Le « Frittage Flash » ou « Spark Plasma Sintering (SPS) » est utilisé pour consolider des poudres en des temps relativement courts (quelques minutes). Ce procédé utilise un haut courant continu pulsé (quelques kA), traversant les parties conductrices du système et générant une montée rapide en température induite principalement par effet Joule. L’application d’un chargement mécanique, via des pistons, et d’une rapide montée en température permet d’obtenir une pièce dense sans grossissement excessif des grains. L’objectif de ce travail a été de proposer une simulation numérique thermo-électro-mécanique du procédé « Frittage Flash » sur ABAQUS, afin de suivre in situ les évolutions de température, de porosité et des contraintes difficilement accessibles expérimentalement. Dans ce travail, un modèle de comportement des corps poreux est proposé. Cette approche est basée sur les modèles micromécaniques de la littérature et modifiés de manière heuristique pour reproduire la densification réelle du matériau pour des porosités comprises entre 0 et 50%. Les simulations thermo-électro-mécanique incluant ce modèle, intègrent la dépendance en porosité et température des paramètres matériaux. Quatre cycles d’élaboration de poudre de nickel ont été réalisés avec différentes histoires de température. Les évolutions de la température et de la porosité calculées ont été confrontées avec des résultats expérimentaux. Des analyses post mortem sur des échantillons densifiés confortent la distribution de la température obtenue par le calcul. Ce travail ouvre de nombreuses perspectives, notamment, la possibilité d’optimiser le procédé / Nowadays, Spark Plasma Sintering (SPS) is used to consolidate powders in a relative short time (few minutes). This process uses a pulsed high DC electrical current (few kA) which flows through the conductive part of the device and generates large heating rate mainly due to Joule effect. The application of an uniaxial pressure via punches combined with a rapid heating allow the production of near net shape specimen. The thermal electrical mechanical numerical simulation of SPS process is a powerful tool to capture in situ evolutions of temperature, porosity and stresses which are difficult to obtain in experiments. In this work, a new constitutive model is presented for the description of the behavior of porous medium. This model is based on original viscoplastic micromechanical models of the literature and modified in a heuristic manner to better reproduce the real densification of sintered material for porosity in the range [0;0,5]. The model has been implemented in ABAQUS software. A thermal electrical mechanical simulation of SPS is performed where the dependence of material parameters on temperature and porosity is taken into account. Four processing cycles of nickel have been conducted with different temperature histories. Calculated porosity and temperature evolutions are compared to experimental results. Post-mortem analyses of the material (grain size, yield stress) confirm the temperature distribution obtained by numerical simulations in the sample made of nickel. This simulation is seen to be able to capture experimental trends. The work will permit in a near future the optimization of the sintering conditions to reach prescribed properties

Os compósitos cerâmicos de alto desempenho têm sido objeto de frequentes estudos nas últimas décadas, visando à melhora das propriedades mecânicas e ao aumento da sua gama de aplicações em produtos tecnológicos. Este trabalho consistiu em estudar a preparação, a sinterização convencional e não convencional e as propriedades mecânicas e tribológicas resultantes de dois sistemas compósitos: t-ZrO2/Al2O3 e t-ZrO2/Al2O3-NbC. No sistema t-ZrO2/Al2O3 foram estudadas as composições de 0, 5 e 15% em volume de Al2O3 usando pós comerciais. No sistema t-ZrO2/Al2O3-NbC, foi usado um pó nanocristalino de Al2O3-NbC, obtido por moagem reativa de alta energia e adicionado na proporção de 5% em volume à matriz de t-ZrO2. Os pós foram prensados uniaxial e isostaticamente e sinterizados em forno convencional e pelas técnicas de flash sintering (FS) (t-ZrO2/Al2O3) e