Le contexte de cette thèse est la production du vecteur énergétique hydrogène par thermolyse de la vapeur d’eau consistant en la dissociation de la molécule H2O en oxygène (O) et hydrogène (H). Le dispositif employé est une torche à plasma d’arc non transféré développée au LAEPT. Après l’exposition de la théorie sur la physique des plasmas et la spectrométrie d’émission atomique nécessaire à l’exploitation des mesures, cette thèse présente l’évolution de la torche à plasma ainsi que son environnement nécessitée par la présence de gaz instables et explosifs. Les mesures des différentes grandeurs électriques, hydrauliques et spéctrométriques ont permis la détermination des caractéristiques physique et chimique d’un plasma formé d’un mélange de vapeur d’eau – d’argon. La détermination de grandeurs telles que la température du jet plasma, la conductivité électrique, l’enthalpie massique et la densité électronique, est basée sur la comparaison entre expérimentation et théorie. / The context of this thesis is the production of hydrogen as an energy vector by steam thermolysis consisting in the dissociation of H2O molecule into oxygen (O) and hydrogen (H). The process used is a plasma torch device developed by the LAEPT. After presenting the theory of plasma physics and atomic emission spectroscopy which will help to make the most of the measured realized, this thesis will show the evolution of the plasma torch device and the experimental environment required to work with explosive and unstable gases. Some measurements like electrical, hydraulic and spectroscopy magnitudes made it possible to determine the chemical and physical characteristics of a water vapor – argon plasma. A comparison between experiments and theoretical knowledge will enable to determine the temperature of a flow of plasma, electrical conductivity, enthalpy and the electronic density.

Esta tese apresenta um modelo matemático para simulação numérica do escoamento com turbilhonamento (swirl) em tochas de plasma térmico de arco não transferido que operam em corrente contínua, assim como os resultados obtidos com as simulações para estudo de casos. O modelo magneto-hidrodinâmico (modelo MHD) bidimensional permitiu simular a interação entre o escoamento e o arco elétrico usando uma configuração axissimétrica, que abrange as seguintes regiões: entrada do gás; interior da tocha; jato de plasma livre no ambiente. O modelo foi implementado num código numérico baseado no Método dos Volumes Finitos para a solução numérica das equações governantes. Para os estudos foram simulados casos com diferentes condições operacionais (vazão de gás; intensidade de corrente elétrica; gases plasmogênicos: ar e argônio; intensidade de turbilhonamento). A fim de verificar a qualidade do modelo, alguns resultados foram comparados com a literatura e apresentaram boa concordância: a maior diferença obtida entre valores de temperatura experimentais e valores calculados foi -10%, e a média das diferenças obtidas nas comparações foi de aproximadamente ±3,2%. Os perfis de temperatura e de velocidade obtidos para a região do arco e para o jato de plasma resultante permitiram o estudo do comportamento do escoamento na tocha de plasma em diferentes condições. Conclui-se que o modelo desenvolvido é apto à realização de investigações numéricas do escoamento em tochas de plasma e dos efeitos do turbilhonamento na interação arco/escoamento. / This thesis presents a mathematical model for numerical simulation of swirling flow in DC non-transferred arc thermal plasma torches, as well as the results obtained from simulations to case studies. The two-dimensional magnetohydrodynamic model (MHD model) allowed simulate the interaction between the flow and the electric arc using an axisymmetric configuration, covering the following areas: gas inlet; inside the torch; free jet of plasma in the environment. The model was implemented in a computer code based on the Finite Volume Method (FVM) to enable the numerical solution of the governing equations. For the study, cases were simulated with different operating conditions (gas flow rate; electric current intensity; plasmogenic gases: air and argon; swirl intensity). In order to verify the quality of the model, some results were compared with the literature and showed good agreement: the biggest difference between experimental temperature values and calculated values was 10%, and the average of the differences obtained in the comparisons was approximately ±3.2%. The resulting profiles of temperature and velocity obtained for the region of the arc and the plasma jet allowed the study of the flow behavior in the plasma torch in different conditions. It is concluded that the model developed is able to carry out numerical investigations of the flow in plasma torches and the effects of swirl in the interaction arc/flow.

