Ice Supercooled Water Research Articles

Rate of Homogenous Nucleation of Ice in Supercooled Water.

The homogeneous freezing of water is of fundamental importance to a number of fields, including that of cloud formation. However, there is considerable scatter in homogeneous nucleation rate coefficients reported in the literature. Using a cold stage droplet system designed to minimize uncertainties in temperature measurements, we examined the freezing of over 1500 pure water droplets with diameters between 4 and 24 μm. Under the assumption that nucleation occurs within the bulk of the droplet, nucleation rate coefficients fall within the spread of literature data and are in good agreement with a subset of more recent measurements. To quantify the relative importance of surface and volume nucleation in our experiments, where droplets are supported by a hydrophobic surface and surrounded by oil, comparison of droplets with different surface area to volume ratios was performed. From our experiments it is shown that in droplets larger than 6 μm diameter (between 234.6 and 236.5 K), nucleation in the interior is more important than nucleation at the surface. At smaller sizes we cannot rule out a significant contribution of surface nucleation, and in order to further constrain surface nucleation, experiments with smaller droplets are necessary. Nevertheless, in our experiments, it is dominantly volume nucleation controlling the observed nucleation rate.

Nucleation at the contact line observed on nanotextured surfaces.

It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at the liquid-gas interface. Using high speed imaging, we sought evidence for freezing at the contact line on catalyst substrates with imposed characteristic length scales (texture). Length scales consistent with the critical nucleus size and with δ∼τ/σ, where τ is a relevant line tension and σ is the surface tension, range from nanometers to micrometers. It is found that nanoscale texture causes a shift in the nucleation of ice in supercooled water to the three-phase contact line, while microscale texture does not.

Interface-Limited Growth of Heterogeneously Nucleated Ice in Supercooled Water

Heterogeneous ice growth exhibits a maximum in freezing rate arising from the competition between kinetics and the thermodynamic driving force between the solid and liquid states. Here, we use molecular dynamics simulations to elucidate the atomistic details of this competition, focusing on water properties in the interfacial region along the secondary prismatic direction. The crystal growth velocity is maximized when the efficiency of converting interfacial water molecules to ice, collectively known as the attachment kinetics, is greatest. We find water molecules that contact the intermediate ice layer in concave regions along the atomistically roughened surface are more likely to freeze directly. An increased roughening of the solid surface at large undercoolings consequently plays an important limiting role in the rate of ice growth, as water molecules are unable to integrate into increasingly deeper surface pockets. These results provide insight into the molecular mechanisms for self-assembly of solid phases that are important in many biological and atmospheric processes.

Morphological selection of Euclidean and fractal patterns of nonequilibrium growth of ice in supercooled water

A morphology diagram of Euclidean and fractal patterns of the nonequilibrium growth of ice in supercooled water has been constructed based on the experimental dependence of the growth rate of ice crystals of different shapes on the initial supercooling of water. An empirical morphological principle follows from this diagram: with an increase in water supercooling, the phase implementing the maximum volume growth rate of ice crystals is selected.

Externally Applied Electric Fields up to 1.6 × 105 V/m Do Not Affect the Homogeneous Nucleation of Ice in Supercooled Water

The freezing of water can initiate at electrically conducting electrodes kept at a high electric potential or at charged electrically insulating surfaces. The microscopic mechanisms of these phenomena are unknown, but they must involve interactions between water molecules and electric fields. This paper investigates the effect of uniform electric fields on the homogeneous nucleation of ice in supercooled water. Electric fields were applied across drops of water immersed in a perfluorinated liquid using a parallel-plate capacitor; the drops traveled in a microchannel and were supercooled until they froze due to the homogeneous nucleation of ice. The distribution of freezing temperatures of drops depended on the rate of nucleation of ice, and the sensitivity of measurements allowed detection of changes by a factor of 1.5 in the rate of nucleation. Sinusoidal alternation of the electric field at frequencies from 3 to 100 kHz prevented free ions present in water from screening the electric field in the bulk of drops. Uniform electric fields in water with amplitudes up to (1.6 ± 0.4) × 10(5) V/m neither enhanced nor suppressed the homogeneous nucleation of ice. Estimations based on thermodynamic models suggest that fields in the range of 10(7)-10(8) V/m might cause an observable increase in the rate of nucleation.

