Article

Air Bubbles in Ice

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Abstract

The opacity of ice formed from water containing dissolved air is due to the presence of bubbles of air in the ice. Both bubble concentration and sizes were found to depend on the rate of freezing. Bulk water saturated with air at 0°C was found to freeze into ice containing about six bubbles per mm³ when freezing proceeded at 0.5 mm min⁻¹ and 300 per mm³ at a rate of 5 mm min⁻¹. Bubbles were formed at the ice-water boundary when the concentration of dissolved air reached a critical value which, for rates of freezing greater than 2 mm min⁻¹, corresponded to a supersaturation ratio of 30. Agitation of the water could prevent the critical concentration from being attained and clear ice then formed. Other factors which influenced bubble concentrations and sizes were the amount of dissolved air, pressure, thickness of the layer of water ahead of the growing ice and escape of bubbles by buoyancy. The magnitude and extent of the air concentration gradient ahead of the ice were estimated from theory. Bubbles in ice were found to change shape with time particularly when under the influence of a temperature gradient.

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... Major conceptual frameworks were provided by Halde (1980) and Vesilind and Martel (1990), who reported that a slow freezing rate rejects particle by the moving ice-water interface, whereas a high freezing rate traps particle into the developing ice layer. Carte (1961) showed that air bubbles in ice could form from air originally dissolved in water before freezing. ...
... Due to the compressibility and temperature-dependent volume change of gases, the gas volume can also change during the freezing process. Furthermore, Carte (1961) observed the nucleation and entrapment of gas bubbles by an advancing ice-water interface, since gas solubility in ice is at least two orders of magnitude smaller than in water (Killawee et al. 1998). Therefore, bubbles may form due to nucleation at the water-ice boundary when the water at the interface becomes supersaturated. ...
... Therefore, bubbles may form due to nucleation at the water-ice boundary when the water at the interface becomes supersaturated. Bubble concentration and sizes were found to be depending on the rate of freezing (Carte 1961). ...
Article
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The quantification of greenhouse gas emissions from aquatic ecosystems requires knowledge about the spatial and temporal dynamics of free gas in sediments. Freezing the sediment in situ offers a promising method for obtaining gas-bearing sediment samples, unaffected by changes in hydrostatic pressure and sample temperature during core withdrawal and subsequent analysis. This article presents a novel freeze coring technique to preserve the in situ stratigraphy and gas bubble characteristics. Nondestructive X-ray computed tomography (CT) scans were used to identify and characterize coring disturbances of gravity and freeze cores associated with gassy sediment , as well as the effect of the freezing process on the gas bubble characteristics. Real-time X-ray CT scans were conducted to visualize the progression of the freezing process. Additional experiments were conducted to determine the freezing rate to assess the probability of sediment particle/bubble migration, and gas bubble nucleation at the phase transition of pore water to ice. The performance of the freeze coring technique was evaluated under field conditions in Olsberg and Urft Reservoir (Germany). The results demonstrate the capability of the freeze coring technique for the preservation of gas-bearing sediments and the analysis of gas bubble distribution pattern in both reservoirs. Nevertheless, the obtained cores showed that nearly all gravity and freeze cores show some degree of coring disturbances.
... As water freezes to ice, dissolved gases too large to fit into the lattice of ice are rejected, then redistributed at the ice-water interface, where the gas content in the water is at its maximum (Bari and Hallett, 1974;Inada and others, 2009). As freezing progresses, the interface concentration of dissolved gases surpasses a critical value, the water at the interface becomes supersaturated, and gas bubbles nucleate and grow to a visible size (Bari and Hallett, 1974;Carte, 1961;Maeno, 1967;Yoshimura and others, 2008) along the interface. Bubbles formed in this way can be found in pond/lake ice, as well as in hailstones (Bari and Hallett, 1974). ...
... The bubbles nucleated at the advancing ice-water interface can be characterized by concentration, size and shape. The concentration and size of the bubbles in ice depend on growth rate of ice, the amount of gases dissolved in water and the particulate content of the water (Carte, 1961;Bari and Hallett, 1974). The rate of ice growth affects the size, shape and distribution of bubbles and therefore the porosity of the ice (Carte, 1961;Bari and Hallett, 1974;Zhekamukhov, 1976). ...
... The concentration and size of the bubbles in ice depend on growth rate of ice, the amount of gases dissolved in water and the particulate content of the water (Carte, 1961;Bari and Hallett, 1974). The rate of ice growth affects the size, shape and distribution of bubbles and therefore the porosity of the ice (Carte, 1961;Bari and Hallett, 1974;Zhekamukhov, 1976). This was further supported by the results from the field study by Gow and Langston (1977). ...
Article
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Autonomous temperature data loggers were used to measure the temperature profile within a growing ice cover and in the water below. The ice formed under natural conditions over the pond. We observed the presence of distinct layers of gas bubbles throughout the ice thickness. Temperature measurements allowed us to determine growth rates (μm s ⁻¹ ) and cooling rates (°C s ⁻¹ ) of the ice and demonstrated that these bubble layers formed during the peak ice growth rates from 0.58 to 0.92 µm s ⁻¹ . The growth rates, leading to the formation of layers of bubbles, were more than an order of magnitude lower than for bubbles produced in controlled laboratory conditions (from 3 to 80 µm s ⁻¹ ). This observation introduces the possibility that solid impurities play a role in natural waters and that they must lower the limit of growth rates required for bubble occurrence. Data revealed a decrease in ice growth rates while cooling rates increased. We interpret this observation as an effect of the heat flux from the water to the ice (8.34–34.11 W m ⁻² ), and of gas concentration changes in the water below. Calculations of the ice thickness using traditional methods showed the necessity to include the heat flux from the water to the ice and the effect of gas bubbles within the ice and near the ice–water interface.
... If the rate of advance of the front is slower than a threshold value, and especially when the front is moving vertically, the gas bubbles would form pipes. He quoted apparent support from observations of water-air and metal-gas solutions (Carte, 1961;Fast, 1965), and argued that pipe vesicles in basalt form by the slow directional solidification of lava near the flow base. Philpotts and Lewis (1987) Philpotts and Lewis (1987) questioned the "self-evident-looking assumption" that bubble buoyancy is responsible for pipe vesicles. ...
... However, because the horizontal pipes in such a radial configuration were evidently not formed by buoyant gas bubbles, Philpotts and Lewis (1987) argued that bubble buoyancy (as in the Walker, 1987 model) is not the cause of any pipe vesicles, for which some other mechanism must be sought. Philpotts and Lewis (1987) noted the formation of air-filled tubes within ice cubes due to exsolution of air originally dissolved in the water during its freezing (see also Carte, 1961). As the water-ice boundary moves inwards, continuing exsolution of air leaves the long tubes which have striking similarities to pipe vesicles in basalt, namely their mutual parallelism, constant diameters, regular spacing, and even occasional mergence. ...
... From Fig. 4, it is seen that Ice 1 has the lowest density, followed by Ice 2 and then Ice 3. The opacity of the ice is also a measure of the density of the ice, as a higher fraction of air bubbles in the ice results in a more opaque ice. 53 From Fig. 1a, it is clear that Ice 1 has a much higher degree of air bubbles present than the other types of ice, and that Ice 3 in Fig. 1c is almost completely free of air bubbles. The different transparencies of the ices substantiates the different densities of the ice types as seen in Fig. 4. ...
... 54 The exact definition of glaze ice varies, 25,42,54 but it can be assumed that Ice 3 displays a structure similar to that of theoretical glaze ice due to the high transparency and the lack of air bubbles. 53 Micro-structures of the ice types might be proposed based on the densities, and such proposed structures can be found in the supplementary material. ...
