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Sample records for volume glass transition

  1. 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.

  2. 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...

  3. Kinetic criteria of glass formation and the pressure dependence of the glass transition temperature.

    Science.gov (United States)

    Schmelzer, Jürn W P

    2012-02-21

    An overview on different attempts of formulation of kinetic criteria of glass formation is given. It is analyzed which of the characteristic time scales-time of observation, time of relaxation, and time of change of external parameters-have to be employed to appropriately develop such criteria. Based on this analysis, a general model-independent kinetic criterion for glass formation is formulated. As a first consequence, it is shown that it is not-as often claimed-the Deborah number which governs glass formation. Based on this general kinetic criterion for glass formation, general expressions for the dependence of the glass transition temperature on pressure (and vice versa) are obtained being essentially ratios of the partial derivatives of the appropriate relaxation times with respect to pressure and temperature, respectively. Employing, as examples, further two different (free volume and entropy based) models for the description of viscous flow and relaxation, respectively, relations similar but, in general, not identical to the classical Ehrenfest relations describing second-order equilibrium phase transitions are obtained. In this way, it can be explained why one of the Ehrenfest's relations is usually fulfilled in glass transition and the other not and why the Prigogine-Defay ratio in glass transition is not equal to one as this is the case with Ehrenfest's ratio in second-order equilibrium phase transitions. © 2012 American Institute of Physics

  4. Electron anions and the glass transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Lewis E.; Sushko, Peter V.; Tomota, Yudai; Hosono, Hideo

    2016-08-24

    Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca12Al14O32]2+ ∙ (e)2, we demonstrate that electron anions in this system behave as glass-modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. Concentration of such electron anions is a consequential control parameter: it invokes materials evolution pathways and properties not available in conventional glasses, which opens a new avenue in rational materials design.

  5. A density-independent glass transition in biological tissues

    CERN Document Server

    Bi, Dapeng; Schwarz, J M; Manning, M Lisa

    2014-01-01

    Cells must move through tissues in many important biological processes, including embryonic development, cancer metastasis, and wound healing. In these tissues, a cell's motion is often strongly constrained by its neighbors, leading to glassy dynamics. Recent work has demonstrated the existence of a non-equilibrium glass transition in self-propelled particle models for active matter, where the transition is driven by changes in density. However, this may not explain liquid-to-solid transitions in confluent tissues, where there are no gaps between cells and the packing fraction remains fixed and equal to unity. Here we demonstrate the existence of a different type of glass transition that occurs in the well-studied vertex model for confluent tissue monolayers. In this model, the onset of rigidity is governed by changes to single-cell properties such as cell-cell adhesion, cortical tension, and volume compressibility, providing an explanation for a liquid-to-solid transitions in confluent tissues.

  6. Application of Glass Transition in Food Processing.

    Science.gov (United States)

    Balasubramanian, S; Devi, Apramita; Singh, K K; Bosco, S J D; Mohite, Ashish M

    2016-01-01

    The phenomenon of glass transition has been employed to food products to study their stability. It can be applied as an integrated approach along with water activity and physical and chemical changes in food in processing and storage to determine the food stability. Also associated with the changes during agglomeration crystallization, caking, sticking, collapse, oxidation reactions, nonenzymatic browning, and microbial stability of food system. Various techniques such as Differential Scanning Calorimetry, Nuclear Magnetic Resonance, etc. have been developed to determine the glass transition temperature (Tg) of food system. Also, various theories have been applied to explain the concept of Tg and its relation to changes in food system. This review summarizes the understanding of concept of glass transition, its measurement, and application in food technology.

  7. GLASS TRANSITION OF HYDRATED WHEAT GLIADIN POWDERS

    Institute of Scientific and Technical Information of China (English)

    Shao-min Sun; Li Zhao; Yi-hu Song; Qiang Zheng

    2011-01-01

    Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorption ranged from 2.30 db% to 18.21 db%. Glass transition temperature (Tg) of dry wheat gliadin was estimated according to the GordonTaylor equation. Structural heterogeneity at high degrees of hydration was revealed in dielectric temperature and frequency spectra. The activation energies (Ea) of the two relaxations were calculated from Arrhenius equation.

  8. On relaxation nature of glass transition in amorphous materials

    Science.gov (United States)

    Sanditov, Damba S.; Ojovan, Michael I.

