Supercooled Liquid State Research Articles

Decoupled alpha and beta relaxation kinetics in a thermally cycled bulk Pd40Ni40P20 glass

Reproducible thermodynamic sample states of a Pd40Ni40P20 bulk metallic glass are realized via differential scanning calorimetry by repeated quenching from the supercooled liquid state to temperatures well below the glass transition. Annealing treatments at 0.81 Tg and 0.96 Tg are embedded in the calorimetric method, changing the energetical state of the system. Varying the annealing times, a detailed and reproducible picture of the reversible relaxation dynamics with separated α- and β-relaxation is obtained. An endothermic signature before Tg can either be provoked or depressed depending on the annealing temperature. The activation energy related to this process is obtained via Kissinger analyses yielding about 30 RTg. A large number of annealing cycles at 0.96 Tg irreversibly alters the response of the α-relaxation, while the mechanism of β-relaxation is interestingly not influenced by this alternation. In order to extend the calorimetric response of the relaxation spectra to spatial resolution, the sample states were additionally analyzed using electron correlation microscopy providing information on the glass dynamics on an atomistic scale. The thus obtained kinetic parameters of local dynamics do not show an alteration of room temperature dynamics for different levels of α-relaxation, which is consistent with the results obtained via kinetic analyses of calorimetric data.

Experimental Evaluation of the Rheological Properties and Influencing Factors of Gel Fracturing Fluid Mixed with CO2 for Shale Gas Reservoir Stimulation.

Foam gel fracturing fluid has the characteristics of low formation damage, strong flowback ability, low fluid loss, high fluid efficiency, proper viscosity, and strong sand-carrying capacity, and it occupies a very important position in fracturing fluid systems. The rheological properties of gel fracturing fluid with different foam qualities of CO2, under different experimental temperatures and pressures, have not been thoroughly investigated, and their influence on it was studied. To simulate the performance of CO2 foam gel fracturing fluid under field operation conditions, the formula of the gel fracturing fluid was obtained through experimental optimization in this paper, and the experimental results show that the viscosity of gel fracturing fluid is 2.5 mPa·s (after gel breaking at a shear rate of 500 s−1), the residue content is 1.3 mg/L, the surface tension is 25.1 mN/m, and the interfacial tension is 1.6 mN/m. The sand-carrying fluid has no settlement in 3 h with a 40% sand ratio of 40–70-mesh quartz sand. The core damage rate of foam gel fracturing fluid is less than 19%, the shear time is 90 min at 170 s−1 and 90 °C, the viscosity of fracturing fluid is >50 mPa·s, and the temperature resistance and shear resistance are excellent. The gel fracturing fluid that was optimized was selected as the base fluid, which was mixed with liquid CO2 to form the CO2 foam fracturing fluid. This paper studied the rheological properties of CO2 foam gel fracturing fluid with different CO2 foam qualities under high temperature (65 °C) and high pressure (30 MPa) and two states of supercooled liquid (unfoamed) and supercritical state (foamed) through indoor pipe flow experiments. The effects of temperature, pressure, shear rate, foam quality, and other factors on the rheological properties of CO2 foam gel fracturing fluid were considered, and it was confirmed that among all the factors, foam quality and temperature are the main influencing factors, which is of great significance for us to better understand and evaluate the flow characteristics of CO2 foam gel fracturing fluid and the design of shale gas reservoir fracturing operations.

Effect of sodium lauryl sulfate-mediated gelation on the suppressed dissolution of crystalline lurasidone hydrochloride and a strategy to mitigate the gelation

In dissolution test, the surfactant sodium lauryl sulfate (SLS) is usually added to increase the dissolution of insoluble drugs and achieve the sink condition. However, the current study found that 0.1 % SLS would significantly decrease the dissolution of crystalline lurasidone hydrochloride (LH, a BCS Ⅱ drug). The aim of this study was to clarify the mechanism of this unexpected phenomenon and explore a strategy for mitigating the negative effect of SLS on the dissolution of LH. Sample characterizations (such as PLM, DSC, PXRD, IR and NMR) confirmed that the insoluble single-phase amorphous LH-SLS complex (with a single Tg at 35.2 °C) formed during dissolution in 0.1 % SLS aqueous solution via electrostatic interaction, tetrel bond interaction, and hydrophobic effect. Due to the plasticization effect of water, the transition of amorphous LH-SLS from its glassy state to viscous supercooled liquid state led to the gel formation, and suppressd the dissolution of LH. Meanwhile, the solubility curve of LH in SLS aqueous solution at various concentrations exhibited an unusual V-shaped feature, with the CMC value of SLS serving as the inflection point, since the gel degree was attenuated due to the micelle solubilization of SLS. Additionally, an innovative strategy was developed to alleviate the inhibiting effect of SLS on LH dissolution based on the potential competitive interactions. This study not only enriches the internal mechanism of surfactant-inhibited drug dissolution but also informs an effective strategy to mitigate the gelation.

