTIDA_Disserta??o Cristiano_Jaeger Stradolini_Processo Poliol.pdf: 3080490 bytes, checksum: 6539be3aad396dd1f8b30cd3389b1469 (MD5) Previous issue date: 2018-03-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / During the past few years, nanosized noble metals have attracted much attention due to their unique electrical and physical properties. Among them, silver has been the subject of several studies, by having the highest electrical and thermal conductivity between all metals. For that reason, its one-dimensional nanometric structure (nanowires) has been receiving a lot of attention, due to its potential in the manufacture of devices that offer good electrical conduction and optical transparency. There are several methods of synthesis for the production of these silver nanowires, however the most widely used is the polyol process, due to its simplicity and low cost. Several studies show the influence of different parameters of the polyol process (reaction time, temperature and etc.) on the final morphology of the nanowires. Thus, a well-defined protocol of good practice for obtaining long and thin silver nanowires is required. The main objective of this work is the development of a low cost protocol capable of generating nanowires with great lengths by modifying the polyol process parameters. Variations were also performed in the method of addition of the main synthesis reagent, silver nitrate, and its influence on the final morphology of the silver nanowires was studied. In this work, by using the polyol process, nanowires up to 40 ?m in length were reported, demonstrating the effectiveness of the developed technique and conclusions about the final results were presented. / Ao decorrer dos ?ltimos anos, metais nobres na escala nanom?trica t?m atra?do muita aten??o, devido as suas propriedades el?tricas e f?sicas ?nicas. Dentre eles, a prata vem sendo alvo de diversos estudos, por possuir a maior condutividade el?trica e t?rmica entre todos os metais. Por conta disto, sua estrutura nanom?trica unidimensional (nanofios) vem recebendo muita aten??o, pelo seu potencial na fabrica??o de dispositivos que exijam alta condutividade el?trica e transpar?ncia ?ptica. Atualmente, existem diversos m?todos de s?nteses para a produ??o destes nanofios de prata, por?m o mais utilizado ? o processo poliol, por ser simples e de baixo custo. Diversos estudos demonstram a influ?ncia de diferentes par?metros do processo poliol (tempo de rea??o, temperatura e etc.) sobre a morfologia final dos nanofios. Assim, se faz necess?rio um protocolo bem definido de boas pr?ticas para a obten??o de fios longos e finos. O principal objetivo deste trabalho ? o desenvolvimento de um protocolo de baixo custo capaz de gerar nanofios com grandes comprimentos, atrav?s de altera??es nas vari?veis do processo poliol, como, por exemplo, varia??es no m?todo de adi??o do principal reagente da s?ntese, o nitrato de prata. Foi estudada a sua influ?ncia na morfologia final dos nanofios. Neste trabalho, os resultados finais apresentaram que nanofios de at? 40 ?m de comprimento foram produzidos pelo processo poliol, demonstrando a efic?cia da t?cnica desenvolvida e foram apresentadas as conclus?es acerca dos resultados atingidos.

O grafeno, material com duas dimensões (2D), formado por átomos de carbono hibridizados em sp2, tem atraído muita atenção da comunidade científica devido às propriedades elétricas, térmicas e mecânicas excepcionais que este material apresenta. Nanopartículas (NPs) de metais e de óxidos metálicos têm sido incorporadas sobre a estrutura do grafeno com o objetivo de obter materiais compósitos. Este trabalho teve por objetivo principal desenvolver uma nova rota para a preparação de compósitos de grafeno/NPs metálicas e de óxidos metálicos pelo método do poliol modificado, em etapa única. O óxido de grafeno (GO) foi sintetizado pelo método Hummers modificado e reduzido e esfoliado pelo processo pioliol modificado para obtenção do grafeno. Ajustou-se a metodologia proposta para que o GO obtido pudesse ser utilizado diretamente no meio reacional do processo poliol sem a necessidade de secagem e redispersão. Foram testadas diversas condições de síntese do grafeno variando-se a presença e tipo de surfactante, o solvente e diferentes condições de aquecimento. As variações de síntese permitiram observar que a presença do surfactante oleilamina aumenta a capacidade redutora do sistema e inibe a formação de outras estruturas de carbono além do grafeno e taxas de aquecimento menores favorecem a formação de grafeno em detrimento destas outras estruturas, enquanto patamares de temperatura intermediários levam à formação dessas estruturas secundárias de carbono. As sínteses foram também adaptadas para a obtenção de compósitos de grafeno/NPs de FePt e Fe3O4. Estas sínteses foram realizadas de duas maneiras: com os precursores metálicos e o GO presentes no balão desde o início da síntese e com os precursores metálicos presentes no balão desde o início da síntese e hot injection do GO. Para os compósitos, as