Article
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To lower the ice adhesion strength is the most efficient technique for passive ice removal for several applications. In this paper, the effect of different types of ice on the ice adhesion strength was investigated. The ice types precipitation ice, in-cloud ice and bulk water ice on the same aluminum substrate and under similar environmental conditions were investigated. The ice adhesion strength was measured with a centrifugal adhesion test and varied from 0.78 ± 0.10 MPa for precipitation ice, 0.53 ± 0.12 MPa for in-cloud ice to 0.28 ± 0.08 MPa for bulk water ice. The results indicate that the ice adhesion strength inversely correlates with the density of ice. The results inspire a new strategy in icephobic surface development, specifically tailored to the relevant ice type.
... In most instances, icing is undesired 22 and causes numerous problems, such as reduction of crop production in agriculture [1], reduction 23 of lifting force with decreased flight safety in aviation [2], and heat transfer deterioration in 24 heat exchanger systems [3]. Understanding the icing mechanisms and employing appropriate 25 anti-icing technologies have been intensively studied in a few decades. Some progress have been 26 made regarding the ice nucleation physics under humidity or gas flow environments [4,5], the 27 freezing front growth and droplet shape evolution features [6][7][8], and the pointy tip formation 28 mechanism at the later stage of icing [9,10]. ...
... 34 In all of these studies, frozen ice has been considered as a tight solid, which may not be always 35 true. It has been observed from ice disks [25], natural pond ice [26], and ice cubes frozen in 36 fridges [27], that some bubbles may be formed. For sessile droplets, there was also some incidental 37 observation that bubbles might form in ice beads [9,28]; for example, one can see the bubbles in 38 two-dimensional (2D) freezing droplets captured by Marin et al. (although they do not mention 39 the bubble formation in their Letter) [9]. ...
Article
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Water droplet icing on solid surfaces has been intensively studied in recent years but still with many mechanisms unrevealed. Here, we report a bubble formation phenomenon that always occurs in freezing droplets, from millimeter-sized sessile droplets to microscale condensed droplets, during icing and condensation frosting. In the second stage of icing (the first stage is nucleation and recalescence), air dissolved in liquid water is separated out in the ice front, forming many isolated bubbles. Coupled with the droplet icing physics, a theoretical model was proposed to predict the bubble formation and elucidate its influencing factors. Due to the bubble formation, the final ice droplet is actually a porous medium, rather than a complete solid ice. These results bring new insight into icing physics, helping modify icing models and improve anti-icing and deicing techniques.
... This results in the continuous formation of freeze-out bubble layers which preserve, to a certain degree, information about the concentration of the dissolved gases in the water column during the time of freezing (Lipp et al., 1987;Craig et al., 1992;Killawee et al., 1998). The frequency of bubble layer formation, bubble size, and bubble shape are largely dependent on the rate of freezing (Carte, 1961;Yoshimura et al., 2008). The sizes of freezeout bubbles are reported to range between micrometers to millimeters at natural freezing rates of the order of millimeters per day (Lipp et al., 1987;Yoshimura et al., 2008). ...
... The model results can therefore be considered to be conservative when calculating net CH 4 production rates. Since the size of bubbles from freezedegassing depends largely on the rate of freezing (Carte, 1961), we assumed that the accumulation of freeze-out bub-bles was adequately represented by a constant rate during periods of constant freezing (Yoshimura et al., 2008). The partial pressure of CH 4 in the bubbles was assumed to be always in equilibrium with the partial pressure of CH 4 in the water column, following Henry's law. ...
Article
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Lakes and ponds play a key role in the carbon cycle of permafrost ecosystems, where they are considered to be hotspots of carbon dioxide CO2 and methane CH4 emission. The strength of these emissions is, however, controlled by a variety of physical and biogeochemical processes whose responses to a warming climate are complex and only poorly understood. Small waterbodies have been attracting an increasing amount of attention since recent studies demonstrated that ponds can make a significant contribution to the CO2 and CH4emissions of tundra ecosystems. Waterbodies also have a marked effect on the thermal state of the surrounding permafrost; during the freezing period they prolong the period of time during which thawed soil material is available for microbial decomposition. This study presents net CH4 production rates during the freezing period from ponds within a typical lowland tundra landscape in northern Siberia. Rate estimations were based on CH4 concentrations measured in surface lake ice from a variety of waterbody types. Vertical profiles along ice blocks showed an exponential increase in CH4 concentration with depth. These CH4 profiles were reproduced by a 1-D mass balance model and the net CH4 production rates were then inferred through inverse modeling. Results revealed marked differences in early winter net CH4 production among various ponds. Ponds situated within intact polygonal ground structures yielded low net production rates, of the order of 10-11 to 10-10 mol m-2 s-1 (0.01 to 0.14 mgCH4 m-2 day-1). In contrast, ponds exhibiting clear signs of erosion yielded net CH4 production rates of the order of 10-7 mol m-2 s-1 (140 mg CH4 m-2 day-1). Our results therefore indicate that once a particular threshold in thermal erosion has been crossed, ponds can develop into major CH4 sources. This implies that any future warming of the climate may result in nonlinear CH4 emission behavior in tundra ecosystems.
... Nucleation of a bubble on a solidification front, its entrapment as a pore and shape development in solid are primarily determined by supersaturation ratio, representing the ratio between solute concentration and saturation solute concentration. Carte [22] observed that bubbles were formed at the ice-water interface, when concentration of dissolved air reached a critical value which, for solidification rates greater than 2 mm/min, corresponded to a supersaturation ratio of 30. Murakami and Nakajima [19] observed pore formation of water-carbon dioxide solutions. ...
... Bubble nucleation on a solidification front is affected by solidification rate. Carte [25] observed that bubble were formed at the ice-water interface, when concentration of dissolved air reached a critical value which, for solidification rates greater than 2 mm/min, corresponded to a supersaturation ratio of 30. Park et al. [18] and Drenchev [19], respectively, showed that an increase in solidification rate increases pore nucleation rates due to an increased difference between pressures in the pore and the ambient, and supersaturation ratio in the melt. ...
... Carte [1] studied the motion of air bubbles when ice is created. Seipel and Nivfors [19] proposed the real time formation of an opaque area using textures, while expressing reflection and refraction effects. ...
Article
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We propose a real time simulation for window frost formation on mobile devices that uses both particles and grids. Previous ice formation methods made heavy demands on both memory and computational capacity because they were designed for a desktop environment. In this paper, a frost skeleton grows around a location touched by the user using particles, and the ice surfaces are constructed using a grid. Using a nonlattice random-walk technique, the frost skeleton grows freely and naturally. A hash grid technique is used to search efficiently for neighbor particles during the crystallization process. Finally, some 2.5D details are added to the ice skeleton by adjusting the height of the grid vertices around the skeleton. Experiments show that our method creates realistic frost in real time. Our method can be used to express ice formation effects in touch-based mobile device applications such as weather forecasts or games.
... Water occasionally drips from the ceiling and freezes in the lakes that contain cm-sized air bubbles. Large air bubbles in clear ice are expected for slow freezing from above (Carte, 1961;Bari & Hallett, 1974). Table 1 lists the samples. ...
Article
Mauna Loa volcano, on the Island of Hawaii, has numerous young lava tube caves. Among them, two at high altitude are known to contain ice year-round: Mauna Loa Icecave and Arsia Cave. These unusual caves harbor cold, humid, dark, and biologically restricted environments. Secondary minerals and ice were sampled from both caves to explore their geochemical and microbiological characteristics. The minerals sampled from the deep parts of the caves, where near freezing temperatures prevail, are all multi-phase and consist mainly of secondary amorphous silica SiO2, cryptocrystalline calcite CaCO3, and gypsum CaSO4·2H2O. Based on carbon and oxygen stable isotope ratios, all sampled calcite is cryogenic. The isotopic composition of Arsia Cave pond water falls on the global meteoric line, indicating that little evaporation has occurred. The microbial diversity of a silica and calcite deposit in Mauna Loa Icecave and from ice pond water in Arsia Cave was explored by analysis of ∼50,000 SSU rRNA gene fragments via amplicon sequencing. Analyses reveal that the Hawaii ice caves harbor unique microbial diversity distinct from other environments, including cave environments, on Hawaii and worldwide. Actinobacteria and Proteobacteria were the most abundant microbial phyla detected, which is largely consistent with studies of other oligotrophic cave environments. The cold, isolated, oligotrophic basaltic lava cave environment on Hawaii provides a unique opportunity to understand microbial biogeography not only on Earth, but also on other planets.
