WorldWideScience

Sample records for solvent-induced glass transition

  1. Gauge theory of glass transition

    International Nuclear Information System (INIS)

    Vasin, Mikhail

    2011-01-01

    A new analytical approach for the description of the glass transition in a frustrated system is suggested. The theory is based on the non-equilibrium dynamics technique, and takes into account the interaction of the local order field with the massive gauge field, which describes frustration-induced plastic deformation. The glass transition is regarded as a phase transition interrupted because of the premature critical slowing-down of one of the degrees of freedom caused by the frustrations. It is shown that freezing of the system appears when the correlation length and relaxation time of the gauge field diverge. The Vogel–Fulcher–Tammann relation for the transition kinetics and the critical exponent for the nonlinear susceptibility, 2.5∼ t correlation function dependence on time, and explains the boson peak appearance on this curve. In addition, the function of the glass transition temperature value with cooling rate is derived; this dependence fully conforms with known experimental data

  2. Strong-Superstrong Transition in Glass Transition of Metallic Glass

    International Nuclear Information System (INIS)

    Dan, Wang; Hong-Yan, Peng; Xiao-Yu, Xu; Bao-Ling, Chen; Chun-Lei, Wu; Min-Hua, Sun

    2010-01-01

    Dynamic fragility of bulk metallic glass (BMG) of Zr 64 Cu 16 Ni 10 Al 10 alloy is studied by three-point beam bending methods. The fragility parameter mfor Zr 64 Cu 16 Ni 10 Al 10 BMG is calculated to be 24.5 at high temperature, which means that the liquid is a 'strong' liquid, while to be 13.4 at low temperature which means that the liquid is a 'super-strong' liquid. The dynamical behavior of Zr 64 Cu 16 Ni 10 Al 10 BMG in the supercooled region undergoes a strong to super-strong transition. To our knowledge, it is the first time that a strong-to-superstrong transition is found in the metallic glass. Using small angle x-ray scattering experiments, we find that this transition is assumed to be related to a phase separation process in supercooled liquid. (condensed matter: structure, mechanical and thermal properties)

  3. Phase transitions and glass transition in a hyperquenched silica–alumina glass

    DEFF Research Database (Denmark)

    Zhang, Y.F.; Zhao, D.H.; Yue, Yuanzheng

    2017-01-01

    We investigate phase transitions, glass transition, and dynamic behavior in the hyperquenched 69SiO2–31Al2O3 (mol%) glass (SA glass). Upon reheating, the SA glass exhibits a series of thermal responses. Subsequent to the sub-Tg enthalpy release, the glass undergoes a large jump in isobaric heat...... capacity (ΔCp) during glass transition, implying the fragile nature of the SA glass. The mullite starts to form before the end of glass transition, indicating that the SA glass is extremely unstable against crystallization. After the mullite formation, the remaining glass phase exhibits an increased Tg...... and a suppressed ΔCp. The formation of cristobalite at 1553 K indicates the dominance of silica in the remaining glass matrix. The cristobalite gradually re-melts as the isothermal heat-treatment temperature is raised from 1823 to 1853 K, which is well below the melting point of cristobalite, while the amount...

  4. Spin-glass transition in disordered terbium

    International Nuclear Information System (INIS)

    Hauser, J.J.

    1985-01-01

    While crystalline Tb is a helix antiferromagnet with a Neel temperature of 229 K which becomes ferromagnetic at 222 K, disordered Tb exhibits a spin-glass transition. The spin-glass freezing temperature ranges from 183 to 53 K, the lowest temperatures corresponding to the greatest degree of atomic disorder. These experiments constitute the first evidence for an elemental spin-glass. (author)

  5. Mechanical failure and glass transition in metallic glasses

    International Nuclear Information System (INIS)

    Egami, T.

    2011-01-01

    Research highlights: → We review the recent results of molecular dynamics simulations on metallic glasses. → They show the equivalence of mechanical failure and glass transition. → We discuss the microscopic mechanism behind this equivalence. → We show that the density of defects in metallic glasses is as high as a quarter. → Our concepts about the defect state in glasses need to be changed. - Abstract: The current majority view on the phenomenon of mechanical failure in metallic glasses appears to be that it is caused by the activity of some structural defects, such as free-volumes or shear transformation zones, and the concentration of such defects is small, only of the order of 1%. However, the recent results compel us to revise this view. Through molecular dynamics simulation it has been shown that mechanical failure is the stress-induced glass transition. According to our theory the concentration of the liquid-like sites (defects) is well over 20% at the glass transition. We suggest that the defect concentration in metallic glasses is actually very high, and percolation of such defects causes atomic avalanche and mechanical failure. In this article we discuss the glass transition, mechanical failure and viscosity from such a point of view.

  6. Glass transition of soft colloids

    Science.gov (United States)

    Philippe, Adrian-Marie; Truzzolillo, Domenico; Galvan-Myoshi, Julian; Dieudonné-George, Philippe; Trappe, Véronique; Berthier, Ludovic; Cipelletti, Luca

    2018-04-01

    We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric and screened Coulomb interactions, respectively. In the supercooled regime, the structural relaxation time τα of both systems grows steeply with volume fraction, reminiscent of the behavior of colloidal hard spheres. Computer simulations confirm that the growth of τα on approaching the glass transition is independent of particle softness. By contrast, softness becomes relevant at very large packing fractions when the system falls out of equilibrium. In this nonequilibrium regime, τα depends surprisingly weakly on packing fraction, and time correlation functions exhibit a compressed exponential decay consistent with stress-driven relaxation. The transition to this novel regime coincides with the onset of an anomalous decrease in local order with increasing density typical of ultrasoft systems. We propose that these peculiar dynamics results from the combination of the nonequilibrium aging dynamics expected in the glassy state and the tendency of colloids interacting through soft potentials to refluidize at high packing fractions.

  7. Excitation Chains at the Glass Transition

    International Nuclear Information System (INIS)

    Langer, J. S.

    2006-01-01

    The excitation-chain theory of the glass transition, proposed in an earlier publication, predicts diverging, super-Arrhenius relaxation times and, via a similarly diverging length scale, suggests a way of understanding the relations between dynamic and thermodynamic properties of glass-forming liquids. I argue here that critically large excitation chains play a role roughly analogous to that played by critical clusters in the droplet model of vapor condensation. Unlike a first-order condensation point in a vapor, the glass transition is not a conventional phase transformation, and may not be a thermodynamic transition at all

  8. Poly(acrylamide) films at the solvent-induced glass transition: Adhesion, tribology, and the influence of crosslinking

    NARCIS (Netherlands)

    Li, A.; Ramakrishna, S.N.; Kooij, Ernst S.; Espinos-Marzal, R.M.; Spencer, N.D.

    2012-01-01

    Adhesive and nanotribological properties of end-grafted poly(acrylamide) (PAAm) films with various degrees of crosslinking, and in the presence of solvents over a broad spectrum of quality, were investigated by means of colloidal-probe atomic force microscopy. The solvent consisted of a mixture of

  9. Percolation and spin glass transition

    International Nuclear Information System (INIS)

    Sadiq, A.; Tahir-Kheli, R.A.; Wortis, M.; Bhatti, N.A.

    1980-10-01

    The behaviour of clusters of curved and normal plaquette particles in a bond random, +-J, Ising model is studied in finite square and triangular lattices. Computer results for the concentration of antiferromagnetic bonds when percolating clusters first appears are found to be close to those reported for the occurrence and disappearance of spin glass phases in these systems. (author)

  10. Glass Transition, Crystallization of Glass-Forming Melts, and Entropy

    Directory of Open Access Journals (Sweden)

    Jürn W. P. Schmelzer

    2018-02-01

    Full Text Available A critical analysis of possible (including some newly proposed definitions of the vitreous state and the glass transition is performed and an overview of kinetic criteria of vitrification is presented. On the basis of these results, recent controversial discussions on the possible values of the residual entropy of glasses are reviewed. Our conclusion is that the treatment of vitrification as a process of continuously breaking ergodicity with entropy loss and a residual entropy tending to zero in the limit of zero absolute temperature is in disagreement with the absolute majority of experimental and theoretical investigations of this process and the nature of the vitreous state. This conclusion is illustrated by model computations. In addition to the main conclusion derived from these computations, they are employed as a test for several suggestions concerning the behavior of thermodynamic coefficients in the glass transition range. Further, a brief review is given on possible ways of resolving the Kauzmann paradox and its implications with respect to the validity of the third law of thermodynamics. It is shown that neither in its primary formulations nor in its consequences does the Kauzmann paradox result in contradictions with any basic laws of nature. Such contradictions are excluded by either crystallization (not associated with a pseudospinodal as suggested by Kauzmann or a conventional (and not an ideal glass transition. Some further so far widely unexplored directions of research on the interplay between crystallization and glass transition are anticipated, in which entropy may play—beyond the topics widely discussed and reviewed here—a major role.

  11. The physics of the colloidal glass transition.

    Science.gov (United States)

    Hunter, Gary L; Weeks, Eric R

    2012-06-01

    As one increases the concentration of a colloidal suspension, the system exhibits a dramatic increase in viscosity. Beyond a certain concentration, the system is said to be a colloidal glass; structurally, the system resembles a liquid, yet motions within the suspension are slow enough that it can be considered essentially frozen. For several decades, colloids have served as a valuable model system for understanding the glass transition in molecular systems. The spatial and temporal scales involved allow these systems to be studied by a wide variety of experimental techniques. The focus of this review is the current state of understanding of the colloidal glass transition, with an emphasis on experimental observations. A brief introduction is given to important experimental techniques used to study the glass transition in colloids. We describe features of colloidal systems near and in glassy states, including increases in viscosity and relaxation times, dynamical heterogeneity and ageing, among others. We also compare and contrast the glass transition in colloids to that in molecular liquids. Other glassy systems are briefly discussed, as well as recently developed synthesis techniques that will keep these systems rich with interesting physics for years to come.

  12. The physics of the colloidal glass transition

    International Nuclear Information System (INIS)

    Hunter, Gary L; Weeks, Eric R

    2012-01-01

    As one increases the concentration of a colloidal suspension, the system exhibits a dramatic increase in viscosity. Beyond a certain concentration, the system is said to be a colloidal glass; structurally, the system resembles a liquid, yet motions within the suspension are slow enough that it can be considered essentially frozen. For several decades, colloids have served as a valuable model system for understanding the glass transition in molecular systems. The spatial and temporal scales involved allow these systems to be studied by a wide variety of experimental techniques. The focus of this review is the current state of understanding of the colloidal glass transition, with an emphasis on experimental observations. A brief introduction is given to important experimental techniques used to study the glass transition in colloids. We describe features of colloidal systems near and in glassy states, including increases in viscosity and relaxation times, dynamical heterogeneity and ageing, among others. We also compare and contrast the glass transition in colloids to that in molecular liquids. Other glassy systems are briefly discussed, as well as recently developed synthesis techniques that will keep these systems rich with interesting physics for years to come. (review article)

  13. Superconducting Metallic Glass Transition-Edge-Sensors

    Science.gov (United States)

    Hays, Charles C. (Inventor)

    2013-01-01

    A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

  14. Cell approach to glass transition

    International Nuclear Information System (INIS)

    Aste, Tomaso; Coniglio, Antonio

    2003-01-01

    We present a novel theoretical approach to understanding the complex dynamics of glass-forming liquids, granular packings and amorphous solids. This theory, which is an elaboration of the free volume and inherent structure approaches, allows one to retrieve the thermodynamical properties of these systems from studies of geometrical and topological properties of local, static configurations alone. When applied to hard-sphere systems, the present theory reproduces with a good quantitative agreement the equation of state for the crystalline and the disordered glassy phases. Moreover, we find that, as the density approaches a critical value close to the random close-packing density, the configurational entropy approaches zero and the large relaxation time diverges according to the Vogel-Fulcher behaviour, following also the Adam-Gibbs relation

  15. Water’s second glass transition

    Science.gov (United States)

    Amann-Winkel, Katrin; Gainaru, Catalin; Handle, Philip H.; Seidl, Markus; Nelson, Helge; Böhmer, Roland

    2013-01-01

    The glassy states of water are of common interest as the majority of H2O in space is in the glassy state and especially because a proper description of this phenomenon is considered to be the key to our understanding why liquid water shows exceptional properties, different from all other liquids. The occurrence of water’s calorimetric glass transition of low-density amorphous ice at 136 K has been discussed controversially for many years because its calorimetric signature is very feeble. Here, we report that high-density amorphous ice at ambient pressure shows a distinct calorimetric glass transitions at 116 K and present evidence that this second glass transition involves liquid-like translational mobility of water molecules. This “double Tg scenario” is related to the coexistence of two liquid phases. The calorimetric signature of the second glass transition is much less feeble, with a heat capacity increase at Tg,2 about five times as large as at Tg,1. By using broadband-dielectric spectroscopy we resolve loss peaks yielding relaxation times near 100 s at 126 K for low-density amorphous ice and at 110 K for high-density amorphous ice as signatures of these two distinct glass transitions. Temperature-dependent dielectric data and heating-rate–dependent calorimetric data allow us to construct the relaxation map for the two distinct phases of water and to extract fragility indices m = 14 for the low-density and m = 20–25 for the high-density liquid. Thus, low-density liquid is classified as the strongest of all liquids known (“superstrong”), and also high-density liquid is classified as a strong liquid. PMID:24101518

  16. Ideal glass transitions by random pinning

    Science.gov (United States)

    Cammarota, Chiara; Biroli, Giulio

    2012-01-01

    We study the effect of freezing the positions of a fraction c of particles from an equilibrium configuration of a supercooled liquid at a temperature T. We show that within the random first-order transition theory pinning particles leads to an ideal glass transition for a critical fraction c = cK(T) even for moderate supercooling; e.g., close to the Mode-Coupling transition temperature. First we derive the phase diagram in the T - c plane by mean field approximations. Then, by applying a real-space renormalization group method, we obtain the critical properties for |c - cK(T)| → 0, in particular the divergence of length and time scales, which are dominated by two zero-temperature fixed points. We also show that for c = cK(T) the typical distance between frozen particles is related to the static point-to-set length scale of the unconstrained liquid. We discuss what are the main differences when particles are frozen in other geometries and not from an equilibrium configuration. Finally, we explain why the glass transition induced by freezing particles provides a new and very promising avenue of research to probe the glassy state and ascertain, or disprove, the validity of the theories of the glass transition. PMID:22623524

  17. Vortex-glass transition in three dimensions

    International Nuclear Information System (INIS)

    Reger, J.D.; Tokuyasu, T.A.; Young, A.P.; Fisher, M.P.A.

    1991-01-01

    We investigate the possibility of a vortex-glass transition in a disordered type-II superconductor in a magnetic field in three dimensions by numerical studies of a simplified model. Monte Carlo simulations at finite temperature and domain-wall renormalization-group calculations at T=0 indicate that d=3 is just above the lower critical dimension d l , though the possibility that d l =3 cannot be definitely ruled out. A comparison is made with XY and Ising spin glasses. The (effective) correlation-length exponent ν and dynamical exponent z are in fairly good agreement with experiment

  18. Chiral-glass transition and replica symmetry breaking of a three-dimensional Heisenberg spin glass

    OpenAIRE

    Hukushima, K.; Kawamura, H.

    2000-01-01

    Extensive equilibrium Monte Carlo simulations are performed for a three-dimensional Heisenberg spin glass with the nearest-neighbor Gaussian coupling to investigate its spin-glass and chiral-glass orderings. The occurrence of a finite-temperature chiral-glass transition without the conventional spin-glass order is established. Critical exponents characterizing the transition are different from those of the standard Ising spin glass. The calculated overlap distribution suggests the appearance ...

  19. Dielectric determination of the glass transition temperature (T sub g)

    Science.gov (United States)

    Ries, Heidi R.

    1990-01-01

    The objective is to determine the glass transition temperature of a polymer using a dielectric dissipation technique. A peak in the dissipation factor versus temperature curve is expected near the glass transition temperature T sub g. It should be noted that the glass transition is gradual rather than abrupt, so that the glass transition temperature T sub g is not clearly identifiable. In this case, the glass transition temperature is defined to be the temperature at the intersection point of the tangent lines to the dissipation factor versus temperature curve above and below the transition region, as illustrated.

  20. Glass transition in soft-sphere dispersions

    International Nuclear Information System (INIS)

    RamIrez-Gonzalez, P E; Medina-Noyola, M

    2009-01-01

    The concept of dynamic equivalence among mono-disperse soft-sphere fluids is employed in the framework of the self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics to calculate the ideal glass transition phase diagram of model soft-sphere colloidal dispersions in the softness-concentration state space. The slow dynamics predicted by this theory near the glass transition is compared with available experimental data for the decay of the intermediate scattering function of colloidal dispersions of soft-microgel particles. Increasing deviations from this simple scheme occur for increasingly softer potentials, and this is studied here using the Rogers-Young static structure factor of the soft-sphere systems as the input of the SCGLE theory, without assuming a priori the validity of the equivalence principle above.

  1. Microstructure and Rheology near an Attractive Colloidal Glass Transition

    International Nuclear Information System (INIS)

    Narayanan, T.; Sztucki, M.; Belina, G.; Pignon, F.

    2006-01-01

    Microstructure and rheological properties of a thermally reversible short-ranged attractive colloidal system are studied in the vicinity of the attractive glass transition line. At high volume fractions, the static structure factor changes very little but the low frequency shear moduli varies over several orders of magnitude across the transition. From the frequency dependence of shear moduli, fluid-attractive glass and repulsive glass-attractive glass transitions are identified

  2. Glass/Jamming Transition in Colloidal Aggregation

    Science.gov (United States)

    Segre, Philip N.; Prasad, Vikram; Weitz, David A.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have studied colloidal aggregation in a model colloid plus polymer system with short-range attractive interactions. By varying the colloid concentration and the strength of the attraction, we explored regions where the equilibrium phase is expected to consist of colloidal crystallites in coexistance with colloidal gas (i.e. monomers). This occurs for moderate values of the potential depth, U approximately equal to 2-5 kT. Crystallization was not always observed. Rather, over an extended sub-region two new metastable phases appear, one fluid-like and one solid-like. These were examined in detail with light scattering and microscopy techniques. Both phases consist of a near uniform distribution of small irregular shaped clusters of colloidal particles. The dynamical and structural characteristics of the ergodic-nonergodic transition between the two phases share much in common with the colloidal hard sphere glass transition.

  3. Glass Transition Temperature- and Specific Volume- Composition Models for Tellurite Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Vienna, John D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-09-01

    This report provides models for predicting composition-properties for tellurite glasses, namely specific gravity and glass transition temperature. Included are the partial specific coefficients for each model, the component validity ranges, and model fit parameters.

  4. A simple method for tuning the glass transition process in inorganic phosphate glasses

    OpenAIRE

    Fulchiron, Ren?; Belyamani, Imane; Otaigbe, Joshua U.; Bounor-Legar?, V?ronique

    2015-01-01

    The physical modification of glass transition temperature (Tg ) and properties of materials via blending is a common practice in industry and academia and has a large economic advantage. In this context, simple production of hitherto unattainable new inorganic glass blends from already existing glass compositions via blending raises much hope with the potential to provide new glasses with new and improved properties, that cannot be achieved with classical glass synthesis, for a plethora of ap...

  5. Numerical study of the glass-glass transition in short-ranged attractive colloids

    International Nuclear Information System (INIS)

    Zaccarelli, Emanuela; Sciortino, Francesco; Tartaglia, Piero

    2004-01-01

    We report extensive numerical simulations in the glass region for a simple model of short-ranged attractive colloids, the square well model. We investigate the behaviour of the density autocorrelation function and of the static structure factor in the region of temperatures and packing fractions where a glass-glass transition is expected according to theoretical predictions. We strengthen our observations by studying both waiting time and history dependence of the numerical results. We provide evidence supporting the possibility that activated bond-breaking processes destabilize the attractive glass, preventing the full observation of a sharp glass-glass kinetic transition

  6. Glass transition of anhydrous starch by fast scanning calorimetry.

    Science.gov (United States)

    Monnier, Xavier; Maigret, Jean-Eudes; Lourdin, Denis; Saiter, Allisson

    2017-10-01

    By means of fast scanning calorimetry, the glass transition of anhydrous amorphous starch has been measured. With a scanning rate of 2000Ks -1 , thermal degradation of starch prior to the glass transition has been inhibited. To certify the glass transition measurement, structural relaxation of the glassy state has been investigated through physical aging as well as the concept of limiting fictive temperature. In both cases, characteristic enthalpy recovery peaks related to the structural relaxation of the glass have been observed. Thermal lag corrections based on the comparison of glass transition temperatures measured by means of differential and fast scanning calorimetry have been proposed. The complementary investigations give an anhydrous amorphous starch glass transition temperature of 312±7°C. This estimation correlates with previous extrapolation performed on hydrated starches. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Glass transitions in lubricants - Its relation to elastohydrodynamic lubrication /EHD/

    Science.gov (United States)

    Alsaad, M.; Bair, S.; Sanborn, D. M.; Winer, W. O.

    1977-01-01

    A preliminary investigation into the possible role of glass transition and glassy state behavior of lubricants in EHD contacts is reported. Measurements of the glass transition of lubricants as a function of pressure by two methods are presented along with a discussion indicating possible implications of the results to EHD lubrication.

  8. Modern aspects of the kinetic theory of glass transition

    International Nuclear Information System (INIS)

    Tropin, T V; Aksenov, V L; Schmelzer, J W

    2016-01-01

    This paper reviews glass transition kinetics models that are developed to describe the formation of structural (for example, covalent and metallic) glasses, as well as to account for the transition of a polymer to a solid glassy state. As the two approaches most frequently used over the last decade to model the glass transition, the Tool–Narayanaswamy–Moynihan model and the Adam–Gibbs theory of glass transition are described together with examples of their applications. Also discussed are entropy-based approaches that rely on irreversible thermodynamics methods originated in the work of De Donder, Mandelstam, and Leontovich. The actual problems that arise in applying these methods and the prospects of their development are discussed. A brief overview of statistical glass transition models is given, including the mode-coupling and energy-landscape theories. (reviews of topical problems)

  9. Echoes of the Glass Transition in Athermal Soft Spheres.

    Science.gov (United States)

    Morse, Peter K; Corwin, Eric I

    2017-09-15

    Recent theoretical advances have led to the creation of a unified phase diagram for the thermal glass and athermal jamming transitions. This diagram makes clear that, while related, the mode-coupling-or dynamic-glass transition is distinct from the jamming transition, occurring at a finite temperature and significantly lower density than the jamming transition. Nonetheless, we demonstrate a prejamming transition in athermal frictionless spheres which occurs at the same density as the mode-coupling transition and is marked by percolating clusters of locally rigid particles. At this density in both the thermal and athermal systems, individual motions of an extensive number of particles become constrained, such that only collective motion is possible. This transition, which is well below jamming, exactly matches the definition of collective behavior at the dynamical transition of glasses. Thus, we reveal that the genesis of rigidity in both thermal and athermal systems is governed by the same underlying topological transition in their shared configuration space.

  10. Predicting the glass transition temperature of bioactive glasses from their molecular chemical composition.

    Science.gov (United States)

    Hill, Robert G; Brauer, Delia S

    2011-10-01

    A recently published paper (M.D. O'Donnell, Acta Biomaterialia 7 (2011) 2264-2269) suggests that it is possible to correlate the glass transition temperature (T(g)) of bioactive glasses with their molar composition, based on iterative least-squares fitting of published T(g) data. However, we show that the glass structure is an important parameter in determining T(g). Phase separation, local structural effects and components (intermediate oxides) which can switch their structural role in the glass network need to be taken into consideration, as they are likely to influence the glass transition temperature of bioactive glasses. Although the model suggested by O'Donnell works reasonably well for glasses within the composition range presented, it is oversimplified and fails for glasses outside certain compositional boundaries. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  11. Does Brillouin light scattering probe the primary glass transition process at temperatures well above glass transition?

    Science.gov (United States)

    Voudouris, P; Gomopoulos, N; Le Grand, A; Hadjichristidis, N; Floudas, G; Ediger, M D; Fytas, G

    2010-02-21

    The primary alpha-relaxation time (tau(alpha)) for molecular and polymeric glass formers probed by dielectric spectroscopy and two light scattering techniques (depolarized light scattering and photon correlation spectroscopy) relates to the decay of the torsional autocorrelation function computed by molecular dynamics simulation. It is well known that Brillouin light scattering spectroscopy (BLS) operating in gigahertz frequencies probes a fast (10-100 ps) relaxation of the longitudinal modulus M*. The characteristic relaxation time, irrespective of the fitting procedure, is faster than the alpha-relaxation which obeys the non-Arrhenius Vogel-Fulcher-Tammann equation. Albeit, this has been noticed, it remains a puzzling finding in glass forming systems. The available knowledge is based only on temperature dependent BLS experiments performed, however, at a single wave vector (frequency). Using a new BLS spectrometer, we studied the phonon dispersion at gigahertz frequencies in molecular [o-terphenyl (OTP)] and polymeric [polyisoprene (PI) and polypropylene (PP)] glass formers. We found that the hypersonic dispersion does relate to the glass transition dynamics but the disparity between the BLS-relaxation times and tau(alpha) is system dependent. In PI and PP, the former is more than one order of magnitude faster than tau(alpha), whereas the two relaxation times become comparable in the case of OTP. The difference between the two relaxation times appears to relate to the "breadth" of the relaxation time distribution function. In OTP the alpha-relaxation process assumes a virtually single exponential decay at high temperatures well above the glass transition temperature, in clear contrast with the case of the amorphous bulk polymers.

  12. Relationship between thermal expansion coefficient and glass transition temperature in metallic glasses

    International Nuclear Information System (INIS)

    Kato, H.; Chen, H.-S.; Inoue, A.

    2008-01-01

    The thermal expansion coefficients of 13 metallic glasses were measured using a thermo-mechanical analyser. A unique correlation was found between the linear thermal expansion coefficient and the glass transition temperature-their product is nearly constant ∼8.24 x 10 -3 . If one assumes the Debye expression for thermal activation, the total linear thermal expansion up to glass transition temperature (T g ) is reduced to 6 x 10 -3 , nearly 25% of that at the fusion of pure metals

  13. Isotope effect in glass-transition temperature and ionic conductivity of lithium-borate glasses

    International Nuclear Information System (INIS)

    Nagasaki, Takanori; Morishima, Ryuta; Matsui, Tsuneo

    2002-01-01

    The glass-transition temperature and the electrical conductivity of lithium borate (0.33Li 2 O-0.67B 2 O 3 ) glasses with various isotopic compositions were determined by differential thermal analysis and by impedance spectroscopy, respectively. The obtained glass-transition temperature as well as the vibrational frequency of B-O network structure was independent of lithium isotopic composition. This result indicates that lithium ions, which exist as network modifier, only weakly interact with B-O network structure. In addition, the glass-transition temperature increased with 10 B content although the reason has not been understood. The electrical conductivity, on the other hand, increased with 6 Li content. The ratio of the conductivity of 6 Li glass to that of 7 Li glass was found to be 2, being larger than the value (7/6) 1/2 calculated with the simple classical diffusion theory. This strong mass dependence could be explained by the dynamic structure model, which assumes local structural relaxation even far below the glass-transition temperature. Besides, the conductivity appeared to increase with the glass-transition temperature. Possible correlations between the glass-transition temperature and the electrical conductivity were discussed. (author)

  14. Polymer brushes: a controllable system with adjustable glass transition temperature of fragile glass formers.

    Science.gov (United States)

    Xie, Shi-Jie; Qian, Hu-Jun; Lu, Zhong-Yuan

    2014-01-28

    We present results of molecular dynamics simulations for coarse-grained polymer brushes in a wide temperature range to investigate the factors that affect the glass transition in these systems. We focus on the influences of free surface, polymer-substrate interaction strength, grafting density, and chain length not only on the change of glass transition temperature Tg, but also the fragility D of the glass former. It is found that the confinement can enhance the dependence of the Tg on the cooling rate as compared to the bulk melt. Our layer-resolved analysis demonstrates that it is possible to control the glass transition temperature Tg of polymer brushes by tuning the polymer-substrate interaction strength, the grafting density, and the chain length. Moreover, we find quantitative differences in the influence range of the substrate and the free surface on the density and dynamics. This stresses the importance of long range cooperative motion in glass formers near the glass transition temperature. Furthermore, the string-like cooperative motion analysis demonstrates that there exists a close relation among glass transition temperature Tg, fragility D, and string length ⟨S⟩. The polymer brushes that possess larger string length ⟨S⟩ tend to have relatively higher Tg and smaller D. Our results suggest that confining a fragile glass former through forming polymer brushes changes not only the glass transition temperature Tg, but also the very nature of relaxation process.

  15. The glass transition in high-density amorphous ice.

    Science.gov (United States)

    Loerting, Thomas; Fuentes-Landete, Violeta; Handle, Philip H; Seidl, Markus; Amann-Winkel, Katrin; Gainaru, Catalin; Böhmer, Roland

    2015-01-01

    There has been a long controversy regarding the glass transition in low-density amorphous ice (LDA). The central question is whether or not it transforms to an ultraviscous liquid state above 136 K at ambient pressure prior to crystallization. Currently, the most widespread interpretation of the experimental findings is in terms of a transformation to a superstrong liquid above 136 K. In the last decade some work has also been devoted to the study of the glass transition in high-density amorphous ice (HDA) which is in the focus of the present review. At ambient pressure HDA is metastable against both ice I and LDA, whereas at > 0.2 GPa HDA is no longer metastable against LDA, but merely against high-pressure forms of crystalline ice. The first experimental observation interpreted as the glass transition of HDA was made using in situ methods by Mishima, who reported a glass transition temperature T g of 160 K at 0.40 GPa. Soon thereafter Andersson and Inaba reported a much lower glass transition temperature of 122 K at 1.0 GPa. Based on the pressure dependence of HDA's T g measured in Innsbruck, we suggest that they were in fact probing the distinct glass transition of very high-density amorphous ice (VHDA). Very recently the glass transition in HDA was also observed at ambient pressure at 116 K. That is, LDA and HDA show two distinct glass transitions, clearly separated by about 20 K at ambient pressure. In summary, this suggests that three glass transition lines can be defined in the p-T plane for LDA, HDA, and VHDA.

  16. Light-scattering study of the glass transition in lubricants

    Science.gov (United States)

    Alsaad, M. A.; Winer, W. O.; Medina, F. D.; Oshea, D. C.

    1977-01-01

    The sound velocity of four lubricants has been measured as a function of temperature and pressure using Brillouin scattering. A change in slope of the velocity as a function of temperature or pressure allowed the determination of the glass transition temperature and pressure. The glass transition data were used to construct a phase diagram for each lubricant. The data indicate that the glass transition temperature increased with pressure at a rate which ranged from 120 to 200 C/GPa. The maximum pressure attained was 0.69 GPa and the temperature range was from 25 to 100 C.

  17. Glass-Glass Transitions by Means of an Acceptor-Donor Percolating Electric-Dipole Network

    Science.gov (United States)

    Zhang, Le; Lou, Xiaojie; Wang, Dong; Zhou, Yan; Yang, Yang; Kuball, Martin; Carpenter, Michael A.; Ren, Xiaobing

    2017-11-01

    We report the ferroelectric glass-glass transitions in KN (K+/Nb5 +) -doped BaTiO3 ferroelectric ceramics, which have been proved by x-ray diffraction profile and Raman spectra data. The formation of glass-glass transitions can be attributed to the existence of cubic (C )-tetragonal (T )-orthorhombic (O )-rhombohedral (R ) ferroelectric transitions in short-range order. These abnormal glass-glass transitions can perform very small thermal hysteresis (approximately 1.0 K ) with a large dielectric constant (approximately 3000), small remanent polarization Pr , and relative high maximum polarization Pm remaining over a wide temperature range (220-350 K) under an electrical stimulus, indicating the potential applications in dielectric recoverable energy-storage devices with high thermal reliability. Further phase field simulations suggest that these glass-glass transitions are induced by the formation of a percolating electric defect-dipole network (PEDN). This proper PEDN breaks the long-range ordered ferroelectric domain pattern and results in the local phase transitions at the nanoscale. Our work may further stimulate the fundamental physical theory and accelerate the development of dielectric energy-storing devices.

  18. Liquid-liquid phase transition and glass transition in a monoatomic model system.

    Science.gov (United States)

    Xu, Limei; Buldyrev, Sergey V; Giovambattista, Nicolas; Stanley, H Eugene

    2010-01-01

    We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.

  19. Spherical 2+p spin-glass model: An exactly solvable model for glass to spin-glass transition

    International Nuclear Information System (INIS)

    Crisanti, A.; Leuzzi, L.

    2004-01-01

    We present the full phase diagram of the spherical 2+p spin-glass model with p≥4. The main outcome is the presence of a phase with both properties of full replica symmetry breaking phases of discrete models, e.g., the Sherrington-Kirkpatrick model, and those of one replica symmetry breaking. This phase has a finite complexity which leads to different dynamic and static properties. The phase diagram is rich enough to allow the study of different kinds of glass to spin glass and spin glass to spin glass phase transitions

  20. Citrate increases glass transition temperature of vitrified sucrose preparations

    NARCIS (Netherlands)

    Kets, E.P.W.; Lipelaar, P.J.; Hoekstra, F.A.; Vromans, H.

    2004-01-01

    The aim of this study was to investigate the effect of sodium citrate on the properties of dried amorphous sucrose glasses. Addition of sodium citrate to a sucrose solution followed by freeze-drying or convective drying resulted in a glass transition temperature (T-g) that was higher than the

  1. Thermodynamic consequences of the kinetic nature of the glass transition

    Science.gov (United States)

    Koperwas, Kajetan; Grzybowski, Andrzej; Tripathy, Satya N.; Masiewicz, Elzbieta; Paluch, Marian

    2015-01-01

    In this paper, we consider the glass transition as a kinetic process and establish one universal equation for the pressure coefficient of the glass transition temperature, dTg/dp, which is a thermodynamic characteristic of this process. Our findings challenge the common previous expectations concerning key characteristics of the transformation from the liquid to the glassy state, because it suggests that without employing an additional condition, met in the glass transition, derivation of the two independent equations for dTg/dp is not possible. Hence, the relation among the thermodynamic coefficients, which could be equivalent to the well-known Prigogine-Defay ratio for the process under consideration, cannot be obtained. Besides, by comparing the predictions of our universal equation for dTg/dp and Ehrenfest equations, we find the aforementioned supplementary restriction, which must be met to use the Prigogine-Defay ratio for the glass transition. PMID:26657017

  2. An Overview of the Glass Transition Temperature of Synthetic Polymers.

    Science.gov (United States)

    Beck, Keith R.; And Others

    1984-01-01

    Presents an overview of the glass-to-rubber transition, what it is, why it is important, and the major factors that influence it. Indicates that this information should be incorporated into chemistry curricula. (JN)

  3. Glass transition and thermal expansivity of polystyrene thin films

    International Nuclear Information System (INIS)

    Inoue, R.; Kanaya, T.; Miyazaki, T.; Nishida, K.; Tsukushi, I.; Shibata, K.

    2006-01-01

    We have studied glass transition temperature and thermal expansivity of polystyrene thin films supported on silicon substrate using X-ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we have found that the reported apparent negative expansivity of polymer thin films is caused by unrelaxed structure due to insufficient annealing. Using well-annealed films, we have evaluated glass transition temperature T g and thermal expansivity as a function of film thickness. The glass transition temperature decreases with film thickness and is constant below about 10 nm, suggesting the surface glass transition temperature of 355 K, which is lower than that in bulk. We have also found that the thermal expansivity in the glassy state decreases with film thickness even after annealing. The decrease has been attributed to hardening of harmonic force constant arising from chain confinement in a thin film. This idea has been confirmed in the inelastic neutron scattering measurements

  4. Glass transition and thermal expansivity of polystyrene thin films

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, R. [Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011 (Japan); Kanaya, T. [Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011 (Japan)]. E-mail: kanaya@scl.kyoto-u.ac.jp; Miyazaki, T. [Nitto Denko Corporation, 1-1-2 Shimohozumi, Ibaraki, Osaka-fu 567-8680 (Japan); Nishida, K. [Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011 (Japan); Tsukushi, I. [Chiba Institute of Technology, Narashino, Chiba-ken 275-0023 (Japan); Shibata, K. [Japan Atomic Energy Research Institute, Tokai, Ibaraki-ken 319-1195 (Japan)

    2006-12-20

    We have studied glass transition temperature and thermal expansivity of polystyrene thin films supported on silicon substrate using X-ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we have found that the reported apparent negative expansivity of polymer thin films is caused by unrelaxed structure due to insufficient annealing. Using well-annealed films, we have evaluated glass transition temperature T {sub g} and thermal expansivity as a function of film thickness. The glass transition temperature decreases with film thickness and is constant below about 10 nm, suggesting the surface glass transition temperature of 355 K, which is lower than that in bulk. We have also found that the thermal expansivity in the glassy state decreases with film thickness even after annealing. The decrease has been attributed to hardening of harmonic force constant arising from chain confinement in a thin film. This idea has been confirmed in the inelastic neutron scattering measurements.

  5. Ideal glass transitions in thin films: An energy landscape perspective

    OpenAIRE

    Truskett, Thomas M.; Ganesan, Venkat

    2003-01-01

    We introduce a mean-field model for the potential energy landscape of a thin fluid film confined between parallel substrates. The model predicts how the number of accessible basins on the energy landscape and, consequently, the film's ideal glass transition temperature depend on bulk pressure, film thickness, and the strength of the fluid-fluid and fluid-substrate interactions. The predictions are in qualitative agreement with the experimental trends for the kinetic glass transition temperatu...

  6. Investigation of low glass transition temperature on COTS PEMs reliability

    Science.gov (United States)

    Sandor, M.; Agarwal, S.

    2002-01-01

    Many factors influence PEM component reliability.One of the factors that can affect PEM performance and reliability is the glass transition temperature (Tg) and the coefficient of thermal expansion (CTE) of the encapsulant or underfill. JPL/NASA is investigating how the Tg and CTE for PEMs affect device reliability under different temperature and aging conditions. Other issues with Tg are also being investigated. Some preliminary data will be presented on glass transition temperature test results conducted at JPL.

  7. Glass heat capacity and its abrupt change in glass transition region

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Smedskjær, Morten Mattrup; Mauro, John C.

    cover a large range of glass formers from metallic to non-metallic glasses. To conduct this study we convert the units of all the Cp data from J/mol K and J/g K to J/g-atom K. This study will provide insight into the correlations among chemical bonding, microstructure structure, liquid fragility, glass......Glass transition (GT) has been a fascinating, but challenging subject in the condensed matter science over decades. Despite progress in understanding GT, many crucial problems still need to be clarified. One of the problems deals with the microscopic origin of abrupt change of heat capacity (Cp......) around glass transition. Here we study this problem through two approaches. First, we analyze the Cp change with temperature on homologous series of glass formers (i.e., with regular compositional substitution). Second, we do the same on non-homologous systems (e.g. without regular compositional...

  8. [Glass transition of Chinese medicine extract powder and its application].

    Science.gov (United States)

    Luo, Xiao-Jian; Liu, Hui; Liang, Hong-Bo; Xiong, Lei; Rao, Xiao-Yong; Xie, Yin; He, Yan

    2017-01-01

    Glass transition theory is an important theory in polymer science, which is used to characterize the physical properties. It refers to the transition of amorphous polymer from the glassy state to the rubber state due to heating or the transition from rubber state to glassy state due to cooling. In this paper, the glassy state and glass transition of food and the similar relationship between the composition of Chinese medicine extract powder and food ingredients were described; the determination method for glass transition temperature (Tg) of Chinese medicine extract powder was established and its main influencing factors were analyzed. Meanwhile, the problems in drying process, granulation process and Chinese medicine extract powder and solid preparation storage were analyzed and investigated based on Tg, and then the control strategy was put forward to provide guidance for the research and production of Chinese medicine solid preparation. Copyright© by the Chinese Pharmaceutical Association.

  9. Effect of particle size on the glass transition.

    Science.gov (United States)

    Larsen, Ryan J; Zukoski, Charles F

    2011-05-01

    The glass transition temperature of a broad class of molecules is shown to depend on molecular size. This dependency results from the size dependence of the pair potential. A generalized equation of state is used to estimate how the volume fraction at the glass transition depends on the size of the molecule, for rigid molecule glass-formers. The model shows that at a given pressure and temperature there is a size-induced glass transition: For molecules larger than a critical size, the volume fraction required to support the effective pressure due to particle attractions is above that which characterizes the glassy state. This observation establishes the boundary between nanoparticles, which exist in liquid form only as dispersions in low molecular weight solvents and large molecules which form liquids that have viscosities below those characterized by the glassy state.

  10. Brittle to ductile transition in densified silica glass.

    Science.gov (United States)

    Yuan, Fenglin; Huang, Liping

    2014-05-22

    Current understanding of the brittleness of glass is limited by our poor understanding and control over the microscopic structure. In this study, we used a pressure quenching route to tune the structure of silica glass in a controllable manner, and observed a systematic increase in ductility in samples quenched under increasingly higher pressure. The brittle to ductile transition in densified silica glass can be attributed to the critical role of 5-fold Si coordination defects (bonded to 5 O neighbors) in facilitating shear deformation and in dissipating energy by converting back to the 4-fold coordination state during deformation. As an archetypal glass former and one of the most abundant minerals in the Earth's crest, a fundamental understanding of the microscopic structure underpinning the ductility of silica glass will not only pave the way toward rational design of strong glasses, but also advance our knowledge of the geological processes in the Earth's interior.

  11. Glass-like and Verwey transitions in magnetite in details

    Czech Academy of Sciences Publication Activity Database

    Janů, Zdeněk; Hadač, J.; Švindrych, Z.

    2007-01-01

    Roč. 310, - (2007), e203-e205 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z10100520 Keywords : metal-insulator transition s and other electronic transition s * spin glass es and other random magnets * dynamic properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.704, year: 2007

  12. Comment on 'Spherical 2+p spin-glass model: An analytically solvable model with a glass-to-glass transition'

    International Nuclear Information System (INIS)

    Krakoviack, V.

    2007-01-01

    Guided by old results on simple mode-coupling models displaying glass-glass transitions, we demonstrate, through a crude analysis of the solution with one step of replica symmetry breaking (1RSB) derived by Crisanti and Leuzzi for the spherical s+p mean-field spin glass [Phys. Rev. B 73, 014412 (2006)], that the phase behavior of these systems is not yet fully understood when s and p are well separated. First, there seems to be a possibility of glass-glass transition scenarios in these systems. Second, we find clear indications that the 1RSB solution cannot be correct in the full glassy phase. Therefore, while the proposed analysis is clearly naive and probably inexact, it definitely calls for a reassessment of the physics of these systems, with the promise of potentially interesting developments in the theory of disordered and complex systems

  13. Photoacoustic investigation of glass transition in AsxTe1-x glasses

    International Nuclear Information System (INIS)

    Madhusoodanan, K.N.; Nandakumar, K.; Philip, J.; Titus, S.S.K.; Asokan, S.; Gopal, E.S.R.

    1989-01-01

    Photoacoustic (Pa) technique is used to study glass transition and temperature dependence of thermal diffusivity in As x Te 1-x glasses with 0.25 ≤ x ≤ 0.60. PA amplitude goes through a minimum and the phase shows a maximum at glass transition temperature T g . The variation of thermal diffusivity with temperature shows sharp decrease near T g . The variation of thermal diffusivity with composition shows maximum at x = 0.40 for all temperatures T ≤ T g . (author)

  14. Communication: Glass transition and melting lines of an ionic liquid

    Science.gov (United States)

    Lima, Thamires A.; Faria, Luiz F. O.; Paschoal, Vitor H.; Ribeiro, Mauro C. C.

    2018-05-01

    The phase diagram of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesufonyl)imide, [Pyrr1,4][NTf2], was explored by synchroton X-ray diffraction and Raman scattering measurements as a function of temperature and pressure. Glass transition Tg(p) and melting Tm(p) temperatures were obtained from atmospheric pressure up to ca. 2.0 GPa. We found that both the Tg(p) and Tm(p) curves follow essentially the same pressure dependence. The similarity of pressure coefficients, dTg/dp ≈ dTm/dp, is explained within the non-equilibrium thermodynamics approach for the glass transition by assuming that one of the Ehrenfest equations is appropriated for Tg(p), whereas Tm(p) follows the Clausius-Clapeyron equation valid for the first-order transitions. The results highlight that ionic liquids are excellent model systems to address fundamental questions related to the glass transition.

  15. Glass Transitions in a Monatomic Liquid with Two Glassy States

    Science.gov (United States)

    Gordon, Andrew; Giovambattista, Nicolas

    2014-04-01

    We perform out-of-equilibrium molecular dynamics simulations of a monatomic liquid that exhibits liquid and glass polymorphism, with two distinct glasses, low- (LDA) and high-density (HDA) amorphous solids. By performing isobaric heating simulations of LDA and HDA at different pressures, we determine (a) the glass transition temperature of LDA and HDA, TgLDA(P) and TgHDA(P), as well as (b) the corresponding glass-glass transformation temperatures, TLDA-HDA(P) and THDA-LDA(P). It is found that TgLDA(P) is anomalous; i.e., it decreases with increasing pressure, while TgHDA(P) increases with increasing pressure. Interestingly, the TgLDA(P) and TLDA-HDA(P) loci, as well as the TgHDA(P) and THDA-LDA(P) loci, constitute smooth single lines in the P -T plane, suggesting that heating-induced glass-glass and glass transitions are related. We discuss the present results in the context of water experiments and simulations.

  16. Models of agglomeration and glass transition

    CERN Document Server

    Kerner, Richard

    2007-01-01

    This book is for any physicist interested in new vistas in the domain of non-crystalline condensed matter, aperiodic and quasi-crystalline networks and especially glass physics and chemistry. Students with an elementary background in thermodynamics and statistical physics will find the book accessible. The physics of glasses is extensively covered, focusing on their thermal and mechanical properties, as well as various models leading to the formation of the glassy states of matter from overcooled liquids. The models of agglomeration and growth are also applied to describe the formation of quasicrystals, fullerenes and, in biology, to describe virus assembly pathways.

  17. TOPEM DSC study of glass transition region of polyurethane cationomers

    International Nuclear Information System (INIS)

    Pielichowska, Kinga; Król, Piotr; Król, Bożena; Pagacz, Joanna

    2012-01-01

    Highlights: ► TOPEM DSC method was employed to investigate the glass transition (T g ) region of fluorinated polyurethane cationomers. ► Introduction of fluorine compounds significantly changes thermal behaviour of cationomers in the T g region of hard segments. ► Introduction of fluorine compound leads to changes of the slope in activation diagram of glass transition. - Abstract: In this paper TOPEM DSC method was employed to investigate the glass transition region of fluorinated polyurethane cationomers. Fluorinated polyurethane cationomers have been synthesised in the reaction of MDI with poly(ethylene glycol) (600) and butane1,4-diol or N-methyl- or N-butyldiethanolamine and 2,2,3,3-tetrafluoro-1,4-butanediol. Better rigidity was found for generally amorphous cationomer coats. It was found that introduction of fluorine compound changes thermal behaviour of polyurethane cationomers as well as leads to changes in the slope in activation diagram profiles of glass transition in comparison to polyuretahene cationomer without fluorine compound. Application of TOPEM DSC allows to obtain more information concerning frequency dependence of glass transition region and thermodynamical stability of polyurethane structures.

  18. The liquid-glass-jamming transition in disordered ionic nanoemulsions.

    Science.gov (United States)

    Braibanti, Marco; Kim, Ha Seong; Şenbil, Nesrin; Pagenkopp, Matthew J; Mason, Thomas G; Scheffold, Frank

    2017-11-08

    In quenched disordered out-of-equilibrium many-body colloidal systems, there are important distinctions between the glass transition, which is related to the onset of nonergodicity and loss of low-frequency relaxations caused by crowding, and the jamming transition, which is related to the dramatic increase in elasticity of the system caused by the deformation of constituent objects. For softer repulsive interaction potentials, these two transitions become increasingly smeared together, so measuring a clear distinction between where the glass ends and where jamming begins becomes very difficult or even impossible. Here, we investigate droplet dynamics in concentrated silicone oil-in-water nanoemulsions using light scattering. For zero or low NaCl electrolyte concentrations, interfacial repulsions are soft and longer in range, this transition sets in at lower concentrations, and the glass and the jamming regimes are smeared. However, at higher electrolyte concentrations the interactions are stiffer, and the characteristics of the glass-jamming transition resemble more closely the situation of disordered elastic spheres having sharp interfaces, so the glass and jamming regimes can be distinguished more clearly.

  19. A simple method for tuning the glass transition process in inorganic phosphate glasses

    Science.gov (United States)

    Fulchiron, René; Belyamani, Imane; Otaigbe, Joshua U.; Bounor-Legaré, Véronique

    2015-02-01

    The physical modification of glass transition temperature (Tg) and properties of materials via blending is a common practice in industry and academia and has a large economic advantage. In this context, simple production of hitherto unattainable new inorganic glass blends from already existing glass compositions via blending raises much hope with the potential to provide new glasses with new and improved properties, that cannot be achieved with classical glass synthesis, for a plethora of applications such as computers screens, glass-to-metal seals, and storage materials for nuclear wastes. Here, we demonstrate that blends of the specific glass compositions studied are miscible in all proportions, an unreported phenomenon in hard condensed matter like glass. Interestingly, excellent agreement was found between the obtained data and calculated Tgs from theoretical equations (Supplementary information) for predicting the composition dependence of Tg for miscible blends with weak but significant specific interactions between the blend components. That this blending method is at present not applied to inorganic glasses reflects the fact that water and chemically resistant phosphate glasses with relatively low Tgs have become available only recently.

  20. Piezoelectricity of a ferroelectric liquid crystal with a glass transition.

    Science.gov (United States)

    Jákli, A; Tóth-Katona, T; Scharf, T; Schadt, M; Saupe, A

    2002-07-01

    Pressure-electric (hydrostatic piezoelectric) measurements are reported on bookshelf textures of a ferroelectric smectic-C (Sm C*) liquid crystal with a glass transition. The continuous variation of a partially fluid state to the solid glass enables one to trace how the piezoelectric effect depends on the consistency of the material. It was observed that in the Sm C* samples with poled glass the piezoelectric constants are comparable to conventional piezoelectric crystals and poled piezoelectric polymers. This implies their application possibilities. The magnitude of the piezoelectric constant in the glassy state depends very much on the poling conditions. The studies indicate that there are two counteracting effects, which cancel each other out in the Sm C* phase near the glass transition. Our analysis indicates that the pressure-induced director tilt change has a dominating effect both in the fluid and the glassy Sm C* states.

  1. Solvent induced supramolecular anisotropy in molecular gels

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Michael A., E-mail: mroger09@uoguelph.ca [Department of Food Science, University of Guelph, Guelph, Ontario, N3C3X9 (Canada); Corradini, Maria G. [Department of Food Science, University of Massachusetts Amherst, Amherst, MA, 01003 (United States); Emge, Thomas [Department of Chemistry and Biochemistry, Rutgers University, New Brunswick, NJ, 08901 (United States)

    2017-06-15

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  2. Solvent induced supramolecular anisotropy in molecular gels

    International Nuclear Information System (INIS)

    Rogers, Michael A.; Corradini, Maria G.; Emge, Thomas

    2017-01-01

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  3. Glass transition of repulsive charged rods (fd-viruses).

    Science.gov (United States)

    Kang, Kyongok

    2014-05-14

    It has recently been shown that suspensions of long and thin charged fibrous viruses (fd) form a glass at low ionic strengths. The corresponding thick electric double layers give rise to long-ranged repulsive electrostatic interactions, which lead to caging and structural arrest at concentrations far above the isotropic-nematic coexistence region. Structural arrest and freezing of the orientational texture are found to occur at the same concentration. In addition, various types of orientational textures are equilibrated below the glass transition concentration, ranging from a chiral-nematic texture with a large pitch (of about 100 μm), an X-pattern, and a tightly packed domain texture, consisting of helical domains with a relatively small pitch (of about 10 μm) and twisted boundaries. The dynamics of both particles as well as the texture are discussed, below and above the glass transition. Dynamic light scattering correlation functions exhibit two dynamical modes, where the slow mode is attributed to the elasticity of helical domains. On approach of the glass-transition concentration, the slow mode increases in amplitude, while as the amplitudes of the fast and slow mode become equal at the glass transition. Finally, interesting features of the "transient" behaviors of charged fd-rod glass are shown as the initial caging due to structural arrest, the propagation of flow originating from stress release, and the transition to the final metastable glass state. In addition to the intensity correlation function, power spectra are presented as a function of the waiting time, at the zero-frequency limit that may access to the thermal anomalities in a charged system.

  4. Unique properties associated with normal martensitic transition and strain glass transition – A simulation study

    International Nuclear Information System (INIS)

    Wang, Dong; Ni, Yan; Gao, Jinghui; Zhang, Zhen; Ren, Xiaobing; Wang, Yunzhi

    2013-01-01

    Highlights: ► We model the unique properties of strain glass which is different from that of normal martensite. ► We describe the importance of point defects in the formation of strain glass and related properties. ► The role of point defect can be attributed to global transition temperature effect (GTTE) and local field effect (LFE). -- Abstract: The transition behavior and unique properties associated with normal martensitic transition and strain glass transition are investigated by computer simulations using the phase field method. The simulations are based on a physical model that assumes that point defects alter the thermodynamic stability of martensite and create local lattice distortion. The simulation results show that strain glass transition exhibits different properties from those found in normal martensitic transformations. These unique properties include diffuse scattering pattern, “smear” elastic modulus peak, disappearance of heat flow peak and non-ergodicity. These simulation predictions agree well with the experimental observations

  5. A universal reduced glass transition temperature for liquids

    Science.gov (United States)

    Fedors, R. F.

    1979-01-01

    Data on the dependence of the glass transition temperature on the molecular structure for low-molecular-weight liquids are analyzed in order to determine whether Boyer's reduced glass transition temperature (1952) is a universal constant as proposed. It is shown that the Boyer ratio varies widely depending on the chemical nature of the molecule. It is pointed out that a characteristic temperature ratio, defined by the ratio of the sum of the melting temperature and the boiling temperature to the sum of the glass transition temperature and the boiling temperature, is a universal constant independent of the molecular structure of the liquid. The average value of the ratio obtained from data for 65 liquids is 1.15.

  6. Predictions of glass transition temperature for hydrogen bonding biomaterials.

    Science.gov (United States)

    van der Sman, R G M

    2013-12-19

    We show that the glass transition of a multitude of mixtures containing hydrogen bonding materials correlates strongly with the effective number of hydroxyl groups per molecule, which are available for intermolecular hydrogen bonding. This correlation is in compliance with the topological constraint theory, wherein the intermolecular hydrogen bonds constrain the mobility of the hydrogen bonded network. The finding that the glass transition relates to hydrogen bonding rather than free volume agrees with our recent finding that there is little difference in free volume among carbohydrates and polysaccharides. For binary and ternary mixtures of sugars, polyols, or biopolymers with water, our correlation states that the glass transition temperature is linear with the inverse of the number of effective hydroxyl groups per molecule. Only for dry biopolymer/sugar or sugar/polyol mixtures do we find deviations due to nonideal mixing, imposed by microheterogeneity.

  7. Fluorinated epoxy resins with high glass transition temperatures

    Science.gov (United States)

    Griffith, James R.

    1991-01-01

    Easily processed liquid resins of low dielectric constants and high glass transition temperatures are useful for the manufacture of certain composite electronic boards. That combination of properties is difficult to acquire when dielectric constants are below 2.5, glass transition temperatures are above 200 C and processability is of conventional practicality. A recently issued patent (US 4,981,941 of 1 Jan. 1991) teaches practical materials and is the culmination of 23 years of research and effort and 15 patents owned by the Navy in the field of fluorinated resins of several classes. In addition to high fluorine content, practical utility was emphasized.

  8. Ideal glass transitions in thin films: An energy landscape perspective

    Science.gov (United States)

    Truskett, Thomas M.; Ganesan, Venkat

    2003-07-01

    We introduce a mean-field model for the potential energy landscape of a thin fluid film confined between parallel substrates. The model predicts how the number of accessible basins on the energy landscape and, consequently, the film's ideal glass transition temperature depend on bulk pressure, film thickness, and the strength of the fluid-fluid and fluid-substrate interactions. The predictions are in qualitative agreement with the experimental trends for the kinetic glass transition temperature of thin films, suggesting the utility of landscape-based approaches for studying the behavior of confined fluids.

  9. Inward Cationic Diffusion and Percolation Transition in Glass-Ceramics

    DEFF Research Database (Denmark)

    Smedsklaer, Morten Mattrup; Yue, Yuanzheng; Mørup, Steen

    2010-01-01

    We show the quantitative correlation between the degree of crystallization and the cationic diffusion extent in iron-containing diopside glass–ceramics at the glass transition temperature. We find a critical degree of crystallization, above which the diffusion extent sharply drops with the degree...... of crystallization. Below the critical value, the diffusion extent decreases only slightly with the degree of crystallization. No cationic diffusion is observed in the fully crystalline materials. The critical value might be associated with a percolation transition from an interconnected to a disconnected glass...

  10. 'Vanishing' structural effects of temperature in polymer glasses close to the glass-transition temperature

    International Nuclear Information System (INIS)

    Shantarovich, V.P.; Suzuki, T.; Ito, Y.; Yu, R.S.; Kondo, K.; Yampolskii, Yu. P.; Alentiev, A.Yu.

    2007-01-01

    Positron annihilation lifetime (PAL) measurements were used for observation of structural effects of temperature in polystyrene (PS), super-cross-linked polystyrene networks (CPS), and in polyimides (PI) below and in the vicinity of glass-transition temperature T g . 'Vanishing' of these structural effects in the repeating cycles of the temperature controlled PAL experiments due to the slow relaxation processes in different conditions and details of chemical structure is demonstrated. Obtained results illustrate complex, dependent on thermal history, inhomogeneous character of the glass structure. In fact, structure of some polymer glasses is changing continuously. Calculations of the number density of free volume holes in these conditions are discussed

  11. Polymorphic crystallization of metal-metalloid-glasses above the glass transition temperature

    International Nuclear Information System (INIS)

    Koster, U.; Schunemann, U.; Stephenson, G.B.; Brauer, S.; Sutton, M.

    1992-01-01

    Crystallization of metal-metalloid glasses is known to proceed by nucleation and growth processes. Using crystallization statistics in partially crystallized glasses, at temperatures below the glass transition temperature, time-dependent heterogeneous nucleation has been found to occur at a number of quenched-in nucleation sites. Close to the glass transition temperature crystallization proceeds so rapidly that partially crystallized microstructures could not be obtained. Initial results form fully crystallized glasses exhibit evidence for a transient homogeneous nucleation process at higher temperatures. These conclusions are derived post mortem. At there may be some change of the microstructure after crystallization is finished or during he subsequent quenching, it is desirable to directly obtain information during the early stages of crystallization. Recently reported work by Sutton et al. showed that structural changes can be observed in situ during crystallization by time-resolved x-ray diffraction on time scales as short as milliseconds. The aim o the paper is to present the authors study of the crystallization behavior at temperatures near the glass transition by in-situ x-ray diffraction studies and by microstructural analysis after rapid heating experiments. The results are compared to those derived from a computer model of the crystallization process

  12. Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System

    Directory of Open Access Journals (Sweden)

    Nicolas Giovambattista

    2010-12-01

    Full Text Available We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.

  13. Configurational entropy of polar glass formers and the effect of electric field on glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Matyushov, Dmitry V., E-mail: dmitrym@asu.edu [Department of Physics and School of Molecular Sciences, Arizona State University, P.O. Box 871504, Tempe, Arizona 85287 (United States)

    2016-07-21

    A model of low-temperature polar liquids is constructed that accounts for the configurational heat capacity, entropy, and the effect of a strong electric field on the glass transition. The model is based on the Padé-truncated perturbation expansions of the liquid state theory. Depending on parameters, it accommodates an ideal glass transition of vanishing configurational entropy and its avoidance, with a square-root divergent enumeration function at the point of its termination. A composite density-temperature parameter ρ{sup γ}/T, often used to represent combined pressure and temperature data, follows from the model. The theory is in good agreement with the experimental data for excess (over the crystal state) thermodynamics of molecular glass formers. We suggest that the Kauzmann entropy crisis might be a signature of vanishing configurational entropy of a subset of degrees of freedom, multipolar rotations in our model. This scenario has observable consequences: (i) a dynamical crossover of the relaxation time and (ii) the fragility index defined by the ratio of the excess heat capacity and excess entropy at the glass transition. The Kauzmann temperature of vanishing configurational entropy and the corresponding glass transition temperature shift upward when the electric field is applied. The temperature shift scales quadratically with the field strength.

