Freezing Temperature Depression Research Articles

Heterogeneous ice nucleation of salt solution in porous media.

Water ubiquitously exists with dissolved salt in both natural and engineered porous media, such as soil, rock, concrete, and tissue; therefore, its freezing temperature depression behavior is of particular interest to various scientific communities tackling with mechanics and physics of porous media. To date, it remains elusive which physical mechanism accounts for its freezing temperature depression and how dissolved ions affect it. Herein, a series of pore-scale experiments were designated to investigate the freezing temperature of salt solutions in tubes with varying pore diameters, pore solution volumes, solid-liquid interfacial areas, ion concentrations, and ion types. The results reveal two main findings: (i) the freezing temperature depression of pore solutions is governed by the heterogeneous ice nucleation (HIN) at the water-solid interface, as evidenced by the observation that the freezing temperature decreases with the decreasing solid-liquid interfacial areas, regardless of pore diameter and pore solution volume; (ii) the dissolved salts alter HIN processes via changing the osmotic potential across the ice embryo-liquid water interface, as indicated by the observation that the freezing temperature is mainly determined by the salt concentration irrespective of salt types. Furthermore, the classical nucleation theory model is adapted for the freezing behavior of pore solutions by including an osmotic potential term. The model shows excellent performance in capturing experimental data with various pore solution concentrations, further substantiating the HIN as the physical mechanism governing pore solution freezing.

Physical origins of freezing and melting temperature depressions of water in millimeter-sized pores

As a long-standing problem, the physics of freezing and melting temperature depressions of water in millimeter-sized pores remains elusive. We devised a series of experiments on the freezing and melting of water in glass tubes with varying tube diameters, water volumes, water-solid interfacial areas, and cooling rates. The results of the experiments indicate that the freezing temperature depression is highly correlated with the water-solid interfacial areas. It can be inferred that heterogeneous nucleation is the dominant physical origin for such freezing temperature depression. In contrast, melting temperature depression is orders of magnitude lower than that of freezing, and is independent of heating rate, water volume, water-solid interfacial area, and correlated with pore diameter, suggesting the governing role of capillarity. The recognized distinct physical origins of freezing and melting temperatures lead to the disparity between them, i.e., freezing and melting hysteresis. The findings resolve the controversy on the freezing mechanism of water in millimeter-sized pores, and can be used to better manipulate freezing and melting behaviors of pore water in various engineering applications, e.g., promoting or inhibiting freezing in biomaterials, and developing anti-freezing materials.

Influence of the Inclusion of Propylene Carbonate Electrolyte Solvent on the Microstructure and Thermal and Mechanical Stability of Poly(l-lactic acid) and Poly(vinylidene fluoride-co-hexafluoropropylene) Battery Separator Membranes.

The influence of the inclusion of the organic solvent propylene carbonate (PC) in microporous membranes based on poly(l-lactic acid) (PLLA) and poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) has been studied based on its relevance for the application of those separator membranes in lithium-ion batteries. The membranes have been produced through solvent casting and characterized with respect to the swelling ratio originated by the uptake of the organic solvent. The organic solvent uptake affects the porous microstructure and crystalline phase of both membrane types. The organic solvent uptake amount affects the crystal size of the membranes as a consequence of the interaction between the solvent and the polymer, since the presence of the solvent modifies the melting process of the polymer crystals due to a freezing temperature depression effect. It is also shown that the organic solvent partially penetrates into the amorphous phase of the polymer, leading to a mechanical plasticizing effect. Thus, the interaction between the organic solvent and the porous membrane is essential to properly tailor membrane properties, which in turn will affect lithium-ion battery performance.

A Thermodynamic Formulation of Water Potential in Soil

AbstractIn the mid‐20th century, harnessing of thermodynamics in describing water movement in soil, viz the concept of water potential, marks the emergence of modern soil physics, unsaturated soil mechanics, and vadose zone hydrology. Yet to date, a seamless linkage between thermodynamics and water potential is still missing, leading to several long‐lasting dilemmas regarding soil properties, for example, abnormal soil water density, peculiar film water viscosity and relative permittivity, pore water pressure, and water freezing temperature depression. Here, a thermodynamic framework is established by synthesizing recent advancements in soil‐water interaction. The classical thermodynamic concepts are revisited, highlighting the difference between macroscopic systems commonly treated in conventional theories and the intermolecular scale system subject to external fields. Soil water is conceived as an intermolecular scale open thermodynamic system subject to external fields of gravity, osmosis, and adsorption. The formulated thermodynamic framework is verified by reducing to the conventional definition of matric potential and a recently proposed unitary definition. The accuracy of the framework is further justified in terms of mechanical equilibrium criteria. The framework predicts the existence of spatially varied pore water pressure in soil pores and can serve as the theoretical basis for reconciling the physical origin of abnormal soil behavior such as water density, film water viscosity, relative permittivity, and negative or positive pore water pressure.