... Supersaturation can be achieved in three ways: First, decreasing the solubility of the gas in the liquid by decompressing the solution which has been saturated at a higher pressure or increasing (typically) the temperature of the saturated solution [31]. Second, supersaturated solutions can be prepared by reducing the amount of liquid (solvent) in the saturated solution while keeping the amount of dissolved gas constant (see for example the formation air bubbles in ice [38,118,173] or crystals [207]). Third, gas can be generated chemically or electrochemically in a solution [31,147]. ...
Thesis
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Mixing water with anhydrous cement powder and other additives results in a viscid cement slurry and triggers a set of complex exothermic reactions. As the cement slurry transitions from a suspension to a gel and ultimately to a stone-like porous solid, the material develops mechanical properties. This transition, however, is also accompanied by bulk volume changes, which -if restrained- lead to premature cracking of materials and structures. The main objective of this study is to relate bulk volume changes as measured at a macroscopic scale to their finer colloidal origin under controlled temperature and pressure conditions. To achieve this goal, an original set of macroscopic scale experiments is designed and a multiscale microporomechanics model is employed to rationalize the experimental results. While bulk volume changes have been classically attributed to capillary pressure, surface tension, and disjoining pressure that all relate to changes in relative humidity, we herein argue that they are a consequence of eigenstresses that develop in the solid phase of the hydrating matter due to attractive and repulsive colloidal forces at mesoscale. To prove our hypothesis, we experimentally investigate volume changes under saturated and drained conditions that eliminate any volume changes associated with humidity and (effective) pressure changes. Under these conditions, we observe first a volume expansion followed at later stages of hydration by volume shrinkage that cannot be explained by classical theories. By analyzing both expansion and shrinkage within the framework of incremental micro-poro-mechanics, we suggest that the expansion is caused by the relative volume change between the reactive solids and hydration products in the hydration reaction. After the solid percolates, this volume change is restrained by the percolated solid phase. This induces a compressive eigenstress in the solid phase that entails a swelling of the material under overall stress-free conditions. In return, as the material further densifies, the attractive forces between charged C-S-H grains prevail causing the whole system to shrink. These attractive (tensile) forces compete with the compressive solid eigenstress development, reversing the expansion into shrinkage. By carrying out tests at different temperatures, we provide strong experimental evidence that this tensile eigenstress development is an out-of-equilibrium phenomenon that occurs close to jamming. Furthermore, the tensile eigenstresses calculated from our shrinkage measurements agree qualitatively with those from meso-scale coarsegrained simulations of C-S-H precipitation originating from the electrostatic coupling between charged C-S-H particles mediated by the electrolyte pore solution.
... A plausible cause for the enhanced amount of retrapped air in the ice core ice compared to the bubble-free ice (0.31% versus 0.14%) is the physical characteristics of the ice core. 38 The pressurized gas bubbles in the ice core perturb the melting ice by bubbling during melting and facilitate gas dissolution in water. Our results indicate that the bubble-free ice experiments with high-purity ice should not be considered because they have the same condition as the actual ice core experiments, as assumed in previous studies. ...
Article
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Atmospheric nitrous oxide (N2O) is a greenhouse gas and ozone-depleting substance whose emissions are substantially perturbed by current human activities. Although air trapped in polar ice cores can provide direct information about N2O evolution, analytical precision was not previously sufficient for high temporal resolution studies. In this work, we present a highly improved analytical technique with which to study N2O concentrations in ancient-air-trapped ice cores. We adopt a melt–refreezing method to extract air and use a gas chromatography–electron capture detector (GC–ECD) to determine N2O concentrations. The GC conditions are optimized to improve the sensitivity for detecting N2O. Retrapped N2O in ice during the extraction procedure is precisely analyzed and corrected. We confirmed our results using data from the Styx Glacier ice core in Antarctica by comparing them with the results of a dry-extraction method. The precision estimated from the pooled standard deviation of replicated measurements of the Styx ice core was 1.5 ppb for ∼20 g of ice, a smaller sample of ice than was used in previous studies, showing a significant improvement in precision. Our preliminary results from the Styx Glacier ice core samples have the potential to define small N2O variations (a few parts per billion) at centennial time scales.
... In-situ observation provides useful information about the bubble formation and morphology during solidification. Several methods are available to observe porosity during solidification, such as optical methods [8,9] and micro focus X-ray imaging [10][11][12]. Generally, in-situ experiments suffer from limitations regarding tracking the bubble motion, transparency of alloys, and the thickness of sample [13]. ...
Article
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This paper presents a comparative study between the pseudopotential Shan-Chen model and the phase field multiphase lattice Boltzmann method for simulating bubble dynamics during dendritic solidification of binary alloys. The Shan-Chen method is an efficient lattice Boltzmann multiphase method despite having some limitations, including the generation of large spurious currents. The phase field model solves the Cahn-Hilliard equation in addition to the Navier-Stokes equation to track the interface between phases. The phase field method is more accurate than the Shan-Chen model for simulation of fluids with a high-density ratio since it generates an acceptable small spurious current, though at the expense of higher computational costs. For the simulations in this article, the multiphase lattice Boltzmann model was coupled with the cellular automata and finite difference methods to solve temperature and concentration fields. The simulated results were presented and compared regarding the ability of each model to simulate phenomena at a microscale resolution, such as Marangoni convection, the magnitude of spurious current, and the computational costs. It is shown that although Shan-Chen methods can replicate some qualitative features of bubble-dendrite interaction, the generated spurious current is unacceptably large, particularly for practical values of the density ratio between fluid and gas phases. This occurs even after implementation of several enhancements to the original Shan-Chen method. This serious limitation makes the Shan-Chen models unsuitable to simulate fluid flow phenomena, such as Marangoni convection, because the large spurious currents mask completely the physical flow.
... This hypothesis is supported by the similar diameters of the tubes. Carte (1961) reported nucleation of bubbles at the ice front during freezing of dissolved gas containing water. When freezing in rising direction of bubbles at slow freezing rate, cylindrical threads were formed parallel to the freezing direction. ...
Article
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All-cellulose porous solids have been prepared by foaming watery suspensions of microfibrillated cellulose (MFC) and the foaming agent methyl cellulose (MC) followed by freeze-drying. Mechanical and structural characterization of foamed and unfoamed porous solids with and without MC was performed to evaluate the effect of the foaming agent and of the foaming process. In unfoamed systems, partial replacement of MFC by MC led to decreased mechanical stability and a stronger dependency of mechanical properties on density. The foaming process allowed to reach gas volume fractions of up to 52% through interfacial stabilization by MC and thus reduce specific volume of water before drying by half. The incorporated gas bubbles withstood the freezing and drying process as shown by scanning electron microscopy of freeze-dried samples. Final density and porosity were tailored by adjusting solid content in the suspension, foaming time or concentration of foaming agent. In uniaxial compression, foamed porous solids showed similar or even higher Young’s modulus and yield stress compared to unfoamed systems at same composition and density. In foamed porous solids with increased mechanical stability, X-ray μ-computed tomography revealed the occurrence of aligned tubes, which act as reinforcing substructure. Thus, foaming can be applied prior to freeze-drying to drastically reduce water content, while the mechanical performance is unaffected or even improved through restructuring. Online access to full article: http://em.rdcu.be/wf/click?upn=lMZy1lernSJ7apc5DgYM8e4XBGpbcROjtgjU88eNwqg-3D_LOeYrYi-2FbjVRuMdi63-2FVQaf7me-2Fe8j-2FW8zz3fC30EJIISNpNOzU79LWiMtbtD1ZVQsxQpNpCRji5b7zArrKDClEmQkrUfSFQumkrun7KUvbmcfvb6mcLOHpMlKT9eXDsw-2FSPt26YPdzMe3Unl-2By3vCGwEmdI8IgTGgBe-2BA9bmatjWdWhBdkd-2BYxP3eqvzv2TihSULKEQqZEGYCq4-2F3dc5jmNIcwtc8s5aXELzcoA4cB4jbSw76uLn83J0VQUmnOashzG4pmYKzP-2FzLWGI-2BkXoQ-3D-3D
... conclusion was drawn in one of the first attempts to quantify the amount of air in ice, with the success 707 not exceeding 50 -66 %; there remained 33 -50 % of air deemed to form bubbles too small to be 708 discernible with the magnification of 160 times (Carte, 1961). 709 ...
