A NEW PRODUCTION PROCESS OF POWDERS WITH DEFINED PROPERTIES BY ELECTROHYDRODYNAMIC ATOMIZATION OF LIQUIDS AND POSTPRODUCTION ELECTRICAL MIXING

A new electrical process to produce powders with defined chemical comp osition, size distribution, and morphology (shape and structure) is pr esented, first, the production of charged droplets with defined mass o f solute per unit charge is achieved by electrosprays of two liquids i n opposite polarities. Then, electrostatic forces lead to neutral drop lets with defined relative amounts of reactants arising from the initi al compositions of solutions. Due to the homogeneous mixing of liquid droplets, the same chemical reaction is induced in separate droplets c onsidered as homogeneous micro-reactors. The first part of the paper i s devoted to the validation of these principles (neutralisation, homog eneous Liquid mixing and reactivity at the micro-reactor scale). The f inal dried powder is shown to exhibit well defined properties with ref erence to macroscopic experimental parameters. The final size distribu tion varies with the solute concentration in the liquids to be sprayed and with their respective flowrates. The morphology (surface to volum e ratio, hollow-dense) mainly depends on the reactivity of mixed compo unds from droplets of opposite polarities (i.e. mainly on the products of eventual chemical reactions) but also on the evaporation and heati ng/cooling rates. Before any optimisation of the reactor, the massic y ield of the process varies from 10 to 30% for different experimental c onditions.