This project considers the co-rotating twin screw extrusion of a confectionery paste comprising powdered proteins, sugars, water and fats. As is the case with many food industry products, this process has been developed experimentally with little quantitative understanding of how variations in processing conditions influence the formation of the extrudate. A variety of techniques have therefore been developed to characterise and quantify the dispersive mixing, distributive mixing and rheological flow properties of this complex, multiphase, viscoelastic, unstable material. These techniques have then been utilised in a pilot plant extruder study of the mechanics of mixing and paste formation during extrusion, considering the influence of both processing conditions and screw profile. The internal evolution of paste microstructure has been successfully tracked along the length of screw profile using dead-stop extractions of the screws. A rigorous off-line assessment of shear yield strength behaviour using cone penetrometry has shown the use of conventional off-line rheometers to be unviable due to rapid post extrusion hardening. This highlighted the need for an in-line rheological measurement technique for continuous extrusion analysis where the extruded material is severely time dependent and not extractable. In pursuit of this, a novel arrangement of bender elements is proposed and trialled, to rapidly characterise material parameters of viscoelastic pastes. A second technique looking to extend the application of shear wave interface reflection to multiphase pastes is also trialled. A novel analysis of thermogravimetric data (TGA) has generated a viable index of distributive mixing, suitable for use on complex multi-component materials where thermal decomposition temperatures of the components are not well defined. Quantitative image analysis of pastes using scanning electron microscopy (SEM), optical microscopy protein staining and a novel application of multiphoton microscopy (MPM) have been used to visualise paste microstructure and quantify dispersive mixing. From the pilot plant extruder study, the application of these techniques was successful in mapping the evolution of paste mixing and the resulting microstructure, as well as identifying key differences between pastes mixed by twin screw extrusion and batch mixing.

Environmentally-assisted cracking (EAC) phenomena affect the in-service behaviour of austenitic stainless steels in nuclear power plants. EAC includes such degradation phenomena as Stress Corrosion Cracking (SCC) and Corrosion Fatigue (CF). Factors affecting EAC include the material type, microstructure, environment, and stress. This is an important degradation issue for both current and Gen III+ light water reactors, particularly as nuclear power plant lifetimes are extended ( > 60 years). Thus, it is important to understand the behaviour of the alloys used in light water reactors, and phenomena such as SCC to avoid failures. Although there is no agreement on the mechanism(s) of SCC, the importance of localized electrochemical reactions at the material surface is widely recognised. Considerable research has been performed on SCC and CF crack growth, but the initiation phenomena are not fully understood. In this project, novel in situ analytical TEM techniques have been developed and applied to explore localised reactions in Type 304 austenitic stainless steel. In situ transmission electron microscopy has become an increasingly important and dynamic research area in materials science with the advent of unique microscope platforms and a range of specialized in situ specimen holders. In metals research, the ability to image and perform X-ray energy dispersive spectroscopy (XED) analyses of metals in liquids are particularly important for detailed study of the metal-environment interactions with specific microstructural features. To further facilitate such studies a special hybrid specimen preparation technique involving electropolishing and FIB extraction has been developed in this thesis to enable metal specimens to be examined in the liquid cell TEM specimen holder using both distilled H2O and H2SO4 solutions. Furthermore, a novel electrode configuration has been designed to permit the localized electrochemical measurement of electron-transparent specimens in the TEM. These novel approaches have been benchmarked by extensive ex situ experiments, including both conventional electrochemical measurements and microcell measurements. The results are discussed in terms of validation of in situ test data as well as the role of the electron beam in the experiments. In situ liquid cell TEM experiments have also explored the localized dissolution of MnS inclusions in H2O, and correlated the behaviour with ex situ experiments. Based on the research performed in this thesis, in situ liquid cell and in situ electrochemical cell experiments can be used to study nanoscale reactions pertaining to corrosion and localized dissolution leading to "precursor" events for subsequent EAC phenomena.