sínteses realizadas em benzil éter (BE) favoreceram a formação de partículas. Para os compósitos de grafeno/NPs de Fe3O4, observou-se que a quantidade de precursor de Fe é crucial para a formação das NPs. Os resultados indicaram que a metodologia empregada foi muito eficiente para produção de grafeno e de compósitos de grafeno/NPs em etapa única e o processo poliol se mostrou muito versátil, de maneira que os resultados obtidos indicam que é possível obter compósitos de grafeno com qualquer sistema de NPs que venham a ser sintetizadas pelo processo poliol, apenas pelo ajuste das condições de síntese, em etapa única. / Graphene, a two dimensional material, composed only by sp2 hybridized carbon atoms, have attracted much attention of the scientific comunity due to the exceptional electrical, thermal and mechanical properties this material presents. Metallic and metal oxide nanoparticles (NPs) have been incorporated over graphene structure in order to obtain composite materials. The main goal of this work was to develop a new synthetic route to obtain graphene and metallic and metal oxide NPs composites, in one step. Graphene oxide (GO) was sinthesized by the modified Hummers method and exfoliated and reduced by the modified polyol process to obtain graphene. The proposed methodology was adjusted for the obtained GO to be used directly in the polyol process reactional means, not being necessary to dry and to redisperse the material. Several synthesis conditions were tested to obtain graphene, varying the presence of the surfactant and its type, solvent and heating rates. The synthesis diversity let us observe that the presence of oleylamine improved the reducing capacity of the system and it inhibited other carbon structures formation besides graphene. Also, smaller heating rates favor graphene formation to the detriment of these other structures, whereas intermediate temperature plateaus lead to the formation of carbon secondary structures. The synthesis were also adapted in order to obtain graphene/NPs of FePt and Fe3O4 composites. These synthesis were performed in two ways: both metallic precursors and GO present in the flask since the begining of the synthesys and only methalic precursors present in the flask since the begining of the synthsys, with a GO hot injection. Regarding the composites, synthesis performed in benzyl ether (BE) favor the particles formation. And specifically on the graphene/NPs of Fe3O4 composites, it was observed that Fe precursor quantity is decisive on the NPs formation. The results indicated that the employed methodology was very efficient to produce graphene and graphene/NPs composites in one step. And the polyol process proved to be very versatile, thereby the obtained results indicate it\'s possible to obtain graphene/NPs composites, in one step, with any NPs system that can be synthesized by the polyol process, only by adjusting the synthesis condition.

Nanotechnology enabled synthesis of various shapes and morphologies of conventional materials. Nanotubes, nanoparticles, quantum dots and nanowires are the new form of materials. Especially nanowires have gotten great attention due to their unique physical, chemical and optical properties. Superior properties of nanowires are based on their high surface area and two quantum confinement directions. Silver is one of the most conductive metals and it has the highest thermal conductivity. Due to excellent properties of bulk silver its nanostructures especially silver nanowires have been widely studied. Silver nanowires have been demonstrated to be used in optical polarizers, photonic crystals, surface enhanced Raman spectroscopy and recently transparent and conducting electodes. Hence, production of silver nanowires through a cost-effective and well controlled method could make important contributions to these and other unprecedented. So far, many different methods have been explored for the synthesis of silver nanowires. Vapor-liquid-solid (VLS) technique, hard template techniques such as porous anodic alumina synthesis and soft template techniques such as DNA based synthesis and polyol process are some silver nanowire synthesis methods. Among these methods, solution based polyol process is the most feasible one in terms of cost, yield and simplicity. In this thesis, polyol process, which is a novel and solution based method enabling the synthesis of silver nanowires with precise length and diameter control, is investigated. A detailed parametric study resulting in a full control over the resultant nanowire morphology is provided. The parameters affecting the structure have been determined as temperature, injection rate, poly(vinylpyrrolidone):silver nitrate (PVP:AgNO3) molar ratio, sodium chloride (NaCl) amount and stirring rate. The results show that polyol process method could replace the conventional silver nanowire fabrication methods. It was shown that specific nanowire lengths and diameters for any application can be obtained simply by adjusting the parameters of the process.