spark plasma sintering (SPS) (t-ZrO2/Al2O3-NbC). Os compósitos t-ZrO2/Al2O3 sinterizados convencionalmente e t-ZrO2/Al2O3-NbC sinterizados convencionalmente e por SPS foram caracterizados por medidas de densidade aparente, dilatometria, microscopia eletrônica de varredura (MEV), e medidas de propriedades mecânicas: dureza, módulo de Young e tenacidade à fratura. Os compósitos t-ZrO2/Al2O3 sinterizados por FS foram caracterizados por medidas de densidade aparente, dilatometria in situ e MEV. Os nanocompósitos de t-ZrO2/Al2O3-NbC foram também caracterizados quanto à resistência ao desgaste pelo método esfera-no-disco, utilizando esferas de Al2O3 e WC-6%Co como contramateriais. Os resultados mostraram que a moagem reativa de alta energia foi completa e efetiva na obtenção de pós nanométricos de Al2O3-NbC, com tamanhos de cristalito de 9,1 nm para Al2O3 e 9,7 nm para o NbC. A desaglomeração posterior à moagem de alta energia foi eficaz na redução do tamanho de aglomerados. Os compósitos t-ZrO2/Al2O3 e t-ZrO2/Al2O3-NbC sinterizados convencionalmente e ZrO2/Al2O3-NbC sinterizados por SPS mostraram alta densificação (>97% DT e boas propriedades mecânicas. Os nanocompósitos de t-ZrO2/Al2O3 sinterizados por FS apresentaram uma densificação ultrarrápida (< 1 min) com retração linear superior às amostras sinterizadas em forno convencional, ocorrente a temperaturas inferiores a 1000°C, com densidades relativas superiores a 90% DT em algumas composições. Os nanocompósitos de t-ZrO2/Al2O3-NbC apresentaram propriedades competitivas entre os compósitos sinterizados convencionalmente e por SPS, com dureza e tenacidade à fratura superiores às da t-ZrO2 monolítica. A resistência ao desgaste desses nanocompósitos sinterizados convencionalmente, no entanto, foi notadamente superior à dos sinterizados por SPS. A oxidação do NbC nos compósitos sinterizados convencionalmente influiu negativamente nas propriedades, levando à sugestão de uma \"janela\" de temperaturas em que a sinterização do nanocompósito de t-ZrO2/Al2O3-NbC seja interessante sem a degradação das propriedades mecânicas. Os resultados permitiram concluir que os materiais estudados apresentam potencial para aplicações industriais que requerem cerâmicas de alto desempenho mecânico e de resistência ao desgaste. / High performance ceramic composites have been the subject of frequent studies in recent decades, aiming at improving mechanical properties and increasing their range of applications in technological products. This work consisted in studying the preparation, the conventional and non-conventional sintering and the mechanical properties resulting from two t-ZrO2 matrix composites: the t-ZrO2/Al2O3 system and the t-ZrO2/Al2O3-NbC system. In the t-ZrO2/Al2O3 system, the compositions of 0, 5 and 15% by volume of Al2O3 using commercial powders were studied, while in the t-ZrO2/Al2O3-NbC system, an Al2O3-NbC nanocrystalline powder obtained by high energy reactive milling, deagglomerated, leached in HCl and added in the proportion of 5% by volume to the t-ZrO2 matrix. The obtained powders were uniaxially and isostatically pressed and sintered in conventional furnace and using flash sintering (t-ZrO2/Al2O3) and spark plasma sintering (SPS) (t-ZrO2/Al2O3-NbC). Conventionally sintered t-ZrO2/Al2O3 and conventionally sintered t-ZrO2/Al2O3-NbC composites were characterized by measurements of apparent density, dilatometry, SEM, and mechanical properties: hardness, Young\'s modulus and fracture toughness. The t-ZrO2/Al2O3 composites sintered by FS were characterized by measurements of apparent density, in situ dilatometry and SEM. t-ZrO2/Al2O3-NbC nanocomposites were also characterized for wear strength by the ball-in-disc method, using Al2O3 and WC-6%Co beads as countermaterials. The results showed that the high energy reactive milling was complete and effective in obtaining nanometric powders of Al2O3-NbC, with crystallite sizes equal to 9.1 and 9.7 nm, for Al2O3 and NbC, respectively. The deagglomeration after high energy reactive milling was effective in reducing the size of agglomerates. Conventionally sintered t-ZrO2/Al2O3 and t-ZrO2/Al2O3-NbC