A thermodynamic model for calculating the unfrozen water content of frozen soil

On the basis of thermodynamic principles, the relationship between freezing temperature depression and pore radius of soil has been derived. Combined with the soil pore size distribution, this paper proposes a thermodynamic model for calculating unfrozen water content, and investigates the effects of pore radius, nonfreezable layer, and pore shape on unfrozen water content. Comparison of calculated results with the experimental data shows that the model provides a reasonable approximation for calculating the unfrozen water content of frozen soil. Moreover, the mechanism of unfrozen water content change for different soil types, initial water contents can be well explained. The study not only establish a relationship between the unfrozen water content and pore size distributions of soils, but also provide a thermodynamic reference to understand the mechanism of phase transitions in frozen soils.

Microscopic diffusion in hydrated encysted eggs of brine shrimp

BackgroundWe have studied microscopic diffusion of water in fully hydrated encysted eggs of brine shrimp (Artemia). MethodsWe have utilized quasielastic neutron scattering. ResultsDry eggs of brine shrimp were rehydrated using (1) water without additives, (2) eutectic mixture of water and dimethyl sulfoxide, and (3) a concentrated aqueous solution of lithium chloride. Despite the complexity of the hydrated multicellular organism, measurable microscopic diffusivity of water is rather well defined. Pure hydration water in eggs exhibits freezing temperature depression, whereas hydration water in eggs mixed with dimethyl sulfoxide or lithium chloride does not crystallize at all. ConclusionsThe characteristic size of the voids occupied by water or aqueous solvents in hydrated brine shrimp eggs is between 2 and 10nm. Those voids are accessible to co-solvents such as dimethyl sulfoxide and lithium chloride. There is no evidence of intracellular water in the hydrated eggs. General significanceThe lack of intracellular water in the fully hydrated (but still under arrested development) state must be linked to the unique resilience against adverse environmental factors documented not only for the anhydrous, but also hydrated encysted eggs of brine shrimp.

Pore distribution of water-saturated compacted clay using NMR relaxometry and freezing temperature depression; effects of density and salt concentration

The estimation of water population in water-saturated compacted clay was studied with 1H NMR relaxometry and freezing point depression. The clay samples and saturated condition were Na-montmorillonite at 0.8 and 1.4g/cm3 saturated by three salt concentrations (deionized water, 0.1mol/L and 1.0mol/L). The water-saturated compacted samples were prepared in PCTFE cylinder by immersed in the liquid under vacuum for 1month. All NMR measurements were conducted using intact PCTFE vessel, which was possible to keep confinement condition during experiment.In order to distinguish interlayer with four hydrated state and non-interlayer water, we assumed four T1 thresholds corresponding to 1-, 2-, 3, and 4 hydrated layers, which were 1.2, 2.3, 3.5, and 4.7ms, respectively. The populations of hydrated state and non-interlayer water were calculated from these thresholds at 30°C. The sample with lower density exhibits higher population of non-interlayer water up to 55%.Low-temperature 1H NMR experiments were also conducted to support these results in view of freezing point depression against pore size. Mesopore water in approximately 4nm space observed in the calorimetric study was considered as non-interlayer water and the threshold temperature, which was equivalent to a freezing point of −12.5°C from Gibbs–Thomson equation. The result showed that population of non-interlayer water by expected from freezing point depression agreed with 1H NMR relaxometry within 10%. Correlation experiments were also conducted between longitudinal (T1) and transverse relation times (T2) at −10°C to obtain dynamical information on water. A small peak was obtained close to a T1/T2 line of 1.0 at a clay density of 1.4g/cm3, suggesting that high-mobility bulk-like water molecules existed in this sample.