  14. Configurational entropy of polar glass formers and the effect of electric field on glass transition.

    Science.gov (United States)

    Matyushov, Dmitry V

    2016-07-21

    A model of low-temperature polar liquids is constructed that accounts for the configurational heat capacity, entropy, and the effect of a strong electric field on the glass transition. The model is based on the Padé-truncated perturbation expansions of the liquid state theory. Depending on parameters, it accommodates an ideal glass transition of vanishing configurational entropy and its avoidance, with a square-root divergent enumeration function at the point of its termination. A composite density-temperature parameter ρ(γ)/T, often used to represent combined pressure and temperature data, follows from the model. The theory is in good agreement with the experimental data for excess (over the crystal state) thermodynamics of molecular glass formers. We suggest that the Kauzmann entropy crisis might be a signature of vanishing configurational entropy of a subset of degrees of freedom, multipolar rotations in our model. This scenario has observable consequences: (i) a dynamical crossover of the relaxation time and (ii) the fragility index defined by the ratio of the excess heat capacity and excess entropy at the glass transition. The Kauzmann temperature of vanishing configurational entropy and the corresponding glass transition temperature shift upward when the electric field is applied. The temperature shift scales quadratically with the field strength.

  15. Deformation, Stress Relaxation, and Crystallization of Lithium Silicate Glass Fibers Below the Glass Transition Temperature

    Science.gov (United States)

    Ray, Chandra S.; Brow, Richard K.; Kim, Cheol W.; Reis, Signo T.

    2004-01-01

    The deformation and crystallization of Li(sub 2)O (center dot) 2SiO2 and Li(sub 2)O (center dot) 1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range -50 to -150 C below the glass transition temperature (Tg). The glass fibers can be permanently deformed at temperatures about 100 C below T (sub)g, and they crystallize significantly at temperatures close to, but below T,, about 150 C lower than the onset temperature for crystallization for these glasses in the no-stress condition. The crystallization was found to occur only on the surface of the glass fibers with no detectable difference in the extent of crystallization in tensile and compressive stress regions. The relaxation mechanism for fiber deformation can be best described by a stretched exponential (Kohlrausch-Williams-Watt (KWW) approximation), rather than a single exponential model.The activation energy for stress relaxation, Es, for the glass fibers ranges between 175 and 195 kJ/mol, which is considerably smaller than the activation energy for viscous flow, E, (about 400 kJ/mol) near T, for these glasses at normal, stress-free condition. It is suspected that a viscosity relaxation mechanism could be responsible for permanent deformation and crystallization of the glass fibers below T,

  16. Thermal expansion accompanying the glass-liquid transition and crystallization

    Directory of Open Access Journals (Sweden)

    M. Q. Jiang

    2015-12-01

    Full Text Available We report the linear thermal expansion behaviors of a Zr-based (Vitreloy 1 bulk metallic glass in its as-cast, annealed and crystallized states. Accompanying the glass-liquid transition, the as-cast Vitreloy 1 shows a continuous decrease in the thermal expansivity, whereas the annealed glass shows a sudden increase. The crystallized Vitreloy 1 exhibits an almost unchanged thermal expansivity prior to its melting. Furthermore, it is demonstrated that the nucleation of crystalline phases can induce a significant thermal shrinkage of the supercooled liquid, but with the growth of these nuclei, the thermal expansion again dominates. These results are explained in the framework of the potential energy landscape, advocating that the configurational and vibrational contributions to the thermal expansion of the glass depend on both, structure and temperature.

  17. Application of Kissinger analysis to glass transition and study of ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 35; Issue 4. Application of Kissinger analysis to glass transition and study of thermal degradation kinetics of phenolic–acrylic IPNs ... Author Affiliations. S Goswami1 K Kiran1. Department of Polymer Engineering, Birla Institute of Technology, Ranchi 835 215, India ...

  18. Depression of Glass Transition Temperatures of Polymer Networks by Diluents

    NARCIS (Netherlands)

    Brinke, Gerrit ten; Karasz, Frank E.; Ellis, Thomas S.

    1983-01-01

    A classical thermodynamic theory is used to derive expressions for the depression of the glass transition temperature Tg of a polymer network by a diluent. The enhanced sensitivity of Tg in cross-linked systems to small amounts of diluent is explained. Predictions of the theory are in satisfactory

  19. Note on the glass transition temperature of poly(vinylphenol)

    Czech Academy of Sciences Publication Activity Database

    Kratochvíl, Jaroslav; Šturcová, Adriana; Sikora, Antonín; Dybal, Jiří

    2009-01-01

    Roč. 45, č. 6 (2009), s. 1851-1856 ISSN 0014-3057 Institutional research plan: CEZ:AV0Z40500505 Keywords : Poly(4-vinylphenol) * glass transition temperature * differential scanning calorimetry Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.310, year: 2009

  20. Beta relaxation of nonpolymeric liquids close to the glass transition

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Christensen, Tage Emil; Dyre, Jeppe

    2000-01-01

    Dielectric beta relaxation in a pyridine-toluene solution is studied close to the glass transition. Loss peak frequency and maximum loss both exhibit thermal hysteresis. An annealing-state-independent parameter involving loss and loss peak frequency is identified. This parameter has a simple...

  1. Glass transition and crystallization kinetics of a barium borosilicate glass by a non-isothermal method

    International Nuclear Information System (INIS)

    Lopes, Andreia A. S.; Soares, Roque S.; Lima, Maria M. A.; Monteiro, Regina C. C.

    2014-01-01

    The glass transition and crystallization kinetics of a glass with a molar composition 60BaO-30B 2 O 3 -10SiO 2 were investigated by differential scanning calorimetry (DSC) under non-isothermal conditions. DSC curves exhibited an endothermic peak associated with the glass transition and two partially overlapped exothermic peaks associated with the crystallization of the glass. The dependence of the glass transition temperature (T g ) and of the maximum crystallization temperature (T p ) on the heating rate was used to determine the activation energy associated with the glass transition (E g ), the activation energy for crystallization (E c ), and the Avrami exponent (n). X-ray diffraction (XRD) revealed that barium borate (β-BaB 2 O 4 ) was the first crystalline phase to be formed followed by the formation of barium silicate (Ba 5 Si 8 O 21 ). The variations of activation energy for crystallization and of Avrami exponent with the fraction of crystallization (χ) were also examined. When the crystallization fraction (χ) increased from 0.1 to 0.9, the value of local activation energy (E c (χ)) decreased from 554 to 458 kJ/mol for the first exothermic peak and from 1104 to 831 kJ/mol for the second exothermic peak. The value determined for the Avrami exponent was near 2 indicating a similar one-dimensional crystallization mechanism for both crystalline phases. This was confirmed by the morphological studies performed by scanning electron microscopy (SEM) on glass samples heat-treated at the first and at the second crystallization temperatures

  2. Glass transition near the free surface studied by synchrotron radiation

    International Nuclear Information System (INIS)

    Sikorski, M.

    2008-06-01

    A comprehensive picture of the glass transition near the liquid/vapor interface of the model organic glass former dibutyl phthalate is presented in this work. Several surface-sensitive techniques using x-ray synchrotron radiation were applied to investigate the static and dynamic aspects of the formation of the glassy state from the supercooled liquid. The amorphous nature of dibutyl phthalate close to the free surface was confirmed by grazing incidence X-ray diffraction studies. Results from X-ray reflectivity measurements indicate a uniform electron density distribution close to the interface excluding the possibility of surface freezing down to 175 K. Dynamics on sub-μm length-scales at the surface was studied with coherent synchrotron radiation via x-ray photon correlation spectroscopy. From the analysis of the dispersion relation of the surface modes, viscoelastic properties of the dibutyl phthalate are deduced. The Kelvin-Voigt model of viscoelastic media was found to describe well the properties of the liquid/vapor interface below room temperature. The data show that the viscosity at the interface matches the values reported for bulk dibutyl phthalate. The scaled relaxation rate at the surface agrees with the bulk data above 210 K. Upon approaching the glass transition temperature the free surface was observed to relax considerably faster close to the liquid/vapor interface than in bulk. The concept of higher relaxation rate at the free surface is also supported by the results of the quasielastic nuclear forward scattering experiment, during which dynamics on molecular length scales around the calorimetric glass transition temperature is studied. The data were analyzed using mode-coupling theory of the glass transition and the model of the liquid(glass)/vapor interface, predicting inhomogeneous dynamics near the surface. The quasielastic nuclear forward scattering data can be explained when the molecular mobility is assumed to decrease with the increasing

  3. Glass transition near the free surface studied by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sikorski, M.

    2008-06-15

    A comprehensive picture of the glass transition near the liquid/vapor interface of the model organic glass former dibutyl phthalate is presented in this work. Several surface-sensitive techniques using x-ray synchrotron radiation were applied to investigate the static and dynamic aspects of the formation of the glassy state from the supercooled liquid. The amorphous nature of dibutyl phthalate close to the free surface was confirmed by grazing incidence X-ray diffraction studies. Results from X-ray reflectivity measurements indicate a uniform electron density distribution close to the interface excluding the possibility of surface freezing down to 175 K. Dynamics on sub-{mu}m length-scales at the surface was studied with coherent synchrotron radiation via x-ray photon correlation spectroscopy. From the analysis of the dispersion relation of the surface modes, viscoelastic properties of the dibutyl phthalate are deduced. The Kelvin-Voigt model of viscoelastic media was found to describe well the properties of the liquid/vapor interface below room temperature. The data show that the viscosity at the interface matches the values reported for bulk dibutyl phthalate. The scaled relaxation rate at the surface agrees with the bulk data above 210 K. Upon approaching the glass transition temperature the free surface was observed to relax considerably faster close to the liquid/vapor interface than in bulk. The concept of higher relaxation rate at the free surface is also supported by the results of the quasielastic nuclear forward scattering experiment, during which dynamics on molecular length scales around the calorimetric glass transition temperature is studied. The data were analyzed using mode-coupling theory of the glass transition and the model of the liquid(glass)/vapor interface, predicting inhomogeneous dynamics near the surface. The quasielastic nuclear forward scattering data can be explained when the molecular mobility is assumed to decrease with the increasing

  4. The nature of the colloidal 'glass' transition.

    Science.gov (United States)

    Dawson, Kenneth A; Lawlor, A; DeGregorio, Paolo; McCullagh, Gavin D; Zaccarelli, Emanuela; Foffi, Giuseppe; Tartaglia, Piero

    2003-01-01

    The dynamically arrested state of matter is discussed in the context of athermal systems, such as the hard sphere colloidal arrest. We believe that the singular dynamical behaviour near arrest expressed, for example, in how the diffusion constant vanishes may be 'universal', in a sense to be discussed in the paper. Based on this we argue the merits of studying the problem with simple lattice models. This, by analogy with the the critical point of the Ising model, should lead us to clarify the questions, and begin the program of establishing the degree of universality to be expected. We deal only with 'ideal' athermal dynamical arrest transitions, such as those found for hard sphere systems. However, it is argued that dynamically available volume (DAV) is the relevant order parameter of the transition, and that universal mechanisms may be well expressed in terms of DAV. For simple lattice models we give examples of simple laws that emerge near the dynamical arrest, emphasising the idea of a near-ideal gas of 'holes', interacting to give the power law diffusion constant scaling near the arrest. We also seek to open the discussion of the possibility of an underlying weak coupling theory of the dynamical arrest transition, based on DAV.

  5. Glass transition and density fluctuations in the fragile glass former orthoterphenyl

    International Nuclear Information System (INIS)

    Monaco, G.; Fioretto, D.; Comez, L.; Ruocco, G.

    2001-01-01

    High-resolution Brillouin light scattering is used to measure the dynamic structure factor of the fragile glass former orthoterphenyl (OTP) in a wide temperature range around the glass transition region and up to the boiling point. The whole set of spectra is described in terms of a phenomenological generalized hydrodynamic model. In the supercooled phase, we show the contemporary existence of the structural process, whose main features come out to be consistent with the results obtained with other spectroscopies, and of a secondary, activated process, which occurs on the 10 -11 s time scale and has a low activation energy (E a f =0.28 kcal/mol). This latter process, which is also present in the glassy phase and seems to be insensitive to the glass transition, is attributed to the coupling between the density modes and intramolecular degrees of freedom. In the normal liquid phase, the two processes merge together, and the resulting characteristic time is no longer consistent with those derived with other spectroscopies. The analysis points to the conclusion that, for what concerns the long-wavelength density fluctuations in fragile glass formers such as OTP, the universal dynamical features related to the glass transition come out clearly only in the supercooled phase and at frequencies lower than ∼10 6 Hz

  6. Investigation of low glass transition temperature on COTS PEM's reliability for space applications

    Science.gov (United States)

    Sandor, M.; Agarwal, S.; Peters, D.; Cooper, M. S.

    2003-01-01

    Plastic Encapsulated Microelectronics (PEM) reliability is affected by many factors. Glass transition temperature (Tg) is one such factor. In this presentation issues relating to PEM reliability and the effect of low glass transition temperature epoxy mold compounds are presented.

  7. The electronic conduction of glass and glass ceramics containing various transition metal oxides

    International Nuclear Information System (INIS)

    Yoshida, T.; Matsuno, Y.

    1980-01-01

    Nb 2 O 5 -V 2 O 5 -P 2 O 5 glasses containing only Group Va oxides have been investigated to elucidate their electronic conduction and structure, as compared with other glasses obtained by the addition of various transition metal oxides to vanadium phosphate. The P 2 O 5 introduction for Nb 2 O 5 in this glass with the same amount of V 2 O 5 increased the conductivity about two times. Glass ceramics having high conductivity increased by two orders of magnitude and the activation energy for conduction decreased from about 0.5 to 0.2 eV. The crystals were confirmed to be (V,Nb) 2 O 5 and Nb phosphate, one of which was highly conductive and developed a pillar-like shape with a length of more than 20 μm. (orig.)

  8. Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition

    DEFF Research Database (Denmark)

    Mattern, N.; Hermann, H.; Roth, S.

    2003-01-01

    The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows...... the Debye theory up to the glass transition with a Debye temperature theta=296 K. Above the glass transition temperature T-g, the temperature dependence of S(q) is altered, pointing to a continuous development of structural changes in the liquid with temperature. The atomic pair correlation functions g......(r) indicate changes in short-range-order parameters of the first and the second neighborhood with temperature. The temperature dependence of structural parameters is different in glass and in supercooled liquid, with a continuous behavior through the glass transition. The nearest-neighbor distance decreases...

  9. Unusual Crystallization Behavior Close to the Glass Transition

    Science.gov (United States)

    Desgranges, Caroline; Delhommelle, Jerome

    2018-03-01

    Using molecular simulations, we shed light on the mechanism underlying crystal nucleation in metal alloys and unravel the interplay between crystal nucleation and glass transition, as the conditions of crystallization lie close to this transition. While decreasing the temperature of crystallization usually results in a lower free energy barrier, we find an unexpected reversal of behavior for glass-forming alloys as the temperature of crystallization approaches the glass transition. For this purpose, we simulate the crystallization process in two glass-forming Copper alloys, Ag6 Cu4 , which has a positive heat of mixing, and CuZr, characterized by a large negative heat of mixing. Our results allow us to identify this unusual behavior as directly correlated with a nonmonotonic temperature dependence for the formation energy of connected icosahedral structures, which are incompatible with crystalline order and impede the development of the crystal nucleus, leading to an unexpectedly larger free energy barrier at low temperature. This, in turn, promotes the formation of a predominantly closed-packed critical nucleus, with fewer defects, thereby suggesting a new way to control the structure of the crystal nucleus, which is of key importance in catalysis.

  10. Magnetization relaxation in spin glasses above transition point

    International Nuclear Information System (INIS)

    Zajtsev, I.A.; Minakov, A.A.; Galonzka, R.R.

    1988-01-01

    Magnetization relaxation of Cd 0.6 Zn 0.4 Cr 2 Se 4 and Cd 0.6 Mn 0.4 Te monocrystalline samples with T g =21 K and T g =12 K respectively and magnetic colloid is investigated. It is shown that magnetization inexponential relaxation detected experimentally in spin and dipole glasses is essentially higher than T g temperature transition. It is found that at temperatures higher than T g the essential difference is observed in behaviour of spin glasses with different Z and disorder types

  11. Dynamic thermal expansivity of liquids near the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage Emil

    2012-01-01

    Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704) in the ......Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704...... the liquid contracts when cooling from room temperature down to around the glass-transition temperature, which is relevant when measuring on a molecular liquid rather than a polymer....

  12. Glass transition, crystallization kinetics and pressure effect on crystallization of ZrNbCuNiBe bulk metallic glass

    DEFF Research Database (Denmark)

    Xing, P.F.; Zhuang, Yanxin; Wang, W.H.

    2002-01-01

    The glass transition behavior and crystallization kinetics of Zr48Nb8Cu14Ni12Be18 bulk metallic glass have been investigated by differential scanning calorimetry and x-ray powder diffraction (XRD). The activation energies of both glass transition and crystallization events have been obtained using...... the Kissinger method. Results indicate that this glass crystallizes by a three-stage reaction: (1) phase separation and primary crystallization of glass, (2) formation of intermetallic compounds, and (3) decomposition of intermetallic compounds and crystallization of residual amorphous phase. The pressure...

  13. Testing the paradigms of the glass transition in colloids

    Science.gov (United States)

    Zia, Roseanna; Wang, Jialun; Peng, Xiaoguang; Li, Qi; McKenna, Gregory

    2017-11-01

    Many molecular liquids freeze upon fast enough cooling. This so-called glass state is path dependent and out of equilibrium, as measured by the Kovacs signature experiments, i.e. intrinsic isotherms, asymmetry of approach and memory effect. The reasons for this path- and time-dependence are not fully understood, due to fast molecular relaxations. Colloids provide a natural way to model such behavior, owing to disparity in colloidal versus solvent time scales that can slow dynamics. To shed light on the ambiguity of glass transition, we study via large-scale dynamic simulation of hard-sphere colloidal glass after volume-fraction jumps, where particle size increases at fixed system volume followed by protocols of the McKenna-Kovacs signature experiments. During and following each jump, the positions, velocities, and particle-phase stress are tracked and utilized to characterize relaxation time scales. The impact of both quench depth and quench rate on arrested dynamics and ``state'' variables is explored. In addition, we expand our view to various structural signatures, and rearrangement mechanism is proposed. The results provide insight into not only the existence of an ``ideal'' glass transition, but also the role of structure in such a dense amorphous system.

  14. Water sorption and glass transition of amorphous sugars containing BSA

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, K.; Suzuki, T.; Tatsumichi, T.; Kirii, S.; Okazaki, M. [Kyoto Univ., Kyoto (Japan). Dept. of Chemical Engineering

    2000-08-01

    Water sorption and glass transition of four amorphous sugars (lactose, maltose, sucrose, and trehalose) containing bovine serum albumin (BSA) are investigated. Freeze-dried sugar-BSA samples equilibrated at several water activities ranging from 0 to 0.43 were prepared. Moisture content and glass transition temperature (T{sub g}) were measured. For the all sugars, it is found that BSA lowers T{sub g} at low water activity, and raises it at high water activity. It is also found that the difference between T{sub g} of the sugar-BSA samples and that of the corresponding amorphous sugar samples (T{sub g0}) depends mainly on T{sub g0}. (author)

  15. Multiple Glass Transitions and Freezing Events of Aqueous Citric Acid

    Science.gov (United States)

    2014-01-01

    Calorimetric and optical cryo-microscope measurements of 10–64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid–glass transitions upon cooling and from one to six liquid–glass and reverse glass–liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role. PMID:25482069

  16. Noise as a Probe of Ising Spin Glass Transitions

    Science.gov (United States)

    Chen, Zhi; Yu, Clare

    2009-03-01

    Noise is ubiquitous and and is often viewed as a nuisance. However, we propose that noise can be used as a probe of the fluctuations of microscopic entities, especially in the vicinity of a phase transition. In recent work we have used simulations to show that the noise increases in the vicinity of phase transitions of ordered systems. We have recently turned our attention to noise near the phase transitions of disordered systems. In particular, we are studying the noise near Ising spin glass transitions using Monte Carlo simulations. We monitor the system as a function of temperature. At each temperature, we obtain the time series of quantities characterizing the properties of the system, i.e., the energy and magnetization. We look at different quantities, such as the noise power spectrum and the second spectrum of the noise, to analyze the fluctuations.

  17. Motility-driven glass and jamming transitions in biological tissues

    Science.gov (United States)

    Bi, Dapeng; Yang, Xingbo; Marchetti, M. Cristina; Manning, M. Lisa

    2017-01-01

    Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. To make quantitative predictions about glass transitions in tissues, we study a self-propelled Voronoi (SPV) model that simultaneously captures polarized cell motility and multi-body cell-cell interactions in a confluent tissue, where there are no gaps between cells. We demonstrate that the model exhibits a jamming transition from a solid-like state to a fluid-like state that is controlled by three parameters: the single-cell motile speed, the persistence time of single-cell tracks, and a target shape index that characterizes the competition between cell-cell adhesion and cortical tension. In contrast to traditional particulate glasses, we are able to identify an experimentally accessible structural order parameter that specifies the entire jamming surface as a function of model parameters. We demonstrate that a continuum Soft Glassy Rheology model precisely captures this transition in the limit of small persistence times, and explain how it fails in the limit of large persistence times. These results provide a framework for understanding the collective solid-to-liquid transitions that have been observed in embryonic development and cancer progression, which may be associated with Epithelial-to-Mesenchymal transition in these tissues. PMID:28966874

  18. Determination of the glass transition temperature of cyclodextrin polymers.

    Science.gov (United States)

    Tabary, Nicolas; Garcia-Fernandez, Maria Jose; Danède, Florence; Descamps, Marc; Martel, Bernard; Willart, Jean-François

    2016-09-05

    The aim of this work was to determine the main physical characteristics of β-cyclodextrin polymers, well known for improving complexation capacities and providing enhanced and sustained release of a large panel of drugs. Two polymers were investigated: a polymer of β-cyclodextrin (polyβ-CD) and a polymer of partially methylated (DS=0.57) β-cyclodextrin (polyMe-β-CD). The physical characterizations were performed by powder X-ray diffraction and differential scanning calorimetry. The results indicate that these polymers are amorphous and that their glass transition is located above the thermal degradation point of the materials preventing their direct observation and thus their full characterization. We could however estimate the virtual glass transition temperatures by mixing the polymers with different plasticizers (trehalose and mannitol) which decreases Tg sufficiently to make the glass transition observable. Extrapolation to zero plasticizer concentration then yield the following Tg values: Tg (polyMe-β-CD)=317°C±5°C and Tg (polyβ-CD)=418°C±6°C. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Simple solvable energy-landscape model that shows a thermodynamic phase transition and a glass transition.

    Science.gov (United States)

    Naumis, Gerardo G

    2012-06-01

    When a liquid melt is cooled, a glass or phase transition can be obtained depending on the cooling rate. Yet, this behavior has not been clearly captured in energy-landscape models. Here, a model is provided in which two key ingredients are considered in the landscape, metastable states and their multiplicity. Metastable states are considered as in two level system models. However, their multiplicity and topology allows a phase transition in the thermodynamic limit for slow cooling, while a transition to the glass is obtained for fast cooling. By solving the corresponding master equation, the minimal speed of cooling required to produce the glass is obtained as a function of the distribution of metastable states.

  20. Shear viscosity of glass-forming melts in the liquid-glass transition region

    International Nuclear Information System (INIS)

    Sanditov, D. S.

    2010-01-01

    A new approach to interpreting the hole-activation model of a viscous flow of glass-forming liquids is proposed. This model underlies the development of the concept on the exponential temperature dependence of the free energy of activation of a flow within the range of the liquid-glass transition in complete agreement with available experimental data. The 'formation of a fluctuation hole' in high-heat glass-forming melts is considered as a small-scale low-activation local deformation of a structural network, i.e., the quasi-lattice necessary for the switching of the valence bond, which is the main elementary event of viscous flow of glasses and their melts. In this sense, the hole formation is a conditioned process. A drastic increase in the activation free energy of viscous flow in the liquid-glass transition region is explained by a structural transformation that is reduced to a limiting local elastic deformation of the structural network, which, in turn, originates from the excitation (critical displacement) of a bridging atom like the oxygen atom in the Si-O-Si bridge. At elevated temperatures, as a rule, a necessary amount of excited bridging atoms (locally deformed regions of the structural network) always exists, and the activation free energy of viscous flow is almost independent of temperature. The hole-activation model is closely connected with a number of well-known models describing the viscous flow of glass-forming liquids (the Avramov-Milchev, Nemilov, Ojovan, and other models).

  1. Predicting bioactive glass properties from the molecular chemical composition: glass transition temperature.

    Science.gov (United States)

    O'Donnell, Matthew D

    2011-05-01

    The glass transition temperature (T(g)) of inorganic glasses is an important parameter than can be used to correlate with other glass properties, such as dissolution rate, which governs in vitro and in vivo bioactivity. Seven bioactive glass compositional series reported in the literature (77 in total) were analysed here with T(g) values obtained by a number of different methods: differential thermal analysis, differential scanning calorimetry and dilatometry. An iterative least-squares fitting method was used to correlate T(g) from thermal analysis of these compositions with the levels of individual oxide and fluoride components in the glasses. When all seven series were fitted a reasonable correlation was found between calculated and experimental values (R(2)=0.89). When the two compositional series that were designed in weight percentages (the remaining five were designed in molar percentage) were removed from the model an improved fit was achieved (R(2)=0.97). This study shows that T(g) for a wide range in compositions (e.g. SiO(2) content of 37.3-68.4 mol.%) can be predicted to reasonable accuracy enabling processing parameters to be predicted such as annealing, fibre-drawing and sintering temperatures. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Kinetic arrest and glass-glass transition in short-ranged attractive colloids

    International Nuclear Information System (INIS)

    Sztucki, M.; Narayanan, T.; Belina, G.; Moussaied, A.; Pignon, F.; Hoekstra, H.

    2006-01-01

    A thermally reversible repulsive hard-sphere to sticky-sphere transition was studied in a model colloidal system over a wide volume fraction range. The static microstructure was obtained from high resolution small angle x-ray scattering, the colloid dynamics was probed by dynamic x-ray and light scattering, and supplementary mechanical properties were derived from bulk rheology. At low concentration, the system shows features of gas-liquid type phase separation. The bulk phase separation is presumably interrupted by a gelation transition at the intermediate volume fraction range. At high volume fractions, fluid-attractive glass and repulsive glass-attractive glass transitions are observed. It is shown that the volume fraction of the particles can be reliably deduced from the absolute scattered intensity. The static structure factor is modeled in terms of an attractive square-well potential, using the leading order series expansion of Percus-Yevick approximation. The ensemble-averaged intermediate scattering function shows different levels of frozen components in the attractive and repulsive glassy states. The observed static and dynamic behavior are consistent with the predictions of a mode-coupling theory and numerical simulations for a square-well attractive system

  3. Raman scattering boson peak and differential scanning calorimetry studies of the glass transition in tellurium-zinc oxide glasses.

    Science.gov (United States)

    Stavrou, E; Tsiantos, C; Tsopouridou, R D; Kripotou, S; Kontos, A G; Raptis, C; Capoen, B; Bouazaoui, M; Turrell, S; Khatir, S

    2010-05-19

    Raman scattering and differential scanning calorimetry (DSC) measurements have been carried out on four mixed tellurium-zinc oxide (TeO(2))(1 - x)(ZnO)(x) (x = 0.1, 0.2, 0.3, 0.4) glasses under variable temperature, with particular attention being given to the respective glass transition region. From the DSC measurements, the glass transition temperature T(g) has been determined for each glass, showing a monotonous decrease of T(g) with increasing ZnO content. The Raman study is focused on the low-frequency band of the glasses, the so-called boson peak (BP), whose frequency undergoes an abrupt decrease at a temperature T(d) very close to the respective T(g) values obtained by DSC. These results show that the BP is highly sensitive to dynamical effects over the glass transition and provides a means for an equally reliable (to DSC) determination of T(g) in tellurite glasses and other network glasses. The discontinuous temperature dependence of the BP frequency at the glass transition, along with the absence of such a behaviour by the high-frequency Raman bands (due to local atomic vibrations), indicates that marked changes of the medium range order (MRO) occur at T(g) and confirms the correlation between the BP and the MRO of glasses.

  4. Raman scattering boson peak and differential scanning calorimetry studies of the glass transition in tellurium-zinc oxide glasses

    International Nuclear Information System (INIS)

    Stavrou, E; Tsiantos, C; Tsopouridou, R D; Kripotou, S; Kontos, A G; Raptis, C; Capoen, B; Bouazaoui, M; Turrell, S; Khatir, S

    2010-01-01

    Raman scattering and differential scanning calorimetry (DSC) measurements have been carried out on four mixed tellurium-zinc oxide (TeO 2 ) 1-x (ZnO) x (x = 0.1, 0.2, 0.3, 0.4) glasses under variable temperature, with particular attention being given to the respective glass transition region. From the DSC measurements, the glass transition temperature T g has been determined for each glass, showing a monotonous decrease of T g with increasing ZnO content. The Raman study is focused on the low-frequency band of the glasses, the so-called boson peak (BP), whose frequency undergoes an abrupt decrease at a temperature T d very close to the respective T g values obtained by DSC. These results show that the BP is highly sensitive to dynamical effects over the glass transition and provides a means for an equally reliable (to DSC) determination of T g in tellurite glasses and other network glasses. The discontinuous temperature dependence of the BP frequency at the glass transition, along with the absence of such a behaviour by the high-frequency Raman bands (due to local atomic vibrations), indicates that marked changes of the medium range order (MRO) occur at T g and confirms the correlation between the BP and the MRO of glasses.

  5. Neutron- and light-scattering studies of the liquid-to-glass and glass-to-glass transitions in dense copolymer micellar solutions

    International Nuclear Information System (INIS)

    Chen Weiren; Chen Sowhsin; Mallamace, Francesco; Glinka, Charles J.; Fratini, Emiliano

    2003-01-01

    Recent mode coupling theory (MCT) calculations show that if a short-range attractive interaction is added to the pure hard sphere system, one may observe a new type of glass originating from the clustering effect (the attractive glass) as a result of the attractive interaction. This is in addition to the known glass-forming mechanism due to the cage effect in the hard sphere system (the repulsive glass). The calculations also indicate that if the range of attraction is sufficiently short compared to the diameter of the particle, within a certain interval of volume fractions where the two glass-forming mechanisms nearly balance each other, varying the external control parameter, the effective temperature, makes the glass-to-liquid-to-glass reentrance and the glass-to-glass transitions possible. Here we present experimental evidence of both transitions, obtained from small-angle neutron-scattering and photon correlation measurements taken from dense L64 copolymer micellar solutions in heavy water. Varying the temperature in certain predicted volume fraction range triggers a sharp transition between these two different types of glass. In particular, according to MCT, there is an end point (called A 3 singularity) of this glass-to-glass transition line, beyond which the long-time dynamics of the two glasses become identical. Our findings confirm this theoretical prediction. Surprisingly, although the Debye-Waller factors, the long-time limit of the coherent intermediate scattering functions, of these two glasses obtained from photon correlation measurements indeed become identical at the predicted volume fraction, they exhibit distinctly different intermediate time relaxation. Furthermore, our experimental results obtained from volume fractions beyond the end point are characterized by the same features as the repulsive glass obtained before the end point. A complete phase diagram giving the boundaries of the structural arrest transitions for L64 micellar system is

  6. Brittle-to-Ductile Transition in Metallic Glass Nanowires.

    Science.gov (United States)

    Şopu, D; Foroughi, A; Stoica, M; Eckert, J

    2016-07-13

    When reducing the size of metallic glass samples down to the nanoscale regime, experimental studies on the plasticity under uniaxial tension show a wide range of failure modes ranging from brittle to ductile ones. Simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce the brittle-like fracture deformation as found in experiments. Using large-scale molecular dynamics simulations we provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. A model for predicting the critical nanowire aspect ratio for the ductile-to-brittle transition is developed. Furthermore, the structure of brittle nanowires can be tuned to a softer phase characterized by a defective short-range order and an excess free volume upon systematic structural rejuvenation, leading to enhanced tensile ductility. The presented results shed light on the fundamental deformation mechanisms of nanoscaled metallic glasses and demarcate ductile and catastrophic failure.

  7. Chiral-glass transition in a diluted dipolar-interaction Heisenberg system

    International Nuclear Information System (INIS)

    Zhang Kaicheng; Liu Guibin; Zhu Yan

    2011-01-01

    Recently, numerical simulations reveal that a spin-glass transition can occur in the three-dimensional diluted dipolar system. By defining the chirality of triple spins in a diluted dipolar Heisenberg spin glass, we study the chiral ordering in the system using parallel tempering algorithm and heat bath method. The finite-size scaling analysis reveals that the system undergoes a chiral-glass transition at finite temperature. - Highlights: → We define the chirality in a diluted dipolar Heisenberg system. → The system undergoes a chiral-glass transition at finite temperature. → We extract the critical exponents of the chiral-glass transition.

  8. Linking rigidity transitions with enthalpic changes at the glass transition and fragility: insight from a simple oscillator model.

    Science.gov (United States)

    Micoulaut, Matthieu

    2010-07-21

    A low temperature Monte Carlo dynamics of a Keating-like oscillator model is used to study the relationship between the nature of network glasses from the viewpoint of rigidity, the thermal reversibility during the glass transition and the strong-fragile behaviour of glass-forming liquids. The model shows that a Phillips optimal glass formation with minimal enthalpic changes is obtained under a cooling/annealing cycle when the system is optimally constrained by the harmonic interactions, i.e. when it is isostatically rigid. For these peculiar systems with a nearly reversible glass transition, the computed activation energy for relaxation time shows also a minimum, which demonstrates that isostatically rigid glasses are strong (Arrhenius-like) glass-forming liquids. Experiments on chalcogenide and oxide glass-forming liquids are discussed under this new perspective and confirm the theoretical prediction for chalcogenide network glasses whereas limitations of the approach appear for weakly interacting (non-covalent, ionic) systems.

  9. Dynamic thermal expansivity of liquids near the glass transition.

    Science.gov (United States)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage; Dyre, Jeppe C

    2012-04-01

    Based on previous works on polymers by Bauer et al. [Phys. Rev. E 61, 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704) in the ultraviscous regime. Compared to the method of Bauer et al., the dynamical range has been extended by making time-domain experiments and by making very small and fast temperature steps. The modeling of the experiment presented in this paper includes the situation in which the capacitor is not full because the liquid contracts when cooling from room temperature down to around the glass-transition temperature, which is relevant when measuring on a molecular liquid rather than a polymer.

  10. The length and time scales of water's glass transitions

    Science.gov (United States)

    Limmer, David T.

    2014-06-01

    Using a general model for the equilibrium dynamics of supercooled liquids, I compute from molecular properties the emergent length and time scales that govern the nonequilibrium relaxation behavior of amorphous ice prepared by rapid cooling. Upon cooling, the liquid water falls out of equilibrium whereby the temperature dependence of its relaxation time is predicted to change from super-Arrhenius to Arrhenius. A consequence of this crossover is that the location of the apparent glass transition temperature depends logarithmically on cooling rate. Accompanying vitrification is the emergence of a dynamical length-scale, the size of which depends on the cooling rate and varies between angstroms and tens of nanometers. While this protocol dependence clarifies a number of previous experimental observations for amorphous ice, the arguments are general and can be extended to other glass forming liquids.

  11. The length and time scales of water's glass transitions.

    Science.gov (United States)

    Limmer, David T

    2014-06-07

    Using a general model for the equilibrium dynamics of supercooled liquids, I compute from molecular properties the emergent length and time scales that govern the nonequilibrium relaxation behavior of amorphous ice prepared by rapid cooling. Upon cooling, the liquid water falls out of equilibrium whereby the temperature dependence of its relaxation time is predicted to change from super-Arrhenius to Arrhenius. A consequence of this crossover is that the location of the apparent glass transition temperature depends logarithmically on cooling rate. Accompanying vitrification is the emergence of a dynamical length-scale, the size of which depends on the cooling rate and varies between angstroms and tens of nanometers. While this protocol dependence clarifies a number of previous experimental observations for amorphous ice, the arguments are general and can be extended to other glass forming liquids.

  12. Calorimetric study of water's two glass transitions in the presence of LiCl

    Science.gov (United States)

    Ruiz, Guadalupe N.; Amann-Winkel, Katrin; Bove, Livia E.; Corti, Horacio R.

    2018-01-01

    A DSC study of dilute glassy LiCl aqueous solutions in the water-dominated regime provides direct evidence of a glass-to-liquid transition in expanded high density amorphous (eHDA)-type solutions. Similarly, low density amorphous ice (LDA) exhibits a glass transition prior to crystallization to ice Ic. Both glass transition temperatures are independent of the salt concentration, whereas the magnitude of the heat capacity increase differs. By contrast to pure water, the glass transition endpoint for LDA can be accessed in LiCl aqueous solutions above 0.01 mole fraction. Furthermore, we also reveal the endpoint for HDA's glass transition, solving the question on the width of both glass transitions. This suggests that both equilibrated HDL and LDL can be accessed in dilute LiCl solutions, supporting the liquid–liquid transition scenario to understand water's anomalies. PMID:29442107

  13. Measurement of the volatility and glass transition temperatures of glasses produced during the DWPF startup test program

    International Nuclear Information System (INIS)

    Marra, J.C.; Harbour, J.R.

    1995-01-01

    The Defense Waste Processing Facility (DWPF) will immobilize high-level radioactive waste currently stored in underground tanks at the Savannah River Site by incorporating the waste into a glass matrix. The molten waste glass will be poured into stainless steel canisters which will be welded shut to produce the final waste form. One specification requires that any volatiles produced as a result of accidentally heating the waste glass to the glass transition temperature be identified. Glass samples from five melter campaigns, run as part of the DWPF Startup Test Program, were analyzed to determine glass transition temperatures and to examine the volatilization (by weight loss). Glass transition temperatures (T g ) for the glasses, determined by differential scanning calorimetry (DSC), ranged between 445 C and 474 C. Thermogravimetric analysis (TGA) scans showed that no overall weight loss occurred in any of the glass samples when heated to 500 C. Therefore, no volatility will occur in the final glass product when heated up to 500 C

  14. Oxidation feature and diffusion mechanism of Zr-based metallic glasses near the glass transition point

    Science.gov (United States)

    Hu, Zheng; Lei, Xianqi; Wang, Yang; Zhang, Kun

    2018-03-01

    The oxidation behaviors of as-cast, pre-deformed, and crystallized Zr47.9Ti0.3Ni3.1Cu39.3Al9.4 metallic glasses (MGs) were studied near the glass transition point. The oxidation kinetics of the crystallized MGs followed a parabolic-rate law, and the as-cast and pre-deformed MGs exerted a typical two-stage behavior above the glass transition temperature (T g). Most interesting, pre-deformed treatment can significantly improve the oxidation rate of MGs, as the initial oxidation appeared earlier than for the as-cast MGs, and was accompanied by much thicker oxide scale. The EDS and XPS results showed that the metal Al acted as the preferred scavenger that absorbed intrinsic oxygen in the near-surface region of as-cast MGs. However, a homogeneous mixed layer without Al was observed in the pre-deformed MGs. We speculated the accelerated diffusion of other elements in the MGs was due to the local increase in the free volume and significant shear-induced dilation of the local structure. The results from this study demonstrate that MGs exhibit controllable atomic diffusion during the oxidation process, which can facilitate use in super-cooled liquid region applications.

  15. Thermal conductivity of Glycerol's liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures.

    Science.gov (United States)

    Andersson, Ove; Johari, G P

    2016-02-14

    To investigate the effects of local density fluctuations on phonon propagation in a hydrogen bonded structure, we studied the thermal conductivity κ of the crystal, liquid, and glassy states of pure glycerol as a function of the temperature, T, and the pressure, p. We find that the following: (i) κcrystal is 3.6-times the κliquid value at 140 K at 0.1 MPa and 2.2-times at 290 K, and it varies with T according to 138 × T(-0.95); (ii) the ratio κliquid (p)/κliquid (0.1 MPa) is 1.45 GPa(-1) at 280 K, which, unexpectedly, is about the same as κcrystal (p)/κcrystal (0.1 MPa) of 1.42 GPa(-1) at 298 K; (iii) κglass is relatively insensitive to T but sensitive to the applied p (1.38 GPa(-1) at 150 K); (iv) κglass-T plots show an enhanced, pressure-dependent peak-like feature, which is due to the glass to liquid transition on heating; (v) continuous heating cold-crystallizes ultraviscous glycerol under pressure, at a higher T when p is high; and (vi) glycerol formed by cooling at a high p and then measured at a low p has a significantly higher κ than the glass formed by cooling at a low p. On heating at a fixed low p, its κ decreases before its glass-liquid transition range at that p is reached. We attribute this effect to thermally assisted loss of the configurational and vibrational instabilities of a glass formed at high p and recovered at low p, which is different from the usual glass-aging effect. While the heat capacity, entropy, and volume of glycerol crystal are less than those for its glass and liquid, κcrystal of glycerol, like its elastic modulus and refractive index, is higher. We discuss these findings in terms of the role of fluctuations in local density and structure, and the relations between κ and the thermodynamic quantities.

  16. Characterization of the hidden glass transition of amorphous cyclomaltoheptaose.

    Science.gov (United States)

    Tabary, Nicolas; Mahieu, Aurélien; Willart, Jean-François; Dudognon, Emeline; Danède, Florence; Descamps, Marc; Bacquet, Maryse; Martel, Bernard

    2011-10-18

    An amorphous solid of cyclomaltoheptaose (β-cyclodextrin, β-CD) was formed by milling its crystalline form using a high-energy planetary mill at room temperature. The glass transition of this amorphous solid was found to occur above the thermal degradation point of the material preventing its direct observation and thus its full characterization. The corresponding glass transition temperature (T(g)) and the ΔC(p) at T(g) have, however, been estimated by extrapolation of T(g) and ΔC(p) of closely related amorphous compounds. These compounds include methylated β-CD with different degrees of substitution and molecular alloys obtained by co-milling β-CD and methylated β-CD (DS 1.8) at different ratios. The physical characterization of the amorphous states have been performed by powder X-ray diffraction and differential scanning calorimetry, while the chemical integrity of β-CD upon milling was checked by NMR spectroscopy and mass spectrometry. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Pressure dependence of glass transition in As2Te3 glass.

    Science.gov (United States)

    Ramesh, K

    2014-07-24

    Amorphous solids prepared from their melt state exhibit glass transition phenomenon upon heating. Viscosity, specific heat, and thermal expansion coefficient of the amorphous solids show rapid changes at the glass transition temperature (Tg). Generally, application of high pressure increases the Tg and this increase (a positive dT(g)/dP) has been understood adequately with free volume and entropy models which are purely thermodynamic in origin. In this study, the electrical resistivity of semiconducting As(2)Te(3) glass at high pressures as a function of temperature has been measured in a Bridgman anvil apparatus. Electrical resistivity showed a pronounced change at Tg. The Tg estimated from the slope change in the resistivity-temperature plot shows a decreasing trend (negative dT(g)/dP). The dT(g)/dP was found to be -2.36 °C/kbar for a linear fit and -2.99 °C/kbar for a polynomial fit in the pressure range 1 bar to 9 kbar. Chalcogenide glasses like Se, As(2)Se(3), and As(30)Se(30)Te(40) show a positive dT(g)/dP which is very well understood in terms of the thermodynamic models. The negative dT(g)/dP (which is generally uncommon in liquids) observed for As(2)Te(3) glass is against the predictions of the thermodynamic models. The Adam-Gibbs model of viscosity suggests a direct relationship between the isothermal pressure derivative of viscosity and the relaxational expansion coefficient. When the sign of the thermal expansion coefficient is negative, dT(g)/dP = Δk/Δα will be less than zero, which can result in a negative dT(g)/dP. In general, chalcogenides rich in tellurium show a negative thermal expansion coefficient (NTE) in the supercooled and stable liquid states. Hence, the negative dT(g)/dP observed in this study can be understood on the basis of the Adams-Gibbs model. An electronic model proposed by deNeufville and Rockstad finds a linear relation between Tg and the optical band gap (Eg) for covalent semiconducting glasses when they are grouped

  18. A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates.

    Science.gov (United States)

    Andersson, Ove; Häussermann, Ulrich

    2018-04-19

    Type II clathrate hydrates (CHs) M·17 H 2 O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to ∼1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass-liquid-glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.

  19. Breaking Through the Glass Ceiling: Recent Experimental Approaches to Probe the Properties of Supercooled Liquids near the Glass Transition.

    Science.gov (United States)

    Smith, R Scott; Kay, Bruce D

    2012-03-15

    Experimental measurements of the properties of supercooled liquids at temperatures near their glass transition temperatures, Tg, are requisite for understanding the behavior of glasses and amorphous solids. Unfortunately, many supercooled molecular liquids rapidly crystallize at temperatures far above their Tg, making such measurements difficult to nearly impossible. In this Perspective, we discuss some recent alternative approaches to obtain experimental data in the temperature regime near Tg. These new approaches may yield the additional experimental data necessary to test current theoretical models of the dynamical slowdown that occurs in supercooled liquids approaching the glass transition.

  20. Glass transition behavior and crystallization kinetics of Cu0.3(SSe20)0.7 chalcogenide glass

    International Nuclear Information System (INIS)

    Soliman, A.A.

    2005-01-01

    The glass transition behavior and crystallization kinetics of Cu 0.3 (SSe 20 ) 0.7 chalcogenide glass were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD). Two crystalline phases (SSe 20 and Cu 2 Se) were identified after annealing the glass at 773 K for 24 h. The activation energy of the glass transition (E g ), the activation energy of crystallization (E c ), the Avrami exponent (n) and the dimensionality of growth (m) were determined. Results indicate that this glass crystallizes by a two-stage bulk crystallization process upon heating. The first transformation, in which SSe 20 precipitates from the amorphous matrix with a three-dimensional crystal growth. The second transformation, in which the residual amorphous phase transforms into Cu 2 Se compound with a two-dimensional crystal growth

  1. Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water

    Science.gov (United States)

    Giovambattista, Nicolas; Loerting, Thomas; Lukanov, Boris R.; Starr, Francis W.

    2012-01-01

    Water has multiple glassy states, often called amorphous ices. Low-density (LDA) and high-density (HDA) amorphous ice are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. Direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we explore the implications of a LLPT on the pressure dependence of Tg(P) for LDA and HDA by performing computer simulations of two water models – one with a LLPT, and one without. In the absence of a LLPT, Tg(P) for all glasses nearly coincide. When there is a LLPT, different glasses exhibit dramatically different Tg(P) which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario including a LLPT. PMID:22550566

  2. Simultaneous Determination of Glass Transition Temperatures of Several Polymers.

    Science.gov (United States)

    He, Jiang; Liu, Wei; Huang, Yao-Xiong

    2016-01-01

    A simple and easy optical method is proposed for the determination of glass transition temperature (Tg) of polymers. Tg was determined using the technique of microsphere imaging to monitor the variation of the refractive index of polymer microsphere as a function of temperature. It was demonstrated that the method can eliminate most thermal lag and has sensitivity about six fold higher than the conventional method in Tg determination. So the determined Tg is more accurate and varies less with cooling/heating rate than that obtained by conventional methods. The most attractive character of the method is that it can simultaneously determine the Tg of several polymers in a single experiment, so it can greatly save experimental time and heating energy. The method is not only applicable for polymer microspheres, but also for the materials with arbitrary shapes. Therefore, it is expected to be broadly applied to different fundamental researches and practical applications of polymers.

  3. Glass transition and intermixing of amorphous water and methanol

    International Nuclear Information System (INIS)

    Souda, Ryutaro

    2004-01-01

    The diffusion of molecules in amorphous water and methanol films has been investigated on the basis of time-of-flight secondary ion mass spectrometry as a function of temperature. The glass-liquid transition of the amorphous water film occurs at 130-145 K as confirmed from the surface segregation of embedded methanol molecules. The morphology of the pure amorphous water film changes drastically at 160 K as a consequence of dewetting induced by the surface tension and the strongly decreased viscosity of the film. The morphology of the amorphous methanol film changes at 115 K following the self-diffusion onset at 80 K. The binary films of water and heavy methanol are intermixed completely at 136 K as evidenced by the occurrence of the H/D exchange

  4. Molecular modeling of polycarbonate materials: Glass transition and mechanical properties

    Science.gov (United States)

    Palczynski, Karol; Wilke, Andreas; Paeschke, Manfred; Dzubiella, Joachim

    2017-09-01

    Linking the experimentally accessible macroscopic properties of thermoplastic polymers to their microscopic static and dynamic properties is a key requirement for targeted material design. Classical molecular dynamics simulations enable us to study the structural and dynamic behavior of molecules on microscopic scales, and statistical physics provides a framework for relating these properties to the macroscopic properties. We take a first step toward creating an automated workflow for the theoretical prediction of thermoplastic material properties by developing an expeditious method for parameterizing a simple yet surprisingly powerful coarse-grained bisphenol-A polycarbonate model which goes beyond previous coarse-grained models and successfully reproduces the thermal expansion behavior, the glass transition temperature as a function of the molecular weight, and several elastic properties.

  5. Influence of entanglements on glass transition temperature of polystyrene

    Science.gov (United States)

    Ougizawa, Toshiaki; Kinugasa, Yoshinori

    2013-03-01

    Chain entanglement is essential behavior of polymeric molecules and it seems to affect many physical properties such as not only viscosity of melt state but also glass transition temperature (Tg). But we have not attained the quantitative estimation because the entanglement density is considered as an intrinsic value of the polymer at melt state depending on the chemical structure. Freeze-drying method is known as one of the few ways to make different entanglement density sample from dilute solution. In this study, the influence of entanglements on Tg of polystyrene obtained by the freeze-dried method was estimated quantitatively. The freeze-dried samples showed Tg depression with decreasing the concentration of precursor solution due to the lower entanglement density and their depressed Tg would be saturated when the almost no intermolecular entanglement was formed. The molecular weight dependence of the maximum value of Tg depression was discussed.

  6. Ferromagnetism and spin glass ordering in transition metal alloys (invited)

    Science.gov (United States)

    Crane, S.; Carnegie, D. W., Jr.; Claus, H.

    1982-03-01

    Magnetic properties of transition metal alloys near the percolation threshold are often complicated by metallurgical effects. Alloys like AuFe, VFe, CuNi, RhNi, and PdNi are in general not random solid solutions but have various degrees of atomic clustering or short-range order (SRO), depending on the heat treatment. First, it is shown how the magnetic ordering temperature of these alloys varies with the degree of clustering or SRO. Second, by systematically changing this degree of clustering or SRO, important information can be obtained about the magnetic phase diagram. In all these alloys below the percolation limit, the onset of ferromagnetic order is probably preceded by a spin glass-type ordering. However, details of the magnetic phase diagram near the critical point can be quite different alloy systems.

  7. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 2 ... Spin glasses; quantum phase transition; ferromagnetism; electron gas. ... We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent ...

  8. Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water

    Science.gov (United States)

    Giovambattista, Nicolas

    2013-03-01

    Most liquids can form a single glass or amorphous state when cooled sufficiently fast (in order to prevent crystallization). However, there are a few substances that are relevant to scientific and technological applications which can exist in at least two different amorphous states, a property known as polyamorphism. Examples include silicon, silica, and in particular, water. In the case of water, experiments show the existence of a low-density (LDA) and high-density (HDA) amorphous ice that are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation evolves into a first-order liquid-liquid phase transition (LLPT) at temperatures above the glass transition temperature Tg. However, obtaining direct experimental evidence of the LLPT has been challenging since the LLPT occurs at conditions where water rapidly crystallizes. In this talk, I will (i) discuss the general phenomenology of polyamorphism in water and its implications, and (ii) explore the effects of a LLPT on the pressure dependence of Tg(P) for LDA and HDA. Our study is based on computer simulations of two water models - one with a LLPT (ST2 model), and one without (SPC/E model). In the absence of a LLPT, Tg(P) for all glasses nearly coincide. Instead, when there is a LLPT, different glasses exhibit dramatically different Tg(P) loci which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario that includes a LLPT (ST2 model) and hence, our results support the view that a LLPT may exist for the case of water.

  9. The structural origin of the hard-sphere glass transition in granular packing.

    Science.gov (United States)

    Xia, Chengjie; Li, Jindong; Cao, Yixin; Kou, Binquan; Xiao, Xianghui; Fezzaa, Kamel; Xiao, Tiqiao; Wang, Yujie

    2015-09-28

    Glass transition is accompanied by a rapid growth of the structural relaxation time and a concomitant decrease of configurational entropy. It remains unclear whether the transition has a thermodynamic origin, and whether the dynamic arrest is associated with the growth of a certain static order. Using granular packing as a model hard-sphere glass, we show the glass transition as a thermodynamic phase transition with a 'hidden' polytetrahedral order. This polytetrahedral order is spatially correlated with the slow dynamics. It is geometrically frustrated and has a peculiar fractal dimension. Additionally, as the packing fraction increases, its growth follows an entropy-driven nucleation process, similar to that of the random first-order transition theory. Our study essentially identifies a long-sought-after structural glass order in hard-sphere glasses.

  10. A thermally tunable inverse opal photonic crystal for monitoring glass transition.

    Science.gov (United States)

    Sun, Liguo; Xie, Zhuoying; Xu, Hua; Xu, Ming; Han, Guozhi; Wang, Cheng; Bai, Xuduo; Gu, ZhongZe

    2012-03-01

    An optical method was developed to monitor the glass transition of the polymer by taking advantage of reflection spectrum change of the thermally tunable inverse opal photonic crystal. The thermally tunable photonic bands of the polymer inverse opal photonic crystal were traceable to the segmental motion of macromolecules, and the segmental motion was temperature dependent. By observing the reflection spectrum change of the polystyrene inverse opal photonic crystal during thermal treatment, the glass transition temperature of polystyrene was gotten. Both changes of the position and intensity of the reflection peak were observed during the glass transition process of the polystyrene inverse opal photonic crystal. The optical change of inverse opal photonic crystal was so large that the glass transition temperature could even be estimated by naked eyes. The glass transition temperature derived from this method was consistent with the values measured by differential scanning calorimeter.

  11. Kinetically controlled glass transition measurement of organic aerosol thin films using broadband dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    Y. Zhang

    2018-06-01

    Full Text Available Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud-forming (cloud condensation nuclei and ice nucleation capabilities of secondary organic aerosols (SOAs. The small size and relatively low mass concentration of SOAs in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adapted a new technique for measuring glass-forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE using electrostatic precipitation. Dielectric spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K that are used to calculate the glass transition temperatures for several cooling or heating rates. IDE-enabled broadband dielectric spectroscopy (BDS was successfully used to measure the kinetically controlled glass transition temperatures of aerosols consisting of glycerol and four other compounds with selected cooling and heating rates. The glass transition results agree well with available literature data for these five compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.

  12. Spatial glass transition temperature variations in polymer glass: application to a maltodextrin-water system.

    Science.gov (United States)

    van Sleeuwen, Rutger M T; Zhang, Suying; Normand, Valéry

    2012-03-12

    A model was developed to predict spatial glass transition temperature (T(g)) distributions in glassy maltodextrin particles during transient moisture sorption. The simulation employed a numerical mass transfer model with a concentration dependent apparent diffusion coefficient (D(app)) measured using Dynamic Vapor Sorption. The mass average moisture content increase and the associated decrease in T(g) were successfully modeled over time. Large spatial T(g) variations were predicted in the particle, resulting in a temporary broadening of the T(g) region. Temperature modulated differential scanning calorimetry confirmed that the variation in T(g) in nonequilibrated samples was larger than in equilibrated samples. This experimental broadening was characterized by an almost doubling of the T(g) breadth compared to the start of the experiment. Upon reaching equilibrium, both the experimental and predicted T(g) breadth contracted back to their initial value.

  13. Mobility restrictions and glass transition behaviour of an epoxy resin under confinement.

    Science.gov (United States)

    Djemour, A; Sanctuary, R; Baller, J

    2015-04-07

    Confinement can have a big influence on the dynamics of glass formers in the vicinity of the glass transition. Already 40 to 50 K above the glass transition temperature, thermal equilibration of glass formers can be strongly influenced by the confining substrate. We investigate the linear thermal expansion and the specific heat capacity cp of an epoxy resin (diglycidyl ether of bisphenol A, DGEBA) in a temperature interval of 120 K around the glass transition temperature. The epoxy resin is filled into controlled pore glasses with pore diameters between 4 and 111 nm. Since DGEBA can form H-bonds with silica surfaces, we also investigate the influence of surface silanization of the porous substrates. In untreated substrates a core/shell structure of the epoxy resin can be identified. The glass transition behaviours of the bulk phase and that of the shell phase are different. In silanized substrates, the shell phase disappears. At a temperature well above the glass transition, a second transition is found for the bulk phase - both in the linear expansion data as well as in the specific heat capacity. The cp data do not allow excluding the glass transition of a third phase as being the cause for this transition, whereas the linear expansion data do so. The additional transition temperature is interpreted as a separation between two regimes: above this temperature, macroscopic flow of the bulk phase inside the porous structure is possible to balance the mismatch of thermal expansion coefficients between DGEBA and the substrate. Below the transition temperature, this degree of freedom is hindered by geometrical constraints of the porous substrates. Moreover, this second transition could also be found in the linear expansion data of the shell phase.

  14. Long-wavelength fluctuations and the glass transition in two dimensions and three dimensions.

    Science.gov (United States)

    Vivek, Skanda; Kelleher, Colm P; Chaikin, Paul M; Weeks, Eric R

    2017-02-21

    Phase transitions significantly differ between 2D and 3D systems, but the influence of dimensionality on the glass transition is unresolved. We use microscopy to study colloidal systems as they approach their glass transitions at high concentrations and find differences between two dimensions and three dimensions. We find that, in two dimensions, particles can undergo large displacements without changing their position relative to their neighbors, in contrast with three dimensions. This is related to Mermin-Wagner long-wavelength fluctuations that influence phase transitions in two dimensions. However, when measuring particle motion only relative to their neighbors, two dimensions and three dimensions have similar behavior as the glass transition is approached, showing that the long-wavelength fluctuations do not cause a fundamental distinction between 2D and 3D glass transitions.

  15. Silk fibroin gelation via non-solvent induced phase separation

    Czech Academy of Sciences Publication Activity Database

    Kasoju, Naresh; Hawkins, N.; Pop-Georgievski, Ognen; Kubies, Dana; Vollrath, F.

    2016-01-01

    Roč. 4, č. 3 (2016), s. 460-473 ISSN 2047-4830 R&D Projects: GA MŠk(CZ) EE2.3.30.0029; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : silk fibroin * non-solvent induced phase separation * desolvation Subject RIV: CE - Biochemistry Impact factor: 4.210, year: 2016

  16. Analysis of early medieval glass beads - Glass in the transition period

    Energy Technology Data Exchange (ETDEWEB)

    Smit, Ziga, E-mail: ziga.smit@ijs.si [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana (Slovenia); Jozef Stefan Institute, Jamova 39, P.O.B. 3000, SI-1001 Ljubljana (Slovenia); Knific, Timotej [National Museum of Slovenia, Presernova 20, SI-1000 Ljubljana (Slovenia); Jezersek, David [Jozef Stefan Institute, Jamova 39, P.O.B. 3000, SI-1001 Ljubljana (Slovenia); Istenic, Janka [National Museum of Slovenia, Presernova 20, SI-1000 Ljubljana (Slovenia)

    2012-05-01

    Glass beads from graves excavated in Slovenia and dated archaeologically to the 7th-10th century AD were analysed by the combined PIXE-PIGE method. The results indicate two groups of glass; natron glass made in the Roman tradition and glass made with alkalis from the ash of halophytic plants, which gradually replaced natron glass after c. 800 AD. The alkalis used in the second group of glass seem to be in close relation to a variant of the Venetian white glass that appeared several centuries later. The origin of this glass may be traced to glass production in Mesopotamia and around the Aral Sea. All the mosaic beads with eye decoration, as well as most of the drawn-segmented and drawn-cut beads analysed, are of plant-ash glass, which confirms their supposed oriental origin.