Article
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The microstructure of polycrystalline ice with a threading solution of brine controls its numerous characteristics, including the ice mechanical properties, ice-atmosphere interactions, sea-ice albedo, and (photo)chemical behavior in/on the ice. Ice samples were previously prepared in laboratories to study various facets of ice-impurities interactions and (photo)reactions to model natural ice-impurities behavior. We examine the impact of the freezing conditions and solute (CsCl used as a proxy for naturally occurring salts) concentrations on the microscopic structure of ice samples via an environmental scanning electron microscope. The method allows us to observe in detail the ice surfaces, namely, the free ice, brine puddles, brine-containing grain boundary grooves, individual ice crystals, and imprints left by entrapped air bubbles at temperatures higher than −25 °C. The amount of brine on the external surface is found proportional to the solute concentration and is strongly dependent on the sample preparation method. Time-lapse images in the condition of slight sublimation reveal sub-surface association of air bubbles with brine. With rising temperature (up to −14 °C), the brine surface coverage increases to remain enhanced during the subsequent cooling and until the final crystallization below the eutectic temperature. The ice recrystallization dynamics identifies the role of surface spikes in retarding the ice boundaries propagation (Zeener pining). The findings thus quantify the amounts of brine exposed to incoming radiation, available for the gas exchange, and influencing other mechanical and optical properties of ice. The results have straightforward implications for artificially prepared and naturally occurring salty ices.
... The differences in the bubble and impurity stratigraphy might indicate changes in the main ice-forming processes. Bubble nucleation in freezing water at equilibrium with the atmosphere has been inves- tigated by Carte (1961) and later by Hubbard (1991). Following these authors air components initially dissolved in the liquid water are rejected from the developing ice front until the air concentration in the water layer reaches (super-)saturation leading to bubble formation. ...
Article
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Investigations into the genesis and dynamical properties of cave ice are essential for assessing the climate significance of these underground glaciers. We drilled an ice core through a 7.1 m thick ice body filling a large cavern of the dynamic ice cave Eisenriesenwelt (Austria). In addition to visual core inspections, quasi-continuous measurements at 2 cm resolution comprised particulate matter, stable water isotope (δ<sup>18</sup>O, δ D ) and electrolytic conductivity profiles supplemented by specifically selected samples analysed for tritium and radiocarbon. We found that recent ablation led to an almost complete loss of bomb derived tritium removing any ice accumulated, since at least, the early fifties leaving the actual ice surface even below the natural tritium level. The small particulate organic masses made radiocarbon dating inconclusive, though a crude estimate gave a maximum ice age in the order of several thousand years. The visual stratigraphy and all investigated parameters showed a clear dichotomy between the upper 4 m and the bottom 3 m of the core, which points to a substantial change in the ice formation process. Main features of the core comprise the changing appearance and composition of distinct cyro-calcite layers, a extremely low total ion content and a surprisingly high variability of the isotope signature. Co-isotope evaluation (δ D versus δ<sup>18</sup>O) of the core in comparison with data from precipitation and karst spring water clearly indicate that ice formation is governed by (slow) freezing of dripping water.
... The solubility of air in ice is much smaller than in liquid water and therefore, generally air bubbles are generated during freezing of a water droplet [29]. Although the water used for the present experiments is degassed prior to droplet generation, freezing of the water droplets results in the formation of small air bubbles inside the frozen drop. ...
Article
In the present study, ice nucleation in sessile water drops during continuous cool down is studied experimentally under the impact of a constant electric field, to determine its influence on heterogeneous nucleation. The experimental setup enables simultaneous observation of multiple drops under well-defined conditions with and without an electric field and at temperatures down to -40 °C. A single experimental run contains 40 drops exposed to the same conditions. Drops with a well-defined size are produced employing a drop-on-demand drop generator. Based on multiple experimental runs using the same drops, the nucleation behavior is analyzed using statistical methods to determine the drop survival curves and nucleation site densities for varying conditions. Besides the influence of the electric field, the influence of different drop ensembles is investigated for a constant cooling rate of 5 K/min. A comparison of the experiments with and without an electric field is used to elaborate its influence on heterogeneous ice nucleation.
... 2-4). On the other hand, low ice nucleation temperature is linked to fast ice propagation velocity ( Figure 6), and physical freezing experiments with thin ice sheets show that the faster the ice propagation velocity is the more and the smaller are the gas bubbles formed in the ice (Carte, 1961). This would decrease the risk of winter embolism formation (Mayr & Améglio, 2016;. ...
Article
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It is not well understood what determines the degree of supercooling of apoplastic sap in trees, although it determines the number and duration of annual freeze-thaw cycles in a given environment. We studied the linkage between apoplastic ice nucleation temperature, tree water status, and conduit size. We used branches of 10 gymno-sperms and 16 angiosperms collected from an arboretum in Helsinki (Finland) in winter and spring. Branches with lower relative water content froze at lower temperatures, and branch water content was lower in winter than in spring. A bench drying experiment with Picea abies confirmed that decreasing branch water potential decreases apoplastic ice nucleation temperature. The studied angiosperms froze on average 2.0 and 1.8°C closer to zero Celsius than the studied gymnosperms during winter and spring, respectively. This was caused by higher relative water content in angiosperms; when branches were saturated with water, apoplastic ice nucleation temperature of gymnosperms increased to slightly higher temperature than that of angiosperms. Apoplastic ice nucleation temperature in sampled branches was positively correlated with xylem conduit diameter as shown before, but saturating the branches removed the correlation. Decrease in ice nucleation temperature decreased the duration of freezing, which could have an effect on winter embolism formation via the time available for gas escape during ice propagation. The apoplastic ice nucleation temperature varied not only between branches but also within a branch between consecutive freeze-thaw cycles demonstrating the stochastic nature of ice nucleation.
... Bubble formation processes and shapes in lake ice have already been discussed at length by several authors (Adams et al., 1998;Bari and Hallett, 1974;Carte, 1961;Gow and Langston, 1977). These authors suggest that bubble shapes and density result from a balance between ice growth rate and diffusion of rejected gases in the liquid reservoir ahead. ...
Article
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This paper describes gas composition, total gas content and bubbles characteristics in winter lake ice for four adjacent lakes in a discontinuous permafrost area. Our gas mixing ratios for O<sub>2</sub>, N<sub>2</sub>, CO<sub>2</sub>, and CH<sub>4</sub> suggest that gas exchange occurs between the bubbles and the water before entrapment in the ice. Comparison between lakes enabled us to identify 2 major "bubbling events" shown to be related to a regional drop of atmospheric pressure. Further comparison demonstrates that winter lake gas content is strongly dependent on hydrological connections: according to their closed/open status with regards to water exchange, lakes build up more or less greenhouse gases (GHG) in their water and ice cover during the winter, and release it during spring melt. These discrepancies between lakes need to be taken into account when establishing a budget for permafrost regions. Our analysis allows us to present a new classification of bubbles, according to their gas properties. Our methane emission budgets (from 6.52 10<sup>−5</sup> to 12.7 mg CH<sub>4</sub> m<sup>−2</sup> d<sup>−1</sup> at 4 different lakes) for the three months of winter ice cover is complementary to other budget estimates, as our approach encompasses inter- and intra-lake variability. Most available studies on boreal lakes have focused on quantifying GHG emissions from sediment by means of various systems collecting gases at the lake surface, and this mainly during the summer "open water" period. Only few of these have looked at the gas enclosed in the winter ice-cover itself. Our approach enables us to integrate, for the first time, the history of winter gas emission for this type of lakes.