Role of Fe substitution for Co on thermal stability and glass-forming ability of soft magnetic Co-based Co-Fe-B-P-C metallic glasses

Soft magnetic Co-based bulk metallic glasses (BMGs) with large supercooled liquid region (ΔTx) of 47 K and high saturation magnetic flux density (Bs) up to 1.21 T have been developed in a new Co-Fe-B-P-C alloy system without early transition metal and rare earth elements. Substitution of Co by 10–35 at.% Fe in a Co75B10P7.5C7.5 alloy promotes the occurrence of glass transition and enhances the stability of supercooled liquid and glass-forming ability (GFA). The ΔTx of 37–47 K and a critical sample diameter up to 1.2 mm can be achieved for Co40–55Fe20–35B10P7.5C7.5 BMGs. The improved thermal stability and GFA are attributed to complicated primary crystallization phases and stabilized alloy melts, respectively. The addition of Fe enhances the Bs of the Co-based BMGs from 0.79 to 1.21 T, and increases coercivity from 1.1 to 7.2 A/m. The Co-based BMGs also exhibit high yield strength of 3243–3665 MPa with plastic strain up to 2.3% and low viscosity of around 3.0 × 109 Pa·s in the supercooled liquid state.

Density Scaling of Translational and Rotational Molecular Dynamics in a Simple Ellipsoidal Model near the Glass Transition.

In this paper, we show that a simple anisotropic model of supercooled liquid properly reflects some density scaling properties observed for experimental data, contrary to many previous results obtained from isotropic models. We employ a well-known Gay–Berne model earlier parametrized to achieve a supercooling and glass transition at zero pressure to find the point of glass transition and explore volumetric and dynamic properties in the supercooled liquid state at elevated pressure. We focus on dynamic scaling properties of the anisotropic model of supercooled liquid to gain a better insight into the grounds for the density scaling idea that bears hallmarks of universality, as follows from plenty of experimental data collected near the glass transition for different dynamic quantities. As a result, the most appropriate values of the scaling exponent γ are established as invariants for a given anisotropy aspect ratio to successfully scale both the translational and rotational relaxation times considered as single variable functions of densityγ/temperature. These scaling exponent values are determined based on the density scaling criterion and differ from those obtained in other ways, such as the virial–potential energy correlation and the equation of state derived from the effective short-range intermolecular potential, which is qualitatively in accordance with the results yielded from experimental data analyses. Our findings strongly suggest that there is a deep need to employ anisotropic models in the study of glass transition and supercooled liquids instead of the isotropic ones very commonly exploited in molecular dynamics simulations of supercooled liquids over the last decades.

Predicting Dielectric and Shear-Rheology Properties of Glass-Forming Pharmaceutical Liquids from Each Other: Applications and Limitations.

Acetaminophen, nicotine, and lidocaine hydrochloride were investigated in their deeply supercooled liquid states using oscillatory shear rheology. The mechanical spectra of these drugs are presented in modulus, compliance, as well as fluidity formats. Their frequency profiles can be described via models adapted from the field of charge transport. Inspired by the success of this approach, the Barton-Nakajima-Namikawa relation, best known from the same field, was also tested. When adapted to rheology, this approach interrelates static and dynamic characteristics of viscous flow and was found to work excellently. The temperature dependence of the characteristic shear frequencies was checked against the shoving model, which relates them to the temperature-dependent instantaneous shear modulus and acceptable agreement was found. Combined with shear mechanical literature data on ibuprofen and indomethacin, a modified version of the phenomenological model by Gemant, DiMarzio, and Bishop (GDB) was employed to successfully predict the shape and amplitude of the dielectric spectra for all studied liquids, except for lidocaine hydrochloride. For the latter, the modified GDB model is suggested to aid in mapping out the reorientational part of the dielectric response, while the experimental results are strongly superimposed by ionic conduction phenomena. The reverse transformation, the calculation of rheological spectra based on dielectric ones, is also successfully demonstrated. For the example of acetyl salicylic acid, it is shown how dielectric spectra can be used to even predict rheological ones. The limits of the central parameter governing these mutual transformations, the electroviscoelastic material constant, and indications for its correlation with the dielectric relaxation strength are discussed. For pharmaceuticals characterized by a strong dynamical decoupling of the electrical from the mechanical degrees of freedom, the modified GDB model is not expected to be applicable.