O grafeno, material com duas dimensões (2D), formado por átomos de carbono hibridizados em sp2, tem atraído muita atenção da comunidade científica devido às propriedades elétricas, térmicas e mecânicas excepcionais que este material apresenta. Nanopartículas (NPs) de metais e de óxidos metálicos têm sido incorporadas sobre a estrutura do grafeno com o objetivo de obter materiais compósitos. Este trabalho teve por objetivo principal desenvolver uma nova rota para a preparação de compósitos de grafeno/NPs metálicas e de óxidos metálicos pelo método do poliol modificado, em etapa única. O óxido de grafeno (GO) foi sintetizado pelo método Hummers modificado e reduzido e esfoliado pelo processo pioliol modificado para obtenção do grafeno. Ajustou-se a metodologia proposta para que o GO obtido pudesse ser utilizado diretamente no meio reacional do processo poliol sem a necessidade de secagem e redispersão. Foram testadas diversas condições de síntese do grafeno variando-se a presença e tipo de surfactante, o solvente e diferentes condições de aquecimento. As variações de síntese permitiram observar que a presença do surfactante oleilamina aumenta a capacidade redutora do sistema e inibe a formação de outras estruturas de carbono além do grafeno e taxas de aquecimento menores favorecem a formação de grafeno em detrimento destas outras estruturas, enquanto patamares de temperatura intermediários levam à formação dessas estruturas secundárias de carbono. As sínteses foram também adaptadas para a obtenção de compósitos de grafeno/NPs de FePt e Fe3O4. Estas sínteses foram realizadas de duas maneiras: com os precursores metálicos e o GO presentes no balão desde o início da síntese e com os precursores metálicos presentes no balão desde o início da síntese e hot injection do GO. Para os compósitos, as sínteses realizadas em benzil éter (BE) favoreceram a formação de partículas. Para os compósitos de grafeno/NPs de Fe3O4, observou-se que a quantidade de precursor de Fe é crucial para a formação das NPs. Os resultados indicaram que a metodologia empregada foi muito eficiente para produção de grafeno e de compósitos de grafeno/NPs em etapa única e o processo poliol se mostrou muito versátil, de maneira que os resultados obtidos indicam que é possível obter compósitos de grafeno com qualquer sistema de NPs que venham a ser sintetizadas pelo processo poliol, apenas pelo ajuste das condições de síntese, em etapa única. / Graphene, a two dimensional material, composed only by sp2 hybridized carbon atoms, have attracted much attention of the scientific comunity due to the exceptional electrical, thermal and mechanical properties this material presents. Metallic and metal oxide nanoparticles (NPs) have been incorporated over graphene structure in order to obtain composite materials. The main goal of this work was to develop a new synthetic route to obtain graphene and metallic and metal oxide NPs composites, in one step. Graphene oxide (GO) was sinthesized by the modified Hummers method and exfoliated and reduced by the modified polyol process to obtain graphene. The proposed methodology was adjusted for the obtained GO to be used directly in the polyol process reactional means, not being necessary to dry and to redisperse the material. Several synthesis conditions were tested to obtain graphene, varying the presence of the surfactant and its type, solvent and heating rates. The synthesis diversity let us observe that the presence of oleylamine improved the reducing capacity of the system and it inhibited other carbon structures formation besides graphene. Also, smaller heating rates favor graphene formation to the detriment of these other structures, whereas intermediate temperature plateaus lead to the formation of carbon secondary structures. The synthesis were also adapted in order to obtain graphene/NPs of FePt and Fe3O4 composites. These synthesis were performed in two ways: both metallic precursors and GO present in the flask since the begining of the synthesys and only methalic precursors present in the flask since the begining of the synthsys, with a GO hot injection. Regarding the composites, synthesis performed in benzyl ether (BE) favor the particles formation. And specifically on the graphene/NPs of Fe3O4 composites, it was observed that Fe precursor quantity is decisive on the NPs formation. The results indicated that the employed methodology was very efficient to produce graphene and graphene/NPs composites in one step. And the polyol process proved to be very versatile, thereby the obtained results indicate it\'s possible to obtain graphene/NPs composites, in one step, with any NPs system that can be synthesized by the polyol process, only by adjusting the synthesis condition.