  17. Optical transitions of Ho(3+) in oxyfluoride glasses and upconversion luminescence of Ho(3+)/Yb(3+)-codoped oxyfluoride glasses.

    Science.gov (United States)

    Feng, Li; Wu, Yinsu

    2015-05-05

    Optical properties of Ho(3+)-doped SiO2-BaF2-ZnF2 glasses have been investigated on the basis of the Judd-Ofelt theory. Judd-Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Ho(3+)/Yb(3+)-codoped SiO2-BaF2-ZnF2 glasses under 980nm excitation. The effects of composition, concentration of the doping ions, and excitation pump power on the upconversion emissions were also systematically studied. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Pair distribution function and its relation to the glass transition in an amorphous alloy

    International Nuclear Information System (INIS)

    Basak, S.; Clarke, R.; Nagel, S.R.

    1979-01-01

    Data for the pair distribution function g (r) are presented as a function of temperature for amorphous Nb/sub 0.4/Ni/sub 0.6/. We show, based on a simple model, that g (r) varies linearly with T over a wide temperature range in the glass as was found empirically by Wendt and Abraham. We also find that in our glass the behavior of g (r) near the glass transition is, within experimental error, similar to what they found in their Monte Carlo calculation. We interpret the deviation from linearity at the glass transition as due to the onset of diffusive motion of the atoms

  19. Magnetic properties of 3d-transition metal and rare earth fluoride glasses

    International Nuclear Information System (INIS)

    Renard, J.P.; Dupas, C.; Velu, E.; Jacobini, C.; Fonteneau, G.; Lucas, J.

    1981-01-01

    The ac susceptibility of fluoride glasses in the ternary systems PbF 2 -MnF 2 -FeF 3 , ThF 4 -BaF 2 -MnF 2 , ZnF 2 -BaF 2 -RF 3 (R = Dy-Ho) has been studied down to 0.3 K. The susceptibility of rare earth glasses exhibits a broad maximum strongly dependent on the measuring frequency ν while a spin glass transition with a sharp susceptibility cusp nearly independent on ν is observed in 3d-transition metal glasses. Magnetic after effects are observed below the spin freezing temperature. (orig.)

  20. Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition Time of Polydextrose.

    Science.gov (United States)

    Buehler, Martin G; Kindle, Michael L; Carter, Brady P

    2015-06-01

    Dielectric relaxation spectroscopy was used to characterize the glass transition time, tg , of polydextrose, where the glass transition temperature, Tg , and water activity, aw (relative humidity), were held constant during polydextrose relaxation. The tg was determined from a shift in the peak frequency of the imaginary capacitance spectrum with time. It was found that when the peak frequency reaches 30 mHz, polydextrose undergoes glass transition. Glass transition time, tg , is the time for polydextrose to undergo glass transition at a specific Tg and aw . Results lead to a modified state diagram, where Tg is depressed with increasing aw . This curve forms a boundary: (a) below the boundary, polydextrose does not undergo glass transition and (b) above the boundary, polydextrose rapidly undergoes glass transition. As the boundary curve is specified by a tg value, it can assist in the selection of storage conditions. An important point on the boundary curve is at aw = 0, where Tg0 = 115 °C. The methodology can also be used to calculate the stress-relaxation viscosity of polydextrose as a function of Tg and aw , which is important when characterizing the flow properties of polydextrose initially in powder form. © 2015 Institute of Food Technologists®

  1. Experimental and computational prediction of glass transition temperature of drugs.

    Science.gov (United States)

    Alzghoul, Ahmad; Alhalaweh, Amjad; Mahlin, Denny; Bergström, Christel A S

    2014-12-22

    Glass transition temperature (Tg) is an important inherent property of an amorphous solid material which is usually determined experimentally. In this study, the relation between Tg and melting temperature (Tm) was evaluated using a data set of 71 structurally diverse druglike compounds. Further, in silico models for prediction of Tg were developed based on calculated molecular descriptors and linear (multilinear regression, partial least-squares, principal component regression) and nonlinear (neural network, support vector regression) modeling techniques. The models based on Tm predicted Tg with an RMSE of 19.5 K for the test set. Among the five computational models developed herein the support vector regression gave the best result with RMSE of 18.7 K for the test set using only four chemical descriptors. Hence, two different models that predict Tg of drug-like molecules with high accuracy were developed. If Tm is available, a simple linear regression can be used to predict Tg. However, the results also suggest that support vector regression and calculated molecular descriptors can predict Tg with equal accuracy, already before compound synthesis.

  2. Glass transition in thermosetting clay-nanocomposite polyurethanes

    Energy Technology Data Exchange (ETDEWEB)

    Corcione, C. Esposito [Dipartimento di Ingegneria dell' Innovazione, Universita del Salento, Via Monteroni 73100, Lecce (Italy)], E-mail: carola.corcione@unile.it; Maffezzoli, A. [Dipartimento di Ingegneria dell' Innovazione, Universita del Salento, Via Monteroni 73100, Lecce (Italy)

    2009-03-10

    In this work nanocomposite in a polyurethane (PU) matrix, using an organically modified montmorillonite (OMM), were studied. An amount of organoclay ranging from 2% up to 6% by volume was added to the polyol component of the resin before mixing with isocyanate. The basal distance of OMM before and after mixing with the polyol and after curing was characterized by X-ray diffraction. The glass transition temperature (T{sub g}) of PU nanocomposites, measured using differential scanning calorimeter, increases with increasing the volume fraction of OMM. On the other hand, the heat capacity increment, {delta}C{sub p}, decreases from that the unfilled PU to that of the sample with 5.7 vol.% of OMM. Therefore the rigid amorphous fraction of the PU nanocomposites increases with increasing volume fraction of OMM. Finally, a three-phase model similar to that applied to study semi-crystalline polymers, was used to analyze the intercalation of the PU chains between OMM lamellae. The definition of molecular cooperativity was discussed for these systems and the characteristic length of the cooperative region was determined, using Donth equation.

  3. Exploring the Origin of Fragile-to-Strong Transition in Some Glass-Forming Liquids

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Hu, L. N.

    2014-01-01

    , topological and thermodynamic changes causing this transition. The theory for describing the transition has not been fully established. In this paper, we summarize our current understanding of the fragile-to-strong transition in some glass-forming liquids basedon our two published papers and recent...

  4. X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

    Czech Academy of Sciences Publication Activity Database

    Harris, W.H.; Guillen, D.P.; Kloužek, Jaroslav; Pokorný, P.; Yano, T.; Lee, S.; Schweiger, M. J.; Hrma, P.

    2017-01-01

    Roč. 100, č. 9 (2017), s. 3883-3894 ISSN 0002-7820 Institutional support: RVO:67985891 Keywords : borosilicate glass * computed tomography * glass melting * morphology * nuclear waste * X-ray Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass OBOR OECD: Ceramics Impact factor: 2.841, year: 2016

  5. Radiation-Induced Fluidity and Glass-Liquid Transition in Irradiated Amorphous Materials

    International Nuclear Information System (INIS)

    Ojovan, M.I.

    2009-01-01

    This paper describes the fluidity behaviour of continuously irradiated glasses using the Congruent Bond Lattice model in which broken bonds 'configurons' facilitate the flow. Irradiation breaks the bonds creating configurons which at high concentrations provide the transition of material from the glassy to liquid state. An explicit equation of viscosity has been derived which gives results in agreement with experimental data. This equation provides correct viscosity data for non-irradiated materials and shows a significant increase of fluidity in radiation fields. It demonstrates a decrease of activation energy of flow for irradiated glasses. A simple equation for glass-transition temperature was also obtained which shows that irradiated glasses have lower glass transition temperatures and are readily transformed from glassy to liquid state e.g. fluidized in strong radiation fields. (authors)

  6. Discontinuity in Fast Dynamics at the Glass Transition of ortho-Terphenyl.

    Science.gov (United States)

    Hoffman, David J; Fayer, Michael D

    2017-11-16

    The dynamics of the molecular glass former ortho-terphenyl through the glass transition were observed with two-dimensional infrared vibrational spectroscopy measurements of spectral diffusion using the small probe molecule phenylselenocyanate. Although the slow diffusive motions were not visible on the experimental time scale, a picosecond-scale exponential relaxation was observed at temperatures from above to well below the glass transition temperature. The characteristic time scale has a smooth temperature dependence from the liquid into the glass phase, but the range of vibrational frequencies the probe samples displayed a discontinuity at the glass transition temperature. Complementary pump-probe experiments associate the observed motion with density fluctuations. The key features of the dynamics are reproduced with a simple corrugated well potential energy surface model. In addition, the temperature dependence of the homogeneous vibrational dephasing was found to have a T 2 functional form, where T is the absolute temperature.

  7. Stereodynamic insight into the thermal history effects on poly(vinyl chloride) calorimetric sub-glass and glass transitions as a fragile glass model.

    Science.gov (United States)

    Pin, Jean-Mathieu; Behazin, Ehsan; Misra, Manjusri; Mohanty, Amar

    2018-05-02

    The dynamic thermal history impact of poly(vinyl chloride) (PVC) has been explored for a wide range of pre-cooling rates, from 1 to 30 °C min-1. A first macroscopic insight into the dynamic thermal history influence has been highlighted through a decrease in the apparent activation energy (Eapp) in the first stage of the glass transition. The overall glass transition Eapp surface was successfully modeled in a polynomial fashion regarding the pre-cooling range. Raman scattering was used to associate the Eapp variations along the glass transition conversion with the stereochemistry evolution during the polymeric relaxation. Herein, the selection of atactic PVC as the polymer model permits us to monitor the glassy polymer segment stereodynamics during the heating ramp through the C-Cl stretching. The intermolecular H-Cl dipole interactions, as well as intramolecular conformational reorganizations among syndiotactic, isotactic and heterotactic polymer sequences, have been associated with non-cooperative and cooperative motions, i.e. the β- and α-process, respectively. The fruitful comparison of the two extreme values of the pre-cooling rates permits us to propose a thermokinetic scenario that explains the occurrence, intensity, and inter-dependence of β- and α-processes in the glassy state and during the glass transition. This scenario could potentially be generalized to all the other polymeric glass-formers.

  8. Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers

    International Nuclear Information System (INIS)

    Bouhadja, M.; Jakse, N.; Pasturel, A.

    2014-01-01

    Molecular dynamics simulations are used to study the structural and dynamic properties of calcium aluminosilicate, (CaO-Al 2 O 3 ) 1−x (SiO 2 ) x , glass formers along three joins, namely, R = 1, 1.57, and 3, in which the silica content x can vary from 0 to 1. For all compositions, we determined the glass-transition temperature, the abundances of the non-bridging oxygen, triclusters, and AlO 5 structural units, as well as the fragility from the temperature evolution of the α-relaxation times. We clearly evidence the role played by the non-bridging oxygen linked either to Al atoms or Si atoms in the evolution of the glass-transition temperature as well as of the fragility as a function of silica content along the three joins

  9. Glass transition and aging in dense suspensions of thermosensitive microgel particles

    NARCIS (Netherlands)

    Purnomo, E.H; van den Ende, Henricus T.M.; Vanapalli Veera, V.S.A.R.; Vanapalli, Srinivas; Mugele, Friedrich Gunther

    2008-01-01

    We report a thermosensitive microgel suspension that can be tuned reversibly between the glass state at low temperature and the liquid state at high temperature. Unlike hard spheres, we find that the glass transition for these suspensions is governed by both the volume fraction and the softness of

  10. Connection between slow and fast dynamics of molecular liquids around the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Dalle-Ferrier, Cecile; Frick, Bernhard

    2010-01-01

    The mean-square displacement (MSD) was measured by neutron scattering at various temperatures and pressures for a number of molecular glass-forming liquids. The MSD is invariant along the glass-transition line at the pressure studied, thus establishing an “intrinsic” Lindemann criterion for any...

  11. Reversibility and hysteresis of the sharp yielding transition of a colloidal glass under oscillatory shear

    NARCIS (Netherlands)

    Dang, M. T.; Denisov, D.; Struth, B.; Zaccone, A.; Schall, P.

    The mechanical response of glasses remains challenging to understand. Recent results indicate that the oscillatory rheology of soft glasses is accompanied by a sharp non-equilibrium transition in the microscopic dynamics. Here, we use simultaneous x-ray scattering and rheology to investigate the

  12. Characterization of frequency-dependent glass transition temperature by Vogel-Fulcher relationship

    International Nuclear Information System (INIS)

    Bai Yu; Jin Li

    2008-01-01

    The complex mechanical modulus of polymer and polymer based composite materials showed a frequency-dependent behaviour during glass transition relaxation, which was historically modelled by the Arrhenius equation. However, this might not be true in a broad frequency domain based on the experience from the frequency dependence of the complex dielectric permittivity, which resulted from the same glass transition relaxation as for the complex mechanical modulus. Considering a good correspondence between dielectric and mechanical relaxation during glass transition, the Vogel-Fulcher relationship, previously proposed for the frequency dependence of dielectric permittivity, is introduced for that of the mechanical modulus; and the corresponding static glass transition temperature (T f ) was first determined for polymer and polymer based composite materials. (fast track communication)

  13. Glass transition temperature of PMMA/modified alumina nanocomposite: Molecular dynamic study

    OpenAIRE

    Mohammadi, Maryam; Davoodi, Jamal; Javanbakht, Mahdi; Rezaei, Hamidreza

    2017-01-01

    In this study, the effect of alumina and modified alumina nanoparticles in a PMMA/alumina nanocomposite was investigated. To attain this goal, the glass transition behavior of poly methyl methacrylate (PMMA), PMMA/alumina and PMMA/hydroxylated alumina nanocomposites were investigated by molecular dynamic simulations (MD). All the MD simulations were performed using the Materials Studio 6.0 software package of Accelrys. To obtain the glass transition temperature, the variation of density vs. t...

  14. Glass Transition Temperature Measurement for Undercured Cyanate Ester Networks: Challenges, Tips, and Tricks (Briefing Charts)

    Science.gov (United States)

    2014-01-29

    DISTRIBUTION A: Approved for public release; distribution is unlimited. Thermosetting Polymers Have a TG Envelope – Not Just a TG 4 • The glass transition...glass transition temperature of a thermosetting polymer can vary over a wide range of temperatures depending on how the polymer is processed • A... thermosetting polymer with only one kind of network formation and negligible side reactions, the conversion may be determined at every point in the scan. • By

  15. Discontinuous and heterogeneous glass transition behavior of carbohydrate polymer-plasticizer systems.

    Science.gov (United States)

    Kawai, Kiyoshi; Hagura, Yoshio

    2012-07-01

    In order to understand the glass transition properties of carbohydrate polymer-plasticizer systems, glass transition temperatures of dextrin-glucose and dextrin-maltose systems were investigated systematically using differential scanning calorimetry. The onset (Tg(on)) and offset (Tg(off)) of the glass transition decreased with increasing plasticizer (glucose or maltose) content, and showed an abrupt depression at certain plasticizer content. The abrupt depression of Tg(off) occurred at higher plasticizer content than that of Tg(on). The glass transition was much broader for intermediate plasticizer content. From the enthalpy relaxation behavior of samples aged at various temperatures, it was found that two different glass transitions occurred contentiously in the broad glass transition. These results suggested that carbohydrate polymer-plasticizer systems can be classified into three regions: the entrapment of the plasticizer by the polymer, the formations of the polymer-plasticizer and plasticizer-rich domains, and the embedment of polymer into the plasticizer. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Thermalization calorimetry: A simple method for investigating glass transition and crystallization of supercooled liquids

    DEFF Research Database (Denmark)

    Jakobsen, Bo; Sanz, Alejandro; Niss, Kristine

    2016-01-01

    and their crystallization, e.g., for locating the glass transition and melting point(s), as well as for investigating the stability against crystallization and estimating the relative change in specific heat between the solid and liquid phases at the glass transition......We present a simple method for fast and cheap thermal analysis on supercooled glass-forming liquids. This “Thermalization Calorimetry” technique is based on monitoring the temperature and its rate of change during heating or cooling of a sample for which the thermal power input comes from heat...

  17. Numerical detection of the Gardner transition in a mean-field glass former.

    Science.gov (United States)

    Charbonneau, Patrick; Jin, Yuliang; Parisi, Giorgio; Rainone, Corrado; Seoane, Beatriz; Zamponi, Francesco

    2015-07-01

    Recent theoretical advances predict the existence, deep into the glass phase, of a novel phase transition, the so-called Gardner transition. This transition is associated with the emergence of a complex free energy landscape composed of many marginally stable sub-basins within a glass metabasin. In this study, we explore several methods to detect numerically the Gardner transition in a simple structural glass former, the infinite-range Mari-Kurchan model. The transition point is robustly located from three independent approaches: (i) the divergence of the characteristic relaxation time, (ii) the divergence of the caging susceptibility, and (iii) the abnormal tail in the probability distribution function of cage order parameters. We show that the numerical results are fully consistent with the theoretical expectation. The methods we propose may also be generalized to more realistic numerical models as well as to experimental systems.

  18. Predicting glass-to-glass and liquid-to-liquid phase transitions in supercooled water using classical nucleation theory

    Science.gov (United States)

    Tournier, Robert F.

    2018-01-01

    Glass-to-glass and liquid-to-liquid phase transitions are observed in bulk and confined water, with or without applied pressure. They result from the competition of two liquid phases separated by an enthalpy difference depending on temperature. The classical nucleation equation of these phases is completed by this quantity existing at all temperatures, a pressure contribution, and an enthalpy excess. This equation leads to two homogeneous nucleation temperatures in each liquid phase; the first one (Tn- below Tm) being the formation temperature of an "ordered" liquid phase and the second one corresponding to the overheating temperature (Tn+ above Tm). Thermodynamic properties, double glass transition temperatures, sharp enthalpy and volume changes are predicted in agreement with experimental results. The first-order transition line at TLL = 0.833 × Tm between fragile and strong liquids joins two critical points. Glass phase above Tg becomes "ordered" liquid phase disappearing at TLL at low pressure and at Tn+ = 1.302 × Tm at high pressure.

  19. A toy MCT model for multiple glass transitions: Double swallow tail singularity

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhov, V.N. [Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk 142190, Moscow region (Russian Federation); Moscow Institute of Physics and Technology, 141700 Moscow (Russian Federation); Tareyeva, E.E. [Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk 142190, Moscow region (Russian Federation)

    2014-11-07

    We propose a toy model to describe in the frame of Mode Coupling Theory multiple glass transitions. The model is based on the postulated simple form for static structure factor as a sum of two delta-functions. This form makes it possible to solve the MCT equations in almost analytical way. The phase diagram is governed by two swallow tails resulting from two A{sub 4} singularities and includes liquid–glass transition and multiple glasses. The diagram has much in common with those of binary and quasibinary systems. - Highlights: • A simple toy model is proposed for description of glass–glass transitions. • The static structure factor of the model has the form of a sum of delta-functions. • The phase diagram contains A{sub 4} bifurcation singularities and A{sub 3} end points. • The results can be applied for the qualitative description of quasibinary systems.

  20. Modeling glass transition and aging processes in nanocomposites and polymer thin films

    Science.gov (United States)

    Pryamitsyn, Victor; Ganesan, Venkat

    2010-03-01

    We use a lattice kinetic model of glass transition to study the role of confinement and the presence of nano-inclusions. We have studied freely suspended films of glass-formers and its nanocomposites with ``plastifying'' and ``hardening'' nanoparticles. Using our model we determine the thickness and nanoparticle load dependencies of the Kauzmann temperature T0 and the fragility parameter. We found the glass transition temperature increases with the thickness of the film and the volume fraction of ``hardening'' nanoparticles , while Tg decreases with increase in the loading of ``plastifying'' nanoparticles. We found that the isothermal free volume relaxation rate of the nanocomposite thin film, usually referred as an aging, correlates with the glass transition temperature shift. We also studied the relations between our lattice model and Curro's, Kovacs and Struik's phenomenological models of free volume reduction to deduce physical insights into the mechanisms governing aging processes in thin films and nanocomposites.

  1. On melting dynamics and the glass transition. II. Glassy dynamics as a melting process.

    Science.gov (United States)

    Krzakala, Florent; Zdeborová, Lenka

    2011-01-21

    There are deep analogies between the melting dynamics in systems with a first-order phase transition and the dynamics from equilibrium in super-cooled liquids. For a class of Ising spin models undergoing a first-order transition--namely p-spin models on the so-called Nishimori line--it can be shown that the melting dynamics can be exactly mapped to the equilibrium dynamics. In this mapping the dynamical--or mode-coupling--glass transition corresponds to the spinodal point, while the Kauzmann transition corresponds to the first-order phase transition itself. Both in mean field and finite dimensional models this mapping provides an exact realization of the random first-order theory scenario for the glass transition. The corresponding glassy phenomenology can then be understood in the framework of a standard first-order phase transition.

  2. Size and pressure effects on glass transition temperature of poly (methyl methacrylate) thin films

    International Nuclear Information System (INIS)

    Lang, X.Y.; Zhang, G.H.; Lian, J.S.; Jiang, Q.

    2006-01-01

    A simple and unified model, without any adjustable parameter, is developed for size and pressure effects on glass transition temperatures of nanopolymers. The model is based on a model for size dependent glass transition temperature of nanopolymer glasses under ambient pressure, and a pressure-dependent function of the root of mean-square displacement of atom vibration. It is found that the size- and pressure-dependent glass transition temperatures of free-standing films or supported films having weak interaction with substrates decreases with decreasing of pressure and size. However, the glass transition temperature of supported films having strong interaction with substrates increases with the increase of pressure and the decrease of size. The predicted results correspond with available experimental evidences for atactic-Poly (methyl methacrylate) thin films under hydrostatic pressure or under the pressure induced by supercritical fluid CO 2 . In addition, the predicted glass transition temperature of isotactic-Poly (methyl methacrylate) thin films under ambient pressure is consistent with available experimental evidences

  3. The electronic and optical properties of germanium tellurite glasses containing various transition metal oxides

    International Nuclear Information System (INIS)

    Khan, M.N.

    1988-01-01

    Various transition metal oxides, such as TiO 2 , V 2 O 5 , NiO, CuO, and ZnO are added to germanium-tellurite glass and measurements are reported of the electrical conductivity, density, optical absorption, infra-red absorption spectra, and electron spin resonance. It is found that the d.c. conductivity of glasses containing the same amount of V 2 O 5 is higher than that of germanium tellurite glasses containing a similar amount of other transition metal oxides, and is due to hopping between localized states. The optical absorption measurements show that the fundamental absorption edge is a function of glass composition and the optical absorption is due to forbidden indirect transitions. From the infra-red absorption spectra, it is found that the addition of transition metal oxides does not introduce any new absorption band in the infra-red spectrum of germanium tellurite glasses. A small shift of existing absorptions toward higher wave number is observed. The ESR measurements revealed that some transition metal ions are diamagnetic while others are paramagnetic in the glass network. (author)

  4. Exploration of a new method in determining the glass transition temperature of BMGs by electrical resistivity

    Science.gov (United States)

    Guo, Jing; Zu, Fangqiu; Chen, Zhihao; Zheng, Shubin; Yuan, Yuan

    2005-07-01

    Based on a brief retrospect of the method in establishing Tg of the bulk metallic glasses (BMGs), some perplexities concerning this are pointed out. With the experimental results of Zr-Al-Ni-Cu-X (Nb,Ti) BMGs, a electrical resistivity method is proposed to determine the glass transition temperature of BMGs. With the method, we define two kinds of characteristic temperature related to the glass transition, Tg-dep and Tg-int, respectively. By comparing Tg-dep and Tg-int with Tg determined by the DSC method, we have found that, for the same alloy at the same heating rate, Tg-dep is very close to Tg-onset while Tg-int is approximate to Tg-mid. As a method to determine the glass transition temperature, the electrical resistivity method has proved to be more convenient and practical in comparison with the DSC method, especially when the DSC curve cannot show the glass transition character of BMGs. In addition, we would emphasize that when we refer to Tg, it is necessary to expatiate on the way of denoting the glass transition temperature, such as Tg-dep or Tg-int ( Tg-onset or Tg-mid), and on the heating rate, in order to avoid ambiguity.

  5. Transition from glass to graphite in manufacture of composite aircraft structure

    Science.gov (United States)

    Buffum, H. E.; Thompson, V. S.

    1978-01-01

    The transition from fiberglass reinforced plastic composites to graphite reinforced plastic composites is described. Structural fiberglass design and manufacturing background are summarized. How this experience provides a technology base for moving into graphite composite secondary structure and then to composite primary structure is considered. The technical requirements that must be fulfilled in the transition from glass to graphite composite structure are also included.

  6. Glass Transition Temperature of Saccharide Aqueous Solutions Estimated with the Free Volume/Percolation Model.

    Science.gov (United States)

    Constantin, Julian Gelman; Schneider, Matthias; Corti, Horacio R

    2016-06-09

    The glass transition temperature of trehalose, sucrose, glucose, and fructose aqueous solutions has been predicted as a function of the water content by using the free volume/percolation model (FVPM). This model only requires the molar volume of water in the liquid and supercooled regimes, the molar volumes of the hypothetical pure liquid sugars at temperatures below their pure glass transition temperatures, and the molar volumes of the mixtures at the glass transition temperature. The model is simplified by assuming that the excess thermal expansion coefficient is negligible for saccharide-water mixtures, and this ideal FVPM becomes identical to the Gordon-Taylor model. It was found that the behavior of the water molar volume in trehalose-water mixtures at low temperatures can be obtained by assuming that the FVPM holds for this mixture. The temperature dependence of the water molar volume in the supercooled region of interest seems to be compatible with the recent hypothesis on the existence of two structure of liquid water, being the high density liquid water the state of water in the sugar solutions. The idealized FVPM describes the measured glass transition temperature of sucrose, glucose, and fructose aqueous solutions, with much better accuracy than both the Gordon-Taylor model based on an empirical kGT constant dependent on the saccharide glass transition temperature and the Couchman-Karasz model using experimental heat capacity changes of the components at the glass transition temperature. Thus, FVPM seems to be an excellent tool to predict the glass transition temperature of other aqueous saccharides and polyols solutions by resorting to volumetric information easily available.

  7. Pressure effect of glass transition temperature in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk metallic glass

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Roseker, W.; Sikorski, M.

    2004-01-01

    Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition was det...... range of 0-2.2 GPa. This method opens a possibility to study the pressure effect of glass transition process in glassy systems under high pressures (>1 GPa). (C) 2004 American Institute of Physics.......Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition...... was detected from the change of the slope of peak position as a function of temperature. It is found that the glass transition temperature increases with pressure by 4.4 K/GPa for the Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass, and the supercooled liquid range decreases with pressure by 2.9 K/GPa in a pressure...

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

    International Nuclear Information System (INIS)

    Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa

    2007-01-01

    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

  9. The extent of the glass transition from molecular simulation revealing an overcrank effect.

    Science.gov (United States)

    Godey, François; Fleury, Alexandre; Ghoufi, Aziz; Soldera, Armand

    2018-02-15

    A deep understanding of the transition between rubber and amorphous state characterized by a glass transition temperature, T g , is still a source of discussions. In this work, we highlight the role of molecular simulation in revealing explicitly this temperature dependent behavior. By reporting the specific volume, the thermal expansion coefficient and the heat capacity versus the temperature, we actually show that the glass transition domain extends to a greater range of temperature, compared with experiments. This significant enlargement width is due to the fast cooling rate, and actually explains the difficulty to locate T g . This result is the manifestation of an overcranking effect used by high-speed cameras to reveal slow-motion. Accordingly, atomistic simulation offers the significant opportunity to show that the transition from the rubber state to the glass phase should be detailed in terms of the degrees of freedom freeze. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  10. Impact of medium-range order on the glass transition in liquid Ni-Si alloys

    Science.gov (United States)

    Lü, Y. J.; Entel, P.

    2011-09-01

    We study the thermophysical properties and structure of liquid Ni-Si alloys using molecular dynamics simulations. The liquid Ni-5% and 10%Si alloys crystallize to form the face-centered cubic (Ni) at 900 and 850 K, respectively, and the glass transitions take place in Ni-20% and 25%Si alloys at about 700 K. The temperature-dependent self-diffusion coefficients and viscosities exhibit more pronounced non-Arrhenius behavior with the increase of Si content before phase transitions, indicating the enhanced glass-forming ability. These appearances of thermodynamic properties and phase transitions are found to closely relate to the medium-range order clusters with the defective face-centered cubic structure characterized by both local translational and orientational order. This locally ordered structure tends to be destroyed by the addition of more Si atoms, resulting in a delay of nucleation and even glass transition instead.

  11. Discontinuous nature of the repulsive-to-attractive colloidal glass transition.

    Science.gov (United States)

    van de Laar, T; Higler, R; Schroën, K; Sprakel, J

    2016-03-04

    In purely repulsive colloidal systems a glass transition can be reached by increasing the particle volume fraction beyond a certain threshold. The resulting glassy state is governed by configurational cages which confine particles and restrict their motion. A colloidal glass may also be formed by inducing attractive interactions between the particles. When attraction is turned on in a repulsive colloidal glass a re-entrant solidification ensues. Initially, the repulsive glass melts as free volume in the system increases. As the attraction strength is increased further, this weakened configurational glass gives way to an attractive glass in which motion is hindered by the formation of physical bonds between neighboring particles. In this paper, we study the transition from repulsive-to-attractive glasses using three-dimensional imaging at the single-particle level. We show how the onset of cage weakening and bond formation is signalled by subtle changes in local structure. We then demonstrate the discontinuous nature of the solid-solid transition, which is marked by a critical onset at a threshold bonding energy. Finally, we highlight how the interplay between bonding and caging leads to complex and heterogeneous dynamics at the microscale.

  12. Glass Transition Kinetics of 2714A amorphous alloy

    Science.gov (United States)

    Shanker Rao, T.; Lilly Shanker Rao, T.; Shaker, A. M.; Venkataraman, K.

    2018-03-01

    The present study is related to the kinetics of onset crystallization, Tx and peak crystallization Tp of cobalt based metallic glass 2714A (Co65Si15B14Fe4Ni2) using Differential Scanning Calorimetry (DSC). Non-isothermal measurements were performed at different heating rates (2, 4, 6, 8 and 10 K/min).The experimental results of the crystallization were studied by two most frequently used methods, i.e., Moynihan and Kissinger. The onset crystallization was also studied by VFT and Lasock’s approaches in addition to the above two methods. The activation energy of crystallization Ec was found to be 622.86 and 638.28 kJ/mol and Ex the activation energy of onset crystallization to be 676.34 and 688.93 kJ/mol respectively. Here Tx is used as a substitution of Tg to calculate the fragility index m of the cobalt based metallic glass in the absence of Tg. The fragility index, m which is a measure of glass forming ability (GFA) is also calculated and the value falls between 20 and 60. This indicates the studied metallic glass is an intermediate strong glass.

  13. Relationship between the shear viscosity and heating rate in metallic glasses below the glass transition

    International Nuclear Information System (INIS)

    Khonik, Vitaly A.; Kobelev, N. P.

    2008-01-01

    It has been shown that first-order irreversible structural relaxation with distributed activation energies must lead to a linear decrease of the logarithm of Newtonian shear viscosity with the logarithm of heating rate upon linear heating of glass. Such a behavior is indeed observed in the experiments on metallic glasses. Structural relaxation-induced viscous flow leads to infra-low-frequency Maxwell viscoelastic internal friction, which is predicted to increase with the heating rate

  14. Glass transition in thin supported polystyrene films probed by temperature-modulated ellipsometry in vacuum.

    Science.gov (United States)

    Efremov, Mikhail Yu; Kiyanova, Anna V; Last, Julie; Soofi, Shauheen S; Thode, Christopher; Nealey, Paul F

    2012-08-01

    Glass transition in thin (1-200 nm thick) spin-cast polystyrene films on silicon surfaces is probed by ellipsometry in a controlled vacuum environment. A temperature-modulated modification of the method is used alongside a traditional linear temperature scan. A clear glass transition is detected in films with thicknesses as low as 1-2 nm. The glass transition temperature (T(g)) shows no substantial dependence on thickness for coatings greater than 20 nm. Thinner films demonstrate moderate T(g) depression achieving 18 K for thicknesses 4-7 nm. Less than 4 nm thick samples are excluded from the T(g) comparison due to significant thickness nonuniformity (surface roughness). The transition in 10-20 nm thick films demonstrates excessive broadening. For some samples, the broadened transition is clearly resolved into two separate transitions. The thickness dependence of the glass transition can be well described by a simple 2-layer model. It is also shown that T(g) depression in 5 nm thick films is not sensitive to a wide range of experimental factors including molecular weight characteristics of the polymer, specifications of solvent used for spin casting, substrate composition, and pretreatment of the substrate surface.

  15. Optical properties of 3d transition metal ion-doped sodium borosilicate glass

    International Nuclear Information System (INIS)

    Wen, Hongli; Tanner, Peter A.

    2015-01-01

    Graphical abstract: Photographs of undoped (SiO 2 ) 50 (Na 2 O) 25 (B 2 O 3 ) 25 (SiNaB) glass and transition metal ion-doped (TM) 0.5 (SiO 2 ) 49.5 (Na 2 O) 25 (B 2 O 3 ) 25 glass samples. - Highlights: • 3d transition metal ion (from Ti to Zn) doped SiO 2 -Na 2 O-B 2 O 3 glasses. • Optical properties of doped glasses investigated. • V(IV,V); Cr(III, VI); Mn(II,III); Fe(II,III); Co(II); Ni(II); Cu(II) by XANES, DRS. • Strong visible absorption but only vanadium ion gives strong emission in glass. - Abstract: SiO 2 -Na 2 O-B 2 O 3 glasses doped with 3d-transition metal species from Ti to Zn were prepared by the melting-quenching technique and their optical properties were investigated. The X-ray absorption near edge spectra of V, Cr, and Mn-doped glasses indicate that the oxidation states of V(IV, V), Cr(III, VI) and Mn(II, III) exist in the studied glasses. The oxidation states revealed from the diffuse reflectance spectra of the glasses are V(IV, V), Cr(III, VI), Mn(III), Fe(II, III), Co(II), Ni(II), and Cu(II). Most of the 3d transition element ions exhibit strong absorption in the visible spectral region in the glass. Under ultraviolet excitation, the undoped sodium borosilicate glass produces weak and broad emission, while doping of vanadium introduces strong and broad emission due to the V(V) charge transfer transition. Only weak emission is observed from Ti(IV), Mn(II), Fe(III) and Cu(II), partly resulting from the strong electron–phonon coupling of the 3d-electrons and the relatively high phonon energy of the studied glass host, with the former leading to dominant nonradiative relaxation based on multiphonon processes for most of the 3d excited states

  16. Polymeric nanoparticles - Influence of the glass transition temperature on drug release.

    Science.gov (United States)

    Lappe, Svenja; Mulac, Dennis; Langer, Klaus

    2017-01-30

    The physico-chemical characterisation of nanoparticles is often lacking the determination of the glass transition temperature, a well-known parameter for the pure polymer carrier. In the present study the influence of water on the glass transition temperature of poly (DL-lactic-co-glycolic acid) nanoparticles was assessed. In addition, flurbiprofen and mTHPP as model drugs were incorporated in poly (DL-lactic-co-glycolic acid), poly (DL-lactic acid), and poly (L-lactic acid) nanoparticles. For flurbiprofen-loaded nanoparticles a decrease in the glass transition temperature was observed while mTHPP exerted no influence on this parameter. Based on this observation, the release behaviour of the drug-loaded nanoparticles was investigated at different temperatures. For all preparations an initial burst release was measured that could be attributed to the drug adsorbed to the large nanoparticle surface. At temperatures above the glass transition temperature an instant drug release of the nanoparticles was observed, while at lower temperatures less drug was released. It could be shown that the glass transition temperature of drug loaded nanoparticles in suspension more than the corresponding temperature of the pure polymer is the pivotal parameter when characterising a nanostructured drug delivery system. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

    Science.gov (United States)

    Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

    2016-01-13

    Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

  18. Structure and properties of transition metal-metalloid glasses based on refractory metals

    International Nuclear Information System (INIS)

    Johnson, W.L.; Williams, A.R.

    1979-01-01

    The structure and properties of several new transition metal-metalloid (TM/sub 1-x/M/sub x/) metallic glasses based on refractory transition metals (e.g. Mo, W, Ru etc.) have been systemically investigated as a function of composition. The structure of the alloys has been investigated by x-ray diffraction methods and measurements of superconducting properties, electrical resistivity, density, hardness, and mechanical behavior were made. These data are used in developing a novel description of the structure of TM/sub 1-x/M/sub x/ glasses. The experimental evidence suggests that an ideal amorphous phase forms at a specific composition x/sub c/ and that this phase has a well defined atomic short range order. For metallic glasses having x x/sub c/. This novel picture can explain the variation of many properties of these glasses with metalloid concentration

  19. Characterisation of the glass transition of an amorphous drug using modulated DSC.

    Science.gov (United States)

    Royall, P G; Craig, D Q; Doherty, C

    1998-07-01

    The use of modulated differential scanning calorimetry (MDSC) as a novel means of characterising the glass transition of amorphous drugs has been investigated, using the protease inhibitor saquinavir as a model compound. In particular, the effects of measuring variables (temperature cycling, scanning period, heating mode) have been examined. Saquinavir samples of known moisture content were examined using a TA Instruments 2920 MDSC at a heating rate of 2 degrees C/min and an amplitude of +/-0.159 degrees C with a period of 30 seconds. These conditions were used to examine the effects of cycling between - 50 degrees C and 150 degrees C. A range of periods between 20 and 50 seconds were then studied. Isothermal measurements were carried out between 85 degrees C and 120 degrees C using an amplitude of +/-0.159 degrees C with a period of 30 seconds. MDSC showed the glass transition of saquinavir (0.98 +/- 0.05%w/w moisture content) in isolation from the relaxation endotherm to give an apparent glass transition temperature of 107.0 degrees C +/- 0.4 degrees C. Subsequent temperature cycling gave reproducible glass transition temperatures of approximately 105 degrees C for both cooling and heating cycles. The enthalpic relaxation peak observed in the initial heating cycle had an additional contribution from a Tg "shift" effect brought about by the difference in response to the glass transition of the total and reversing heat flow signals. Isothermal studies yield a glass transition at 105.9 degrees C +/- 0.1 degrees C. MDSC has been shown to be capable of separating the glass transition of saquinavir from the relaxation endotherm, thereby facilitating measurement of this parameter without the need for temperature cycling. However, the Tg "shift" effect and the number of modulations through the transition should be taken into account to avoid drawing erroneous conclusions from the experimental data. MDSC has been shown to be an effective method of characterising the glass

  20. DWPF glass transition temperatures: What they are and why they are important

    International Nuclear Information System (INIS)

    Marra, S.L.; Jantzen, C.M.; Ramsey, A.A.

    1991-01-01

    The Defense Waste Processing Facility (DWPF) at the Savannah River Site will immobilize high-level radioactive liquid waste in borosilicate glass. The glass will be poured into stainless steel canisters for eventual disposal in a geologic repository. The Department of Energy has defined a set of requirements for the DWPF canistered waste form which must be met in order to assure compatibility with, and acceptance by, the repository. These requirements are the Waste Acceptance Preliminary Specifications (WAPS). The WAPS require DWPF to report glass transition temperatures for the projected range of compositions. This information will be used by the repository to establish waste package design limits

  1. Glass transition temperature of hard chairside reline materials after post-polymerisation treatments.

    Science.gov (United States)

    Urban, Vanessa M; Machado, Ana L; Alves, Marinês O; Maciel, Adeilton P; Vergani, Carlos E; Leite, Edson R

    2010-09-01

    This study evaluated the effect of post-polymerisation treatments on the glass transition temperature (T(g)) of five hard chairside reline materials (Duraliner II-D, Kooliner-K, New Truliner-N, Ufi Gel hard-U and Tokuso Rebase Fast-T). Specimens (10 x 10 x 1 mm) were made following the manufacturers' instructions and divided into three groups (n = 5). Control group specimens were left untreated. Specimens from the microwave group were irradiated with pre-determined power/time combinations, and specimens from the water-bath group were immersed in hot water at 55 degrees C for 10 min. Glass transition ( degrees C) was performed by differential scanning calorimetry. Data were analysed using anova, followed by post hoc Tukey's test (alpha = 0.05). Both post-polymerisation treatments promoted a significant (p glass transition of material Kooliner, with the effect being more pronounced for microwave irradiation.

  2. Effect of the glass transition temperature on alpha-amylase activity in a starch matrix.

    Science.gov (United States)

    Chaudhary, Vinita; Panyoyai, Naksit; Small, Darryl M; Shanks, Robert A; Kasapis, Stefan

    2017-02-10

    This study optimises a protocol for the estimation of α-amylase activity in a condensed starch matrix in the vicinity of the glass transition region. Enzymatic activity on the vitrified starch system was compared with that of a reference substrate, maltodextrin. The activity was assayed as the rate of release of reducing sugar using a dinitrosalicylic acid procedure. The condensed carbohydrate matrices served the dual purpose of acting as a substrate as well as producing a pronounced effect on the ability to enzymatic hydrolysis. Activation energies were estimated throughout the glass transition region of condensed carbohydrate preparations based on the concept of the spectroscopic shift factor. Results were used to demonstrate a considerable moderation by the mechanical glass transition temperature, beyond the expected linear effect of the temperature dependence, on the reaction rate of starch hydrolysis by α-amylase in comparison with the low-molecular weight chain of maltodextrin. Copyright © 2016. Published by Elsevier Ltd.

  3. Acrylate oligomers in ultraviolet cured PSA's glass transition, molecular weight versus peel strength

    International Nuclear Information System (INIS)

    Miller, H.C.

    1999-01-01

    Typically those not skilled in the art relate Glass Transition Temperature to Pressure Sensitive Adhesives. You need a low Tg material to prepare good pressure sensitive adhesives. This report deals with a wide range acrylate terminated oligomers in a standard formulation. Molecular weight, chemical structure variations are examined versus the Glass Transition of the oligomers and final peel strength. Each formulated adhesive will require unique oligomer properties to reach one hundred newtons per 100 millimeters (5.71 pounds per square inch) peel strength. Excellent peel strengths may be obtained with oligomer molecular weight ranging from six thousand to one thousand molecular weight and glass transition temperatures ranging from minus seventy four degrees centigrade up to thirteen degrees centigrade

  4. Resolving glass transition in Te-based phase-change materials by modulated differential scanning calorimetry

    Science.gov (United States)

    Chen, Yimin; Mu, Sen; Wang, Guoxiang; Shen, Xiang; Wang, Junqiang; Dai, Shixun; Xu, Tiefeng; Nie, Qiuhua; Wang, Rongping

    2017-10-01

    Glass transitions of Te-based phase-change materials (PCMs) were studied by modulated differential scanning calorimetry. It was found that both Ge2Sb2Te5 and GeTe are marginal glass formers with ΔT (= T x - T g) less than 2.1 °C when the heating rate is below 3 °C min-1. The fragilities of Ge2Sb2Te5 and GeTe can be estimated as 46.0 and 39.7, respectively, around the glass transition temperature, implying that a fragile-to-strong transition would be presented in such Te-based PCMs. The above results provide direct experimental evidence to support the investigation of crystallization kinetics in supercooled liquid PCMs.

  5. Thermodynamic aspects of the glass-rubber transition

    NARCIS (Netherlands)

    Staverman, A.J.

    1966-01-01

    In 1933 Ehren/est defined transitions in which not only the thermodynamical potential but also the specific volume and entropy of the two states are equal. For these transitions he derived three relations, between the differences of the coefficients of dilatation and of compressibility and the

  6. Glass transitions in one-, two-, three-, and four-dimensional binary Lennard-Jones systems

    Energy Technology Data Exchange (ETDEWEB)

    Bruening, Ralf; St-Onge, Denis A; Patterson, Steve [Physics Department, Mount Allison University, Sackville, NB, E4L 1E6 (Canada); Kob, Walter [Laboratoire des Colloides, Verres et Nanomateriaux, UMR5587, Universite Montpellier II and CNRS, 34095 Montpellier Cedex (France)], E-mail: rbruening@mta.ca

    2009-01-21

    We investigate the calorimetric liquid-glass transition by performing simulations of a binary Lennard-Jones mixture in one through four dimensions. Starting at a high temperature, the systems are cooled to T = 0 and heated back to the ergodic liquid state at constant rates. Glass transitions are observed in two, three and four dimensions as a hysteresis between the cooling and heating curves. This hysteresis appears in the energy and pressure diagrams, and the scanning rate dependence of the area and height of the hysteresis can be described using power laws. The one-dimensional system does not experience a glass transition but its specific heat curve resembles the shape of the D{>=}2 results in the supercooled liquid regime above the glass transition. As D increases, the radial distribution functions reflect reduced geometric constraints. Nearest neighbor distances become smaller with increasing D due to interactions between nearest and next-nearest neighbors. Simulation data for the glasses are compared with crystal and melting data obtained with a Lennard-Jones system with only one type of particle and we find that with increasing D crystallization becomes increasingly more difficult.

  7. The superspin glass transition in zinc ferrite nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Kaman, Ondřej; Kořínková, T.; Jirák, T.; Maryško, Miroslav; Veverka, Miroslav

    2015-01-01

    Roč. 117, č. 17 (2015), "17C706-1"-"17C706-4" ISSN 0021-8979 R&D Projects: GA ČR(CZ) GAP108/11/0807; GA ČR GAP204/10/0035 Institutional support: RVO:68378271 Keywords : superspin glass * zinc ferrite * doped magnetite * magnetic nanoparticles * thermal decomposition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.101, year: 2015

  8. Glass transition in the spin-density wave phase of (TMTSF)2PF6

    DEFF Research Database (Denmark)

    Lasjaunias, J.C.; Biljakovic, K.; Nad, F.

    1994-01-01

    We present the results of low frequency dielectric measurements and a detailed kinetic investigation of the specific heat anomaly in the spin-density wave phase of (TMTSF)(2)PF6 in the temperature range between 2 and 4 K. The dielectric relaxation shows a critical slowing down towards a ''static'......'' glass transition around 2 K. The jump in the specific heat in different controlled kinetic conditions shows all the characteristics of freezing in supercooled liquids. Both effects give direct evidence of a glass transition in the spin-density wave ground state....

  9. Superfluid/Bose-glass transition in one dimension

    Science.gov (United States)

    Ristivojevic, Zoran; Petković, Aleksandra; Le Doussal, Pierre; Giamarchi, Thierry

    2014-09-01

    We consider a one-dimensional system of interacting bosons in a random potential. At zero temperature, it can be either in the superfluid or in the insulating phase. We study the transition at weak disorder and moderate interaction. Using a systematic approach, we derive the renormalization group equations at two-loop order and discuss the phase diagram. We find the universal form of the correlation functions at the transitions and compute the logarithmic corrections to the main universal power-law behavior. In order to mimic large density fluctuations on a single site, we study a simplified model of disordered two-leg bosonic ladders with correlated disorder across the rung. Contrarily to the single-chain case, the latter system exhibits a transition between a superfluid and a localized phase where the exponents of the correlation functions at the transition do not take universal values.

  10. Anomalous Crystallization as a Signature of the Fragile-to-Strong Transition in Metallic Glass-Forming Liquids

    DEFF Research Database (Denmark)

    Yang, X.N.; Zhou, C.; Sun, Q.J.

    2014-01-01

    We study the fragile-to-strong (F−S) transition of metallic glass-forming liquids (MGFLs) by measuring the thermal response during annealing and dynamic heating of La55Al25Ni5Cu15 glass ribbons fabricated at different cooling rates. We find that the glasses fabricated in the intermediate regime o...

  11. Ultrasound-induced crystallization around the glass transition temperature for Pd40Ni40P20 metallic glass

    International Nuclear Information System (INIS)

    Ichitsubo, Tetsu; Matsubara, Eiichiro; Kai, Satoshi; Hirao, Masahiko

    2004-01-01

    We have found that crystallization of a Pd 40 Ni 40 P 20 bulk metallic glass is accelerated in the vicinity of the glass transition temperature T g when it is subjected to sub/low-MHz frequency ultrasonic vibration. Resonance frequencies and internal frictions have been measured with the electromagnetic acoustic resonance (EMAR) technique. In the initial heating process of an as-cast glassy sample, the resonance frequencies jump up just above T g under ultrasonic excitation, which is attributed to nano-crystallization that is confirmed by the X-ray diffraction profile. However, such a notable change is not observed without ultrasonic vibration. The irregular Λ-shaped internal-friction peaks are also observed prior to the abrupt crystallization. This rapid crystallization is considered to be caused by a stochastic resonance, in which the jump frequency of atoms matches the frequency of the interatomic-potential change by the ultrasonic vibration

  12. Effects of configurational changes on electrical resistivity during glass-liquid transition of two bulk metal-alloy glasses

    Energy Technology Data Exchange (ETDEWEB)

    Aji, D. P. B.; Johari, G. P., E-mail: joharig@mcmaster.ca [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

    2014-12-14

    Consequences of increase in structural fluctuations on heating Pd{sub 40}Ni{sub 10}Cu{sub 30}P{sub 20} and Zr{sub 46.75}Ti{sub 8.25}Cu{sub 7.5}Ni{sub 10}Be{sub 27.5} through their glass to liquid transition range were investigated by measuring the electrical resistivity, ρ, an electron scattering property. The temperature coefficient of resistivity (TCR = (1/ρ) dρ/dT) of the liquid and glassy states is negative. The plots of their ρ against T in the T{sub g} (glass to liquid transition) range show a gradual change in the slope similar to the change observed generally for the plots of the density, elastic modulus, and refractive index. As fluctuations in the melt structure involve fewer configurations on cooling, ρ increases. In the energy landscape description, the melt's structure explores fewer minima with decrease in T, vibrational frequencies increase, and electron scattering and ρ increase. Plots of (−dρ/dT) against T resemble the plot of the specific heat of other glasses and show a sub-T{sub g} feature and a rapid rise at T near T{sub g}. Analysis shows that the magnitude of negative TCR is dominated by change in the phonon characteristics, and configurational fluctuations make it more negative. The TCR of the liquid and glassy states seems qualitatively consistent with the variation in the structure factor in Ziman's model for pure liquid metals as extended by Nagel to metal alloys and used to explain the negative TCR of a two-component metal glass.

  13. Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

    DEFF Research Database (Denmark)

    Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

    2015-01-01

    Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...... at elastic stage. The concentrated stress in crystals at elastic stage provided adequate energy for the direct gamma-alpha phase transition under T-g. The force to promote the gamma-phase into a phase directly is insufficient at the yield stage and a transient phase as a compromise was formed. The transient...... phase was confirmed by DSC measurements and assisted the gamma-alpha phase transition indirectly. The gamma-phase slips into incomplete fragments at yield point, and the parts along tensile direction are responsible for the formation of transient phase. The gamma-fragments after yield is oriented...

  14. Analyses of kinetic glass transition in short-range attractive colloids based on time-convolutionless mode-coupling theory.

    Science.gov (United States)

    Narumi, Takayuki; Tokuyama, Michio

    2017-03-01

    For short-range attractive colloids, the phase diagram of the kinetic glass transition is studied by time-convolutionless mode-coupling theory (TMCT). Using numerical calculations, TMCT is shown to recover all the remarkable features predicted by the mode-coupling theory for attractive colloids: the glass-liquid-glass reentrant, the glass-glass transition, and the higher-order singularities. It is also demonstrated through the comparisons with the results of molecular dynamics for the binary attractive colloids that TMCT improves the critical values of the volume fraction. In addition, a schematic model of three control parameters is investigated analytically. It is thus confirmed that TMCT can describe the glass-glass transition and higher-order singularities even in such a schematic model.

  15. Spin glass transition in canonical AuFe alloys: A numerical study

    International Nuclear Information System (INIS)

    Zhang, Kai-Cheng; Li, Yong-Feng; Liu, Gui-Bin; Zhu, Yan

    2012-01-01

    Although spin glass transitions have long been observed in diluted magnetic alloys, e.g. AuFe and CuMn alloys, previous numerical studies are not completely consistent with the experiment results. The abnormal critical exponents of the alloys remain still puzzling. By employing parallel tempering algorithm with finite-size scaling analysis, we investigated the phase transitions in canonical AuFe alloys. Our results strongly support that spin glass transitions occur at finite temperatures in the alloys. The calculated critical exponents agree well with those obtained from experiments. -- Highlights: ► By simulation we investigated the abnormal critical exponents observed in canonical SG alloys. ► The critical exponents obtained from our simulations agree well with those measured from experiments. ► Our results strongly support that RKKY interactions lead to SG transitions at finite temperatures.

  16. Glass transition memorized by the enthalpy-entropy compensation in the shear thinning of supercooled metallic liquids

    Science.gov (United States)

    Zhang, Meng; Liu, Lin

    2018-06-01

    To unravel the true nature of glass transition, broader insights into glass forming have been gained by examining the stress-driven glassy systems, where strong shear thinning, i.e. a reduced viscosity under increasing shear rate, is encountered. It is argued that arbitrarily small stress-driven shear rates would ‘melt’ the glass and erase any memory of its thermal history. In this work, we report a glass transition memorized by the enthalpy-entropy compensation in strongly shear-thinned supercooled metallic liquids, which coincides with the thermal glass transition in both the transition temperature and the activation Gibbs free energy. Our findings provide distinctive insights into both glass forming and shear thinning, and enrich current knowledge on the ubiquitous enthalpy-entropy compensation empirical law in condensed matter physics.

  17. Analyses of glass transition phenomena by solving differential equation with delay effect

    International Nuclear Information System (INIS)

    Takeuchi, A.; Inoue, A.

    2007-01-01

    A linear differential equation for the analyses of glass transition phenomena has been proposed by taking into account the delay effect due to the change in transportation of atoms near the glass transition temperature (T g ). Under the condition maintaining the order of the differential equation as the second, the non-linear differential equation proposed by Van Den Beukel and Sietsma is modified to obtain the analytic solution for a linear equation by introducing the following points: the delay effect which is described with a term of Mackey-Glass model, a concept of effective free volume (x fe eff ) and its concentration expression (C fe eff ) which correspond to the equilibrium, and an additional term associated with C fe eff . In analyzing the linear equation, Doyle's p-function was used for the integral of reaction rate with respect to temperature (T). It is found that the linear equation proposed in the present study can describe the changes in free volume (x) with increasing temperature in the dx/dT-T chart, the sharp increase in free volume at T g , and over shooting phenomena of free volume slightly above the T g , as experimentally in thermal analyses for metallic glasses. The linear solution obtained in the present study is of great importance for the analyses of the glass transition because the change in free volume with increasing temperature on heating is described with fundamental functions

  18. Influence of processing conditions on the glass-crystal transition into borosilicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Deschanels, X.; Cachia, J.N.; Lopez, C.; Peuget, S. [CEA Marcoule, BP 17171, 30207 Bagnols sur Ceze (France)

    2008-07-01

    The precipitation of a crystalline phase in glass is observed when one element exceeds its loading limit (i.e.: solubility limit). In this work we have studied the solubility of different actinides and surrogates (lanthanides and hafnium) in borosilicate glass used for the immobilization of the high-level nuclear waste (HLW glasses). The results obtained show an increase of the solubility limits of these elements with the processing temperature and the redox potential of the melt. The elements at the oxidation state (III) exhibit a higher solubility than the element at oxidation state (IV). In this framework, cerium is an interesting element because its oxidation state tunes from (IV) to (III) as a function of the processing conditions. It is shown that the solubility of cerium can be multiplied by a factor of 20 at 1100 C. degrees. In order to have a better understanding of the mechanisms that underline the evolution of the solubility, XAFS and NMR investigation has been undertaken. Trivalent elements present the characteristics of network-modified cations while tetravalent elements look like network-former cations.

  19. Relaxation dynamics of glass transition in PMMA + SWCNT composites by temperature-modulated DSC

    Science.gov (United States)

    Pradhan, N. R.; Iannacchione, G. S.

    2010-03-01

    The experimental technique offered by temperature-modulated differential scanning calorimeter (TMDSC) used to investigate the thermal relaxation dynamics through the glass transition as a function of frequency was studied for pure PMMA and PMMA-single wall carbon nanotubes (SWCNTs) composites. A strong dependence of the temperature dependence peak in the imaginary part of complex heat capacity (Tmax) is found during the transition from the glass-like to the liquid-like region. The frequency dependence of Tmax of the imaginary part of heat capacity (Cp) is described by Arrhenius law. The activation energy obtained from the fitting shows increases while the characteristic relaxation time decreases with increasing mass fraction (phim) of SWCNTs. The dynamics of the composites during glass transition, at slow and high scan rates, are also the main focus of this experimental study. The change in enthalpy during heating and cooling is also reported as a function of scan rate and frequency of temperature modulation. The glass transition temperature (Tg) shows increases with increasing frequency of temperature modulation and phim of SWCNTs inside the polymer host. Experimental results show that Tg is higher at higher scan rates but as the frequency of temperature modulation increases, the Tg values of different scan rates coincide with each other and alter the scan rate dependence. From the imaginary part of heat capacity, it is obvious that Tmax is not the actual glass transition temperature of pure polymer but Tmax and Tg values can be superimposed when phim increases in the polymer host or when the sample undergoes a transition with a certain frequency of temperature modulation.

  20. Polymer relaxations in thin films in the vicinity of a penetrant or a temperature induced glass transition

    NARCIS (Netherlands)

    Ogieglo, Wojciech; Wessling, Matthias; Benes, Nieck Edwin

    2014-01-01

    The transient properties of thin glassy polymer films in the vicinity of the glass transition are investigated. We compare the differences and similarities between sorption and temperature induced glass transitions, referred to as Pg and Tg, respectively. The experimental technique used is in situ

  1. NMR signature of evolution of ductile-to-brittle transition in bulk metallic glasses.

    Science.gov (United States)

    Yuan, C C; Xiang, J F; Xi, X K; Wang, W H

    2011-12-02

    The mechanical properties of monolithic metallic glasses depend on the structures at atomic or subnanometer scales, while a clear correlation between mechanical behavior and structures has not been well established in such amorphous materials. In this work, we find a clear correlation of (27)Al NMR isotropic shifts with a microalloying induced ductile-to-brittle transition at ambient temperature in bulk metallic glasses, which indicates that the (27)Al NMR isotropic shift can be regarded as a structural signature to characterize plasticity for this metallic glass system. The study provides a compelling approach for investigating and understanding the mechanical properties of metallic glasses from the point of view of electronic structure. © 2011 American Physical Society

  2. The glass transition, crystallization and melting in Au-Pb-Sb alloys

    Science.gov (United States)

    Lee, M. C.; Allen, J. L.; Fecht, H. J.; Perepezko, J. H.; Ohsaka, K.

    1988-01-01

    The glass transition, crystallization and melting of Au(55)Pb(22.5)Sb(22.5) alloys have been studied by differential scanning calorimetry DSC. Crystallization on heating above the glass transition temperature Tg (45 C) begins at 64 C. Further crystallization events are observed at 172 C and 205 C. These events were found to correspond to the formation of the intermetallic compounds AuSb2, Au2Pb, and possibly AuPb2, respectively. Isothermal DSC scans of the glassy alloy above Tg were used to monitor the kinetics of crystallization. The solidification behavior and heat capacity in the glass-forming composition range were determined with droplet samples. An undercooling level of 0.3T(L) below the liquidus temperature T(L) was achieved, resulting in crystallization of different stable and metastable phases. The heat capacity C(P) of the undercooled liquid was measured over an undercooling range of 145 C.

  3. Local variation of fragility and glass transition temperature of ultra-thin supported polymer films.

    Science.gov (United States)

    Hanakata, Paul Z; Douglas, Jack F; Starr, Francis W

    2012-12-28

    Despite extensive efforts, a definitive picture of the glass transition of ultra-thin polymer films has yet to emerge. The effect of film thickness h on the glass transition temperature T(g) has been widely examined, but this characterization does not account for the fragility of glass-formation, which quantifies how rapidly relaxation times vary with temperature T. Accordingly, we simulate supported polymer films of a bead-spring model and determine both T(g) and fragility, both as a function of h and film depth. We contrast changes in the relaxation dynamics with density ρ and demonstrate the limitations of the commonly invoked free-volume layer model. As opposed to bulk polymer materials, we find that the fragility and T(g) do not generally vary proportionately. Consequently, the determination of the fragility profile--both locally and for the film as a whole--is essential for the characterization of changes in film dynamics with confinement.

