Supercooled Liquid Phase Research Articles

Acoustic properties of aspirin in its various phases and transformation stages studied by Brillouin scattering

The acoustic behaviors of aspirin were studied in its crystal, liquid, glass states as well as transformation stages between them. The Brillouin doublet of the longitudinal acoustic (LA) mode propagating to the [100] direction of aspirin crystals showed a splitting in a temperature range of 393–413 K below the melting temperature, which indicated a softening and distortion of the layered aspirin crystal in its premelting stage. One LA mode was observed in the liquid and glassy phases of aspirin, consistent with Brillouin selection rule for isotropic materials. The acoustic damping in the glassy aspirin was systematically higher than that in the crystal aspirin, which was in contrast to ibuprofen materials. These suggested different activity of remnant local dynamics that could couple to the acoustic waves, persistent in the glassy state of these two representative pharmaceuticals. In the supercooled liquid phase, the Brillouin spectrum displayed a new spectral feature characterized by a high-frequency cutoff and a distributed low-frequency contribution other than the Brillouin peak of the amorphous aspirin. This could be ascribed to the formation of crystalline grains in the glassy matrix due to cold crystallization.

Distribution and Coordination State of Titanium Oxides in Microstructures Formed by Spinodal Decomposition in Multicomponent Borosilicate Glass

Tetrahedrally coordinated titanium oxides implanted into inorganic materials aid in the removal of air-based pollutants by photocatalytic reactions. We investigated the distribution and the coordination state of titanium oxides in a phase-separated glass formed by the spinodal decomposition to obtain porous glass containing tetrahedrally coordinated titanium oxides. Various glass compositions containing titanium oxides were prepared by partially replacing SiO2 with B2O3 and small amounts of TiO2 in multicomponent silicate glass compositions where a spinodal decomposition had been confirmed. Interconnected microstructures that consist of two different phases were observed in heat-treated glass samples using transmission electron microscopy and these microstructures underwent spinodal decomposition. Compositional analyses of these microstructures using energy dispersion spectroscopy revealed that the decomposed phase with higher concentration of SiO2 contains smaller amount of titanium oxides than the other phase. Thermodynamic analysis was conducted to evaluate the distribution of titanium oxides in the glass phases, formed by a phase separation in the multicomponent borosilicate glass, where glass was regarded as a super-cooled liquid phase. In the thermodynamic analysis, the calculated activity of TiO2 in the two decomposed glass phases indicated that the glass phase with higher concentration of SiO2 contains lower concentration of titanium oxides. Porous glasses containing titanium oxide were fabricated from the spinodal-decomposed borosilicate glass by leaching one of the separated phases with an acid solution. Ti K-edge X-ray absorption near edge structure spectra indicated that the porous glass contains tetrahedrally coordinated titanium oxides.

Observation of the dynamics of clusters in d-glucose with the use of dielectric spectroscopy

Dielectric and FTIR measurements were performed on d-glucose in its supercooled liquid phase. The data obtained revealed that apart from the structural relaxation. a much slower relaxation mode exists in the liquid phase of d-glucose. Analysis of the dielectric data showed that this new mode exhibits features characteristic of the cluster relaxation process, i.e. the exponential relaxation function, as well as the equilibration time which is much longer than the relaxation time. Therefore we attributed this process to the long range correlation of density fluctuations (LRCDF). We also show that above T = 370 K the dielectric strength of the cluster relaxation starts to decrease rapidly. However FTIR measurements indicated that at T = 366 K reorganization of the liquid structure occurs. Combined dielectric and FTIR data showed that above T = 366 K clusters become less stable and probably disintegrate. Moreover the splitting temperature T(s) = 387 K was determined from the dielectric data. Its value corresponds to the temperature T = 385 K at which the change of dynamics of the hydroxyl group (hydrogen bonds) is observed. It can be assumed that the change of dynamics of the d-glucose (at T(s)) is related to the temperature at which LRCDF vanishes. It should be added that to the best of our knowledge this is the first dielectric study on dynamics of clusters in carbohydrates. Moreover, due to our studies the relaxation map of monosaccharides seems now to be complete.

Precursive stage of nanocrystallization in niobium oxide-containing glass

In situ observation of inelastic light scattering in Raman and Boson regions was performed in a niobiogermanate glass with a high nucleation ability during heating in order to examine its nanocrystallization dynamics. The relation of structural heterogeneity to the precursive stage of crystallization is also discussed. It is suggested that evolution of nuclei occurs in a nanometric niobate-rich region due to density fluctuation in the supercooled liquid phase prior to nanocrystallization.