composites and SPS-sintered t-ZrO2/Al2O3-NbC showed high densification (> 97% TD), good dispersion of the inclusions in the matrix and good mechanical properties. The t-ZrO2/Al2O3 nanocomposites sintered by FS presented an ultrafast densification (<1 min) with linear shrinkage superior to the sintered samples in conventional furnace, occurring at temperatures lower than 1000°C, with relative densities higher than 90% TD in some compositions. The t-ZrO2/Al2O3-NbC nanocomposites presented competitive properties between conventionally sintered and SPS-sintered composites with higher hardness and fracture toughness than monolithic t-ZrO2. The wear resistance of these conventionally sintered nanocomposites, however, was markedly higher than those of SPS-sintered ones. The oxidation of NbC in the composites sintered conventionally influenced negatively the properties, leading to the suggestion of a \"window\" of temperatures in which the sintering of the t-ZrO2/Al2O3-NbC nanocomposite is interesting without the degradation of the mechanical properties. The results allowed concluding that the studied materials present potential for industrial applications that require high mechanical performance and wear resistance ceramics.

L’intérêt de ces travaux est de proposer un nouveau composite BaAl2Si2O8 (BAS) renforcé par des fibres d’alumine ayant des propriétés physiques similaires tout en étant plus réfractaire que les composites SiO2 / SiO2. La forme cristalline hexagonale du BAS est la forme stable à haute température. Cependant, elle est métastable en dessous de 1590 °C et il est donc nécessaire de la stabiliser pour éviter les transformations cristallines. La stabilisation de la forme hexagonale par substitution atomique, notamment par du rubidium à hauteur de 5 % atomique a été la solution retenue. Concernant le composite à matrice BAS, le choix de fibres d’alumine est motivée par la compatibilité physico-chimique BAS / alumine. Diverses voies d’élaboration de la matrice BAS et du composite BAS / alumine ont été explorées. La voie d’élaboration par « reactive spark plasma sintering » (R-SPS) apporte un gain important en termes de réduction du temps d’élaboration et de rendement. Ce gain de temps évite donc l’exposition du BAS aux hautes températures et le risque de transformation de la phase hexagonale en monoclinique. Cependant la mise en forme par SPS de matériaux oxydes, dont le BAS, est confrontée à l’existence de gradients thermiques importants au sein de l’échantillon. C’est pourquoi, la mise en oeuvre d’un moule chauffant est développée comme une alternative au SPS. Ce système, en cours d’évaluation, devrait permettre l’utilisation de cycles thermiques équivalents à ceux du SPS, tout en limitant fortement les gradients thermiques. / The main purpose of the present work is to propose a new BaAl2Si2O8 (BAS) composite reinforced with alumina fibers exhibiting similar physical properties but a higher refractoriness than SiO2 / SiO2 composites. The hexagonal crystal form of BAS is the stable one at high temperatures. However, it is metastable below 1590 °C and it is therefore necessary to stabilize it in order to prevent crystalline transformations. The stabilization of the hexagonal form by atomic substitution, including rubidium at 5 atomic % has been chosen. Regarding the matrix BAS composite, the alumina fibers selection has been justified by their low physical and chemical reactivity with this material. Several elaboration methods of the BAS matrix and of the BAS / alumina composite have been investigated. The development by "reactive spark plasma sintering" (R-SPS) brings an important benefit in terms of reduced elaboration time and yield. This saving time thus limits the BAS exposure to high temperatures and the risk of transformation into monoclinic. Nevertheless, the SPS shaping of oxide materials, including the BAS, is confronted with the presence of important thermal gradient within the sample. This is why shaping in a heating mold is currently in progress, as an alternative to the SPS. This system should allow the use the same thermal cycles as for SPS, but with lower thermal gradient.

