METHOD AND APPARATUS FOR PREPARING MONO-DISPERSED ULTRAFINE PARTICLES BY RAPIDLY COOLING SUPERCRITICAL SOLUTION

PROBLEM TO BE SOLVED: To provide a method and an apparatus for preparing a suspension comprising mono-dispersed ultrafine particles of from nanometer order to micron order without using an organic solvent, which are capable of completely recovering the ultrafine particles by instantaneously preventing their agglomeration and crystal growth as soon as they are formed. SOLUTION: In the method, a supercritical solution is rapidly cooled by injecting a coolant with a surfactant dissolved therein into the supercritical solution and by externally cooling it to form ultrafine particles. Thereby, the surfactant dissolved in the coolant is adsorbed on the surface of the precipitated particles and instantaneously suppresses the agglomeration and crystal growth of the resulting particles enabling them to remain as ultrafine particles which can be recovered as an ultrafine particle suspension of the resulting ultrafine particles uniformly mono-dispersed in an aqueous solution. COPYRIGHT: (C)2007,JPO&INPIT