Expanded micro-particles by supercritical antisolvent precipitation: Interpretation of results

Supercritical antisolvent (SAS) micronization has been used to obtain nanoparticles and micro-particles of several kinds of materials. Sometimes hollow expanded micro-particles have also been obtained. This work is focused on the analysis of this last morphology. We organized literature data and our previous experiments and we added new experiments on previously tested compounds and on compounds never tested before.As a result, expanded micro-particles using several compounds belonging to different categories and precipitated from different solvents in laboratory and pilot scale plants were obtained with diameters between about 10 and 180 μm. They also showed different sub-structures: uniform or nanostructured surface or constituted by microcrystals. Also expanded micro-particles of coprecipitates were obtained. To explain all the available experimental evidences, we propose a mechanism of hollow expanded micro-particles formation, based on thermodynamic and mass transfer interactions.