10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Production of Homogeneous Particles by Controlled Neutralization of Electrosprays

Antonio Carrasco-Munoz, Elena Barbero-Colmenar, Eszter Bodnar, Jordi Grifoll, JOAN ROSELL-LLOMPART, Universitat Rovira i Virgili

     Abstract Number: 1375
     Working Group: Materials Synthesis

Abstract
Electro-hydrodynamic atomization (EHDA) of liquids, or electrospray, is a promising way of generating uniformly sized micro- and nano-drops, as building blocks for the production of nanoparticles and nanostructured coatings. In this technique, a liquid meniscus is electrified to form a microscopic jet that spontaneously breaks up regularly, resulting in uniformly sized drops. However, EHDA has not yet been implemented industrially much, due to the lack of robust atomization methods that can mass-produce uniform droplets. One of the challenges is to overcome the high electrical charge carried by the droplets, which leads to several issues. Specifically, as solvent evaporates from droplets containing a non-volatile solute, the charge concentrates till a limit (Rayleigh limit) is reached, at which they explode, distorting the shape of the resulting particles and the size distribution uniformity.

To overcome this drawback, we have explored experimentally and numerically the implementation of controlled sources of ions of opposite polarity to the electrospray droplets in order to neutralize them. The simulation includes a 3D Lagrangian model for droplet motion, a droplet-ion neutralization kinetics according classical electrostatic charging theories, and a gas velocity field obtained with COMSOL 5.2. Additional features are the coalescence of droplets with low electrical charge of the same or opposite sign, and droplet evaporation.

When ions are injected from the counter electrode zone under the influence of a gas velocity field, controlled neutralization of the droplets can be achieved and thus Coulomb explosions can be avoided. The forces that drive the droplets progressively change from electrical to gas drag as the droplets progress from the needle to the counter electrode. Experimentally, we find that the aerosol extraction efficiency is dramatically improved when ions are injected into the electrospray.