Spherical microparticles production by supercritical antisolvent precipitation: Interpretation of results

Supercritical antisolvent micronization has been the subject of many works aimed at the production of precipitates with controlled particle size and morphology. Several morphologies have been observed; but, the production of spherical micrometric particles has been the major objective of most of the studies performed. Therefore, in this work, literature data analysis on spherical and related morphologies has been performed. The ranges of process conditions at which spherical microparticles have been obtained have been listed and discussed. A possible formation mechanism is proposed that is based on the competition between jet break-up and liquid surface tension vanishing characteristic times. If surface tension disappears before the jet break-up, nanoparticles formation by "gas to particle" precipitation is observed; if atomization develops first, micrometric droplets drying and spherical micrometric particles formation is the prevailing process. Modifications of the morphology of spherical particles can be explained by the further evolution of the solid material by superimposition of fast crystallization kinetics that can produce rough surfaces, nanocrystalline surfaces, spherical geometry collapse.