Viscosity, surface tension, and density of binary mixtures of the liquid organic hydrogen carrier diphenylmethane with benzophenone

The liquid organic hydrogen carrier (LOHC) diphenylmethane may react to benzophenone in the presence of air, especially at elevated temperatures. Therefore, information about the influence of benzophenone added to diphenylmethane on process-relevant thermophysical properties is required. In the present contribution, the liquid viscosity, surface tension, and liquid density of binary mixtures of diphenylmethane with benzophenone are determined between (283 and 573) K using complementary experimental methods. Investigations on the surface tension by the pendant-drop method and surface light scattering indicate molecular orientation effects of benzophenone at the vapor-liquid interface. With increasing benzophenone content, an increase in density, surface tension, and especially viscosity is found. For the latter property, a distinct change in the temperature dependence is observed at the transition from the liquid to the supercooled liquid state. Furthermore, water dissolved in benzophenone causes changes within 15% and 3% relative to the viscosity and surface tension of benzophenone, respectively. • Surface light scattering and conventional methods applied between 283 and 573 K. • Surface tension measurements indicate surface orientation effects of benzophenone. • Larger density, surface tension, and viscosity with increasing benzophenone content. • Big change in temperature dependence of viscosity from liquid to supercooled liquid. • Dissolved water has minor impact on viscosity and surface tension of benzophenone.

Volumetric and viscosity data of selected oils analyzed in the density scaling regime

In this paper, we have performed thorough analyses of volumetric and viscosity data for six oils. The volumetric data has been inspected by using two different equations of state, drawing a special attention to the intersection of the isothermal pressure dependences of the thermal volume expansivity, which were earlier reported for various materials in the liquid state. Each fluid is unique with respect to the other oils’ relative composition, with those being either a pure liquid (Sebacate), or mineral oil with a proprietary blend of branched paraffins, napthalenes and aromatic molecules (Normafluid) or are undisclosed composition of mineral oil (MIN-H01 and MIN-H02) or are composed of fatty acid methyl esters (soybean biodiesel and rapeseed biodiesel). We have confirmed that the intersection points evaluated for different isotherms constitute a nonlinear curve for a given tested oil, and not any single point or straight line. Consequently, we have determined the temperature–pressure areas important from the application viewpoint, within which the thermal volume expansivity behaves differently, either increasing or decreasing with increasing temperature at a constant pressure. In the viscosity analysis, the parametrizations of the temperature–pressure dependences of specific volume based on the equations of state enabled to employ the density scaling idea in its simplest form of a power law of densityγ/temperature, where γ related to an effective intermolecular potential is independent of thermodynamic conditions to a good approximation, which was successfully validated by various materials mainly in the supercooled liquid state, but also in the normal liquid and liquid crystal states in some cases. We have found that the scaling law giving prediction benefits relied on a linkage between macroscopic measurement quantities and effective molecular interactions is obeyed by the viscosity data of examined oils. Then, based on the prediction capabilities of the density scaling criterion, we have successfully explored the inflection points observed in some isothermal pressure dependences of viscosity measured for the oils in the temperature–pressure ranges that differ from those earlier reported for other materials. This intriguing finding observed in case of the experimental data for only some examined oils yields not only cognitive benefits, but it is also expected to exert an effect for instance on mechanical properties of the materials. Thus, our comparative discussion about the intersection and inflection curves provide a useful contribution to the further investigations of these thermodynamic and dynamic issues and other physicochemical properties of oils, which require gaining a better insight.