Grâce aux développements des méthodes de synthèse et de caractérisation, les nanomatériaux constituent un champ d'investigation de plus en plus actif et attractif. Cette thèse s'attache à étudier un procédé de synthèse de nanoparticules d’oxyde de zinc par voie polyol. Ce procédé a l’avantage de fournir une large variété morphologique de particules présentant une bonne qualité cristalline. Dans cette thèse, nous montrons qu’en variant les paramètres de synthèse nous pouvons moduler la taille, la distribution de taille et la morphologie des nanoparticules pour les obtenir en forme de nanosphères aussi fines que 6 nm ou des nanofils aussi longs que600 nm. Notre étude systémique a porté sur un ensemble de paramètres qui contrôlent la réaction d’hydrolyse forcée incluant la stoechiométrie, la température, la nature du polyol mais également l’agitation, l’injection des réactifs et l’activation par ultra sons du milieu. Nous montrons que la forme des nanoparticules est déterminée par la compétition entre les réactions de croissance de différentes faces du cristal d’oxyde de zinc. Notre étude a permis aussi de comparer différents dispositifs de mélange comme le réacteur du laboratoire, le T de mélange et les jets libres. Par ailleurs, pour produire en masse ces nano objets nous avons développé une stratégie originale pour comprendre l’effet du mélange sur la taille des nanoparticules. Notre approche s’appuie sur la résolution numérique des équations de Navier-Stokes et la corrélation entre les profils d’énergie turbulente dissipée et la taille des nanoparticules mesurée expérimentalement. L’application au cas spécifique de l’oxyde de zinc nous a permis de produire jusqu’à ~50 g de nanoparticules par Batch. Ces nanoparticules ont par la suite été incorporées comme matériau semi conducteur dans des cellules photovoltaïques à colorant préparées à l’École Nationale Supérieure de Chimie de Paris. En effet, la richesse morphologique de ZnO obtenu par voie polyol laisse présager une bonne adsorption du colorant à sa surface. Nos résultats montrent que les rendements de photoconversion dépendent aussi bien de la morphologie que de la taille. Les meilleures cellules élaborées dans cette thèse ont un rendement qui avoisine 5.3 %. / Thanks to developments in synthesis methods and characterization techniques, nanomaterials research field is increasingly active and attractive. This thesis aims to investigate the polyol process for zinc oxide nanoparticles synthesis. Indeed, this method has the advantage of providing a wide variety of particle morphology with a good crystalline quality. In this thesis, we show that by varying the synthesis conditions we can adjust the size, the size distribution and the morphology of nanoparticles to obtain either shaped nanospheres as small as 6 nm or nanowires as long as 600 nm. Our systemic study focused on a set of parameters that control the forced hydrolysis reaction including stoichiometry, temperature, nature of the polyol but also mixing, injection of reagents and ultrasound activation. We show that the shape of the nanoparticles is determined by the competition between growth rates of different zinc oxide crystal facets. Our study also compared different mixing devices such as laboratory reactor, T- mixer and impinging jets. More over, to mass produce zinc oxide nanoparticles, we developed an original strategy to understand the effect of mixing on nanoparticle size. In our approach, we correlate the turbulent energy dissipated as obtained from Computation Fluid Dynamics with theme asured nanoparticle size. The application to the specific case of zinc oxide has allowed us to produce sample aliquots of ~50 g per Batch. These nanoparticles were subsequently incorporated into dye-sensitized solar cells as semi conducting material at the École Nationale Supérieure de Chimie de Paris. Indeed, the morphological richness of the zinc oxide produced via polyol process suggests good adsorption of the dye on their surfaces. Our results show that the photoconversion efficiencies depend both on the morphology and the size. Our best photoconversion efficiency approaches 5.3%.