  4. Thermalization calorimetry: A simple method for investigating glass transition and crystallization of supercooled liquids

    Directory of Open Access Journals (Sweden)

    Bo Jakobsen

    2016-05-01

    Full Text Available We present a simple method for fast and cheap thermal analysis on supercooled glass-forming liquids. This “Thermalization Calorimetry” technique is based on monitoring the temperature and its rate of change during heating or cooling of a sample for which the thermal power input comes from heat conduction through an insulating material, i.e., is proportional to the temperature difference between sample and surroundings. The monitored signal reflects the sample’s specific heat and is sensitive to exo- and endothermic processes. The technique is useful for studying supercooled liquids and their crystallization, e.g., for locating the glass transition and melting point(s, as well as for investigating the stability against crystallization and estimating the relative change in specific heat between the solid and liquid phases at the glass transition.

  5. Exploring the dynamics about the glass transition by muon spin relaxation and muon spin rotation

    International Nuclear Information System (INIS)

    Bermejo, F J; Bustinduy, I; Cox, S F J; Lord, J S; Cabrillo, C; Gonzalez, M A

    2006-01-01

    The capability of muon spin rotation and muon spin relaxation to explore dynamics in the vicinity of the glass transition is illustrated by results pertaining to three materials exhibiting two different glass-forming abilities. Measurements under transverse magnetic fields enable us to monitor the dynamics of muonium-labelled closed-shell molecules within the microsecond range. The results display the onset of stochastic molecular motions taking place upon crossing from below the glass-transition temperature. In turn, the molecular dynamics of radicals formed by addition of atomic muonium to unsaturated organic molecules can also be explored up to far shorter times by means of relaxation measurements under longitudinal fields. The technique is then shown to be capable of singling out stochastic reorientational motions from others, which usually are strongly coupled to them and usually dominate the material response when measured using higher-frequency probes such as neutron and light scattering

  6. Energy Transfer between Post-Transition Elements & Rare Earths in Oxide & Chalcogenide Glasses.

    Science.gov (United States)

    1979-08-27

    Caird [13]. A calculation of reduced matrix elements of Pr3 in 20 Na O • 80 TeO2 glass [14] showed that they differ slightly from data of ref. [121... glasses Transition (lass 35 ZnO 65 TeO2 20 Na2 O 80 TeO 2 fX 106 fX 106 l.,eas 3a, a) Ia’l. faI f.me.s f al f+ I fal 3 H4 - 3 H6 1.56 1.65 1.12...Rare-Earth Doped Glasses 20. jIST HAEV CCnFn~m ,i cn,on ra e sideit If c."*Ar’ -- ~ 14-r by t?-h.c .: r Intensity parameters, radiative transition

  7. Neutron Scattering Analysis of Water's Glass Transition and Micropore Collapse in Amorphous Solid Water.

    Science.gov (United States)

    Hill, Catherine R; Mitterdorfer, Christian; Youngs, Tristan G A; Bowron, Daniel T; Fraser, Helen J; Loerting, Thomas

    2016-05-27

    The question of the nature of water's glass transition has continued to be disputed over many years. Here we use slow heating scans (0.4  K min^{-1}) of compact amorphous solid water deposited at 77 K and an analysis of the accompanying changes in the small-angle neutron scattering signal, to study mesoscale changes in the ice network topology. From the data we infer the onset of rotational diffusion at 115 K, a sudden switchover from nondiffusive motion and enthalpy relaxation of the network at 121  K, in excellent agreement with the glass transition onset deduced from heat capacity and dielectric measurements. This indicates that water's glass transition is linked with long-range transport of water molecules on the time scale of minutes and, thus, clarifies its nature. Furthermore, the slow heating rates combined with the high crystallization resistance of the amorphous sample allow us to identify the glass transition end point at 136 K, which is well separated from the crystallization onset at 144 K-in contrast to all earlier experiments in the field.

  8. Determination of the glass-transition temperature of proteins from a viscometric approach.

    Science.gov (United States)

    Monkos, Karol

    2015-03-01

    All fully hydrated proteins undergo a distinct change in their dynamical properties at glass-transition temperature Tg. To determine indirectly this temperature for dry albumins, the viscosity measurements of aqueous solutions of human, equine, ovine, porcine and rabbit serum albumin have been conducted at a wide range of concentrations and at temperatures ranging from 278 K to 318 K. Viscosity-temperature dependence of the solutions is discussed on the basis of the three parameters equation resulting from Avramov's model. One of the parameter in the Avramov's equation is the glass-transition temperature. For all studied albumins, Tg of a solution monotonically increases with increasing concentration. The glass-transition temperature of a solution depends both on Tg for a dissolved dry protein Tg,p and water Tg,w. To obtain Tg,p for each studied albumin the modified Gordon-Taylor equation was applied. This equation describes the dependence of Tg of a solution on concentration, and Tg,p and a parameter depending on the strength of the protein-solvent interaction are the fitting parameters. Thus determined the glass-transition temperature for the studied dry albumins is in the range (215.4-245.5)K. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. CORRELATION OF THE GLASS TRANSITION TEMPERATURE OF PLASTICIZED PVC USING A LATTICE FLUID MODEL

    Science.gov (United States)

    A model has been developed to describe the composition dependence of the glass transition temperature (Tg) of polyvinyl chloride (PVC) + plasticizer mixtures. The model is based on Sanchez-Lacombe equation of state and the Gibbs-Di Marzio criterion, which states that th...

  10. Interactions in a blend of two polymers greatly differing in glass transition temperature

    Czech Academy of Sciences Publication Activity Database

    Kratochvíl, Jaroslav; Šturcová, Adriana; Sikora, Antonín; Dybal, Jiří

    2011-01-01

    Roč. 49, č. 14 (2011), s. 1031-1040 ISSN 0887-6266 Institutional research plan: CEZ:AV0Z40500505 Keywords : differential scanning calorimetry (DSC) * fouriertransform infrared spectroscopy (FT-IR) * glass transition temperature Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.531, year: 2011

  11. Studying the Adhesion Force and Glass Transition of Thin Polystyrene Films by Atomic Force Microscopy

    DEFF Research Database (Denmark)

    Kang, Hua; Qian, Xiaoqin; Guan, Li

    2018-01-01

    microscopy (AFM)-based forcedistance curve to study the relaxation dynamics and the film thickness dependence of glass transition temperature (T-g) for normal thin polystyrene (PS) films supported on silicon substrate. The adhesion force (F-ad) between AFM tip and normal thin PS film surfaces...

  12. Molecular Motion in Polymers: Mechanical Behavior of Polymers Near the Glass-Rubber Transition Temperature.

    Science.gov (United States)

    Sperling, L. H.

    1982-01-01

    The temperature at which the onset of coordinated segmental motion begins is called the glass-rubber transition temperature (Tg). Natural rubber at room temperature is a good example of a material above its Tg. Describes an experiment examining the response of a typical polymer to temperature variations above and below Tg. (Author/JN)

  13. Mathematical modeling of photoinitiated coating degradation: Effects of coating glass transition temperature and light stabilizers

    DEFF Research Database (Denmark)

    Kiil, Søren; G.de With, R.A.T.M.Van Benthem

    2013-01-01

    A mathematical model, describing coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature, was extended to simulate the behavior of a coating with a low glass transition temperature. The effects of adding light stabilizers (a UV...

  14. Glass transition and relaxation processes of polymers studied by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science

    1996-10-01

    The glass transition and relaxation processes of polymers were studied by the positron annihilation technique. A positron implanted into polymers might annihilate from positronium (Ps) states in open spaces. Ps is a bound state between a positron and an electron, and its nonrelativistic quantum mechanics is practically identical to that of a hydrogen atom. The lifetime of Ps can be associated with the size of the open spaces, and the formation probability of Ps provides information of motions of molecules. Since the glass transition or relaxation processes affect behavior of open spaces, one can study these phenomena through the detection of the open spaces using the positron annihilation technique. In the present paper, we report studies of the glass transition and relaxation processes in polyethylene, polypropylene, and polystyrene by measurements of lifetime spectra of positrons and those of Doppler broadening profiles of the annihilation radiation. For these specimens, by measurements of the lifetime of Ps, {tau}{sub 3}, as a function of temperature, the glass transition temperature, T{sub g}, was determined as an onset temperature of the increase in the temperature coefficient of {tau}{sub 3}. Below T{sub g}, local motions of molecules were detected by measurements of the formation probability of Ps. The positron annihilation as a tool for the characterization of polymers was discussed. (author). 51 refs.

  15. Relaxation Dynamics of the Glass Transition in PMMA+SWCNT Composites by Temperature-Modulated DSC

    Science.gov (United States)

    Pradhan, Nihar; Iannacchione, Germano

    2010-03-01

    Temperature Modulated Differential Scanning Calorimeter (TMDSC) used to investigate the thermal relaxation dynamics of PMMA-Single wall carbon nanotubes (SWCNTs) through the glass transition as a function of frequency. A strong dependence of the temperature dependence peak in imaginary part of complex heat capacity (Tmax) was found during the transition from glass like to liquid like region and can be described by Arhenius law. The activation energy shows increases while the charactersistic time decreases with increasing mass fraction (φm) of SWCNTs. Decreasing of enthalpy, while heating and slowly increasing while cooling at 2.0 K/min scan rate was observed and as frequency of temperature modulation increases. There is no relative change of enthalpy in heating and cooling observed at sufficiently slow scan rate. The glass transition temperature (Tg) shows increases as a function of frequency of temperature modulation, φm of SWCNTs and with increasing scan rate. From imaginary part of heat capacity, it obvious that Tmax is not the actual glass transition temperature of pure polymer but Tmax and Tg values can be superimpose when φm of SWCNT increases in polymer.

  16. Practical Considerations for Determination of Glass Transition Temperature of a Maximally Freeze Concentrated Solution.

    Science.gov (United States)

    Pansare, Swapnil K; Patel, Sajal Manubhai

    2016-08-01

    Glass transition temperature is a unique thermal characteristic of amorphous systems and is associated with changes in physical properties such as heat capacity, viscosity, electrical resistance, and molecular mobility. Glass transition temperature for amorphous solids is referred as (T g), whereas for maximally freeze concentrated solution, the notation is (T g'). This article is focused on the factors affecting determination of T g' for application to lyophilization process design and frozen storage stability. Also, this review provides a perspective on use of various types of solutes in protein formulation and their effect on T g'. Although various analytical techniques are used for determination of T g' based on the changes in physical properties associated with glass transition, the differential scanning calorimetry (DSC) is the most commonly used technique. In this article, an overview of DSC technique is provided along with brief discussion on the alternate analytical techniques for T g' determination. Additionally, challenges associated with T g' determination, using DSC for protein formulations, are discussed. The purpose of this review is to provide a practical industry perspective on determination of T g' for protein formulations as it relates to design and development of lyophilization process and/or for frozen storage; however, a comprehensive review of glass transition temperature (T g, T g'), in general, is outside the scope of this work.

  17. Material properties and glass transition temperatures of different thermoplastic starches after extrusion processing

    NARCIS (Netherlands)

    Janssen, Léon P.B.M.; Karman, Andre P.; Graaf, Robbert A. de

    Four different starch sources, namely waxy maize, wheat, potato and pea starch were extruded with the plasticizer glycerol, the latter in concentrations of 15, 20 and 25% (w/w). The glass transition temperatures of the resulting thermoplastic products were measured by Dynamic Mechanical Thermal

  18. Crystallization kinetics, glass transition kinetics, and thermal stability of Se70-xGa30Inx (x=5, 10, 15, and 20) semiconducting glasses

    International Nuclear Information System (INIS)

    Imran, Mousa M.A.

    2011-01-01

    Crystallization and glass transition kinetics of Se 70-x Ga 30 In x (x=5, 10, 15, and 20) semiconducting chalcogenide glasses were studied under non-isothermal condition using a Differential Scanning Calorimeter (DSC). DSC thermograms of the samples were recorded at four different heating rates 5, 10, 15, and 20 K/min. The variation of the glass transition temperature (T g ) with the heating rate (β) was used to calculate the glass transition activation energy (E t ) using two different models. Meanwhile, the variation of the peak temperature of crystallization (T p ) with β was utilized to deduce the crystallization activation energy (E c ) using Kissinger, Augis-Bennet, and Takhor models. Results reveal that E t decreases with increasing In content, while both T g and E c exhibit the opposite behavior, and the crystal growth occurs in one dimension. The variation of these thermal parameters with the average coordination number was also discussed, and the results were interpreted in terms of the type of bonding that In makes with Se. Assessment of thermal stability and glass forming ability (GFA) was carried out on the basis of some quantitative criteria and the results indicate that thermal stability is enhanced while the crystallization rate is reduced with the addition of In to Se-Ga glass. -- Research highlights: → Addition of In to Se-Ga glass decreases the glass transition activation energy. → The crystallization rate in Se-Ga-In glass is reduced as In content increases. → The crystal growth in Se-Ga-In glass occurs in one dimension. → Thermal properties of Se-Ga-In glass indicate a shift in Phillips-Thorpe threshold.

  19. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability.

    Science.gov (United States)

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A S

    2015-11-10

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12h at temperatures 20°C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20°C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π-π interactions reduce the inherent physical stability of amorphous drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Transport properties of glass-forming liquids suggest that dynamic crossover temperature is as important as the glass transition temperature.

    Science.gov (United States)

    Mallamace, Francesco; Branca, Caterina; Corsaro, Carmelo; Leone, Nancy; Spooren, Jeroen; Chen, Sow-Hsin; Stanley, H Eugene

    2010-12-28

    It is becoming common practice to partition glass-forming liquids into two classes based on the dependence of the shear viscosity η on temperature T. In an Arrhenius plot, ln η vs 1/T, a strong liquid shows linear behavior whereas a fragile liquid exhibits an upward curvature [super-Arrhenius (SA) behavior], a situation customarily described by using the Vogel-Fulcher-Tammann law. Here we analyze existing data of the transport coefficients of 84 glass-forming liquids. We show the data are consistent, on decreasing temperature, with the onset of a well-defined dynamical crossover η(×), where η(×) has the same value, η(×) ≈ 10(3) Poise, for all 84 liquids. The crossover temperature, T(×), located well above the calorimetric glass transition temperature T(g), marks significant variations in the system thermodynamics, evidenced by the change of the SA-like T dependence above T(×) to Arrhenius behavior below T(×). We also show that below T(×) the familiar Stokes-Einstein relation D/T ∼ η(-1) breaks down and is replaced by a fractional form D/T ∼ η(-ζ), with ζ ≈ 0.85.

  1. Effect of mixed transition metal ions on DC conductivity in lithium bismuth borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Khasa, S.; Yadav, Arti, E-mail: artidabhur@gmail.com; Dahiya, M. S.; Seema,; Ashima [Physics Department, Deenbandhu Chhotu Ram University of Science & Technology, Murthal-131039 (India); Agarwal, A. [Physics Department, G.J. University of science and technology, Hisar-125001 (India)

    2015-06-24

    The DC conductivities of glasses having composition x(2NiO·V{sub 2}O{sub 5})·(30-x)Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} (with x=0, 2, 5, 7 and 10, i.e. NVLBB glasses) and glass samples having composition 7NiO·23 Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} and 7V{sub 2}O{sub 5}·23Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} (NLBB and VLBB respectively) are investigated as a function of temperature. Conductivity for glasses containing higher percentage of lithium ions is predominantly ionic and in glasses containing higher percentage of transition metal (TM) ions is predominantly electronic. The observed increase in conductivity with x and peak-like behavior at x=7 in NVLBB glasses due to competitive transport of small polaron contributing to a significant structural change in NVLBB glasses. Variation of molar volume and density was also observed with x. In NVLBB glasses, as x increases density increases except a slight decrease at x=7. Also density increases in NLBB whereas in case of VLBB it decreases in comparison to NVLBB1 glass composition. Mott’s small polaron hopping (SPH) model has been applied to analyze the high temperature conductivity data and activation energy.

  2. Spectroscopic and ultrasonic investigations on structural characterization of borate glass specimen doped with transition metal ions.

    Science.gov (United States)

    Sathish, K; Thirumaran, S

    2015-08-05

    The present work describes the glass samples of composition (x% V₂O₅-(80-x)% B₂O₃-20% Na₂CO₃) VBS glass system and (x%MnO₂-(80-x)% B₂O₃-20% Na₂CO₃) in MBS glass system with mol% ranging from x=3, 6, 9, 12, 15 and 18 in steps of 3 mol% are prepared by melt quenching technique. For these prepared glass systems, sound velocity (longitudinal and shear velocities) and density have been measured. The sound velocity (longitudinal and shear) was measured by using pulse-echo technique at 5 MHz. The XRD study was carried to out to ascertain the amorphous nature of the glass specimen. Using these measured values, the elastic moduli, Poisson's ratio, Debye temperature, acoustic impedance and thermal expansion coefficient of the two glass systems were evaluated. The elastic and mechanical properties of the prepared glass systems are analyzed from ultrasonic study and the structural characterization from spectroscopic study. The effects due to the doping of transition metal ions with borate have been discussed. In the V₂O₅ doped glass system,(VBS glass system) the sound velocity, density and elastic moduli, steeply increases after 12 mol% comparatively with MnO₂ doped glass system (VBS glass system). The present study critically observes the doping of V₂O₅ with borate enhances the strengthening of network linkage and hardening of the glassy network structure than MnO₂. The IR spectral analysis reveals depolymerization of the borate network and conversion of BO₃ or BO4 units with the formation of non-bridging oxygen. The FTIR spectral studies confirm the presence of various functional groups of the sample. FTIR spectrum of sample exhibits broad absorption bands indicating the wide distribution of borate structural units. The effect of Na₂CO₃, V₂O₅ and MnO₂ contents on the structures of borate glass is evaluated from the FTIR spectra. The topological aspects of the prepared glass samples are exhaustively reported from SEM micrographs

  3. Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing.

    Science.gov (United States)

    Kim, Chae Un; Tate, Mark W; Gruner, Sol M

    2015-09-22

    Observation of theorized glass-to-liquid transitions between low-density amorphous (LDA) and high-density amorphous (HDA) water states had been stymied by rapid crystallization below the homogeneous water nucleation temperature (∼235 K at 0.1 MPa). We report optical and X-ray observations suggestive of glass-to-liquid transitions in these states. Crack healing, indicative of liquid, occurs when LDA ice transforms to cubic ice at 160 K, and when HDA ice transforms to the LDA state at temperatures as low as 120 K. X-ray diffraction study of the HDA to LDA transition clearly shows the characteristics of a first-order transition. Study of the glass-to-liquid transitions in nanoconfined aqueous solutions shows them to be independent of the solute concentrations, suggesting that they represent an intrinsic property of water. These findings support theories that LDA and HDA ice are thermodynamically distinct and that they are continuously connected to two different liquid states of water.

  4. Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing

    Science.gov (United States)

    Kim, Chae Un; Tate, Mark W.; Gruner, Sol M.

    2015-01-01

    Observation of theorized glass-to-liquid transitions between low-density amorphous (LDA) and high-density amorphous (HDA) water states had been stymied by rapid crystallization below the homogeneous water nucleation temperature (∼235 K at 0.1 MPa). We report optical and X-ray observations suggestive of glass-to-liquid transitions in these states. Crack healing, indicative of liquid, occurs when LDA ice transforms to cubic ice at 160 K, and when HDA ice transforms to the LDA state at temperatures as low as 120 K. X-ray diffraction study of the HDA to LDA transition clearly shows the characteristics of a first-order transition. Study of the glass-to-liquid transitions in nanoconfined aqueous solutions shows them to be independent of the solute concentrations, suggesting that they represent an intrinsic property of water. These findings support theories that LDA and HDA ice are thermodynamically distinct and that they are continuously connected to two different liquid states of water. PMID:26351671

  5. First-order phase transition in the quantum spin glass at T=0

    Energy Technology Data Exchange (ETDEWEB)

    Viana, J. Roberto; Nogueira, Yamilles; Sousa, J. Ricardo de

    2003-05-26

    The van Hemmen model with transverse and random longitudinal field is studied to analyze the tricritical behavior in the quantum Ising spin glass at T=0. The free energy and order parameter are calculated for two types of probability distributions: Gaussian and bimodal. We obtain the phase diagram in the {omega}-H plane, where {omega} and H are the transverse and random longitudinal fields, respectively. For the case of Gaussian distribution the phase transition is of second order, while the bimodal distribution we observe second-order transition for high-transverse field and first-order transition for small transverse field, with a tricritical point in the phase diagram.

  6. First-order phase transition in the quantum spin glass at T=0

    International Nuclear Information System (INIS)

    Viana, J. Roberto; Nogueira, Yamilles; Sousa, J. Ricardo de

    2003-01-01

    The van Hemmen model with transverse and random longitudinal field is studied to analyze the tricritical behavior in the quantum Ising spin glass at T=0. The free energy and order parameter are calculated for two types of probability distributions: Gaussian and bimodal. We obtain the phase diagram in the Ω-H plane, where Ω and H are the transverse and random longitudinal fields, respectively. For the case of Gaussian distribution the phase transition is of second order, while the bimodal distribution we observe second-order transition for high-transverse field and first-order transition for small transverse field, with a tricritical point in the phase diagram

  7. Thermal history of Hawaiian pāhoehoe lava crusts at the glass transition: implications for flow rheology and emplacement

    Science.gov (United States)

    Gottsmann, Joachim; Harris, Andrew J. L.; Dingwell, Donald B.

    2004-12-01

    We have investigated the thermal history of glassy pāhoehoe crusts across their glass transition. Ten different samples obtained between 1993 and 2003 from the active flow field of the Pu'u 'O'o-Kupaianaha eruption on Hawaii (USA) have been analysed using relaxation geospeedometry. This method employs differential scanning calorimetry to quantify the enthalpic relaxation of the glass to monitor the natural time-temperature (t-T) path followed by the melt during cooling across its glass transition. Cooling rates across the glass transition interval (at 1000- 900 K) have been found to vary between 8 and 140 K/min. The associated glass transition temperatures are up to 400 K, lower than previously anticipated by others. Melt viscosities at the glass transition for these crusts range from 10 9.4 to 10 10.7 Pa s. We have compared the t-T paths quantified via relaxation geospeedometry with those obtained from direct measurements on the active flow field. The calorimetrically determined cooling rates are consistent with either simple cooling from eruption temperatures to temperatures below the glass transition or more complex cooling paths, including periods of reheating and short-term annealing within the glass transition interval. By quantifying the relaxation times associated with these contrasting cooling histories, we show that secondary vesiculation of pāhoehoe flow crusts may be favoured by complex, nonlinear t-T paths within the glass transition. These constraints also allow us to evaluate the time scales associated with the crystallisation and inflation of flow lobes at the glass transition for different pāhoehoe lava flow types. Our results provide important quantifications of rheological parameters at the lower temperature range of viscoelastic deformation in basaltic lava flows. As such, the results may be helpful in refining models for the generation of continental flood basalt flows, as well as models of basaltic lava flow propagation for hazard

  8. X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

    International Nuclear Information System (INIS)

    Harris, William H.; Guillen, Donna P.; Klouzek, Jaroslav; Pokorny, Richard; Yano, Tetsuji

    2017-01-01

    The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2 /(Li 2 CO 3 +H 3 BO 3 +Na 2 CO 3 ) mass fractions at temperatures between 600°C and 1040°C. To track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2 /(Li 2 CO 3 +H 3 BO 3 +Na 2 CO 3 ) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower total amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.

  9. Analytical evidence for the absence of spin glass transition on self-dual lattices

    International Nuclear Information System (INIS)

    Ohzeki, Masayuki; Nishimori, Hidetoshi

    2009-01-01

    We show strong evidence for the absence of a finite-temperature spin glass transition for the random-bond Ising model on self-dual lattices. The analysis is performed by an application of duality relations, which enables us to derive a precise but approximate location of the multicritical point on the Nishimori line. This method can be systematically improved to presumably give the exact result asymptotically. The duality analysis, in conjunction with the relationship between the multicritical point and the spin glass transition point for the symmetric distribution function of randomness, leads to the conclusion of the absence of a finite-temperature spin glass transition for the case of symmetric distribution. The result is applicable to the random-bond Ising model with ±J or Gaussian distribution and the Potts gauge glass on the square, triangular and hexagonal lattices as well as the random three-body Ising model on the triangular and the Union-Jack lattices and the four-dimensional random plaquette gauge model. This conclusion is exact provided that the replica method is valid and the asymptotic limit of the duality analysis yields the exact location of the multicritical point. (fast track communication)

  10. Thermodynamics and kinetics of the glass transition: A generic geometric approach

    International Nuclear Information System (INIS)

    Gutzow, I.; Ilieva, D.; Babalievski, F.; Yamakov, V.

    2000-01-01

    A generic phenomenological theory of the glass transition is developed in the framework of a quasilinear formulation of the thermodynamics of irreversible processes. Starting from one of the basic principles of this science in its approximate form given by de Donder's equation, after a change of variables the temperature dependence of the structural parameter ξ(T), the thermodynamic potentials ΔG(tilde sign)(T), the thermodynamic functions and the time of molecular relaxation τ of vitrifying systems is constructed. In doing so, a new effect in the ΔG(tilde sign)(T) course is observed. The analysis of the higher derivatives of the thermodynamic potential, and especially the nullification of the second derivative of the configurational specific heats ΔC(tilde sign) p (T) of the vitrifying liquid defines glass transition temperature T(tilde sign) g and leads directly to the basic dependence of glass transition kinetics: the Frenkel-Kobeko-Reiner equation. The conditions guaranteeing the fulfillment of this equation specify the temperature dependence of the activation energy U(T,ξ(tilde sign)) for viscous flow and give a natural differentiation of glass formers into fragile and strong liquids. The effect of thermal prehistory on the temperature dependence of both thermodynamic functions and kinetic coefficients is established by an appropriate separation of de Donder's equation. (c) 2000 American Institute of Physics

  11. Doping influence by some transition elements on the irradiation effects in nuclear waste glasses

    International Nuclear Information System (INIS)

    Florent, Olivier

    2006-06-01

    High-level waste glasses are submitted to auto-irradiation. Modelling it using external irradiations on simple glasses revealed defects production and non negligible structural changes. This thesis aims at determining the impact of a more complex composition on these effects, especially the influence of adding polyvalent transition metals. Silicate, soda-lime and alumino-borosilicate glasses are doped with different iron, chromium and manganese concentrations then β irradiated at different doses up to 10 9 Gy. Non doped glasses show an increase of their density and polymerisation coupled with a molecular oxygen and point defects production. Adding 0.16 mol% Fe decreases the amount of defects by 85 % and all irradiation effects. A Fe 3+ reduction is also observed by EPR, optical absorption and indirectly by Raman spectroscopy. A higher than 0.32 mol% Fe concentration causes complete blockage of the evolution of polymerisation, density and defect production. The same results are obtained on chromium or manganese doped glasses. An original in situ optical absorption device shows the quick decrease of Fe 3+ amount to a 25 % lower level during irradiation. Stopping irradiation causes a lower decrease of 65 %, suggesting a dynamic (h 0 /e-) consuming equilibrium. He + and Kr 3+ ions and γ irradiated glasses tend to confirm these phenomena for all kind of irradiation with electronic excitations. (author)

  12. Peculiar thermal points during B2O3 transition from liquid to glass-like state

    International Nuclear Information System (INIS)

    Bartenev, G.M.; Lomovskoj, V.A.

    1992-01-01

    Relaxation transitions in glass-like B 2 O 3 were studied by dynamic methods in vacuum in the temperature range of 70-1070 K and frequency range of 10 -4 -1.2·10 6 Hz. The standard temperature of glass formation is T g =493 K and it corresponds to the standard frequency 5.3·10 -4 Hz. Above T g two special temperature points - T K and T F , position of which does not depend on the frequency, are observed

  13. Deuteron NMR (Nuclear Magnetic Resonance) in relation to the glass transition in polymers

    Science.gov (United States)

    Roessler, E.; Sillescu, H.; Spiess, H. W.; Wallwitz, R.

    1983-01-01

    H-2NMR is introduced as a tool for investigating slow molecular motion in the glass transition region of amorphous polymers. In particular, we compare H-2 spin alignment echo spectra of chain deuterated polystyrene with model calculations for restricted rotational Brownian motion. Molecular motion in the polyztyrene-toluene system has been investigated by analyzing H-2NMR of partially deuterated polystyrene and toluene, respectively. The diluent mobility in the mixed glass has been decomposed into solid and liquid components where the respective average correlation times differ by more than 5 decades.

  14. Effects of dynamic heterogeneity and density scaling of molecular dynamics on the relationship among thermodynamic coefficients at the glass transition

    International Nuclear Information System (INIS)

    Koperwas, K.; Grzybowski, A.; Grzybowska, K.; Wojnarowska, Z.; Paluch, M.

    2015-01-01

    In this paper, we define and experimentally verify thermodynamic characteristics of the liquid-glass transition, taking into account a kinetic origin of the process. Using the density scaling law and the four-point measure of the dynamic heterogeneity of molecular dynamics of glass forming liquids, we investigate contributions of enthalpy, temperature, and density fluctuations to spatially heterogeneous molecular dynamics at the liquid-glass transition, finding an equation for the pressure coefficient of the glass transition temperature, dTg/dp. This equation combined with our previous formula for dTg/dp, derived solely from the density scaling criterion, implies a relationship among thermodynamic coefficients at Tg. Since this relationship and both the equations for dTg/dp are very well validated using experimental data at Tg, they are promising alternatives to the classical Prigogine-Defay ratio and both the Ehrenfest equations in case of the liquid-glass transition

  15. Effects of dynamic heterogeneity and density scaling of molecular dynamics on the relationship among thermodynamic coefficients at the glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Koperwas, K., E-mail: kkoperwas@us.edu.pl; Grzybowski, A.; Grzybowska, K.; Wojnarowska, Z.; Paluch, M. [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1A, 41-500 Chorzow (Poland)

    2015-07-14

    In this paper, we define and experimentally verify thermodynamic characteristics of the liquid-glass transition, taking into account a kinetic origin of the process. Using the density scaling law and the four-point measure of the dynamic heterogeneity of molecular dynamics of glass forming liquids, we investigate contributions of enthalpy, temperature, and density fluctuations to spatially heterogeneous molecular dynamics at the liquid-glass transition, finding an equation for the pressure coefficient of the glass transition temperature, dTg/dp. This equation combined with our previous formula for dTg/dp, derived solely from the density scaling criterion, implies a relationship among thermodynamic coefficients at Tg. Since this relationship and both the equations for dTg/dp are very well validated using experimental data at Tg, they are promising alternatives to the classical Prigogine-Defay ratio and both the Ehrenfest equations in case of the liquid-glass transition.

  16. Metastability at the Yield-Stress Transition in Soft Glasses

    Science.gov (United States)

    Lulli, Matteo; Benzi, Roberto; Sbragaglia, Mauro

    2018-04-01

    We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable "fluidized" state, which relaxes back to a metastable "solid" state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity) developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

  17. Glass transition temperature of dried lens tissue pretreated with trehalose, maltose, or cyclic tetrasaccharide.

    Science.gov (United States)

    Kawata, Tetsuhiro; Matsuo, Toshihiko; Uchida, Tetsuya

    2014-01-01

    Glass transition temperature is a main indicator for amorphous polymers and biological macromolecules as materials, and would be a key for understanding the role of trehalose in protecting proteins and cells against desiccation. In this study, we measured the glass transition temperature by differential scanning calorimetry of dried lens tissues as a model of a whole biological tissue to know the effect of pretreatment by trehalose and other sugars. Isolated porcine lenses were incubated with saline, 100 or 1000 mM concentration of trehalose, maltose, or cyclic tetrasaccharide dissolved in saline at room temperature for 150 minutes. The solutions were removed and all samples were dried at room temperature in a desiccator until no weight change. The dried tissues were ground into powder and placed in a measuring pan for differential scanning calorimetry. The glass transition temperature of the dried lens tissues, as a mean and standard deviation, was 63.0 ± 6.4°C (n = 3) with saline pretreatment; 53.0 ± 0.8°C and 56.3 ± 2.7°C (n = 3), respectively, with 100 and 1000 mM trehalose pretreatment; 56.0 ± 1.6°C and 55.8 ± 1.1°C (n = 3), respectively, with 100 and 1000 mM maltose pretreatment; 60.0 ± 8.8°C and 59.2 ± 6.3°C (n = 3), respectively, with 100 and 1000 mM cyclic tetrasaccharide pretreatment. The glass transition temperature appeared lower, although not significantly, with trehalose and maltose pretreatments than with saline and cyclic tetrasaccharide pretreatments (P > 0.05, Kruskal-Wallis test). The glass transition temperature of the dried lens tissues with trehalose pretreatment appeared more noticeable on the thermogram, compared with other pretreatments. The glass transition temperature was measured for the first time in the dried lens tissues as an example of a whole biological tissue and might provide a basis for tissue preservation in the dried condition.

  18. A FeNiMnC alloy with strain glass transition

    Directory of Open Access Journals (Sweden)

    Hui Ma

    2018-02-01

    Full Text Available Recent experimental and theoretical investigations suggested that doping sufficient point defects into a normal ferroelastic/martensitic alloy systems could lead to a frozen disordered state of local lattice strains (nanomartensite domains, thereby suppressing the long-range strain-ordering martensitic transition. In this study, we attempt to explore the possibility of developing novel ferrous Elinvar alloys by replacing nickel with carbon and manganese as dopant species. A nominal Fe89Ni5Mn4.6C1.4 alloy was prepared by argon arc melting, and XRD, DSC, DMA and TEM techniques were employed to characterize the strain glass transition signatures, such as invariance in average structure, frequency dispersion in dynamic mechanical properties (storage modulus and internal friction and the formation of nanosized strain domains. It is indicated that doping of Ni, Mn and C suppresses γ→α long-range strain-ordering martensitic transformation in Fe89Ni5Mn4.6C1.4 alloy, generating randomly distributed nanosized domains by strain glass transition. Keywords: Strain glass transition, Elinvar alloys, Point defects, Nanosized domains

  19. Dimensional study of the caging order parameter at the glass transition.

    Science.gov (United States)

    Charbonneau, Patrick; Ikeda, Atsushi; Parisi, Giorgio; Zamponi, Francesco

    2012-08-28

    The glass problem is notoriously hard and controversial. Even at the mean-field level, little is agreed upon regarding why a fluid becomes sluggish while exhibiting but unremarkable structural changes. It is clear, however, that the process involves self-caging, which provides an order parameter for the transition. It is also broadly assumed that this cage should have a gaussian shape in the mean-field limit. Here we show that this ansatz does not hold. By performing simulations as a function of spatial dimension d, we find the cage to keep a nontrivial form. Quantitative mean-field descriptions of the glass transition, such as mode-coupling theory, density functional theory, and replica theory, all miss this crucial element. Although the mean-field random first-order transition scenario of the glass transition is qualitatively supported here and non-mean-field corrections are found to remain small on decreasing d, reconsideration of its implementation is needed for it to result in a coherent description of experimental observations.

  20. Cluster glass transition in Ca2-xLaxMnO4

    International Nuclear Information System (INIS)

    Manaka, H.; Mishima, K.; Okuda, T.

    2007-01-01

    We performed linear and nonlinear AC magnetic susceptibility measurements on Ca 2-x La x MnO 4 (x=0.03,0.07,0.10, and 0.14). In such manganites, coexistence or competition brings about various phenomena. We focus on a cluster glass state consisting of ferromagnetic clusters within an antiferromagnetic matrix because the coexistence of the ferromagnetic double exchange interaction and the antiferromagnetic superexchange interaction is closely associated with phase separation. As a result, temperature (T) dependence of a linear susceptibility (X 0 ' (T)) exhibits a sharp peak for x=0.03, and these peaks become broad with increasing x. The X 0 ' (T) curves for x=0.07 and 0.10 show a typical frequency dependence around the peaks, suggesting a cluster (spin) glass transition. Furthermore, a nonlinear susceptibility (X 2 ' (T)) for x=0.10 exhibits successive transitions: the ferromagnetic transition in each cluster occurs at ∼108K and the antiferromagnetic transition between the ferromagnetic clusters occurs at ∼89K. From the X 0 ' (T) and X 2 ' (T) curves for various values of x, we found the existence of the ferromagnetic clusters within the antiferromagnetic matrix, and the cluster glass state was realized for 0.07=< x=<0.14

  1. Structural influence of mixed transition metal ions on lithium bismuth borate glasses

    Science.gov (United States)

    Yadav, Arti; Dahiya, Manjeet S.; Hooda, A.; Chand, Prem; Khasa, S.

    2017-08-01

    Lithium bismuth borate glasses containing mixed transition metals having composition 7CoO·23Li2O·20Bi2O3·50B2O3 (CLBB), 7V2O5·23Li2O·20Bi2O3·50B2O3 (VLBB) and x(2CoO·V2O5)·(30 - x)Li2O·20Bi2O3·50B2O3 (x = 0.0 (LBB) and x = 2.0, 5.0, 7.0, 10.0 mol% (CVLBB1-4)) are synthesized via melt quench route. The synthesized compositions are investigated for their physical properties using density (D) and molar volume (Vm), thermal properties by analyzing DSC/TG thermo-graphs, structural properties using IR absorption spectra in the mid-IR range and optical properties using UV-Vis-NIR spectroscopy. The Electron Paramagnetic Resonance (EPR) spectra of vanadyl and cobalt ion have been analyzed to study compositional effects on spin-Hamiltonian parameters. The non linear variations in physical properties depict a strong structural influence of Co/V- oxides on the glassy matrix. The compositional variations in characteristic temperatures (glass transition temperature Tg, glass crystallization temperature Tp and glass melting temperature Tm) reveals that Tg for glass samples CLBB is relatively less than that of pure lithium bismuth borate (LBB) glass sample wherein Tg for sample VLBB is higher than that of LBB. The increase in Tg (as compared with LBB) with an enhanced substitution of mixed transition metal oxides (2CoO·V2O5) shows a progressive structure modification of bismuth borate matrix. These predictions are very well corroborated by corresponding compositional trends of Tp and Tm. FTIR studies reveal that Co2+& VO2+ ions lead to structural rearrangements through the conversion of three-coordinated boron into four coordinated boron and thereby reducing number of non-bridging oxygen atoms. Bismuth is found to exist in [BiO6] octahedral units only, whereas boroxol rings are not present in the glass network. The theoretical values of optical basicity (Λth) and corresponding oxide ion polarizability (αo2-) have also been calculated to investigate oxygen covalency of

  2. Metastability at the Yield-Stress Transition in Soft Glasses

    Directory of Open Access Journals (Sweden)

    Matteo Lulli

    2018-05-01

    Full Text Available We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable “fluidized” state, which relaxes back to a metastable “solid” state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

  3. Formation of bulk metallic glasses in the Fe-M-Y-B (M = transition metal) system

    Energy Technology Data Exchange (ETDEWEB)

    Huang, X.M. [International Center for New-Structured Materials (ICNSM) and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Chang, C.T. [Institute for Material Research, Tohoku University, Sendai 980-8577 (Japan); Chang, Z.Y.; Wang, X.D.; Cao, Q.P. [International Center for New-Structured Materials (ICNSM) and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Shen, B.L.; Inoue, A. [Institute for Material Research, Tohoku University, Sendai 980-8577 (Japan); Jiang, J.Z. [International Center for New-Structured Materials (ICNSM) and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)], E-mail: jiangjz@zju.edu.cn

    2008-07-28

    In this work, quaternary Fe{sub 72-x}M{sub x}Y{sub 6}B{sub 22} (M = Ni, Co and Mo) bulk metallic glasses (BMGs) have been developed. It is found that a fully amorphous Fe{sub 68}Mo{sub 4}Y{sub 6}B{sub 22} cylindrical rod with 6.5 mm in diameter can be prepared by copper mold injection. These alloys have a high glass transition temperature of about 900 K with high fracture strengths up to about 3 GPa although they are still brittle. Magnetic measurements reveal that they are ferromagnetic at ambient temperature with low coercive force of about 2 A/m, saturation magnetization of about 0.7 T and effective permeability of about 7000 at 100 kHz. The newly developed Fe-based quaternary alloys exhibit excellent combination properties: superior glass forming ability (GFA), high glass transition temperature, and soft magnetic properties, which could have potential applications in electronic industries. Furthermore, the effect of Mo addition on GFA in the Fe-Y-B BMG system has been discussed compared with those of Ni and Co additions.

  4. Spin-glass-like transition in the majority-vote model with anticonformists

    Science.gov (United States)

    Krawiecki, Andrzej

    2018-03-01

    Majority-vote model on scale-free networks and random graphs is investigated in which a randomly chosen fraction p of agents (called anticonformists) follows an antiferromagnetic update rule, i.e., they assume, with probability governed by a parameter q (0 transition from a disordered (paramagnetic) state to a spin-glass-like state, characterized by a non-zero value of the spin-glass order parameter measuring the overlap of agents' opinions in two replicas of the system, and simultaneously by the magnetization close to zero. In the case of the model on scale-free networks the critical value of the parameter q weakly depends on the details of the degree distribution. As p is decreased, the critical value of q falls quickly to zero and only the disordered phase is observed. On the other hand, for p close to zero for decreasing q the usual ferromagnetic transition is observed.

  5. Isoviscosity lines and the liquid-glass transition in simple liquids.

    Science.gov (United States)

    Fomin, Yu D; Brazhkin, V V; Ryzhov, V N

    2012-07-01

    This article presents the study of the generic behavior of viscosity of liquids based on some simple theoretical models, the soft-spheres and Lennard-Jones systems. The use of these simple models allows us to investigate in detail the viscosity behavior in a wide range of temperatures and pressures including the high-temperature-high-pressure limits. Based on the simulation results, we discuss the shape of isoviscosity lines and analyze the glass transition at high temperatures and high pressures. Despite the fact that the viscosity drastically increases in the limit of high temperatures and high pressures along the melting line, the relaxation time rapidly decreases in this region, and the system becomes further from the glass transition.

  6. Electronic and ionic conductivity studies on microwave synthesized glasses containing transition metal ions

    Directory of Open Access Journals (Sweden)

    Basareddy Sujatha

    2017-01-01

    Full Text Available Glasses in the system xV2O5·20Li2O·(80 − x [0.6B2O3:0.4ZnO] (where 10 ≤ x ≤ 50 have been prepared by a simple microwave method. Microwave synthesis of materials offers advantages of efficient transformation of energy throughout the volume in an effectively short time. Conductivity in these glasses was controlled by the concentration of transition metal ion (TMI. The dc conductivity follows Arrhenius law and the activation energies determined by regression analysis varies with the content of V2O5 in a non-linear passion. This non-linearity is due to different conduction mechanisms operating in the investigated glasses. Impedance and electron paramagnetic resonance (EPR spectroscopic studies were performed to elucidate the nature of conduction mechanism. Cole–cole plots of the investigated glasses consist of (i single semicircle with a low frequency spur, (ii two depressed semicircles and (iii single semicircle without spur, which suggests the operation of two conduction mechanisms. EPR spectra reveal the existence of electronic conduction between aliovalent vanadium sites. Further, in highly modified (10V2O5 mol% glasses Li+ ion migration dominates.

  7. Effect of alkali content on AC conductivity of borate glasses containing two transition metals

    International Nuclear Information System (INIS)

    Kashif, I.; Rahman, Samy A.; Soliman, A.A.; Ibrahim, E.M.; Abdel-Khalek, E.K.; Mostafa, A.G.; Sanad, A.M.

    2009-01-01

    Sodium borate glasses containing iron and molybdenum ions with the total concentration of transition ions constant and gradual substitution of sodium oxide (network modifier) by borate oxide (network former) was prepared. Densities, molar volume, DC and AC conductivities are measured. The trends of these properties are attributed to changes in the glass network structure. Their DC and AC conductivity increased with increasing NaO concentration. The increase of AC conductivity of sodium borate glasses is attributed to the chemical composition and the hopping mechanism of conduction. Measurements of the dielectric constant (ε) and dielectric loss (tan δ) as a function of frequency (50 Hz-100 kHz) and temperature (RT-600 K) indicate that the increase in dielectric constant and loss (ε and tan δ) values with increasing sodium ion content could be attributed to the assumption that Fe and Mo ions tend to assume network-forming position in the glass compositions studied. The variation of the value of frequency exponent s for all glass samples as the function of temperature at a definite frequency indicates that the value of s decreases with increasing the temperature which agrees with the correlated barrier-hopping (CBH) model.

  8. Hard sphere-like glass transition in eye lens α-crystallin solutions.

    Science.gov (United States)

    Foffi, Giuseppe; Savin, Gabriela; Bucciarelli, Saskia; Dorsaz, Nicolas; Thurston, George M; Stradner, Anna; Schurtenberger, Peter

    2014-11-25

    We study the equilibrium liquid structure and dynamics of dilute and concentrated bovine eye lens α-crystallin solutions, using small-angle X-ray scattering, static and dynamic light scattering, viscometry, molecular dynamics simulations, and mode-coupling theory. We find that a polydisperse Percus-Yevick hard-sphere liquid-structure model accurately reproduces both static light scattering data and small-angle X-ray scattering liquid structure data from α-crystallin solutions over an extended range of protein concentrations up to 290 mg/mL or 49% vol fraction and up to ca. 330 mg/mL for static light scattering. The measured dynamic light scattering and viscosity properties are also consistent with those of hard-sphere colloids and show power laws characteristic of an approach toward a glass transition at α-crystallin volume fractions near 58%. Dynamic light scattering at a volume fraction beyond the glass transition indicates formation of an arrested state. We further perform event-driven molecular dynamics simulations of polydisperse hard-sphere systems and use mode-coupling theory to compare the measured dynamic power laws with those of hard-sphere models. The static and dynamic data, simulations, and analysis show that aqueous eye lens α-crystallin solutions exhibit a glass transition at high concentrations that is similar to those found in hard-sphere colloidal systems. The α-crystallin glass transition could have implications for the molecular basis of presbyopia and the kinetics of molecular change during cataractogenesis.

  9. Dynamic and thermodynamic characteristics associated with the glass transition of amorphous trehalose-water mixtures.

    Science.gov (United States)

    Weng, Lindong; Elliott, Gloria D

    2014-06-21

    The glass transition temperature Tg of biopreservative formulations is important for predicting the long-term storage of biological specimens. As a complementary tool to thermal analysis techniques, which are the mainstay for determining Tg, molecular dynamics simulations have been successfully applied to predict the Tg of several protectants and their mixtures with water. These molecular analyses, however, rarely focused on the glass transition behavior of aqueous trehalose solutions, a subject that has attracted wide scientific attention via experimental approaches. Important behavior, such as hydrogen-bonding dynamics and self-aggregation has yet to be explored in detail, particularly below, or in the vicinity of, Tg. Using molecular dynamics simulations of several dynamic and thermodynamic properties, this study reproduced the supplemented phase diagram of trehalose-water mixtures (i.e., Tg as a function of the solution composition) based on experimental data. The structure and dynamics of the hydrogen-bonding network in the trehalose-water systems were also analyzed. The hydrogen-bonding lifetime was determined to be an order of magnitude higher in the glassy state than in the liquid state, while the constitution of the hydrogen-bonding network exhibited no noticeable change through the glass transition. It was also found that trehalose molecules preferred to form small, scattered clusters above Tg, but self-aggregation was substantially increased below Tg. The average cluster size in the glassy state was observed to be dependent on the trehalose concentration. Our findings provided insights into the glass transition characteristics of aqueous trehalose solutions as they relate to biopreservation.

  10. Effects of molecular weight on the glass transition temperature in Durolon polycarbonate

    International Nuclear Information System (INIS)

    Miranda, Adelina; Sciani, Valdir

    1995-01-01

    The effect of variation of the dose rate on degradation mechanism of PC Durolon irradiated with gamma rays was determined trough out intrinsic viscosity and thermal analysis of DSC-type measurements. The results showed a linear relationship between the glass transition temperature and the viscosimetric average molecular weight. From the results it's shown that with an increased of the dose rate it also increases the degradation of the material. (author). 12 refs., 3 figs

  11. Spin glass transition in a thin-film NiO/permalloy bilayer

    Science.gov (United States)

    Ma, Tianyu; Urazhdin, Sergei

    2018-02-01

    We experimentally study magnetization aging in a thin-film NiO/permalloy bilayer. Aging characteristics are nearly independent of temperature below the exchange bias blocking temperature TB, but rapidly vary above it. The dependence on the magnetic history qualitatively changes across TB. The observed behaviors are consistent with the spin glass transition at TB, with significant implications for magnetism and magnetoelectronic phenomena in antiferromagnet/ferromagnet bilayers.

  12. Self-bonding in an amorphous polymer below the glass transition

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Bach, Anders; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    was found to develop with (th)1/2 at Th = Tg-bulk - 33 °C (where Tg-bulk is the glass-transition temperature of the bulk sample), and log G was found to develop with 1/Th at Tg-bulk - 43 °C Th Tg-bulk - 23 °C. The smallest measured value of G = 1.4 J/m2 was at least one order of magnitude larger than...

  13. DWPF glass transition temperatures - What they are and why they are important

    International Nuclear Information System (INIS)

    Marra, S.L.; Applewhite-Ramsey, A.L.; Jantzen, C.M.

    1991-01-01

    The Department of Energy has defined a set of requirements for the DWPF canistered waste form which must be met in order to assure compatibility with, and acceptance by, the first geologic repository. These requirements are the Waste Acceptance Preliminary Specifications (WAPS). The WAPS require DWPF to report glass transition temperatures for the projected range of compositions. This information will be used by the repository to establish waste package design limits

  14. Determination of the glass transition temperature: methods correlation and structural heterogeneity

    OpenAIRE

    Hutchinson, John M.

    2009-01-01

    The definition of the glass transition temperature, Tg, is recalled and its experimental determination by various techniques is reviewed. The diversity of values of Tg obtained by the different methods is discussed, with particular attention being paid to Differential Scanning Calorimetry (DSC) and to dynamic techniques such as Dynamic Mechanical Thermal Analysis (DMTA) and Temperature Modulated DSC (TMDSC). This last technique, TMDSC, in particular, is considered in respect of ways in which ...

  15. Ellipsometry measurements of glass transition breadth in bulk films of random, block, and gradient copolymers.

    Science.gov (United States)

    Mok, M M; Kim, J; Marrou, S R; Torkelson, J M

    2010-03-01

    Bulk films of random, block and gradient copolymer systems were studied using ellipsometry to demonstrate the applicability of the numerical differentiation technique pioneered by Kawana and Jones for studying the glass transition temperature (T (g)) behavior and thermal expansivities of copolymers possessing different architectures and different levels of nanoheterogeneity. In a series of styrene/n -butyl methacrylate (S/nBMA) random copolymers, T (g) breadths were observed to increase from approximately 17( degrees ) C in styrene-rich cases to almost 30( degrees ) C in nBMA-rich cases, reflecting previous observations of significant nanoheterogeneity in PnBMA homopolymers. The derivative technique also revealed for the first time a substantial increase in glassy-state expansivity with increasing nBMA content in S/nBMA random copolymers, from 1.4x10(-4) K-1 in PS to 3.5x10(-4) K-1 in PnBMA. The first characterization of block copolymer T (g) 's and T (g) breadths by ellipsometry is given, examining the impact of nanophase-segregated copolymer structure on ellipsometric measurements of glass transition. The results show that, while the technique is effective in detecting the two T (g) 's expected in certain block copolymer systems, the details of the glass transition can become suppressed in ellipsometry measurements of a rubbery minor phase under conditions where the matrix is glassy; meanwhile, both transitions are easily discernible by differential scanning calorimetry. Finally, broad glass transition regions were measured in gradient copolymers, yielding in some cases extraordinary T (g) breadths of 69- 71( degrees ) C , factors of 4-5 larger than the T (g) breadths of related homopolymers and random copolymers. Surprisingly, one gradient copolymer demonstrated a slightly narrower T (g) breadth than the S/nBMA random copolymers with the highest nBMA content. This highlights the fact that nanoheterogeneity relevant to the glass transition response in selected

  16. Liquid -to-glass transition in bulk glass-forming Cu55-xZr45Agx alloys using molecular dynamic simulations

    Directory of Open Access Journals (Sweden)

    Celtek M.

    2011-05-01

    Full Text Available We report results from molecular dynamics (MD studies concerning the microscopic structure of the ternary, bulk metallic glass-forming Cu55-x Zr45Agx (x=0,10,20 alloys using tight-binding potentials. Understanding of the nature of Glass Forming Ability (GFA of studied alloys, GFA parameters, glass transition temperature (T-g, melting temperature (T-m, reduced glass transition temperature (T-g/T-m, the supercooled liquid region and other parameters were simulated and compared with experiments. The computed pair distribution functions reproduce well experimental x-ray data of Inoue and co-workers. Structure analysis of the Cu-Zr-Ag alloy based on MD simulation will be also presented

  17. Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

    International Nuclear Information System (INIS)

    Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua; Zhao, Lijuan

    2016-01-01

    Tm 3+ ions doped β-PbF 2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm 3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O h to D 4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm 3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field

  18. Transition to Glass: Pilot Training for High-Technology Transport Aircraft

    Science.gov (United States)

    Wiener, Earl L.; Chute, Rebecca D.; Moses, John H.

    1999-01-01

    This report examines the activities of a major commercial air carrier between 1993 and late 1996 as it acquired an advanced fleet of high-technology aircraft (Boeing 757). Previously, the airline's fleet consisted of traditional (non-glass) aircraft, and this report examines the transition from a traditional fleet to a glass one. A total of 150 pilots who were entering the B-757 transition training volunteered for the study, which consisted of three query phases: (1) first day of transition training, (2) 3 to 4 months after transition training, and (3) 12 to 14 months after initial operating experience. Of these initial 150 pilots, 99 completed all three phases of the study, with each phase consisting of probes on attitudes and experiences associated with their training and eventual transition to flying the line. In addition to the three questionnaires, 20 in-depth interviews were conducted. Although the primary focus of this study was on the flight training program, additional factors such as technical support, documentation, and training aids were investigated as well. The findings generally indicate that the pilot volunteers were highly motivated and very enthusiastic about their training program. In addition, the group had low levels of apprehension toward automation and expressed a high degree of satisfaction toward their training. However, there were some concerns expressed regarding the deficiencies in some of the training aids and lack of a free-play flight management system training device.

  19. Characterization of the glass transition of water predicted by molecular dynamics simulations using nonpolarizable intermolecular potentials.

    Science.gov (United States)

    Kreck, Cara A; Mancera, Ricardo L

    2014-02-20

    Molecular dynamics simulations allow detailed study of the experimentally inaccessible liquid state of supercooled water below its homogeneous nucleation temperature and the characterization of the glass transition. Simple, nonpolarizable intermolecular potentials are commonly used in classical molecular dynamics simulations of water and aqueous systems due to their lower computational cost and their ability to reproduce a wide range of properties. Because the quality of these predictions varies between the potentials, the predicted glass transition of water is likely to be influenced by the choice of potential. We have thus conducted an extensive comparative investigation of various three-, four-, five-, and six-point water potentials in both the NPT and NVT ensembles. The T(g) predicted from NPT simulations is strongly correlated with the temperature of minimum density, whereas the maximum in the heat capacity plot corresponds to the minimum in the thermal expansion coefficient. In the NVT ensemble, these points are instead related to the maximum in the internal pressure and the minimum of its derivative, respectively. A detailed analysis of the hydrogen-bonding properties at the glass transition reveals that the extent of hydrogen-bonds lost upon the melting of the glassy state is related to the height of the heat capacity peak and varies between water potentials.

  20. Low-density to high-density transition in Ce75Al23Si2 metallic glass

    International Nuclear Information System (INIS)

    Zeng, Q S; Lou, H B; Gong, Y; Wang, X D; Jiang, J Z; Fang, Y Z; Wu, F M; Yang, K; Li, A G; Yan, S; Yu, X H; Lathe, C

    2010-01-01

    Using in situ high-pressure x-ray diffraction (XRD), we observed a pressure-induced polyamorphic transition from the low-density amorphous (LDA) state to the high-density amorphous (HDA) state in Ce 75 Al 23 Si 2 metallic glass at about 2 GPa and 300 K. The thermal stabilities of both LDA and HDA metallic glasses were further investigated using in situ high-temperature and high-pressure XRD, which revealed different pressure dependences of the onset crystallization temperature (T x ) between them with a turning point at about 2 GPa. Compared with Ce 75 Al 25 metallic glass, minor Si doping shifts the onset polyamorphic transition pressure from 1.5 to 2 GPa and obviously stabilizes both LDA and HDA metallic glasses with higher T x and changes their slopes dT x /dP. The results obtained in this work reveal another polyamorphous metallic glass system by minor alloying (e.g. Si), which could modify the transition pressure and also properties of LDA and HDA metallic glasses. The minor alloying effect reported here is valuable for the development of more polyamorphous metallic glasses, even multicomponent bulk metallic glasses with modified properties, which will trigger more investigations in this field and improve our understanding of polyamorphism and metallic glasses.

  1. Glasses

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  2. First Clear-Cut Experimental Evidence of a Glass Transition in a Polymer with Intrinsic Microporosity: PIM-1.

    Science.gov (United States)

    Yin, Huajie; Chua, Yeong Zen; Yang, Bin; Schick, Christoph; Harrison, Wayne J; Budd, Peter M; Böhning, Martin; Schönhals, Andreas

    2018-04-19

    Polymers with intrinsic microporosity (PIMs) represent a novel, innovative class of materials with great potential in various applications from high-performance gas-separation membranes to electronic devices. Here, for the first time, for PIM-1, as the archetypal PIM, fast scanning calorimetry provides definitive evidence of a glass transition ( T g = 715 K, heating rate 3 × 10 4 K/s) by decoupling the time scales responsible for glass transition and decomposition. Because the rigid molecular structure of PIM-1 prevents any conformational changes, small-scale bend and flex fluctuations must be considered the origin of its glass transition. This result has strong implications for the fundamental understanding of the glass transition and for the physical aging of PIMs and other complex polymers, both topical problems of materials science.

  3. Optical transitions of Tm3+ in oxyfluoride glasses and compositional and thermal effect on upconversion luminescence of Tm3+/Yb3+-codoped oxyfluoride glasses.

    Science.gov (United States)

    Feng, Li; Wu, Yinsu; Liu, Zhuo; Guo, Tao

    2014-01-24

    Optical properties of Tm(3+)-doped SiO2-BaF2-ZnF2 glasses have been investigated on the basis of the Judd-Ofelt theory. Judd-Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Tm(3+)/Yb(3+)-codoped SiO2-BaF2-ZnF2 glasses under 980 nm excitation. The effects of composition, concentration of the doping ions, temperature, and excitation pump power on the upconversion emissions were also systematically studied. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. The peculiar behavior of the glass transition temperature of amorphous drug-polymer films coated on inert sugar spheres.

    Science.gov (United States)

    Dereymaker, Aswin; Van Den Mooter, Guy

    2015-05-01

    Fluid bed coating has been proposed in the past as an alternative technology for manufacturing of drug-polymer amorphous solid dispersions, or so-called glass solutions. It has the advantage of being a one-step process, and thus omitting separate drying steps, addition of excipients, or manipulation of the dosage form. In search of an adequate sample preparation method for modulated differential scanning calorimetry analysis of beads coated with glass solutions, glass transition broadening and decrease of the glass transition temperature (Tg ) were observed with increasing particle size of crushed coated beads and crushed isolated films of indomethacin (INDO) and polyvinylpyrrolidone (PVP). Substituting INDO with naproxen gave comparable results. When ketoconazole was probed or the solvent in INDO-PVP films was switched to dichloromethane (DCM) or a methanol-DCM mixture, two distinct Tg regions were observed. Small particle sizes had a glass transition in the high Tg region, and large particle sizes had a glass transition in the low Tg region. This particle size-dependent glass transition was ascribed to different residual solvent amounts in the bulk and at the surface of the particles. A correlation was observed between the deviation of the Tg from that calculated from the Gordon-Taylor equation and the amount of residual solvent at the Tg of particles with different sizes. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  5. Effect of In-situ Cure on Measurement of Glass Transition Temperatures in High-temperature Thermosetting Polymers

    Science.gov (United States)

    2015-01-01

    TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING POLYMERS 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...illustrated the difficulties inherent in measurement of the glass transition temperature of this high-temperature thermosetting polymer via dynamic...copyright protection in the United States. EFFECT OF IN-SITU CURE ON MEASUREMENT OF GLASS TRANSITION TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING

  6. The influence of gamma radiation on the molecular weight and glass transition of PLLA and HAp/PLLA nanocomposite

    International Nuclear Information System (INIS)

    Milicevic, D.; Trifunovic, S.; Dojcilovic, J.; Ignjatovic, N.; Suljovrujic, E.