Softer region at boundary of supercooled liquid–crystal in glassy fresnoite

The transition between the supercooled liquid (SCL) and crystal phases was investigated by in situ observation of boson peak in a glassy fresnoite (Ba2TiSi2O8) with an extremely high nucleation ability. The glassy fresnoite revealed anomalous boson behavior, in that the boson peak's full width at half maximum diverged at T/Tg∼1.2. This behavior suggests that an elastically softer region exists at the interface of the fresnoite nucleus/crystallite in the SCL state.

Prediction of phase separation in multi-component oxide glass for the fabrication of porous glass materials from waste slag

Thermodynamic analyses were performed to evaluate the composition ranges for metastable immiscibility including spinodal decomposition in multi-component silicate systems, where glass was regarded as a super-cooled liquid phase. Experimental studies on two-phase separation in glass were carried out, and the phase separation was observed in those silicate glasses corresponding to calculated metastable miscibility gaps.The authors also attempted the fabrication of porous glass using phase separation in oxide glasses containing B2O3. A multi-component borosilicate glass composition was prepared based on the silicate glass composition where spinodal decomposition had been confirmed. One of the glass phases formed by the spinodal decomposition in the boro-silicate glass was selectively removed by acid leaching and porous glass was successfully obtained.

The physics and the chemistry of the heat pad

Flexing a metallic disk triggers the crystallization of the supercooled sodium acetate solution contained in commercial heat pads. Many mechanisms have been proposed to explain the apparent nucleation of crystalline material. In this paper a simple experiment is described that demonstrates that nucleation is triggered by preserving seed crystals clamped between opposing metal surfaces. An explanation for the retention of the crystalline particles is the elevated melting point caused by very high local pressures. A series of thermophysical properties of the sodium acetate solution is also measured, including the available enthalpy upon crystallization of the supercooled substance, and liquid and solid phase specific heat capacities.

Formation of Ice-like Water Structure on the Surface of an Antifreeze Protein

Antifreeze proteins (AFPs) are found in different species from polar, alpine, and subarctic regions where they serve to inhibit ice crystal growth by adsorption to ice surfaces. Computational methods have the power to investigate the antifreeze mechanism in atomic detail. Molecular dynamics simulations of water under different conditions have been carried out to test our water model for simulations of biological macromolecules in extreme conditions: very low temperatures (200 K) and at the ice/liquid water interface. We show that the flexible F3C water model reproduces properties of water in the solid phase (ice I(h)), the supercooled liquid phase, and at the ice/liquid water interface. Additionally, the hydration of the type III AFP from ocean pout was studied as a function of temperature. Hydration waters on the ice-binding surface of the AFP were less distorted and more tetrahedral than elsewhere on the surface. More ice-like hydrating water structures formed on the ice-binding surface of the protein such that it created an ice-like structure in water within its first hydration layer but not beyond, suggesting that this portion of the protein has high affinity for ice surfaces.

Materials Design for the Fabrication of Porous Glass using Phase Separation in Multi-component Borosilicate Glass

Porous glass was fabricated using spinodal decomposition in multi-component oxide glass and leaching out one of the decomposed phases with acid solution. Multi-component borosilicate glass compositions were designed for the porous glass by partially replacing SiO2 by B2O3 in silicate glass compositions where the occurrence of spinodal decomposition was confirmed. One of separated phases formed by the spinodal decomposition in the borosilicate glass was leached out with acid solution and then porous glass was obtained. The microstructure in porous glass was observed by field emission scanning electron microscopy, and the development of an interconnected porous structure was indicated. Prediction of the phase separation was attempted for multi-component borosilicate glass compositions investigated in this study by calculating the Gibbs energy of super-cooled liquid phase. It was revealed the calculated metastable liquid–liquid immiscibility boundaries in these borosilicate systems do not coincide with experimental results for the occurrence of phase separation. For the precise estimation of the miscibility gap in the multi-component oxide glasses containing B2O3, the temperature and composition dependence of Gibbs energy of liquid phase, including the super-cooled liquid state, should be optimized.

Effect of nano-quasicrystals on viscosity of a Zr-based bulk metallic glass

The effect of formation of nano-quasicrystals on the creep behavior of a Zr 44 Ti 11 Cu 10 Ni 10 Be 25 bulk metallic glass was studied by the indentation technique above the glass transition temperature . The apparent viscosity of the supercooled liquid–quasicrystal composite increases with increasing volume fraction of the quasicrystalline phase following a simple relationship derived previously for dilute suspensions. The formation of quasicrystalline particles is accompanied by the decrease of activation energy of creep. This was related to the increase of the Be/Ti ratio in the supercooled liquid phase.