Molecular Dynamics Simulations of Freezing Behavior of Pure Water and 14% Water-NaCl Mixture Using the Coarse-Grained Model

We performed molecular dynamics simulations using the coarse-grained model to study the freezing behavior of pure water and 14% water-salt mixture in a wide range of temperatures for a very long time around 50 nanoseconds. For the salty water, an interface in nanoscale was used. For both systems, the freezing behavior of water molecules was studied using some qualities such as density, total energy, and radial distribution function. For the 14% water-salt mixture, the equilibrium freezing temperature depression observed in the simulations was well consistent with the experimental data. Contrary to the water-salt mixture, however, the above- mentioned quantities changed dramatically for the pure water at the freezing point. The plots of the total energy versus time shows the freezing point of 14% water-salt mixture was 265 K that is 9 K less than the freezing point of pure water. The reduction of freezing point is in very good agreement with the experimental freezing point. The results of the simulation showed that in the less temperature than obtained freezing point, the sodium and chloride ions tendency to network formation and rejection of solution lead to reduction of water molecules accumulation.

Phase transition of carbonate solvent mixture solutions at low temperatures

The phase transition of carbonate solvent mixture solutions consisting of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and LiPF6 salt have been studied for improving the low temperature performance of lithium-ion batteries.The Li ion conductivity at 25 °C was maximum at x = 0.3 in a series of 1 M LiPF6 mixed carbonate solvents compositions consisting of ECxDMC0.5−0.5xEMC0.5−0.5x (x = 0 to 0.6), while the maximum tended to shift to x = 0.2 as the temperature lowered. The differential scanning calorimetry results showed that the freezing temperature depressions of EC in the 1 M LiPF6 solution were larger than those of the DMC or EMC. The chemical shift of 7Li nuclear magnetic resonance changed from a constant to increasing at around x = 0.3, which could be reasonably understood by focusing on the change in solvation energy calculated using Born equation. However, in the region of a high EC concentration of over x = 0.3 (EC/LiPF6 > 4) in the 1 M LiPF6 solution, the free EC from the solvation to the lithium ions seems to reduce the freezing temperature depression of the EC, and thus, decreases the ionic conductivity of the solution at low temperatures, due to the EC freezing.

Size-dependent freezing of n-alcohols in silicon nanochannels

We present a study on the phase behavior of several linear n-alcohols (heptanol, nonanol and undecanol) in their bulk state as well as confined in mesoporous silicon. We were able to vary the mean pore radii of the nanochannels from r = 3.5 nm to 7 nm and to determine the respective temperatures of the freezing and melting transitions using infrared and dielectric spectroscopy. The smaller the chain length the lower the freezing point, both in the bulk and in the confined state. Under confinement the freezing temperature decreases by up to 28 K compared to the bulk value. In accordance with the Gibbs-Thompson model the lowering is proportional to the inverse pore radius, ΔTfr ∝ 1/r. Moreover, the ratio of freezing temperature depression to melting temperature depression is close to the theoretical value of ΔTfr/ΔTmelt = 3/2. The spectra also indicate a structural change: while the solid bulk alcohols are a polycrystalline mixture of the orthorhombic β- and monoclinic γ-form, geometrical confinement forces the alcohol-chains into the more simple orthorhombic structure. In addition, a part of the material does not crystallize. Such an additional amorphous phase seems to be a logical consequence of the size mismatch between molecular crystals and irregular shaped pores.

Effect of Sulfate Contaminant on Soil Properties and Infrastructure Safety in Permafrost Regions

Contamination of unfrozen water in frozen soil could have adverse effects on surrounding infrastructure such as foundation instability or deterioration of trafficability. This paper describes the results of the experimental examination of the physical properties and mechanical behavior of Na2SO4 contaminated soil. Initial freezing temperature test, unfrozen water content test and unconfined compression tests were conducted on silts with 3 levels of concentrations (6, 18 and 42 ppt) of Na2SO4 and nonsaline cases at temperatures ranging between 0°C and -20°C. The test results indicate that the presence of salt significantly affect the physical properties and mechanical behavior of the frozen soil. Contamination of soils will cause depression of freezing temperature and degradation of permafrost. The freezing temperature depression ratio of Na2SO4 contaminated soil is 0.028°C/ppt. The unfrozen water content increases with an increase in salinity and temperature. The strength decreases with an increase in salinity, and the strength loss ratio of Na2SO4 contaminated soil is among 0.02-0.04MPa/ppt. Combined the effect of salinity and temperature on the strength, the decrease in strength with increase in unfrozen water content follows an exponential relationship. So estimation of salt concentration in the soil, and predictions of future increases of salt in the soil, is essential for design of buildings and roadways in permafrost.