    2010-01-01

    The influence of gamma radiation on the molecular weight and glass transition behaviour of poly-L-lactide (PLLA) and hydroxyapatite/poly-L-lactide (HAp/PLLA) nanocomposite has been studied. Since PLLA exposed to high-energy radiation in the presence of air is prone to chain scission reactions and large degradation, changes in molecular weight were obtained by gel permeation chromatography (GPC). Alterations in the glass transition behaviour were investigated by differential scanning calorimetry (DSC). The apparent activation energy (ΔH*) for glass transition was determined on the basis of the heating rate dependence of the glass transition temperature (T g ). Our findings support the fact that chain scission is the main reason for the decrease of T g and ΔH* with the absorbed dose. Furthermore, more intensive chain scission degradation of PLLA was observed in HAp/PLLA and can only be ascribed to the presence of HAp nanoparticles. Consequently, initial differences in the glass transition temperature and/or apparent activation energy of PLLA and HAp/PLLA became more pronounced with absorbed dose. This study reveals that radiation-induced changes in molecular weight and glass transition temperature occur in a predictable and fairly accurate manner. Therefore, gamma radiation can be used not only for sterilization but also for tailoring desirable end-use properties of these biomaterials.

  7. Thermal lens and interferometric method for glass transition and thermo physical properties measurements in Nd2O3 doped sodium zincborate glass.

    Science.gov (United States)

    Astrath, N G C; Steimacher, A; Rohling, J H; Medina, A N; Bento, A C; Baesso, M L; Jacinto, C; Catunda, T; Lima, S M; Karthikeyan, B

    2008-12-22

    In this work the time resolved thermal lens method is combined with interferometric technique, the thermal relaxation calorimetry, photoluminescence and lifetime measurements to determine the thermo physical properties of Nd(2)O(3) doped sodium zincborate glass as a function of temperature up to the glass transition region. Thermal diffusivity, thermal conductivity, fluorescence quantum efficiency, linear thermal expansion coefficient and thermal coefficient of electronic polarizability were determined. In conclusion, the results showed the ability of thermal lens and interferometric methods to perform measurements very close to the phase transition region. These techniques provide absolute values for the measured physical quantities and are advantageous when low scan rates are required.

  8. Quantum percolation phase transition and magnetoelectric dipole glass in hexagonal ferrites

    Science.gov (United States)

    Rowley, S. E.; Vojta, T.; Jones, A. T.; Guo, W.; Oliveira, J.; Morrison, F. D.; Lindfield, N.; Baggio Saitovitch, E.; Watts, B. E.; Scott, J. F.

    2017-07-01

    Hexagonal ferrites not only have enormous commercial impact (£2 billion/year in sales) due to applications that include ultrahigh-density memories, credit-card stripes, magnetic bar codes, small motors, and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbF e12 -xG axO19 to zero by chemical substitution x . The phase transition boundary is found to vary as TN˜(1-x /xc ) 2 /3 with xc very close to the calculated spin percolation threshold, which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven. We find that this produces a form of compositionally tuned, insulating, ferrimagnetic quantum criticality. Close to the zero-temperature phase transition, we observe the emergence of an electric dipole glass induced by magnetoelectric coupling. The strong frequency behavior of the glass freezing temperature Tm has a Vogel-Fulcher dependence with Tm finite, or suppressed below zero in the zero-frequency limit, depending on composition x . These quantum-mechanical properties, along with the multiplicity of low-lying modes near the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.

  9. Slow dynamics and glass transition in simulated free-standing polymer films: a possible relation between global and local glass transition temperatures

    International Nuclear Information System (INIS)

    Peter, S; Meyer, H; Baschnagel, J; Seemann, R

    2007-01-01

    We employ molecular dynamics simulations to explore the influence that the surface of a free-standing polymer film exerts on its structural relaxation when the film is cooled toward the glass transition. Our simulations are concerned with the features of a coarse-grained bead-spring model in a temperature regime above the critical temperature T c of mode-coupling theory. We find that the film dynamics is spatially heterogeneous. Monomers at the free surface relax much faster than they would in the bulk at the same temperature T. The fast relaxation of the surface layer continuously turns into bulk-like relaxation with increasing distance y from the surface. This crossover remains smooth for all T, but its range grows on cooling. We show that it is possible to associate a gradient in critical temperatures T c (y) with the gradient in the relaxation dynamics. This finding is in qualitative agreement with experimental results on supported polystyrene (PS) films (Ellison and Torkelson 2003 Nat. Mater. 2 695). Furthermore we show that the y dependence of T c (y) can be expressed in terms of the depression of T c (h)-the global T c for a film of thickness h-if we assume that T c (h) is the arithmetic mean of T c (y) and parameterize the depression of T c (h) by T c (h) = T c /(1+h 0 /h), a formula suggested by Herminghaus et al (2001 Eur. Phys. J. E 5 531) for the reduction of the glass transition temperature in supported PS films. We demonstrate the validity of this formula by comparing our simulation results to results from other simulations and experiments

  10. Correlation between physical properties and ultrasonic relaxation parameters in transition metal tellurite glasses

    Science.gov (United States)

    Abd El-Moneim, A.

    2003-07-01

    The correlation between activation energy of ultrasonic relaxation process through the temperature range from 140 to 300 K and some physical properties has been investigated in pure TeO 2 and transition metal TeO 2-V 2O 5 and TeO 2-MoO 3 glasses according to Bridge and Patel's theory. The oxygen density (loss centers), number of two-well systems, hopping distance and mechanical relaxation time have been calculated in these glasses from the data of density, bulk modulus and stretching force constant of the glass. It has been found that the acoustic activation energy increased linearly with both the oxygen density and the number of two-well systems. The correlation between the acoustic activation energy and bulk modulus was achieved through the stretching force constant of the network and other structural parameters. Moreover, the experimental values of activation energy (V) agree well with those calculated from an empirical equation presented in this study in the form V=2.9×10 -7 F( F/ K) 3.37, where F is the stretching force constant of the glass and K is the experimental bulk modulus.

  11. Spin-exchange interaction between transition metals and metalloids in soft-ferromagnetic metallic glasses

    Science.gov (United States)

    Das, Santanu; Choudhary, Kamal; Chernatynskiy, Aleksandr; Choi Yim, Haein; Bandyopadhyay, Asis K.; Mukherjee, Sundeep

    2016-06-01

    High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin-exchange interaction between metal and metalloid atoms, which typically constitute a metallic glass. Using an integrated experimental and molecular dynamics approach, we demonstrate the mechanism of electron interaction between transition metals and metalloids. Spin-exchange interactions were investigated for a Fe-Co metallic glass system of composition [(Co1-x Fe x )0.75B0.2Si0.05]96Cr4. The saturation magnetization increased with higher Fe concentration, but the trend significantly deviated from simple rule of mixtures. Ab initio molecular dynamics simulation was used to identify the ferromagnetic/anti-ferromagnetic interaction between the transition metals and metalloids. The overlapping band-structure and density of states represent ‘Stoner type’ magnetization for the amorphous alloys in contrast to ‘Heisenberg type’ in crystalline iron. The enhancement of magnetization by increasing iron was attributed to the interaction between Fe 3d and B 2p bands, which was further validated by valence-band study.

  12. The glass transition in nanoscaled confinement probed by dynamic mechanical spectroscopy

    International Nuclear Information System (INIS)

    Koppensteiner, J.

    2009-01-01

    A glass transition in a liquid is characterized by a massive change in some of its physical properties as viscosity η and molecular relaxation time τ, whereas no change in structure or long range order can be detected. Up to now an overall theory explaining the very nature of the glass transition and therewith all experimental findings is not available. Today's common approach, reaching back to Adams and Gibbs in 1963, is based on a cooperative rearrangement of molecules in groups whose size increases, when the glass transition is approached. In this picture a typical number of correlated molecules N corr,T form a compact cluster of a typical size ξ, predicted to be in the nm-range at T g . If this is true, nanoscaled confinement of a glass forming liquid should considerably influence this transition. In a pioneer work of 1991 Jackson and McKenna found a downshift ΔT g α 1/d in nm-sized pores of diameter d. This paper started a new eld of physics, the glass transition in confinement being investigated in experiment, simulation and theory. 20 years of research created partly contradictory results pointing to a large influence of side effects in confinement, opponent in their impact on T g . Both T g upshifts and downshifts were found in 2D and 3D conning geometries showing that spatially hindered molecular rearrangement is blurred by surface interactions and a negative pressure effect. An accurate investigation of side effects therefore is essential. The present thesis contributes to this rich eld and aims to help bridging the often cited gap between theory and experiments. For the rst time a mechanical approach is chosen and the dynamic elastic response of a mesoporous host matrix filled with a glass forming liquid is used to model the liquids behaviour across the glass transition. Low frequency dynamic mechanical measurements are proven to be very sensitive of the vitrification of the filling liquid. DMA turned out as a highly efficient and versatile tool

  13. Thermodynamic evidence for cluster ordering in Cu46Zr42Al7Y5 ribbons during glass transition

    DEFF Research Database (Denmark)

    Zheng, H.J.; Lv, Y.M.; Sun, Q.J.

    2016-01-01

    This work investigated the response of Cu46Zr42Al7Y5 glass ribbons to both dynamic and static heating using differential scanning calorimeter (DSC). The DSC curve manifests three exothermic responses to dynamic heating, among which the first and the third one are the signatures of the normal sub......-Tg (Tg, glass transition temperature) relaxation and the crystallization process, respectively. The second one is attributed to a partial overlap between the endothermic response to the glass transition and the exothermic response to the formation of ordered clusters. The cluster ordering, which begins...... at the final stage of glass transition, has been verified by the differences in the activation energy of the sub-Tg relaxation, the cluster ordering and primary crystallization for both the as-spun and annealed ribbons. The cluster ordering could be driven by the large difference between the Zr–Y mixing...

  14. Experimental signatures of a nonequilibrium phase transition governing the yielding of a soft glass.

    Science.gov (United States)

    Hima Nagamanasa, K; Gokhale, Shreyas; Sood, A K; Ganapathy, Rajesh

    2014-06-01

    We present direct experimental signatures of a nonequilibrium phase transition associated with the yield point of a prototypical soft solid-a binary colloidal glass. By simultaneously quantifying single-particle dynamics and bulk mechanical response, we identified the threshold for the onset of irreversibility with the yield strain. We extracted the relaxation time from the transient behavior of the loss modulus and found that it diverges in the vicinity of the yield strain. This critical slowing down is accompanied by a growing correlation length associated with the size of regions of high Debye-Waller factor, which are precursors to yield events in glasses. Our results affirm that the paradigm of nonequilibrium critical phenomena is instrumental in achieving a holistic understanding of yielding in soft solids.

  15. Glass Transitions and Low-Frequency Dynamics of Room-Temperature Ionic Liquids

    International Nuclear Information System (INIS)

    Yamamuro, O.; Inamura, Y.; Hayashi, S.; Hamaguchi, H.

    2006-01-01

    We have measured the heat capacity and neutrion quasi- and inelastic scattering spectra of some salts of 1-butyl-3-methylimidazolium ion bmim+, which is a typical cation of room-temperature ionic liquids, and its derivatives. The heat capacity measurements revealed that the room-temperature ionic liquids have glass transitions as molecular liquids. The temperature dependence of configurational entropy demonstrated that the room-temperature ionic liquids are 'fragile liquids'. Both heat capacity and inelastic neutron scattering data revealed that the glassy phases exhibit large low-energy excitations usually called 'boson peak'. The quasielastic neutron scattering data showed that so-called 'fast process' appears around Tg as in molecular and polymer glasses. The temperature dependence of the self-diffusion coefficient derived from the neutron scattering data indicated that the orientation of bmim+ ions and/or butyl-groups of bmim+ ions is highly disordered and very flexible in an ionic liquid phase

  16. Phase Transition in the Density of States of Quantum Spin Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Erdős, László, E-mail: lerdos@ist.ac.at [IST Austria (Austria); Schröder, Dominik, E-mail: schroeder.dominik@gmail.com [Ludwig-Maximilians-Universität München (Germany)

    2014-12-15

    We prove that the empirical density of states of quantum spin glasses on arbitrary graphs converges to a normal distribution as long as the maximal degree is negligible compared with the total number of edges. This extends the recent results of Keating et al. (2014) that were proved for graphs with bounded chromatic number and with symmetric coupling distribution. Furthermore, we generalise the result to arbitrary hypergraphs. We test the optimality of our condition on the maximal degree for p-uniform hypergraphs that correspond to p-spin glass Hamiltonians acting on n distinguishable spin- 1/2 particles. At the critical threshold p = n{sup 1/2} we find a sharp classical-quantum phase transition between the normal distribution and the Wigner semicircle law. The former is characteristic to classical systems with commuting variables, while the latter is a signature of noncommutative random matrix theory.

  17. Connection between slow and fast dynamics of molecular liquids around the glass transition

    International Nuclear Information System (INIS)

    Niss, Kristine; Dalle-Ferrier, Cecile; Frick, Bernhard; Russo, Daniela; Dyre, Jeppe; Alba-Simionesco, Christiane

    2010-01-01

    The mean-square displacement (MSD) was measured by neutron scattering at various temperatures and pressures for a number of molecular glass-forming liquids. The MSD is invariant along the glass-transition line at the pressure studied, thus establishing an 'intrinsic' Lindemann criterion for any given liquid. A one-to-one connection between the MSD's temperature dependence and the liquid's fragility is found when the MSD is evaluated on a time scale of ∼4 ns, but does not hold when the MSD is evaluated at shorter times. The findings are discussed in terms of the elastic model and the role of relaxations, and the correlations between slow and fast dynamics are addressed.

  18. Expected anomalies of the neutron cross section near the liquid-glass transition

    International Nuclear Information System (INIS)

    Gotze, W.

    1987-01-01

    In the frameworks of a microscopic theory the anomalies of the neutron cross section near the liquid-glass transition are discussed. The central concept of the theory is the correlation function for density fluctuations of wave vector q and frequency ω. Its absorptive part is proportional to the dynamical structure factor S(q, ω), this is the scattering law for coherent neutron scattering. Tagged particle motion is evaluated as well and it yields the incoherent neutron scattering cross section S i (q, ω) in. The predictions of the theory for S(q, ω) and Si (q, ω) a q-ω domain are given

  19. Effect of aging time on a glass transition of amorphous polymers at heating

    Czech Academy of Sciences Publication Activity Database

    Hadač, J.; Říha, Pavel; Slobodian, P.; Saha, P.; Kubát, J.

    2014-01-01

    Roč. 108, special issue 1 (2014), s. 59-65 ISSN 0009-2770 Grant - others:GA MŠk(CZ) EE.2.3.20.0104; GA MŠk(CZ) ED2.1.00/03.0111 Institutional research plan: CEZ:AV0Z20600510 Institutional support: RVO:67985874 Keywords : physical aging * glass transition * PMMA * relaxation function Subject RIV: BK - Fluid Dynamics Impact factor: 0.272, year: 2014 http://www.chemicke-listy.cz/docs/full/2014_s1_s59-s65.pdf

  20. Study of L-ascorbic acid (vitamin C)/H 2O mixture across glass transition

    Science.gov (United States)

    Migliardo, F.; Branca, C.; Faraone, A.; Magazù, S.; Migliardo, P.

    2001-07-01

    In this paper, we report quasi elastic neutron scattering (QENS) spectra of vitamin C aqueous solutions, obtained using MIBEMOL spectrometer (LLB). The main purpose of this work is to characterize the relaxational and vibrational properties of the Vitamin C/H 2O system below and above the glass transition temperature by analysing the low-frequency neutron scattering spectra. The determination of the relative weight of vibrational over relaxational contributions allows to get information on the fragility degree of this peculiar hydrogen-bond system.

  1. Acoustic and thermal anomalies in a liquid-glass transition of racemic S(+)-R(-) ketoprofen

    Science.gov (United States)

    Shibata, Tomohiko; Takayama, Haruki; Kim, Tae Hyun; Kojima, Seiji

    2014-01-01

    Acoustic and thermal properties of pharmaceutical racemic S(+)-R(-) ketoprofen were investigated in wide temperature range including glassy, supercooled liquid and liquid states by Brillouin scattering and temperature modulated DSC. Sound velocity and acoustic attenuation exhibited clear changes at 265 K indicating a liquid-glass transition and showed the typical structural relaxation above Tg. The high value of the fragility index m = 71 was determined by the dispersion of the complex heat capacity. New relaxation map was suggested in combination with previous study of dielectric measurement.

  2. Effect of γ-radiation on glass transition temperature of Poly(Bisphenol A carbonate) (PC)

    International Nuclear Information System (INIS)

    Kalkar, A.K.; Kundagol, S.

    1988-01-01

    Thin films of pure Poly(Bisphenol A carbonate) (PC) were γ-irradiated at room temperature from Co 60 source for varied doses, for the systematic study of γ-radiation on glass transition temperature (Tsub(g)) of PC. It was found that Tsub(g) of PC decreases with increasing doses. Irradiation of γ-rays on PC results in evolution of CO, CO 2 and H 2 from carbonate linkage and methyl group and which results in lowering of average mol.wt. of bul k polymer. Hence, overall increase in free volume increases chain mobility and thus reduces the Tsub(g). (author)

  3. Fuel Pellets from Wheat Straw: The Effect of Lignin Glass Transition and Surface Waxes on Pelletizing Properties

    DEFF Research Database (Denmark)

    Stelte, Wolfgang; Clemons, Craig; Holm, Jens K.

    2012-01-01

    and a high concentration of hydrophobic waxes on its outer surface that may limit the pellet strength. The present work studies the impact of the lignin glass transition on the pelletizing properties of wheat straw. Furthermore, the effect of surface waxes on the pelletizing process and pellet strength...... are investigated by comparing wheat straw before and after organic solvent extraction. The lignin glass transition temperature for wheat straw and extracted wheat straw is determined by dynamic mechanical thermal analysis. At a moisture content of 8%, transitions are identified at 53°C and 63°C, respectively....... Pellets are pressed from wheat straw and straw where the waxes have been extracted from. Two pelletizing temperatures were chosen—one below and one above the glass transition temperature of lignin. The pellets compression strength, density, and fracture surface were compared to each other. Pellets pressed...

  4. A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses

    Science.gov (United States)

    Wang, Shi-Qing; Cheng, Shiwang; Lin, Panpan; Li, Xiaoxiao

    2014-09-01

    This work formulates, at a molecular level, a phenomenological theoretical description of the brittle-ductile transition (BDT) in tensile extension, exhibited by all polymeric glasses of high molecular weight (MW). The starting point is our perception of a polymer glass (under large deformation) as a structural hybrid, consisting of a primary structure due to the van der Waals bonding and a chain network whose junctions are made of pairs of hairpins and function like chemical crosslinks due to the intermolecular uncrossability. During extension, load-bearing strands (LBSs) emerge between the junctions in the affinely strained chain network. Above the BDT, i.e., at "warmer" temperatures where the glass is less vitreous, the influence of the chain network reaches out everywhere by activating all segments populated transversely between LBSs, starting from those adjacent to LBSs. It is the chain network that drives the primary structure to undergo yielding and plastic flow. Below the BDT, the glassy state is too vitreous to yield before the chain network suffers a structural breakdown. Thus, brittle failure becomes inevitable. For any given polymer glass of high MW, there is one temperature TBD or a very narrow range of temperature where the yielding of the glass barely takes place as the chain network also reaches the point of a structural failure. This is the point of the BDT. A theoretical analysis of the available experimental data reveals that (a) chain pullout occurs at the BDT when the chain tension builds up to reach a critical value fcp during tensile extension; (b) the limiting value of fcp, extrapolated to far below the glass transition temperature Tg, is of a universal magnitude around 0.2-0.3 nN, for all eight polymers examined in this work; (c) pressurization, which is known [K. Matsushige, S. V. Radcliffe, and E. Baer, J. Appl. Polym. Sci. 20, 1853 (1976)] to make brittle polystyrene (PS) and poly(methyl methacrylate) (PMMA) ductile at room temperature

  5. A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses.

    Science.gov (United States)

    Wang, Shi-Qing; Cheng, Shiwang; Lin, Panpan; Li, Xiaoxiao

    2014-09-07

    This work formulates, at a molecular level, a phenomenological theoretical description of the brittle-ductile transition (BDT) in tensile extension, exhibited by all polymeric glasses of high molecular weight (MW). The starting point is our perception of a polymer glass (under large deformation) as a structural hybrid, consisting of a primary structure due to the van der Waals bonding and a chain network whose junctions are made of pairs of hairpins and function like chemical crosslinks due to the intermolecular uncrossability. During extension, load-bearing strands (LBSs) emerge between the junctions in the affinely strained chain network. Above the BDT, i.e., at "warmer" temperatures where the glass is less vitreous, the influence of the chain network reaches out everywhere by activating all segments populated transversely between LBSs, starting from those adjacent to LBSs. It is the chain network that drives the primary structure to undergo yielding and plastic flow. Below the BDT, the glassy state is too vitreous to yield before the chain network suffers a structural breakdown. Thus, brittle failure becomes inevitable. For any given polymer glass of high MW, there is one temperature TBD or a very narrow range of temperature where the yielding of the glass barely takes place as the chain network also reaches the point of a structural failure. This is the point of the BDT. A theoretical analysis of the available experimental data reveals that (a) chain pullout occurs at the BDT when the chain tension builds up to reach a critical value f(cp) during tensile extension; (b) the limiting value of f(cp), extrapolated to far below the glass transition temperature T(g), is of a universal magnitude around 0.2-0.3 nN, for all eight polymers examined in this work; (c) pressurization, which is known [K. Matsushige, S. V. Radcliffe, and E. Baer, J. Appl. Polym. Sci. 20, 1853 (1976)] to make brittle polystyrene (PS) and poly(methyl methacrylate) (PMMA) ductile at room

  6. Systematic expansion in the order parameter for replica theory of the dynamical glass transition.

    Science.gov (United States)

    Jacquin, Hugo; Zamponi, Francesco

    2013-03-28

    It has been shown recently that predictions from mode-coupling theory for the glass transition of hard-spheres become increasingly bad when dimensionality increases, whereas replica theory predicts a correct scaling. Nevertheless if one focuses on the regime around the dynamical transition in three dimensions, mode-coupling results are far more convincing than replica theory predictions. It seems thus necessary to reconcile the two theoretic approaches in order to obtain a theory that interpolates between low-dimensional, mode-coupling results, and "mean-field" results from replica theory. Even though quantitative results for the dynamical transition issued from replica theory are not accurate in low dimensions, two different approximation schemes--small cage expansion and replicated hyper-netted-chain (RHNC)--provide the correct qualitative picture for the transition, namely, a discontinuous jump of a static order parameter from zero to a finite value. The purpose of this work is to develop a systematic expansion around the RHNC result in powers of the static order parameter, and to calculate the first correction in this expansion. Interestingly, this correction involves the static three-body correlations of the liquid. More importantly, we separately demonstrate that higher order terms in the expansion are quantitatively relevant at the transition, and that the usual mode-coupling kernel, involving two-body direct correlation functions of the liquid, cannot be recovered from static computations.

  7. Electrical Conductivity, Relaxation and the Glass Transition: A New Look at a Familiar Phenomenon

    Science.gov (United States)

    Angel, Paul W.; Cooper, Alfred R.; DeGuire, Mark R.

    1996-01-01

    Annealed samples from a single melt of a 10 mol% K2O-90SiO2 glass were reheated to temperatures ranging from 450 to 800 C, held isothermally for 20 min, and then quenched in either air or a silicon oil bath. The complex impedance of both the annealed and quenched samples was measured as a function of temperature from 120 to 250 C using ac impedance spectroscopy from 1 Hz to 1 MHz. The dc conductivity, sigma(sub dc), was measured from the low frequency intercept of depressed semicircle fits to the complex impedance data. When the sigma(sub dc) at 150 C was plotted against soak temperature, the results fell into three separate regions that are explained in terms of the glass structural relaxation time, tau(sub S). This sigma(sub dc) plot provides a new way to look the glass transition range, Delta T(sub r). In addition, sigma(sub dc) was measured for different soak times at 550 C, from which an average relaxation time of 7.3 min was calculated. It was found that the size and position of the Delta T(sub r) is controlled by both the soak time and cooling rate.

  8. On the dynamics of liquids in their viscous regime approaching the glass transition.

    Science.gov (United States)

    Chen, Z; Angell, C A; Richert, R

    2012-07-01

    Recently, Mallamace et al. (Eur. Phys. J. E 34, 94 (2011)) proposed a crossover temperature, T(×), and claimed that the dynamics of many supercooled liquids follow an Arrhenius-type temperature dependence between T(×) and the glass transition temperature T(g). The opposite, namely super-Arrhenius behavior in this viscous regime, has been demonstrated repeatedly for molecular glass-former, for polymers, and for the majority of the exhaustively studied inorganic glasses of technological interest. Therefore, we subject the molecular systems of the Mallamace et al. study to a "residuals" analysis and include not only viscosity data but also the more precise data available from dielectric relaxation experiments over the same temperature range. Although many viscosity data sets are inconclusive due to their noise level, we find that Arrhenius behavior is not a general feature of viscosity in the T(g) to T(×) range. Moreover, the residuals of dielectric relaxation times with respect to an Arrhenius law clearly reveal systematic curvature consistent with super-Arrhenius behavior being an endemic feature of transport properties in this viscous regime. We also observe a common pattern of how dielectric relaxation times decouple slightly from viscosity.

  9. Meissner effects, vortex core states, and the vortex glass phase transition

    International Nuclear Information System (INIS)

    Huang, Ming.

    1991-01-01

    This thesis covers three topics involving Meissner effects and the resulting defect structures. The first is a study of Meissner effects in superconductivity and in systems with broken translational symmetry. The Meissner effect in the superconductors is a rigidity against external magnetic field caused by the breaking of the gauge symmetry. Other condensed matter systems also exhibit rigidities like this: The breaking of the translational symmetry in a cubic-liquid-crystal causes the system to expel twist deformations and the breaking of the translational symmetry in a nematic liquid crystal gives it a tendency to expel twist and bend deformations. In this thesis, the author studies these generalized Meissner effects in detail. The second is a study of the quasiparticle states bound to the vortex defect in superconductors. Scanning-tunneling-microscope measurements by Harald Hess et al. of the local density of states in a vortex core show a pronounced peak at small bias. These measurements contradict with previous theoretical calculations. Here, he solves the Bogoliubov equations to obtain the local density of states in the core and satisfactorily explain the experimental observations. He also predicted additional structure in the local density of states which were later observed in experiments. The third is a study of vortex dynamics in the presence of disorder. A mean field theory is developed for the recently proposed normal to superconducting vortex glass transition. Using techniques developed to study the critical dynamics of spin glasses, he calculates the mean field vortex glass phase boundary and the critical exponents

  10. Short range structural models of the glass transition temperatures and densities of 0.5Na2S + 0.5[xGeS2 + (1 - x)PS5/2] mixed glass former glasses.

    Science.gov (United States)

    Bischoff, Christian; Schuller, Katherine; Martin, Steve W

    2014-04-03

    The 0.5Na2S + 0.5[xGeS2 + (1 - x)PS5/2] mixed glass former (MGF) glass system exhibits a nonlinear and nonadditive negative change in the Na(+) ion conductivity as one glass former, PS5/2, is exchanged for the other, GeS2. This behavior, known as the mixed glass former effect (MGFE), is also manifest in a negative deviation from the linear interpolation of the glass transition temperatures (T(g)) of the binary end-member glasses, x = 0 and x = 1. Interestingly, the composition dependence of the densities of these ternary MGF glasses reveals a slightly positive MGFE deviation from a linear interpolation of the densities of the binary end-member glasses, x = 0 and x = 1. From our previous studies of the structures of these glasses using IR, Raman, and NMR spectroscopies, we find that a disproportionation reaction occurs between PS7/2(4-) and GeS3(2-) units into PS4(3-) and GeS5/2(1-) units. This disproportionation combined with the formation of Ge4S10(4-) anions from GeS5/2(1-) groups leads to the negative MGFE in T(g). A best-fit model of the T(g)s of these glasses was developed to quantify the amount of GeS5/2(1-) units that form Ge4S10(4-) molecular anions in the ternary glasses (∼ 5-10%). This refined structural model was used to develop a short-range structural model of the molar volumes, which shows that the slight densification of the ternary glasses is due to the improved packing efficiency of the germanium sulfide species.

  11. Treatments of intrinsic viscosity and glass transition temperature data of poly(2,6-dimethylphenylmethacrylate)

    International Nuclear Information System (INIS)

    Hamidi, Nasrollah; Massoudi, Ruhullah

    2003-01-01

    A useful relationship, ln(T g )=ln(T g,∞ )-m[η] -ν , between intrinsic viscosity and glass transition temperature for a series of homologous polymers was obtained by combining the Mark-Houwink-Kuhn-Sakurada (MHKS) relation for intrinsic viscosity and molecular mass, and the Fox-Flory equation for glass transition temperature and number-average molecular mass. This relationship was applied to poly(2,6-dimethylphenylmethacrylate) (PDMPh) in a variety of solvents (ideal to good) such as toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems. The parameter α estimated by this procedure in toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems are 0.50 6 , 0.51 1 , 0.56 7 , and 0.67 3 , respectively which are in agreement with those of Mark-Houwink-Kuhn-Sakurada values by less than 5% differences. The T g,∞ quantity estimated from this equation also is within the standard deviation of that obtained from the Fox-Flory method. The m quantity is increasing as the thermodynamic quality of the solvent improves, therefore, m may be considered as an indicator of coil conformations in a given solvent

  12. Structure and dynamics of soft repulsive colloidal suspensions in the vicinity of the glass transition.

    Science.gov (United States)

    Crassous, Jérôme J; Casal-Dujat, Lucia; Medebach, Martin; Obiols-Rabasa, Marc; Vincent, Romaric; Reinhold, Frank; Boyko, Volodymyr; Willerich, Immanuel; Menzel, Andreas; Moitzi, Christian; Reck, Bernd; Schurtenberger, Peter

    2013-08-20

    We use a combination of different scattering techniques and rheology to highlight the link between structure and dynamics of dense aqueous suspensions of soft repulsive colloids in the vicinity of a glass transition. Three different latex formulations with an increasing amount of the hydrophilic component resulting in either purely electrostatically or electrosterically stabilized suspensions are investigated. From the analysis of the static structure factor measured by small-angle X-ray scattering, we derive an effective volume fraction that includes contributions from interparticle interactions. We further investigate the dynamics of the suspensions using 3D cross-correlation dynamic light scattering (3DDLS) and rheology. We analyze the data using an effective hard sphere model and in particular compare the linear viscoelasticity and flow behavior to the predictions of mode coupling theory, which accounts for a purely kinetic glass transition determined by the equilibrium structure factor. We demonstrate that seemingly very different colloidal systems exhibit the same generic behavior when the effects from interparticle interactions are incorporated using an effective volume fraction description.

  13. Dielectric relaxation of 2-ethyl-1-hexanol around the glass transition by thermally stimulated depolarization currents.

    Science.gov (United States)

    Arrese-Igor, S; Alegría, A; Colmenero, J

    2015-06-07

    We explore new routes for characterizing the Debye-like and α relaxation in 2-ethyl-1-hexanol (2E1H) monoalcohol by using low frequency dielectric techniques including thermally stimulated depolarization current (TSDC) techniques and isothermal depolarization current methods. In this way, we have improved the resolution of the overlapped processes making it possible the analysis of the data in terms of a mode composition as expected for a chain-like response. Furthermore the explored ultralow frequencies enabled to study dynamics at relatively low temperatures close to the glass transition (Tg). Results show, on the one hand, that Debye-like and α relaxation timescales dramatically approach to each other upon decreasing temperature to Tg. On the other hand, the analysis of partial polarization TSDC data confirms the single exponential character of the Debye-like relaxation in 2E1H and rules out the presence of Rouse type modes in the scenario of a chain-like response. Finally, on crossing the glass transition, the Debye-like relaxation shows non-equilibrium effects which are further emphasized by aging treatment and would presumably emerge as a result of the arrest of the structural relaxation below Tg.

  14. In-Situ Phase Transition Control in the Supercooled State for Robust Active Glass Fiber.

    Science.gov (United States)

    Lv, Shichao; Cao, Maoqing; Li, Chaoyu; Li, Jiang; Qiu, Jianrong; Zhou, Shifeng

    2017-06-21

    The construction of a dopant-activated photonic composite is of great technological importance for various applications, including smart lighting, optical amplification, laser, and optical detection. The bonding arrangement around the introduced dopants largely determines the properties, yet it remains a daunting challenge to manipulate the local state of the matrix (i.e., phase) inside the transparent composite in a controllable manner. Here we demonstrate that the relaxation of the supercooled state enables in-situ phase transition control in glass. Benefiting from the unique local atom arrangement manner, the strategy offers the possibility for simultaneously tuning the chemical environment of the incorporated dopant and engineering the dopant-host interaction. This allows us to effectively activate the dopant with high efficiency (calculated as ∼100%) and profoundly enhance the dopant-host energy-exchange interaction. Our results highlight that the in-situ phase transition control in glass may provide new opportunities for fabrication of unusual photonic materials with intense broadband emission at ∼1100 nm and development of the robust optical detection unit with high compactness and broadband photon-harvesting capability (from X-ray to ultraviolet light).

  15. Elementary excitations and the phase transition in the bimodal Ising spin glass model

    International Nuclear Information System (INIS)

    Jinuntuya, N; Poulter, J

    2012-01-01

    We show how the nature of the phase transition in the two-dimensional bimodal Ising spin glass model can be understood in terms of elementary excitations. Although the energy gap with the ground state is expected to be 4J in the ferromagnetic phase, a gap 2J is in fact found if the finite lattice is wound around a cylinder of odd circumference L. This 2J gap is really a finite size effect that should not occur in the thermodynamic limit of the ferromagnet. The spatial influence of the frustration must be limited and not wrap around the system if L is large enough. In essence, the absence of 2J excitations defines the ferromagnetic phase without recourse to calculating the magnetization or investigating the system response to domain wall defects. This study directly investigates the response to temperature. We also estimate the defect concentration where the phase transition to the spin glass state occurs. The value p c = 0.1045(11) is in reasonable agreement with the literature

  16. Determination of Material Properties Near the Glass Transition Temperature for an Isogrid Boom

    Science.gov (United States)

    Blandino, Joseph R.; Woods-Vedeler, Jessica A. (Technical Monitor)

    2002-01-01

    Experiments were performed and results obtained to determine the temperature dependence of the modulus of elasticity for a thermoplastic isogrid tube. The isogrid tube was subjected to axial tensile loads of 0-100 lbf and strain was measured at room and elevated temperatures of 100, 120, 140, 160, 180, 190, and 200 F. These were based on tube manufacturer specifying an incorrect glass transition temperature of 210 F. Two protocols were used. For the first protocol the tube was brought to temperature and a tensile test performed. The tube was allowed to cool between tests. For the second protocol the tube was ramped to the desired test temperature and held. A tensile test was performed and the tube temperature ramped to the next test temperature. The second protocol spanned the entire test range. The strain rate was constant at 0.008 in/min. Room temperature tests resulted in the determination of an average modulus of 2.34 x 106 Psi. The modulus decreased above 100 F. At 140 F the modulus had decreased by 7.26%. The two test protocols showed good agreement below 160 F. At this point the glass transition temperature had been exceeded. The two protocols were not repeated because the tube failed.

  17. Glass transition of poly (methyl methacrylate) filled with nanosilica and core-shell structured silica

    DEFF Research Database (Denmark)

    Song, Yihu; Bu, Jing; Zuo, Min

    2017-01-01

    transition and segmental dynamics of PMMA in the nanocomposites prepared via solution casting was compared. The remarkable depression (≥10 °C) of glass transition temperature (Tg) induced by the incorporation of SiO2 and CS was both observed at low loadings. Here, different mechanisms were responsible...... for the effect of SiO2 and CS on the segmental acceleration of PMMA matrix. The formation of rigid amorphous fraction (RAF) layer around SiO2 with the thickness of 16.4 nm led to the adjacent molecular packing frustration, while the “lubrication” effect of nonwetting interface between the grafted crosslinked......Core-shell (CS) nanocomposite particles with 53.4 wt% cross-linked poly (methyl methacrylate) (PMMA) shell of 11.6 nm in thickness were fabricated via miniemulsion polymerization of methyl methacrylate in the presence of modified nanosilica. The influence of nanosilica and CS nanoparticles on glass...

  18. Thermodynamic Properties, Sorption Isotherms and Glass Transition Temperature of Cape Gooseberry (Physalis peruviana L.

    Directory of Open Access Journals (Sweden)

    Jessica López

    2014-01-01

    Full Text Available Adsorption and desorption isotherms of fresh and dried Cape gooseberry (Physalis peruviana L. were determined at three temperatures (20, 40 and 60 °C using a gravimetric technique. The data obtained were fitted to several models including Guggenheim-Anderson- De Boer (GAB, Brunauer-Emmett-Teller (BET, Henderson, Caurie, Smith, Oswin, Halsey and Iglesias-Chirife. A non-linear least square regression analysis was used to evaluate the models. The Iglesias-Chirife model fitted best the experimental data. Isosteric heat of sorption was also determined from the equilibrium sorption data using the Clausius-Clapeyron equation and was found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy-controlled sorption process. Glass transition temperature (Tg of Cape gooseberry was also determined by differential scanning calorimetry and modelled as a function of moisture content with the Gordon-Taylor, the Roos and the Khalloufi models, which proved to be excellent tools for predicting glass transition of Cape gooseberry.

  19. Criteria for solvent-induced chronic toxic encephalopathy: a systematic review

    NARCIS (Netherlands)

    van der Hoek, J. A.; Verberk, M. M.; Hageman, G.

    2000-01-01

    In 1985, a WHO Working Group presented diagnostic criteria and a classification for solvent-induced chronic toxic encephalopathy (CTE). In the same year, the "Workshop on neurobehavioral effects of solvents" in Raleigh, N.C., USA introduced a somewhat different classification for CTE. The objective

  20. Preparing poly (caprolactone) micro-particles through solvent-induced phase separation

    DEFF Research Database (Denmark)

    Li, Xiaoqiang; Kanjwal, Muzafar Ahmed; Stephansen, Karen

    2012-01-01

    Poly (caprolactone) (PCL) particles with the size distribution from 1 to 100 μm were prepared through solvent-induced phase separation, in which polyvinyl-alcohol (PVA) was used as the matrix-forming polymer to stabilize PCL particles. The cloud point data of PCL-acetone-water was determined...

  1. Quantitative determination of the specific heat and the glass transition of moist samples by temperature modulated differential scanning calorimetry.

    Science.gov (United States)

    Schubnell, M; Schawe, J E

    2001-04-17

    In differential scanning calorimetry (DSC), remnant moisture loss in samples often overlaps and distorts other thermal events, e.g. glass transitions. To separate such overlapping processes, temperature modulated DSC (TMDSC) has been widely used. In this contribution we discuss the quantitative determination of the heat capacity of a moist sample from TMDSC measurements. The sample was a spray-dried pharmaceutical compound run in different pans (hermetically-sealed pan, pierced lid pan [50 microm] and open pan). The apparent heat capacity was corrected for the remaining amount of moisture. Using this procedure we could clearly identify the glass transition of the dry and the moist sample. We found that a moisture content of about 6.2% shifts the glass transition by about 50 degrees C.

  2. SU-F-T-17: A Feasibility Study for the Transit Dosimetry with a Glass Dosimeter in Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S; Yoon, M [Korea University, Seoul (Korea, Republic of); Chung, W; Chung, M; Kim, D [Kyung Hee University Hospital at Gangdong, Gangdonggu, Seoul (Korea, Republic of)

    2016-06-15

    Purpose: Confirming the dose delivered to a patient is important to make sure the treatment quality and safety of the radiotherapy. Measuring a transit dose of the patient during the radiotherapy could be an interesting way to confirm the patient dose. In this study, we evaluated the feasibility of the transit dosimetry with a glass dosimeter in brachytherapy. Methods: We made a phantom that inserted the glass dosimeters and placed under patient lying on a couch for cervix cancer brachytherapy. The 18 glass dosimeters were placed in the phantom arranged 6 per row. A point putting 1cm vertically from the source was prescribed as 500.00 cGy. Solid phantoms of 0, 2, 4, 6, 8, 10 cm were placed between the source and the glass dosimeter. The transit dose was measured each thickness using the glass dosimeters and compared with a treatment planning system (TPS). Results: When the transit dose was smaller than 10 cGy, the average of the differences between measured values and calculated values by TPS was 0.50 cGy and the standard deviation was 0.69 cGy. If the transit dose was smaller than 100 cGy, the average of the error was 1.67 ± 4.01 cGy. The error to a point near the prescription point was −14.02 cGy per 500.00 cGy of the prescription dose. Conclusion: The distances from the sources to skin of the patient generally are within 10 cm for cervix cancer cases in brachytherapy. The results of this preliminary study showed the probability of the glass dosimeter as the transit dosimeter in brachytherapy.

  3. The ferromagnetic-spin glass transition in PdMn alloys: symmetry breaking of ferromagnetism and spin glass studied by a multicanonical method.

    Science.gov (United States)

    Kato, Tomohiko; Saita, Takahiro

    2011-03-16

    The magnetism of Pd(1-x)Mn(x) is investigated theoretically. A localized spin model for Mn spins that interact with short-range antiferromagnetic interactions and long-range ferromagnetic interactions via itinerant d electrons is set up, with no adjustable parameters. A multicanonical Monte Carlo simulation, combined with a procedure of symmetry breaking, is employed to discriminate between the ferromagnetic and spin glass orders. The transition temperature and the low-temperature phase are determined from the temperature variation of the specific heat and the probability distributions of the ferromagnetic order parameter and the spin glass order parameter at different concentrations. The calculation results reveal that only the ferromagnetic phase exists at x glass phase exists at x > 0.04, and that the two phases coexist at intermediate concentrations. This result agrees semi-quantitatively with experimental results.

  4. Glass transition in thaumatin crystals revealed through temperature-dependent radiation-sensitivity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Warkentin, Matthew, E-mail: maw64@cornell.edu; Thorne, Robert E. [Physics Department, Cornell University, Ithaca, New York (United States)

    2010-10-01

    Radiation damage to protein crystals exhibits two regimes of temperature-activated behavior between T = 300 and 100 K, with a crossover at the protein glass transition near 200 K. These results have implications for mechanistic studies of proteins and for structure determination when cooling to T = 100 K creates excessive disorder. The temperature-dependence of radiation damage to thaumatin crystals between T = 300 and 100 K is reported. The amount of damage for a given dose decreases sharply as the temperature decreases from 300 to 220 K and then decreases more gradually on further cooling below the protein-solvent glass transition. Two regimes of temperature-activated behavior were observed. At temperatures above ∼200 K the activation energy of 18.0 kJ mol{sup −1} indicates that radiation damage is dominated by diffusive motions in the protein and solvent. At temperatures below ∼200 K the activation energy is only 1.00 kJ mol{sup −1}, which is of the order of the thermal energy. Similar activation energies describe the temperature-dependence of radiation damage to a variety of solvent-free small-molecule organic crystals over the temperature range T = 300–80 K. It is suggested that radiation damage in this regime is vibrationally assisted and that the freezing-out of amino-acid scale vibrations contributes to the very weak temperature-dependence of radiation damage below ∼80 K. Analysis using the radiation-damage model of Blake and Phillips [Blake & Phillips (1962 ▶), Biological Effects of Ionizing Radiation at the Molecular Level, pp. 183–191] indicates that large-scale conformational and molecular motions are frozen out below T = 200 K but become increasingly prevalent and make an increasing contribution to damage at higher temperatures. Possible alternative mechanisms for radiation damage involving the formation of hydrogen-gas bubbles are discussed and discounted. These results have implications for mechanistic studies of proteins and for

  5. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

    Science.gov (United States)

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

    2014-07-01

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  6. Structural evolution during fragile-to-strong transition in CuZr(Al) glass-forming liquids

    DEFF Research Database (Denmark)

    Zhou, C.; Hu, L.N.; Sun, Q.J.

    2015-01-01

    In the present work, we show experimental evidence for the dynamic fragile-to-strong (F-S) transition in a series of CuZr(Al) glass-forming liquids (GFLs). A detailed analysis of the dynamics of 98 glass-forming liquids indicates that the F-S transition occurs around Tf-s ≈ 1.36 Tg. Using...... the hyperquenching-annealing-x-ray scattering approach, we have observed a three-stage evolution pattern of medium-range ordering (MRO) structures during the F-S transition, indicating a dramatic change of the MRO clusters around Tf-s upon cooling. The F-S transition in CuZr(Al) GFLs is attributed to the competition...... among the MRO clusters composed of different locally ordering configurations. A phenomenological scenario has been proposed to explain the structural evolution from the fragile to the strong phase in the CuZr(Al) GFLs....

  7. Effect of thermal history on mechanical properties of polyetheretherketone below the glass transition temperature

    Science.gov (United States)

    Cebe, Peggy; Chung, Shirley Y.; Hong, Su-Don

    1987-01-01

    The effect of thermal history on the tensile properties of polyetheretherketone neat resin films was investigated at different test temperatures (125, 25, and -100) using four samples: fast-quenched amorphous (Q); quenched, then crystallized at 180 C (C180); slowly cooled (for about 16 h) from the melt (SC); and air-cooled (2-3 h) from the melt (AC). It was found that thermal history significantly affects the tensile properties of the material below the glass transition. Fast quenched amorphous films were most tough, could be drawn to greatest strain before rupture, and undergo densification during necking; at the test temperature of -100 C, these films had the best ultimate mechanical properties. At higher temperatures, the semicrystalline films AC and C180 had properties that compared favorably with the Q films. The SC films exhibited poor mechanical properties at all test temperatures.

  8. Evaluation of glass transition temperature and dynamic mechanical properties of autopolymerized hard direct denture reline resins.

    Science.gov (United States)

    Takase, Kazuma; Watanabe, Ikuya; Kurogi, Tadafumi; Murata, Hiroshi

    2015-01-01

    This study assessed methods for evaluation of glass transition temperature (Tg) of autopolymerized hard direct denture reline resins using dynamic mechanical analysis and differential scanning calorimetry in addition to the dynamic mechanical properties. The Tg values of 3 different reline resins were determined using a dynamic viscoelastometer and differential scanning calorimeter, and rheological parameters were also determined. Although all materials exhibited higher storage modulus and loss modulus values, and a lower loss tangent at 37˚C with a higher frequency, the frequency dependence was not large. Tg values obtained by dynamic mechanical analysis were higher than those by differential scanning calorimetry and higher frequency led to higher Tg, while more stable Tg values were also obtained by that method. These results suggest that dynamic mechanical analysis is more advantageous for characterization of autopolymerized hard direct denture reline resins than differential scanning calorimetry.

  9. Higher-order glass-transition singularities in systems with short-ranged attractive potentials

    International Nuclear Information System (INIS)

    Goetze, W; Sperl, M

    2003-01-01

    Within the mode-coupling theory for the evolution of structural relaxation, the A 4 -glass-transition singularities are identified for systems of particles interacting with a hard-sphere repulsion complemented by different short-ranged potentials: Baxter's singular potential regularized by a large-wavevector cut-off, a model for the Asakura-Oosawa depletion attraction, a triangular potential, a Yukawa attraction, and a square-well potential. The regular potentials yield critical packing fractions, critical Debye-Waller factors, and critical amplitudes very close to each other. The elastic moduli and the particle localization lengths for corresponding states of the Yukawa system and the square-well system may differ by up to 20 and 10%, respectively

  10. Glass transition temperature of polymer nano-composites with polymer and filler interactions

    Science.gov (United States)

    Hagita, Katsumi; Takano, Hiroshi; Doi, Masao; Morita, Hiroshi

    2012-02-01

    We systematically studied versatile coarse-grained model (bead spring model) to describe filled polymer nano-composites for coarse-grained (Kremer-Grest model) molecular dynamics simulations. This model consists of long polymers, crosslink, and fillers. We used the hollow structure as the filler to describe rigid spherical fillers with small computing costs. Our filler model consists of surface particles of icosahedra fullerene structure C320 and a repulsive force from the center of the filler is applied to the surface particles in order to make a sphere and rigid. The filler's diameter is 12 times of beads of the polymers. As the first test of our model, we study temperature dependence of volumes of periodic boundary conditions under constant pressures through NPT constant Andersen algorithm. It is found that Glass transition temperature (Tg) decrease with increasing filler's volume fraction for the case of repulsive interaction between polymer and fillers and Tg weakly increase for attractive interaction.

  11. Investigation of dynamic glass transitions and structure transformations in cryovacuum condensates of ethanol

    International Nuclear Information System (INIS)

    Aldiyarov, A.; Aryutkina, M.; Drobyshev, A.; Kaikanov, M.; Kurnosov, V.

    2009-01-01

    An IR spectrometric investigation of the dynamic glass transition of ethanol from the rotationally disordered crystal to the orientationally disordered crystal is carried out. The samples considered are thin films formed from the gas phase at a substrate temperature of T=16 K. The measurements are performed using the experimental apparatus which has been described in detail in our recent work. The sample thickness was d=2 μm, and the typical rate of annealing is approximately 10 K/min. The results are compared with the phase diagram of solid ethanol proposed by M.A. Ramos et al. We observe good agreement between the temperature intervals of existence of the amorphous and crystalline states. The low-temperature amorphous phase (12-70 K) is described by the present authors as amorphous solid ethanol by analogy with the amorphous solid water

  12. Synthesis of styrene/isoprene/butadiene integrated rubber with wide glass transition temperature by reactive extrusion

    Science.gov (United States)

    Huang, Tianhua; Zheng, Anna; Zhan, Pengfei; Shi, Han; Li, Xiang; Guan, Yong; Wei, Dafu

    2018-05-01

    In this work, styrene/isoprene/butadiene integrated rubber (SIBR) was synthesized with n-butyllithium as the initiator and tetrahydrofuran as structure modifier in a co-rotating intermeshing twin-screw extruder. The content of diene in these terpolymers reached a surprising 70 wt% by feeding the monomers in two different sites of the twin-screw extruder. 1H-NMR, GPC and TEM results showed that the molecular structures of terpolymers changed with the variation of feeding site. Dynamic mechanical analysis of the vulcanized SIBR showed that the terpolymer had a wide glass transition region, which assured an excellent combination of high antiskid properties and low rolling resistance. Different from traditional solution polymerization, the present work provides a green approach to prepare the SIBR via bulk polymerization without solvent.

  13. Finite-size effects on the vortex-glass transition in thin YBa2Cu3O7-δ films

    International Nuclear Information System (INIS)

    Woeltgens, P.J.M.; Dekker, C.; Koch, R.H.; Hussey, B.W.; Gupta, A.

    1995-01-01

    Nonlinear current-voltage characteristics have been measured at high magnetic fields in YBa 2 Cu 3 O 7-δ films of a thickness t ranging from 3000 down to 16 A. Critical-scaling analyses of the data for the thinner films (t≤400 A) reveal deviations from the vortex-glass critical scaling appropriate for three-dimensional (3D) systems. This is argued to be a finite-size effect. At large current densities J, the vortices are probed at length scales smaller than the film thickness, i.e., 3D vortex-glass behavior is observed. At low J by contrast, the vortex excitations involve typical length scales exceeding the film thickness, resulting in 2D behavior. Further evidence for this picture is found directly from the 3D vortex-glass correlation length, which, upon approach of the glass transition temperature, appears to level off at the film thickness. The results indicate that a vortex-glass phase transition does occur at finite temperature in 3D systems, but not in 2D systems. In the latter an onset of 2D correlations occurs towards zero temperature. This is demonstrated in our thinnest film (16 A), which, in a magnetic field, displays a 2D vortex-glass correlation length which critically diverges at zero temperature

  14. Effect of molecular weight and glass transition on relaxation and release behaviour of poly(DL-lactic acid) tablets

    NARCIS (Netherlands)

    Steendam, R.; Van Steenbergen, M.J.; Hennink, W.E.; Frijlink, H.W.; Lerk, C.F.

    2001-01-01

    Different molecular weight grades of poly(DL-lactic acid) were applied as release controlling excipients in tablets for oral drug administration. The role of molecular weight and glass transition in the mechanism of water-induced volume expansion and drug release of PDLA tablets was investigated.

  15. Effect of aging time on the volumetric and enthalpic glass transition of a-PMMA upon heating

    Czech Academy of Sciences Publication Activity Database

    Říha, Pavel; Hadač, J.; Slobodian, P.; Sáha, P.; Rychwalski, R. W.; Kubát, J.

    2007-01-01

    Roč. 48, č. 25 (2007), s. 7356-7363 ISSN 0032-3861 R&D Projects: GA ČR GA103/05/0803 Institutional research plan: CEZ:AV0Z20600510 Keywords : a-PMMA * Glass transition * Aging Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.065, year: 2007

  16. 4-(ALPHA, ALPHA-DIMETHYLBENZYL)PHENYL METHACRYLATE .3. SYNTHESIS, TACTICITY AND GLASS-TRANSITION TEMPERATURES OF ITS POLYMERS

    NARCIS (Netherlands)

    VANEKENSTEIN, GORA; TAN, YY

    Depending on the kind of initiator, anionic Polymerization of 4-(alpha,alpha-dimethylbenzyl)phenyl methacrylate in toluene at -78-degrees-C led either to highly isotactic or predominantly syndiotactic polymers as determined by C-13 NMR spectro copy. The glass transition temperature difference

  17. Dilatancy induced ductile-brittle transition of shear band in metallic glasses

    Science.gov (United States)

    Zeng, F.; Jiang, M. Q.; Dai, L. H.

    2018-04-01

    Dilatancy-generated structural disordering, an inherent feature of metallic glasses (MGs), has been widely accepted as the physical mechanism for the primary origin and structural evolution of shear banding, as well as the resultant shear failure. However, it remains a great challenge to determine, to what degree of dilatation, a shear banding will evolve into a runaway shear failure. In this work, using in situ acoustic emission monitoring, we probe the dilatancy evolution at the different stages of individual shear band in MGs that underwent severely plastic deformation by the controlled cutting technology. A scaling law is revealed that the dilatancy in a shear band is linearly related to its evolution degree. A transition from ductile-to-brittle shear bands is observed, where the formers dominate stable serrated flow, and the latter lead to a runaway instability (catastrophe failure) of serrated flow. To uncover the underlying mechanics, we develop a theoretical model of shear-band evolution dynamics taking into account an atomic-scale deformation process. Our theoretical results agree with the experimental observations, and demonstrate that the atomic-scale volume expansion arises from an intrinsic shear-band evolution dynamics. Importantly, the onset of the ductile-brittle transition of shear banding is controlled by a critical dilatation.

  18. Hysteresis critical point of nitrogen in porous glass: occurrence of sample spanning transition in capillary condensation.

    Science.gov (United States)

    Morishige, Kunimitsu

    2009-06-02

    To examine the mechanisms for capillary condensation and for capillary evaporation in porous glass, we measured the hysteresis critical points and desorption scanning curves of nitrogen in four kinds of porous glasses with different pore sizes (Vycor, CPG75A, CPG120A, and CPG170A). The shapes of the hysteresis loop in the adsorption isotherm of nitrogen for the Vycor and the CPG75A changed with temperature, whereas those for the CPG120A and the CPG170A remained almost unchanged with temperature. The hysteresis critical points for the Vycor and the CPG75A fell on the common line observed previously for ordered mesoporous silicas. On the other hand, the hysteresis critical points for the CPG120A and the CPG170A deviated appreciably from the common line. This strongly suggests that capillary evaporation of nitrogen in the interconnected and disordered pores of both the Vycor and the CPG75A follows a cavitation process at least in the vicinity of their hysteresis critical temperatures in the same way as that in the cagelike pores of the ordered silicas, whereas the hysteresis critical points in the CPG120A and the CPG170A have origin different from that in the cagelike pores. The desorption scanning curves for the CPG75A indicated the nonindependence of the porous domains. On the other hand, for both the CPG120A and the CPG170A, we obtained the scanning curves that are expected from the independent domain theory. All these results suggest that sample spanning transitions in capillary condensation and evaporation take place inside the interconnected pores of both the CPG120A and the CPG170A.

  19. Glass transition behaviour of the quaternary ammonium type ionic liquid, {[DEME][I] + H2O} mixtures

    International Nuclear Information System (INIS)

    Imai, Yusuke; Abe, Hiroshi; Matsumoto, Hitoshi; Shimada, Osamu; Hanasaki, Tomonori; Yoshimura, Yukihiro

    2011-01-01

    By a simple DTA system, the glass transition temperatures of the quaternary ammonium type ionic liquid, {N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide, [DEME][I] + H 2 O} mixtures after quick pre-cooling were measured as a function of water concentration (x mol% H 2 O). Results were compared with the previous results of {[DEME][BF 4 ] + H 2 O} mixtures in which double glass transitions were observed in the water concentration region of (16.5 to 30.0) mol% H 2 O. Remarkably, we observed the double glass transition phenomenon in {[DEME][I] + H 2 O} mixtures too, but the two-T g s regions lie towards the water-rich side of (77.5 to 85.0) mol% H 2 O. These clearly reflect the difference in the anionic effect between BF 4 - and I - on the water structure. The end of the glass-formation region of {[DEME][I] + H 2 O} mixtures is around x = 95.0 mol% H 2 O, and this is comparable to that of {[DEME][BF 4 ] + H 2 O} mixtures (x = 96.0 mol% H 2 O).

  20. A New Vogel-Like Law: Ionic Conductivity, Dielectric Relaxation and Viscosity Near the Glass Transition

    National Research Council Canada - National Science Library

    Bendler, John

    2001-01-01

    A model, based on defect diffusion, is developed that describes temperature and pressure dependence of dielectric relaxation, ionic conductivity and viscosity of glass-forming liquids near the glass...

  1. Fundamental considerations in the effect of molecular weight on the glass transition of the gelatin/cosolute system.

    Science.gov (United States)

    Jiang, Bin; Kasapis, Stefan; Kontogiorgos, Vassilis

    2012-05-01

    Four molecular fractions of gelatin produced by alkaline hydrolysis of collagen were investigated in the presence of cosolute to record the mechanical properties of the glass transition in high-solid preparations. Dynamic oscillatory and stress relaxation moduli in shear were recorded from 40°C to temperatures as low as -60°C. The small-deformation behavior of these linear polymers was separated by the method of reduced variables into a basic function of time alone and a basic function of temperature alone. The former allowed the reduction of isothermal runs into a master curve covering 17 orders of magnitude in the time domain. The latter follows the passage from the rubbery plateau through the glass transition region to the glassy state seen in the variation of shift factor, a(T) , as a function of temperature. The mechanical glass transition temperature (T(g) ) is pinpointed at the operational threshold of the free volume theory and the predictions of the reaction rate theory. Additional insights into molecular dynamics are obtained via the coupling model of cooperativity, which introduces the concept of coupling constant or interaction strength of local segmental motions that govern structural relaxation at the vicinity of T(g) . The molecular weight of the four gelatin fractions appears to have a profound effect on the transition temperature or coupling constant of vitrified matrices, as does the protein chemistry in relation to that of amorphous synthetic polymers or gelling polysaccharides. © 2011 Wiley Periodicals, Inc.

  2. Substrate and surfactant effects on the glass-liquid transition of thin water films.

    Science.gov (United States)

    Souda, Ryutaro

    2006-09-07

    Temperature-programmed time-of-flight secondary ion mass spectrometry (TP-TOF-SIMS) and temperature-programmed desorption (TPD) have been used to perform a detailed investigation of the adsorption, desorption, and glass-liquid transition of water on the graphite and Ni(111) surfaces in the temperature range 13-200 K. Water wets the graphite surface at 100-120 K, and the hydrogen-bonded network is formed preferentially in the first monolayer to reduce the number of nonbonding hydrogens. The strongly chemisorbed water molecules at the Ni(111) surface do not form such a network and play a role in stabilizing the film morphology up to 160 K, where dewetting occurs abruptly irrespective of the film thickness. The surface structure of the water film formed on graphite is fluctuated considerably, resulting in deweting at 150-160 K depending on the film thickness. The dewetted patches of graphite are molecularly clean, whereas the chemisorbed water remains on the Ni(111) surface even after evaporation of the film. The abrupt drop in the desorption rate of water molecules at 160 K, which has been attributed to crystallization in the previous TPD studies, is found to disappear completely when a monolayer of methanol is present on the surface. This is because the morphology of supercooled liquid water is changed by the surface tension, and it is quenched by termination of the free OH groups on the surface. The surfactant methanol desorbs above 160 K since the hydrogen bonds of the water molecules are reconstructed. The drastic change in the properties of supercooled liquid water at 160 K should be ascribed to the liquid-liquid phase transition.