Article
Frosting is widely seen in the surface of an evaporator extracting heat from air in heat pump or liquid natural gas fields. The solidification of a water droplet on a cold plate surface, a phase change from liquid status to solid status as reaching its freezing point, is the key process at the early frosting stage. To accurately control the frosting/icing process, it is necessary to well understand the heat and mass transfer mechanism during the water solidification. As a fundamental problem, the characteristics of water droplet's solidification on a cold horizontal flat plate surface is reviewed. The objectives and scopes of this paper are firstly introduced. This is followed by the detailed tips before and during freezing of droplet, including the temperature variation, nucleation rate, opaque phenomenon, singular shape, evolution of freezing front, trapped air bubbles, etc. The literatures mentioned take a long time span, from 1950s to 2020. To analyze some seemingly contradictory conclusions or ideas, some of them are experimentally investigated by authors. The current research obstacles are also discussed, with the meaning of this topic re-emphasized by its large time and space scales. This comprehensive and systematic review might provide an overview of the frontiers around water droplet's solidification, and shed new light on the following experimental design and numerical validation.
Article
The coldest places on the Hawaiian island chain are not on the very summits of its tallest volcanoes, Mauna Kea (19.82°N; 4,207 m) and Mauna Loa (19.48°N; 4,169 m), but within craters and caves with perennial ice. Here, we explore unique microclimates in the alpine stone deserts of two tropical island volcanoes, report new temperature extremes for Hawaii, and study the role of microclimates in the preservation of perennial ice bodies. Nocturnal cold-air pools are common in the craters and are responsible for the coldest temperature ever reported from the Hawaiian Islands (–20°C). These cold-air pools are not frequent enough to substantially affect the annual heat budget of the ground, but cold air is frequently trapped between boulders and contributes to freezing conditions in this way. Perennial ice is found beneath even warmer environments in lava tube caves. The lowest annual-mean temperature (–0.7°C) was measured at the distal end of a spectacular ice cave on Mauna Loa, where the outside air temperature averages +8°C. In the current climate, the outside temperature rarely falls below freezing, so the air’s sensible heat cannot contribute to freezing conditions. Considering the effect of recent climate warming and the buoyancy of humid air, cold air that flowed down the lava tubes in winter nights, combined with sublimation cooling, is still a plausible explanation for the perennial ice ponds found there.
Article
Solute transport in the presence of a pore resulting from an entrapped bubble during horizontal solidification of water containing carbon dioxide is numerically and parametrically investigated. Structural material containing pores degrade microstructure, whereas materials with pores can also be functionally used to enhance efficiencies of engineering, foods and biomedical industries, and control outcome of geophysics and global warming, etc. In this study, transport equations including mass, momentum, energy and concentration transport equations satisfied by their interfacial balances between liquid, gas pore, and solid were solved with the COMSOL commercial computer code. Extending previous work dealing with influence of fluid flow, the present results further find that the effects of metallurgical and thermal properties on solute transport processes during entrapment of a bubble. Decreases in Henry's law constant, partition coefficient and liquid solute diffusivity, and increases in solid thermal conductivity increase solute concentration in solid around an entrapped pore. Predicted contact angle during solidification is in good accordance with computed analytical results confirmed by measured data. The findings of this study can help for better understanding of pore formation in the solid during horizontal solidification.
Article
Surface icing is detrimental to applications ranging from transportation to biological systems. Soft elastomeric coatings can engender remarkably low ice adhesion strength, but mechanisms at the microscale and resulting ice extraction outcomes need to be understood. Here we investigate dynamic ice-elastomer interfacial events and show that the ice adhesion strength can actually vary by orders of magnitude due to the shear velocity. We study the detailed deformation fields of the elastomer using confocal traction force microscopy and elucidate the underlying mechanism. The elastomer initially undergoes elastic deformation having a shear velocity dependent threshold, followed by partial relaxation at the onset of slip, where velocity dependent "stick-slip" micropulsations are observed. The results of the work provide important information for the design of soft surfaces with respect to removal of ice, and utility to fields exemplified by adhesion, contact mechanics, and biofouling.
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Many important chemical reactions occur in polar snow, where solutes may be present in several reservoirs, including at the air–ice interface and in liquid-like regions within the ice matrix. Some recent laboratory studies suggest chemical reaction rates may differ in these two reservoirs. While investigations have examined where solutes are found in natural snow and ice, few studies have examined either solute locations in laboratory samples or the possible factors controlling solute segregation. To address this, we used micro-computed tomography (microCT) to examine solute locations in ice samples prepared from either aqueous cesium chloride (CsCl) or rose bengal solutions that were frozen using several different methods. Samples frozen in a laboratory freezer had the largest liquid-like inclusions and air bubbles, while samples frozen in a custom freeze chamber had somewhat smaller air bubbles and inclusions; in contrast, samples frozen in liquid nitrogen showed much smaller concentrated inclusions and air bubbles, only slightly larger than the resolution limit of our images (∼ 2 µm). Freezing solutions in plastic vs. glass vials had significant impacts on the sample structure, perhaps because the poor heat conductivity of plastic vials changes how heat is removed from the sample as it cools. Similarly, the choice of solute had a significant impact on sample structure, with rose bengal solutions yielding smaller inclusions and air bubbles compared to CsCl solutions frozen using the same method. Additional experiments using higher-resolution imaging of an ice sample show that CsCl moves in a thermal gradient, supporting the idea that the solutes in ice are present in mobile liquid-like regions. Our work shows that the structure of laboratory ice samples, including the location of solutes, is sensitive to the freezing method, sample container, and solute characteristics, requiring careful experimental design and interpretation of results.
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We report on the shape dynamics of ice suspended in cold fresh water and subject to the natural convective flows generated during melting. Experiments reveal shape motifs for increasing far-field temperature: Sharp pinnacles directed downward at low temperatures, scalloped waves for intermediate temperatures between 5 °C and 7 °C, and upward pointing pinnacles at higher temperatures. Phase-field simulations reproduce these morphologies, which are closely linked to the anomalous density-temperature profile of liquid water. Boundary layer flows yield pinnacles that sharpen with accelerating growth of tip curvature while scallops emerge from a Kelvin-Helmholtz-like instability caused by counterflowing currents that roll up to form vortex arrays. By linking the molecular-scale effects underlying water's density anomaly to the macroscale flows that imprint the surface, these results show that the morphology of melted ice is a sensitive indicator of ambient temperature.
Article
Algebraic expressions for the shapes of lotus-type or isolated pores after bubbles completely entrapped in solid during unidirectional solidification are provided in this study. Functional materials of lotus-type porous metals are fabricated by unidirectional solidification of molten metals dissolving gasses such as hydrogen, oxygen or nitrogen. In view of superior and anisotropic features of mechanical, thermal and electrical properties, unidirectional lotus-type pore materials have been widely used in bio-, micro- and nano-technologies. The present model is based on a previous work by accounting for transient gas pressure in the pore affected by solute transfer and balance of gas, capillary and hydrostatic pressures, and physico-chemical equilibrium at the bubble cap. Solute transport across the bubble cap during solidification can be in different directions as previously denoted by Cases 1 and 2 due to relative magnitude between height of bubble cap and thickness of the concentration boundary layer on the solidification front. Proposing the self-consistently unified model combining Cases 1 and 2 and introducing a solute transport parameter, algebraic expressions of lotus-type pores and isolated pore can be obtained. Predicted and measured maximum radius, total length, inter-pore spacing, aspect ratio and porosity of lotus-type pores subject to Henry's law and Sievert's law as well as shape of an isolated pore during unidirectional solidification of water containing oxygen gas, liquid copper containing hydrogen, and water containing carbon dioxide, respectively, agree quite well.