The aim of the Master thesis is the investigation of the influence of microwave discharge for skin wound healing. Microwave discharge used for this work was argon microwave plasma generated by the surface wave and direct vortex torch. The theoretical part is focused on basic information about plasma and processes that occur in plasma discharge under specific conditions. Plasma generates various active particles such as hydroxyl radicals, nitric oxide radicals, excited nitrogen molecules, atomic nitrogen, argon and oxygen. All of these particles together with plasma generated photons are usable in biomedical applications and summary of them is shown in the theoretical part. The experimental part is focused on the comparison of torch discharge and microwave plasma generated surface wave in skin wound healing. The model wounds on laboratory mousses were treated by plasma and wound healing was examined during 3 weeks after the plasma treatment. Both plasma systems showed healing acceleration. Application of torch discharge was proved to be the most effective method in the healing of skin defects. Additionally, determination of active particles was taken by optical emission spectroscopy. Based on these measurements, plasma parameters were determined: electron temparutare, rotational and vibrational temperatures. To determine role of different plasma active species, the treatment of indigo coloured artificial skin model was treated under various conditions by both plasma systems. Results show that the direct interaction between plasma particles is the main effect, role of radiation, only, is more or less negligible. Finally, the plasma vortex system was visualized using fast camera at selected powers and gas flows.

This diploma thesis was focused on the possibility of using a plasma nozzle to accelerate the wound healing process. The benefits of using low-temperature plasma in medicine or biomedical applications are known from many studies, and low-temperature plasma is already used to sterilize medical devices, materials or surgical instruments. Some studies also report a high potential of usinh plasma nozzle in the treatment of skin wounds. In the experimental part of this work, an in vitro wound healing test was performed using two different low-temperature plasma sources. Source No. 1 was a surface wave microwave discharge and source No. 2 was a torch microwave discharge. An in vitro scratch healing test was performed on a monolayer of HaCaT keratinocytes and testing was performed using various parameters. The influence of the plasma treatment time was monitored, as well as the influence of the plasma discharge power and also the influence of the argon working gas flow. Especially when using a torch microwave discharge, faster wound healing was recorded at most of the parameters used compared to the control. Thus, it can be said that this source appears to be potentially suitable for faster wound healing. Furthermore, in the work using the MTT cytotoxicity test, the viability of skin cells after their plasmination was also monitored using the same conditions as in the in vitro wound healing test. When performed in the standard MTT assay, none of the settings or sources used showed any cytotoxic effects on keratinocytes. LDH cytotoxicity tests were also performed concurrently to verify the accuracy of the MTT assays. The results of both tests agreed and the use of low-temperature plasma in skin treatment can be considered as safe. Overall, the results show that the plasma nozzle can find use in medicine in the healing of skin wounds and chronic defects as a potentially fast, inexpensive and effective method.

This master thesis deals with the implementation of various types of recurrent neural networks via programming language lua using torch library. It focuses on finding optimal strategy for training recurrent neural networks and also tries to minimize the duration of the training. Furthermore various types of regularization techniques are investigated and implemented into the recurrent neural network architecture. Implemented recurrent neural networks are compared on the speech recognition task using AMI dataset, where they model the acustic information. Their performance is also compared to standard feedforward neural network. Best results are achieved using BLSTM architecture. The recurrent neural network are also trained via CTC objective function on the TIMIT dataset. Best result is again achieved using BLSTM architecture.

Mittels thermischer Plasmen werden Hartstoffschichten auf der Basis von Silicium - SiC, Si3N4 sowie ternäre Si-C-N Verbindungen, aus flüssigen Single Precursoren synthetisiert. Durch die hohen Abscheideraten von bis zu 1.500 µm/h wird das hohe Potenzial der Beschichtungswerkstoffe für den Schutz von Bauteilen, die starken Verschleiß- und Korrosionsbeanspruchungen insbesondere bei hohen Temperaturen ausgesetzt sind, bei wirtschaftlich interessanten Prozesszeiten nutzbar. Der Einfluss der Precursorstruktur und der Prozessführung auf die Mikrostruktur der Schichten sowie die Abscheiderate wird systematisch erarbeitet. Zur Schichtcharakterisierung kommen Lichtmikroskopie, REM, EDX, XRD und im Fall röntgenamorpher Schichten FTIR zum Einsatz. Das Verwenden unterschiedlicher thermischer Plasmen erlaubt das Einstellen eines weiten Prozessfeldes. Mit Hilfe von Enthalpiesonden Messungen werden die Einflüsse der Maschinenparameter auf den Prozesszustand untersucht. Die Ergebnisse sind in einer Prozess - Gefügekarte zusammengefasst. Da das Gefüge der Schichten die Eigenschaften im Einsatz bedingt, bieten diese Arbeiten die Grundlage für das reproduzierbare Herstellen von Schichten mit angepassten Eigenschaften. Über die emissionsspektroskopischen Analysen zu den plasmachemischen Reaktionen gelingt es, die Schichtabscheidemechanismen in Abhängigkeit von den Prozessparametern zu klären und einen Ansatz für eine online Prozesskontrolle zu erarbeiten.

