Influence of Drying Rate on Morphology of Laboratory Generated Sodium Chloride Aerosols

NISHAN SAPKOTA, Rym Mehri, Timothy Sipkens, Steven Rogak, Joel Corbin, University of British Columbia

     Abstract Number: 570
     Working Group: Aerosol Physics

Abstract
Sodium chloride (NaCl) aerosols play an important role both in nature as sea-spray particles and in the laboratory as a calibration source. However, characterizing these aerosols is often difficult as they show significant variation in their shape, ranging from spherical to cubic depending on the drying rate. Drying rate influences particle morphology as it governs the nucleation rate of NaCl crystals; with extremely slow and fast rates resulting in monocrystalline cubes or polycrystalline spheroids, respectively. This work, therefore, builds on the current literature by establishing the influence of drying rate on the distribution of effective density and dynamic shape factor of laboratory generated NaCl particles. A TSI 3076 atomizer was operated to generate NaCl particles that are passed through a polytube Nafion dryer. Flow rates in the dryer were varied to control the drying rate according to a quantitative theoretical framework. The dried particles were then passed through a tandem Centrifugal Particle Mass Analyzer and differential mobility analyzer (tCPMA-DMA) setup to classify with respect to both mobility equivalent diameter and particle mass. Morphological information was validated with TEM images. The results showed that slow-dried particles attained a more cubical shape with a lower effective density while fast-dried particles retained their spherical morphology with a higher effective density.