Os compósitos cerâmicos de alto desempenho têm sido objeto de frequentes estudos nas últimas décadas, visando à melhora das propriedades mecânicas e ao aumento da sua gama de aplicações em produtos tecnológicos. Este trabalho consistiu em estudar a preparação, a sinterização convencional e não convencional e as propriedades mecânicas e tribológicas resultantes de dois sistemas compósitos: t-ZrO2/Al2O3 e t-ZrO2/Al2O3-NbC. No sistema t-ZrO2/Al2O3 foram estudadas as composições de 0, 5 e 15% em volume de Al2O3 usando pós comerciais. No sistema t-ZrO2/Al2O3-NbC, foi usado um pó nanocristalino de Al2O3-NbC, obtido por moagem reativa de alta energia e adicionado na proporção de 5% em volume à matriz de t-ZrO2. Os pós foram prensados uniaxial e isostaticamente e sinterizados em forno convencional e pelas técnicas de flash sintering (FS) (t-ZrO2/Al2O3) e spark plasma sintering (SPS) (t-ZrO2/Al2O3-NbC). Os compósitos t-ZrO2/Al2O3 sinterizados convencionalmente e t-ZrO2/Al2O3-NbC sinterizados convencionalmente e por SPS foram caracterizados por medidas de densidade aparente, dilatometria, microscopia eletrônica de varredura (MEV), e medidas de propriedades mecânicas: dureza, módulo de Young e tenacidade à fratura. Os compósitos t-ZrO2/Al2O3 sinterizados por FS foram caracterizados por medidas de densidade aparente, dilatometria in situ e MEV. Os nanocompósitos de t-ZrO2/Al2O3-NbC foram também caracterizados quanto à resistência ao desgaste pelo método esfera-no-disco, utilizando esferas de Al2O3 e WC-6%Co como contramateriais. Os resultados mostraram que a moagem reativa de alta energia foi completa e efetiva na obtenção de pós nanométricos de Al2O3-NbC, com tamanhos de cristalito de 9,1 nm para Al2O3 e 9,7 nm para o NbC. A desaglomeração posterior à moagem de alta energia foi eficaz na redução do tamanho de aglomerados. Os compósitos t-ZrO2/Al2O3 e t-ZrO2/Al2O3-NbC sinterizados convencionalmente e ZrO2/Al2O3-NbC sinterizados por SPS mostraram alta densificação (>97% DT e boas propriedades mecânicas. Os nanocompósitos de t-ZrO2/Al2O3 sinterizados por FS apresentaram uma densificação ultrarrápida (< 1 min) com retração linear superior às amostras sinterizadas em forno convencional, ocorrente a temperaturas inferiores a 1000°C, com densidades relativas superiores a 90% DT em algumas composições. Os nanocompósitos de t-ZrO2/Al2O3-NbC apresentaram propriedades competitivas entre os compósitos sinterizados convencionalmente e por SPS, com dureza e tenacidade à fratura superiores às da t-ZrO2 monolítica. A resistência ao desgaste desses nanocompósitos sinterizados convencionalmente, no entanto, foi notadamente superior à dos sinterizados por SPS. A oxidação do NbC nos compósitos sinterizados convencionalmente influiu negativamente nas propriedades, levando à sugestão de uma \"janela\" de temperaturas em que a sinterização do nanocompósito de t-ZrO2/Al2O3-NbC seja interessante sem a degradação das propriedades mecânicas. Os resultados permitiram concluir que os materiais estudados apresentam potencial para aplicações industriais que requerem cerâmicas de alto desempenho mecânico e de resistência ao desgaste. / High performance ceramic composites have been the subject of frequent studies in recent decades, aiming at improving mechanical properties and increasing their range of applications in technological products. This work consisted in studying the preparation, the conventional and non-conventional sintering and the mechanical properties resulting from two t-ZrO2 matrix composites: the t-ZrO2/Al2O3 system and the t-ZrO2/Al2O3-NbC system. In the t-ZrO2/Al2O3 system, the compositions of 0, 5 and 15% by volume of Al2O3 using commercial powders were studied, while in the t-ZrO2/Al2O3-NbC system, an Al2O3-NbC nanocrystalline powder obtained by high energy reactive milling, deagglomerated, leached in HCl and added in the proportion of 5% by volume to the t-ZrO2 matrix. The obtained powders were uniaxially and isostatically pressed and sintered in conventional furnace and using flash sintering (t-ZrO2/Al2O3) and spark plasma sintering (SPS) (t-ZrO2/Al2O3-NbC). Conventionally sintered t-ZrO2/Al2O3 and conventionally