Die Habilitation befasst sich mit neuen Verfahren und Anwendungen des Thermischen Spritzens, beleuchtet anhand einer internationalen Umfrage den Forschungsbedarf der Branche und liefert zahlreiche Lösungen, die im Rahmen von grundlagenorientierten und industrienahen Forschungsvorhaben erarbeitet wurden. Der Fokus der Arbeit liegt auf der Verbesserung individueller Arbeitsschritte der Prozesskette des Thermischen Spritzens, wobei Ergebnisse aus den Bereichen Werkstoffentwicklung, Prozessoptimierung, Qualitätssicherung und Nachbearbeitung zusammengeführt und durch konkrete Anwendungsbeispiele hinterlegt werden. Im Detail werden die Aspekte Herstellung leistungsfähiger und preiswerter Spritzzusätze (Wasserverdüsung von Metallpulvern, Hochenergiekugelmahlen, Agglomerieren und Sintern sowie Fülldrahtherstellung), die Verbesserung der Prozessführung (numerisch optimierte Spritzbrenner und automatisierbare Online-Prozessdiagnostikmethoden) und die Steigerung der Leistungsfähigkeit der Beschichtungen durch mechanische Nachbearbeitung sowie Versieglung behandelt. Anwendungsbezogen werden das Beschichten von Hochleistungspolymeren und CFC-Leichtbaustrukturen untersucht. Um Anknüpfungspunkte für weiterführende Forschungsarbeiten zu schaffen, schließt die Arbeit mit der Darstellung von Entwicklungstrends und zeigt Arbeitsgebiete auf, die perspektivisch von thermisch gespritzten Schichten profitieren können.

In der vorliegenden Habilitationsarbeit wurden technisch-konstruktive Lösungsansätze basierend auf einem entwickelten strömungs-thermomechanischen/magneto-hydro-dynamischen Simulationsmodell zur Entwicklung/Charakterisierung eines physikalischen Prozesswirkprinzips des betrachteten Mikro- und Hochleistungs- sowie Orbital-Plasma-Schweißprozesses und dessen physikalischer Effekte entwickelt. Dabei wurden die differenten Einflussgrößen beim Plasmaschweißprozess erfasst, analysiert und ihre Wirkung auf Schweißprozessverhalten und Brennerkonstruktion charakterisiert. Die damit gewonnenen Ergebnisse wurden zur werkstofflichen, technisch-konstruktiven Entwicklung der Brennerkopfmodelle hinsichtlich der Ausführungsgeometrien des Prozessgaszuführungs- und Brennerkühlsystems genutzt. Im Rahmen des erarbeiteten thermomechanischen Simulationsmodells wurden die beim Plasma-Auftragschweißen von Verbundbauteilen auftretenden Temperaturfelder, Verformungen und Eigenspannungen vorausbestimmt, untersucht und analysiert. Mittels des erarbeiteten Simulationsmodells wurden werkstoffliche, konstruktive und fertigungstechnische Maßnahmen zur Minimierung/Beeinflussung schweißbedingter Verformungen und Eigenspannungen simulativ untersucht und bewertet. / In this work, technical and constructive solutions were developed based on simulation models (process and structural) for fluid mechanical, thermomechanical and magneto-hydrodynamic effects. The simulation process included improving and characterising the physical operating principles for micro plasma welding, high performance plasma welding and orbital plasma welding. Also, the physical effects for the above plasma welding processes were studied and analysed. From these different physical properties of the parameters for the plasma welding processes, and their effects on plasma welding process behaviour and torch design were analysed and characterised. The results were used for the development and construction of plasma welding torch models, which included material selection and geometrical design such as, process gas supply design, torch cooling system design, and other related torch designs. By developing the thermomechanical simulation model, deformations and residual stresses that were generated by heating during the plasma welding process were investigated and analysed. The developed thermomechanical model included material, structural and welding specifications such as buffering and preheating. Simulations utilizing this model were used in order to reduce the residual stresses and deformations of the welded components.