    2017-10-01

    A short review on relaxation theories of glass transition is presented. The main attention is paid to modern aspects of the glass transition equation qτg = C, suggested by Bartenev in 1951 (q - cooling rate of the melt, τg - structural relaxation time at the glass transition temperature Tg). This equation represents a criterion of structural relaxation at transition from liquid to glass at T = Tg (analogous to the condition of mechanical relaxation ωτ = 1, where the maximum of mechanical loss is observed). The empirical parameter С = δTg has the meaning of temperature range δTg that characterizes the liquid-glass transition. Different approaches of δTg calculation are reviewed. In the framework of the model of delocalized atoms a modified kinetic criterion of glass transition is proposed (q/Tg)τg = Cg, where Cg ≅ 7·10-3 is a practically universal dimensionless constant. It depends on fraction of fluctuation volume fg, which is frozen at the glass transition temperature Cg = fg/ln(1/fg). The value of fg is approximately constant fg ≅ 0.025. At Tg the process of atom delocalization, i.e. its displacement from the equilibrium position, is frozen. In silicate glasses atom delocalization is reduced to critical displacement of bridge oxygen atom in Si-O-Si bridge necessary to switch a valence bond according to Muller and Nemilov. An equation is derived for the temperature dependence of viscosity of glass-forming liquids in the wide temperature range, including the liquid-glass transition and the region of higher temperatures. Notion of (bridge) atom delocalization is developed, which is related to necessity of local low activation deformation of structural network for realization of elementary act of viscous flow - activated switch of a valence (bridge) bond. Without atom delocalization (;trigger mechanism;) a switch of the valence bond is impossible and, consequently, the viscous flow. Thus the freezing of atom delocalization process at low temperatures

  9. Review: Pressure-Induced Densification of Oxide Glasses at the Glass Transition

    Science.gov (United States)

    Kapoor, Saurabh; Wondraczek, Lothar; Smedskjaer, Morten M.

    2017-02-01

    Densification of oxide glasses at the glass transition offers a novel route to develop bulk glasses with tailored properties for emerging applications. Such densification can be achieved in the technologically relevant pressure regime of up to 1GPa. However, the present understanding of the composition-structure-property relationships governing these glasses is limited, with key questions, e.g., related to densification mechanism, remaining largely unanswered. Recent advances in structural characterization tools and high-pressure apparatuses have prompted new research efforts. Here, we review this recent progress and the insights gained in the understanding of the influence of isostatic compression at elevated temperature (so-called hot compression) on the composition-structure-property relationships of oxide glasses. We focus on compression at temperatures at or around the glass transition temperature (Tg), with relevant comparisons made to glasses prepared by pressure quenching and cold compression. We show that permanent densification at 1 GPa sets-in at temperatures above 0.7Tg and the degree of densification increases with increasing compression temperature and time, until attaining an approximately constant value for temperatures above Tg. For glasses compressed at the same temperature/pressure conditions, we demonstrate direct relations between the degree of volume densification and the pressure-induced change in micro-mechanical properties such as hardness, elastic moduli, and extent of the indentation size effect across a variety of glass families. Furthermore, we summarize the results on relaxation behavior of hot compressed glasses. All the pressure-induced changes in the structure and properties exhibit strong composition dependence. The experimental results highlight new opportunities for future investigation and identify research challenges that need to be overcome to advance the field.

  10. Predicting glass transition temperatures of polyarylethersulphones using QSPR methods.

    Directory of Open Access Journals (Sweden)

    Ian Hamerton

    Full Text Available The technique of Quantitative Structure Property Relationships has been applied to the glass transition temperatures of polyarylethersulphones. A general equation is reported that calculates the glass transition temperatures with acceptable accuracy (correlation coefficients of between 90-67%, indicating an error of 10-30% with regard to experimentally determined values for a series of 42 reported polyarylethersulphones. This method is quite simple in assumption and relies on a relatively small number of parameters associated with the structural unit of the polymer: the number of rotatable bonds, the dipole moment, the heat of formation, the HOMO eigenvalue, the molar mass and molar volume. For smaller subsets of the main group (based on families of derivatives containing different substituents the model can be simplified further to an equation that uses the volume of the substituents as the principal variable.

  11. 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.

  12. The glass transition of hard spherical colloids

    Energy Technology Data Exchange (ETDEWEB)

    Pusey, P.N. (Royal Signals and Radar Establishment, Malvern (UK)); Van Megen, W. (Royal Melbourne Inst. of Tech. (Australia). Dept. of Applied Physics)

    1990-03-01

    When suspended in a liquid, hard spherical colloidal particles can show fluid, crystalline and glassy phases. A light scattering study of the dynamics of the metastable fluid and glassy phases is reported. Comparison is made with the predictions of mode-coupling theories applied to the glass transition of simple atomic systems. (orig.).