Origin of ductility in amorphous Ag2S0.4Te0.6

Amorphous Ag2S0.4Te0.6 shows outstanding ductility and promising thermoelectric properties at room temperature [He et al., Sci. Adv. 6, eaaz8423 (2020)], while the origin of its exceptional ductility is still not very clear. Here, we systematically investigate the temperature-dependent structure and thermodynamic behavior of the Ag2SxTe1−x (x = 0–1.0) system by means of in situ x-ray powder diffraction and dynamic thermodynamic analysis, respectively. Our experimental results reveal that the degree of crystallization in Ag2SxTe1−x varies continuously with the ratio of S and Te. The Ag2S0.4Te0.6 sample is composed of two amorphous phases, i.e., the S-rich and Te-rich Ag2(S,Te) glasses. The S-rich Ag2(S,Te) amorphous phase with the atomic ratio about Ag:S:Te = 66:21:13 is identified as the ductile phase, which is the origin of ductility in the Ag2S0.4Te0.6 sample. The Ag2S-based glass in the supercooled liquid state at room temperature behaves like a Newtonian fluid at low strain rates, leading to the excellent ductility of Ag2S0.4Te0.6. Our work demonstrates the great potential to design and realize flexible inorganic functional materials through amorphization.

Annealing-induced phase transitions in a Zr–Ti–Nb–Cu–Ni–Al bulk metallic glass matrix composite containing quasicrystalline precipitates

Abstract The phase formation of a copper-mold-cast Zr60Ti2Nb6Cu14 Ni9Al9 alloy has been investigated upon cooling from the melt as well as upon annealing of as-cast specimens. The different states of the samples are characterized by X-ray diffraction, optical and electron microscopy, and differential scanning calorimetry. The cooling rate as realized upon copper-mold casting leads to micrometer-sized quasicrystals, which are embedded in a glassy phase. The thermal stability ΔTx of the supercooled liquid state of the glassy phase that forms near to the wall of the copper mold, differs from that of the glassy matrix in the center of the rod due to different compositions of the glassy phase. This is a consequence of the change in local cooling conditions, which affects the phase formation upon solidification as well as the subsequent transformation behavior of the alloy upon constant-rate heating.

Universal scaling law of glass rheology.

The similarity in atomic/molecular structure between liquids and glasses has stimulated a long-standing hypothesis that the nature of glasses may be more fluid-like, rather than the apparent solid. In principle, the nature of glasses can be characterized by the dynamic response of their rheology in a wide rate range, but this has not been realized experimentally, to the best of our knowledge. Here we report the dynamic response of shear stress to the shear strain rate of metallic glasses over a timescale of nine orders of magnitude, equivalent to hundreds of years, by broadband stress relaxation experiments. The dynamic response of the metallic glasses, together with other 'glasses', follows a universal scaling law within the framework of fluid dynamics. The universal scaling law provides comprehensive validation of the conjecture on the jamming (dynamic) phase diagram by which the dynamic behaviours of a wide variety of 'glasses' can be unified under one rubric parameterized by the thermodynamic variables of temperature, volume and stress in the trajectory space.

Fast crystal growth of amorphous nimesulide: implication of surface effects.

Understanding crystallization behaviors is of utmost importance for developing robust amorphous pharmaceutical solids. Herein, the crystal growth behaviors of amorphous anti-inflammatory drug nimesulide (NIME) are systemically investigated in the glassy and supercooled liquid state as a function of temperature. A sudden over-tenfold increase is observed in the bulk crystal growth of NIME on cooling below its glass transition temperature (Tg). This fast growth behavior is known as a glass-to-crystal (GC) mode and has been reported in some molecular glasses. Fast surface crystal growth of NIME can persist up to Tg + 57°C with a weak jump in its growth rates at 30-40°C. In addition, surface crystal growth and GC growth of NIME exhibit an almost identical temperature dependence, supporting the view that GC growth is indeed a surface-facilitated process. Moreover, the bubble-induced fast crystal growth of NIME is observed in the interior of its supercooled liquid with approximately the same growth kinetics as surface crystal growth. These findings are relevant for a full understanding of the surface-related crystallization behaviors and physical stability of amorphous pharmaceutical formulations.