  3. Micro-Raman spectroscopy studies of the phase separation mechanisms of transition-metal phosphate glasses

    International Nuclear Information System (INIS)

    Mazali, Italo Odone; Alves, Oswaldo Luiz; Gimenez, Iara de Fatima

    2009-01-01

    Glass-ceramics are prepared by controlled separation of crystal phases in glasses, leading to uniform and dense grain structures. On the other hand, chemical leaching of soluble crystal phases yields porous glass-ceramics with important applications. Here, glass/ceramic interfaces of niobo-, vanado- and titano-phosphate glasses were studied by micro-Raman spectroscopy, whose spatial resolution revealed the multiphase structures. Phase-separation mechanisms were also determined by this technique, revealing that interface composition remained unchanged as the crystallization front advanced for niobo- and vanadophosphate glasses (interface-controlled crystallization). For titanophosphate glasses, phase composition changed continuously with time up to the equilibrium composition, indicating a spinodal-type phase separation. (author)

  4. Optical transitions of Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 glass.

    Science.gov (United States)

    Shen, Xiang; Nie, Qiuhua; Xu, Tiefeng; Gao, Yuan

    2005-10-01

    Optical absorption and emission properties of the Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 (TWB) glass has been investigated. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. The broad 1.5 microm fluorescence was observed under 970 nm excitation, and its full width at half maximum (FWHM) is 77 nm. The emission cross-section is calculated using the McCumber theory, and the peak emission cross-section is 1.03 x 10(-21) cm2 at 1.531 microm. This value is much larger than those of the silicate and phosphate glasses. Efficient green and weak red upconversion luminescence from Er3+ centers in the glass sample was observed at room temperature, and the upconversion excitation processes have been analyzed.

  5. Using Combined Computational Techniques to Predict the Glass Transition Temperatures of Aromatic Polybenzoxazines

    Science.gov (United States)

    Mhlanga, Phumzile; Wan Hassan, Wan Aminah; Hamerton, Ian; Howlin, Brendan J.

    2013-01-01

    The Molecular Operating Environment software (MOE) is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc.) are obtained and quantitative structure property relationships (QSPR) models are formulated. Three QSPR models (formulated using up to 5 descriptors) are first used to make predictions for the initiator data set (n = 9) and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.63–1.86 K of the entire dataset). The water accessible surface area is found to be the most important descriptor in the prediction of Tg. Molecular modelling simulations of the benzoxazine polymer (minus initiator) carried out at the same time using the Materials Studio software suite provide an independent prediction of Tg. Predicted Tg values from molecular modelling fall in the middle of the range of the experimentally determined Tg values, indicating that the structure of the network is influenced by the nature of the initiator used. Hence both techniques can provide predictions of glass transition temperatures and provide complementary data for polymer design. PMID:23326419

  6. Molecular relaxation behavior and isothermal crystallization above glass transition temperature of amorphous hesperetin.

    Science.gov (United States)

    Shete, Ganesh; Khomane, Kailas S; Bansal, Arvind Kumar

    2014-01-01

    The purpose of this paper was to investigate the relaxation behavior of amorphous hesperetin (HRN), using dielectric spectroscopy, and assessment of its crystallization kinetics above glass transition temperature (Tg ). Amorphous HRN exhibited both local (β-) and global (α-) relaxations. β-Relaxation was observed below Tg , whereas α-relaxation prominently emerged above Tg . β-Relaxation was found to be of Johari-Goldstein type and was correlated with α-process by coupling model. Secondly, isothermal crystallization experiments were performed at 363 K (Tg + 16.5 K), 373 K (Tg + 26.5 K), and 383 K (Tg + 36.5 K). The kinetics of crystallization, obtained from the normalized dielectric strength, was modeled using the Avrami model. Havriliak-Negami (HN) shape parameters, αHN and αHN .βHN , were analyzed during the course of crystallization to understand the dynamics of amorphous phase during the emergence of crystallites. HN shape parameters indicated that long range (α-like) were motions affected to a greater extent than short range (β-like) motions during isothermal crystallization studies at all temperature conditions. The variable behavior of α-like motions at different isothermal crystallization temperatures was attributed to evolving crystallites with time and increase in electrical conductivity with temperature. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

  7. A molecular dynamics approach for predicting the glass transition temperature and plasticization effect in amorphous pharmaceuticals.

    Science.gov (United States)

    Gupta, Jasmine; Nunes, Cletus; Jonnalagadda, Sriramakamal

    2013-11-04

    The objectives of this study were as follows: (i) To develop an in silico technique, based on molecular dynamics (MD) simulations, to predict glass transition temperatures (Tg) of amorphous pharmaceuticals. (ii) To computationally study the effect of plasticizer on Tg. (iii) To investigate the intermolecular interactions using radial distribution function (RDF). Amorphous sucrose and water were selected as the model compound and plasticizer, respectively. MD simulations were performed using COMPASS force field and isothermal-isobaric ensembles. The specific volumes of amorphous cells were computed in the temperature range of 440-265 K. The characteristic "kink" observed in volume-temperature curves, in conjunction with regression analysis, defined the Tg. The MD computed Tg values were 367 K, 352 K and 343 K for amorphous sucrose containing 0%, 3% and 5% w/w water, respectively. The MD technique thus effectively simulated the plasticization effect of water; and the corresponding Tg values were in reasonable agreement with theoretical models and literature reports. The RDF measurements revealed strong hydrogen bond interactions between sucrose hydroxyl oxygens and water oxygen. Steric effects led to weak interactions between sucrose acetal oxygens and water oxygen. MD is thus a powerful predictive tool for probing temperature and water effects on the stability of amorphous systems during drug development.

  8. Structure-to-glass transition temperature relationships in high temperature stable condensation polyimides

    Science.gov (United States)

    Alston, W. B.; Gratz, R. F.

    1985-01-01

    The presence of a hexafluoroisopropylidene (6F) connecting group in aryl dianhydrides used to prepare aromatic condensation polyimides provides high glass transition temperature (T sub g) polyimides with excellent thermo-oxidative stability. The purpose of this study was to determine if a trifluorophenyl-ethylidene (3F) connecting group would have a similar effect on the T sub g of aromatic condensation polyimides. A new dianhydride containing the 3F connecting group was synthesized. This dianhydride and an aromatic diamine also containing the 3F connecting group were used together and in various combinations with known diamines or known dianhydrides, respectively, to prepare new 3F containing condensation polyimides. Known polyimides, including some with the 6F connecting linkage, were also prepared for comparison purposes. The new 3F containing polymers and the comparison polymers were prepared by condensation polymerization via the traditional amic-acid polymerization method in N,N-dimethylacetamide solvent. The solutions were characterized by determining their inherent viscosities and then were thermally converted into polyimide films under nitrogen atmosphere at 300 to 500 C, usually 350 C. The T sub g's of the films and resin discs were then determined by thermomechanical analysis and were correlated as a function of the final processing temperatures of the films and resin discs. The results showed that similarities existed in the T sub g's depending on the nature of the connecting linkage in the monomers used to prepare the condensation polyimides.

  9. Effect of salt on the glass transition of condensed tapioca starch systems.

    Science.gov (United States)

    Chuang, Lillian; Panyoyai, Naksit; Shanks, Robert A; Kasapis, Stefan

    2017-08-15

    This work examines the effect of including hydrated NaCl and CaCl 2 (up to 6% w/w) on the physicochemical properties of condensed tapioca starch. Samples were prepared by hot pressing at 120°C to produce condensed systems that covered a range of moisture contents from 7.34% w/w (23% relative humidity) to 19.52% w/w (75% relative humidity). Tensile storage modulus and heat flow measurements were taken using DMA and MDSC, which were accompanied by FTIR, WAXD and ESEM. Increasing the salt level enhances the mechanical strength of starch in the glassy state and shifts the glass transition temperature to a higher value. Antiplasticising effects of NaCl and CaCl 2 on the non-phosphorylated tapioca starch are indistinguishable from each other. Observations are complemented by intensification of absorbance peaks in FTIR spectra and a systematic change in shape and intensity of diffraction patterns with increasing addition of salt consistent with interactions between added ions and macromolecule. Copyright © 2017. Published by Elsevier Ltd.

  10. CO2 Induced Foaming Behavior of Polystyrene near the Glass Transition

    Directory of Open Access Journals (Sweden)

    Salah Al-Enezi

    2017-01-01

    Full Text Available This paper examines the effect of high-pressure carbon dioxide on the foaming process in polystyrene near the glass transition temperature and the foaming was studied using cylindrical high-pressure view cell with two optical windows. This technique has potential applications in the shape foaming of polymers at lower temperatures, dye impregnation, and the foaming of polystyrene. Three sets of experiments were carried out at operating temperatures of 50, 70, and 100°C, each over a range of pressures from 24 to 120 bar. Foaming was not observed when the polymer was initially at conditions below Tg but was observed above Tg. The nucleation appeared to occur randomly leading to subsequent bubble growth from these sites, with maximum radius of 0.02–0.83 mm. Three models were applied on the foaming experimental data. Variable diffusivity and viscosity model (Model C was applied to assess the experimental data with the WLF equation. The model shows very good agreement by using realistic parameter values. The expansion occurs by diffusion of a dissolved gas from the supersaturated polymer envelope into the bubble.

  11. Glass transition and degree of conversion of a light-cured orthodontic composite

    Directory of Open Access Journals (Sweden)

    Michela M. D. S. Sostena

    2009-12-01

    Full Text Available OBJECTIVE: This study evaluated the glass transition temperature (Tg and degree of conversion (DC of a light-cured (Fill Magic versus a chemically cured (Concise orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s. RESULTS: Fill Magic presented lower Tg than Concise (35-84ºC versus 135ºC, but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm² is necessary to reach adequate conversion level and obtain satisfactory adhesion.

  12. Impact of the glass transition on exciton dynamics in polymer thin films

    Science.gov (United States)

    Ehrenreich, Philipp; Proepper, Daniel; Graf, Alexander; Jores, Stefan; Boris, Alexander V.; Schmidt-Mende, Lukas

    2017-11-01

    In the development of organic electronics, unlimited design possibilities of conjugated polymers offer a wide variety of mechanical and electronic properties. Thereby, it is crucially important to reveal universal physical characteristics that allow efficient and forward developments of new chemical compounds. In particular for organic solar cells, a deeper understanding of exciton dynamics in polymer films can help to improve the charge generation process further. For this purpose, poly(3-hexylthiophene) (P3HT) is commonly used as a model system, although exciton decay kinetics have found different interpretations. Using temperature-dependent time-resolved photoluminescence spectroscopy in combination with low-temperature spectroscopic ellipsometry, we can show that P3HT is indeed a model system in which excitons follow a simple diffusion/hopping model. Based on our results we can exclude the relevance of hot-exciton emission as well as a dynamic torsional relaxation upon photoexcitation on a ps time scale. Instead, we depict the glass transition temperature of polymers to strongly affect exciton dynamics.

  13. Role of fluctuations in the phase transitions of coupled plaquette spin models of glasses

    Directory of Open Access Journals (Sweden)

    Giulio Biroli, Charlotte Rulquin, Gilles Tarjus, Marco Tarzia

    2016-10-01

    Full Text Available We study the role of fluctuations on the thermodynamic glassy properties of plaquette spin models, more specifically on the transition involving an overlap order parameter in the presence of an attractive coupling between different replicas of the system. We consider both short-range fluctuations associated with the local environment on Bethe lattices and long-range fluctuations that distinguish Euclidean from Bethe lattices with the same local environment. We find that the phase diagram in the temperature-coupling plane is very sensitive to the former but, at least for the $3$-dimensional (square pyramid model, appears qualitatively or semi-quantitatively unchanged by the latter. This surprising result suggests that the mean-field theory of glasses provides a reasonable account of the glassy thermodynamics of models otherwise described in terms of the kinetically constrained motion of localized defects and taken as a paradigm for the theory of dynamic facilitation. We discuss the possible implications for the dynamical behavior.

  14. Low-Cost, High Glass-Transition Temperature, Thermosetting Polyimide Developed

    Science.gov (United States)

    Chuang, Kathy C.

    1999-01-01

    PMR-15 polyimide, developed in the mid-1970's at the NASA Lewis Research Center, is recognized as a state-of-the-art high-temperature resin for composite applications in the temperature range of 500 to 550 F (260 to 288 C). PMR-15 offers easy processing and good property retention at a reasonable cost. For these reasons, it is widely used in both military and commercial aircraft engine components. Traditionally, polyimide composites have been designed for long-term use at 500 to 600 F over thousands of hours. However, new applications in reusable launch vehicles (RLV's) require lightweight materials that can perform for short times (tens of hours) at temperatures between 800 and 1000 F (425 and 538 C). Current efforts at Lewis are focused on raising the use temperature of polyimide composites by increasing the glass-transition temperature of the matrix resins. Achieving this dramatic increase in the upper use temperature without sacrificing polymer and composite processability is a major technical challenge.

  15. Tuning Glass Transition in Polymer Nanocomposites with Functionalized Cellulose Nanocrystals through Nanoconfinement.

    Science.gov (United States)

    Qin, Xin; Xia, Wenjie; Sinko, Robert; Keten, Sinan

    2015-10-14

    Cellulose nanocrystals (CNCs) exhibit impressive interfacial and mechanical properties that make them promising candidates to be used as fillers within nanocomposites. While glass-transition temperature (Tg) is a common metric for describing thermomechanical properties, its prediction is extremely difficult as it depends on filler surface chemistry, volume fraction, and size. Here, taking CNC-reinforced poly(methyl-methacrylate) (PMMA) nanocomposites as a relevant model system, we present a multiscale analysis that combines atomistic molecular dynamics (MD) surface energy calculations with coarse-grained (CG) simulations of relaxation dynamics near filler-polymer interfaces to predict composite properties. We discover that increasing the volume fraction of CNCs results in nanoconfinement effects that lead to an appreciation of the composite Tg provided that strong interfacial interactions are achieved, as in the case of TEMPO-mediated surface modifications that promote hydrogen bonding. The upper and lower bounds of shifts in Tg are predicted by fully accounting for nanoconfinement and interfacial properties, providing new insight into tuning these aspects in nanocomposite design. Our multiscale, materials-by-design framework is validated by recent experiments and breaks new ground in predicting, without any empirical parameters, key structure-property relationships for nanocomposites.

  16. The effective complex permittivity stability in filled polymer nanocomposites studied above the glass transition temperature

    Directory of Open Access Journals (Sweden)

    Elhaouzi F.

    2018-01-01

    Full Text Available The temperature effecton the dielectric response of nanocomposite at low frequencies range is reported. The investigated samples are formed by a semi-crystalline ethylene-co-butyl acrylate (EBA polymer filled with three concentrations of the dispersed conducting carbon black (CB nanoparticles. The temperature dependence of the complex permittivity has been analyzedabove the glass transition temperature of the neat polymer matrix Tg=-75°C. For all CB concentrations, the dielectric spectra follow a same trend in frequency range 100-106Hz. More interestingly, the stability of the effective complex permittivity ɛ=ɛ' -iɛ'' with the temperature range of 10-70°C is explored. While the imaginary part of the complex permittivity ɛ'' exhibits a slight decreasewith temperature, the real part ɛ' shows a significant reduction especially for high loading samples. The observed dielectric response may be related to the breakup of the three-dimensional structurenetwork formed by the aggregation of CB particles causing change at the interfaceEBA-CB.This interface is estimated bythe volume fraction of constrained polymer chain according to loss tangent data of dynamic mechanical analysis.

  17. Gradient of molecular dynamics at the glass transition of PETg-Montmorillonite nanocomposites

    Science.gov (United States)

    Couderc, H.; Saiter, A.; Grenet, J.; Saiter, J. M.

    2011-07-01

    Temperature Modulated Differential Scanning Calorimetry (TMDSC) is used to estimate Cooperative Rearranging Region (CRR) average sizes for polymer/clay nanocomposites, obtained by mixing polyethylene 1,4-cyclohexylenedimethylene terephthalate glycol (PETg) filled and organically modified nanoclay (C15A) following a master-batch process. Two different basal distances are obtained. It is shown that the greater the basal distance and the nanofiller content, the lower the heat capacity step at the glass transition temperature Δ Cp( Tg), and the lower the CRR volume. It is also shown that the evolution of the CRR volume is consistent with the evolution of the fragility index obtained by DSC and Broadband Dielectric Spectroscopy (BDS) when the nanofiller content changes. The fragility index and the CRR size decreases can be correlated to nanofiller presence, hindering the molecular movements. From the Vollenberg and Heikens [34] approach, this behaviour can also be interpreted through the existence of an interfacial bilayer. This interfacial bilayer is composed by a zone, which is next to the nanofiller, with a density higher than the matrix one, followed by a more expanded zone with a density lower than the matrix one.

  18. Using combined computational techniques to predict the glass transition temperatures of aromatic polybenzoxazines.

    Directory of Open Access Journals (Sweden)

    Phumzile Mhlanga

    Full Text Available The Molecular Operating Environment software (MOE is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc. are obtained and quantitative structure property relationships (QSPR models are formulated. Three QSPR models (formulated using up to 5 descriptors are first used to make predictions for the initiator data set (n = 9 and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.63-1.86 K of the entire dataset. The water accessible surface area is found to be the most important descriptor in the prediction of T(g. Molecular modelling simulations of the benzoxazine polymer (minus initiator carried out at the same time using the Materials Studio software suite provide an independent prediction of T(g. Predicted T(g values from molecular modelling fall in the middle of the range of the experimentally determined T(g values, indicating that the structure of the network is influenced by the nature of the initiator used. Hence both techniques can provide predictions of glass transition temperatures and provide complementary data for polymer design.

  19. Rationalization of an unusual solvent-induced inversion of enantiomeric excess in organocatalytic selenylation of aldehydes.

    Science.gov (United States)

    Burés, Jordi; Dingwall, Paul; Armstrong, Alan; Blackmond, Donna G

    2014-08-11

    An unusual solvent-induced inversion of the sense of enantioselectivity observed in the α-selenylation of aldehydes catalyzed by a diphenylprolinol silyl ether catalyst is correlated to the presence of intermediates formed subsequent to the highly selective C-Se bond-forming step in the catalytic cycle. This work provides support for a mechanistic concept for enamine catalysis and includes a general role for "downstream intermediates" in selectivity outcomes in organocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effect of 3d-transition metal doping on the shielding behavior of barium borate glasses: a spectroscopic study.

    Science.gov (United States)

    ElBatal, H A; Abdelghany, A M; Ghoneim, N A; ElBatal, F H

    2014-12-10

    UV-visible and FT infrared spectra were measured for prepared samples before and after gamma irradiation. Base undoped barium borate glass of the basic composition (BaO 40%-B2O3 60mol.%) reveals strong charge transfer UV absorption bands which are related to unavoidable trace iron impurities (Fe(3+)) within the chemical raw materials. 3d transition metal (TM)-doped glasses exhibit extra characteristic absorption bands due to each TM in its specific valence or coordinate state. The optical spectra show that TM ions favor generally the presence in the high valence or tetrahedral coordination state in barium borate host glass. Infrared absorption bands of all prepared glasses reveal the appearance of both triangular BO3 units and tetrahedral BO4 units within their characteristic vibrational modes and the TM-ions cause minor effects because of the low doping level introduced (0.2%). Gamma irradiation of the undoped barium borate glass increases the intensity of the UV absorption together with the generation of an induced broad visible band at about 580nm. These changes are correlated with suggested photochemical reactions of trace iron impurities together with the generation of positive hole center (BHC or OHC) within the visible region through generated electrons and positive holes during the irradiation process. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    Films of high-molecular-weight amorphous polystyrene (PS, M-w = 225 kg/mol, M-w/M-n = 3, T-g-bulk = 97degreesC, where T-g-bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M-w = 87 kg/mol, M-w/M-n = 2, Tg-bulk = 109degreesC) were brought into contact...

  2. Healing of interfaces of high and ultra-high-molecular- weight polystyrene below the bulk glass transition temperature

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    into contact to themselves below the glass transition temperature T-g of the bulk Tg-bulk, in a lap-shear joint geometry, at a constant healing temperature T-h for a healing time t(h) of 10 min to 24 h. The lap-shear strength sigma of the symmetric HMWPS-HMWPS and UHMWPS-URMWPS interfaces has been measured...

  3. Effect of water content on the glass transition temperature of mixtures of sugars, polymers, and penetrating cryoprotectants in physiological buffer.

    Science.gov (United States)

    Drake, Andrew C; Lee, Youngjoo; Burgess, Emma M; Karlsson, Jens O M; Eroglu, Ali; Higgins, Adam Z

    2018-01-01

    Long-term storage of viable mammalian cells is important for applications ranging from in vitro fertilization to cell therapy. Cryopreservation is currently the most common approach, but storage in liquid nitrogen is relatively costly and the requirement for low temperatures during shipping is inconvenient. Desiccation is an alternative strategy with the potential to enable viable cell preservation at more convenient storage temperatures without the need for liquid nitrogen. To achieve stability during storage in the dried state it is necessary to remove enough water that the remaining matrix forms a non-crystalline glassy solid. Thus, the glass transition temperature is a key parameter for design of cell desiccation procedures. In this study, we have investigated the effects of moisture content on the glass transition temperature (Tg) of mixtures of sugars (trehalose or raffinose), polymers (polyvinylpyrrolidone or Ficoll), penetrating cryoprotectants (ethylene glycol, propylene glycol, or dimethyl sulfoxide), and phosphate buffered saline (PBS) solutes. Aqueous solutions were dried to different moisture contents by equilibration with saturated salt solutions, or by baking at 95°C. The glass transition temperatures of the dehydrated samples were then measured by differential scanning calorimetry. As expected, Tg increased with decreasing moisture content. For example, in a desiccation medium containing 0.1 M trehalose in PBS, Tg ranged from about 360 K for a completely dry sample to about 220 K at a water mass fraction of 0.4. Addition of polymers to the solutions increased Tg, while addition of penetrating cryoprotectants decreased Tg. Our results provide insight into the relationship between relative humidity, moisture content and glass transition temperature for cell desiccation solutions containing sugars, polymers and penetrating cryoprotectants.

  4. Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting Polymers (Briefing Charts)

    Science.gov (United States)

    2015-05-20

    TEMPERATURES IN HIGH-TEMPERATURE THERMOSETTING POLYMERS 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...temperature thermosetting polymer via dynamic mechanical analysis alone. These difficulties result from the residual cure of samples heated beyond their...98) Prescribed by ANSI Std. 239.18 Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting

  5. Temperature Dependence of Arn+ Cluster Backscattering from Polymer Surfaces: a New Method to Determine the Surface Glass Transition Temperature.

    Science.gov (United States)

    Poleunis, Claude; Cristaudo, Vanina; Delcorte, Arnaud

    2018-01-01

    In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to study the intensity variations of the backscattered Ar n + clusters as a function of temperature for several amorphous polymer surfaces (polyolefins, polystyrene, and polymethyl methacrylate). For all these investigated polymers, our results show a transition of the ratio Ar 2 + /(Ar 2 + + Ar 3 + ) when the temperature is scanned from -120 °C to +125 °C (the exact limits depend on the studied polymer). This transition generally spans over a few tens of degrees and the temperature of the inflection point of each curve is always lower than the bulk glass transition temperature (T g ) reported for the considered polymer. Due to the surface sensitivity of the cluster backscattering process (several nanometers), the presented analysis could provide a new method to specifically evaluate a surface transition temperature of polymers, with the same lateral resolution as the gas cluster beam. Graphical abstract ᅟ.

  6. Characterisation of moisture uptake effects on the glass transitional behaviour of an amorphous drug using modulated temperature DSC.

    Science.gov (United States)

    Royall, P G; Craig, D Q; Doherty, C

    1999-12-01

    The purpose of this study was to investigate the depression of the glass transition temperature, T(g), of the protease inhibitor saquinavir in the first heating scan as a function of the quantity of sorbed water by the application of modulated temperature differential scanning calorimetry (MTDSC). Samples of amorphous saquinavir were pretreated under various humidity conditions and the quantity of sorbed water measured by thermogravimetric analysis. MTDSC runs were performed using hermetically and non-hermetically sealed pans in order to determine the glass transition temperature. MTDSC allowed the separation of the glass transition from the enthalpic relaxation, thereby allowing clear visualisation of T(g) for amorphous saquinavir in the first heating scan. The plasticizing effects of water were assessed, with the depression in T(g) related to the mole fraction of water sorbed via the Gordon-Taylor relationship. An expression has been derived which allows estimation of the water content which lowers the T(g) to the storage temperature, thereby considerably increasing the risk of recrystallisation. It is argued that this model may aid prediction of the optimal storage conditions for amorphous drugs.

  7. How carbon nanotubes affect the cure kinetics and glass transition temperature of their epoxy composites? – A review

    Directory of Open Access Journals (Sweden)

    2009-09-01

    Full Text Available Motivated by the widespread and contradictory results regarding the glass transition temperature of carbon nanotube (CNT/epoxy composites, we reviewed and analyzed the literature results dealing with the effect of unmodified multiwall carbon nanotubes (MWNT on the cure behaviour of an epoxy resin (as a possible source of this discrepancy. The aim of this work was to clarify the effective role of unmodified multiwall carbon nanotubes on the cure kinetics and glass transition temperature (Tg of their epoxy composites. It was found that various authors reported an acceleration effect of CNT. The cure reaction was promoted in its early stage which may be due to the catalyst particles present in the CNT raw material. While SWNT may lead to a decrease of Tg due to their bundling tendency, results reported for MWNT suggested an increased or unchanged Tg of the composites. The present status of the literature does not allow to isolate the effect of MWNT on the Tg due to the lack of a study providing essential information such as CNT purity, glass transition temperature along with the corresponding cure degree.

  8. Low-density to high-density transition in Ce{sub 75}Al{sub 23}Si{sub 2} metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Q S; Lou, H B; Gong, Y; Wang, X D; Jiang, J Z [International Center for New-Structured Materials, Zhejiang University, Hangzhou 310027 (China); Fang, Y Z; Wu, F M [College of Mathematics, Physics and Information Engineering, Zhejiang Normal University, Jinhua 321004, Zhejiang (China); Yang, K; Li, A G; Yan, S; Yu, X H [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201203 (China); Lathe, C, E-mail: qiaoshizeng@gmail.co, E-mail: jiangjz@zju.edu.c [HASYLAB am DESY, Notkestrasse 85, Hamburg D-22603 (Germany)

    2010-09-22

    Using in situ high-pressure x-ray diffraction (XRD), we observed a pressure-induced polyamorphic transition from the low-density amorphous (LDA) state to the high-density amorphous (HDA) state in Ce{sub 75}Al{sub 23}Si{sub 2} metallic glass at about 2 GPa and 300 K. The thermal stabilities of both LDA and HDA metallic glasses were further investigated using in situ high-temperature and high-pressure XRD, which revealed different pressure dependences of the onset crystallization temperature (T{sub x}) between them with a turning point at about 2 GPa. Compared with Ce{sub 75}Al{sub 25} metallic glass, minor Si doping shifts the onset polyamorphic transition pressure from 1.5 to 2 GPa and obviously stabilizes both LDA and HDA metallic glasses with higher T{sub x} and changes their slopes dT{sub x}/dP. The results obtained in this work reveal another polyamorphous metallic glass system by minor alloying (e.g. Si), which could modify the transition pressure and also properties of LDA and HDA metallic glasses. The minor alloying effect reported here is valuable for the development of more polyamorphous metallic glasses, even multicomponent bulk metallic glasses with modified properties, which will trigger more investigations in this field and improve our understanding of polyamorphism and metallic glasses.

  9. Prediction of the Formulation Dependence of the Glass Transition Temperature for Amine-Epoxy Copolymers Using a Quantitative Structure-Property Relationship Based on the AM1 Method

    National Research Council Canada - National Science Library

    Morrill, Jason

    2004-01-01

    A designer Quantitative Structure-Property Relationsbip (QSPR) based upon molecular properties calculated using the AM1 semi-empirical quantum mechanical metbod was developed to predict the glass transition temperature (Tg...

  10. Effect of sugar addition on glass transition temperatures of cassava starch with low to intermediate moisture contents.

    Science.gov (United States)

    Figueroa, Yetzury; Guevara, Marvilan; Pérez, Adriana; Cova, Aura; Sandoval, Aleida J; Müller, Alejandro J

    2016-08-01

    This work studies how sucrose (S) addition modifies the thermal properties of cassava starch (CS). Neat CS and CS-S blends with 4, 6 and 8% sugar contents (CS-S-4%, CS-S-6% and CS-S-8%) were prepared and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), in a wide range of moisture levels (2-20%). In equilibrated samples with moisture contents lower than 10%, twoendothermic steps were observed during first DSC heating scans and two corresponding relaxation maxima in tan δ were detected by DMTA. The first transition, detected at around 45-55°C by both DSC and DMTA, is frequently found in starchy foods, while the second observed at higher temperatures is associated to the glass transition temperature of the blends. At higher moisture contents, only one thermal transition was observed. Samples analyzed immediately after cooling from the melt (i.e., after erasing their thermal history), exhibited a single glass transition temperature, regardless of their moisture content. Addition of sugar promotes water plasticization of CS only at high moisture contents. In the low moisture content range, anti-plasticization was observed for both neat and sugar-added CS samples. Addition of sugar decreases the moisture content needed to achieve the maximum value of the glass transition temperature before plasticization starts. The results of this work may be valuable for the study of texture establishment in low moisture content extruded food products. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

    Directory of Open Access Journals (Sweden)

    W.-S. W. DeRieux

    2018-05-01

    Full Text Available Secondary organic aerosol (SOA accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH, and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg. We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds with molar mass less than 450 g mol−1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol−1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg∕T as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7 as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon–Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ, and the Gordon–Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS, resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI and atmospheric pressure photoionization (APPI. Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and

  12. Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

    Science.gov (United States)

    Wong DeRieux, Wing-Sy; Li, Ying; Lin, Peng; Laskin, Julia; Laskin, Alexander; Bertram, Allan K.; Nizkorodov, Sergey A.; Shiraiwa, Manabu

    2018-05-01

    Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg). We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol-1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ˜ 1100 g mol-1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg/T) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ˜ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon-Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ), and the Gordon-Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2-5 orders

  13. Thermal properties and optical transition probabilities of Tm3 + doped TeO2-WO3 glass.

    Science.gov (United States)

    Cenk, S; Demirata, B; Oveçoglu, M L; Ozen, G

    2001-10-01

    Glasses with the composition of (1 - x)TeO2 + (x)WO3, where x = 0.15, 0.25 and 0.3 were prepared and, their thermal and absorption measurements were carried out. Differential thermal analysis (DTA) curves taken in the 23-600 degrees C temperature range with a heating rate of 10 degrees C/min reveal a change in the value of the glass transition temperature, Tg, while crystallization was not observed for the glasses containing a WO3 content of more than 15 mol%. All the glasses were found to be moisture-resistant. The absorption bands corresponding to the absorption of the 1G4, 3F2, 3F3 and 3F4, 3H5 and 3H4 levels from the 3H6 ground level of the Tm3+ ion were observed in the optical absorption spectra. Integrated absorption cross-sections of each band except that of 3H5 level was found to vary with the glass composition. Judd-Ofelt analysis was carried out for the samples doped with 1.0 mol% Tm2O3. The omega2 parameter shows the strongest dependence on the host composition and it increases with the increasing WO3 amount. The value of omega4 increases rather slowly while the value of omega6 is practically independent of the composition. The strong dependence of the parameter omega2 indicates that this parameter is related to the structural change and the symmetry of the local environment of the Tm3+ ions in this glass.

  14. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.; Wang, W. H.; Bai, H. Y., E-mail: hybai@aphy.iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, B. A. [Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon (Hong Kong)

    2016-02-07

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

  15. Transitioning glass-ceramic scintillators for diagnostic x-ray imaging from the laboratory to commercial scale

    Science.gov (United States)

    Beckert, M. Brooke; Gallego, Sabrina; Elder, Eric; Nadler, Jason

    2016-10-01

    This study sought to mitigate risk in transitioning newly developed glass-ceramic scintillator technology from a laboratory concept to commercial product by identifying the most significant hurdles to increased scale. These included selection of cost effective raw material sources, investigation of process parameters with the most significant impact on performance, and synthesis steps that could see the greatest benefit from participation of an industry partner that specializes in glass or optical component manufacturing. Efforts focused on enhancing the performance of glass-ceramic nanocomposite scintillators developed specifically for medical imaging via composition and process modifications that ensured efficient capture of incident X-ray energy and emission of scintillation light. The use of cost effective raw materials and existing manufacturing methods demonstrated proof-of-concept for economical viable alternatives to existing benchmark materials, as well as possible disruptive applications afforded by novel geometries and comparatively lower cost per volume. The authors now seek the expertise of industry to effectively navigate the transition from laboratory demonstrations to pilot scale production and testing to evince the industry of the viability and usefulness of composite-based scintillators.

  16. Glass transition behavior of octyl β-D-glucoside and octyl β-D-thioglucoside/water binary mixtures.

    Science.gov (United States)

    Ogawa, Shigesaburo; Asakura, Kouichi; Osanai, Shuichi

    2010-11-22

    The lyotropic behavior and glass-forming properties of octyl β-D-glucoside (C8Glu) and octyl β-D-thioglucoside (C8SGlu)/water binary mixtures were evaluated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The results clearly indicate that the mixture forms a glass in the supercooling state of liquid crystalline phases such as cubic, lamellar, and smectic. The glass transition temperature (T(g)) of the mixture was strongly dependent on solute concentration, with a higher concentration correlating with a higher T(g). The experimental T(g) was consistent with the predicted value calculated using the Couchman-Karasz equation in both the C8Glu and C8SGlu/water mixtures. The change of heat capacity at T(g) showed the two bending points under variation of concentrations. And the highest temperature of phase transition from lamellar to isotropic solution was observed at around 50% molar concentration. It was expected that non-percolated state of water existed in extremely higher concentration ranges. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Evolution of short range order in Ar: Liquid to glass and solid transitions-A computational study

    Science.gov (United States)

    Shor, Stanislav; Yahel, Eyal; Makov, Guy

    2018-04-01

    The evolution of the short range order (SRO) as a function of temperature in a Lennard-Jones model liquid with Ar parameters was determined and juxtaposed with thermodynamic and kinetic properties obtained as the liquid was cooled (heated) and transformed between crystalline solid or glassy states and an undercooled liquid. The Lennard-Jones system was studied by non-equilibrium molecular dynamics simulations of large supercells (approximately 20000 atoms) rapidly cooled or heated at selected quenching rates and at constant pressure. The liquid to solid transition was identified by discontinuities in the atomic volume and molar enthalpy; the glass transition temperature range was identified from the temperature dependence of the self-diffusion. The SRO was studied within the quasi-crystalline model (QCM) framework and compared with the Steinhardt bond order parameters. Within the QCM it was found that the SRO evolves from a bcc-like order in the liquid through a bct-like short range order (c/a=1.2) in the supercooled liquid which persists into the glass and finally to a fcc-like ordering in the crystalline solid. The variation of the SRO that results from the QCM compares well with that obtained with Steinhardt's bond order parameters. The hypothesis of icosahedral order in liquids and glasses is not supported by our results.

  18. Quantification of Protein Hydration, Glass Transitions, and Structural Relaxations of Aqueous Protein and Carbohydrate-Protein Systems.

    Science.gov (United States)

    Roos, Yrjö H; Potes, Naritchaya

    2015-06-11

    Water distribution and miscibility of carbohydrate and protein components in biological materials and their structural contributions in concentrated solids are poorly understood. In the present study, structural relaxations and a glass transition of protein hydration water and antiplasticization of the hydration water at low temperatures were measured using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) for bovine whey protein (BWP), aqueous glucose-fructose (GF), and their mixture. Thermal transitions of α-lactalbumin and β-lactoglobulin components of BWP included water-content-dependent endothermic but reversible dehydration and denaturation, and exothermic and irreversible aggregation. An α-relaxation assigned to hydration water in BWP appeared at water-content-dependent temperatures and increased to over the range of 150-200 K at decreasing water content and in the presence of GF. Two separate glass transitions and individual fractions of unfrozen water of ternary GF-BWP-water systems contributed to uncoupled α-relaxations, suggesting different roles of protein hydration water and carbohydrate vitrification in concentrated solids during freezing and dehydration. Hydration water in the BWP fraction of GF-BWP systems was derived from equilibrium water sorption and glass transition data of the GF fraction, which gave a significant universal method to quantify (i) protein hydration water and (ii) the unfrozen water in protein-carbohydrate systems for such applications as cryopreservation, freezing, lyophilization, and dehydration of biological materials. A ternary supplemented phase diagram (state diagram) established for the GF-BWP-water system can be used for the analysis of the water distribution across carbohydrate and protein components in such applications.

  19. Traction and lubricant film temperature as related to the glass transition temperature and solidification. [using infrared spectroscopy on EHD contacts

    Science.gov (United States)

    Lauer, J. L.; Peterkin, M. E.

    1978-01-01

    Does a traction fluid have to be a glass or solid under operating conditions. Infrared spectra on dynamic EHD contacts of several types of fluid were used to determine the surface and oil-film temperatures. Polarized spectral runs were made to study molecular alignment. Static glass transition pressures at appropriate temperatures were between 0.1 and 2.0 GPa, with the traction fluid showing the highest. In the EHD contact region, the traction fluid showed both the highest film temperatures as well as the greatest degree of molecular alignment. A plot of the difference between the film and surface temperatures vs shear rate resulted in a master plot valid for all the fluids. From this work, the authors propose a model of 'fluid' traction, where friction between parallel rough molecules provides the traction.

  20. Transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses.

    Science.gov (United States)

    Jang, Dongchan; Greer, Julia R

    2010-03-01

    Amorphous metallic alloys, or metallic glasses, are lucrative engineering materials owing to their superior mechanical properties such as high strength and large elastic strain. However, their main drawback is their propensity for highly catastrophic failure through rapid shear banding, significantly undercutting their structural applications. Here, we show that when reduced to 100 nm, Zr-based metallic glass nanopillars attain ceramic-like strengths (2.25 GPa) and metal-like ductility (25%) simultaneously. We report separate and distinct critical sizes for maximum strength and for the brittle-to-ductile transition, thereby demonstrating that strength and ability to carry plasticity are decoupled at the nanoscale. A phenomenological model for size dependence and brittle-to-homogeneous deformation is provided.

  1. In situ visualization of Ni-Nb bulk metallic glasses phase transition

    OpenAIRE

    Oreshkin, A. I.; Mantsevich, V. N.; Savinov, S. V.; Oreshkin, S. I.; Panov, V. I.; Yavari, A. R.; Miracle, D. B.; Louzguine-Luzgin, D. V.

    2013-01-01

    We report the results of the Ni-based bulk metallic glass structural evolution and crystallization behavior in situ investigation. The X-ray diffraction (XRD), transmission electron microscopy (TEM), nano-beam diffraction (NBD), differential scanning calorimetry (DSC), radial distribution function (RDF) and scanning probe microscopy/spectroscopy (STM/STS) techniques were applied to analyze the structure and electronic properties of Ni63.5Nb36.5 glasses before and after crystallization. It was...

  2. The kinetic glass transition of the Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass former-supercooled liquids on a long time scale

    International Nuclear Information System (INIS)

    Busch, R.; Johnson, W.L.

    1998-01-01

    Viscosity and enthalpy relaxation from the amorphous state into the supercooled liquid state was investigated in the bulk metallic glass forming Zr 46.75 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 alloy below the calorimetric glass transition. At different temperatures, the viscosities relax into states that obey the same Vogel endash Fulcher endash Tammann relation as the data obtained at higher temperatures in the supercooled liquid. Enthalpy recovery experiments after relaxation in the same temperature range show that the enthalpy of the material reaches values that also corresponds to the supercooled liquid state. The glass relaxes into a metastable supercooled liquid state, if it is observed on a long time scale. Equilibration is possible far below the calorimetric glass transition and very likely even below the isentropic temperature. copyright 1998 American Institute of Physics

  3. The glass transition in cured epoxy thermosets: A comparative molecular dynamics study in coarse-grained and atomistic resolution

    Energy Technology Data Exchange (ETDEWEB)

    Langeloth, Michael; Böhm, Michael C.; Müller-Plathe, Florian [Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich Weiss Straße 4, D-64287 Darmstadt (Germany); Sugii, Taisuke, E-mail: taisuke.sugii.zs@hitachi.com [Center for Technology Innovation – Mechanical Engineering, Research & Development Group, Hitachi, Ltd., 832-2, Horiguchi, Hitachinaka, Ibaraki 312-0034 (Japan)

    2015-12-28

    We investigate the volumetric glass transition temperature T{sub g} in epoxy thermosets by means of molecular dynamics simulations. The epoxy thermosets consist of the resin bisphenol A diglycidyl ether and the hardener diethylenetriamine. A structure based coarse-grained (CG) force field has been derived using iterative Boltzmann inversion in order to facilitate simulations of larger length scales. We observe that T{sub g} increases clearly with the degree of cross-linking for all-atomistic (AA) and CG simulations. The transition T{sub g} in CG simulations of uncured mixtures is much lower than in AA-simulations due to the soft nature of the CG potentials, but increases all the more with the formation of rigid cross-links. Additional simulations of the CG mixtures in contact with a surface show the existence of an interphase region of about 3 nm thickness in which the network properties deviate significantly from the bulk. In accordance to experimental studies, we observe that T{sub g} is reduced in this interphase region and gradually increases to its bulk value with distance from the surface. The present study shows that the glass transition is a local phenomenon that depends on the network structure in the immediate environment.

  4. The order parameter of glass transition: Spontaneously delocalized nanoscale solitary wave with transverse ripplon-like soft wave

    Directory of Open Access Journals (Sweden)

    Jia Lin Wu

    2013-06-01

    Full Text Available In macromolecular self-avoiding random walk, movement of each chain-particle accompanies an instantaneous spin system with de Gennes n = 0 that provides extra energy, extra vacancy volume and relaxation time needed for chain-particles co-movement. Using these additional and instantaneous spin systems not only directly yields the same Brownian motion mode in glass transition (GT and reptation-tube model, but also proves that the entangled chain length corresponding to the Reynolds number in hydrodynamics and the inherent diffusion - delocalization mode of entangled chains, from frozen glass state to melt liquid state, is a chain-size solitary wave with transverse ripplon-like soft wave. Thus, the order parameter of GT is found. The various currently available GT theories, such as Static Replica, Random First-Order Transition, Potential Energy Landscape, Mode-Coupling and Nanoscale Heterogeneity, can be unified using the additional and instantaneous spin system. GT served as an inspiration and continues to serve as the paradigm in the universal random delocalization transitions from disorder to more disorder until turbulence.

  5. Evidence for reentrant spin glass behavior in transition metal substituted Co-Ga alloys near critical concentration

    Science.gov (United States)

    Yasin, Sk. Mohammad; Srinivas, V.; Kasiviswanathan, S.; Vagadia, Megha; Nigam, A. K.

    2018-04-01

    In the present study magnetic and electrical transport properties of transition metal substituted Co-Ga alloys (near critical cobalt concentration) have been investigated. Analysis of temperature and field dependence of dc magnetization and ac susceptibility (ACS) data suggests an evidence of reentrant spin glass (RSG) phase in Co55.5TM3Ga41.5 (TM = Co, Cr, Fe, Cu). The magnetic transition temperatures (TC and Tf) are found to depend on the nature of TM element substitution with the exchange coupling strength Co-Fe > Co-Co > Co-Cu > Co-Cr. From magnetization dynamics precise transition temperatures for the glassy phases are estimated. It is found that characteristic relaxation times are higher than that of spin glasses with minimal spin-cluster formation. The RSG behavior has been further supported by the temperature dependence of magnetotransport studies. From the magnetic field and substitution effects it has been established that the magnetic and electrical transport properties are correlated in this system.

  6. Electrochemical determination of the glass transition temperature of thin polyelectrolyte brushes at solid-liquid interfaces by impedance spectroscopy.

    Science.gov (United States)

    Alonso-García, Teodoro; Rodríguez-Presa, María José; Gervasi, Claudio; Moya, Sergio; Azzaroni, Omar

    2013-07-16

    Devising strategies to assess the glass transition temperature (Tg) of polyelectrolyte assemblies at solid-electrolyte interfaces is very important to understand and rationalize the temperature-dependent behavior of polyelectrolyte films in a wide range of settings. Despite the evolving perception of the importance of measuring Tg under aqueous conditions in thin film configurations, its straightforward measurement poses a challenging situation that still remains elusive in polymer and materials science. Here, we describe a new method based on electrochemical impedance spectroscopy (EIS) to estimate the glass transition temperature of planar polyelectrolyte brushes at solid-liquid interfaces. To measure Tg, the charge transfer resistance (Rct) of a redox probe diffusing through the polyelectrolyte brush was measured, and the temperature corresponding to the discontinuous change in Rct was identified as Tg. Furthermore, we demonstrate that impedance measurements not only facilitate the estimation of Tg but also enable a reliable evaluation of the transport properties of the polymeric interface, i.e., determination of diffusion coefficients, close to the thermal transition. We consider that this approach bridges the gap between electrochemistry and the traditional tools used in polymer science and offers new opportunities to characterize the thermal behavior of complex polymeric interfaces and macromolecular assemblies.

  7. The glass transition in cured epoxy thermosets: A comparative molecular dynamics study in coarse-grained and atomistic resolution

    International Nuclear Information System (INIS)

    Langeloth, Michael; Böhm, Michael C.; Müller-Plathe, Florian; Sugii, Taisuke

    2015-01-01

    We investigate the volumetric glass transition temperature T g in epoxy thermosets by means of molecular dynamics simulations. The epoxy thermosets consist of the resin bisphenol A diglycidyl ether and the hardener diethylenetriamine. A structure based coarse-grained (CG) force field has been derived using iterative Boltzmann inversion in order to facilitate simulations of larger length scales. We observe that T g increases clearly with the degree of cross-linking for all-atomistic (AA) and CG simulations. The transition T g in CG simulations of uncured mixtures is much lower than in AA-simulations due to the soft nature of the CG potentials, but increases all the more with the formation of rigid cross-links. Additional simulations of the CG mixtures in contact with a surface show the existence of an interphase region of about 3 nm thickness in which the network properties deviate significantly from the bulk. In accordance to experimental studies, we observe that T g is reduced in this interphase region and gradually increases to its bulk value with distance from the surface. The present study shows that the glass transition is a local phenomenon that depends on the network structure in the immediate environment

  8. Effect of water on glass transition in starch/sucrose matrices investigated through positron annihilation lifetime spectroscopy: a new approach.

    Science.gov (United States)

    Sharma, Sandeep Kumar; Zaydouri, Abdelhadi; Roudaut, Gaëlle; Duplâtre, Gilles

    2011-11-21

    Glass transition is studied through positron annihilation lifetime spectroscopy (PALS) in maize starch matrices containing 10 (batch STS10) and 20 (STS20) w/w% sucrose, as a function of temperature (T) and water content (c(w)). To circumvent important losses of water upon heating while recording the PALS spectra, a new method is developed: instead of a series of measurements of τ(3), the triplet positronium lifetime, at different T, the latter is kept constant and the series relates to c(w), which is left to decrease at a constant rate. Similarly to the changes in τ(3) with T, the τ(3)vs. c(w) plots obtained show a smooth linear increase until a break, denoting the occurrence of glass transition, followed by a sharper increase. The gradients appear to be independent of T. The variation of the glass transition temperature, T(g), with c(w) shows a broad sigmoid with a large linear central part; as expected from the plasticising effect of sucrose, the plot for STS20 lies some 10 K below that for STS10. Results from differential scanning calorimetry for STS20 yield T(g) values some 15 K higher than from PALS. On the basis of the general shape of the τ(3)vs. T variations, a general equation is set for τ(3)(T, c(w)), leading one to expect a similar shape for τ(3)vs. c(w), as experimentally observed. This journal is © the Owner Societies 2011

  9. Thermal stress modification in regenerated fiber Bragg grating via manipulation of glass transition temperature based on CO₂-laser annealing.

    Science.gov (United States)

    Lai, Man-Hong; Lim, Kok-Sing; Gunawardena, Dinusha S; Yang, Hang-Zhou; Chong, Wu-Yi; Ahmad, Harith

    2015-03-01

    In this work, we have demonstrated thermal stress relaxation in regenerated fiber Bragg gratings (RFBGs) by using direct CO₂-laser annealing technique. After the isothermal annealing and slow cooling process, the Bragg wavelength of the RFBG has been red-shifted. This modification is reversible by re-annealing and rapid cooling. It is repeatable with different cooling process in the subsequent annealing treatments. This phenomenon can be attributed to the thermal stress modification in the fiber core by means of manipulation of glass transition temperature with different cooling rates. This finding in this investigation is important for accurate temperature measurement of RFBG in dynamic environment.

  10. The Relationship of Dynamical Heterogeneity to the Adam-Gibbs and Random First-Order Transition Theories of Glass Formation

    OpenAIRE

    Starr, Francis W.; Douglas, Jack F.; Sastry, Srikanth

    2013-01-01

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and stri...

  11. Eigenstates and radiative transition probabilities for Tm3+(4f12) in phosphate and tellurite glasses

    International Nuclear Information System (INIS)

    Spector, N.; Reisfeld, R.; Boehm, L.

    1977-01-01

    Electronic wavefunctions of Tm 3+ in intermediate coupling were obtained and used to calculate the Usup((lambda)) matrix elements between all possible states of the 4f 12 configuration. The Judd-Ofelt intensity parameters Ωsub(lambda) obtained for Tm 3+ in phosphate and tellurite glasses were used in conjunction with the Usup((lambda))'s to calculate the forced electric dipole line strengths. The total electric and magnetic radiative transition probabilities are calculated. The entire theoretical spectrum involving the ground and excited levels (from 129 nm to 16447 nm) is given. (Auth.)

  12. Origin of the strain glass transition in Ti_5_0(Ni_5_0_−_x D_x) alloys

    International Nuclear Information System (INIS)

    Wang, Xu; Shang, Jia-Xiang; Wang, Fu-He; Chen, Yue

    2016-01-01

    Direct evidence was recently discovered for the unique strain glass (STG) transition, which breaks the local symmetries (PRL 112, 025701 (2014)). To understand the origin of the STG transition, the effects of doping point defects on Ti_5_0(Ni_5_0_−_x D_x) are investigated using first-principle calculations. The experimental observation that STG only exists in a limited range of chemical composition x is successfully rationalized. The mechanisms that correspond to the division of a system into domains with distinctly different compositions are found to be directly related to a dip in the defect formation energy. - Highlights: • The strain glass transition phenomenon in Ti−Ni-based alloys is rationalized. • The electronic-structure origins of the strain glass transition are uncovered. • The separation of domains with different compositions is explained.

  13. Glass transition and composite formation in InF{sub 3}-containing oxyfluoroniobate system

    Energy Technology Data Exchange (ETDEWEB)

    Savchenko, N. N.; Ignatieva, L. N.; Marchenko, Yu. V. [Institute of Chemistry FEB RAS, Vladivostok (Russian Federation); Bouznik, V. M. [All-Russian Scientific Research Institute of Aviation Materials (Russian Federation)

    2016-05-18

    The glasses in the system MnNbOF{sub 5}-BaF{sub 2}-InF{sub 3} have been firstly synthesized and studied. The thermal parameters of these glasses are analyzed. It was stated that glass of the composition 40MnNbOF{sub 5}-40BaF{sub 2}-20InF{sub 3} is the most thermal stable in the system under study. By X-ray analysis the compositions of the crystalline phases obtained at the glass thermal treatment were determined: the main phases are Ba{sub 3}In{sub 2}F{sub 12} and BaNbOF{sub 5}. By Raman and IR spectra analysis it was stated that the networks of glasses in the system are built by the structural type of the glasses in NbO{sub 2}F-BaF{sub 2} system: (NbO{sub n}F{sub m}) polyhedra joined oxygen bridges. Indium trifluoride forms InF{sub 6} polyhedra, which are embeded between oxyfluoroniobate ions, forming a common networks or forms its own layers from InF{sub 6} polyhedra. IR-spectroscopy method showed that at devitrification of the sample 30MnNbOF{sub 5}-50BaF{sub 2}-20InF{sub 3} the band position and shape change in going from glass state to crystalline. The bands in the range 900–700 cm{sup −1} shift into the low-frequency range and transformed into narrow peaks characteristic for the crystalline state. It was determined that for this sample the IR-spectroscopy method fixes the presence of the crystalline phases at 340°C without time of exposure, despite the fact that X-ray analysis shows an amorphous state for this sample at the same temperature. It was suggested, that controlling the composition and conditions of annealing of the glasses it can be obtain the transparent glass-ceramics of definite composition.

  14. Transition Communities and the Glass Ceiling of Environmental Sustainability Policies at Three Universities

    Science.gov (United States)

    Pardellas Santiago, Miguel; Meira Cartea, Pablo; Iglesias da Cunha, Lucía

    2017-01-01

    Purpose: This paper deals with the experiences of three European universities that have implemented transition initiatives, using the Transition Network's methodology to promote their sustainability plans. The Transition Communities' model for change is presented from a socio-educational perspective as an effective methodology for encouraging…

  15. Highly sensitive pseudo-differential ac-nanocalorimeter for the study of the glass transition

    International Nuclear Information System (INIS)

    Laarraj, Mohcine; Adhiri, Rahma; Moussetad, Mohamed; Ouaskit, Said; Guttin, Christophe; Richard, Jacques; Garden, Jean-Luc

    2015-01-01

    We present a nanocalorimeter designed for the measurement of the dynamic heat capacity of thin films. The microfabricated sensor, the thermal conditioning of the sensor, as well as the highly stable and low noise electronic chain allow measurements of the real and imaginary parts of the complex specific heat with a resolution Δ C/C of about 10 −5 . The performances of this quasi-differential nanocalorimeter were tested on a model of polymeric glass-former, the polyvinyl acetate (PVAc). The high stability and low noise of the device are essential for accurate studies on non-equilibrium slow relaxing systems such as glasses

  16. Highly sensitive pseudo-differential ac-nanocalorimeter for the study of the glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Laarraj, Mohcine [Institut NÉEL, CNRS, 25 Avenue des Martyrs, F-38042 Grenoble (France); University Grenoble Alpes, Institut NEEL, F-38042 Grenoble (France); Laboratoire d’Ingénierie et des Matériaux (LIMAT), Université Hassan II de Casablanca, Faculté des Sciences Ben M’Sik, Casablanca Maroc (Morocco); Adhiri, Rahma; Moussetad, Mohamed [Laboratoire d’Ingénierie et des Matériaux (LIMAT), Université Hassan II de Casablanca, Faculté des Sciences Ben M’Sik, Casablanca Maroc (Morocco); Ouaskit, Said [Laboratoire de Physique de la Matière Condensée (LPMC), Université Hassan II de Casablanca, Faculté des Sciences Ben M’Sik, Casablanca Maroc (Morocco); Guttin, Christophe; Richard, Jacques; Garden, Jean-Luc [Institut NÉEL, CNRS, 25 Avenue des Martyrs, F-38042 Grenoble (France); University Grenoble Alpes, Institut NEEL, F-38042 Grenoble (France)

    2015-11-15

    We present a nanocalorimeter designed for the measurement of the dynamic heat capacity of thin films. The microfabricated sensor, the thermal conditioning of the sensor, as well as the highly stable and low noise electronic chain allow measurements of the real and imaginary parts of the complex specific heat with a resolution Δ C/C of about 10{sup −5}. The performances of this quasi-differential nanocalorimeter were tested on a model of polymeric glass-former, the polyvinyl acetate (PVAc). The high stability and low noise of the device are essential for accurate studies on non-equilibrium slow relaxing systems such as glasses.

  17. Influence of chain topology and bond potential on the glass transition of polymer chains simulated with the bond fluctuation model

    International Nuclear Information System (INIS)

    Freire, J J

    2008-01-01

    The bond fluctuation model with a bond potential has been applied to investigation of the glass transition of linear chains and chains with a regular disposition of small branches. Cooling and subsequent heating curves are obtained for the chain energies and also for the mean acceptance probability of a bead jump. In order to mimic different trends to vitrification, a factor B gauging the strength of the bond potential with respect to the long-range potential (i.e. the intramolecular or intermolecular potential between indirectly bonded beads) has been introduced. (A higher value of B leads to a preference for the highest bond lengths and a higher total energy, implying a greater tendency to vitrify.) Different cases have been considered for linear chains: no long-range potential, no bond potential and several choices for B. Furthermore, two distinct values of B have been considered for alternate bonds in linear chains. In the case of the branched chains, mixed models with different values of B for bonds in the main chain and in the branches have also been investigated. The possible presence of ordering or crystallization has been characterized by calculating the collective light scattering function of the different samples after annealing at a convenient temperature below the onset of the abrupt change in the curves associated with a thermodynamic transition. It is concluded that ordering is inherited more efficiently in the systems with branched chains and also for higher values of B. The branched molecules with the highest B values in the main chain bonds exhibit two distinct transitions in the heating curves, which may be associated with two glass transitions. This behavior has been detected experimentally for chains with relatively long flexible branches

  18. Influence of chain topology and bond potential on the glass transition of polymer chains simulated with the bond fluctuation model

    Energy Technology Data Exchange (ETDEWEB)

    Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), Senda del Rey 9, 28040 Madrid (Spain)], E-mail: jfreire@invi.uned.es

    2008-07-16

    The bond fluctuation model with a bond potential has been applied to investigation of the glass transition of linear chains and chains with a regular disposition of small branches. Cooling and subsequent heating curves are obtained for the chain energies and also for the mean acceptance probability of a bead jump. In order to mimic different trends to vitrification, a factor B gauging the strength of the bond potential with respect to the long-range potential (i.e. the intramolecular or intermolecular potential between indirectly bonded beads) has been introduced. (A higher value of B leads to a preference for the highest bond lengths and a higher total energy, implying a greater tendency to vitrify.) Different cases have been considered for linear chains: no long-range potential, no bond potential and several choices for B. Furthermore, two distinct values of B have been considered for alternate bonds in linear chains. In the case of the branched chains, mixed models with different values of B for bonds in the main chain and in the branches have also been investigated. The possible presence of ordering or crystallization has been characterized by calculating the collective light scattering function of the different samples after annealing at a convenient temperature below the onset of the abrupt change in the curves associated with a thermodynamic transition. It is concluded that ordering is inherited more efficiently in the systems with branched chains and also for higher values of B. The branched molecules with the highest B values in the main chain bonds exhibit two distinct transitions in the heating curves, which may be associated with two glass transitions. This behavior has been detected experimentally for chains with relatively long flexible branches.

  19. Density crosslink study of gamma irradiated LDPE predicted by gel-fraction, swelling and glass transition temperature characterization

    International Nuclear Information System (INIS)

    Cardoso, Elisabeth C.L.; Scagliusi, Sandra R.; Moraes, Guilherme F.; Ono, Lilian S.; Parra, D.F.; Lugao, Ademar B.

    2011-01-01

    Experimental results showed that the crosslink density of polymeric stocks may be predicted from values of gel content based on the reactive portion of the stocks, that is, exclusive of plasticizers and fillers. Where entanglements may be neglected, the crosslink density is directly proportional to functions of the gel and sol contents. In order to predict the behavior of carbon-chain polymers exposed to ionizing radiation, an empirical rule can be used. According to this rule, polymers containing a hydrogen atom at each carbon atom predominantly undergo crosslinking. During irradiation, chain scission occurs simultaneously and competitively with crosslinking, the end result being determined by the ratio of the yields of the two reactions. The ratio of crosslinking to scission depends basically on factors including total irradiation dose, dose rate and the presence of oxygen. The glass transition temperature (Tg), temperature below which the polymer segments do not have sufficient energy to move past one another, marks the onset of segmental mobility for a polymer. Properties such as melt index, melt strength, crystallinity, glass transition, gel fraction, swelling ratio and elasticity modulus were assessed in LDPE (2.6 g.10 min -1 melt index) gamma irradiated within a 10, 15, 20 and 30 kGy and results obtained were further discussed prior conclusion. (author)

  20. Mobility of supercooled liquid toluene, ethylbenzene, and benzene near their glass transition temperatures investigated using inert gas permeation.

