ED Sciences Chimiques
Laser processing of copper/diamond composites
by Emmanuel LOUBÈRE (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at 10h00 - Amphithéâtre iCMCB-CNRS 87 Avenue du Dr Albert Schweitzer 33608 Pessac
in front of the jury composed of
- Cyril AYMONIER - Directeur de recherche - ICMCB, CNRS - Examinateur
- Yongfeng LU - Professeur des universités - University of Nebraska Lincoln - Examinateur
- Hanlin LIAO - Professeur des universités - Université de Technologie de Belfort Montbéliard, ICB-PMDM-LERMPS - Rapporteur
- Yann LEPETITCORPS - Professeur des universités - Laboratoire des Composites Thermo Structuraux - Examinateur
- Andrzej KUSIAK - Maître de conférences - Institut de Mécanique et d'Ingénierie de Bordeaux (I2M) - CoDirecteur de these
- Karl JOULAIN - Professeur des universités - Université de Poitiers - Institut P' - Rapporteur
- Kim VANMEENSEL - Associate Professor - Katholieke Universiteit, Leuven - Examinateur
- Jean-François SILVAIN - Directeur de recherche - Université de Bordeaux - Examinateur
With the increasing miniaturization of electronic components, more and more heat has to be dissipated from electronic devices. Without optimal heat dissipation, components overheating can significantly reduce their lifetime and reliability. To meet this need, new thermal management materials, with tailored thermal properties and mechanical strength, have to be developed. Copper (Cu) matrix composites reinforced with diamond (D) particles have the potential to be used as the next-generation of thermal dissipation materials, due to their potentially high thermal conductivity and tailorable coefficient of thermal expansion (CTE). Indeed, Cu has been historically used as heat sink as it is the second-best thermal conductor among metals (λCu = 400 W/(m·K)) after silver. On the other hand, diamond has the highest thermal conductivity (between 1000 and 2500 W/(m·K)) of all bulk materials known in nature, and a low CTE (close to 2 x 10⁻⁶/K). For this type of chemically non-reactive copper-carbon (Cu-C) system, it is necessary to improve the reactivity of the Cu-C interface, in order to enhance the heat transfer between the Cu matrix and the C reinforcement. Furthermore, the use of conventional manufacturing processes, such as powder metallurgy, limits the production of Cu/D composites to simple shapes (cylinders or cubes). The extreme hardness of diamond makes machining very complex, and almost impossible, with conventional machining methods. The development of additive manufacturing (AM) and ultra-short pulse lasers allows to manufacture and process parts with complex shapes, whatever the nature of the material. This study aims to optimize the processing of Cu/D composite materials for thermal management applications using a laser-based AM process, and their post-processing with an ultra-short pulse laser. First, multilayer and Cu/carbon fiber model composite materials are developed by magnetron sputtering and powder metallurgy, respectively. These model materials are then thermally characterized by photothermal radiometry to assess the influence of the chemical nature of the Cu-C interface on the thermal conductivity of the Cu/C system. Next, the 3D printing of Cu-based materials and Cu/D composites, using the laser powder bed fusion (LPBF) AM process, is investigated using an infrared continuous wave laser. This laser has a constant spatial intensity distribution profile over the entire spot diameter, known as the “top hat” profile. Finally, the feasibility of polishing rough surfaces of Cu and Cu/D composite materials with femtosecond pulsed laser is investigated, with the aim of achieving a surface with a submicron average roughness.
ED Sciences de la Vie et de la Santé
Study of pesticide degradation by Pulsed Light process combining an analytical chemistry and ecotoxicology approach. Application to viticultural effluents
by François CLAVERO (Oenologie)
The defense will take place at 14h00 - Amphithéatre 210 Chem. de Leysotte, 33140 Villenave-d'Ornon
in front of the jury composed of
- Rémy GHIDOSSI - Professeure des universités - Université de Bordeaux - Directeur de these
- Florence GERET - Professeure des universités - Institut national Universitaire Champolion - Rapporteur
- Marie-Virginie SALVIA - Maîtresse de conférences - Université de Perpignan - Rapporteur
- Régis GOUGEON - Professeur des universités - Université de Bourgone - Examinateur
- Julien PARINET - Chercheur - Agence National de sécurité sanitaire de l'alimentation, de l'environnement et du travail - Examinateur
Viticulture generates significant volumes of wastewater contaminated with pesticides. Current processes for treating these effluents have limitations (energy-consuming, limited efficiency, and production of waste concentrated in pesticides). Pulsed light (PL) has recently demonstrated potential for the degradation of some pesticides. The objective of this work was to develop a continuous process for treating viticultural effluents using PL by combining an analytical chemistry and ecotoxicology approach. First, static PL treatment of 20 pesticides widely used in viticulture revealed the formation of 74 degradation products. These pesticides were at least 93.5% degraded. Through this study, optimization of the operating conditions for PL treatment led to reductions in acute toxicity for all models studied (bacteria, algae, and fish). Next, optimization of PL in continuous mode enabled the degradation of over 99% of the 20-pesticide cocktail. The optimized treatment was applied to 3 effluent samples, resulting in a significant reduction in toxicity for all three biological models. However, high toxicity persisted in all treated samples due to the presence of trace metal elements (TME) in the effluents. Finally, LC-HRMS analyses allowed the identification of 82 degradation products using chemometric tools, and 47 structures were proposed. The individual toxicity of the photoproducts, estimated by ECOSAR, indicated a reduction in both acute and chronic toxicity for algae and fish. However, only two photoproducts were estimated non-toxic. These results confirm the efficacy of PL in degrading most of the studied pesticides and reducing the toxicity of treated waters. Coupling PL with coagulation-flocculation-filtration processes to remove TMEs, along with the addition of hydrogen peroxide, could further enhance this efficiency, reduce energy costs, and improve the degradation of photoproducts. Further studies are needed to assess the acute and chronic effects of this process on various links within the aquatic trophic chain.