sintered t-ZrO2/Al2O3-NbC composites were characterized by measurements of apparent density, dilatometry, SEM, and mechanical properties: hardness, Young\'s modulus and fracture toughness. The t-ZrO2/Al2O3 composites sintered by FS were characterized by measurements of apparent density, in situ dilatometry and SEM. t-ZrO2/Al2O3-NbC nanocomposites were also characterized for wear strength by the ball-in-disc method, using Al2O3 and WC-6%Co beads as countermaterials. The results showed that the high energy reactive milling was complete and effective in obtaining nanometric powders of Al2O3-NbC, with crystallite sizes equal to 9.1 and 9.7 nm, for Al2O3 and NbC, respectively. The deagglomeration after high energy reactive milling was effective in reducing the size of agglomerates. Conventionally sintered t-ZrO2/Al2O3 and t-ZrO2/Al2O3-NbC composites and SPS-sintered t-ZrO2/Al2O3-NbC showed high densification (> 97% TD), good dispersion of the inclusions in the matrix and good mechanical properties. The t-ZrO2/Al2O3 nanocomposites sintered by FS presented an ultrafast densification (<1 min) with linear shrinkage superior to the sintered samples in conventional furnace, occurring at temperatures lower than 1000°C, with relative densities higher than 90% TD in some compositions. The t-ZrO2/Al2O3-NbC nanocomposites presented competitive properties between conventionally sintered and SPS-sintered composites with higher hardness and fracture toughness than monolithic t-ZrO2. The wear resistance of these conventionally sintered nanocomposites, however, was markedly higher than those of SPS-sintered ones. The oxidation of NbC in the composites sintered conventionally influenced negatively the properties, leading to the suggestion of a \"window\" of temperatures in which the sintering of the t-ZrO2/Al2O3-NbC nanocomposite is interesting without the degradation of the mechanical properties. The results allowed concluding that the studied materials present potential for industrial applications that require high mechanical performance and wear resistance ceramics.

This work was on the effect of electric current on the processing of ceramics. The focus was on electromigration/electrochemistry and plasma effects. While there is no solid evidence that there is plasma in Spark Plasma Sintering, (SPS), newer techniques e.g. flash, use different conditions so there is an interest in understanding the conditions under which a plasma forms. The minimum arcing voltage was found from literature to be from 10-15V for materials of interest. This is above that found in SPS (10V). However, due to the many contact points in a powder compact much higher voltages (50V) were required in practical experiments. Optical spectroscopy was used to verify the formation of a plasma, and emission peaks from the powder compact material were visible implying they were vaporised and formed the plasma. Electromigration was exploited to alter the oxidation of zirconium diboride, by passing current through the oxide layer (120μm zirconia base grown at 1200°C) oxygen could be pumped either away or toward the diboride bulk. Small cubes (3mm) of diboride had platinum foil electrodes applied on both sides and oxidation was performed at 1400°C for 5hr. Without a field the oxide grew to 360μm, by applying 10V and 100mA the oxide grew to 150μm under the +ve electrode but 1400μm under the -ve electrode. Electrochemical reduction was believed to have occurred due to the electrical properties of the material changing during oxidation and visible blackening of the oxide. Combining the techniques from both earlier works, a contactless flash sintering setup was developed. This used two plasma arcs as electrodes to heat and pass current through the sample. Various materials, currents and times were used, but the best result was with SiC:B4C which was sintered in 3s with 6A, the microstructure showed sharp grains, no segregation and limited grain growth ( initially 0.7μm SiC and 0.5μm B4C, this grew to 1.1μm and 1.4μm). This was the first recorded case of contactless flash sintering and the technique has the potential to sinter ceramics in a continuous manner.