Effects of poly-vinyl alcohol on supercooling phenomena of water

The effects of a polymer additive on the supercooling of water were investigated experimentally. Poly-vinyl alcohols (PVAs) were used as the additives, and samples were prepared by dissolving the PVA in water. Since the characteristics of PVA are decided by its degrees of polymerization and saponification, these were varied along with the concentration as the experimental parameters. Moreover, the effect of purity of the water was also considered. Each sample was cooled and the temperature at the instant when ice appeared was measured. Since the freezing of supercooled water is a statistical phenomenon, many experiments were carried out and the average degree of supercooling was obtained. It was found that PVA affects the nucleation of ice in supercooled water and the degree of supercooling increases with the addition of PVA even for water with low purity. The average degree of supercooling increases with an increase in the degree of saponification of PVA.

Emergence of chaos during dendritic growth of ice

A transition from deterministic to chaotic growth behavior along the dendrite axis has been experimentally found and investigated. A “correlation structure” of a growing dendrite has been revealed in terms of relationship between oscillations of the dendrite tip velocity and the branching dynamics at different distances from the tip. It is shown that the dendritic growth of ice in supercooled water is an example of nonequilibrium morphogenesis of a dissipative system demonstrating deterministic chaos.

The nucleation of ice in supercooled D 2O and H 2O

The homogeneous nucleation rates of light and heavy water have been measured in supercooled levitated micro-droplets at different temperatures using a temperature jump experiment. Homogeneous nucleation times of ice in supercooled water follow the Poisson statistics. The nucleation rate has a negative temperature coefficient; it increases strongly with decreasing temperature. At the same degree of supercooling, the nucleation in heavy water is faster than in light water. The discussion of the experimental results is based on kinetic arguments in the frame of a two-state model of liquid water. The homogeneous nucleation rate J is tantamount to a volume-normalized apparent first-order rate constant J ⁎ which can be described by the product of the genuine rate constant j and an overall equilibrium constant K. K describes a large number of pre-equilibria, which are coupled to the rate-determining step of nucleation and influence the apparent nucleation rate J of formation of the critical germ.

Effect of surface kinetics on the dendritic growth of ice in supercooled water

The dendritic growth of ice in supercooled water was investigated experimentally. It has been found that, with an increase in the degree of initial supercooling of water, the data of measuring the growth rate of the dendrite tip v t, the average distance between the tip and the first side branch z SB, and the fractal dimension d f of the dendrite contour diverge from the analytically and numerically calculated parameters of dendritic growth. It is shown that the discrepancy between experiment and theory is due to the transition from the diffusional growth to the growth controlled by the surface kinetics. The nature of the anisotropic surface kinetics of ice growth in supercooled water is discussed.

Ultrasonic-induced nucleation of ice in water containing air bubbles

Cavitation induced by ultrasonic vibrations can cause nucleation of ice in supercooled water. In this study, the time required for ultrasonic-induced nucleation of ice was measured for water containing two different size distributions of air bubbles. When the water was supersaturated with air bubbles, there was a time lag of about 0.5 s between the onset of ultrasonic irradiation and the onset of ice nucleation, and the probability of ice nucleation was unusually high within 0.5–1.1 s after the onset of ultrasonic irradiation. These results cannot be explained by conventional models alone, in which the collapse of a cavitation bubble triggers the nucleation of ice. Secondary effects appear to also influence ice nucleation.

Surface crystallization of supercooled water in clouds.

The process by which liquid cloud droplets homogeneously crystallize into ice is still not well understood. The ice nucleation process based on the standard and classical theory of homogeneous freezing initiates within the interior volume of a cloud droplet. Current experimental data on homogeneous freezing rates of ice in droplets of supercooled water, both in air and emulsion oil samples, show considerable scatter. For example, at -33 degrees C, the reported volume-based freezing rates of ice in supercooled water vary by as many as 5 orders of magnitude, which is well outside the range of measurement uncertainties. Here, we show that the process of ice nucleus formation at the air (or oil)-liquid water interface may help to explain why experimental results on ice nucleation rates yield different results in different ambient phases. Our results also suggest that surface crystallization of ice in cloud droplets can explain why low amounts of supercooled water have been observed in the atmosphere near -40 degrees C.

Kinetics and morphology of nonequilibrium growth of ice in supercooled water

The kinetics of free growth of ice in a distilled-water film supercooled to −30°C was studied by the video recording technique in the polarized light. In the supercooling range 12 < ΔT < 16 K, a first-order kinetic morphological transition was observed between the structure formed by needlelike crystals of ice and the quasiadiabatic “structure” of single grains having the shape of planar platelets with the thickness proportional to the thickness of the water film and relative supercooling. It was found that this transition is accompanied by jumplike changes in the main crystallization parameters such as the growth rate of grains, their size and number, their kinetic behavior, and the fractal dimension of the structure.