Die Arbeit beschäftigt sich mit der Erweiterung der für dicke Proben schon mit Erfolg eingesetzten Werkstoffanalytischen Methode Elektronenstrahl-Mikroanalyse (ESMA) mittels Peak/Untergrund-Verhältnissen auf die Analyse von dünnen Schichten (unter 1 μm) zur qualitative und quantitativen Elementanalyse sowie zur Ermittlung von Schichtdicken. Weiterhin wird auf der Basis von einer ESMA-Methode für zwei dünne Schichten auf einem Substrat wird ein Modell zur Ermittlung des Phasenwachstumskoeffizienten für eine intermetallische Phase die sich bei der Diffusion zwischen einer dünnen Schicht und einem Substrat bildet, mittels ESMA-Messungen bei gleichzeitiger Erwärmung der Probe dargestellt. / The paper deals with the application of the materials analysis method EPMA by peak-to-background ratios, which is currently being used for the analysis of thick samples successfully, to thin layers (less than 1 μm) for the quantitative element analysis as well as for thickness prediction. In addition a model has been established on the Basis of an EPMA method for two films on a substrate for deriving the phase growth coefficient of an inter-metallic phase which grows during the diffusion between a thin layer and a substrate from EPMA measurements while simultaneously heating the sample.

No description available.

L'utilisation de lasers est largement répandue dans le domaine de la microanalyse directe des solides. La matière vaporisée, en focalisant un faisceau laser de forte puissance sur la cible, peut être analysée soit par spectrométrie d'émission optique sur plasma induit (LIBS, acronyme anglais pour Laser Induced Breakdown Spectroscopy), soit par une source à plasma induit par haute fréquence couplée à la spectrométrie d'émission optique (ICP-AES) ou à la spectrométrie de masse (ICP-MS). Avec une résolution spatiale à l'échelle microscopique, les techniques d'ablation laser permettent ainsi d'accéder à la composition élémentaire locale de la surface d'un matériau. Néanmoins, les performances analytiques de ces techniques pourraient être améliorées par l'utilisation combinée des informations LIBS et ICP afin également de comprendre et maîtriser davantage l'interaction laser/matière. Dans ce but, ce travail a consisté à développer une technique de microanalyse par ablation laser couplée avec une détection en simultané par ICP et par LIBS afin d'étudier les potentialités analytiques de cet instrument pour cartographier la surface des matériaux. Les performances et les limitations de ce système ont été évaluées d'une part, en caractérisant les aérosols produits par ablation laser et d'autre part, en étudiant les signaux LIBS et ICP obtenus à partir d'un même prélèvement de matière. Le phénomène de fractionnement élémentaire rencontré sur des matrices critiques telles que le laiton a été mis en évidence en microablation malgré des caractéristiques de l'interaction laser/matière différente de la macroablation. Une méthode de correction, a posteriori, par l'efficacité d'extraction de la cellule d'ablation a été proposée afin de pallier ces effets limitatifs pour l'analyse quantitative. Une cellule d'ablation, optimisée à partir d'une étude de simulation numérique, a été développée afin de s'adapter aux applications de cartographies de surface. Les performances analytiques du système ont été évaluées en termes de stabilité (8-10%), de résolution spatiale (5 µm) et de limites de détection (de l'ordre de la ppm dans le solide avec un détecteur de masse). La complémentarité des mesures LIBS et ICP représente à la fois un outil de diagnostic de l'interaction laser/matière et un instrument d’analyse très complet grâce à la double détection qui permet de suivre simultanément des traces et des majeurs sur une large gamme d'éléments de la classification périodique / Laser ablation is widely spread for solid sample microanalysis. A tightly focused laser beam allows direct sampling of matter, the ablated mass can then be analysed either with LIBS (Laser Induced Breakdown Spectroscopy) or with an inductively coupled plasma source combined with an optical emission spectrometer (ICP-AES) or a mass spectrometer (ICP-MS). With spatial resolution down to the micron scale, laser ablation techniques permit local elemental analysis of sample