Supercritical Anti-Solvent Micronization: Control of Morphology and Particle Size

Supercritical antisolvent precipitation has been used to micronize several kinds of materials. Nanoparticles with mean diameters in the 30-200 nm range and microparticles in the 0.2-20 µm range are the most frequently obtained morphologies. Sometimes, hollow expanded microparticles with diameters between about 10 and 200 µm and crystals having various morphologies have been obtained. In this work, the relation between vapor liquid equilibria and the observed morphologies has been performed; possible formation mechanisms have been proposed. If the material is precipitated from a supercritical gaseous phase, expanded microparticles can be obtained; whereas, if the process is carried out at supercritical conditions, there is a competition between jet break-up and liquid surface tension vanishing characteristic times. If surface tension disappears before the jet break-up, nanoparticles are formed from a gas plume; otherwise, micrometric droplets generate spherical micrometric particles.