Thermodynamic and kinetic supercooling of liquid in a wedge pore

Nowak, D.; Heuberger, Manfred; Zäch, Michael; Christenson, Hugo K.

doi:10.1063/1.2996293

Cited by 24 publications

(50 citation statements)

References 40 publications

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“…We expect the first condensate formed to be a supercooled liquid, which will then freeze to form a solid condensate by normal nucleation. The Gibbs-Thomson effect predicts that a confined phase will suffer a decrease in the melting point inversely proportional to the dimension of the pore; as such, an infinitesimally small condensate is expected to be a liquid (25). This mechanism has been experimentally observed in a highly acute annular wedge (24)(25)(26).…”

Section: Discussionmentioning

confidence: 96%

Observing the formation of ice and organic crystals in active sites

Campbell

Meldrum

Christenson

2016

Proc. Natl. Acad. Sci. U.S.A.

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112

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Heterogeneous nucleation is vital to a wide range of areas as diverse as ice nucleation on atmospheric aerosols and the fabrication of high-performance thin films. There is excellent evidence that surface topography is a key factor in directing crystallization in real systems; however, the mechanisms by which nanoscale pits and pores promote nucleation remain unclear. Here, we use natural cleavage defects on Muscovite mica to investigate the activity of topographical features in the nucleation from vapor of ice and various organic crystals. Direct observation of crystallization within surface pockets using optical microscopy and also interferometry demonstrates that these sharply acute features provide extremely effective nucleation sites and allows us to determine the mechanism by which this occurs. A confined phase is first seen to form along the apex of the wedge and then grows out of the pocket opening to generate a bulk crystal after a threshold saturation has been achieved. Ice nucleation proceeds in a comparable manner, although our resolution is insufficient to directly observe a condensate before the growth of a bulk crystal. These results provide insight into the mechanism of crystal deposition from vapor on real surfaces, where this will ultimately enable us to use topography to control crystal deposition on surfaces. They are also particularly relevant to our understanding of processes such as cirrus cloud formation, where such topographical features are likely candidates for the "active sites" that make clay particles effective nucleants for ice in the atmosphere.nucleation | confinement | topography | pores | active sites T he growth of a new phase is almost always dependent on a nucleation event. Nucleation is therefore fundamental to a number of processes including crystallization, freezing, condensation, and bubble formation and is typically described in terms of classical nucleation theory. However, because this theory was developed to describe the nucleation of liquid droplets in vapor it cannot give a complete understanding of all nucleation processes, and in particular the formation of crystalline materials. Nucleation in the real world is also usually heterogeneous, occurring on seeds, impurities, or container surfaces. Although simple models consider nucleation to occur on perfectly flat, uniform surfaces, it is clear that real surfaces inevitably vary in chemistry and topography. We focus here on the effects of surface topography. Classical nucleation theory predicts a lower free energy barrier to nucleation in surface cracks or pores on the length scale of a critical nucleus (1). The extent of the reduction is contact-angle-dependent, such that nuclei with a low contact angle experience a more significant reduction from topography.Topography is known to promote crystallization directly from a vapor (2-5), because these systems typically exhibit low contact angles. Crystallization from the melt, in contrast, is associated with very high contact angles such that topography is usually ineff...

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Section: Discussionmentioning

confidence: 96%

Observing the formation of ice and organic crystals in active sites

Campbell

Meldrum

Christenson

2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

112

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“…Grain boundaries show up, and in absence of impurities, typical microscale morphologies develop (Libbrecht, 2005;Sazaki et al, 2010;Asakawa et al, 2014;Kiselev et al, 2017) and rearrange (Krzyzak et al, 2007). Even supercooled water could exist (in highly curved nanoscale structures) (Nowak et al, 2008). In nature, impurities can concentrate in such defects (Baker et al, 2003;Bartels-Rausch et al, 2012, for example forming networks of water-filled microscale "veins", sometimes of relevance as a habitat for organisms (Mader, 1992;Mader et al, 2006;Buford Price, 2000).…”

Section: Introductionmentioning

confidence: 99%

The ice–vapour interface during growth and sublimation

2021

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Abstract. We employed environmental scanning electron microscopy (ESEM) in low-humidity atmosphere to study the ice growth, coalescence of crystallites, polycrystalline film morphology, and sublimation, in the temperature range of −10 to −20 ∘C. First, individual ice crystals grow in the shape of micron-sized hexagonal columns with stable basal faces. Their coalescence during further growth results in substantial surface defects and forms thick polycrystalline films, consisting of large grains separated by grain boundaries. The latter are composed of 1 to 3 µm wide pores, which are attributed to the coalescence of defective crystallite surfaces. Sublimation of isolated crystals and of films is defect-driven, and grain boundaries play a decisive role. A scallop-like concave structure forms, limited by sharp ridges, which are terminated by nanoscale asperities. The motivation for this work is also to evaluate ESEM's ability to provide a clean and reproducible environment for future study of nucleation and growth on atmospherically relevant nucleators such as materials of biological origin and inorganic materials. Hence, extensive information regarding potential ESEM beam damage and effect of impurities are discussed.

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“…A reduction in temperature below Tm thus has the same effect as a reduction in vapour pressure below saturation above Tm. This has been found to accurately predict the size (proportional to the radius of curvature of the vapour-water interface) of condensates of cyclohexane [134] and neo-pentanol [108; 109] below Tm. With water, however, the condensate size and interfacial radius of curvature were larger than predicted, but good agreement was obtained by assuming that each water condensate contained all the K + (in the form of K2CO3) from the mica surface with which it was in contact.…”

Section: Mica and The Surface Force Apparatusmentioning

confidence: 99%

The nature of the air-cleaved mica surface

Christenson

Thomson

2016

Surface Science Reports

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111

102

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The accepted image of muscovite mica is that of an inert and atomically smooth surface, easily prepared by cleavage in an ambient atmosphere. Consequently, mica is extensively used a model substrate in many fundamental studies of surface phenomena and as a substrate for AFM imaging of biomolecules. In this review we present evidence from the literature that the above picture is not quite correct. The mica used in experimental work is almost invariably cleaved in laboratory air, where a reaction between the mica surface, atmospheric CO2 and water occurs immediately after cleavage. The evidence suggests very strongly that as a result the mica surface becomes covered by up to one formula unit of K2CO3 per nm 2 , which is mobile under humid conditions, and crystallizes under drier conditions. The properties of mica in air or water vapour cannot be fully understood without reference to the surface K2CO3, and many studies of the structure of adsorbed water on mica surfaces may need to be revisited. With this new insight, however, the air-cleaved mica should provide exciting opportunities to study phenomena such as two-dimensional ion diffusion, electrolyte effects on surface conductivity, and two-dimensional crystal nucleation.

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Thermodynamic and kinetic supercooling of liquid in a wedge pore

Cited by 24 publications

References 40 publications

Observing the formation of ice and organic crystals in active sites

Observing the formation of ice and organic crystals in active sites

The ice–vapour interface during growth and sublimation

The nature of the air-cleaved mica surface

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