Lithium iron phosphate (LiFePO4) is one of the most promising cathode materials for lithium ion rechargeable batteries. It has a high theoretical specific capacity (170 mAh/g) and operating potential (3.45 V vs. Li+/Li). Additionally, the material is extremely stable thermally and electrochemically at ambient conditions, which is very suitable to be used in electric vehicles. However, the electronic and ionic conductivities of the material are quite low, which limits the power performance of the batteries. In the last decade, extensive work was reported on various methods to improve the electronic conductivity extrinsically, for example carbon coating, metallic additives and molecular wiring. Nevertheless, energy density of the cells will be reduced because of non-electrochemically active nature of the additives. In principle, electronic and ionic conductivities can be boosted intrinsically. One of the methods is to increase the number of charge carriers in the material, for instance in two-phase solid solution system LiαFePO4/Li1-βFePO4 or single solid solution phase LixFePO4. Since the formation of solid solution has been reported to be size dependent, it is highly desired to know how to synthesize LiFePO4 particles with different sizes. In this study, we have used hydrothermal synthesis and polyol process to control the size of LiMPO4 (M: Fe, Mn, and Co) particles. We will present how we prepare particles with different sizes. Moreover, the solid solution properties of various sizes of LiMPO4 (M: Mn and Fe) were studied. The result will be presented. Part of the preliminary findings have been published in the peer-reviewed journals or conference presentations: 1) Journal of Materials Chemistry [Ellis B.; Kan W. H.; Makahnouk W. R. M.; Nazar L. F. J. Mater. Chem. 2007, 17 (30) 3248., 2) Journal of the American iv Chemical Society [Lee K. T.; Kan W. H.; Nazar L. F. J. Am. Chem. Soc. (submitted)], 3) Material Research Society Meeting [Kan W. H.; Maunders C.; Badi S.; Ellis B.; Botton G.; Nazar L. F. MRS Fall Meeting 2008 in Boston]

Lithium iron phosphate (LiFePO4) is one of the most promising cathode materials for lithium ion rechargeable batteries. It has a high theoretical specific capacity (170 mAh/g) and operating potential (3.45 V vs. Li+/Li). Additionally, the material is extremely stable thermally and electrochemically at ambient conditions, which is very suitable to be used in electric vehicles. However, the electronic and ionic conductivities of the material are quite low, which limits the power performance of the batteries. In the last decade, extensive work was reported on various methods to improve the electronic conductivity extrinsically, for example carbon coating, metallic additives and molecular wiring. Nevertheless, energy density of the cells will be reduced because of non-electrochemically active nature of the additives. In principle, electronic and ionic conductivities can be boosted intrinsically. One of the methods is to increase the number of charge carriers in the material, for instance in two-phase solid solution system LiαFePO4/Li1-βFePO4 or single solid solution phase LixFePO4. Since the formation of solid solution has been reported to be size dependent, it is highly desired to know how to synthesize LiFePO4 particles with different sizes. In this study, we have used hydrothermal synthesis and polyol process to control the size of LiMPO4 (M: Fe, Mn, and Co) particles. We will present how we prepare particles with different sizes. Moreover, the solid solution properties of various sizes of LiMPO4 (M: Mn and Fe) were studied. The result will be presented. Part of the preliminary findings have been published in the peer-reviewed journals or conference presentations: 1) Journal of Materials Chemistry [Ellis B.; Kan W. H.; Makahnouk W. R. M.; Nazar L. F. J. Mater. Chem. 2007, 17 (30) 3248., 2) Journal of the American iv Chemical Society [Lee K. T.; Kan W. H.; Nazar L. F. J. Am. Chem. Soc. (submitted)], 3) Material Research Society Meeting [Kan W. H.; Maunders C.; Badi S.; Ellis B.; Botton G.; Nazar L. F. MRS Fall Meeting 2008 in Boston]