Chapter
The burning of a sheet of cellulose-based material, such as paper or cloth, involves uneven shrinkage which causes wrinkling.
Article
The solidification process of water (liquid) can cause an intricate deformation of its structures, from the complex of ice crystals to dendritic frost crystal growth. The dissolved gas in water (liquid) is rejected and accumulated ahead of the ice-water interface during solidification and the resulting bubbles are incorporated into the growing ice crystal. In this study, the bubble formation process and the effect of the dissolved gas on the nucleation and growth of ice crystals in freezing droplets at various gas concentrations were experimentally investigated. The dissolved gas acted as a heterogeneous medium, and promoted the nucleation of the liquid droplets. Compared with the pure solid ice crystal, during the freezing process, the existence of bubbles altered the solid-liquid density ratio and the shape of the droplets. Coupled with experimental observations, a quantitative analysis of the tip angles was proposed to elucidate this influence , which indicated that the tip angle of the frozen ice droplet decreased with the gas concentration, and promoted the growth of the initial frost crystal.
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The physical structure dominates other physical properties of lake ice. The lake ice processes,crystal structures,air bubbles,densities,and local meteorology were investigated in a reservoir and a lake in northeastern plain for several winters in order to determine the seasonal and annual variations of lake ice microstructure and its influencing factors. It is found that the crystalline structure,air bubble content and distribution,and ice density have distinct vertical stratification,and does not change significantly during the ice growth. However,when the melting season comes,everything changes rapidly,such as crystal boundary melting,air bubble expanding,and meltwater transporting. Ice covers resemble each other in crystal types and air bubble shapes,but differ in thickness percentage of each crystal type and the content and size of air bubble in different regions or winters. Statistically,the ice crystal size increases with increasing growth rate,but the generating and dissolving processes of air in water and the water agitation influence the relationship of gas content with ice growth rate.
Article
Droplet freezing phenomenon widely exists in many fields, including aerospace, power production, and cryopreservation, etc. Considering the effects of supercooling, gravity and volume expansion, a theoretical model of droplet freezing is developed. A good agreement is found between the predicted results of freezing front radius and height and experiments for both hydrophilic and hydrophobic surfaces. The developed model also shows good performance in predicting freezing times. The average prediction deviation is 7.63%, and more than 93% simulation results show the deviation within ±15%. Gravity has a more obvious influence on final freezing times with the increase of cold plate temperature, contact angle, and droplet volume. For the droplet freezing process under various contact angles and cold plate temperatures, the fastest average temperature change rates inside water droplet are -2.48 °C/s and -1.72 °C/s, respectively. This study is beneficial for the better understanding of the droplet solidification as well as the optimization of refrigeration and defrosting technologies.
Article
Freezing of water droplet is widely seen and important in the fields of aerospace, cold energy storage, and power production. To investigate the freezing process of a sessile water droplet on a horizontal cold plate, a theoretical model was developed. Different from previously reported models, the effects of supercooling and gravity on the physical properties and the water droplet profile are both considered, respectively. This model is validated with the experimental data of two parameters, including the freezing time and the freezing front radius. The results indicate that the deviation of freezing time is decreased from 7.69% to 0.17%, while the accuracy improved by 7.52%. The average deviation of the freezing front radius is decreased from 142.90 μm to 57.94 μm, with the accuracy improved by 59.46%. At the freezing stage, the appearance of the dynamic growth angle contributes to the less deviation of the freezing front radius. The eccentricity of droplet shape decreases from 0.45 to 0.03, with the eccentricity decreased by 93.45%. The temperature change rates inside a droplet show a gradually decreasing tendency, and the temperatures at different droplet locations present different limiting values. The findings of this study are beneficial for understanding droplet solidification process as well as new technologies for refrigeration, deicing, and defrosting.
Article
A new method for preparing thin sections of wet snow is described. Samples are flash-frozen to immobilise the liquid water content (LWC). Next, the pore space is filled with ester, and the entire sample is frozen to a solid, sliceable block, Micrographs of slices are obtained using transmitted and specular illumination. The proportion of LWC is measured on the micrographs and compared with LWC measured independently using calorimetry. Section analysis is both facilitated and complicated by small bubbles which form during sample preparation. Flash-freezing and bubble formation are discussed theoretically.
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Atmospheric ice accretion results from the exposure of technical equipment or facilities to cold and humid environments. Supercooled droplets in a cloud can impact an airplane's surface and quickly form an ice layer. The presence of air pockets in such a layer is well known and explains the white appearance of some of the accretions. However, estimation of its porosity values and studies on the pore formation mechanics remain limited. In this study, we performed tests in an icing wind tunnel and scans with micro-computed tomography to address these issues. Here, we show that the accretion has closed porosity below 1%, which is mostly produced by the interaction between a spray-like impact on the water surface. The insights we provide here are important to improve ice accretion modelling techniques and establish a different approach to address the interaction between the cloud and the surfaces exposed to atmospheric icing.
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Frazil particles, ice crystals or slushy granules that form in turbulent water, change the freezing properties of ice to create “frazil ice”. To understand the microstructural characteristics of these particles and the physical properties of frazil ice in greater depth, an in situ sampler was designed to collect frazil particles in the Yellow River. The ice crystal microstructural characteristics of the frazil particles (morphology, size, air bubble, and sediment) were observed under a microscope, and their nucleation mechanism was analyzed according to its microstructure. The physical properties of frazil ice (ice crystal microstructure, air bubble, ice density, and sediment content) were also observed. The results showed that these microstructures of frazil particles can be divided into four types: granular, dendritic, needle-like, and serrated. The size of the measured frazil particles ranged from 0.1 to 25 mm. Compared with columnar ice, the crystal microstructure of frazil ice is irregular, with a mean crystal diameter less than 5 mm extending in all directions. The crystal grain size and ice density of frazil ice are smaller than columnar ice, but the bubble and sediment content are larger.
Chapter
PolarPolar regions of our planet are undergoing rapid changes, including warming of both atmosphere and underlying surface (Kokhanovsky and Tomasi 2020) and decrease of snowSnow/iceIce extent/albedoAlbedo (Tedesco 2015) with corresponding impacts on polarPolar environments (Barry and Hall-McKim 2018).
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Solute segregation of carbon dioxide in water during entrapment of a bubble by a solidification front is numerically investigated. The bubble can be initiated by supersaturation ahead of the solidification front. Porosity influences not only microstructure of materials, but also formation of functional materials in biology, engineering, foods, and geophysics, and so on. The model was proposed in a previous work accounting for conservation equations with interfacial balances of mass, momentum, energy and concentration. Using commercial COMSOL computer code, this study further finds that different solute distributions in liquid and solid in the presence of an entrapping bubble can be attributed to solute diffusivity of liquid and partition coefficient. A high solute diffusivity of liquid enhances solute diffusion away from the pore along the solidification front, leading to negligible solute transport from liquid to solidification front, whereas a low solute diffusivity of liquid gives rise to significant solute transport from the solidification front to liquid. A decrease in solute diffusivity of liquid or partition coefficient therefore results in high solute accumulation and a high concentration region covering liquid and solid in a triangle shape near the triple-phase line. In contrast to exponential decrease for a high solute diffusivity of liquid, radial variation of solute concentration in solid in the vicinity of pore jumps to high value through the high concentration region and maintains relative constant for a low diffusivity of liquid. Solute concentration in solid significantly decreases as solute diffusivity of liquid or partition coefficient increases. Predicted contact angle agree with solutions of Abel's equation of the first or second kind. This work is critical to understand solute segregation induced by formation of a pore in solid.