surface. Nevertheless, analytical performances of such techniques could be improved by combining LIBS and ICP information to understand and control laser/matter interaction. For this purpose, this work aimed to develop a microanalytical technique based on laser ablation coupled to simultaneous detection with LIBS and ICP to study analytical potentialities of such technique for elemental mapping of material surface. Performances and limitations of the system were studied on one hand, by characterizing laser-induced aerosols and on the other hand, by studying simultaneous LIBS and ICP signals. Elemental fractionation on critical matrices such as brass was evidenced in microablation despite a different laser/matter interaction compared with macroablation. A correction procedure a posteriori using the total extraction efficiency of the ablation cell was proposed to overcome this problem for quantitative analysis. An ablation cell, optimized from a numerical simulation study, was developed for mapping applications. Analytical performances were evaluated in terms of stability (8-10 %), spatial resolution (5 µm) and detection limits (in the ppm range with ICP-MS). The LIBS and ICP complementarity makes the double detection system a diagnostic tool for laser/matter interaction and an analytical instrument allowing simultaneous monitoring of traces and majors from a large element range of the periodic classification

Les latérites sont les sols les plus utilisés dans les travaux de génie civil, plus particulièrement en construction routière dans la plupart des pays de la zone intertropicale. Ce sont des sols résiduels ou détritiques provenant de l’altération des roches préexistantes. Ces sols contiennent en quantité appréciable des oxydes de fer et d’aluminium, de la kaolinite et de la silice, mais de faibles quantités d’oxydes de titane, de manganèse, de magnésium, …, etc. La grande diversité des composés chimiques des latérites rend leur caractérisation malaisée. En outre, les documents normatifs et les guides techniques utilisés pour le dimensionnement des chaussées en Afrique subsaharienne pour la plupart inadaptés, ne prennent pas en compte la spécificité des conditions climatiques et environnementales des formations latéritiques dans les projets routiers. Une caractérisation interdisciplinaire de ces sols avec la prise en compte des facteurs intervenant dans le processus de latéritisation permettrait de déterminer des propriétés plus précises, plus pertinentes et beaucoup plus représentatives. Ce travail a pour vocation la caractérisation et la détermination de l’aptitude des sols latéritiques du sud-ouest du Niger. La zone concernée par l’étude comporte sept gisements latéritiques aux contextes géologiques forts différents les uns des autres. Notre étude, basée sur diverses approches a permis de déterminer les propriétés géotechniques et mécaniques des sols d’une part et les propriétés chimiques et minéralogiques d’autre part. À l’issue de l’étude, deux catégories de sols sont à distinguer : [1] les sols de bonne portance : d’indice CBR de l’ordre de 100 contiennent en moyenne une teneur en fines n’excédant pas 12% et un indice de plasticité inférieur à 15. Pour ces sols, la portance dépend beaucoup de la taille des particules. Ces derniers ont une résistance élevée au cisaillement et un angle de frottement interne effectif φ’ de l’ordre de 40° ainsi qu’une cohésion effective c’ supérieure à 10 kPa. Leur comportement est dilatant au cours du cisaillement. Ils présentent de faibles valeurs en indice de vide et en perméabilité. De même, leur amplitude de tassement est faible. La bonne portance de ces sols se justifie principalement par leur teneur appréciable en oxydes de fer. L’attaque de la matrice fine par ces derniers se fait de manière diffuse ou par concrétionnement sous forme de cercles d’oolithes et de pisolithes ovoïdes tangents. [2] les sols de faible portance : la fraction fine et l’indice de plasticité sont élevés, respectivement de l’ordre de 25 et 30. La portance est de l’ordre de 30, l’angle de frottement interne inférieur à 30° et la cohésion inférieure à 5 kPa. Ces sols résistent faiblement au cisaillement et leur comportement est contractant, c’est-à-dire celui d’un sable lâche. Ils sont plus