Bubble dynamics and nucleation of ice in supercooled water

The effects of mechanically induced impulses such as vibration and flow have been used to induce the solid–liquid phase transformation in liquids held below their equilibrium freezing point. Although processes used for grain refining in metallurgy rely on this artificially enhanced nucleation process, there is no clearly identified underlying physical mechanism. Experiments have been conducted with single bubbles immersed in a small volume of supercooled water and trapped in a 22-kHz resonant cell to study the action of both large amplitude radial and shape oscillations. The experimental observations reveal that large-amplitude radial oscillations of micron-size air bubbles induce the nucleation of ice when a minimum supercooling of 5 °C is reached. Shape oscillations and radially nonresonant bubbles do not induce nucleation of ice within the same ‘‘incubation’’ time. The appearance of the ice crystal at the location of the trapped bubble strongly suggests a cause and effect correlation between the bubble radial oscillations and the freezing onset, and both sonoluminescing and nonluminescing bubbles appear to induce nucleation. This mechanism also has the additional benefit of allowing the direct measurement of free dendritic growth velocity within a supercooled liquid bulk in the absence of any artificially introduced seed. [Work sponsored by NASA.]

Inhibition of bacterial ice nucleators by fish antifreeze glycoproteins.

Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre.

Ice Nucleation by Miersite

Abstract Miersite, a naturally occurring solid solution of silver iodide and cuprous iodide, can nucleate ice in supercooled water at −1.42C. The excellent ice nucleation properties of miersite can be attributed to the fact that the miersite lattice is only 0.28% larger than the ice lattice.

Growth velocities of ice in supercooled water and aqueous sucrose solutions

Abstract Measurements have been made of the component velocities parallel to and normal to the basal plane of ice growing in supercooled water and aqueous sucrose solutions at supercoolings up to 10°C. It has been found that there are discontinuities in the velocity curves for the sucrose solutions. It is inferred that these are due to a growth mechanism change.

On the Growth of Ice in Aqueous Solutions Contained in Capillaries

The growth rate of ice in supercooled water and in dilute aqueous solutions of various salts which dissociate in water into univalent ions was studied. The solutions contained in polyethylene tubes of small bore had concentrations between 10-6 and 10-1 moles liter-1 and were investigated at bath supercoolings between 1° and 15°C. The growth rate of ice which in pure water was found to vary approximately with the square of the bath supercooling was affected in a systematic manner by the type and concentration of the salt in solution. At salt concentrations smaller than 5 × 10-2 moles liter-1 most salts did not affect the growth rate. However, the fluorides were found to increase the growth rate over and above the one in pure water. At concentrations larger than 5 × 10-2 moles liter-1 all the salts reduced the growth rate of ice below the one in pure water. By comparing solutions of salts with common anion it was found that at a particular bath supercooling and salt concentration the growth rate of ice was reduced most in lithium solutions and least in cesium and ammonium solutions. By comparing solutions of salts with common cation it was found that the growth rate of ice was reduced most in fluoride solutions and least in bromide solutions. It was concluded that in solutions with salt concentrations larger than 5 × 10-2 moles liter-1 the rate of dissipation of latent heat which controls the growth rate of ice is affected in a systematic manner by the freezing point lowering effects which result from pure mass transfer conditions prevailing at the ice-solution interface of a stagnant system. Some features of the observed growth rates are discussed in terms of the effect of dissolved salts on the growth forms of ice in aqueous solutions.

On the growth of ice crystals in supercooled water and aqueous solution drops

The results of a recent investigation on the free growth rate and the growth forms of ice in supercooled water and aqueous solutions are presented. The results are used to discuss the structure of frozen drops, the structure of hailstones, the mechanisms which are responsible for the glaciation of atmospheric clouds and the mechanisms which cause cloud electrification. It was found that the presence of dissolved salts and dust particles in cloud drops favor the formation of spongy and polycristalline ice, that it is unlikely for frozen cloud drops to develop into hexagonal shaped ice single-crystals, and that it is also unlikely that in atmospheric clouds freezing drops shatter and splinter. The latter result casts serious doubts on the splintering mechanism to contribute to thunderstorm electrification and to promote glaciation of clouds.

Ice nucleation under pressure and in salt solution

Organic compounds which promote the nucleation of ice in supercooled water nucleate ice more effectively when the water is compressed or when it contains large amounts of dissolved salt. It is proposed that this behaviour is caused by the special thermodynamic properties of the monolayer of water in contact with the organic surface. Under high pressure or in the presence of dissolved salt the monolayer crystallizes at a temperature above the equilibrium freezing point of the bulk liquid phase, and having crystallized, the monolayer provides a better substrate for the nucleation of bulk ice than does the original organic surface.