ED Sciences Chimiques
Aqueous graphene dispersion: formulation and stability
by Luna BOULBET-FRIEDELMEYER (Centre de Recherche Paul Pascal)
The defense will take place at 10h00 - Amphithéâtre A. Pacault Centre de Recherche Paul Pascal 116 avenue du Dr. Albert Schweitzer 33600 Pessac
in front of the jury composed of
- Carlos DRUMMOND - Directeur de recherche - CNRS - Directeur de these
- Chris EWELS - Directeur de recherche - CNRS - Rapporteur
- Patrick DAVIDSON - Directeur de recherche - CNRS - Rapporteur
- Cécile ZAKRI - Professeure des universités - Université de Bordeaux - Examinateur
- Jordi FARAUDO - Directeur de recherche - CSIC - Examinateur
Graphene, a two-dimensional carbon nanomaterial, exhibits remarkable properties in terms of electrical conductivity, mechanical strength, and thermal conductivity. These qualities make it a versatile and highly promising material for numerous application sectors, such as electronics, composite materials, and various functional coatings. However, these properties are highly dependent on the quality and synthesis method used. Liquid-phase exfoliation is one of the most suitable techniques for graphene production, upon which the company Carbon Waters has based its production system. The graphene dispersions produced through this method can be easily incorporated into various types of matrices, enabling the exploitation of graphene's properties. This thesis focuses on two different aspects of this process to deepen its understanding and control, with the aim of achieving efficient and safe large-scale industrialization. Following an initial chapter on the state of the art regarding graphene and its production techniques, the second chapter addresses the oxidation of graphenide into neutral graphene. Characterization methods such as UV-visible spectroscopy, Raman spectroscopy, transmission electron microscopy, and differential scanning calorimetry are employed to study this phenomenon. This chapter provides a thermodynamic analysis of the process, along with an initial step in controlling the oxidation through the use of microfluidics and work with different oxidants. The third chapter examines in detail the mechanisms of graphene stability in aqueous dispersion. Techniques such as potentiometric titration, isothermal calorimetric titration, zeta potential measurements in dispersion and surface, Raman spectroscopy, and atomic force microscopy are used to analyse the graphene/water interface. The experiments conducted demonstrate a charge on graphene in water, resulting from the interaction between graphene and the hydroxides and hydronium ions present in water. This pH-dependent charge is the reason for the stability of graphene in aqueous dispersion. Finally, molecular dynamics simulations are performed to model the various stages of the production process of aqueous graphene dispersions, complementing the experimental studies and providing a deeper understanding at the molecular level.
ED Sciences Physiques et de l'Ingénieur
Participatory methodology for sustainable urban renewal: Impact of microclimate on user comfort
by Zineb JKAOUA (I2M - Institut de Mécanique et d'Ingénierie de Bordeaux)
The defense will take place at 9h00 - Amphie 3 Ecole nationale supérieure d'architecture et de paysage - 740 Cours de la Libération - BP 70109 - 33405 Talence
in front of the jury composed of
- Denis BRUNEAU - Professeur des universités - ENSAP-Bordeaux - Directeur de these
- Stéphane GINESTET - Professeur des universités - INSA de Toulouse - Rapporteur
- Yann NUSSAUME - Professeur des universités - ENSA Paris-La-Villette - Rapporteur
- Lucie MERLIER - Maîtresse de conférences - Université Lyon 1 - Examinateur
- Vincent LAUREAU - Maître de conférences - ENSA Paris-Val-de-Seine - Examinateur
The escalating concerns surrounding climate change are evidenced by the exacerbation of summer heat waves, posing significant challenges to urban environments. These heat events detrimentally affect daily activities, compromise public health, and intensify energy demands for building cooling systems. Urgent action is required to transition towards resilient, environmentally friendly cities. This necessitates a reevaluation of architectural priorities towards urban redevelopment and building rehabilitation. This thesis advocates for a participatory approach that empowers the decision-makers and designers to address climate change impacts effectively. By focusing on enhancing perceived comfort and quality of life, this research aligns with the priorities of design offices and project owners. Through a scientific methodology, decision support tools are analyzed to inform urban design processes effectively. This thesis proposes to offer, to the designers and the decision-makers, tools adapted to the practice, acting from the programming to the exploitation of an urban renewal project and this, considering the local climatic aspect and the subjective aspect. The thesis employs a scientific methodology, analyzing various decision support tools to enhance urban comfort. Through sensitivity analysis of the Universal Thermal Climate Index (UTCI), significant parameters affecting comfort are identified, followed by the validation of an average perceived comfort index (APCI) at the urban scale. Utilizing a combination of in-situ measurements and standardized surveys, a perceived average comfort index (APCI) is derived and correlated with microclimatic measurements. Additionally, simplified numerical simulations at the building scale assess the impact of urban renovations on interior comfort, leveraging existing building databases and weather data adjustments. This research contributes practical methodological frameworks essential for the development of comfortable urban projects, vital for urbanization strategies better suited to future climate realities. By integrating local climatic considerations with subjective perceptions, this thesis provides designers and decision-makers with tailored tools to guide urban renewal projects towards enhanced comfort, sustainability, and resilience.