    Science.gov (United States)

    May, R Alan; Smith, R Scott; Kay, Bruce D

    2013-11-21

    We investigate the mobility of supercooled liquid toluene, ethylbenzene, and benzene near their respective glass transition temperatures (Tg). The permeation rate of Ar, Kr, and Xe through the supercooled liquid created when initially amorphous overlayers are heated above their glass transition temperature is used to determine the diffusivity. Amorphous benzene crystallizes at temperatures well below its Tg, and as a result, the inert gas underlayer remains trapped until the onset of benzene desorption. In contrast, for toluene and ethylbenzene the onset of inert gas permeation is observed at temperatues near Tg. The inert gas desorption peak temperature as a function of the heating rate and overlayer thickness is used to quantify the diffusivity of supercooled liquid toluene and ethylbenzene from 115 to 135 K. In this temperature range, diffusivities are found to vary across 5 orders of magnitude (∼10(-14) to 10(-9) cm(2)/s). The diffusivity data are compared to viscosity measurements and reveal a breakdown in the Stokes-Einstein relationship at low temperatures. However, the data are well fit by the fractional Stokes-Einstein equation with an exponent of 0.66. Efforts to determine the diffusivity of a mixture of benzene and ethylbenzene are detailed, and the effect of mixing these materials on benzene crystallization is explored using infrared spectroscopy.

  1. An investigation into the effects of residual water on the glass transition temperature of polylactide microspheres using modulated temperature DSC.

    Science.gov (United States)

    Passerini, N; Craig, D Q

    2001-05-18

    The objective of the study was to ascertain residual water levels in polylactide and polylactide-co-glycolide microspheres prepared using the solvent evaporation technique and to investigate the effects of that water on the glass transitional behaviour of the microspheres. Microspheres were prepared from polylactic acid (PLA) and polylactide-co-glycolide (PLGA) 50:50 and 75:25 using a standard solvent evaporation technique. The glass transition was measured as a function of drying conditions using modulated temperature DSC. The microspheres were found to contain very low levels of dichloromethane, while residual water levels of up to circa 3% w/w were noted after freeze or oven drying, these levels being higher for microspheres containing higher glycolic acid levels. The residual water was found to lower the T(g) following the Gordon-Taylor relationship. The data indicate that the microparticles may retain significant water levels following standard preparation and drying protocols and that this drying may markedly lower the T(g) of the spheres.

  2. EFFECTS OF TRITIUM GAS EXPOSURE ON THE GLASS TRANSITION TEMPERATURE OF EPDM ELASTOMER AND ON THE CONDUCTIVITY OF POLYANILINE

    Energy Technology Data Exchange (ETDEWEB)

    Clark, E; Marie Kane, M

    2008-12-12

    Four formulations of EPDM (ethylene-propylene diene monomer) elastomer were exposed to tritium gas initially at one atmosphere and ambient temperature for between three and four months in closed containers. Material properties that were characterized include density, volume, mass, appearance, flexibility, and dynamic mechanical properties. The glass transition temperature was determined by analysis of the dynamic mechanical property data per ASTM standards. EPDM samples released significant amounts of gas when exposed to tritium, and the glass transition temperature increased by about 3 C. during the exposure. Effects of ultraviolet and gamma irradiation on the surface electrical conductivity of two types of polyaniline films are also documented as complementary results to planned tritium exposures. Future work will determine the effects of tritium gas exposure on the electrical conductivity of polyaniline films, to demonstrate whether such films can be used as a sensor to detect tritium. Surface conductivity was significantly reduced by irradiation with both gamma rays and ultraviolet light. The results of the gamma and UV experiments will be correlated with the tritium exposure results.

  3. Dynamical heterogeneities and mechanical non-linearities: Modeling the onset of plasticity in polymer in the glass transition.

    Science.gov (United States)

    Masurel, R J; Gelineau, P; Lequeux, F; Cantournet, S; Montes, H

    2017-12-27

    In this paper we focus on the role of dynamical heterogeneities on the non-linear response of polymers in the glass transition domain. We start from a simple coarse-grained model that assumes a random distribution of the initial local relaxation times and that quantitatively describes the linear viscoelasticity of a polymer in the glass transition regime. We extend this model to non-linear mechanics assuming a local Eyring stress dependence of the relaxation times. Implementing the model in a finite element mechanics code, we derive the mechanical properties and the local mechanical fields at the beginning of the non-linear regime. The model predicts a narrowing of distribution of relaxation times and the storage of a part of the mechanical energy --internal stress-- transferred to the material during stretching in this temperature range. We show that the stress field is not spatially correlated under and after loading and follows a Gaussian distribution. In addition the strain field exhibits shear bands, but the strain distribution is narrow. Hence, most of the mechanical quantities can be calculated analytically, in a very good approximation, with the simple assumption that the strain rate is constant.

  4. A novel approach for analyzing glass-transition temperature vs. composition patterns: application to pharmaceutical compound+polymer systems.

    Science.gov (United States)

    Kalogeras, Ioannis M

    2011-04-18

    In medicine, polymer-based materials are commonly used as excipients of poorly water-soluble drugs. The success of the encapsulation, as well as the physicochemical stability of the products, is often reflected on their glass transition temperature (T(g)) vs. composition (w) dependencies. The shape of the T(g)(w) patterns is critically influenced by polymer's molecular mass, drug molecule's shape and molecular volume, the type and degree of shielding of hydrogen-bonding capable functional groups, as well as aspects of the preparation process. By altering mixture's T(g) the amorphous solid form of the active ingredient may be retained at ambient or body temperatures, with concomitant improvements in handling, solubility, dissolution rate and oral bioavailability. Given the importance of the problem, the glass transitions observed in pharmaceutical mixtures have been extensively analyzed, aiming to appraise the state of mixing and intermolecular interactions. Here, accumulated experimental information on related systems is re-evaluated and comparably discussed under the light of a more effective and system-inclusive T(g)(w) equation. The present analysis indicates that free volume modifications and conformational changes of the macromolecular chains dominate, over enthalpic effects of mixing, in determining thermal characteristics and crystallization inhibition/retardation. Moreover, hydrogen-bonding and ion-dipole heterocontacts--although favorable of a higher degree of mixing--appear less significant compared to the steric hindrances and the antiplasticization proffered by the higher viscosity component. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Development of DMBZ-15 High-Glass-Transition-Temperature Polyimides as PMR-15 Replacements Given R&D 100 Award

    Science.gov (United States)

    Chuang, Kathy

    2004-01-01

    PMR-15, a high-temperature polyimide developed in the mid-1970s at the NASA Lewis Research Center,1 offers the combination of low cost, easy processing, and good high-temperature performance and stability. It has been recognized as the leading polymer matrix resin for carbon-fiber-reinforced composites used in aircraft engine components. The state-of-the-art PMR-15 polyimide composite has a glass-transition temperature (Tg) of 348 C (658 F). Since composite materials must be used at temperatures well below their glass-transition temperature, the long-term use temperatures of PMR-15 composites can be no higher than 288 C (550 F). In addition, PMR-15 is made from methylene dianiline (MDA), a known liver toxin. Concerns about the safety of workers exposed to MDA during the fabrication of PMR-15 components and about the environmental impact of PMR-15 waste disposal have led to the industry-wide implementation of special handling procedures to minimize the health risks associated with this material. These procedures have increased manufacturing and maintenance costs significantly and have limited the use of PMR-15 in commercial aircraft engine components.

  6. Mean-field solution of the Potts glass near the transition temperature to the ordered phase

    Czech Academy of Sciences Publication Activity Database

    Janiš, Václav; Klíč, Antonín

    2011-01-01

    Roč. 84, č. 6 (2011), "064446-1"-"064446-10" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520 Keywords : Potts glass * hierarchic solutions with replicated spins * continuous replica-symmetry breaking Subject RIV: BE - Theoretical Physics Impact factor: 3.691, year: 2011

  7. High temperature spin-glass-like transition in La0.67Sr0.33MnO3 nanofibers near the Curie point.

    Science.gov (United States)

    Lu, Ruie; Yang, Sen; Li, Yitong; Chen, Kaiyun; Jiang, Yun; Fu, Bi; Zhang, Yin; Zhou, Chao; Xu, Minwei; Zhou, Xuan

    2017-06-28

    The glassy transition of superparamagnetic (SPM) (r glass-like (SGL) behavior near the Curie point (T C ), i.e., T 0 = 330 K, in La 0.67 Sr 0.33 MnO 3 (LSMO) nanofibers (NFs) composed of nanoparticles beyond the SPM size (r ≫ r 0 ), resulting in a significant increase of the glass transition temperature. This SGL transition near the T C of bulk LSMO can be explained to be the scenario of locally ordered clusters embedded in a disordered host, in which the assembly of nanoparticles has a magnetic core-shell model driven by surface spin glass. The presence of a surface spin glass of nanoparticles was proved by the Almeida-Thouless line δT f ∝ H 2/3 , exchange bias, and reduced saturation magnetization of the NF system. Composite dynamics were found - that is, both the SPM and the super-spin-glass (SSG) behavior are found in such an NF system. The bifurcation of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization vs. temperature curves at the ZFC peak, and the flatness of FC magnetization involve SSG, while the frequency-dependent ac susceptibility anomaly follows the Vogel-Fulcher law that implies weak dipole interactions of the SPM model. This finding can help us to find a way to search for high temperature spin glass materials.

  8. Thermal expansion of amorphous Zr65Al7.5Cu17.5Ni10 in the vicinity of the glass transition

    International Nuclear Information System (INIS)

    Geier, N.; Weiss, M.; Moske, M.; Samwer, K.

    2000-01-01

    The thermal expansion of non-crystalline Zr 65 Al 7.5 Cu 17.5 Ni 10 has been studied in the range of the glass transition and in the undercooled liquid using a dilatometric device. The measuring technique used permits reliable experimental results up to 40 K above the glass transition temperature. The linear thermal expansion coefficient obtained is almost constant in the glassy state with a value of 8.0 x 10 -6 K -1 . It discontinuously increases at the glass transition temperature yielding a value of 20.0 x 10 -6 K -1 in the undercooled liquid. The results are compared with specific heat measurements of the amorphous material in this temperature range and are interpreted in the framework of a cluster model. (orig.)

  9. Determination of the Glass-Transition Temperature of GRPS and CFRPS Using a Torsion Pendulum in Regimes of Freely Damped Vibrations and Quasi-Stastic Torsion of Specimens

    Science.gov (United States)

    Startsev, V. O.; Lebedev, M. P.; Molokov, M. V.

    2018-03-01

    A method to measure the glass-transition temperature of polymers and polymeric matrices of composite materials with the help of an inverse torsion pendulum over a wide range of temperatures is considered combining the method of free torsional vibrations and a quasi-static torsion of specimens. The glass-transition temperature Tg of a KMKS-1-80. T10 fiberglass, on increasing the frequency of freely damped torsional vibrations from 0.7 to 9.6 Hz, was found to increase from 132 to 140°C. The value of Tg of these specimens, determined by measuring the work of their torsion through a small fixed angle was 128.6°C ± 0.8°C. It is shown that the use of a torsion pendulum allows one to determine the glass-transition temperature of polymeric or polymer matrices of PCMs in dynamic and quasi-static deformation regimes of specimens.

  10. Positron annihilation in some barium borate glasses containing transition metal oxides

    International Nuclear Information System (INIS)

    Usmar, S.G.; Rawson, H.; West, R.N.

    1982-01-01

    Results of positron lifetime and angular correlation measurements for the glass series xMsub(s)Osub(r):(1-x)(0.4BaO:0.6B 2 O 3 ) are presented (Msub(s)Osub(r) equivalent to V 2 O 5 ;Fe 2 O 3 and CuO). All glasses exhibit two or three component lifetime spectra, tau 1 approximately 200 ps; tau 2 approximately 300-400 ps and tau 3 approximately 780 ps. tau 1 is attributed to a mixture of pPs and bulk state annihilation, tau 2 to a trapped or bound state and tau 3 to oPs pick-off. Supporting evidence for these assignments is found in the angular correlation results. (Auth.)

  11. Solvent-Induced Crystallization in Poly(Ethylene Terephthalate) during Mass Transport

    Science.gov (United States)

    Ouyang, Hao

    2001-03-01

    The solvent transport in poly(ethylene terephthalate) (PET) and related phase transformation were investigated. The data of mass sorption were analyzed according to Harmon¡¦s model for Case I (Fickian), Case II (swelling) and anomalous transport. This transport process in PET is accompanied by the induced crystallization of the original amorphous state. The transformation was studied by wide angle x-ray scattering (WAXS), small angle x-ray scattering (SAXS), Differential Scanning Calorimeter (DSC), density gradient column, and Fourier Transform Infra-Red (FTIR). During this process, the matrix is under a compressive strain that causes different kinetic path of crystallization as compared to that by thermal annealing. This state of strain will assist the development of the solvent-induced crystallization. It also can be explained in terms of the principle of Le Chatelier if the local equilibrium is assumed. The model regarding the crystallization was proposed in terms of the study of long period L, the crystal thickness lc and the thickness of amorphous layer la, obtained from the linear correlation function and interface distribution function.

  12. Solvent induced fluorescence enhancement of graphene oxide studied by ultrafast spectroscopy

    Science.gov (United States)

    Zhao, Litao; Chen, Jinquan; He, Xiaoxiao; Yu, Xiantong; Yan, Shujun; Zhang, Sanjun; Pan, Haifeng; Xu, Jianhua

    2018-05-01

    Femtosecond transient absorption (TA) spectroscopy combined with picosecond time resolved fluorescence (TRF) were used to reveal the fluorescence kinetics of graphene oxide (GO) in water, ethanol and water-ethanol mixtures. Size-independent fluorescence of GO were observed in water, and pH-dependent fluorescence spectra could be fitted well by a triple emission relaxation with peaks around 440 nm, 500 nm, and 590 nm respectively. The results indicate that polycyclic aromatic hydrocarbons (PAHs) linked by oxygen-containing functional groups dominate GO's fluorescence emission. GO's fluorescence quantum yield was measured to be 2.8% in ethanol but 1.2% in water. The three decay components fluorescence decay, as well as the transient absorption dynamics with an offset, confirmed this solvent induced fluorescence enhancement. GO's Raman spectral signals showed that GO in ethanol has a smaller average size of PAHs than that of GO in water. Therefore, besides other enhancement effects reported in literatures, we proposed that solvents could also change the size of PAHs, resulting in a photoluminescence enhancement. Our experimental data demonstrates that GO's quantum yield could be up to 2.8% in water and 8.4% in ethanol and this observation may help ones to improve GO's photoluminescence efficiency as well as its applications in solution.

  13. Yield stress in metallic glasses: The jamming-unjamming transition studied through Monte Carlo simulations based on the activation-relaxation technique

    International Nuclear Information System (INIS)

    Rodney, David; Schuh, Christopher A.

    2009-01-01

    A Monte Carlo approach allowing for stress control is employed to study the yield stress of a two-dimensional metallic glass in the limit of low temperatures and long (infinite) time scales. The elementary thermally activated events are determined using the activation-relaxation technique (ART). By tracking the minimum-energy state of the glass for various applied stresses, we find a well-defined jamming-unjamming transition at a yield stress about 30% lower than the steady-state flow stress obtained in conventional strain-controlled quasistatic simulations. ART is then used to determine the evolution of the distribution of thermally activated events in the glass microstructure both below and above the yield stress. We show that aging below the yield stress increases the stability of the glass, both thermodynamically (the internal potential energy decreases) and dynamically (the aged glass is surrounded by higher-energy barriers than the initial quenched configuration). In contrast, deformation above the yield stress brings the glass into a high internal potential energy state that is only marginally stable, being surrounded by a high density of low-energy barriers. The strong influence of deformation on the glass state is also evidenced by the microstructure polarization, revealed here through an asymmetry of the distribution of thermally activated inelastic strains in glasses after simple shear deformation.

  14. Final Report on DE-FG02-04ER46107: Glasses, Noise and Phase Transitions

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Clare C. [Univ. of California, Irvine, CA (United States)

    2011-12-31

    We showed that noise has distinct signatures at phase transitions in spin systems. We also studied charge noise, critical current noise, and flux noise in superconducting qubits and Josephson junctions.

  15. Rheology of confined granular flows: scale invariance, glass transition, and friction weakening.

    Science.gov (United States)

    Richard, P; Valance, A; Métayer, J-F; Sanchez, P; Crassous, J; Louge, M; Delannay, R

    2008-12-12

    We study fully developed, steady granular flows confined between parallel flat frictional sidewalls using numerical simulations and experiments. Above a critical rate, sidewall friction stabilizes the underlying heap at an inclination larger than the angle of repose. The shear rate is constant and independent of inclination over much of the flowing layer. In the direction normal to the free surface, the solid volume fraction increases on a scale equal to half the flowing layer depth. Beneath a critical depth at which internal friction is invariant, grains exhibit creeping and intermittent cage motion similar to that in glasses, causing gradual weakening of friction at the walls.

  16. On the Frequency Correction in Temperature-Modulated Differential Scanning Calorimetry of Glass Transition

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    2012-01-01

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Simulations of TMDSC signals were performed for Corning EAGLE XG® glass over a wide range of modulation frequencies. Our results reveal that the frequency...... correction commonly used in the interpretation of TMDSC signals leads to a master nonreversing heat flow curve independent of modulation frequency, provided that sufficiently high frequencies are employed in the TMDSC measurement. A master reversing heat flow curve can also be generated through the frequency...

  17. Analysis on the phase transition behavior of Cu base bulk metallic glass by electrical resistivity measurement

    International Nuclear Information System (INIS)

    Ji, Young Su; Chung, Sung Jae; Ok, Myoung-Ryul; Hong, Kyung Tae; Suh, Jin-Yoo; Byeon, Jai Won; Yoon, Jin-Kook; Lee, Kyung Hwan; Lee, Kyung Sub

    2007-01-01

    The crystallization behavior of Cu 43 Zr 43 Al 7 Ag 7 (numbers indicate at.%) bulk metallic glass was investigated using the isothermal electrical resistivity measurements at 450 deg. C in the supercooled liquid region. The crystallization process is a single step phase transformation. To analyze the electrical resistivity reduction, microstructure evolutions were analyzed using differential scanning calorimetry, X-ray diffraction, transmission electron microscopy and small-angle X-ray scattering. The Avrami parameter of the electrical resistivity reduction step was 1.73, indicating that the crystallization process is a diffusion-controlled growth of intermetallic compounds with decreasing nucleation rate

  18. Influence of ejection temperature on structure and glass transition behavior for Zr-based rapidly quenched disordered alloys

    International Nuclear Information System (INIS)

    Wang, X.H.; Inoue, A.; Kong, F.L.; Zhu, S.L.; Stoica, M.; Kaban, I.; Chang, C.T.; Shalaan, E.; Al-Marzouki, F.; Eckert, J.

    2016-01-01

    We examined the influence of ejection liquid temperature (T el ) on the structure, thermal stability and crystallization of Zr−Al−Ni−Cu ribbons prepared by the melt-spinning technique. The increase in T el was found to cause the formation of an oxide phase on the ribbon surface, more loose atomic configurations, the absence of glass transition (GT) and supercooled liquid (SL) region, and the rise of crystallization temperature. The changes in the GT and SL region occur reversibly by controlling the T el . Neither the change in alloy composition except oxygen nor the difference in crystallized phases is seen. Their hardness increases significantly by the disappearance of GT and SL region. The reversible changes in the appearance and disappearance of GT and SL region was found for different Zr-based glassy ribbons, being independent of alloy compositions. The disappearance is presumably due to the change in atomic configurations from high-coordinated to less-coordinated atomic packing in the melt-spun ribbons by freezing high-temperature liquid. The observed phenomenon of the reversible changes provides a novel opportunity for deep understanding of mutual correlations among liquid structure, GT, stability of SL and bulk glass-forming ability for metallic alloys.

  19. From boiling point to glass transition temperature: transport coefficients in molecular liquids follow three-parameter scaling.

    Science.gov (United States)

    Schmidtke, B; Petzold, N; Kahlau, R; Hofmann, M; Rössler, E A

    2012-10-01

    The phenomenon of the glass transition is an unresolved problem in condensed matter physics. Its prominent feature, the super-Arrhenius temperature dependence of the transport coefficients, remains a challenge to be described over the full temperature range. For a series of molecular glass formers, we combined τ(T) collected from dielectric spectroscopy and dynamic light scattering covering a range 10(-12) s < τ(T) < 10(2) s. Describing the dynamics in terms of an activation energy E(T), we distinguish a high-temperature regime characterized by an Arrhenius law with a constant activation energy E(∞) and a low-temperature regime for which E(coop)(T) ≡ E(T)-E(∞) increases exponentially while cooling. A scaling is introduced, specifically E(coop)(T)/E(∞) [proportionality] exp[-λ(T/T(A)-1)], where λ is a fragility parameter and T(A) a reference temperature proportional to E(∞). In order to describe τ(T) still the attempt time τ(∞) has to be specified. Thus, a single interaction parameter E(∞) describing the high-temperature regime together with λ controls the temperature dependence of low-temperature cooperative dynamics.

  20. Annealing effect reversal by water sorption-desorption and heating above the glass transition temperature-comparison of properties.

    Science.gov (United States)

    Saxena, A; Jean, Y C; Suryanarayanan, R

    2013-08-05

    Our objective is to compare the physical properties of materials obtained from two different methods of annealing reversal, that is, water sorption-desorption (WSD) and heating above glass transition temperature (HAT). Trehalose was annealed by storing at 100 °C for 120 h. The annealing effect was reversed either by WSD or HAT, and the resulting materials were characterized by differential scanning calorimetry (DSC), water sorption studies, and positron annihilation spectroscopy (PAS). While the products obtained by the two methods of annealing reversal appeared to be identical by conventional characterization methods, they exhibited pronounced differences in their water sorption behavior. Positron annihilation spectroscopy (PAS), by measuring the fractional free volume changes in the processed samples, provided a mechanistic explanation for the differences in the observed behavior.

  1. Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

    Science.gov (United States)

    Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

    2014-02-01

    Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

  2. First-order dynamical phase transition in models of glasses: an approach based on ensembles of histories

    International Nuclear Information System (INIS)

    Garrahan, Juan P; Jack, Robert L; Lecomte, Vivien; Duijvendijk, Kristina van; Wijland, Frederic van; Pitard, Estelle

    2009-01-01

    We investigate the dynamics of kinetically constrained models of glass formers by analysing the statistics of trajectories of the dynamics, or histories, using large deviation function methods. We show that, in general, these models exhibit a first-order dynamical transition between active and inactive dynamical phases. We argue that the dynamical heterogeneities displayed by these systems are a manifestation of dynamical first-order phase coexistence. In particular, we calculate dynamical large deviation functions, both analytically and numerically, for the Fredrickson-Andersen model, the East model, and constrained lattice gas models. We also show how large deviation functions can be obtained from a Landau-like theory for dynamical fluctuations. We discuss possibilities for similar dynamical phase-coexistence behaviour in other systems with heterogeneous dynamics

  3. Study of viscosity of aluminum melt during glass transition by molecular dynamics and Green–Kubo formula

    International Nuclear Information System (INIS)

    Kirova, E M; Pisarev, V V

    2016-01-01

    Molecular dynamics study of shear viscosity behavior of liquid aluminum is performed. The embedded atom method potential is used at the simulation of isobaric cooling. The viscosity is calculated using the Green–Kubo formula. The stress autocorrelation functions are obtained in the range 300-1200 K. The calculated kinematic viscosity is in agreement with the experimental data for the temperatures above melting temperature. The steep change of the shear viscosity is found below 650 K which we associate with the glass transition and is in a good agreement with the temperature which is obtained using the calorimetric criterion Kolotova et al (2015 J. Non-Cryst. Solids 429 98). The viscosity coefficient can not be calculated using the direct atomistic simulations below that temperature. (paper)

  4. The effect of heat treatment and irradiation on some physical properties of lithium borate glass containing transition elements

    International Nuclear Information System (INIS)

    Soliman, A.A.; Aly, S.A.; Frhan, H.; Abo-Zeid, Y.M.

    1999-01-01

    The effect of introducing iron, nickel and cobalt oxide on some physical properties investigated in this article. The electrical conductivity has a higher value in samples containing 1 mol% transition metal oxides. The conductivity decreased as the content of transition metal oxide increased up to 5 mol% which was due to the change of Fe 2+ to Fe 3+ and increase of Co and Ni ions in octahedral state. The effect of heat treatment on the conductivity measurements shows a decrease in the conductivity values for glass samples with increasing the heat treatment time up to 72 h. This decrease could be attributed to the change in the structure of the glass samples. The investigation of radiation doses with the electrical conductivity concluded that the conductivity increased with increase the irradiation doses. The reason of that may be due to increasing the number of vacancies and vacancy interstitial pairs which are created. The magnetic susceptibility measurements showed an increase in the magnetic susceptibility as Fe 2 O 3 and NiO were increased. While for samples containing CoO the magnetic susceptibility changed due to the change in coordination number of the Co ions. The effect of heat treatment on magnetic susceptibility of the investigated samples concluded that the magnetic susceptibilities have a random behavior with increasing time of heat treatment. By investigating irradiation doses with a magnetic susceptibility it was found that the increase of irradiation dose promotes a tendency to change the magnetic susceptibility values. This change can be related to the presence of structure defects and impurities in the samples before irradiation

  5. Predict the glass transition temperature and plasticization of β-cyclodextrin/water binary system by molecular dynamics simulation.

    Science.gov (United States)

    Zhou, Guohui; Zhao, Tianhai; Wan, Jie; Liu, Chengmei; Liu, Wei; Wang, Risi

    2015-01-12

    The glass transition temperature, diffusion behavior and plasticization of β-cyclodextrin (β-CD), and three amorphous β-CD/water mixtures (3%, 5% and 10% [w/w] water, respectively) were investigated by molecular dynamics simulation, which were performed using Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field and isothermal-isobaric ensembles. The specific volumes of four amorphous cells were obtained as a function of temperature. The glass transition temperatures (T(g)) were estimated to be 334.25 K, 325.12 K, 317.32 K, and 305.41 K for amorphous β-CD containing 0%, 3%, 5% and 10% w/w water, respectively, which compares well with the values observed in published literature. The radial distribution function was computed to elucidate the intermolecular interactions between amorphous β-CD and water, which acts as a plasticizer. These results indicate that the hydrogen bond interactions of oxygen in hydroxyl ions was higher than oxygen in acetal groups in β-CD amorphous mixtures with that in water, due to less accessibility of ring oxygens to the surrounding water molecules. The mobility of water molecules was investigated over various temperature ranges, including the rubbery and glassy phases of the β-CD/water mixtures, by calculating the diffusion coefficients and the fractional free volume. In β-CD amorphous models, the higher mobility of water molecules was observed at temperatures above Tg, and almost no change was observed at temperatures below T(g). Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Reorientational dynamics in molecular liquids as revealed by dynamic light scattering: from boiling point to glass transition temperature.

    Science.gov (United States)

    Schmidtke, B; Petzold, N; Kahlau, R; Rössler, E A

    2013-08-28

    We determine the reorientational correlation time τ of a series of molecular liquids by performing depolarized light scattering experiments (double monochromator, Fabry-Perot interferometry, and photon correlation spectroscopy). Correlation times in the range 10(-12) s-100 s are compiled, i.e., the full temperature interval between the boiling point and the glass transition temperature T(g) is covered. We focus on low-T(g) liquids for which the high-temperature limit τ ≅ 10(-12) s is easily accessed by standard spectroscopic equipment (up to 440 K). Regarding the temperature dependence three interpolation formulae of τ(T) with three parameters each are tested: (i) Vogel-Fulcher-Tammann equation, (ii) the approach recently discussed by Mauro et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 19780 (2009)], and (iii) our approach decomposing the activation energy E(T) in a constant high temperature value E∞ and a "cooperative part" E(coop)(T) depending exponentially on temperature [Schmidtke et al., Phys. Rev. E 86, 041507 (2012)]. On the basis of the present data, approaches (i) and (ii) are insufficient as they do not provide the correct crossover to the high-temperature Arrhenius law clearly identified in the experimental data while approach (iii) reproduces the salient features of τ(T). It allows to discuss the temperature dependence of the liquid's dynamics in terms of a E(coop)(T)/E∞ vs. T/E∞ plot and suggests that E∞ controls the energy scale of the glass transition phenomenon.

  7. Degradation of lipids in yeast (Saccharomyces cerevisiae) at the early phase of organic solvent-induced autolysis

    International Nuclear Information System (INIS)

    Ishida-Ichimasa, Michiko

    1978-01-01

    Initial stage of organic solvent-induced autolysis in yeast was studied with 14 C-acetate labeled cells. In the case of toluene-induced autolysis, primary cell injury which was estimated by leakage of UV absorbing substances from cell accompanied rapid deacylation of phospholipids. Lysophospholipids did not occur during autolysis. When autolysis was induced by addition of ethyl acetate, phospholipids of yeast cells were not degraded so much. Ethyl acetate rather inhibited yeast phospholipase activity under the condition tested. (auth.)

  8. Dynamics of a thermo-responsive microgel colloid near to the glass transition

    Science.gov (United States)

    Di, Xiaojun; Peng, Xiaoguang; McKenna, Gregory B.

    2014-02-01

    In a previous study, we used diffusing wave spectroscopy (DWS) to investigate the aging signatures of a thermo-sensitive colloidal glass and compared them with those of molecular glasses from the perspective of the Kovacs temperature-jump, volume recovery experiments [X. Di, K. Z. Win, G. B. McKenna, T. Narita, F. Lequeux, S. R. Pullela, and Z. Cheng, Phys. Rev. Lett. 106, 095701 (2011)]. In order to further look into the glassy behavior of colloidal systems, we have synthesized a new core/shell particle with lower temperature sensitivity and studied the aging signatures of concentrated systems, again following Kovacs' protocol. Similar signatures of aging to those observed previously were seen in this new system. Moreover, a systematic study of the temperature dependence of the dynamics of the new system for different weight concentrations was performed and the dynamic fragility index m was determined. We have also explored the use of the properties determined from the DWS measurements to obtain macroscopic rheological parameters - storage modulus G'(ω) and loss modulus G″(ω) - using a generalized Stokes-Einstein approach. The micro-rheological and macro-rheological values are in reasonable agreement.

  9. Pressure-controlled nucleation and growth in Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass close to and beyond glass transition temperature

    International Nuclear Information System (INIS)

    Pan Mingxiang; Yao Yushu; Zhao Deqian; Zhuang Yanxin; Wang Weihua

    2002-01-01

    By high-pressure annealing close to and beyond glass transition temperature, the behavior of nucleation and growth of crystals in Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass (BMG) is investigated. The experimental results indicate that exerting a high pressure during annealing can markedly decrease the nucleation temperature of the BMG. The growth rate of crystals first increases and then decreases with increase of annealing pressure. The effect of pressure on nucleation and growth of crystals is phenomenologically explained

  10. Dynamic cooperative behavior of constituting species at the glass transition vicinity: Inspirational links to Bořivoj Hlaváček (1941-2014) legacy

    Czech Academy of Sciences Publication Activity Database

    Šesták, Jaroslav

    2015-01-01

    Roč. 120, č. 1 (2015), s. 167-173 ISSN 1388-6150 Institutional support: RVO:68378271 Keywords : glass transition temperature * crossover and void temperature * linear and nonlinear oscillations * viscoelasticity * shear viscosity Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 1.781, year: 2015

  11. Glass transition temperatures of microphase separated semi-interpenetrating polymer networks of polystyrene-inter-poly(cross)-2-ethylhexyl-methacrylate

    NARCIS (Netherlands)

    de Graaf, L.A.; de Graaf, Leontine A.; Möller, Martin; Moller, M.

    1995-01-01

    The glass transition temperature of semi-interpenetrating polymer networks (semi-IPNs) of atactic polystyrene (PS) in crosslinked methacrylates was studied by systematic variation of the morphology, that is domain size, continuity and concentration in the domains. Semi-IPNs were prepared from

  12. Aging effects around the glass and melting transitions in poly(dimethylsiloxane) visualized by resistance measurements [erratum in Applied Physics Letters 85 (16) 3638-3638

    NARCIS (Netherlands)

    Brom, H.B.; Romijn, I.G.; Magis, J.G.; van der Vleuten, M.; Michels, M.A.J.

    2004-01-01

    The aging effects around the glass and melting transitions in poly(dimethylsiloxane) were investigated. Small amounts of carbon-black (CB) particles were dispersed in a fractal network in nonconducting rubbers for monitoring the structural changes on small length scales due to aging. Long time

  13. Glass transition and the rigid amorphous phase in semicrystalline blends of bacterial polyhydroxybutyrate PHB with low molecular mass atactic R,S-PHB-diol

    NARCIS (Netherlands)

    Hoehne, G.W.H.

    2004-01-01

    The glass transition and the crystallinity of blends of isotactic bacterial PHB and low molecular mass atactic R, S-PHB-diols was investigated by means of differential scanning calorimetry (DSC), temperature-modulated DSC and dielectric spectroscopy. It was found that (i) Tg of crystallized blends

  14. Phase-glass scaling near the coherence transition in granular HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Roa-Rojas, J.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A. A. 14490, Bogota DC (Colombia); Prieto, P. [Grupo de Peliculas Delgadas, Departamento de Fisica, Universidad del Valle, A. A. 25360, Cali (Colombia)

    2005-07-01

    Systematic measurements of electrical magnetoconductivity near the coherence transition of granular HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films are reported. Experiments performed in magnetic fields ranging from 0 to 2500 Oe reveal that close to the coherence transition temperature T{sub c0}(H), the correlation length scales as a power law of temperature with a thermal-dependent critical exponent, {nu}. In low external fields the corresponding value of {nu} is consistent with the two-dimensional phase-glass model, which is in the same dynamical universality class of the so-called vortex-glass model. At applied fields H > 1000 Oe, the vortex dynamics becomes stronger and the coherence transition is not observed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. An application for impedance spectroscopy in the characterisation of the glass transition during the lyophilization cycle: the example of a 10% w/v maltodextrin solution.

    Science.gov (United States)

    Smith, Geoff; Arshad, Muhammad Sohail; Polygalov, Eugene; Ermolina, Irina

    2013-11-01

    Impedance spectroscopy has been used for the measurement of the glass transition of a 10 % maltodextrin solution contained within a glass vial, with externally attached electrodes. Features of the pseudo-relaxation process, associated with the composite impedance of the glass vial-solution assembly, were characterised by the peak amplitude, C(peak)(″), and peak frequency, f(peak), of the capacitance spectra and the equivalent circuit elements that model the impedance spectra (i.e. the solution resistance and solution capacitance) and monitored every 3 min during re-heating of the solution. The time derivatives of all four parameters studied provided a glass transition in close agreement with DSC measurements (-17 °C) and at a precision of ± 0.5 °C. The temperature dependencies of the solution resistance and peak frequency were then characterised with the Arrhenius and Vogel-Fulcher-Tammann fit functions, at temperatures below and above Tg, respectively. The energy of activation (below Tg) was estimated at ~20 kJ mol(-1), and the fragility index (If) of the glass forming liquid (above Tg) was estimated at 0.9. The significance of the fragility index to the development, optimisation and control of the freeze-drying cycle is highlighted. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Internal structure transition of spin-on glass by electron beam irradiation

    International Nuclear Information System (INIS)

    Araki, Makoto; Taniguchi, Jun; Sawada, Nobuo; Utsumi, Takayuki; Miyamoto, Iwao

    2007-01-01

    The effects of electron beam (EB) irradiation on spin-on glass (SOG) were investigated using thermal desorption spectroscopy. We were able to employ heat treatment as a 'development process', since we discovered that heat treatment breaks different bonds in SOG depending on whether it is applied before or after EB irradiation of SOG. In the case, when heat treatment was applied before EB irradiation of SOG, it was possible to break the Si-C bond at about 500 deg. C. In the case, when heat treatment was applied after EB irradiation of SOG, on the other hand, the -SiC bond could be broken at a lower temperature of about 400 deg. C. Using this difference between the two bond-breaking temperatures, it was possible to develop SOG using thermal desorption development (TDD). Moreover, the bond-breaking mechanisms revealed that the organic components in SOG play an important role in TDD. Hence, in order to determine the influence of organic components on TDD, the development characteristics of SOG samples with 10% and 15% organic contents were investigated

  17. Fragile-to-fragile liquid transition at Tg and stable-glass phase nucleation rate maximum at the Kauzmann temperature TK

    International Nuclear Information System (INIS)

    Tournier, Robert F.

    2014-01-01

    An undercooled liquid is unstable. The driving force of the glass transition at T g is a change of the undercooled-liquid Gibbs free energy. The classical Gibbs free energy change for a crystal formation is completed including an enthalpy saving. The crystal growth critical nucleus is used as a probe to observe the Laplace pressure change Δp accompanying the enthalpy change −V m ×Δp at T g where V m is the molar volume. A stable glass–liquid transition model predicts the specific heat jump of fragile liquids at T≤T g , the Kauzmann temperature T K where the liquid entropy excess with regard to crystal goes to zero, the equilibrium enthalpy between T K and T g , the maximum nucleation rate at T K of superclusters containing magic atom numbers, and the equilibrium latent heats at T g and T K . Strong-to-fragile and strong-to-strong liquid transitions at T g are also described and all their thermodynamic parameters are determined from their specific heat jumps. The existence of fragile liquids quenched in the amorphous state, which do not undergo liquid–liquid transition during heating preceding their crystallization, is predicted. Long ageing times leading to the formation at T K of a stable glass composed of superclusters containing up to 147 atom, touching and interpenetrating, are evaluated from nucleation rates. A fragile-to-fragile liquid transition occurs at T g without stable-glass formation while a strong glass is stable after transition

  18. On the glass transition of the one-component metallic melts

    Czech Academy of Sciences Publication Activity Database

    Fedorchenko, Alexander I.

    2017-01-01

    Roč. 475, October (2017), s. 362-367 ISSN 0022-0248 Institutional support: RVO:61388998 Keywords : equilibrium and non-equilibrium solidification * criterion of the phase transition scenario * one-component metal melts Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 1.751, year: 2016 http://ac.els-cdn.com/S0022024817304281/1-s2.0-S0022024817304281-main.pdf?_tid=a12ba97e-873b-11e7-b6be-00000aacb35e&acdnat=1503407763_5cdbcdb15d504baf5f8dfb94886b3100

  19. Impulsive Stimulated Light Scattering Studies of the Liquid-Glass Transition: on the Experimental Verification of Mode-Coupling Theory Predictions.

    Science.gov (United States)

    Halalay, Ion C.

    A study of the structural glass transition trough impulsive stimulated light scattering experiments has been carried out in concentrated aqueous lithium chloride solutions, at temperatures ranging from ambient to cryogenic. A specially designed sample cell made it possible to cover the whole temperature interval from simple liquid, to viscoelastic supercooled liquid, to glass. It is shown that a phenomenological description of the results of these experiments in terms of a spectrum of relaxation times through the use of a Kohlrausch-Williams-Watts relaxation function is inadequate. Based on predictions of mode-coupling theory of the liquid-glass transition, an alternative approach to data interpretation is proposed. It is shown that for an aqueous lithium chloride solution, the prediction of simple scaling and identical scaling for mechanical and electrical susceptibilities seems to be valid. However, another prediction of theory is called into question: instead of a power-law behavior on temperature difference, it is found experimentally that the behavior of the susceptibility spectrum minimum is exponential. Similar disagreements are found for other two materials, triphenyl phosphite and polypropylene oxide. The causes for these discrepancies are discussed and it is concluded that additional experimentation is necessary to verify theoretical claims. Experiments are proposed which can test these predictions and serve as guide for the construction of theoretical models for the glass transition in real systems. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

  20. Structure, glass transition temperature and spectroscopic properties of 10Li2O-xP2O5-(89-x)TeO2-1CuO (5≤x≤25 mol%) glass system.

    Science.gov (United States)

    Upender, G; Babu, J Chinna; Mouli, V Chandra

    2012-04-01

    X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), infrared (IR), Raman, electron paramagnetic resonance (EPR) and optical absorption studies on 10Li2O-xP2O5-(89-x)TeO2-1CuO glasses (where x=5, 10, 15, 20 and 25 mol%) have been carried out. The amorphous nature of the glasses was confirmed using XRD and FESEM measurements. The glass transition temperature (Tg) of glass samples have been estimated from DSC traces and found that the Tg increases with increasing P2O5 content. Both the IR and Raman studies have been showed that the present glass system consists of [TeO3], [TeO4], [PO3] and [PO4] units. The spin-Hamiltonian parameters such as g∥, g⊥, and A∥ have been determined from EPR spectra and it was found that the Cu2+ ion is present in tetragonal distorted octahedral site with [Formula: see text] as the ground state. Bonding parameters and bonding symmetry of Cu2+ ions have been calculated by correlating EPR and optical data and were found to be composition dependent. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. A cavitation transition in the energy landscape of simple cohesive liquids and glasses

    International Nuclear Information System (INIS)

    Altabet, Y. Elia; Debenedetti, Pablo G.; Stillinger, Frank H.

    2016-01-01

    In particle systems with cohesive interactions, the pressure-density relationship of the mechanically stable inherent structures sampled along a liquid isotherm (i.e., the equation of state of an energy landscape) will display a minimum at the Sastry density ρ S . The tensile limit at ρ S is due to cavitation that occurs upon energy minimization, and previous characterizations of this behavior suggested that ρ S is a spinodal-like limit that separates all homogeneous and fractured inherent structures. Here, we revisit the phenomenology of Sastry behavior and find that it is subject to considerable finite-size effects, and the development of the inherent structure equation of state with system size is consistent with the finite-size rounding of an athermal phase transition. What appears to be a continuous spinodal-like point at finite system sizes becomes discontinuous in the thermodynamic limit, indicating behavior akin to a phase transition. We also study cavitation in glassy packings subjected to athermal expansion. Many individual expansion trajectories averaged together produce a smooth equation of state, which we find also exhibits features of finite-size rounding, and the examples studied in this work give rise to a larger limiting tension than for the corresponding landscape equation of state.

  2. Deformation and structure evolution of glassy poly(lactic acid) below the glass transition temperature

    DEFF Research Database (Denmark)

    Zhou, Chengbo; Li, Hongfei; Zhang, Yao

    2015-01-01

    , the onset of the mesocrystal formation is delayed to a higher strain value, whereas corresponding to the same critical orientation degree of amorphous chains (f(am) approximate to 0.45). The DSC results indicated that the post-T-g endothermic peak corresponding to the melting of mesocrystal appears...... and shifts to a higher temperature with increasing stretching temperature, followed by the down-shifts (to a lower temperature) of the exothermic peak of cold crystallization of PLA. The appearance of a small exothermic peak just before the melting peak related to the transition of the alpha' to alpha...... crystal implies the formation of an alpha' crystal during cold crystallization in the drawn PLA samples. The structure evolution of glassy PLA stretched below T-g was discussed in details....

  3. Contrasting dynamics of fragile and non-fragile polyalcohols through the glass, and dynamical, transitions: A comparison of neutron scattering and dielectric relaxation data for sorbitol and glycerol.

    Science.gov (United States)

    Migliardo, F; Angell, C A; Magazù, S

    2017-01-01

    Glycerol and sorbitol are glass-forming hydrogen-bonded systems characterized by intriguing properties which make these systems very interesting also from the applications point of view. The goal of this work is to relate the hydrogen-bonded features, relaxation dynamics, glass transition properties and fragility of these systems, in particular to seek insight into their very different liquid fragilities. The comparison between glycerol and sorbitol is carried out by collecting the elastic incoherent neutron scattering (EINS) intensity as a function of temperature and of the instrumental energy resolution. Intensity data vs temperature and resolution are analyzed in terms of thermal restraint and Resolution Elastic Neutron Scattering (RENS) approaches. The number of OH groups, which are related to the connecting sites, is a significant parameter both in the glass transition and in the dynamical transition. On the other hand, the disordered nature of sorbitol is confirmed by the existence of different relaxation processes. From the applications point of view, glycerol and sorbitol have remarkable bioprotectant properties which make these systems useful in different technological and industrial fields. Furthermore, polyols are rich in glassforming liquid phenomenology and highly deserving of study in their own right. The comparison of EINS and calorimetric data on glycerol and sorbitol helps provide a connection between structural relaxation, dynamical transition, glass transition, and fragility. The evaluation of the inflection point in the elastic intensity behavior as a function of temperature and instrumental energy resolution provides a confirmation of the validity of the RENS approach. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo. Copyright © 2016. Published by Elsevier B.V.

  4. The far infrared radiation characteristics for Li2O.Al2O3.4SiO2(LAS) glass-ceramics and transition-metal oxide

    International Nuclear Information System (INIS)

    Huh, Nam Jung; Yang, Joong Sik

    1991-01-01

    The far infrared radiation characteristic for Li 2 O.Al 2 O 3 .4SiO 2 (LAS) glass, the LAS glass-ceramic and sintered transition metal oxides such as CuO, Fe 2 O 3 and Co 3 O 4 , were investigated. LAS glass and LAS glass-ceramic was higher than that of the LAS glass. Heat-treated CuO and Co 3 o 4 had radiation characteristic of high efficiency infrared radiant, and heat-treated Fe 2 O 3 had radiation characteristic that infrared emissivity decreased in higher was length above 15μm. (Author)

  5. Protein Internal Dynamics Associated With Pre-System Glass Transition Temperature Endothermic Events: Investigation of Insulin and Human Growth Hormone by Solid State Hydrogen/Deuterium Exchange.

    Science.gov (United States)

    Fang, Rui; Grobelny, Pawel J; Bogner, Robin H; Pikal, Michael J

    2016-11-01

    Lyophilized proteins are generally stored below their glass transition temperature (T g ) to maintain long-term stability. Some proteins in the (pure) solid state showed a distinct endotherm at a temperature well below the glass transition, designated as a pre-T g endotherm. The pre-T g endothermic event has been linked with a transition in protein internal mobility. The aim of this study was to investigate the internal dynamics of 2 proteins, insulin and human growth hormone (hGH), both of which exhibit the pre-T g endothermic event with onsets at 50°C-60°C. Solid state hydrogen/deuterium (H/D) exchange of both proteins was characterized by Fourier transform infrared spectroscopy over a temperature range from 30°C to 80°C. A distinct sigmoidal transition in the extent of H/D exchange had a midpoint of 56.1 ± 1.2°C for insulin and 61.7 ± 0.9°C for hGH, suggesting a transition to greater mobility in the protein molecules at these temperatures. The data support the hypothesis that the pre-T g event is related to a transition in internal protein mobility associated with the protein dynamical temperature. Exceeding the protein dynamical temperature is expected to activate protein internal motion and therefore may have stability consequences. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  6. Doping influence by some transition elements on the irradiation effects in nuclear waste glasses; Influence du dopage par certains elements de transition sur les effets d'irradiation dans des verres d'interet nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Florent, Olivier

    2006-06-15

    High-level waste glasses are submitted to auto-irradiation. Modelling it using external irradiations on simple glasses revealed defects production and non negligible structural changes. This thesis aims at determining the impact of a more complex composition on these effects, especially the influence of adding polyvalent transition metals. Silicate, soda-lime and alumino-borosilicate glasses are doped with different iron, chromium and manganese concentrations then {beta} irradiated at different doses up to 10{sup 9} Gy. Non doped glasses show an increase of their density and polymerisation coupled with a molecular oxygen and point defects production. Adding 0.16 mol% Fe decreases the amount of defects by 85 % and all irradiation effects. A Fe{sup 3+} reduction is also observed by EPR, optical absorption and indirectly by Raman spectroscopy. A higher than 0.32 mol% Fe concentration causes complete blockage of the evolution of polymerisation, density and defect production. The same results are obtained on chromium or manganese doped glasses. An original in situ optical absorption device shows the quick decrease of Fe{sup 3+} amount to a 25 % lower level during irradiation. Stopping irradiation causes a lower decrease of 65 %, suggesting a dynamic (h{sup 0}/e-) consuming equilibrium. He{sup +} and Kr{sup 3+} ions and {gamma} irradiated glasses tend to confirm these phenomena for all kind of irradiation with electronic excitations. (author)

  7. Effect of borojo (Borojoa patinoi Cuatrecasas) three-phase composition and gum arabic on the glass transition temperature.

    Science.gov (United States)

    Rodríguez-Bernal, Jenny M; Tello, Edisson; Flores-Andrade, Enrique; Perea-Flores, Maria de Jesús; Vallejo-Cardona, Alba A; Gutiérrez-López, Gustavo F; Quintanilla-Carvajal, Maria X

    2016-02-01

    The search for natural, novel, high-quality, stable food ingredients is an ongoing practice in the food industry. Pulp of borojo (Borojoa patinoi Cuatrecasas), which is a fruit of the Colombian Pacific region, can be separated into three phases: liquid (LP), medium (MP) and solid (SP) phases. The objective of this work was to evaluate the effect of the three-phase composition and gum arabic on their glass transitions temperatures (T(g)). The best mixture, LP-MP, MP-SP and LP-SP and gum arabic (GA) was identified by response surface methodology. When adding GA to SP borojo phase in a 1:1 proportion, the resulting T(g) of the mixture was 132.27 °C whereas Tg for GA and SP-phase were 154.89 °C and 79.86 °C respectively, which supported this combination as attractive from a processing perspective and supports an industrial advantage of using borojo as food ingredient. Phases were characterized by high-performance liquid chromatography, Fourier transform infrared spectroscopy, confocal laser scanning microscopy and mass spectrometry. Low molecular weight compounds such as fructose for MP lowered T(g) whereas the presence of lignin increased T(g) of the mixtures as with the SP. The addition of GA significantly increased T(g) of borojo phases so leading to propose them as novel food processing materials. © 2015 Society of Chemical Industry.

  8. Glass-like dynamics of the strain-induced coil/helix transition on a permanent polymer network.

    Science.gov (United States)

    Ronsin, O; Caroli, C; Baumberger, T

    2016-02-14

    We study the stress response to a step strain of covalently bonded gelatin gels in the temperature range where triple helix reversible crosslink formation is prohibited. We observe slow stress relaxation towards a T-dependent finite asymptotic level. We show that this is assignable to the strain-induced coil → helix transition, previously evidenced by Courty et al. [Proc. Natl. Acad. Sci. U. S. A. 102, 13457 (2005)], of a fraction of the polymer strands. Relaxation proceeds, in a first stage, according to a stretched exponential dynamics, then crosses over to a terminal simple exponential decay. The respective characteristic times τK and τf exhibit an Arrhenius-like T-dependence with an associated energy E incompatibly larger than the activation barrier height for the isomerisation process which sets the clock for an elementary coil → helix transformation event. We tentatively assign this glass-like slowing down of the dynamics to the long-range couplings due to the mechanical noise generated by the local elementary events in this random elastic medium.

  9. Effect of hydrolyzed whey protein on surface morphology, water sorption, and glass transition temperature of a model infant formula.

    Science.gov (United States)

    Kelly, Grace M; O'Mahony, James A; Kelly, Alan L; O'Callaghan, Donal J

    2016-09-01

    Physical properties of spray-dried dairy powders depend on their composition and physical characteristics. This study investigated the effect of hydrolyzed whey protein on the microstructure and physical stability of dried model infant formula. Model infant formulas were produced containing either intact (DH 0) or hydrolyzed (DH 12) whey protein, where DH=degree of hydrolysis (%). Before spray drying, apparent viscosities of liquid feeds (at 55°C) at a shear rate of 500 s(-1) were 3.02 and 3.85 mPa·s for intact and hydrolyzed infant formulas, respectively. On reconstitution, powders with hydrolyzed whey protein had a significantly higher fat globule size and lower emulsion stability than intact whey protein powder. Lactose crystallization in powders occurred at higher relative humidity for hydrolyzed formula. The Guggenheim-Anderson-de Boer equation, fitted to sorption isotherms, showed increased monolayer moisture when intact protein was present. As expected, glass transition decreased significantly with increasing water content. Partial hydrolysis of whey protein in model infant formula resulted in altered powder particle surface morphology, lactose crystallization properties, and storage stability. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  10. Confinement and the Glass Transition Temperature in Supported Polymer Films: Molecular Weight, Repeat Unit Modification, and Cooperativity Length Scale Investigations

    Science.gov (United States)

    Mundra, Manish K.

    2005-03-01

    It is well known that the glass transition temperatures, Tgs, of supported polystyrene (PS) films decrease dramatically with decreasing film thickness below 60-80 nm. However, a detailed understanding of the cause of this effect is lacking. We have investigated the impact of several parameters, including polymer molecular weight (MW), repeat unit structure, and the length scale of cooperatively rearranging regions in bulk. There is no significant effect of PS MW on the Tg-confinement effect over a range of 5,000 to 3,000,000 g/mol. In contrast, the strength of the Tg reduction and the onset of the confinement effect increase dramatically upon changing the polymer from PS to poly(4-tert-butylstyrene) (PTBS), with PTBS exhibiting a Tg reduction relative to bulk at a thickness of 300-400 nm. PTBS also shows a Tg reduction relative to bulk of 47 K in a 21-nm-thick film, more than twice that observed in a PS film of identical thickness. Characterization of the length scale of cooperatively rearranging regions has been done by differential scanning calorimetry but reveals at best a limited correlation with the confinement effect.

  11. Fabrication of (PPC/NCC)/PVA composites with inner-outer double constrained structure and improved glass transition temperature.

    Science.gov (United States)

    Cui, Shaoying; Li, Li; Wang, Qi

    2018-07-01

    Improving glass transition temperature (T g ) and mechanical property of the environment-friendly poly(propylene carbonate) via intermacromolecular complexation through hydrogen bonding is attractive and of great importance. A novel and effective strategy to prepare (polypropylene carbonate/nanocrystalline cellulose)/polyvinyl alcohol ((PPC/NCC)/PVA) composites with inner-outer double constrained structure was reported in this work. Outside the PPC phase, PVA, as a strong skeleton at microscale, could constrain the movement of PPC molecular chains by forming hydrogen bonding with PPC at the interface of PPC and PVA phases; inside the PPC phase, the rod-like NCC could restrain the flexible molecular chains of PPC at nanoscale by forming multi-hydrogen bonding with PPC. Under the synergistic effect of this novel inner-outer double constrained structure, T g , mechanical properties and thermal stability of (PPC/NCC)/PVA composite were significantly increased, e.g. T g of the composite researched the maximum value of 49.6 °C, respectively 15.6 °C, 5.7 °C and 4.2 °C higher than that of PPC, PPC/NCC and PPC/PVA composite. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

    Science.gov (United States)

    Eloi, J-C; Okuda, M; Jones, S E Ward; Schwarzacher, W

    2013-06-18

    For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  13. Structural characterization of tellurite glasses doped with transition metal oxides using Raman spectra and ab initio calculations.

    Science.gov (United States)

    Mohamed, Tarek A; Shaltout, I; Al Yahyaei, K M

    2006-05-01

    Systems of iron tellurite glasses were prepared by melt quenching with compositions of [85%TeO2+5%Fe2O3+10%TMO], where transition metal oxides (TMO) are TiO2, V2O5, MnO, CoO, NiO and CuO. Furthermore, the main structural units of these samples have been characterized by means of Raman spectra (150-1200 cm(-1)) as well as wavenumber predictions by means of Gaussian 98 ab initio calculations for the proposed site symmetries of TeO4(4-) triagonal bipyramid (C2v) and Te2O7(6-) bridged tetrahedra (Cs and C1). Aided by normal coordinate analysis, calculated vibrational frequencies, Raman scattering activities, force constants in internal coordinates and potential energy distributions (PEDs), revised vibrational assignments for the fundamental modes have been proposed. The main structural features are correlated to the dominant units of triagonal bipyramid (tbp) or bridged tetrahedral (TeO3+1 binds to TeO3 through TeOTe bridge; corner sharing). Moreover, the Raman spectra of the investigated tellurites reflect a structural change from tbp (coordination number is four) to triagonal pyramidal (coordination number is three).

  14. Reformulation of time-convolutionless mode-coupling theory near the glass transition

    Science.gov (United States)

    Tokuyama, Michio

    2017-10-01

    The time-convolutionless mode-coupling theory (TMCT) recently proposed is reformulated under the condition that one of two approximations, which have been used to formulate the original TMCT in addition to the MCT approximations done on a derivation of nonlinear memory function in terms of the intermediate-scattering function, is not employed because it causes unphysical results for intermediate times. The improved TMCT equation is then derived consistently under another approximation. It is first checked that the ergodic to non-ergodic transition obtained by a new equation is exactly the same as that obtained by an old one because the long-time dynamics of both equations coincides with each other. However, it is emphasized that a difference between them appears in the intermediate-time dynamics of physical quantities. Such a difference is explored numerically in the dynamics of a non-Gaussian parameter by employing the Percus-Yevick static structure factor to calculate the nonlinear memory function.

  15. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with γ-Alumina Nanoparticles

    Science.gov (United States)

    Diez-Berart, Sergio; López, David O.; Salud, Josep; Diego, José Antonio; Sellarès, Jordi; Robles-Hernández, Beatriz; de la Fuente, María Rosario; Ros, María Blanca

    2015-01-01

    In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  16. Effect of silica and water content on the glass transition of poly(ethylene glycol) monomethylether-silica gel-lithium perchlorate ormolytes

    International Nuclear Information System (INIS)

    Korwin, Rebecca S.; Masui, Hitoshi

    2005-01-01

    The effect of silica and water content on the glass transition temperature, T g , of MPEG2000-silica-LiClO 4 ormolytes was assessed by differential scanning calorimetry (DSC). The sol-gel synthesized ormolytes consisted of various amounts of poly(ethylene glycol) monomethylether (M.W. 2000 g/mol; i.e., MPEG2000) tethered to silica gel through the hydroxyl terminus via a urethane linkage. DSC features corresponding to physisorbed and hydrogen-bonded water, as well as the glass transition of the polyether, were identified. Both silica and LiClO 4 raise the T g and suppress crystallization of the polyether component. Water plasticizes the polyether and stoichiometrically solvates and sequesters Li + , thereby, lowering T g

  17. Spin glass transition in the rhombohedral LiNi1/3Mn1/3Co1/3O2

    International Nuclear Information System (INIS)

    Bie, Xiaofei; Yang, Xu; Han, Bing; Chen, Nan; Liu, Lina; Wei, Yingjin; Wang, Chunzhong; Chen, Hong; Du, Fei; Chen, Gang

    2013-01-01

    Highlights: •The Rietveld analysis of XRD data reveals a single phase with rhombohedral structure. •Dc susceptibility data suggest a spin glass behavior at low T in the 333 compound. •The ac susceptibility measurements have been observed in the typical SG system. •Three models have been employed to study the behavior of the spin glass state. •Both geometrical frustration and disorder play important role in the formation of SG. -- Abstract: Layered LiNi 1/3 Mn 1/3 Co 1/3 O 2 has been synthesized by co-precipitation method, and the magnetic properties were comprehensively studied by dc and ac susceptibilities. The dc magnetization curves show the irreversibility and spin freezing behavior at 109 K and 9 K. The evolution of real and imaginary part of ac susceptibility under different frequencies indicates a spin glass transition at low temperature. Three models (the Néel–Arrhenius law, the Vogel–Fulcher law, and the power law) have been employed to study the relaxation behavior of the spin glass state. Both frustration and disorder play important role in the formation of spin glass

  18. Effects of molecular weight on the glass transition temperature in Durolon polycarbonate; Os efeitos da massa molecular sobre a temperatura de transicao vitrea (Tg) para o policarbonato Durolon

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Adelina; Sciani, Valdir [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1995-12-31

    The effect of variation of the dose rate on degradation mechanism of PC Durolon irradiated with gamma rays was determined trough out intrinsic viscosity and thermal analysis of DSC-type measurements. The results showed a linear relationship between the glass transition temperature and the viscosimetric average molecular weight. From the results it`s shown that with an increased of the dose rate it also increases the degradation of the material. (author). 12 refs., 3 figs.

  19. Frequency-dependent complex modulus at the glass transition in Pd40Ni10Cu30P20 bulk amorphous alloys

    International Nuclear Information System (INIS)

    Lee, M.L.; Li, Y.; Feng, Y.P.; Carter, W.C.

    2003-01-01

    We report frequency-dependent measurements of the dynamic elastic modulus of a Pd 40 Cu 30 Ni 10 P 20 bulk amorphous phase near its glass transition temperature. The storage and loss moduli exhibit a structural relaxation similar to those observed by other characterization techniques. Parameters obtained by fitting to the Vogel-Fulcher-Tamman equation and the Kohlrausch-Williams-Watts model exhibit similar behaviors to those other methods

  20. The effect of polymeric excipients on the physical properties and performance of amorphous dispersions: Part I, free volume and glass transition.