En tant que technologie de projection thermique avancée, la projection plasma sous basse pression (LPPS) permet d'obtenir des revêtements de haute qualité et peut combler l'écart d'épaisseur entre les technologies de projection thermique conventionnelles et les procédés de couche mince standard. En outre, LPPS permet de construire des revêtements uniformes avec diverses microstructures; le dépôt a lieu non seulement à partir des éclaboussures liquides, mais aussi à partir des amas nanométriques ainsi que de la phase vapeur en fonction des conditions opérationnelles. Afin de continuer à améliorer et à développer le procédé LPPS, cette recherche vise à le combiner avec les procédés émergents de projection plasma en suspension et de projection plasma réactif. Il devait à la fois fournir deux nouveaux processus intégrés et réaliser des revêtements à structure fine avec des microstructures uniques et des performances élevées.Une torche à plasma bi-cathode (laboratoire LERMPS, UTBM, France) à mode d'injection axiale a été conçue et construite pour le LPPS, dont la puissance maximale en entrée du plasma a pu atteindre 80 kW. En utilisant cette nouvelle torche, soit la suspension à très fines particules, soit les poudres micrométriques ont pu être injectées dans le centre du plasma à basse pression. En conséquence, le transfert de chaleur et de masse entre le jet de plasma et les matériaux pulvérisés a été amélioré.La torche à plasma bi-cathode axiale a été appliquée d'abord pour pulvériser deux types de charges de YSZ, y compris la suspension de YSZ et les poudres agglomérées de YSZ. Les résultats ont indiqué que tous les revêtements YSZ présentaient des structures relativement denses en raison de la grande vitesse des particules sous faibles pressions. Les revêtements ont été composés des particules fondues, des particules agglomérées ainsi que du dépôt en phase vapeur. Il a été constaté que le degré de vaporisation de YSZ a été augmenté en utilisant une taille de particule plus fine, une pression ambiante plus basse, une distance de pulvérisation plus longue et une puissance de plasma plus élevée. En outre, tous les revêtements YSZ ont subi une transformation de phase significative d'une phase monoclinique à une phase tétragonale, et le degré de transformation était proportionnel au degré de vaporisation. Cependant, les propriétés mécaniques des revêtements résultants ont des comportements opposés. Les revêtements YSZ préparés à partir des particules agglomérées, qui avaient une plus grande taille de gouttelettes et moins de dépôt en phase vapeur, présentaient une dureté et un module de Young plus élevés que les revêtements YSZ fabriqués à partir d'une suspension fine.Une autre torche à plasma à haute énergie O3CP (Oerlikon Metco, Suisse) a été utilisée pour synthétiser in situ les revêtements de TiN sur des alliages de Ti-6Al-4V par projection de plasma réactive à très basse pression. Les poudres de Ti pur ont été pulvérisées dans une atmosphère de N2 sous une puissance de plasma d'entrée de 120 kW. Les revêtements TiN hybrides structurés ont été synthétisés, ce qui n'était pas le cas auparavant avec d'autres procédés de projection thermique. Il est connu que la réaction de nitruration se produisait non seulement dans le jet de plasma mais aussi sur le substrat. De plus, avec l'augmentation de la distance de pulvérisation, l'effet de nitruration a été affaibli et la structure hybride du revêtement de TiN a changé de laminaire dense en colonne poreuse, en function du degré de vaporisation supérieur, de la concentration de réactive inférieure et du substrat plus froid.. Néanmoins, ils ont également permis d'améliorer les propriétés mécaniques du substrat Ti-6Al-4V. / As an advanced thermal spray technology, low-pressure plasma spray (LPPS) allows obtaining high-quality coatings and can bridge the thickness gap between conventional thermal spray technologies and standard thin film processes. Moreover, LPPS permits to build uniform coatings with various microstructures; deposition takes place not only from liquid splats but also from nano-sized clusters as well as from the vapor phase depending on operational conditions. In order to further improve and develop the LPPS process, this research aims to combine it with the emerging suspension plasma spray and reactive plasma spray processes. It was expected to both provide two novel integrated processes and achieve fine-structured coatings with unique microstructures and high performance.A bi-cathode plasma torch (LERMPS lab, UTBM, France) with an axial injection mode was designed and built for LPPS, whose maximum input plasma power was able to reach to 80 kW. By using this new torch, either the very fine-particle suspension or the micro-sized powders was able to be injected into the plasma center under low pressures. As a result, the heat and mass transfer between the plasma jet and the sprayed materials were enhanced.The axial bi-cathode plasma torch was applied firstly to spray two kinds of YSZ feedstocks, including the YSZ suspension and the YSZ agglomerated powders. The results indicated that all the YSZ coatings exhibited relatively dense structures due to the high velocity of particles under low pressures. The coatings were composed of the melted particles, the agglomerated particles as well as the vapor deposition. It was found that the vaporization degree of YSZ was increased by using smaller particle size, lower ambient pressure, longer spraying distance and higher plasma power. In addition, all the YSZ coatings undergone a significant phase transformation from a monoclinic phase to a tetragonal phase, and the transformation degree was proportional to the vaporization degree. However, the mechanical properties of the resulting coatings had the opposite behaviors. The YSZ coatings prepared from the agglomerated particles, which had a bigger droplet size and less vapor deposition, showed a higher hardness and Young's modulus than the YSZ coatings fabricated from fine suspension did.Another high-energy plasma torch O3CP (Oerlikon Metco, Switzerland) was employed to in-situ synthesize the TiN coatings on Ti-6Al-4V alloys by reactive plasma spray under very low pressure. The pure Ti powders were sprayed into an N2 atmosphere under an input plasma power of 120 kW. The hybrid structured TiN coatings were synthesized, which was not previously achieved with other thermal spraying processes. It was known that the nitriding reaction occurred not only in the plasma jet but also on the substrate. Additionally, with increasing spraying distance, the nitriding effect was weakened, and the hybrid structure of TiN coating changed from dense laminar to porous columnar, according to the higher vaporization degree, lower reactant concentration and colder substrate. Nevertheless, they also were able to improve the mechanical properties of the Ti-6Al-4V substrate.

