Ice nucleation triggered by negative pressure

Claudia Marcolli

doi:10.1038/s41598-017-16787-3

Abstract

Homogeneous ice nucleation needs supercooling of more than 35 K to become effective. When pressure is applied to water, the melting and the freezing points both decrease. Conversely, melting and freezing temperatures increase under negative pressure, i.e. when water is stretched. This study presents an extrapolation of homogeneous ice nucleation temperatures from positive to negative pressures as a basis for further exploration of ice nucleation under negative pressure. It predicts that increasing negative pressure at temperatures below about 262 K eventually results in homogeneous ice nucleation while at warmer temperature homogeneous cavitation, i. e. bubble nucleation, dominates. Negative pressure occurs locally and briefly when water is stretched due to mechanical shock, sonic waves, or fragmentation. The occurrence of such transient negative pressure should suffice to trigger homogeneous ice nucleation at large supercooling in the absence of ice-nucleating surfaces. In addition, negative pressure can act together with ice-inducing surfaces to enhance their intrinsic ice nucleation efficiency. Dynamic ice nucleation can be used to improve properties and uniformity of frozen products by applying ultrasonic fields and might also be relevant for the freezing of large drops in rainclouds.

Highlights

Crystal nucleation has remained inaccessible to direct observation due to its stochastic nature which renders the exact time and location of occurrence unpredictable
The good agreement of this line with the measured freezing temperatures shows that the effect of pressure on freezing can be described by shifting the melting curve by a constant offset in pressure, analogous to the constant offset that relates melting and freezing temperatures as a function of water activity[4]
When the melting and freezing curves are extrapolated to negative pressure, higher melting and homogeneous freezing temperatures are predicted than under normal pressure

Summary

Claudia Marcolli

Homogeneous ice nucleation needs supercooling of more than 35 K to become effective. When pressure is applied to water, the melting and the freezing points both decrease. Melting and freezing temperatures increase under negative pressure, i.e. when water is stretched. This study presents an extrapolation of homogeneous ice nucleation temperatures from positive to negative pressures as a basis for further exploration of ice nucleation under negative pressure. Negative pressure occurs locally and briefly when water is stretched due to mechanical shock, sonic waves, or fragmentation The occurrence of such transient negative pressure should suffice to trigger homogeneous ice nucleation at large supercooling in the absence of ice-nucleating surfaces. When 2 mm[3] drops of pure distilled water are cooled, freezing usually occurs above 250 K due to heterogeneous nucleation on surfaces that facilitate the orientation of water molecules into an ice-like structure. We explore whether the occurrence of negative pressure may account for freezing when water is agitated

Results and Discussion

Conclusions and Outlook

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Additional Information