compressibles, encore moins perméables avec un coefficient de gonflement élevé. La faible portance de ces sols est imputable à leur faible teneur en oxydes de fer, ainsi que le mode d’attaque qui se fait de manière isolée.L’amélioration des sols présentant une faible portance a été expérimentée en y rajoutant séparément une certaine teneur en liant hydraulique (ciment), en chaux (CaO) et en nodules latéritiques. Les analyses minéralogiques et chimiques ont montré que l’ajout des produits a conduit à une modification texturale et a favorisé la mise en place de composés chimiques néo-synthétisés ayant pour rôle principal de renforcer les liaisons entre les éléments minéraux contenus dans les échantillons de sol latéritique. Dans la plupart des cas, les échantillons améliorés ont présenté une bonne portance validant ainsi leur aptitude en construction routière. / Laterites are the most commonly used soils in civil engineering works, particularly in road construction in most countries of intertropical region. These are residual or detrital soils resulting from the alteration of pre-existing rocks. These soils contain a considerable quantity of iron and aluminum oxides, kaolinite and silica, but small quantities of titanium oxides, manganese, magnesium, etc. The large diversity of the chemical compounds of laterites makes their characterization difficult. Moreover, specification documents and technical guides used for road design in sub-saharan Africa, most of them unsuitable, do not take into account the specificity of climatic and environmental conditions of laterite formations in road projects. An interdisciplinary characterization of these soils, taking into account the factors involved in the lateritization process, should make it possible to be determined more precisely. It’s also the best way to get more relevant and much more representative properties. The aim of this work is to characterize and determine the lateritic soils suitability of southwestern Niger in road construction. The area covered by the study consists of seven lateritic deposits with strong geological different contexts from one to another. Our study, based on various approaches, made it possible to determine the geotechnical and mechanical properties of the soils on the one hand and the chemical and mineralogical properties on the other hand. At the end of the study, two categories of soils are to be distinguished: [1] soils with good bearing capacity : CBR of around 100 contain average fines content not exceeding 12% and a plasticity index less than 15. For these soils, the bearing capcity depends very much on the size of the particles. They have a high shear strength, an effective internal friction angle φ' of the order of 40° and an effective cohesion c' greater than 10 kPa. Their behavior is dilatant during shear. They have low values in void ratio and in index permeability. Similarly, their amplitude of settlement is low. The good bearing capacity of these soils is mainly justified by their appreciable iron oxides content. The attack of the microstructure by the latter is done in diffuse way or by concretionary circles of oolites. [2] the soils of low bearing capacity : the fine fraction and the plasticity index are high respectively of the order of 25 and 30. The bearing capacity is around 30, the internal friction angle is less than 30° and the cohesion less than 5 kPa. These soils are weak to the shear and their behavior is contracting (loose sand behavior). They are more compressible and less permeable with a high swelling coefficient. The low bearing capacity of these soils is attributable to their low iron oxide content and to the mode of attack which is carried out in isolated way.The improvement of soils with low bearing capacity has been tested separately by adding a certain amount of hydraulic binder (cement), lime (CaO) and lateritic nodules. Mineralogical and chemical analyzes showed that the addition of the products led to a textural modification and favored the production of neo-synthesized chemical compounds whose main role was to strengthen the links between the mineral elements contained in the lateritic samples. In most cases, the improved samples showed good bearing capacity and validated their road pavement suitability.