FeSiBNb 리본 합금의 비정질 형성능과 자기적 특성에 미치는 Co의 첨가 효과

큰 비정질 형성능을 가지는 FeSiBNb 비정질 리본 합금의 열적 및 자기적 특성에 미치는 Co의 첨가 효과에 대하여 연구되었다. 두께 <TEX>$40\;{\mu}m$</TEX>의 비정질<TEX>$(Fe_{1-X}Co_X)_{72}Si_4B_{20}Nb_4(x=0{\sim}0.5)$</TEX> 합금에 대한 열분석 결과, Fe에 대한 Co의 치환량이 증가할수록 과냉각 액상의 존재 온도 범위가 넓어져 비정질 형성능이 증가하는 것으로 평가되었다. 또 Co 농도의 증가에 따라 약간의 <TEX>$B_8$</TEX>(800A/m에서의 유도 자속밀도)의 감소가 얻어지나, 투자율이 현저하게 증가하고 철손이 크게 감소하는 경향을 나타내었다. 한편 두께가 두꺼운 상기 비정질 합금의 교류 투자율의 주파수 특성은 와전류에 의한 표피 효과의 증대 때문에 <TEX>$20\;{\mu}m$</TEX> 정도의 두께를 가지는 통상의 비정질 리본 합금에 비해 열화되는 것으로 나타났다. The thermal and magnetic properties of amorphous (FeCo)SiBNb ribbon alloys with high glass forming ability have been investigated. The glass forming ability was enhanced by Co substitution in amorphous (<TEX>$Fe_{1-X}Co_X)_{72}Si_4B_{20}Nb_4$</TEX> alloys with the thickness of about <TEX>$40{\mu}m$</TEX>. With the increase in Co content, the temperature range of supercooled liquid phase increased indicating the high glass forming ability of the Co-added alloys. Further the ac permeability increased, and the core loss decreased considerably by Co substitution, while small change in <TEX>$B_8$</TEX> (magnetic flux density at 800 A/m) was observed. The frequency characteristics of permeability deteriorated as compared to conventional amorphous ribbon alloys with the thickness of about <TEX>$20\;{\mu}m$</TEX> due to the increased skin effect.

Anomaly in temperature dependence of thermal transport of two hydrogen-bonded glass-forming liquids

The thermal conductivity of two molecular glasses (ethanol and 1-propanol) decrease with increasing temperature up to their glass transitions at ${T}_{g}\ensuremath{\approx}97$ and $98\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively. Within their supercooled liquid phases, the conductivity increases with rising temperature up to a maximum which roughly coincides with the liquidus (or melting temperatures ${T}_{m}\ensuremath{\approx}159\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and ${T}_{m}\ensuremath{\approx}149\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively). From there on, the conductivity decreases with increasing temperature, a behavior common to most liquids examined so far, exception made of liquid water. The origin of the rather different dependencies with temperature of thermal transport is understood as a competition between phonon-assisted and diffusive transport effects which are amenable to experiments using high resolution quasielastic neutron scattering and visible and ultraviolet Brillouin light-scattering spectroscopies.

Crystallization at the glass transition in supercooled thin films of methanol

The stability of an amorphous material depends on how fast and by what mechanism crystallization occurs. Based on crystallization rate measurements through optical reflectivity changes in supercooled methanol thin films, it is observed for the first time that there is a definitive and detectable change of the crystallization mechanism at the glass transition temperature T(g). For methanol glasses below T(g)=103.4 K, crystallization occurs as an interface controlled, one-dimension process at frozen-in embryo sites, while in the deep supercooled liquid phase above T(g) crystallization is diffusion controlled in two dimensions with a constant nucleation rate and an activation energy of 107.8(+/-4.7) kJ/mol.

The Widom line of supercooled water

Water can be supercooled to temperatures as low as−92 °C, the experimental crystal homogeneous nucleation temperatureTH at 2 kbar. Within the supercooled liquid phase its response functions show an anomalousincrease consistent with the presence of a liquid–liquid critical point located in a regioninaccessible to experiments on bulk water. Recent experiments on the dynamics ofconfined water show that a possible way to understand the properties of wateris to investigate the supercooled phase diagram in the vicinity of the Widomline (locus of maximum correlation length) that emanates from the hypothesizedliquid–liquid critical point. Here we explore the Widom line for a Hamiltonianmodel of water using an analytic approach, and discuss the plausibility of thehypothesized liquid–liquid critical point, as well as its possible consequences, on the basisof the assumptions of the model. The present analysis allows us (i) to find ananalytic expression for the spinodal line of the high-density liquid phase, withrespect to the low-density liquid phase, showing that this line becomes flat in theP–T phase diagram in the physical limit of a large number of available orientationsfor the hydrogen bonds, as recently seen in simulations and experiments (Xu et al 2005 Proc. Natl Acad. Sci. 102 16558); (ii) to find an estimate of the values forthe hypothesized liquid–liquid critical point coordinates that compare very wellwith Monte Carlo results; and (iii) to show how the Widom line can be locatedby studying the derivative of the probability of forming hydrogen bonds withlocal tetrahedral orientation which can be calculated analytically within thisapproach.