Les composites de type Cf/C sont utilisés en tant que pièces structurales dans les propulseurs spatiaux du fait de leurs excellentes propriétés mécaniques dans le domaine des très hautes températures. Néanmoins, l’atmosphère oxydante et corrosive créée lors du décollage des lanceurs et les hauts flux gazeux dégradent ces matériaux. Afin d’améliorer les performances de ces matériaux vis-à-vis de l’oxydation/corrosion, une protection composée de céramiques ultra-réfractaires (dites UHTC) peut être appliquée. Pour une efficacité de protection optimale, des phases UHTC ont été introduites en tant que constituants de la matrice. Dans ces travaux de thèse, la matrice a été réalisée par l’intermédiaire d’un procédé d’élaboration en phase liquide combinant : (i) l’introduction de poudres et (ii) la densification par infiltration réactive d’un métal fondu. La composition de la matrice appartient au système (B;C;Si;Zr). La caractérisation des matériaux après élaboration a permis de comprendre les mécanismes d’infiltration et les réactions permettant de mieux contrôler la composition chimique et la répartition des phases. Des essais sous torche oxyacétylénique ont été utilisés pour se placer dans des conditions proches de l’application visée. La caractérisation post-test des matériaux a permis d’évaluer l’efficacité de la protection dans le cas d’une utilisation unique et également d’une possible réutilisation. Les résultats en oxydation/corrosion ont permis de classer les matériaux en fonction de leur efficacité de protection. / Since many decades, Carbon/Carbon composites are used as structural parts in rocket engines due to their excellent thermomechanical properties. However, under highly oxidizing/corrosive atmosphere and high gas flow rates, carbon suffers from severe oxidation. To improve oxidation resistance of these composites, Ultra High Temperature Ceramics (UHTC) can be used as a protection. To protect the whole composite, the introduction of UHTC as a matrix has been done using a liquid phase process combining: (i) slurry infiltration process and (ii) reactive melt infiltration. Matrix constituents belong to the (B;C;Si;Zr) system. Material characterisation allowed a better understanding of the infiltration mechanisms and of the phase distribution and composition in respect to the processing conditions. To select the best composition, oxyacetylene torch testing has been done to recreate spacecraft launch environmental conditions. Post-test characterisation has been done to evaluate protection efficiency of each matrix composition for single use and possible reuse. Finally, advantages and drawbacks assessment of each composition allowed to highlight the most protective composition and phase distribution.