Intermetallic compounds are highly investigated, as they combine or enhance the properties of their constituting elements or even bring forth new properties. Especially at the nanoscale, these features can be exploited in heterogeneous catalysis.[1] Various methods have been developed so far to synthesize intermetallic particles, each with its own benefits and drawbacks. A facile procedure is the polyol process, which was first introduced by the group of FIÉVET and FIGLARZ in 1989. Here, the polyol serves a threefold purpose. First, it serves as the primary solvent. With respect to metal salts, it displays a solvation behavior similar to water due to the chelating properties. Second, the polyol can act as a surface-capping agent, which prevents agglomeration, resulting in finely dispersed particles. Third and last, the main attribute of the polyol is its reductive property, which increases with temperature, enabling the reduction of multiple metal cations. Compared to other synthetic routes, the polyol process can be performed with cheap starting materials, such as metal salts or oxides. The utilization of a laboratory microwave can further improve the process. A homogeneous heat distribution and contactless heating diminish side reactions. Additionally, the extreme heating rates foster homogeneous nucleation, resulting in a uniform product. Furthermore, the precise control over the temperature profile enables good reproducibility, making this setup ideal for efficient syntheses as well as investigations of reaction pathways. In this PhD thesis, formation mechanisms of Bi-M particles (M = Ni, Ir, Rh; ) were elucidated, revealing different mechanisms depending on the metal combination as well as various intermediates. Additionally, the influence of reaction parameters, such as metal precursor, anion, and pH value was investigated. In the case of BiNi particle formation, a successive reduction of bismuth and nickel cations was observed. Bismuth cations are reduced first producing bismuth particles, which act as nucleation sites for the subsequent nickel reduction. The particles grow on the surface of the bismuth core resulting in a core-shell structure. Diffusion of nickel results in Bi3Ni and eventually BiNi after full depletion of the nickel shell. The choice of nickel precursor substantially influences the required reaction time. Nickel acetate requires the shortest reaction time, whereas nickel nitrate necessitates drastically longer reaction times due to a decreased reductivity. Nickel chloride is not reducible in neat ethylene glycol due to the formation of a stable dinuclear nickel complex in solution. The overall formation kinetics are substantially promoted by increasing the pH value or temperature, leading to a higher reduction strength or improved diffusion dynamics, respectively. The study of Bi2Ir particle formation revealed a two-stage scenario. First, the starting materials are partially co-reduced to the new intermetallic suboxide Bi4Ir2O. In a second step, at higher temperatures, the suboxide is fully reduced to Bi2Ir. So far, only the combination of bismuth nitrate and iridium acetate results in the suboxide, whereas the introduction of chloride ions, i.e., iridium chloride or potassium hexachloroiridate, merely results in BiOCl and elemental iridium. A structural model of Bi4Ir2O was established based on diffraction data and quantum chemical calculations. Edge-sharing [IrBi6] octahedra form corrugated layers stacked along the c-axis, which are separated by oxide ions. The calculated band structure and DOS suggest metallic behavior within the layers, whereas a band gap was found along the stacking order, thus, making the compound a pseudo 2D metal.The formation of Bi2Rh particles follows a two-step mechanism. For rhodium acetate, the process starts with a direct co-reduction of rhodium and bismuth cations resulting in the formation of BiRh. Increasing the temperature further leads to a gradual transition into Bi2Rh via reduction of residual bismuth cations in solution followed by diffusion. In the case of rhodium nitrate, a bismuth-glycolato complex precipitates, which undergoes a reaction with rhodium at high temperatures. The addition of a base promotes the reactions by lowering the necessary reduction temperatures and preventing the precipitation of the bismuth glycolate. Rhodium chloride does not yield intermetallic phases in the desired purity and yield. These results allowed for a comparison and assessment of reactions in the synthesis of γ-BiPd particles. Similar to the above discussed reactions, chlorides resulted in the formation of BiOCl. An increased pH value was beneficial by preventing precipitation of intermediates, i.e., BiOCl or bismuth glycolates, and improved reduction strength.

