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Theses
Ablation laser impulsionnelle : source de nanoparticules en vol et de films minces : Développement de matériaux nanostructurés à base d'argent, de vanadium et de dioxyde de vanadium
Ablation laser impulsionnelle : source de nanoparticules en vol et de films minces : Développement de matériaux nanostructurés à base d'argent, de vanadium et de dioxyde de vanadium
Abstract : The work presented in this thesis is focused on the development of an experimental setup for the synthesis of nanoparticles (NPs) by a physical route, based on the laser vaporization of a target and followed by the rapid quenching of the plasma plume. Combining such a NP source with conventional laser ablation makes possible to synthesize silver and vanadium NPs in stacks on substrates or embedded in different matrices synthesized by laser ablation. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis revealed crystallized spherical NPs relatively monodisperse in size (~ 3 nm in diameter) depending on the residence time in the nucleation cavity. The synthesis of amorphous Al2O3 nanocomposites doped with metallic silver NPs of different sizes showed the influence of the size on the position and the width of the surface plasmon resonance (SPR) of the nanostructured material. The NPs keep their original shape during impact on the substrate, leading to highly porous NPs stacks (approximately 50%). Vanadium dioxide nanoparticles (VO2 NPs) have been synthesized by annealing vanadium NPs stacks. Due to their individual behaviour, VO2NPs exhibit lower transition temperature (~ 50°C) and larger hysteresis width (~ 10-30°C) than thin films (transition temperature around 68°C and hysteresis width around 3°C). By coupling a PLD thin film and a NPs stack, it is possible to combine their properties and obtain a nanostructured material having a step transition.
Keywords :
Nanostructured materials
Vanadium dioxide
File
2017LIMO0025.pdf
Version validated by the jury (STAR)