Molecular Dynamics Study of Glass-Forming Ability of Zr-Based Metallic Glasses

A new method to estimate the stability of supercooled liquid based on the temperature dependence of the free volume fraction, which is obtained by a molecular dynamics simulation with no empirical data was proposed. The molecular dynamics simulations for some Zr-based metallic glasses, Zr55Cu30Ni5Al10 ,Z r 67Ni33 and Zr67Cu33 in Zr-Cu-Ni-Al system were performed. The features of the first peaks in calculated radial density functions well correspond to the experimental results by XRD and EXAFS spectroscope. The free volume fractions at 0 K in the quenched amorphous, Fquenched, and in ‘‘fully relaxed’’ supercooled liquid states, Frelaxed, are evaluated by the fitting of the temperature vs freevolume-fraction curve obtained by a molecular dynamics simulation. The calculated normalized free volume fraction Nfree, defined as Fquenched=Frelaxed, shows similar tendency with other experimental Trg. criterion. The temperature dependence of the free volume fraction in a supercooled liquid state governs the quenched free volume in the amorphous phase, which shows that the local structures in supercooled liquid or liquid phases are especially important for the glass formation. [doi:10.2320/matertrans.MF200608]

A glance on the glass-transition phenomenon from the viewpoint of devitrification

The formation of a supercooled liquid region and devitrification behaviour of metallic glasses on heating are discussed in relation with the glass-transition phenomenon observed using differential scanning and isothermal calorimetries as well as X-ray diffraction and transmission electron microscopy (TEM). One of the most clear sequences of the glassy ↔ supercooled liquid phase transition is the change of the devitrification behaviour and the kinetics of the devitrification reaction in Al-based and some other alloys after the transition from the glassy to the supercooled liquid state. The significant variation in the devitrification behaviour and thermodynamic parameters indicate the difference between the glassy and the supercooled liquid phases.

Electron irradiation induced phase transformation of supercooled liquid and amorphous phases in Zr 66.7Cu 33.3 metallic glass

Electron-irradiation-induced phase transformations in supercooled liquid, amorphous and crystalline phases were investigated in Zr 66.7Cu 33.3(numbers indicate at.%) metallic glass. The supercooled liquid and amorphous phases were unstable under electron irradiation at and above 552 K: C11 b–Zr 2Cu crystalline phase was formed through electron irradiation induced crystallization. Electron-irradiation-induced crystal-to-supercooled liquid transition and crystal-to-amorphous transition in C11 b–Zr 2Cu crystalline phase did not occur at and above 552 K. Phase selection in electron irradiation induced crystallization was sensitive to the phase stability of crystalline phases against electron irradiation.

Structural relaxation of formic acid and its interaction with water and Xe at cryogenic temperatures

The glass–liquid transition of the amorphous HCOOH films and the reorganization of hydrogen-bonds of HCOOH during interactions with adsorbed D 2O and Xe have been investigated on the basis of temperature-programmed TOF-SIMS and TPD. On the as-deposited HCOOH film at 15 K, the physisorbed Xe atom permeates through pores and is trapped in the bulk during pore collapse upon heating. The hydrogen bonds of the HCOOH film are persistent up to 125 K as revealed from the interaction with the adsorbed D 2O molecules. The translational molecular diffusion commences at 125 K and dewetting of the HCOOH film follows at 150 K. The Xe atom incorporated in the bulk of the HCOOH film desorbs at 150 K concomitantly with dewetting of the film. These phenomena can be explained in terms of the glass-liquid transition of formic acid and the slow evolution of fluidity in the supercooled liquid phase.

Crystal nucleation in the one-component plasma

We have performed molecular dynamics simulations to study the kinetics of crystal nucleation in the one-component plasma. We have monitored nucleation in the supercooled liquid phase by following the time evolution of the size distribution of crystal nuclei formed during the phase transition. Although several observations are consistent with classical nucleation theory such as transient effects and the existence of a free-energy barrier to crystallization, we could not unambiguously identify a critical size for the crystal nuclei formed within the metastable phase.

Annealed high-density amorphous ice under pressure

The well-known expansion of water on cooling below 277 K is one of several peculiar properties that could signal a second critical point near 220 K and 0.1 GPa in pressure, deep in the supercooled liquid phase. Evidence for this would be a first-order transition line between two distinct supercooled liquids at temperatures below the critical point. As that lies below the minimum crystallization temperature, experimental tests have instead used low- and high-density amorphous ices—LDA and HDA—as proxies for the supercooled liquids. But numerous studies over the past decade have not yielded a clear consensus about the nature of the HDA/LDA transition. Here we identify a previously uncharacterized state of high-density amorphous ice obtained if HDA is annealed at pressures near 2 kbar. The transition between this annealed HDA and LDA is strikingly different from the behaviour found in earlier work, in a way that favours the two-liquid model.