Etude des modes de résonance d'une torche à plasma d'arc associée à une injection synchrone pour la réalisation de dépôts par voie liquide

Abstract : Suspension plasma spraying permits to elaborate finely structured coatings with graded properties which address the needs, for example, in the photocatalytic applications, the solid oxide fuels or the thermal barrier coatings. However, the plasma torches, even powered by dc regulated sources, generate highly fluctuating plasma jets. These instabilities result in large variations in dynamic and heat transfers to particles, what decreases the reproducibility and reliability of the method. Consequently, the special efforts have to be devoted to ameliorate the suspension plasma spraying method and, thus, the properties of the coatings. In recent years, the research has been focused on the improvement of heat and momentum transfers between material and plasma by means of the development of new non-conventional torches and the reduction of arc instabilities. The following dissertation presents a new approach to the suspension plasma spraying. The profound studies of the plasma instabilities are performed, what leads to the production of the pulsed laminar plasma jet characterized by high modulation of the specific enthalpy. These regular plasma oscillations are combined with phased injection of suspension, what is achieved by using the ink-jet printer triggered by the arc voltage signal. The results are evaluated by time-resolved imaging system and the time-resolved emission optical spectroscopy. This new method presents the possibility to control heat and momentum transfers between the particles and the plasma.
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Joanna Krowka. Etude des modes de résonance d'une torche à plasma d'arc associée à une injection synchrone pour la réalisation de dépôts par voie liquide. Matériaux et structures en mécanique [physics.class-ph]. Université de Limoges, 2014. Français. ⟨NNT : 2014LIMO0014⟩. ⟨tel-01127257⟩

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