    Science.gov (United States)

    Li, Jinjiang; Zhao, Junshu; Tao, Li; Wang, Jennifer; Waknis, Vrushali; Pan, Duohai; Hubert, Mario; Raghavan, Krishnaswamy; Patel, Jatin

    2015-02-01

    To investigate the structural effect of polymeric excipients on the behavior of free volume of drug-polymer dispersions in relation to glass transition. Two drugs (indomethacin and ketoconazole) were selected to prepare amorphous dispersions with PVP, PVPVA, HPC, and HPMCAS through spray drying. The physical attributes of the dispersions were characterized using SEM and PXRD. The free volume (hole-size) of the dispersions along with drugs and polymers was measured using positron annihilation lifetime spectroscopy (PALS). Their glass transition temperatures (Tgs) were determined using DSC and DMA. FTIR spectra were recorded to identify hydrogen bonding in the dispersions. The chain structural difference-flexible (PVP and PVPVA) vs. inflexible (HPC and HPMCAS)-significantly impacts the free volume and Tgs of the dispersions as well as their deviation from ideality. Relative to Tg, free volume seems to be a better measure of hydrogen bonding interaction for the dispersions of PVP, HPC, and HPMCAS. The free volume of polymers and their dispersions in general appears to be related to their conformations in solution. Both the backbone chain rigidity of polymers as well as drug-polymer interaction can impact the free volume and glass transition behaviors of the dispersions.

  1. Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

    Science.gov (United States)

    Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

    2015-01-01

    Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers.

  2. Temporal Texture Profile and Identification of Glass Transition Temperature as an Instrumental Predictor of Stickiness in a Caramel System.

    Science.gov (United States)

    Mayhew, Emily J; Schmidt, Shelly J; Schlich, Pascal; Lee, Soo-Yeun

    2017-09-01

    Stickiness is an important texture attribute in many food systems, but its meaning can vary by person, product, and throughout mastication. This variability and complexity makes it difficult to devise analytical tests that accurately and consistently predict sensory stickiness. Glass transition temperature (T g ) is a promising candidate for texture prediction. Our objective is to elucidate the temporal profile of stickiness in order to probe the relationship between T g and dynamic stickiness perception. Nine caramel samples with diverse texture and thermal profiles were produced for sensory testing and differential scanning calorimetry. Sixteen trained panelists generated stickiness-relevant terms to be used in a subsequent temporal dominance of sensation (TDS) test with the same panelists. Following the TDS study, these panelists also rated samples for overall tactile and oral stickiness. Stickiness ratings were then correlated to TDS dominance parameters across the full evaluation period and within the first, middle, and final thirds of the evaluation period. Samples with temporal texture profiles dominated by tacky, stringy, and enveloping attributes consistently received the highest stickiness scores, although the correlation strength varied by time period. T g was found to correlate well with trained panelist and consumer ratings of oral (R 2 trained = 0.85; R 2 consumer = 0.96) and tactile (R 2 trained = 0.78; R 2 consumer = 0.79) stickiness intensity, and stickiness intensity ratings decreased with T g of completely amorphous samples. Further, glassy samples followed a different texture trajectory (brittle-cohesive-toothpacking) than rubbery samples (deformable-tacky-enveloping). These results illuminate the dynamic perception of stickiness and support the potential of T g to predict both stickiness intensity and texture trajectory in caramel systems. © 2017 Institute of Food Technologists®.

  3. Transition from Arrhenius to non-Arrhenius temperature dependence of structural relaxation time in glass-forming liquids: continuous versus discontinuous scenario.

    Science.gov (United States)

    Popova, V A; Surovtsev, N V

    2014-09-01

    The temperature dependences of α relaxation time τ(α)(T) of three glass-forming liquids (salol, o-terphenyl, and α-picoline) were investigated by a depolarized light scattering technique. A detailed description of τ(α)(T) near T(A), the temperature of the transition from the Arrhenius law at high temperatures to a non-Arrhenius behavior of τ(α)(T) at lower temperatures, was done. It was found that this transition is quite sharp. If the transition is described as switching from the Arrhenius law to the Vogel-Fulcher-Tammann law, it occurs within the temperature range of about 15 K or less. Most of the known expressions for τ(α)(T) cannot describe this sharp transition. Our analysis revealed that this transition can be described either as a discontinuous transition in the spirit of the frustration-limited domain theory [D. Kivelson, G. Tarjus, X. Zhao, and S. A. Kivelson, Phys. Rev. E 53, 751 (1996)], implying a phase transition, or by a phenomenological expression recently suggested [B. Schmidtke, N. Petzold, R. Kahlau, M. Hofmann, and E. A. Rössler, Phys. Rev. E 86, 041507 (2012)], where the activation energy includes the term depending exponentially on temperature.

  4. Mix proportions and properties of CLSC made from thin film transition liquid crystal display optical waste glass.

    Science.gov (United States)

    Wang, Her-Yung; Chen, Jyun-Sheng

    2010-01-01

    In this study, controlled low-strength concrete (CLSC) is mixed using different water-to-binder (W/B) ratios (1.1, 1.3 and 1.5) and various percentages of sand substituted by waste LCD glass sand (0%, 10%, 20% and 30%). The properties of the fresh concrete, including compressive strength, electrical resistivity, ultrasonic pulse velocity, permeability ratio and shrinking of the CLSC, are examined. Results show that increases in amount of waste glass added result in better slump and slump flow, longer initial setting time and smaller unit weight. Compressive strength decreases with increasing W/B ratio and greater amounts of waste glass added. Both electrical resistivity and ultrasonic pulse velocity increase with increases in amount of waste glass and decreases in W/B ratio. On the contrary, the permeability ratio increases with increases in W/B ratio, but decreases with greater amounts of waste glass added. CLSC specimens cured for different durations show little changes in length with shrinkage below 0.025%. Our findings reveal that CLSC mixed using waste LCD glass in place of sand can meet design requirements. Recycling of waste LCD glass not only offers an economical substitute for aggregates, but also an ecological alternative for waste management. 2009 Elsevier Ltd. All rights reserved.

  5. Solvent-induced crystallization for hybrid perovskite thin-film photodetector with high-performance and low working voltage

    International Nuclear Information System (INIS)

    Hu, Wei; Yang, Shuzhen; Fan, Peng; Pan, Anlian; Wu, Runsheng; Yang, Junliang

    2017-01-01

    Organometal trihalide perovskites have emerged as a class of solution-processed semiconductors exhibiting remarkable optoelectronic properties. Using a high-quality perovskite thin film prepared by solvent-induced crystallization method and adopting a novel device configuration based on photon recycling effect, a perovskite thin-film photodetector has been constructed with the highest external quantum efficiency of 4.1  ×  10 4 % and responsivity of 219 A W −1 at a low bias of 1 V so far. The device working mechanism was further disclosed based on energy band bending model. The high-performance and low working-voltage perovskite thin-film photodetector will find potential applications in photodetection and optoelectronic integrated circuits. (paper)

  6. Thermostimulated transitions of radiation colour centers in fiber light guides on the base of pure quartz glass

    International Nuclear Information System (INIS)

    Abramov, A.V.; Dianov, E.M.; Karpechev, V.N.; Kornienko, L.S.; Rybaltovskij, A.O.; Chernov, P.V.

    1987-01-01

    Study on properties and characteristics of induced absorption (IA) in glass fiber light guides (GFLG) with a pure quartz glass core is continued. Effect of thermal-stimulated construction of colour radiation centers (CRC) giving induced absorption bands at 670, 550, and 380 nm has been detected. Effective temperatures of these IA band annealings have been determined as well as bands at 340 nm and induced absorption IR edge. Positions of IA band halfwidths and maxima on the assumption that IA bands have the Gauss form. It is assumed that CRC photo- and thermostimulated construction may occur with participation of physically dissolved in a glass grid gases or their radiolysis products

  7. Relaxations in spin glasses: Similarities and differences from ordinary glasses

    International Nuclear Information System (INIS)

    Ngai, K.L.; Rajagopal, A.K.; Huang, C.Y.

    1984-01-01

    Relaxation phenomena have become a major concern in the physics of spin glasses. There are certain resemblances of these relaxation properties to those of ordinary glasses. In this work, we compare the relaxation properties of spin glasses near the freezing temperature with those of glasses near the glass transition temperature. There are similarities between the two types of glasses. Moreover, the relaxation properties of many glasses and spin glasses are in conformity with two coupled ''universality'' relations predicted by a recent model of relaxations in condensed matter

  8. Infrequent blue and green emission transitions from Eu3+ in heavy metal tellurite glasses with low phonon energy

    International Nuclear Information System (INIS)

    Lin, H.; Tanabe, S.; Lin, L.; Yang, D.L.; Liu, K.; Wong, W.H.; Yu, J.Y.; Pun, E.Y.B.

    2006-01-01

    Eu 3+ doped alkali-barium-bismuth-tellurite (Eu 3+ :LKBBT) glasses were prepared by conventional melt quenching. Twelve emission bands including infrequent blue and green bands are observed and they almost cover whole visible spectral region under violet light radiation. The blue and green emissions of Eu 3+ rarely appeared in oxide glasses before, but they have been clearly recorded in Eu 3+ :LKBBT glasses even in the case of high concentration doping of Eu 3+ . The analysis based on spontaneous-radiative rate, energy gap and Raman scattering reveals that the obtaining of the abundant multichannel emissions of Eu 3+ is due to the higher refractive index and the lower phonon energy in LKBBT glass system

  9. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation.

    Science.gov (United States)

    Starr, Francis W; Douglas, Jack F; Sastry, Srikanth

    2013-03-28

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

  10. Optical properties of alkaline earth borate glasses

    African Journals Online (AJOL)

    user

    The alkaline earth borate glasses containing heavy metal oxides show good solubility of rare-earth ions. Glasses containing PbO exhibit low glass transition temperature (Tg) and high ..... These oxygen ions carry a partial negative charge and.

  11. Distinctly Different Glass Transition Behaviors of Trehalose Mixed with Na2HPO 4 or NaH 2PO 4: Evidence for its Molecular Origin.

    Science.gov (United States)

    Weng, Lindong; Elliott, Gloria D

    2015-07-01

    The present study is aimed at understanding how the interactions between sugar molecules and phosphate ions affect the glass transition temperature of their mixtures, and the implications for pharmaceutical formulations. The glass transition temperature (Tg) and the α-relaxation temperature (Tα) of dehydrated trehalose/sodium phosphate mixtures (monobasic or dibasic) were determined by differential scanning calorimetry and dynamic mechanical analysis, respectively. Molecular dynamics simulations were also conducted to investigate the microscopic interactions between sugar molecules and phosphate ions. The hydrogen-bonding characteristics and the self-aggregation features of these mixtures were quantified and compared. Thermal analysis measurements demonstrated that the addition of NaH2PO4 decreased both the glass transition temperature and the α-relaxation temperature of the dehydrated trehalose/NaH2PO4 mixture compared to trehalose alone while both Tg and Tα were increased by adding Na2HPO4 to pure trehalose. The hydrogen-bonding interactions between trehalose and HPO4(2-) were found to be stronger than both the trehalose-trehalose hydrogen bonds and those formed between trehalose and H2PO4(-). The HPO4(2-) ions also aggregated into smaller clusters than H2PO4(-) ions. The trehalose/Na2HPO4 mixture yielded a higher T g than pure trehalose because marginally self-aggregated HPO4(2-) ions established a strengthened hydrogen-bonding network with trehalose molecules. In contrast H2PO4(-) ions served only as plasticizers, resulting in a lower Tg of the mixtures than trehalose alone, creating large-sized ionic pockets, weakening interactions, and disrupting the original hydrogen-bonding network amongst trehalose molecules.

  12. Solubility of crystalline organic compounds in high and low molecular weight amorphous matrices above and below the glass transition by zero enthalpy extrapolation.

    Science.gov (United States)

    Amharar, Youness; Curtin, Vincent; Gallagher, Kieran H; Healy, Anne Marie

    2014-09-10

    Pharmaceutical applications which require knowledge of the solubility of a crystalline compound in an amorphous matrix are abundant in the literature. Several methods that allow the determination of such data have been reported, but so far have only been applicable to amorphous polymers above the glass transition of the resulting composites. The current work presents, for the first time, a reliable method for the determination of the solubility of crystalline pharmaceutical compounds in high and low molecular weight amorphous matrices at the glass transition and at room temperature (i.e. below the glass transition temperature), respectively. The solubilities of mannitol and indomethacin in polyvinyl pyrrolidone (PVP) K15 and PVP K25, respectively were measured at different temperatures. Mixtures of undissolved crystalline solute and saturated amorphous phase were obtained by annealing at a given temperature. The solubility at this temperature was then obtained by measuring the melting enthalpy of the crystalline phase, plotting it as a function of composition and extrapolating to zero enthalpy. This new method yielded results in accordance with the predictions reported in the literature. The method was also adapted for the measurement of the solubility of crystalline low molecular weight excipients in amorphous active pharmaceutical ingredients (APIs). The solubility of mannitol, glutaric acid and adipic acid in both indomethacin and sulfadimidine was experimentally determined and successfully compared with the difference between their respective calculated Hildebrand solubility parameters. As expected from the calculations, the dicarboxylic acids exhibited a high solubility in both amorphous indomethacin and sulfadimidine, whereas mannitol was almost insoluble in the same amorphous phases at room temperature. This work constitutes the first report of the methodology for determining an experimentally measured solubility for a low molecular weight crystalline solute

  13. Long-Term Stability of New Co-Amorphous Drug Binary Systems: Study of Glass Transitions as a Function of Composition and Shelf Time

    Directory of Open Access Journals (Sweden)

    Luz María Martínez

    2016-12-01

    Full Text Available The amorphous state is of particular interest in the pharmaceutical industry due to the higher solubility that amorphous active pharmaceutical ingredients show compared to their respective crystalline forms. Due to their thermodynamic instability, drugs in the amorphous state tend to recrystallize; in order to avoid crystallization, it has been a common strategy to add a second component to hinder the crystalline state and form a thermally stable co-amorphous system, that is to say, an amorphous binary system which retains its amorphous structure. The second component can be a small molecule excipient (such as a sugar or an aminoacid or a second drug, with the advantage that a second active pharmaceutical ingredient could be used for complementary or combined therapeutic purposes. In most cases, the compositions studied are limited to 1:1, 2:1 and 1:2 molar ratios, leaving a gap of information about phase transitions and stability on the amorphous state in a wider range of compositions. In the present work, a study of novel co–amorphous formulations in which the selection of the active pharmaceutical ingredients was made according to the therapeutic effect is presented. Resistance against crystallization and behavior of glass transition temperature ( T g were studied through calorimetric measurements as a function of composition and shelf time. It was found that binary formulations with T g temperatures higher than those of pure components presented long-term thermal stability. In addition, significant increments of T g values, of as much as 15 ∘ C, were detected as a result of glass relaxation at room temperature during storage time; this behavior of glass transition has not been previously reported for co-amorphous drugs. Based on these results, it can be concluded that monitoring behavior of T g and relaxation processes during the first weeks of storage leads to a more objective evaluation of the thermomechanical stability of an amorphous

  14. Three-dimensional superconductivity and vortex glass transition in La1.87Y0.13CuO4

    International Nuclear Information System (INIS)

    Lee, Hyun-Sook; Kim, Heon-Jung; Kim, Hyun-Jung; Jung, Myung-Hwa; Jo, Younghun; Lee, Sung-Ik; Tsukada, Akio; Naito, Michio

    2006-01-01

    The angular dependence of the critical current density (J c (θ)) and the vortex glass transition temperature (T g (θ)) in La 1.87 Y 0.13 CuO 4 were measured at different fields and temperatures. Both J c (θ) and T g (θ) showed a strong angular variation, which is typical for anisotropic superconductors. The angular variation could be described by using the anisotropic three-dimensional Ginzburg-Landau theory. From our analysis, we were able to estimate the anisotropy ratio

  15. Aging in a Structural Glass

    OpenAIRE

    Kob, Walter; Barrat, Jean-Louis

    1998-01-01

    We discuss the relaxation dynamics of a simple structural glass which has been quenched below its glass transition temperature. We demonstrate that time correlation functions show strong aging effects and investigate in what way the fluctuation dissipation theorem is violated.

  16. Evidence for two spin-glass transitions with magnetoelastic and magnetoelectric couplings in the multiferroic (B i1 -xB ax) (F e1 -xT ix ) O3 system

    Science.gov (United States)

    Kumar, Arun; Kaushik, S. D.; Siruguri, V.; Pandey, Dhananjai

    2018-03-01

    For disordered Heisenberg systems with small single ion anisotropy (D ), two spin-glass (SG) transitions below the long-range ordered (LRO) phase transition temperature (Tc) have been predicted theoretically for compositions close to the percolation threshold. Experimental verification of these predictions is still controversial for conventional spin glasses. We show that multiferroic spin-glass systems can provide a unique platform for verifying these theoretical predictions via a study of change in magnetoelastic and magnetoelectric couplings, obtained from an analysis of diffraction data, at the spin-glass transition temperatures (TSG). Results of macroscopic (dc M (H , T ), M(t ), ac susceptibility [χ (ω, T )], and specific heat (Cp)) and microscopic (x-ray and neutron scattering) measurements are presented on disordered BiFe O3 , a canonical Heisenberg system with small single ion anisotropy, which reveal appearance of two spin-glass phases, SG1 and SG2, in coexistence with the LRO phase below the Almeida-Thouless (A-T) and Gabey-Toulouse (G-T) lines. It is shown that the temperature dependence of the integrated intensity of the antiferromagnetic (AFM) peak shows dips with respect to the Brillouin function behavior around the SG1 and SG2 transition temperatures. The temperature dependence of the unit cell volume departs from the Debye-Grüneisen behavior below the SG1 transition and the magnitude of departure increases significantly with decreasing temperature up to the electromagnon driven transition temperature below which a small change of slope occurs followed by another similar change of slope at the SG2 transition temperature. The ferroelectric polarization also changes significantly at the two spin-glass transition temperatures. These results, obtained using microscopic techniques, clearly demonstrate that the SG1 and SG2 transitions occur on the same magnetic sublattice and are intrinsic to the system. We also construct a phase diagram showing all

  17. On the transition from tin-rich to antimony-rich European white soda-glass trade beads for the Senecas of Northeastern North America

    International Nuclear Information System (INIS)

    Sempowski, M.L.; Nohe, A.W.; Moreau, J.F.; Karklins, K.; Aufreiter, S.; Toronto Univ. ON; Hancock, R.G.V.; Royal Military College, Kingston, ON

    2000-01-01

    It has been shown that several modifications occurred, over the span of the 17th to 19th centuries, in the agents used to opacify European-made white soda-glass beads that were transmitted as trade goods to northeastern North America. Tin was used at the beginning of the 17th century, followed by Sb later in the century, and then by As during the 18th and 19th centuries. In an attempt to define more closely the transition from Sn-rich to Sb-rich white beads, 198 white glass beads from a number of archaeological sites in western New York State were analyzed. It was shown that the arrival of Sb-white soda-glass trade beads began in this region during the period from approximately A.D. 1625-1640, and that they had completely replaced Sn-white beads by A.D. 1675. Specific bead chemistries link a number of the archaeological sites. (author)

  18. Analysis of water sorption isotherms of amorphous food materials by solution thermodynamics with relevance to glass transition: evaluation of plasticizing effect of water by the thermodynamic parameters.

    Science.gov (United States)

    Shimazaki, Eriko; Tashiro, Akiko; Kumagai, Hitomi; Kumagai, Hitoshi

    2017-04-01

    Relation between the thermodynamic parameters obtained from water sorption isotherms and the degree of reduction in the glass transition temperature (T g ), accompanied by water sorption, was quantitatively studied. Two well-known glassy food materials namely, wheat gluten and maltodextrin were used as samples. The difference between the chemical potential of water in a solution and that of pure water ([Formula: see text]), the difference between the chemical potential of solid in a solution and that of a pure solid ([Formula: see text]), and the change in the integral Gibbs free energy ([Formula: see text]) were obtained by analyzing the water sorption isotherms using solution thermodynamics. The parameter [Formula: see text] correlated well with ΔT g (≡T g  - T g0 ; where T g0 is the glass transition temperature of dry material), which had been taken to be an index of plasticizing effect. This indicates that plasticizing effect of water on foods can be evaluated through the parameter [Formula: see text].

  19. Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C.

    Science.gov (United States)

    Cervenka, L; Kubínová, J; Juszczak, L; Witczak, M

    2012-02-01

    Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35-0.90 a(w) , whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 a(w) . Blahovec-Yanniotis was considered to give the best fit over the whole range of a(w) tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec-Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (T (g)) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the T (g) line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.

  20. Glass transition dynamics and conductivity scaling in ionic deep eutectic solvents: The case of (acetamide + lithium nitrate/sodium thiocyanate) melts

    Energy Technology Data Exchange (ETDEWEB)

    Tripathy, Satya N., E-mail: satyanarayantripathy@gmail.com; Wojnarowska, Zaneta; Knapik, Justyna; Paluch, Marian [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1A, 41-500 Chorzow (Poland); Shirota, Hideaki [Department of Nanomaterial Science and Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522 (Japan); Biswas, Ranjit [Department of Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700098 (India)

    2015-05-14

    A detailed investigation on the molecular dynamics of ionic deep eutectic solvents (acetamide + lithium nitrate/sodium thiocyanate) is reported. The study was carried out employing dielectric relaxation spectroscopy covering seven decades in frequency (10{sup −1}-10{sup 6} Hz) and in a wide temperature range from 373 K down to 173 K, accessing the dynamic observables both in liquid and glassy state. The dielectric response of the ionic system has been presented in the dynamic window of modulus formalism to understand the conductivity relaxation and its possible connection to the origin of localized motion. Two secondary relaxation processes appear below glass transition temperature. Our findings provide suitable interpretation on the nature of secondary Johari-Goldstein process describing the ion translation and orientation of dipoles in a combined approach using Ngai’s coupling model. A nearly constant loss feature is witnessed at shorter times/lower temperatures. We also discuss the ac conductivity scaling behavior using Summerfield approach and random free energy barrier model which establish the time-temperature superposition principle. These experimental observations have fundamental importance on theoretical elucidation of the conductivity relaxation and glass transition phenomena in molten ionic conductors.

  1. Effect of carbon nanotube dispersion on glass transition in cross-linked epoxy-carbon nanotube nanocomposites: role of interfacial interactions.

    Science.gov (United States)

    Khare, Ketan S; Khare, Rajesh

    2013-06-20

    We have used atomistic molecular simulations to study the effect of nanofiller dispersion on the glass transition behavior of cross-linked epoxy-carbon nanotube (CNT) nanocomposites. Specific chemical interactions at the interface of CNTs and cross-linked epoxy create an interphase region, whose impact on the properties of their nanocomposites increases with an increasing extent of dispersion. To investigate this aspect, we have compared the volumetric, structural, and dynamical properties of three systems: neat cross-linked epoxy, cross-linked epoxy nanocomposite containing dispersed CNTs, and cross-linked epoxy nanocomposite containing aggregated CNTs. We find that the nanocomposite containing dispersed CNTs shows a depression in the glass transition temperature (Tg) by ~66 K as compared to the neat cross-linked epoxy, whereas such a large depression is absent in the nanocomposite containing aggregated CNTs. Our results suggest that the poor interfacial interactions between the CNTs and the cross-linked epoxy matrix lead to a more compressible interphase region between the CNTs and the bulk matrix. An analysis of the resulting dynamic heterogeneity shows that the probability of percolation of immobile domains becomes unity near the Tg calculated from volumetric properties. Our observations also lend support to the conceptual analogy between polymer nanocomposites and the nanoconfinement of polymer thin films.

  2. Shape Engineering of Biomass-Derived Nanoparticles from Hollow Spheres to Bowls via Solvent-Induced Buckling.

    Science.gov (United States)

    Chen, Chunhong; Li, Xuefeng; Jiang, Deng; Wang, Zhe; Wang, Yong

    2018-06-19

    To realize the asymmetry for the hollow carbonaceous nanostructures remains to be a great challenge, especially when biomass is chosen as the carbon resource via hydrothermal carbonization (HTC). Herein, a simple and straightforward solvent induced buckling strategy is demonstrated for the synthesis of asymmetric spherical and bowllike carbonaceous nanomaterials. The formation of the bowllike morphology was attributed to the buckling of the spherical shells induced by the dissolution of the oligomers. The bowllike particles made by this solvent-driven approach demonstrated a well-controlled morphology and a uniform particle size of ~360 nm. The obtained nanospheres and nanobowls can be loaded with CoS2 nanoparticles to act as novel heterogeneous catalysts for the selective hydrogenation of aromatic nitro compounds. With the bowllike structure in hand, as expected, the CoS2/nanobowls catalyst showed good tolerance to a wide scope of reducible groups and afforded both high activity and selectivity in almost all the tested substrates (14). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. XRD and FTIR studies the effect of heat treatment and doping the transition metal oxide on LiNbO3 and LiNb3O8 nano-crystallite phases in lithium borate glass system.

    Science.gov (United States)

    Kashif, Ismail; Soliman, Ashia A; Sakr, Elham M; Ratep, Asmaa

    2013-09-01

    Glasses of various compositions in the system 90 Li2B4O7-10 Nb2O5 mixed with T.M ions (where T.M is the transition metal) were prepared by quenching technique. Heat-treatment of the parent glasses was performed at 540, 570 and 620 °C, for 5 and 16 h. The glass structure evolution during the controlled crystallization was examined by XRD and FT-IR spectroscopy analysis. The crystalline phases present in the glass ceramics were identified via X-ray diffraction as a function of heat treatment. The FT-IR data propose for these glasses and heat-treated glass network structures mainly built by: di-, tri-, tetra-, penta-and ortho-borate groups. It was found that the quantitative evolution of these various borate species in the glass structures is influenced by the transition metal. A detailed discussion relating to the N4 evolution with the T.M content was made. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Temperature dependent charge transport studies across thermodynamic glass transition in P3HT:PCBM bulk heterojunction: insight from J-V and impedance spectroscopy

    Science.gov (United States)

    Sarkar, Atri; Rahaman, Abdulla Bin; Banerjee, Debamalya

    2018-03-01

    Temperature dependent charge transport properties of P3HT:PCBM bulk heterojunction are analysed by dc and ac measurements under dark conditions across a wide temperature range of 110-473 K, which includes the thermodynamic glass transition temperature (Tg ˜320 K) of the system. A change from Ohmic conduction to space charge limited current conduction at higher (⩾1.2 V) applied bias voltages above  ⩾200 K is observed from J-V characteristics. From capacitance-voltage (C-V) measurement at room temperature, the occurrence of a peak near the built-in voltage is observed below the dielectric relaxation frequency, originating from the competition between drift and diffusion driven motions of charges. Carrier concentration (N) is calculated from C-V measurements taken at different temperatures. Room temperature mobility values at various applied bias voltages are in accordance with that obtained from transient charge extraction by linearly increasing voltage measurement. Sample impedance is measured over five decades of frequency across temperature range by using lock-in detection. This data is used to extract temperature dependence of carrier mobility (μ), and dc conductivity (σ_dc ) which is low frequency extrapolation of ac conductivity. An activation energy of  ˜126 meV for the carrier hopping process at the metal-semiconductor interface is estimated from temperature dependence of σ_dc . Above T g, μ levels off to a constant value, whereas σ_dc starts to decrease after a transition knee at T g that can be seen as a combined effect of changes in μ and N. All these observed changes across T g can be correlated to enhanced polymer motion above the glass transition.

  5. Observation of the anisotropic spin-glass transition and transverse spin ordering in pseudo-brookite through muon spin relaxation

    NARCIS (Netherlands)

    Boekema, C.; Brabers, V.A.M.; Lichti, R.L.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Schillaci, M.E.; MacLaughlin, D.E.; Dodds, S.A.

    1986-01-01

    Zero-field longitudinal muon-spin-relaxation (µSR) experiments have been performed on single crystals of pseudo-brookite (Fe2-xTil+x O 5; x=0.25), an anisotropic spin-glass system. The spinglass temperature (Tg) is determined to be 44.0±0.5K. Above Tg, a distinct exponential muon-spin-relaxation

  6. The mechanism of deceleration of nucleation and crystal growth by the small addition of transition metals to lithium disilicate glasses

    Science.gov (United States)

    Thieme, Katrin; Avramov, Isak; Rüssel, Christian

    2016-01-01

    The addition of small amounts of niobium or tantalum oxide to lithium disilicate glass provokes a drastic decrease of the steady-state nucleation rates and the crystal growth velocities. The viscosity of the residual glassy matrix is considered as a function of the crystallization degree in the course of a non-isothermal crystallization. For simplification, a homogeneous distribution of the added oxides in the glass matrix is assumed. While the viscosity initially decreases, it significantly increases again for higher crystallization degrees hindering crystal growth. However, it was shown that the additives are enriched at the crystal interface. Several possible reasons for the inhibition of nucleation and growth kinetics such as viscosity, interfacial energy crystal/glassy phase, thermodynamic driving force or impingement rate are discussed. Since the crystallization front is blocked by the additives the impingement rate is decreased with increasing additive concentration. Since small concentrations of Nb2O5 and Ta2O5 have a drastic effect on the nucleation, these components should be enriched at the interface crystal/glass. This will only take place, if it leads to a decrease in the interfacial energy. Since this effect alone should result in an increase of the nucleation rate, it must be overcompensated by kinetic effects. PMID:27150844

  7. Humidity-dependent compression-induced glass transition of the air-water interfacial Langmuir films of poly(D,L-lactic acid-ran-glycolic acid) (PLGA).

    Science.gov (United States)

    Kim, Hyun Chang; Lee, Hoyoung; Jung, Hyunjung; Choi, Yun Hwa; Meron, Mati; Lin, Binhua; Bang, Joona; Won, You-Yeon

    2015-07-28

    Constant rate compression isotherms of the air-water interfacial Langmuir films of poly(D,L-lactic acid-ran-glycolic acid) (PLGA) show a distinct feature of an exponential increase in surface pressure in the high surface polymer concentration regime. We have previously demonstrated that this abrupt increase in surface pressure is linked to the glass transition of the polymer film, but the detailed mechanism of this process is not fully understood. In order to obtain a molecular-level understanding of this behavior, we performed extensive characterizations of the surface mechanical, structural and rheological properties of Langmuir PLGA films at the air-water interface, using combined experimental techniques including the Langmuir film balance, X-ray reflectivity and double-wall-ring interfacial rheometry methods. We observed that the mechanical and structural responses of the Langmuir PLGA films are significantly dependent on the rate of film compression; the glass transition was induced in the PLGA film only at fast compression rates. Surprisingly, we found that this deformation rate dependence is also dependent on the humidity of the environment. With water acting as a plasticizer for the PLGA material, the diffusion of water molecules through the PLGA film seems to be the key factor in the determination of the glass transformation properties and thus the mechanical response of the PLGA film against lateral compression. Based on our combined results, we hypothesize the following mechanism for the compression-induced glass transformation of the Langmuir PLGA film; (1) initially, a humidified/non-glassy PLGA film is formed in the full surface-coverage region (where the surface pressure shows a plateau) during compression; (2) further compression leads to the collapse of the PLGA chains and the formation of new surfaces on the air side of the film, and this newly formed top layer of the PLGA film is transiently glassy in character because the water evaporation rate

  8. Non-ergodicity transition and multiple glasses in binary mixtures: on the accuracy of the input static structure in the mode coupling theory

    International Nuclear Information System (INIS)

    Tchangnwa Nya, F; Ayadim, A; Germain, Ph; Amokrane, S

    2012-01-01

    We examine the question of the accuracy of the static correlation functions used as input in the mode coupling theory (MCT) of non-ergodic states in binary mixtures. We first consider hard-sphere mixtures and compute the static pair structure from the Ornstein-Zernike equations with the Percus-Yevick closure and more accurate ones that use bridge functions deduced from Rosenfeld’s fundamental measures functional. The corresponding MCT predictions for the non-ergodicity lines and the transitions between multiple glassy states are determined from the long-time limit of the density autocorrelation functions. We find that while the non-ergodicity transition line is not very sensitive to the input static structure, up to diameter ratios D 2 /D 1 = 10, quantitative differences exist for the transitions between different glasses. The discrepancies with the more accurate closures become even qualitative for sufficiently asymmetric mixtures. They are correlated with the incorrect behavior of the PY structure at high size asymmetry. From the example of ultra-soft potential it is argued that this issue is of general relevance beyond the hard-sphere model. (paper)

  9. On the temperature dependence of the Adam-Gibbs equation around the crossover region in the glass transition

    Science.gov (United States)

    Duque, Michel; Andraca, Adriana; Goldstein, Patricia; del Castillo, Luis Felipe

    2018-04-01

    The Adam-Gibbs equation has been used for more than five decades, and still a question remains unanswered on the temperature dependence of the chemical potential it includes. Nowadays, it is a well-known fact that in fragile glass formers, actually the behavior of the system depends on the temperature region it is being studied. Transport coefficients change due to the appearance of heterogeneity in the liquid as it is supercooled. Using the different forms for the logarithmic shift factor and the form of the configurational entropy, we evaluate this temperature dependence and present a discussion on our results.

  10. Contrasting the magnetic response between magnetic-glass and reentrant spin-glass

    OpenAIRE

    Roy, S. B.; Chattopadhyay, M. K.

    2008-01-01

    Magnetic-glass is a recently identified phenomenon in various classes of magnetic systems undergoing a first order magnetic phase transition. We shall highlight here a few experimentally determined characteristics of magnetic-glass and the relevant set of experiments, which will enable to distinguish a magnetic-glass unequivocally from the well known phenomena of spin-glass and reentrant spin-glass.

  11. TRANSIT

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. TRANSIT. SYSTEM: DETERMINE 2D-POSITION GLOBALLY BUT INTERMITTENT (POST-FACTO). IMPROVED ACCURACY. PRINCIPLE: POLAR SATELLITES WITH INNOVATIONS OF: GRAVITY-GRADIENT ATTITUDE CONTROL; DRAG COMPENSATION. WORKS ...

  12. Anelastic and viscoelastic behaviour of amorphous Zr65Cu17.5Ni10Al7.5 in the range of the glass transition

    International Nuclear Information System (INIS)

    Ulfert, W.; Kronmueller, H.

    1996-01-01

    Reversible (anelasticity) and the irreversible (viscosity) relaxations in the amorphous alloy Zr 65 Cu 17.5 Ni 10 Al 7.5 have been investigated by means of creep and mechanic after-effect measurements of the shear strain, which were performed in an inverted torsion pendulum. For the evaluation of the measurements a new relaxation model is proposed which takes into account that in the range of the glass-transition temperature T g the local atomic arrangement is steadely changing. By introducing a finite mean life time τ l of local structure units we are able to trace the origin of the anelasticity and the viscosity to the same atomic relaxation processes. The temperature dependence of the viscosity η measured between 560 K and 668 K shows a jump in the activation energy at T g = 606 K from 2.1 eV below T g to 5.6 eV above T g . (orig.)

  13. Alternating copolymerization of propylene oxide with biorenewable terpene-based cyclic anhydrides: a sustainable route to aliphatic polyesters with high glass transition temperatures.

    Science.gov (United States)

    Van Zee, Nathan J; Coates, Geoffrey W

    2015-02-23

    The alternating copolymerization of propylene oxide with terpene-based cyclic anhydrides catalyzed by chromium, cobalt, and aluminum salen complexes is reported. The use of the Diels-Alder adduct of α-terpinene and maleic anhydride as the cyclic anhydride comonomer results in amorphous polyesters that exhibit glass transition temperatures (Tg ) of up to 109 °C. The polymerization conditions and choice of catalyst have a dramatic impact on the molecular weight distribution, the relative stereochemistry of the diester units along the polymer chain, and ultimately the Tg of the resulting polymer. The aluminum salen complex exhibits exceptional selectivity for copolymerization without transesterification or epimerization side reactions. The resulting polyesters are highly alternating and have high molecular weights and narrow polydispersities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Evidence for a vortex-glass transition in superconducting Ba(Fe0.9Co0.1)2As2.

    Science.gov (United States)

    Prando, G; Giraud, R; Aswartham, S; Vakaliuk, O; Abdel-Hafiez, M; Hess, C; Wurmehl, S; Wolter, A U B; Büchner, B

    2013-12-18

    Measurements of magneto-resistivity and magnetic susceptibility were performed on single crystals of superconducting Ba(Fe0.9Co0.1)2As2 close to the conditions of optimal doping. The high quality of the investigated samples allows us to reveal dynamic scaling behaviour associated with a vortex-glass phase transition in the limit of a weak degree of quenched disorder. Accordingly, the dissipative component of the ac susceptibility is reproduced well within the framework of Havriliak-Negami relaxation, assuming a critical power-law divergence for the characteristic correlation time τ of the vortex dynamics. Remarkably, the random disorder introduced by the Fe1-xCox chemical substitution is found to act on the vortices as a much weaker quenched disorder than previously reported for cuprate superconductors such as Y1-xPrxBa2Cu3O7-δ.

  15. Synthesis of POSS-based ionic conductors with low glass transition temperatures for efficient solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Zhang, Wei; Wang, Zhong-Sheng

    2014-07-09

    Replacing liquid-state electrolytes with solid-state electrolytes has been proven to be an effective way to improve the durability of dye-sensitized solar cells (DSSCs). We report herein the synthesis of amorphous ionic conductors based on polyhedral oligomeric silsesquioxane (POSS) with low glass transition temperatures for solid-state DSSCs. As the ionic conductor is amorphous and in the elastomeric state at the operating temperature of DSSCs, good pore filling in the TiO2 film and good interfacial contact between the solid-state electrolyte and the TiO2 film can be guaranteed. When the POSS-based ionic conductor containing an allyl group is doped with only iodine as the solid-state electrolyte without any other additives, power conversion efficiency of 6.29% has been achieved with good long-term stability under one-sun soaking for 1000 h.

  16. Relaxation processes and glass transition of confined polymer melts: A molecular dynamics simulation of 1,4-polybutadiene between graphite walls.

    Science.gov (United States)

    Solar, M; Binder, K; Paul, W

    2017-05-28

    Molecular dynamics simulations of a chemically realistic model for 1,4-polybutadiene in a thin film geometry confined by two graphite walls are presented. Previous work on melts in the bulk has shown that the model faithfully reproduces static and dynamic properties of the real material over a wide temperature range. The present work studies how these properties change due to nano-confinement. The focus is on orientational correlations observable in nuclear magnetic resonance experiments and on the local intermediate incoherent neutron scattering function, F s (q z , z, t), for distances z from the graphite walls in the range of a few nanometers. Temperatures from about 2T g down to about 1.15T g , where T g is the glass transition temperature in the bulk, are studied. It is shown that weakly attractive forces between the wall atoms and the monomers suffice to effectively bind a polymer coil that is near the wall. For a wide regime of temperatures, the Arrhenius-like adsorption/desorption kinetics of the monomers is the slowest process, while very close to T g the Vogel-Fulcher-Tammann-like α-relaxation takes over. The α-process is modified only for z≤1.2 nm due to the density changes near the walls, less than expected from studies of coarse-grained (bead-spring-type) models. The weakness of the surface effects on the glass transition in this case is attributed to the interplay of density changes near the wall with the torsional potential. A brief discussion of pertinent experiments is given.

  17. Effects of temperature changes and stress loading on the mechanical and shape memory properties of thermoplastic materials with different glass transition behaviours and crystal structures.

    Science.gov (United States)

    Iijima, Masahiro; Kohda, Naohisa; Kawaguchi, Kyotaro; Muguruma, Takeshi; Ohta, Mitsuru; Naganishi, Atsuko; Murakami, Takashi; Mizoguchi, Itaru

    2015-12-01

    To investigate the effects of temperature changes and stress loading on the mechanical and shape memory properties of thermoplastic materials with different glass transition behaviours and crystal structures. Five thermoplastic materials, polyethylene terephthalate glycol (Duran®, Scheu Dental), polypropylene (Hardcast®, Scheu Dental), and polyurethane (SMP MM®, SMP Technologies) with three different glass transition temperatures (T g) were selected. The T g and crystal structure were assessed using differential scanning calorimetry and X-ray diffraction. The deterioration of mechanical properties by thermal cycling and the orthodontic forces during stepwise temperature changes were investigated using nanoindentation testing and custom-made force-measuring system. The mechanical properties were also evaluated by three-point bending tests; shape recovery with heating was then investigated. The mechanical properties for each material were decreased significantly by 2500 cycles and great decrease was observed for Hardcast (crystal plastic) with higher T g (155.5°C) and PU 1 (crystalline or semi-crystalline plastic) with lower T g (29.6°C). The Duran, PU 2, and PU 3 with intermediate T g (75.3°C for Duran, 56.5°C for PU 2, and 80.7°C for PU 3) showed relatively stable mechanical properties with thermal cycling. The polyurethane polymers showed perfect shape memory effect within the range of intraoral temperature changes. The orthodontic force produced by thermoplastic appliances decreased with the stepwise temperature change for all materials. Orthodontic forces delivered by thermoplastic appliances may influence by the T g of the materials, but not the crystal structure. Polyurethane is attractive thermoplastic materials due to their unique shape memory phenomenon, but stress relaxation with temperature changes is expected. © The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For

  18. Glass-forming ability and stability of ternary Ni-early transition metal (Ti/Zr/Hf) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Basu, Joysurya [Department of Metallurgy, Indian Institute of Science, Bangalore 560 012 (India); Ranganathan, S. [Department of Metallurgy, Indian Institute of Science, Bangalore 560 012 (India)]. E-mail: rangu@met.iisc.ernet.in

    2006-08-15

    Four Ni-bearing Ti, Zr and Hf ternary alloys of nominal composition Zr{sub 41.5}Ti{sub 41.5}Ni{sub 17}, Zr{sub 25}Ti{sub 25}Ni{sub 50}, Zr{sub 41.5}Hf{sub 41.5}Ni{sub 17} and Ti{sub 41.5}Hf{sub 41.5}Ni{sub 17} were rapidly solidified in order to produce ribbons. The Zr-Ti-Ni and Ti-Hf-Ni alloys become amorphous, whereas the Zr-Hf-Ni alloy shows precipitation of a cubic phase. The devitrification of all three alloys was followed and the relative tendency to form nanoquasicrystals and cF96 phases analysed. The relative glass-forming ability of the alloys can be explained by taking into account their atomic size difference. Addition of Ni often leads to quasicrystallisation or quasicrystal-related phases. This can be explained by the atomic radius and heat of mixing of the constituent elements. The phases precipitated at the initial stages of crystallisation indicate the possible presence of Frank-Kasper polyhedral structure in the amorphous alloys. Structural analysis reveals that the Laves and the anti-Laves phases have the same polyhedral structural unit, which is similar to the structural characteristics of glass.

  19. Granular packing as model glass formers

    International Nuclear Information System (INIS)

    Wang Yujie

    2017-01-01

    Static granular packings are model hard-sphere glass formers. The nature of glass transition has remained a hotly debated issue. We review recent experimental progresses in using granular materials to study glass transitions. We focus on the growth of glass order with five-fold symmetry in granular packings and relate the findings to both geometric frustration and random first-order phase transition theories. (paper)

  20. Mechanical relaxation in glasses

    International Nuclear Information System (INIS)

    Hiki, Y.

    2004-01-01

    The basic properties of glasses and the characteristics of mechanical relaxation in glasses were briefly reviewed, and then our studies concerned were presented. Experimental methods adopted were viscosity, internal friction, ultrasonic attenuation, and Brillouin scattering measurements. The specimens used were several kinds of inorganic, organic, and metallic glasses. The measurements were mainly carried out from the room temperature up to the glass transition temperature, and the relaxation time was determined as a function of temperature. The 'double relaxation' composed of two Arrhenius-type relaxations was observed in many materials. In both relaxations, the 'compensation effect' showing a correlation of the pre-exponential factor and the activation energy was observed. These results were explained by considering the 'complex relaxation' due to cooperative motions of atoms or group of atoms. Values of activation energy near the glass transition determined by the various experimental methods were compared with each other

  1. Ion exchange for glass strengthening

    International Nuclear Information System (INIS)

    Gy, Rene

    2008-01-01

    This paper presents a short overview of silicate glass strengthening by exchange of alkali ions in a molten salt, below the glass transition temperature (chemical tempering). The physics of alkali inter-diffusion is briefly explained and the main parameters of the process, which control the glass reinforcement, are reviewed. Methods for characterizing the obtained residual stress state and the strengthening are described, along with the simplified modelling of the stress build-up. The fragmentation of chemically tempered glass is discussed. The concept of engineered stress profile glass is presented, and finally, the effect of glass and salt compositions is overviewed

  2. Electronic structure of metallic glasses

    International Nuclear Information System (INIS)

    Oelhafen, P.; Lapka, R.; Gubler, U.; Krieg, J.; DasGupta, A.; Guentherodt, H.J.; Mizoguchi, T.; Hague, C.; Kuebler, J.; Nagel, S.R.

    1981-01-01

    This paper is organized in six sections and deals with (1) the glassy transition metal alloys, their d-band structure, the d-band shifts on alloying and their relation to the alloy heat of formation (ΔH) and the glass forming ability, (2) the glass to crystal phase transition viewed by valence band spectroscopy, (3) band structure calculations, (4) metallic glasses prepared by laser glazing, (5) glassy normal metal alloys, and (6) glassy hydrides

  3. New Insights into Lamellar Structure Development and SAXS/WAXD Sequence Appearance During Uniaxial Stretching of Amorphous Poly(ethylene terephthalate) Above Glass Transition Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami,D.; Burger, C.; Ran, S.; Avila-Orta, C.; Sics, I.; Chu, B.; Chiao, S.; Hsiao, B.; Kikutani, T.

    2008-01-01

    An in situ study of structure formation in amorphous poly(ethylene terephthalate) (PET) during uniaxial stretching at a temperature 30 C above glass transition temperature was carried out using synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. Three major deformation-induced structure transitions were confirmed. (1) At small strains, the applied load increased initially but leveled off afterward. Sporadic isotropic crystallization without preferred orientation was observed by WAXD, where no hierarchical structure was seen by SAXS. (2) At intermediate strains, strain hardening took place. Although WAXD showed persistent progression of isotropic crystallization, SAXS indicated formation of a layered structure as well as a fibrillar domain in large scale. This behavior is not consistent with the mechanisms for shish-kebab or spinodal-assisted structure formation. Instead, it can be explained by flow-induced demixing of crystal and amorphous phases through layerlike flocking motion perpendicular to the stretching direction. (3) At high strains, the ratio between the applied load and strain was about constant. In this stage, crystal reorientation and lateral crystal growth took place. The corresponding structure changes could be categorized into three subregions. In the first region, the (010) crystalline plane began to orient. In the second region, the (100) crystalline plane began to orient. In the last region, the structure change became stable and the sample eventually broke apart.

  4. Glass science tutorial: Lecture number-sign 1, Chemistry and properties of oxide glasses. Professor William C. LaCourse, Lecturer

    International Nuclear Information System (INIS)

    Kruger, A.A.

    1994-10-01

    The tutorial covers the following topics: Definitions and terminology; Introduction to glass structure and properties; The glass transition; Structure/property relationships in oxide glasses; Generalized models for predicting structure/properties; Glass surfaces; Chemical durability; and Mechanical properties

  5. Dynamics of molecular rotors confined in two dimensions: transition from a 2D rotational glass to a 2D rotational fluid in a periodic mesoporous organosilica.

    Science.gov (United States)

    Vogelsberg, Cortnie S; Bracco, Silvia; Beretta, Mario; Comotti, Angiolina; Sozzani, Piero; Garcia-Garibay, Miguel A

    2012-02-09

    orientationally disordered 2D rotational glass and its transition from rigid to soft at increasing temperature. The spectral narrowing observed in the (2)H NMR experiments at higher temperatures (310-420 K) is consistent with fast rotational dynamics, which remain anisotropic in nature within the robust lamellar architecture. This study suggests that exploiting reduced dimensionality in the design of solid-state artificial molecular machines and functional materials may yield access to behavior previously unrealized in 3D materials. © 2012 American Chemical Society

  6. Non-equilibrium phenomena in confined soft matter irreversible adsorption, physical aging and glass transition at the nanoscale

    CERN Document Server

    2015-01-01

    This book presents cutting-edge experimental and computational results and provides comprehensive coverage on the impact of non-equilibrium structure and dynamics on the properties of soft matter confined to the nanoscale. The book is organized into three main sections: ·         Equilibration and physical aging: by treating non-equilibrium phenomena with the formal methodology of statistical physics in bulk, the analysis of the kinetics of equilibration sheds new light on the physical origin of the non-equilibrium character of thin polymer films. Both the impact of sample preparation and that of interfacial interactions are analyzed using a large set of experiments. A historical overview of the investigation of the non-equilibrium character of thin polymer films is also presented. Furthermore, the discussion focuses on how interfaces and geometrical confinement perturb the pathways and kinetics of equilibrations of soft glasses (a process of tremendous technological interest). ·         Irr...

  7. Time-convolutionless mode-coupling theory near the glass transition: Numerical solutions for the Percus-Yevick model

    International Nuclear Information System (INIS)

    Kimura, Y.; Tokuyama, M.

    2016-01-01

    The full numerical solutions of the time-convolutionless modecoupling theory (TMCT) equation recently proposed by Tokuyama are compared with those of the ideal mode-coupling theory (MCT) equation based on the Percus- Yevick static structure factor for hard spheres qualitatively and quantitatively. The ergodic to non-ergodic transition at the critical volume fraction φ_c predicted by MCT is also shown to occur even for TMCT. Thus, φ_c of TMCT is shown to be much higher than that of MCT. The dynamics of coherent-intermediate scattering functions and their two-step relaxation process in a β stage are also discussed.

  8. Photostabilisation of the 'wood-clearcoatings' systems with UV absorbers: correlation with their effect on the glass transition temperature

    International Nuclear Information System (INIS)

    Aloui, F; Ahajji, A; Irmouli, Y; George, B; Charrier, B; Merlin, A

    2006-01-01

    In an application-oriented study, the effective transition temperature T g of organic wood-clearcoatings between a hard, glassy state and a viscoelastic and rubbery state is measured. The value of T g is important in the eventual development of cracks and a thermomechanical analysis is used to study the photostabilisation performance of some UV absorbers. A weathering exposure test suggests that certain organic UV absorbers have quite a low T g and may inhibit the crack formation, in contrast with inorganic UV absorbers

  9. Bulk metallic glasses: A new class of engineering materials

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    been discovered. Glass-forming ability depends on various factors like enthalpy ... The determination of a glass transition temperature in ... Rao (1980) has postulated that an alloy with the smallest possible molar volume is most prone to glass ...

  10. Crystallization study of Te–Bi–Se glasses

    Indian Academy of Sciences (India)

    Unknown

    Thermal stability; chalcogenide glasses; glass forming ability; glass transition temperature. 1. Introduction ... as well as their wide technological applications including threshold and ... are other important aspects such as ON-state current,.

  11. Characterization of dynamics in complex lyophilized formulations: I. Comparison of relaxation times measured by isothermal calorimetry with data estimated from the width of the glass transition temperature region.

    Science.gov (United States)

    Chieng, Norman; Mizuno, Masayasu; Pikal, Michael

    2013-10-01

    The purposes of this study are to characterize the relaxation dynamics in complex freeze dried formulations and to investigate the quantitative relationship between the structural relaxation time as measured by thermal activity monitor (TAM) and that estimated from the width of the glass transition temperature (ΔT(g)). The latter method has advantages over TAM because it is simple and quick. As part of this objective, we evaluate the accuracy in estimating relaxation time data at higher temperatures (50 °C and 60 °C) from TAM data at lower temperature (40 °C) and glass transition region width (ΔT(g)) data obtained by differential scanning calorimetry. Formulations studied here were hydroxyethyl starch (HES)-disaccharide, HES-polyol, and HES-disaccharide-polyol at various ratios. We also re-examine, using TAM derived relaxation times, the correlation between protein stability (human growth hormone, hGH) and relaxation times explored in a previous report, which employed relaxation time data obtained from ΔT(g). Results show that most of the freeze dried formulations exist in single amorphous phase, and structural relaxation times were successfully measured for these systems. We find a reasonably good correlation between TAM measured relaxation times and corresponding data obtained from estimates based on ΔT(g), but the agreement is only qualitative. The comparison plot showed that TAM data are directly proportional to the 1/3 power of ΔT(g) data, after correcting for an offset. Nevertheless, the correlation between hGH stability and relaxation time remained qualitatively the same as found with using ΔT(g) derived relaxation data, and it was found that the modest extrapolation of TAM data to higher temperatures using ΔT(g) method and TAM data at 40 °C resulted in quantitative agreement with TAM measurements made at 50 °C and 60 °C, provided the TAM experiment temperature, is well below the Tg of the sample. Copyright © 2013 Elsevier B.V. All rights

  12. Electrical properties of phosphate glasses

    International Nuclear Information System (INIS)

    Mogus-Milankovic, A; Santic, A; Reis, S T; Day, D E

    2009-01-01

    Investigation of the electrical properties of phosphate glasses where transition metal oxide such as iron oxide is the network former and network modifier is presented. Phosphate glasses containing iron are electronically conducting glasses where the polaronic conduction is due to the electron hopping from low to high iron valence state. The identification of structural defects caused by ion/polaron migration, the analysis of dipolar states and electrical conductivity in iron phosphate glasses containing various alkali and mixed alkali ions was performed on the basis of the impedance spectroscopy (IS). The changes in electrical conductivity from as-quenched phosphate glass to fully crystallized glass (glass-ceramics) by IS are analyzed. A change in the characteristic features of IS follows the changes in glass and crystallized glass network. Using IS, the contribution of glass matrix, crystallized grains and grain boundary to the total electrical conductivity for iron phosphate glasses was analyzed. It was shown that decrease in conductivity is caused by discontinuities in the conduction pathways as a result of the disruption of crystalline network where two or more crystalline phases are formed. Also, phosphate-based glasses offer a unique range of biomaterials, as they form direct chemical bonding with hard/soft tissue. The surface charges of bioactive glasses are recognized to be the most important factors in determining biological responses. The improved bioactivity of the bioactive glasses as a result of the effects of the surface charges generated by electrical polarization is discussed.

  13. Phenylene ring dynamics in phenoxy and the effect of intramolecular linkages on the dynamics of some engineering thermoplastics below the glass transition temperature

    International Nuclear Information System (INIS)

    Arrese-Igor, Silvia; Arbe, Arantxa; Alegria, Angel; Colmenero, Juan; Frick, Bernhard

    2007-01-01

    We have investigated the dynamics of phenylene rings in the engineering thermoplastic bisphenol-A poly(hydroxyether)--phenoxy--below its glass transition temperature by means of neutron scattering techniques. A relatively wide dynamic range has been covered thanks to the combination of two different types of neutron spectrometers, time of flight and backscattering. Partially deuterated samples have been used in order to isolate the phenylene ring dynamics. The resulting neutron scattering signal of phenoxy has been described by a model that considers π flips and oscillation motions for phenylene rings. The associated time scales are broadly distributed with mean activation energies equal to 0.41 and 0.21 eV, respectively. Finally, a comparative study with the literature shows that the dielectric and mechanical γ relaxation in phenoxy exhibit good correlation with the characteristic times of the aliphatic chain published elsewhere and with the characteristic times observed for the motion of phenylene rings by neutron scattering. These findings are discussed in a more general framework that considers, in addition, previous results on other polymers, which also contain the bisphenol-A unit

  14. Correlations of norbornenyl crosslinked polyimide resin structures with resin thermo-oxidative stability, resin glass transition temperature and composite initial mechanical properties

    Science.gov (United States)

    Alston, William B.

    1988-01-01

    PMR (polymerization of monomeric reactants) methodology was used to prepare 70 different polyimide oligomeric resins and 30 different unidirectional graphite fiber/polyimide composites. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on resin thermo-oxidative stability and glass transition temperature (Tg) of the cured/postcured resins. A linear correlation of decreasing 316 C resin weight loss/surface area versus (1) decreasing aliphatic content, or (2) increasing benzylic/aliphatic content stoichiometry ratio over a wide range of resin compositions was observed. An almost linear correlation of Tg versus molecular distance between the crosslinks was also observed. An attempt was made to correlate Tg with initial composite mechanical properties (flexural strength and interlaminar shear strength). However, the scatter in mechanical strength data prevented obtaining a clear correlation. Instead, only a range of composite mechanical properties was obtained at 25, 288, and 316 C. Perhaps more importantly, what did become apparent during the correlation study was (1) the PMR methodology could be used to prepare composites from resins containing a wide variety of monomer modifications, (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins formulated exhibited satisfactory processing flow, and (3) that PMR resins exhibited predictable rates of 316 C weight loss/surface area based on their benzylic/aliphatic stoichiometery ratio.

  15. Measurement of glass transition temperature, residual heat of reaction and mixing ratio of epoxy resins using near infrared spectroscopy: a preliminary study

    DEFF Research Database (Denmark)

    Houmøller, Lars Plejdrup; Laursen, Peter Clemen

    2003-01-01

    As a measure of the degree of curing of epoxy resins, the glass transition temperature, Tg, and the residual heat of reaction, DeltaHr, are often used. In this study, near infrared spectroscopy and multivariate calibration (partial least squares regression (PLSR)) have been used to monitor the two...... variables, using differential scanning calorimetry (DSC) as the reference method. The epoxy under study was a commercial system consisting of the resin, trimethylolpropanetriglycidylether, and the hardener, 3-aminomethyl-3,5,5,-trimethylcyclohexylamine. Using samples cured under different conditions......, calibrations resulted in root mean square errors of cross-validation (RMSECV) of 18 J/g for DeltaHr (range for Hr: 6.1-231.3 J/g) and 7.2ºC for Tg (range for Tg: 41.5-98.8ºC). Also, a PLSR model for mixing ratio of hardener and resin was obtained, resulting in a RMSECV of 0.0040 (range for mixing ratio: 0.180-0.380)...

  16. Study of rigidity of semiconducting vanadate glasses and its ...

    Indian Academy of Sciences (India)

    These parameters along with the coordination number of the glasses affect the glass transition temperature. The correlation between the elastic moduli and thermal properties of these samples showed that 0.25MoO3–0.25PbO–0.5V2O5 glass is the most rigid and has an applicable glass transition temperature for coating.

  17. Oxynitride glasses: a review

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A.R.; Clausell, C.; Barba, A.

    2016-07-01

    Oxynitride glasses are special types of silicates or silicoaluminates which have been the object of many studies over the last forty years. They can be prepared by means of various complex methods, leading to variable levels of nitrogen incorporation, though in all cases giving limited transparency in the visible range. More recently, a new family of oxynitride glasses incorporating fluorine has been investigated. This paper outlines the effect of composition, in particular nitrogen and fluorine content, on properties such as glass transition temperature, hardness, Young's modulus, compactness and molar volume. (Author)

  18. Orbital glass in HTSC

    International Nuclear Information System (INIS)

    Kusmartsev, F.V.

    1992-10-01

    The physical reasons why the orbital glass may exist in granular high-temperature superconductors and the existing experimental data appeared recently are discussed. The orbital glass is characterized by the coexistence of the orbital paramagnetic state with the superconducting state and occurs at small magnetic fields H c0 c1 . The transition in orbital glass arises at the critical field H c0 which is inversely proportional to the surface cross-area S of an average grain. In connection with theoretical predictions the possible experiments are proposed. (author). 10 refs

  19. Crystallization of Yttrium and Samarium Aluminosilicate Glasses

    OpenAIRE

    Lago, Diana Carolina; Prado, Miguel Oscar

    2016-01-01

    Aluminosilicate glasses containing samarium and yttrium (SmAS and YAS glasses) exhibit high glass transition temperatures, corrosion resistance, and glass stability on heating which make them useful for technological applications. Yttrium aluminosilicate glass microspheres are currently being used for internal selective radiotherapy of liver cancer. During the preparation process, crystallization needs to be totally or partially avoided depending on the final application. Thus knowing the cry...

  20. Glass Membrane For Controlled Diffusion Of Gases

    Science.gov (United States)

    Shelby, James E.; Kenyon, Brian E.

    2001-05-15

    A glass structure for controlled permeability of gases includes a glass vessel. The glass vessel has walls and a hollow center for receiving a gas. The glass vessel contains a metal oxide dopant formed with at least one metal selected from the group consisting of transition metals and rare earth metals for controlling diffusion of the gas through the walls of the glass vessel. The vessel releases the gas through its walls upon exposure to a radiation source.