Reduced activation oxide dispersion strengthened (ODS) steels are candidate alloys for use in fusion reactor systems and are fabricated by mechanically alloying yttrium oxide to a reduced activation ferritic steel powder. The product is consolidated at high temperature by hot isostatic pressing (HIP), producing a dispersion of nanometre sized oxide particles throughout the ferritic microstructure. These particles have been shown to both improve the high temperature mechanical properties of the alloy and provide trapping sites for helium gas. The use of these particles to sequester helium is of particular significance in the development of a structural ODS steel for fusion reactor systems. A fusion power reactor, based on the ITER design, is expected to produce over 2000 appm transmutant helium in any steel components exposed to the core neutron flux. At these gas concentrations, conventional steels undergo severe swelling and embrittlement, motivating the development of materials capable of managing helium accumulation. This thesis investigates the use of the oxide particle dispersion in sequestering helium introduced by ion implantation. An initial characterisation of a model Fe-14Cr-0.25Y₂O₃ (wt%) system was completed using high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). This demonstrated the efficacy of the production methods and the gas trapping capabilities of the oxide particles via argon gas, introduced during the mechanical alloying process. The subsequent consolidation of a full set of Fe-14Cr-3W-0.2Ti-0.25Y₂O₃ (wt%) ODS alloys at 1150°C, 1050 °C and 950 °C produced a systematic variation in the density of the particle dispersion. The characterisation of these materials using APT provided an insight into the consistent Y₂Ti₃O₅ particle chemistry found in each consolidation, and identified a stoichiometric shift from Y₂Ti₃O₅ to YTiO2 following short term annealing periods at 1000°C. Though further work is required, this shift is thought to be consistent with a thermodynamically mediated transition of the metastable clusters to stable oxide particles. Following implantation with 2000 appm helium and examination under TEM, the helium bubble and particle densities were found to be closely correlated thus providing evidence for an association between the particles and the gas bubbles. Controlling the helium bubble density via the particle dispersion demonstrates the potential use of processing temperature in controlling how helium accumulates in an implanted ODS microstructure. The effects of both bubble and particle densities on mechanical properties were investigated further using nanoindentation methods. Significant local variation in the hardness of the ODS steels was found to result from the bimodal grain size distribution of the material. By using only those measurements taken from large grained regions of the ODS, the grain refinement and particle hardening effects could be deconvolved and used to quantify particle hardening using a dispersed barrier model. The significant hardening effects with helium addition observed in the reference alloys were found to be almost entirely absent from the ODS systems, though anomalous softening in the 950°C consolidation indicated a potentially unexpected interaction between the bubble and particle populations. A possible explanation for this anomaly and a proposal for further work to establish its origin is discussed.

Afin d’accroitre le rendement des turbomachines les motoristes aéronautiques visent à développer de nouveaux matériaux réfractaires permettant d’augmenter les températures de service des parties les plus chaudes. Les travaux présentés dans ce mémoire s’inscrivent dans ce contexte et ont pour cadre le projet européen FP7-HYSOP dans lequel les alliages Nbss-Nb5Si3 sont à l’étude. Alors que d’un point de vue mécanique leurs propriétés sont compatibles avec leur industrialisation, leur résistance à l’oxydation dès les températures intermédiaires (800°C) constitue l’obstacle majeur à leur application. Deux voies sont suivies dans ce travail pour améliorer ce comportement. La première vise à évaluer l’effet d’un affinement de microstructure en synthétisant l’alliage Nbss-Nb5Si3 soit par la voie fusion, soit par métallurgie des poudres. Il a été montré que les microstructures les plus fines permettent de diminuer les cinétiques d’oxydations à 1100°C, et de s’affranchir des phénomènes d’oxydation catastrophique dont souffrent les alliages à microstructure grossière à 815°C. Des modèles diffusionnels gouvernant l’oxydation de ces matériaux ont pu être proposés. La seconde partie se focalise sur le développement de revêtements à base de siliciures, par la technique de cémentation activée en caisse, dont le