L’étude de ce mémoire concerne l’élaboration d'un alliage alternatif sans plomb pour l’électronique de puissance, celui-ci sera utilisé à des fins de brasures. Les brasures actuelles sont composées d’alliages comportant du plombet sont peu résistantes en cas de travail à haute température. Ces systèmes seront progressivement éliminés, ils ne respectent plus la Directive Européenne sur l’environnement (RoHS) et les normes de santé publique en raison de la toxicité du plomb (cancérogène, mutagène, accumulation dans l’environnement …). Le travail a été réalisé avec l’alliage Ag-Sn, l’objectif principal de cette thèse a été d’élaborer le composé Ag3Sn, en raison de sa grande résistance thermique (température de fusion élevée de 480°C). Ses meilleures performances sont avantageuses pour les brasures situées dans des environnements difficiles comme l’aéronautique ou l’automobile. La première partie de ce manuscrit détaille la synthèse du composé Ag3Sn réalisée via la méthode polyol, une voie de chimie douce. Il s’agit d’une technique différente des techniques classiques, comme la voie métallurgique. La synthèse a été réalisée en plusieurs étapes et une méthode d’approches successives a été utilisée afin de déterminer les paramètres de synthèse optimums.Deux protocoles particuliers se détachent et ils permettent d’élaborer des phases résistantes à haute température. Lepremier permet d’élaborer une phase pure d' Ag3Sn, tandis que le second permet d’élaborer deux phases de solutionssolides. Les composés ont été caractérisés par DRX, par imagerie MEB-FEG et MET et par analyse thermogravimétrique.La seconde partie de ce travail est la consolidation de ce composé Ag3Sn par une technique de frittage particulière :le die-bonding, afin de réaliser la connexion entre la puce électronique et un susbtrat de cuivre recouvert d'argent.Une étape de dépôt des poudres sur le substrat a été nécessaire avant de réaliser la consolidation, elle a été réalisée selon différentes techniques : le spin-coating ou le dépôt par sérigraphie. Puis, les paramètres de frittage par die-bonding ont été affinés selon les techniques de dépôt. Enfin, des essais de cisaillement ont été réalisés sur certains échantillons. / The study of this memoir concerns the development of an alternative lead-free alloy for power electronics, which will be used for solders. Nowadays, current solders are composed of alloys containing lead, and aren't resistant at high work temperature. These systems will be phased out, because they no longer comply with the European RoHS Directive and public health standards due to the toxicity of lead (carcinogenic, mutagenic, accumulation in the environment, etc.). This work was carried out with the Ag-Sn alloy, and the main objective was to develop the elaboration of the Ag3Sn compound, due to its high thermal resistance (high melting point of 480°C). Its best performance is an advantage for solders located in difficult work environments such as aeronautics or automobile. First part of this thesis describes the synthesis of Ag3Sn compound with the polyol process, a soft-chemistry routine. It is different from the conventional techniques, like the metallurgical way. Polyol synthesis was realized by following several steps. A method of successive approaches wasdetermine optimum synthesis parameters. Two specific protocols stand out, and they allow the development of high-temperature resistant phases. The first one allows the elaboration of an Ag3Sn pure phase, an the second one allows the development of two compounds of solid solutions. The compounds were characterized by XRD, FEG-SEM, TEM and thermogravimetric analysis. The second part of this work is the consolidation of the Ag3Sn compound with a special sintering technique : the die-bonding, in order to realize the connexion between the electronic chip and the copper substrate coated silver. A first step of depositing powder on the substrate was necessary before carrying out the implementation. It was carried out with various techniques : spin-coating orthe serigraphy deposition. Then, sintering parameters were refined according to the deposition techniques. Finally, shear tests were performed on different samples

The work of this dissertation is centered on two non-conventional synthetic approaches to ferromagnetic nanomaterials: high-throughput experimentation (HTE) (polyol process) and continuous flow (CF) synthesis (aqueous reduction and the polyol process). HTE was performed to investigate phase control between FexCo1-x and Co3-xFexOy. Exploration of synthesis limitations based on magnetic properties was achieved by reproducing Ms=210 emu/g. Morphological control of FexCo1-x alloy was achieved by formation of linear chains using an Hext. The final study of the FexCo1-x chains used DoE to determine factors to control FexCo1-x, diameter, crystallite size and morphology. [Ag] with [Metal] provide statistically significant control of crystallite size. [OH]/[Metal] predict 100 % FexCo1-x at > 30. To conclude section 1, a morphological study was performed on synthesis of Co3-xFexOy using the polyol process. Co3-xFexOy micropillars were synthesized at various sizes. The close proximity of the particles in the nanostructure produced an optical anisotropy and was magnetically induced which is evidence for the magneto-birefringence effect. The second non-conventional synthetic approach involves continuous flow (CF) chemistry. Co nanoparticles (Ms=125 emu/g) were newly synthesized by aqueous reduction in a microreactor and had 30 ±10 nm diameter and were produced at >1g/hr, a marker of industrial-scale up viability. The final work was the CF synthesis of FexCo1-x. The FexCo1-x was synthesized with limitation to the composition. The maximum FexCo1-x phase composition at 20 % resulted from the aqueous carrier solvent triggering oxide formation over FexCo1-x.