Four silicon nitride powder blends vary in starting powder characteristics, glass chemistry, and phase composition. This work focuses on how these properties influence densification behavior, microstructural development, and the resulting mechanical performance of dense ceramics. Previous work completed on alpha-rich, low oxide containing (8 wt%), and fine silicon nitride powder (GS-44) showed high hardness equiaxed with grained ceramic. GS-44 served as an excellent precursor for the matrix phase material in graphene reinforced composites, which resulted in 235% increase in toughness and high hardness retention [1] with the addition of 1.5 vol% graphene. As the GS-44 powder is no longer in production, investigative work into other commercial powders and customization of powder blends was initiated. Commercial blends were selected based on availability, high alpha content, fine particle size, and additive chemistry (Al2O3, MgO, and Y2O3). The objective was to understand which powder characteristics led to a ceramic design that contained high hardness, strength, and toughness properties in order to increase the use of silicon nitride in extreme temperature environments. One such example is aerospace and structural applications that require a high-performance material that is lightweight and good thermal stability. Strong covalent bonding in silicon nitride make densification of powders extremely difficult; thereby, sintering additives are necessary to promote liquid phase sintering processes. Compaction of ceramic powders was carried out using a spark plasma sintering (SPS) furnace by utilizing a pulsed direct current through a conductive graphite die that encapsulates the sample powder. SPS was preferred over other conventional sintering methods owing to its high heating rate and short dwell times at the sintering target temperature. Thus, SPS provides superior control for tailoring the final silicon nitride properties by producing a hard alpha-phase and tough beta-phase microstructures. The custom blend developed had an appreciable amount of media wear included during the milling process that increased the additive content. Development of the custom blend was used to understand the effect of a larger additive content. Commercial GS-44 blend was used as the control to track the effect of adjusting specific surface area and oxide content in silicon nitride powder systems (HCS-M, C-R3, and UA-SN). The mechanical results for the four matrix systems, showed that toughness increased with grain coarsening and minimization of alumina content in beta silicon nitride. Based on these findings it is important to determine tradeoffs (i.e. balance of high hardness, toughness, and strength) to engineer an optimal ceramic that can be used for structural and aerospace applications.

Diploma thesis occupy with preparation of porous material from magnesium powder with a HAp admixture by cold pressing followed by spark plasma sintering (SPS). This thesis contain both preparation of bulk material, diffusion plot and charakterization of materials based on the compaction process conditions. On the basis of physical mechanical characteristics, the impact of the pressing process on the subsequent sintering and the resulting material properties are evaluated. Bulk material is characterized considering to structure and physical–mechanical properties. Properties of final metarial will serve to optimize conditions for process of bulk material preparation.