Mechanistic insight into gel-induced aggregation of amorphous curcumin during dissolution process

Amorphous curcumin (CUR) exhibited a decreased dissolution rate in comparison with the crystalline counterpart due to its gel formation during dissolution. The main purpose of the present study is to explore the mechanism of such gelation phenomenon. It was found that the dissolution of amorphous CUR and gel properties were influenced by the temperature and pH of the media. The formed gels were characterized by TPA, SEM, DSC, XRPD, FTIR and PLM. The results indicated that the gelation process led to the formation of a porous structure in which water molecules infiltrate, and entered into its supercooled liquid state with high viscosity when contacting aqueous media, accompanied by decreased Tg and crystalline transformation. In addition, mixing with hydrophilic excipients (such as hydrophilic silica) accelerated the gel formation of amorphous CUR, while the addition of hydrophobic excipients (such as hydrophobic silica and magnesium stearate) could effectively weaken and even eliminate the gelation, hence significantly improving its dissolution. Furthermore, according to contact angle measurement and fluorescence microscope observation, hydrophilic excipients were found to be able to accelerate water entering into the interior of amorphous CUR, hence facilitating the gelation, while hydrophobic excipients would hinder water infiltration into the powder and thus achieve degelation. In conclusion, it is important to recognize that the gelation potential of some amorphous materials should be considered in developing robust amorphous drug product of high quality and performance.

Studies on the Vitrified and Cryomilled Bosentan.

In this paper, several experimental techniques [X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry, Fourier transform infrared spectroscopy, and broad-band dielectric spectroscopy] have been applied to characterize the structural and thermal properties, H-bonding pattern, and molecular dynamics of amorphous bosentan (BOS) obtained by vitrification and cryomilling of the monohydrate crystalline form of this drug. Samples prepared by these two methods were found to be similar with regard to their internal structure, H-bonding scheme, and structural (α) dynamics in the supercooled liquid state. However, based on the analysis of α-relaxation times (dielectric measurements) predicted for temperatures below the glass-transition temperature (Tg), as well as DSC thermograms, it was concluded that the cryoground sample is more aged (and probably more physically stable) compared to the vitrified one. Interestingly, such differences in physical properties turned out to be reflected in the lower intrinsic dissolution rate of BOS obtained by cryomilling (in the first 15 min of dissolution test) in comparison to the vitrified drug. Furthermore, we showed that cryogrinding of the crystalline BOS monohydrate leads to the formation of a nearly anhydrous amorphous sample. This finding, different from that reported by Megarry et al. [Carbohydr. Res.2011, 346, 1061−106421492830] for trehalose (TRE), was revealed on the basis of infrared and thermal measurements. Finally, two various hypotheses explaining water removal upon cryomilling have been discussed in the manuscript.

ELECTROCHEMICAL POLYMORPHIC PHASE FORMATION IN METALS

The phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage was discussed. Assuming the electrodeposited metal to be a product of formation and ultrarapid solidification of supercooled metallic liquid, a possibility of metastable phase formation during electrodeposition of polymorphous metals was suggested. It was anticipated that the polymorphic transition of the metal’s metastable form to the stable one occurs by shear, as does the martensitic transformation. To enable revealing an orientation relationship between grains of the two phases, a method for X-ray texture analysis of metals was developed using a combination of direct pole figures. It was established that the phase formation during electrodeposition of polymorphous metals produces metastable modifications typical of entities that crystallized from a liquid state at extremely high rates. In regards polymorphic transitions in metal electrodeposition, certain orientation relationships were observed between grains of the stable and the metastable phase, which is typical of phase transformations proceeding at extremely high rates. The results obtained provided additional arguments in favor of the phenomenon under discussion.

Dielectric polarization of cross-linked poly(ethylene oxide)—phenomenology

Results of dielectric relaxation studies will be discussed. It turns out that competition of electric and structural relaxation coins permittivity and as a result conductivity mechanism at low temperature. It dominates long-ranging relaxation in the molten state. In the opposite limit of temperature, cross-linked poly(ethylene oxide) (PEO) with low mesh size can be transferred into super-cooled liquid state. Then, PEO behaves like a hydrogen-bonded liquid since crystallization is strongly suppressed. As a result, one observes slow Debye-like relaxation at low temperature. Beyond the low-frequency region, there appears an extended region between crossings of impedance components, where Z′ ≈ Z″ at acceptable approximation. It is coined by damped oscillation under action of the electric field. These effects lessen with increasing mesh size of the sample as clearly shown by M″(ω) spectra. The dipole moment of the PEO samples in molten state decreases only slightly with increasing mesh size.