caractère protecteur est assuré principalement par la formation d’une couche de silice (SiO2). Une série de tests d’oxydation/corrosion, représentative des conditions extrêmes régnant en sortie de chambre de combustion (isotherme ou cyclique, sous air, air + H2O, mélange silicaté CMAS), a permis d’évaluer et de hiérarchiser les performances des différents systèmes revêtus / Progress in the field of gas-Turbine engines for aircrafts is controlled by the availability of new structural materials able to withstand higher temperatures than nickel based superalloys. The present PhD work was conducted in this context, within the framework of the European FP7-HYSOP project, in which Nbss-Nb5Si3 alloys are studied. From a mechanical point of view, the physicochemical properties (room temperature fracture toughness and creep rate) are compatible with the targeted temperature (1300°C). However, starting from the intermediate temperatures (800°C), the oxidation resistance of those alloys is the major obstacle to their use. In this work, two ways are investigated to improve this behavior: The first one aims at studying the effect of a refinement of microstructure synthesizing the Nbss-Nb5Si3 alloy both by fusion method and powder metallurgy route. It was shown that refining the microstructure led to decrease the oxidation kinetics at 1100°C and suppressed the catastrophic breakaway oxidation (pesting) typical of the Nb-Si alloys with coarse microstructure at 815°C. Furthermore, diffusion models were proposed to describe oxidation kinetics both at 815°C and 1100°C. The second part of this study is devoted to the development of silica forming protective coatings. Diffusion silicide coatings were manufactured by the halide activated pack-Cementation method. The various conditions of oxidation/corrosion tests (isothermal or cyclic, in air, air containing water vapor, CMAS silicate melt) allowed assessing and ranking the performance of coated systems

The thesis comprehensively investigates 2 pcs of ferrous and 14 pcs of bronze Celtic artefacts from a region of Zdejciny by Beroun. The study by means of ore microscopy, x-ray fluorescent microspectrometry, chemical microanalysis, Raman microspectrometry and x-ray powder diffractive analysis has showed that the bronze artefacts are made mainly of bronze. The phases present in the studied items correspond to fields and + of the Cu-Sn phase diagram. Content of Sn in bronze ranges between 4 and 33 wt.%. For the bronze selected items there was also Vickers microhardness measured. There were two artefacts where areas with a significant lead enrichment were found. Corrosive products were also deeply analysed and identified.

Nombreuses prévues et études sur la transmission inter et trans-générationnelle du traumatisme nous confirment l'évidence de la transmission sans pour autant en donner une description détaillé du processus qui pourrait être à la base de la transmission directe de la mère au bébé. La compréhension de ce processus pourrait permettre de penser et promouvoir des dispositifs de soin précoce pour les mères traumatisées et leurs bébés. Cela s'avère d'autant plus important dans les contextes de trauma collectif, comme les situations d'urgence humanitaire, où une large partie de la population est exposée à des événements traumatiques extrêmes et répétés. Dans le but d’identifier les déterminantes propres à la transmissions directe du traumatise psychique de la mère au bébé en contexte humanitaire, nous avons recrutées vingt-quatre dyades mère-bébé, en trois pays affectés par la crise politico-religieuse centrafricaine démarrée en 2013 (République Centrafricaine, Tchad et Cameroun). Dans les vingt-quatre dyades, les mères ont été exposées à un ou plusieurs événements traumatiques, en l'absence du bébé, avant sa naissance ou pendant la grossesse ; l'âge de bébé est compris entre un mois et trois ans. Ces Mères et bébés ont étés rencontré lors d'un entretien semi structuré que nous avons filmé. Cela pour permettre une microanalyse des interactions trans-modales (visuelles, corporelles, vocales) entre mère et bébé, dans l'idée de comprendre si pendant la révocation de l'événement traumatique de la part de la mère, les interactions subissaient des modifications et dans ce cas, lesquels. Les interactions dyadiques ont été aussi observées dans une situation de jeu libre sans la présence d'interviewer. Les représentations maternelles ainsi que les marqueurs traumatiques dans le discours ont été pris en compte comme facteurs contributeurs de la transmission traumatique. Les résultats de l'analyse des échanges dyadiques pendant l'entretien, montrent une évidence dans le changement d'interactions dans le moment de révocation traumatique de la mère. Les