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Effets des ultrasons sur l'élaboration de revêtements électrolytiques d'argent et d'argent-étain : nucléation, croissance et structures cristallines

Abstract : Properties of electrodeposited coatings are directly related to their morphology and structure, which are strongly influenced by the presence of organic additives and electrodeposition parameters (current density, direct vs pulsed current). An attractive possibility results in the use of ultrasound during electrodeposition, to influence the microstructure without using chemicals, or at least, by reducing their quantity. Many works in the literature describe the beneficial effect of ultrasound in plating, reporting finer grains, reduced porosity and increased brightness.In the present study, conventional cyanide silver bath as well as silver-tin electrolyte specifically formulated were used. Coatings were characterized by several methods such as SEM-EDS, XRD, and EBSD. These analysis were performed to evaluate the ultrasound (20 and 575 kHz) effect on the morphology, crystalline structure and elementary composition of coatings. To insulate the effect of cavitation bubbles from convection flow, all coatings had to be elaborated exactly with the same agitation in absence or presence of ultrasound, at an “equivalent flow” condition.During silver electrodeposition, ultrasound affect coatings properties by promoting specifics morphology and crystalline structure obtained by lateral growth. The thickness uniformity was measured on substrates with complex shapes. In this case, the use of low-frequency ultrasound allow to reduce thickness dispersion to a value close to 10%. The electrodeposition of silver-tin under sonication bring significant changes on the coatings appearance, homogeneity and composition. These modifications concerns both the elementary composition and the distribution of crystalline phases. Moreover, this behaviour is strongly dependant of the ultrasound frequency.
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https://tel.archives-ouvertes.fr/tel-01816923
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Submitted on : Friday, June 15, 2018 - 9:29:05 PM
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Aymeric Nevers. Effets des ultrasons sur l'élaboration de revêtements électrolytiques d'argent et d'argent-étain : nucléation, croissance et structures cristallines. Autre. Université Bourgogne Franche-Comté, 2017. Français. ⟨NNT : 2017UBFCD011⟩. ⟨tel-01816923⟩

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