Ph'D defense Mme Camille Angelini
Mlle Camille Angelini will present her thesis "Whitening of aluminum by anodization in Ematal bath : Study of the involved mechanisms"
Abstract : Aluminum anodizing is a chemical surface conversion of the metal during an electrolysis process. When anodizing under acidic conditions, this chemical conversion induces the surface transformation of aluminum into alumina. The produced alumina layer is an electrical insulator which could be dense or porous
depending on the experimental conditions. The porous character of the modified surface allows dyes to be integrated. Nowadays, although efficient to get certain colors, this process has to be improved for light colors. The aim of this PhD work is to determine the electrochemical and chemical conditions to lighten aluminum substrats with a prior anodizing process in a bath called Ematal, patented in 1940. This patented electrolyte contains weaks acids and a titanium complex leading to opaque grey layers onto the Al substrate. Nevertheless, this interesting Ematal mixture hasn't been extensively studied. We particularly focused on the role of the titanium complex present in the bath, which could act as TiO2 precursor in order to reach lighter substrate.
The first part of this thesis has been dedicated to the study of the oxide layer growth in the Ematal bath with and without the titanium complex and the impact of the experimental conditions to control the porous character of the electroproduced layer. Surprisingly, it has been noticed that the titanium complex doesn't integrate the anodic layer whatever its concentration. In addition, the structure and the color of the coatings are poorly dependent on the presence of the TiO2 precursor. However, this complexe is mandatory to ensure the growth of well structured nanoporous layers. In order to better understand its role during the anodization process, impedance measurements on anodized samples have been performed. It has highlighted that the titanium complex contributes to the growth of oxide layer ensuring a better protection to the aluminium substrat towards corrosion. In a second part of this work, two post treatments have been investigated to lighten the anodic layers synthetised using the Ematal bath. Attempts to impregnate TiO2 nanoparticles into coatings pores have been carried out by electrophoresis. In parallel, the immersion of anodized samples into an acidic bath have been performed. Changing/exploring different experimental conditions (solvent, current density ...) the integration of the titanium based dyes has not been achieved by electrophoresis. On the other hand, the immersion of the anodized substrate in acidic bath leads to a 15 % gain on the clarity parameter of the aluminum. Immersion applied for longer period results in a 20 % lightening in good agrement with the industrial objectives. Nevertheless, this immersion lowers the interactions between the lighten oxide layer and its substrat reaching to the debonding of the modified alumina layer
Directrice et co-directeur de thèse : Corine Bas et Jean-claude Leprêtre
Jury members :
depending on the experimental conditions. The porous character of the modified surface allows dyes to be integrated. Nowadays, although efficient to get certain colors, this process has to be improved for light colors. The aim of this PhD work is to determine the electrochemical and chemical conditions to lighten aluminum substrats with a prior anodizing process in a bath called Ematal, patented in 1940. This patented electrolyte contains weaks acids and a titanium complex leading to opaque grey layers onto the Al substrate. Nevertheless, this interesting Ematal mixture hasn't been extensively studied. We particularly focused on the role of the titanium complex present in the bath, which could act as TiO2 precursor in order to reach lighter substrate.
The first part of this thesis has been dedicated to the study of the oxide layer growth in the Ematal bath with and without the titanium complex and the impact of the experimental conditions to control the porous character of the electroproduced layer. Surprisingly, it has been noticed that the titanium complex doesn't integrate the anodic layer whatever its concentration. In addition, the structure and the color of the coatings are poorly dependent on the presence of the TiO2 precursor. However, this complexe is mandatory to ensure the growth of well structured nanoporous layers. In order to better understand its role during the anodization process, impedance measurements on anodized samples have been performed. It has highlighted that the titanium complex contributes to the growth of oxide layer ensuring a better protection to the aluminium substrat towards corrosion. In a second part of this work, two post treatments have been investigated to lighten the anodic layers synthetised using the Ematal bath. Attempts to impregnate TiO2 nanoparticles into coatings pores have been carried out by electrophoresis. In parallel, the immersion of anodized samples into an acidic bath have been performed. Changing/exploring different experimental conditions (solvent, current density ...) the integration of the titanium based dyes has not been achieved by electrophoresis. On the other hand, the immersion of the anodized substrate in acidic bath leads to a 15 % gain on the clarity parameter of the aluminum. Immersion applied for longer period results in a 20 % lightening in good agrement with the industrial objectives. Nevertheless, this immersion lowers the interactions between the lighten oxide layer and its substrat reaching to the debonding of the modified alumina layer
Directrice et co-directeur de thèse : Corine Bas et Jean-claude Leprêtre
Jury members :
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Nadine Pébère, Directeur de recherches, CNRS, Rapporteur
Emmanuel Rocca, Maître de conférences, Université de Lorraine, Rapporteur Virginie Roche, Maître de conférences, UGA, Examinatrice Yannick Champion, Directeur de recherches, CNRS, Invité Stéphane Baumhauer, Directeur Technique Société Catidom, Invité Corine Bas, Co-directrice de thèse, USMB Jean-Claude Leprêtre, Directeur de thèse, UGA |
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Date infos
Defense 3 March 2022 at 9HAddress of the defense : Amphithéâtre B9-G-160, à l’IUT de Chambéry, 28 avenues de lac d’Annecy, 73370 Le Bourget-du-Lac