détails de cette différence d'interaction entre mère et bébé sont présentés dans la session de résultats. Dans la discussion ils sont ensuite mis en relation avec le discours de la mère où nous pouvons remarquer le rôle de représentations maternelle à propos du bébé qui ont une implication importante dans la transmission traumatique. L'analyse de toutes ces composantes multiples semble nous indiquer que le traumatisme maternelle influence les représentations de la mère à propos du bébé, de sa relation avec lui et du mandat transgénérationnelle dont le bébé va être investi. De plus les mères traumatisées, envahies par leur propre état émotionnel négatif ont des difficultés à interpréter correctement les expressions verbales et non verbales du bébé et à trouver des réponses appropriées. Cette difficulté se traduit dans la transmission de son état émotionnel négatif au bébé, qui interprète l'absence de réponse de la mère ou les réponses pas adéquates à ses sollicitations, comme des signaux négatifs vis-à-vis de son propre état émotionnel. Lé bébé et il n'a pas d' autres stratégies que celle d'internaliser l'état affectif négatif maternel et de le transformer dans son propre état interne. Malgré l'évidence de la transmission de l état émotionnel négatif de la mère au bébé, nous avons pu observer certains facteurs de protection qui peuvent préserver les mères et les bébés de l'inévitabilité de cette transmission. Les mères et les bébés montrent plusieurs ressources et compétences internes qui nous laissent penser qu'une réparation est possible ainsi qu'une prévention de la transmission traumatique quand le processus est déjà démarré. Pour conclure ce travail nous présentons de propositions cliniques de prise en charge des mère ayant vécu un traumatisme et leur bébé, dans le but de réduire les effets de la possible transmission du traumatisme au bébé ou, quand possible, de la prévenir. / Several studies on the inter- and trans-gerational transmission of trauma confirm the evidence of transmission without giving a detailed description of the process that could be the basis of mother to child direct transmission. Understanding this process could help to think and promote early care for traumatized mothers and their children. This is especially important in contexts of collective trauma, such as humanitarian emergencies, where a large part of the population is exposed to extreme and repeated traumatic events. In order to identify the determinants of the mother to child direct transmission in a humanitarian context, we recruited twenty-four mother-child dyads, in three countries affected by the Central African political and religious crisis started in 2013 (Central African Republic, Chad and Cameroon). The twenty-four dyads were composed by mothers exposed to one or more traumatic events, in the absence of the child, before childbirth or during pregnancy and their children, aged from one month to three years. We met the mother-child dyads during a semi-structured interview that we filmed in order to allow a microanalysis of the cross-modal (visual, bodily, vocal) interactions between mother and child. The objective was to understand whether interactions underwent modifications during the revocation of the traumatic event by the mother, and if yes, to have a better comprehension of these changes. Dyadic interactions were also observed in a free play situation without the presence of interviewers. Maternal representations as well as traumatic markers in mother discourse have been taken into account as factors contributing to the traumatic transmission. The results of the dyadic exchanges analysis during the interview show some evidences in the modification of interactions during the traumatic revocation of the mother. The details of this difference in mother-child interactions are presented in the results session. In the discussion session, the results from the microanalysis of interactions, have been connected to the mother's speech where we can notice the role of maternal representations about the child that have an important involvement in traumatic transmission. The analysis of all these multiple components seems to indicate that maternal trauma influences the mother's representations about the child, her relationship with him and the intergenerational mandate of which the child will be assigned to. In addition, traumatized mothers who are overwhelmed by their own negative emotional state, have difficulties in interpreting the child's verbal and non-verbal expressions correctly and finding appropriate answers. This difficulty is reflected in the transmission of mother negative emotional state to the child, who interprets the mother's lack of response or inadequate responses to his