AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Freezing of Supercooled n-decane Nanodroplets in a Supersonic Nozzle
VIRAJ MODAK, Barbara Wyslouzil, The Ohio State University
Abstract Number: 456 Working Group: Aerosol Physics
Abstract Crystallization is a common physical process that is encountered in industrial as well as natural settings. In case of systems with free surfaces, whether freezing is initiated in the bulk or on the surface is still a matter of much debate in the scientific community. Intermediate chain n-alkanes (16 < n < 50) are known to form an ordered monolayer up to 3 K above the equilibrium melting point (Tm). Our recent experiments have shown that even the short chain n-alkanes n-octane and n-nonane appear to freeze at the surface of supercooled (T ≈ Tm - 30) nanodroplets within the size range of 6-9 nm. In this work we extend this study to n-decane. Using multiple starting conditions, we try to identify the size and temperature limits under which surface freezing can be observed experimentally. In our experiments, a carrier gas-alkane vapor mixture cools rapidly in a supersonic nozzle, and beyond a critical supersaturation, the alkane vapor condenses forming supercooled nanodroplets. These droplets can freeze if the temperatures are cold enough. We use static pressure measurements to calculate the flow parameters. We characterize the droplets for size, number density and composition using Small Angle X-ray Scattering and Fourier Transformed Infrared (FTIR) Spectroscopy. Finally, we also estimate the surface and the bulk freezing rates for these droplets.