This diploma thesis deals with research and preparation of bulk materials based on the Mg–Al–Ti system. The theoretical part summarizes the basic knowledge about magnesium alloys, focusing mainly on Mg–Al and Mg–Ti systems. Furthermore, basic information on powder metallurgy methods was included here, from the production of powder materials, through their compaction, to heat treatment and spark plasma sintering (SPS). The theoretical part ends with literature review on the current research of the Mg–Al–Ti system. In the experimental part, bulk materials based on the Mg–Al–Ti system was prepared using traditional methods of powder metallurgy, as well as using the SPS method. The microstructure of the material, elemental and phase composition was examined in this thesis. Subsequently, Vickers hardness and flexural strength were measured, and fractographic observation of the fracture surface was performed. It was found that the aluminum was completely dissolved during the heat treatment, but the titanium particles remained almost intact in the material and worked as a particulate reinforcement. Materials prepared by methods of conventional powder metallurgy showed increased porosity compared to materials prepared by the SPS, resulting in lower hardness and flexural strength. The hardness increased with increasing the amount of aluminum and titanium and with the amount of magnesium phase . Fractographic observation of the fracture surface suggests that a diffuse connection between the reinforcement and the matrix may have occurred after the sintering process.

Les propriétés idéales d’un matériau de blindage sont la combinaison d’une extrême dureté pour casserles noyaux des projectiles et d’une grande ductilité pour résister à l’impact et arrêter les fragments du projectile. Or cettecombinaison de propriétés est incompatible avec un matériau unique. Pour pallier ce problème, les concepteurs de blindageassocient un matériau dur (céramique) à un matériau ductile (métal). Une autre solution serait de réaliser un matériauprésentant un gradient de propriétés mécaniques : dans le cas présent, d’une très grande dureté de la face avant à une grandeductilité de la face arrière. Les technologies non conventionnelles de frittage telles que le Spark Plasma Sintering (SPS)permettent d’assembler ou de fritter/assembler des matériaux aux caractéristiques aussi différentes et complémentaires. Ils’agit donc d’étudier les conditions d’assemblage ou de cofrittage de tels matériaux (dans le cas présent, Al2O3 et Ti) ainsique l’influence de la microstructure résultante de l’ensemble sur sa performance balistique.La première partie de ce travail a porté sur la caractérisation de l’alumine et du titane. Cinq poudres d’alumines ontété étudiées d’un point de vue comportement au frittage. Trois d’entre elles sont retenues en raison de leurs microstructuresintéressantes, proches en termes de densité et de taille de grains. Ces alumines ont été caractérisées mécaniquement (dureté,ténacité, résistance à la rupture) et balistiquement pour n’en garder qu’une dans la deuxième partie du travail. Le titane, frittédans les mêmes conditions que l’alumine, a montré qu’il n’avait malheureusement pas les propriétés attendues (absence deductilité).La seconde partie du travail a montré que l’obtention de MGFs sains à partir de Al2O3 et Ti uniquement est délicate,que ce soit avec un intercalaire sous forme de monocouche ou de multicouche. La forte affinité du titane avec l’oxygène(formation d’oxyde ou en insertion) et le carbone (formant des carbures), ainsi que sa réactivité avec l’alumine (produisantdes intermétalliques) rend le MGF fragile et incapable d’accommoder les contraintes résiduelles d’élaboration. L’insertiond’une faible proportion de nickel (plus ductile et moins réactif vis-à-vis de l’oxygène que le titane) dans les composites apermis d’obtenir des MGFs sains, dont le comportement balistique a pu être évalué. / The objective is to improve ballistic performance of armors. A perfect armor combines ductility to resistto the impact and high hardness to stop projectile’s fragments. However, such an association of properties is inconsistent witha single material. The solution is to perform a functionally graded material (FGM) with a ductile metal at the back side of thesample and a hard ceramic on the top side. Non-conventional technologies like Spark Plasma Sintering allow joining orsintering all types of materials with different and additional properties. Furthermore, with this technique, high heating ratescan be achieved, limiting grain growth and resulting in a fine microstructure. The goal is to study joining conditions or cosinteringof such materials (in this case, Al2O3 and Ti), as well as the resulting microstructure on the ballistic efficiency.The first part of the study focused on the characterization of alumina and titanium. Five powders of alumina werestudied from a sintering point of view. Three of which were selected because of their interesting microstructures, close indensities and grain sizes. These ceramics have been characterized mechanically (hardness, toughness and strength) andballistically. One of them is adopted to realize FGM. Titanium, sintered with the same conditions, unfortunately, doesn’t haveexpected properties (absence of ductility).The second part of the work showed that the preparation of FGM without cracks from Al2O3 and Ti only ischallenging, with an interlayer with one or more layers. The strong affinity of Ti with oxygen (formation of oxides orinsertion) with C (forming carbides) and its reactivity with alumina (forming intermetallics) make the FGM brittle and enablethe release of residual stresses during the process. By adding a low amount of nickel (more ductile and less reactive withoxygen and titanium) in composites, FGMs almost without cracks were obtained. The latter were evaluated ballistically.

