Characterization of aerosols produced by laser-matter interaction during paint-stripping experiments by laser

Laser ablation is one of the physical processes that are being considered for paint stripping in possibly contaminated areas, especially for decommissioning and dismantling of nuclear facilities. In this regard, the knowledge of 'ablation products', consisting of particles and gases, is an important issue.The numeric and weight concentration of particles, their size distribution, their morphology and their density have been determined for laser ablation of two wall paints. The main gas species have also been identified. The aerosol is composed of nano-particles, of which the number is predominant, and sub-micron particles. Their morphologies and their chemical composition are very distinct: carbon aggregates have been identified, as well as spherical particles of titanium dioxide. These results show that nano-scale aggregates come from the vaporization of the paint polymer, whereas sub-micron particles are due to mechanical ejection of titanium dioxide particles. The expansion of the plume resulting from laser-paint interaction has been monitored by means of three optical techniques: light extinction, scattering and emission. The frames show the propagation of a shock wave followed by the ejection of matter with a specific 'mushroom' shape. Measurements based on these results show that the peripheral part of the plume contains the primary particles of carbon aggregates; it is the warmest area, which reaches a few thousands Kelvin degrees. Its central part is composed of titanium dioxide spherical particles. (author)