Modeling the relaxation and crystallization kinetics of glass without fictive temperature: Toy landscape approach

AbstractRelaxation and crystallization are key kinetic processes that must be understood to build a comprehensive understanding of the supercooled liquid and glassy states. Traditional approaches have been unable to capture the underlying physics accurately due to assumptions about phenomenological order parameters such as fictive temperature. In this work, we show that glass relaxation can be accurately modeled through a simplified “toy” enthalpy landscape approach, bypassing the use of fictive temperature. Moreover, the same simplified enthalpy landscape provides insights into the thermodynamics and kinetics of crystallization. The toy landscape approach recovers key predictions from the traditional fictive temperature description, but it is based on a more accurate physical framework, giving fundamental knowledge of the glass relaxation and crystallization processes.

Glasses denser than the supercooled liquid

When aged below the glass transition temperature, [Formula: see text], the density of a glass cannot exceed that of the metastable supercooled liquid (SCL) state, unless crystals are nucleated. The only exception is when another polyamorphic SCL state exists, with a density higher than that of the ordinary SCL. Experimentally, such polyamorphic states and their corresponding liquid-liquid phase transitions have only been observed in network-forming systems or those with polymorphic crystalline states. In otherwise simple liquids, such phase transitions have not been observed, either in aged or vapor-deposited stable glasses, even near the Kauzmann temperature. Here, we report that the density of thin vapor-deposited films of N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) can exceed their corresponding SCL density by as much as 3.5% and can even exceed the crystal density under certain deposition conditions. We identify a previously unidentified high-density supercooled liquid (HD-SCL) phase with a liquid-liquid phase transition temperature ([Formula: see text]) ∼35 K below the nominal glass transition temperature of the ordinary SCL. The HD-SCL state is observed in glasses deposited in the thickness range of 25 to 55 nm, where thin films of the ordinary SCL have exceptionally enhanced surface mobility with large mobility gradients. The enhanced mobility enables vapor-deposited thin films to overcome kinetic barriers for relaxation and access the HD-SCL state. The HD-SCL state is only thermodynamically favored in thin films and transforms rapidly to the ordinary SCL when the vapor deposition is continued to form films with thicknesses more than 60 nm.

Elastoplasticity Mediates Dynamical Heterogeneity Below the Mode Coupling Temperature.

As liquids approach the glass transition temperature, dynamical heterogeneity emerges as a crucial universal feature of their behavior. Dynamic facilitation, where local motion triggers further motion nearby, plays a major role in this phenomenon. Here we show that long-ranged, elastically mediated facilitation appears below the mode coupling temperature, adding to the short-range component present at all temperatures. Our results suggest deep connections between the supercooled liquid and glass states, and pave the way for a deeper understanding of dynamical heterogeneity in glassy systems.

Thermodynamic Characteristics of Phenacetin in Solid State and Saturated Solutions in Several Neat and Binary Solvents.

The thermodynamic properties of phenacetin in solid state and in saturated conditions in neat and binary solvents were characterized based on differential scanning calorimetry and spectroscopic solubility measurements. The temperature-related heat capacity values measured for both the solid and melt states were provided and used for precise determination of the values for ideal solubility, fusion thermodynamic functions, and activity coefficients in the studied solutions. Factors affecting the accuracy of these values were discussed in terms of various models of specific heat capacity difference for phenacetin in crystal and super-cooled liquid states. It was concluded that different properties have varying sensitivity in relation to the accuracy of heat capacity values. The values of temperature-related excess solubility in aqueous binary mixtures were interpreted using the Jouyban–Acree solubility equation for aqueous binary mixtures of methanol, DMSO, DMF, 1,4-dioxane, and acetonitrile. All binary solvent systems studied exhibited strong positive non-ideal deviations from an algebraic rule of mixing. Additionally, an interesting co-solvency phenomenon was observed with phenacetin solubility in aqueous mixtures with acetonitrile or 1,4-dioxane. The remaining three solvents acted as strong co-solvents.