Measurements of Particle Phase Transitions Using Synthesized Nanoparticles. Implications for Particle Viscosity
Authors
Nicholas Rothfuss — NCSU
Markus D Petters — North Carolina State University
Paul J Ziemann — University of Colorado
Sonia Kreidenweis — Colorado State University
Category
Secondary organic aerosol
Description
Viscosity of atmospheric aerosol spans fifteen orders of magnitude corresponding to thin liquids to solids. Because viscosity modulates the uptake of water and chemical species, proper assessment of phase state is required for modeling of atmospheric processes involving aerosol. Here we present a method that allows synthesis and isolation of particles that have undergone a single coagulation event. Moderately viscous semi-solid and liquid particles coalesce into a sphere while solid particle do not. Dynamic shape factors of the dimers are characterized by measurement of the mobility diameter. This technique was used to assess phase state as a function of relative humidity for pure organic and inorganic aerosol constituents. The data show that the solid to semi-solid phase transition typically occurred at a lower relative humidity than deliquescence relative humidity. Experimental results are compared with predictions from existing thermodynamic treatments of particle phase.
