Freezing Supercooled Water Nanodroplets Near ~225 K Through Homogeneous and Heterogeneous Ice Nucleation PDF Download
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Author: Andrew J. Amaya
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 172
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Book Description
To complement the WAXS experiments, we determined the ice nucleation rates of these droplets using a combination of pressure trace measurements (PTM), Fourier Transform Infrared Spectroscopy (FTIR), and Small Angle X-ray Scattering (SAXS). We confirmed that the onset of droplet freezing is at ~225 K. Within in the temperature range of 217 K to 225 K, we find that the ice nucleation rate varies from ~1021 cm-3 s-1 to ~1022 cm-3 s-1. These results fill a gap along the ice nucleation vs temperature curve that had been unexplored and represent a sharp corner for ice nucleation rates of small droplets. This sharp transition in nucleation rates is difficult to replicate with theory. Finally, we explored the changes to freezing of supercooled water droplets, r ~7 nm, in the presence of a n-pentanol monolayer. The amount n-pentanol was varied from 3 to 6 mol% of the condensable and distinct differences were observed in the FTIR spectra when pure water droplets froze compared to when water/n-pentanol droplets froze. Quantifying these changes and relating them to the freezing mechanism is the subject of future work.
Author: Andrew J. Amaya
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 172
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Book Description
To complement the WAXS experiments, we determined the ice nucleation rates of these droplets using a combination of pressure trace measurements (PTM), Fourier Transform Infrared Spectroscopy (FTIR), and Small Angle X-ray Scattering (SAXS). We confirmed that the onset of droplet freezing is at ~225 K. Within in the temperature range of 217 K to 225 K, we find that the ice nucleation rate varies from ~1021 cm-3 s-1 to ~1022 cm-3 s-1. These results fill a gap along the ice nucleation vs temperature curve that had been unexplored and represent a sharp corner for ice nucleation rates of small droplets. This sharp transition in nucleation rates is difficult to replicate with theory. Finally, we explored the changes to freezing of supercooled water droplets, r ~7 nm, in the presence of a n-pentanol monolayer. The amount n-pentanol was varied from 3 to 6 mol% of the condensable and distinct differences were observed in the FTIR spectra when pure water droplets froze compared to when water/n-pentanol droplets froze. Quantifying these changes and relating them to the freezing mechanism is the subject of future work.
Author: Amy Gibbs
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Author:
Publisher: American Philosophical Society
ISBN: 9781422377123
Category :
Languages : en
Pages : 92
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Author: William J. Eadie
Publisher:
ISBN:
Category : Ice
Languages : en
Pages : 254
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Author: John Farrar
Publisher:
ISBN:
Category : Ice crystals
Languages : en
Pages : 68
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Author: Noah Ernest Dorsey
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 88
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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Book Description
Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, aw, which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humidity (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, Jhet, to be uniquely expressed by T and aw, a result we term the aw based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, Jhet, frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log10(Jhet) values for the various IN types derived exclusively by T and aw, provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Finally, we demonstrate that ABIFM can be used to derive frozen fractions of droplets and ice particle production for atmospheric models of cirrus and mixed phase cloud conditions.
Author: George K. Swinzow
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Under ordinary conditions, the freezing of water begins with supercooling and ice nucleation, and proceeds at 0 C at the ice/water interface until ice formation stops. The presence of solutes, high pressure, or dispersal in fine pores causes the water to freeze at temperatures below 0 C (the so-called freezing point depression). Whenever freezing begins, it proceeds at a constant temperature, or at a temperature which becomes progressively lower. A temperature rise during ice formation is considered here to be an anomaly. Under all equal circumstances, the conditions under which an anomalous freezing temperature is observable appear to be very special. This report describes two different experiments displaying the anomalous rise of temperature after nucleation and during ice formation. In one case the water was dispersed in the fine pores of fine powders; in the other case pure water was frozen in a transparent insulated cell. Photographic observations were made; relations of ice surface to water volume were measured. (Author).
Author: Yannick J. Rigg
Publisher:
ISBN:
Category : Environmental sciences
Languages : en
Pages :
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Author: Charles Alfred Knight
Publisher:
ISBN:
Category : Crystal growth
Languages : en
Pages : 176
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