Prediction of Frozen Food Properties during Freezing Using Product Composition

Frozen water fraction (FWF), as a function of temperature, is an important parameter for use in the design of food freezing processes. An FWF-prediction model, based on concentrations and molecular weights of specific product components, has been developed. Published food composition data were used to determine the identity and composition of key components. The model proposed in this investigation had been verified using published experimental FWF data and initial freezing temperature data, and by comparison to outputs from previously published models. It was found that specific food components with significant influence on freezing temperature depression of food products included low molecular weight water-soluble compounds with molality of 50 micromol per 100 g food or higher. Based on an analysis of 200 high-moisture food products, nearly 45% of the experimental initial freezing temperature data were within an absolute difference (AD) of +/- 0.15 degrees C and standard error (SE) of +/- 0.65 degrees C when compared to values predicted by the proposed model. The predicted relationship between temperature and FWF for all analyzed food products provided close agreements with experimental data (+/- 0.06 SE). The proposed model provided similar prediction capability for high- and intermediate-moisture food products. In addition, the proposed model provided statistically better prediction of initial freezing temperature and FWF than previous published models.

Behaviour of pure water and water mixture with benzene or chloroform adsorbed onto ordered mesoporous silicas

Abstract Structural characteristics of synthesized ordered mesoporous silicas MCM-41, MCM-48 and SBA-15 were studied using XRD, nitrogen adsorption and FTIR methods. Pure water and mixtures with water/benzene and water/chloroform-d adsorbed onto silicas were studied by 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial liquids. Concentrated aqueous suspensions of MCM-48 and SBA-15 were studied by thermally stimulated depolarization current (TSDC) method. Benzene and chloroform-d can displace a portion of water to broad pores from the pore walls and from narrower pores, especially in the case of a large excess of an organic solvent. This process is accompanied by diminution of both interaction energy of water with an adsorbent surface and freezing temperature depression of adsorbed water. The effect of nonpolar benzene on pore water is much stronger than that of weakly polar chloroform-d. Modifications of the Gibbs-Thomson relation to describe the freezing point depression of mixtures of immiscible liquids confined in pores allow us to determine distribution functions of sizes of structures with unfrozen pore water and benzene.

A two-dimensional adsorption kinetic model for thermal hysteresis activity in antifreeze proteins

Antifreeze proteins (AFPs) and antifreeze glycoproteins (AFGPs), collectively abbreviated as AF(G)Ps, are synthesized by various organisms to enable their cells to survive in subzero environments. Although the AF(G)Ps are markedly diverse in structure, they all function by adsorbing to the surface of embryonic ice crystals to inhibit their growth. This adsorption results in a freezing temperature depression without an appreciable change in the melting temperature. The difference between the melting and freezing temperatures, termed thermal hysteresis (TH), is used to detect and quantify the antifreeze activity. Insights from crystallographic structures of a number of AFPs have led to a good understanding of the ice-protein interaction features. Computational studies have focused either on verifying a specific model of AFP-ice interaction or on understanding the protein-induced changes in the ice crystal morphology. In order to explain the origin of TH, we propose a novel two-dimensional adsorption kinetic model between AFPs and ice crystal surfaces. The validity of the model has been demonstrated by reproducing the TH curve on two different beta-helical AFPs upon increasing the protein concentration. In particular, this model is able to accommodate the change in the TH behavior observed experimentally when the size of the AFPs is increased systematically. Our results suggest that in addition to the specificity of the AFPs for the ice, the coverage of the AFPs on the ice surface is an equally necessary condition for their TH activity.

Application of Antifreeze Protein for Food Preservation: Effect of Type III Antifreeze Protein for Preservation of Gel‐forming of Frozen and Chilled Actomyosin

ABSTRACTType III antifreeze protein (AFP) remarkably preserved Ca2+ ATPase activity of actomyosin during frozen and chilled storage. Under frozen conditions, AFP helped to retain the Ca2+ ATPase activity of actomyosin much higher than that of conventional cryoprotectants (sucrose‐sorbitol mixture). The Ca2+ ATPase activity increased with increasing AFP concentration and reached a maximum at 50g/L AFP. After 3‐d chilled storage, the Ca2+ ATPase activity of control and sucrose‐sorbitol samples had lost 80% and 50%, respectively, while the AFP samples remained unchanged. A Type III AFP mechanism based on freezing temperature depression (more unfrozen water) and inhibition of ice recrystallization that protects against the freezing of muscle proteins in chilled or frozen conditions is proposed.