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Distant glacial areas are interconnected by a complex system of fractures and water channels which run in the glacier interior and characterize the englacial realm. Water can slowly freeze in these channels where the slow freezing excludes air bubbles giving the ice a clear aspect. This ice is uplifted to the surface ablation zone by glacial movements and can therefore be observed in the form of clear surface ice bands. We employed an indirect method to sample englacial water by coring these ice bands. We were able, for the first time, to compare microbial communities sampled from clear (i.e. frozen englacial water bands) and cloudy ice (i.e. meteoric ice) through 16S rRNA gene sequencing. Although microbial communities were primarily shaped and structured by their spatial distribution on the glacier, ice type was a clear secondary factor. One area of the glacier, in particular, presented significant microbial community clear/cloudy ice differences. Although the clear ice and supraglacial communities showed typical cold-adapted glacial communities, the cloudy ice had a less defined glacial community and ubiquitous environmental organisms. These results highlight the role of englacial channels in the microbial dispersion within the glacier and, possibly, in the shaping of glacial microbial communities.
Article
Detection of damage in safety-critical components with complex geometry represents a long-standing challenge in NDE. The ultrasonic inspection of these parts in immersion is often not feasible due to the large impedance and velocity contrast between water and metals which can severely limit the penetration of the ultrasonic signal inside the part. However, this contrast can be significantly reduced if the water is frozen prior to the inspection leading to what has been referred to as Cryoultrasonic NDE. Since the speed of longitudinal waves in ice is more than 2.5 times greater than the speed in water, ice can be an ideal solid couplant provided that it is devoid of bubbles and cracks and that it is fully bonded to the surface of the part. This paper introduces new experimental methods to encase complex parts in blocks of crystal clear ice and presents the first low temperature scanner for ultrasonic array testing of ice-encapsulated parts. It is shown that by controlling the propagation of the solidification front while water is freezing, it is possible to prevent the formation of cracks inside the ice volume. On the other hand, bubble nucleation can be avoided by continuously forcing water circulation on the solidification front. An analytical model is provided to describe the propagation of the front and predict freezing times. Moreover, high-frequency ultrasonic monitoring experiments confirm the excellent adhesion strength properties of ice to metals. Finally, experiments performed with an additively manufactured Ti–6Al–4V impeller demonstrate the feasibility of performing low temperature array contact scans on the surface of the ice block encasing the part.
Article
Ice formation can be problematic on surfaces such as roads, bridges, wings, and sensitive plants. A simple low-cost sensor for detecting the formation of ice has been developed using standard low-cost commercial printed circuit board fabrication techniques. The sensor consists of a capacitive interdigitated electrode structure realized in the top Cu layer of the circuit board and covered with polymeric solder mask. The sensor's capacitance is measured at 1 kHz and at 64 kHz, and then the ratio of the two capacitances is computed. The ratio is then compared with a threshold value of 2.0. Icing results in the capacitance ratio exceeding 2.0, whereas dry conditions or water results in a ratio of less than 2.0. This technique exploits the dielectric relaxation properties of ice in that it has a high dielectric constant below the relatively low dielectric relaxation frequency of ≤ 3 kHz, and a low dielectric constant well above that frequency. The sensor was evaluated in air, water, and ice over a temperature range of $-30^{\circ}C$ to $30^{\circ}C$ , and successfully identified ice every time.
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Late embryogenesis abundant (LEA) proteins comprise a diverse family whose members play a key role in abiotic stress tolerance. As intrinsically disordered proteins, LEA proteins are highly hydrophilic and inherently stress tolerant. They have been shown to stabilise multiple client proteins under a variety of stresses, but current hypotheses do not fully explain how such broad range stabilisation is achieved. Here, using neutron reflection and surface tension experiments, we examine in detail the mechanism by which model LEA proteins, AavLEA1 and ERD10, protect the enzyme citrate synthase (CS) from aggregation during freeze–thaw. We find that a major contributing factor to CS aggregation is the formation of air bubbles during the freeze–thaw process. This greatly increases the air–water interfacial area, which is known to be detrimental to folded protein stability. Both model LEA proteins preferentially adsorb to this interface and compete with CS, thereby reducing surface-induced aggregation. This novel surface activity provides a general mechanism by which diverse members of the LEA protein family might function to provide aggregation protection that is not specific to the client protein.
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Aquatic ecosystems with organic‐rich sediments are a globally significant source of methane to the atmosphere. In shallow waters, ebullition is often a dominant emission pathway of methane. Current knowledge on the processes controlling gas bubble formation and persistence in aquatic sediments is limited. An important prerequisite for accurate quantification of the structure and methane bubbles in sediment samples is to preserve the ambient in situ conditions during the withdrawal process and further analysis. A novel freeze corer has been developed that facilitates sampling of gas‐bearing soft sediments for X‐ray computer tomography. The sampler allows freezing sediment inside a double‐walled corer with a mixture of dry ice and ethanol. This corer has moderate costs and offers important advantages for gassy sediment sampling. Its simplicity and robustness allow to perform sampling from a small boat and the ability to characterize in situ sediment features. The applicability of this freeze coring technique for gas bubble quantification was validated during laboratory experiments aimed to investigate the effects of freezing on sediment gas content, bubble size distribution, and their geometry by comparing computer tomography scans of unfrozen vs. frozen cores. The performance of the corer was further evaluated during field conditions in Lake Kinneret (the Sea of Galilee, Israel). The results demonstrate the suitability of the freeze‐coring method for in situ preservation of gas‐bearing sediments. The sediment structure, however, showed some displacements of sediments layers and bubble abundance in some core regions. Future investigations are needed to address the nature of disturbances of the frozen sediment.
Chapter
Unwanted icing can lead to dangerous situations for both daily life and infrastructure, and deicing methods in use today are either inefficient or expensive. Passive anti‐icing surfaces, or icephobic surfaces, ensure that no ice is formed on the surface or structure, without the need of adding external energy to the system. The most promising pathway towards icephobic surfaces is the lowering of ice adhesion strength, so that the ice is self‐removed from the surface due to natural wind or its own weight. However, the physics of ice adhesion is not fully understood yet and developed low ice adhesion surfaces cannot be directly compared, both due to the formation of the ice and the measurement of the ice adhesion strength, which are not standardized. This chapter presents the results of an interlaboratory study where the ice adhesion strengths of two surfaces were tested in two different laboratory facilities with two types of ice, ensuring comparability between analogous ice types. The results display the same trends with some significant differences and indicate that the type of ice accretion is less important when the ice adhesion is low. Similarly, the difference between ice adhesion tests is smaller for low ice adhesion strengths. The standard deviations seem to scale with the absolute value of the ice adhesion strength. To fully compare different ice adhesion measurements and advance the scope of low ice adhesion surfaces, a reference test basis should be agreed upon, and more comparative experiments should be performed.
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A new electrification and discharge model was developed based on a two‐moment bin microphysical scheme coupled with the Weather and Forecasting (WRF) model. Based on the electrical model, the role of the noninductive charging mechanism associated with the melting processes of both snow and graupel (rimed particles) in the charge structure formation in the stratiform region of an organized convective system was examined. Our results showed that the snow melting charging mechanism forms a substantial positive charge layer near and below 0°C isotherm in the stratiform region of a squall line. It was also found that the graupel melting charging process mostly enhanced the positive charge layer in the convective region with little impact in the stratiform region. The in‐situ charging of noninductive collisional and melting processes, and the charge transportation from the convective core all contribute to the charge structure formation in the stratiform region of a squall line.