L'utilisation de la thermoélectricité passe par une amélioration du rendement du module thermoélectrique à travers l'optimisation de ses dimensions et l'augmentation du facteur de mérite des matériaux thermoélectriques, mais aussi par une réduction des coûts de synthèse et de mise en forme. Dans le cadre de cette thèse nous nous sommes intéressés à la synthèse de β–Zn4Sb3 nanométrique par une méthode de chimie douce à faible dépense énergétique. Nous avons étudié la mise en forme de ce matériau par des technologies d'impression qui permettent d'atteindre les dimensions optimales et présentent un coût réduit. β-Zn4Sb3 est obtenu en deux étapes : une synthèse à reflux suivie d'un traitement thermique à 400°C sous vide secondaire. La composition chimique (DRX, affinement Rietveld), la morphologie (MEB, TEM) et la stabilité en température (spectroscopie Raman) de la poudre sont étudiées. β-Zn4Sb3 ainsi obtenu est densifié par SPS et ses propriétés thermoélectriques sont mesurées montrant une augmentation du facteur de mérite pour des températures inférieures à 100°C. Au dessus de cette température, la présence de porosité et de zinc augmente la résistivité électrique et la conductivité thermique et les échantillons ont un facteur de mérite de 0,6 à 400°C. Enfin, la poudre est mise en forme par sérigraphie et atomisation sur substrat en verre et en Kapton. Le β-Zn4Sb3 montre une forte résistivité électrique juste après impression mais l'application de traitement mécanique et thermique permet de la diminuer. Le facteur de mérite estimé des dépôts est de 0,06 à 400°C. Cependant le faible coût de mise en forme et la possibilité d'automatisation rendent ces techniques viables. / Use of thermoelectricy involves an increase of the module efficiency. In this purpose we need to optimize the dimension of the module and to increase the figure of merit of thermoelectric materials. But we also need to reduce the synthesis and shaping cost. Within the framework of this thesis, we focused on the synthesis of β-Zn4Sb3 nanoparticles by a low energy technique: wet chemistry. We also studied the shaping of this material by printing technologies. These cost-effective technologies allow reaching optimized dimensions. β-Zn4Sb3 is synthesized in two steps: a reflux synthesis flowed by a thermal treatment at 400 °C under vacuum. Chemical composition (XRD, Rietveld refinement), morphology (SEM, TEM) and thermal stability of the powder are studied. The as product β-Zn4Sb3 is densified by SPS and we measured its properties. They show an increase of the figure of merit for temperatures below 100 °C. However above this temperature the presence of zinc and porosity increase electric resistivity and thermal conductivity, leading to a figure of merit of 0.6 at 400 °C. Finally the powder is shaped by two printing technologies: screenprinting and atomization on glass and Kapton substrate. Just after printing the samples show a high electrical resistivity but a decrease is observed after mechanical and thermal treatment. The estimate figure of merit of printing β-Zn4Sb3 is 0.06 at 400 °C. However the printing techniques are cost-effective and allow mass production, which make them still interesting.