Temperature gradient osmometer and anomalies in freezing temperatures.

We have developed a new device that measures freezing and melting temperatures in nanoliter volume samples and can be used as a "freezing point osmometer" with a resolution many orders of magnitude greater than that of existing freezing point osmometers. Using this device we found anomalies in the depression of the freezing temperature and thermal hysteresis in aqueous solutions of hydrophilic amino acids, polyamino acids, and lectins. These anomalies would not have been possible to detect with currently used technology. The compounds that produce anomalies in freezing temperature were reported in the literature as having the ability to bind to cell membranes. This suggests a relation between a molecule's ability to bind to cell membranes and its anomalous freezing temperature depression. The new freezing point osmometer and our results could be important for studying and understanding organic molecules and their interaction with membranes and water.

Isopiestic determination of the osmotic and activitycoefficients of Aqueous Lu2(SO4)3

Osmotic coefficients have been measured for aqueous Lu2(SO4)3 solutions from 0.12402 to 0.89631 mol-kg−1 at 25°C by use of the isopiestic method; these measurements extend into the supersaturated molality region. Since there was a lack of activity data for Lu2(SO4)3 solutions at lower molalities, they were approximated by equating them to results for La2(SO4)3 from freezing temperature depression measurements. The combined osmotic coefficients were then used to derive mean molal activity coefficients for Lu2(SO4)3 solutions. The osmotic coefficients decrease to 0.307 as their minimum value and the mean molal activity coefficients decrease to 0.0069. When these activities were combined with our previously reported solubility of 0.6260±0.0017 mol-kg−1 for Lu2(SO4)3·8H2O, a thermodynamic solubility product of 2.3×10−10 was obtained. This value yields the Gibbs energy of formation ΔGf° (Lu2(SO4)3·8H2O, cr)=−5518.9±16.4 kJ-mol−1.

Antifreeze glycoproteins from Polar fish. Effects of freezing conditions on cooperative function.

Antifreeze glycoproteins and glycopeptides that function noncolligatively contribute one-third of the freezing temperature depression in the blood serum of some polar fishes and enable them to survive at low temperature (-1.9 degree C). There are at least eight closely related glycoproteins and glycopeptides ranging in molecular weight from 32,000 to 2,600 and numbered 1 to 8 in order of decreasing size. Under conditions of negligible supercooling, the glycopeptides have weaker antifreeze activity than the glycoproteins (20% on a weight basis, or 5% on a molar basis); in mixtures of both, their activities are additive. When nucleation is initiated in supercooled solutions (-4 to -5 degrees C), the glycopeptides are inactive, while the glycoproteins still show activity; when mixtures of both are nucleated in supercooled solutions, cooperative potentiation occurs, and the full activities of the glycopeptides are found. On nucleation of supercooled solutions of the glycoprotein alone or of the mixtures, the temperature rises above the freezing temperature ("overshoots") to an extent dependent upon the extent of supercooling; the temperature of the sample then decreases to form a plateau at the true freezing temperature.

Raman spectra of a solid antifreeze glycoprotein and its liquid and frozen aqueous solutions.

Raman spectroscopy was used to study the anomalous decrease in the freezing temperature of water produced by an antifreeze glycoprotein obtained from the sera of an Antarctic fish. An active fraction of this glycoprotein has a molecular weight of approximately 18,000 by equilibrium sedimentation compared to an apparent weight of 20 by freezing temperature depression. The Raman spectra of water present in a 1% antifreeze glycoprotein solution and of ice frozen from this solution were indistinguishable from the spectra of pure water and ice, respectively. These results indicate that the bulk properties of water and ice are unaffected by the presence of the antifreeze glycoprotein. Raman measurements on ice grown slowly, using as seed an oriented single crystal of ice in contact with 1% glycoprotein solutions, showed that the active glycoprotein was not excluded from the ice phase. On the other hand, we found that a smaller, inactive glycoprotein was excluded. Comparison of the Raman spectra of active and inactive glycoprotein components as solids, in 5% solutions, and rapidly frozen 5% solutions, showed that the two components differ in conformation and possibly in the environment of their carbohydrate hydroxyls. These observations suggest that hydrogen bonding of the carbohydrate hydroxyls of the active glycoprotein at the ice-solution interface may physically prevent growth of the ice lattice.