Carbon Nanoparticles from Laser Pyrolysis
Résumé
Carbon nanoparticles synthesised by laser pyrolysis of hydrocarbons in a flow reactor have been investigated as a function of laser power. Samples are cross-characterised by high resolution transmission electron microscopy (HRTEM) and infrared (IR) spectroscopy. Nanoparticles appear highly aromatic in character in all the experimental conditions explored here. As the flame temperature in the interaction zone increases, the nanoparticles evolve drastically from poorly organised, highly hydrogenated samples toward turbostratic concentric particles of carbon. The multiscale organisation of the samples and its evolution with the synthesis parameters are quantitatively determined and correlated to IR properties through an original development of HRTEM image analysis. The multiscale organisation does not reduce to the classical view of assemblies of basic structural units (BSU) of aromatic bricks. More refined models are proposed where non-stacked aromatic layers play a noticeable role and lead to a better understanding of the samples optical properties. Possible contribution to a better understanding of carbon cosmic dust is discussed from an astrophysical point of view.