solicitations, as negative signals about his own emotional state. The child has no other strategies than internalizing the maternal negative affective state and transforming it into its own internal state. Despite the evidence of the transmission of the negative emotional state from the mother to the child, we have observed some protective factors that can preserve mothers and children from the inevitability of this transmission. Mothers and children show many internal resources and skills that suggest a possible recovery as well as give the basis to think about the prevention of traumatic transmission, when the process is already underway. To conclude this work we present clinical applications for the management of traumatized mothers and their young children in order to reduce the effects of the possible transmission of trauma to the child or, where possible, to prevent it. / Diversi studi sulla trasmissione inter e tran-generazionale del trauma confermano l'evidenza della trasmissione, ma senza fornire una descrizione dettagliata del processo che potrebbe essere alla base della trasmissione diretta dalla madre al bambino. Comprendere questo processo potrebbe aiutare a pensare e promuovere la cura precoce delle madri traumatizzate e dei loro bambini. Ciò è tanto più importante nelle situazioni di trauma collettivo, come possono essere le emergenze umanitarie, dove una gran parte della popolazione è esposta a eventi traumatici estremi e ripetuti. Al fine di individuare le caratteristiche specifiche della trasmissione diretta del trauma psichico dalla madre al bambino in ambito umanitario, abbiamo reclutato ventiquattro diadi madre-bambino in tre paesi colpiti dalla crisi politico-religiosa della Repubblilca Centrafricana che ha avuto inizio nel 2013 (Centrafrica, Ciad e Camerun). Nelle ventiquattro diadi, la madre ha assistito a uno o più eventi traumatici in assenza del bambino, prima della nascita o durante la gravidanza e il bambino ha un'età compresa tra un mese e tre anni. Hanno partecipato a un' intervista semi-strutturata che abbiamo filmato per consentire la microanalisi delle interazioni cross-modali (visive, corporee, vocali) tra madre e bambino, con l'obiettivo di comprendere se durante la rievocazione dell'evento traumatico della madre, le interazioni madre-bambino si modificano e in questo caso, come. Le interazioni diadiche sono state osservate anche in una situazione di gioco libero senza la presenza d¿intervistatori. Le rappresentazioni materne e gli elementi identificatori del trauma nel discorso della madre sono stati considerati come fattori che contribuiscono alla trasmissione traumatica. I risultati delle analisi dell'interazione diadica durante l'intervista mostrano un cambiamento evidente dell'interazione nel momento della narrazione traumatica della madre. I dettagli delle differenze osservate nell'interazione madre-bambino sono presentati nella sessione dei risultati e nella discussione sono messi in relazione con il contenuto e la forma del discorso della madre, in cui è possibile vedere il ruolo delle rappresentazioni materne à proposito del bambino, nella trasmissione del trauma. L'analisi di tutti queste componenti multiple suggerisce che il trauma materno ha un impatto sulle rappresentazioni della madre a proposito del suo bambino, del rapporto che ha con lui e del mandato transgenerazionale di cui il bambino sarà portatore. Inoltre, le madri traumatizzate, invase dal proprio stato emotivo negativo, mostrano una difficoltà a interpretare correttamente le espressioni verbali e non verbali del bambino e a trovare delle risposte adeguate alle sue sollicitazioni. Questa difficoltà si traduce nella trasmissione dello stato emotivo negativo della madre al bambino, che interpreta la mancanza di risposta della madre o le risposte inadeguate alle sue richieste, come segnali negativi rispetto al suo stato emotivo. Il bambino non riesce a trovare altre strategie oltre a quella di interiorizzare lo stato emotivo negativo della madre e trasformarlo nel proprio stato emotivo interno. Nonostante le prove della trasmissione dello stato emotivo negativo dalla madre al bambino, abbiamo osservato alcuni fattori protettivi in grado di preservare le madri e i bambini dall'inevitabilità della trasmissione. Madri e bambini mostrano diverse risorse e competenze interne che ci portano a immaginare che una "riparazione" è possibile, cosi come anche la prevenzione della trasmissione traumatica, nel caso in cui il processo è già avviato. Per concludere questo lavoro, presentiamo delle proposte cliniche destinate alle madri traumatizzate e ai loro bambini, al fine di ridurre gli effetti della possibile trasmissione del trauma al bambino o, quando possibile, per impedirla.