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

Abstract View


Characterizing the Homogeneous Nucleation of Carbon Dioxide in a Supersonic Laval Nozzle

KAYANE DINGILIAN, Yensil Park, Barbara Wyslouzil, The Ohio State University

     Abstract Number: 98
     Working Group: Aerosol Physics

Abstract
Understanding and characterizing the nucleation of carbon dioxide (CO2) has significant implications on technologies used to assessing and countering climate change. CO2 nucleation is also relevant on planets and other extra-terrestrial bodies where CO2 dominates the atmospheric and cloud compositions. We studied the homogeneous nucleation of carbon dioxide in the carrier gas argon for varying concentrations of CO2 up to approximately 40 mole percent in a supersonic nozzle. Using position resolved pressure trace measurements (PTM), we determined the pressure, temperature, and characteristic time corresponding to the phase transition. In our nozzle, we reached temperatures as low as 62K and pressures as low as 1200 Pa. We found the onset of nucleation of carbon dioxide took place between 83 and 93K with partial pressures of CO2 ranging from 84 to 784 Pa. The position of onset initially moved upstream then shifted back downstream with increasing mole fraction of CO2. This behavior indicated competition between the saturation of CO2 with increased material and the thermodynamic properties of the CO2-argon mixture. The characteristic nucleation time ranged from 10 to 26 microseconds and mirrored the trend seen in the position of onset. Small angle x-ray scattering (SAXS) measurements will be used to determine the aerosol number density and thus the experimental nucleation rate. The onset data collected in these experiments were located in the solid region of CO2’s phase diagram but we will use SAXS together with Fourier transform infrared spectroscopy (FTIR) measurements to try to discover which phase of CO2 condenses first. Experimental results will be compared to classical nucleation theory and other models to help mend the gaps between predictive methods and reality.