Article
Hypothesis: Understanding the crystallization of atmospheric water can require levitation techniques to avoid the influence of container walls. Recently, an acoustic levitation device called the TinyLev was designed, which can levitate multiple droplets at room temperature. Proximal crystallization may affect droplet phase change and morphological characteristics. Methodology In this study, acoustically levitated pure water droplets were frozen individually and in pairs or triplets using a TinyLev device. Nucleation, bulk crystal growth, and melting were observed using digital and infrared cameras concurrently. Findings: Initially, the acoustic field forced the droplets into an oblate spheroid shape, though the counteracting force of the cooling stream caused them to circularize. Droplet geometry was thus the net result of streaming forces and surface tension at the acoustic boundary layer/air-liquid interface. Nucleation was determined to be neither homogeneous nor heterogeneous but secondary, and thus dependent on the cooling rate and not on the degree of supercooling. It was likely initiated by aerosolized ice particles from the air or from droplets that had already nucleated and broken up. The latter secondary ice production process resulted in multi-drop systems with statistically identical nucleation times. Notably, this meant that the presence of interfacial rupture at an adjacent droplet could influence the crystallization behaviour of another. After the formation of an initial ice shell around the individual droplets, dendritic protrusions grew from the droplet surface, likely seeded by the same ice particles that caused nucleation, but at a quasi-liquid layer. When freezing was complete, it was determined that the frozen core had undergone a volumetric expansion of 30.75%, compared to 9% for pure, sessile water expansion. This significantly greater expansion may have resulted from entrained air bubbles at the inner solid-liquid interface and oscillations at the moving phase boundary caused by changes in local acoustic forces. Soon after melting began, acoustic streaming, the buoyancy of the remaining ice, and convective currents caused by an inner thermal gradient and thermocapillary effects along the air-liquid interface, all contributed to the droplet spinning about the horizontal axis.
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The microstructure of polycrystalline ice with a threading solution of brine controls its numerous characteristics, including the ice mechanical properties, ice–atmosphere interactions, sea ice albedo, and (photo)chemical behavior in and on the ice. Ice samples were previously prepared in laboratories in order to study various facets of ice–impurity interactions and (photo)reactions to model natural ice–impurity behavior. We examine the impact of the freezing conditions and solute (CsCl used as a proxy for naturally occurring salts) concentrations on the microscopic structure of ice samples via an environmental scanning electron microscope. The method allows us to observe the ice surfaces in detail, namely, the free ice, brine puddles, brine-containing grain boundary grooves, individual ice crystals, and imprints left by entrapped air bubbles at temperatures higher than −25 ∘C. The amount of brine on the external surface is found proportional to the solute concentration and is strongly dependent on the sample preparation method. Time-lapse images in the condition of slight sublimation reveal subsurface association of air bubbles with brine. With rising temperatures (up to −14 ∘C), the brine surface coverage increases to remain enhanced during the subsequent cooling and until the final crystallization below the eutectic temperature. The ice recrystallization dynamics identify the role of surface spikes in retarding the ice boundaries' propagation (Zener pinning). The findings thus quantify the amounts of brine exposed to incoming radiation, available for the gas exchange, and influencing other mechanical and optical properties of ice. The results have straightforward and indirect implications for artificially prepared and naturally occurring salty ice, respectively.
Article
Emerging nanofluid-based technologies for cooling, transport, and storage applications have previously been enhanced through the use of graphene nanoflake (GNF) nanofluids. Many of the beneficial effects of GNFs have now been documented, though little work has yet been completed to characterize the morphological behaviour of GNF nanofluids both during and after the phase change process. In this study, the crystallization behaviour of sessile water droplets was evaluated for two plasma-functionalized, hydrophilic GNF concentrations (20 and 100 ppm) at three driving force temperatures (-5, -10, and -20 °C). At low driving forces, the GNFs were wholly expelled from the solid matrix due to low crystallization velocities. At high driving forces, more rapid crystallization rates resulted in the entrapment of GNFs within the air bubbles and inter-dendritic spaces of the solid droplet. However, individual particle dispersion was not achieved within the solid matrix at any driving force. Furthermore, for all experimental conditions, the functionalized GNF clusters which formed during freezing did not disperse spontaneously upon melting as drying-like effects may have altered the attraction properties of their surfaces and destabilized the suspension. Compared to previous studies using MWCNTs, the GNFs were found to have higher liquid mobility at the solid front, provide less resistance to that front as it ascended, and be better dispersed after melting. These effects may have been geometrical; the square nanoflake geometry does not result in any physical particle entanglement.
Article
This study shows that there exist the universal three phase diagrams to describe general development of the pore shape in solid, resulting from a bubble captured by a solidification front with different solidification rates. Pore formation and its shape strongly determine microstructural quality of materials, functional materials encountered in biology, chemistry, engineering, foods, and phenomena of geophysics and climate change, and so on. The solidification rate plays an important role in solute transport and gas pressure, contact angle of the bubble cap, and pore shape in solid. Three universal phase diagrams are under dimensionless coordinate systems of (1) solidification rate, temperature gradients in solid and liquid at the solidification front, (2) solidification rate, contact angle and growth rate of base radius of the cap, and (3) apex radius, contact angle and base radius of the cap. Solidification rate is determined by temperature gradients in liquid and solid at the solid-liquid interface governed by the Stefan boundary condition, whereas apex radius is determined by solute gas pressure in the pore governed by the Young-Laplace equation, equation of state, and different cases governing directions of mass transfer in the pore. Extending previous analysis, phase diagrams in this study confirm that the bubble cannot be completely entrapped in Case 2b, which represents a stronger effect of pore volume expansion on solute gas pressure than solute transport from the surrounding liquid to pore in the early stage. The computed and measured results of development of the pore shape are in good agreement.
Article
As the human excreta, urine is often used as one of the test materials in medical research due to its composition and content directly reflecting the health status of the body. Considering that the substances in urine may show different effects on its freezing process, solidification characteristics of sessile urine droplets on a horizontal cold plate surface under natural convection were experimentally investigated by comparing with those of water droplets under same conditions. To make the conclusion analysis more reasonable, the urine of a human without any diseases, especially metabolic diseases, was treated and used. The characteristics include nucleation location, dynamic variation of droplet color, and temperatures at different heights inside the droplet, and so forth. It was found that, similar to that of a water droplet, the solidification process of a urine droplet also experiences the following four stages: supercooling, recalescence, freezing, and cooling, in chronological order. Differently, the urine droplet changes from transparent to blur white at the supercooling stage due to the precipitation of inorganic salts. For nucleation locations, 46.67% cases are at the bottom, while others are at the top and middle of urine droplets. For a 10 μL droplet on a surface of -30 °C, urine has a 0.95 s freezing duration shorter than water, and a 5.31 °C lower phase-transition temperature. Results of this study are expected to reflect the content of substances in urine and thus provide references for urinalysis of patients with metabolic diseases.
Article
Dissolved oxygen content in rainwater has been measured in Tokyo by means of the Winklar's titration method since September 1957. The sample of rainwater has been collected in a bottle containing a liquid paraffin. In most rainfalls rainwater was found to be unsaturated with the dissolved oxygen at the time of its arrival to the ground as Miyake and Saruhashi (1949) pointed out, its saturation percentages being between 85 and 100% for rainfalls during the period of September 1957 to March 1958. Snow was found to contain about 6cc oxygen per litre of melted snow, which is about 60% as compared with the oxygen content of saturated water at 0°C and normal pressure. Values of oxygen content for each precipitation were related to the structure of raincloud. This shows that the oxygen content in rainwater has a close correlation with the height of cloud base and with the mechanism of raindrop formation. A possible explanation for the cause of the unsaturation and the significance of the obtained results for studies of precipitation mechanism are discussed.
Article
This chapter discusses several techniques of zone melting and crystal growing. The field of application of zone melting may be described as the field of controlled solidification or crystallization. This field encompasses the careful preparation, from the melt or from solution, of crystalline materials of all kinds including metals, semiconductors, and organic and inorganic compounds. The general term, “zone melting,” denotes a family of methods for controlling the distribution of soluble impurities, or simply solutes, in crystalline materials. In all these methods a short molten zone travels slowly through a relatively long solid charge and as the zone travels it redistributes solutes in the charge. A molten zone traversing an ingot has two liquid-solid interfaces, a melting interface and a freezing interface. The field of single crystal growing is broad and variegated. The main factor influencing the growth rate of a rather pure single crystal from its melt is believed to be the rate at which the latent heat of solidification is extracted from the liquid-solid interface. To grow an oriented crystal from the melt, a seed crystal is placed in contact with a dequilibrated with the cool end of the melt. Next, its temperature is slowly reduced so as to cause the interface to advance through the melt.
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Observations and measurements of more than 15 samples of soft hail and small hail disclose the nature and the growing process of these particles.
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