AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Controlling the Microphysical Processes Occurring During Droplet Drying
JONATHAN P. REID, Florence Gregson, Jim Walker, Rachael E.H. Miles, University of Bristol
Abstract Number: 97 Working Group: Nanoparticles and Materials Synthesis
Abstract Droplet routes to fabricate structured nano- and micro-structured particles are routinely used in processes such as spray drying. Starting from simple solute-solvent droplets or from more complex colloidal dispersions, the evaporative drying can lead to the formation of monodisperse crystalline, amorphous or porous particles of simple or complex morphology. The final structure and morphology are dependent on the microphysical processes occurring on millisecond to second timescales. Evaporation rates are dependent on factors such as the gas phase temperature and composition, the surface and bulk composition of the droplet, the dependence of diffusion constants in the particle bulk on composition, and the nucleation and growth rates of crystal structures. Measurements of single droplet evaporation can provide important insights into the detailed microphysical processes at work. We will report on the use of single particle instruments to study the evolving composition, size and morphology of micron-sized droplets during the evaporative drying process. Using an electrodynamic balance to investigate evaporation processes occurring in <1 s, we will begin by exploring the success with which the evolving composition and size of evaporating droplets can be predicted from continuum models that incorporate the interplay of heat and mass transfer. Studies will focus on solution droplets of increasing complexity, increasing the number of solvents of varying volatility. The influence of droplet composition (e.g. the presence of a surface film), drying rate and temperature on the formation of crystalline or amorphous particles will be reported, comparing involatile inorganic or organic solute containing aqueous droplets, before progressing to the drying kinetics of droplets containing silica nanospheres. Finally, we will introduce a new technique for studying drying kinetics on millisecond timescales, reporting measurements of time-dependent size and composition.