  13. 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

  14. PREFACE: Statistical Physics of Ageing Phenomena and the Glass Transition

    Science.gov (United States)

    Henkel, Malte; Pleimling, Michel; Sanctuary, Roland

    2006-06-01

    A summer school on `Ageing and the glass transition' was held at the University of Luxembourg on 18-24 September 2005. It brought together about 60 scientists actively studying the related fields of physical ageing and of the thermodynamics of glass-forming systems when undergoing a glass transition. The programme of the school can be found on the homepage ( http://www.theorie1.physik.uni-erlangen.de/sommerschule.html). The school contained both invited lectures and contributed talks and posters. This volume presents the works contributed to the summer school, while the invited lectures will be published elsewhere (M Henkel, M Pleimling and R Sanctuary (eds), Ageing and the glass transition, Springer Lecture Notes in Physics, Springer (Heidelberg 2006)). We have tried to encourage the exchange between theorists and experimentalists to which the topics treated in these proceedings bear witness. They range from experimental studies on the mechanical response of glasses, biopolymers, and granular materials to the effects of ageing on the long-time modification of the properties of glass-forming polymers, from simulational and analytical studies of theoretical models describing the non-equilibrium statistical mechanics of systems displaying the dynamical scaling typical of ageing phenomena and which are thought to capture essential aspects of glass-forming materials close to a glass transition to more mathematically oriented investigations on the symmetries of these systems. The `Grande Région' Sar-Lor-Lux is leading European efforts to overcome national and linguistic barriers, with the view of creating a common academic education. Physics has a standing internationalist tradition and the existing trinational integrated course in Physics SLLS (see the homepage http://www.uni-saarland.de/fak7/krueger/integ/sll/d/cursus.htm) is busily developing ways and means towards this goal, in particular through the delivery of multinational and multilingual university degrees in

  15. Equivalence of glass transition and colloidal glass transition in the hard-sphere limit.

    Science.gov (United States)

    Xu, Ning; Haxton, Thomas K; Liu, Andrea J; Nagel, Sidney R

    2009-12-11

    We show that the slowing of the dynamics in simulations of several model glass-forming liquids is equivalent to the hard-sphere glass transition in the low-pressure limit. In this limit, we find universal behavior of the relaxation time by collapsing molecular-dynamics data for all systems studied onto a single curve as a function of T/p, the ratio of the temperature to the pressure. At higher pressures, there are deviations from this universal behavior that depend on the interparticle potential, implying that additional physical processes must enter into the dynamics of glass formation.

  16. Mutarotational kinetics and glass transition of lactose

    Science.gov (United States)

    Lefort, Ronan; Caron, Vincent; Willart, Jean-François; Descamps, Marc

    2006-11-01

    We report for the first time real time in situ and quantitative measurements of the mutarotation reaction of lactose in the solid state. The experiments have been performed by 13C NMR. We show that mutarotation is initiated on heating the amorphous state, and reaches chemical equilibrium close above the glass transition temperature Tg. We do not observe this transformation when starting from stable crystalline states. The final ratio of α and β anomers is 1:1, which suggests that the energy profile of the mutarotation reaction pathway in the solid state is actually different from the mechanism proposed for aqueous solution. This chemical equipartition is reached before the crystallization into the corresponding 1:1 molecular compound. These new data clearly illustrate the interrelation between the chemical molecular properties, the physical state of the material, and the relaxational dynamics of the glass.

  17. Chiral-glass transition and replica symmetry breaking of a three-dimensional heisenberg spin glass

    Science.gov (United States)

    Hukushima; Kawamura

    2000-02-01

    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 of a peculiar type of replica-symmetry breaking in the chiral-glass ordered state.

  18. Scaling and universality in glass transition

    Science.gov (United States)

    de Candia, Antonio; Fierro, Annalisa; Coniglio, Antonio

    2016-05-01

    Kinetic facilitated models and the Mode Coupling Theory (MCT) model B are within those systems known to exhibit a discontinuous dynamical transition with a two step relaxation. We consider a general scaling approach, within mean field theory, for such systems by considering the behavior of the density correlator and the dynamical susceptibility  - 2. Focusing on the Fredrickson and Andersen (FA) facilitated spin model on the Bethe lattice, we extend a cluster approach that was previously developed for continuous glass transitions by Arenzon et al. (Phys. Rev. E 90, 020301(R) (2014)) to describe the decay to the plateau, and consider a damage spreading mechanism to describe the departure from the plateau. We predict scaling laws, which relate dynamical exponents to the static exponents of mean field bootstrap percolation. The dynamical behavior and the scaling laws for both density correlator and dynamical susceptibility coincide with those predicted by MCT. These results explain the origin of scaling laws and the universal behavior associated with the glass transition in mean field, which is characterized by the divergence of the static length of the bootstrap percolation model with an upper critical dimension dc = 8.

  19. Fast Heterogeneous Relaxation Near The Glass Transition

    Science.gov (United States)

    Russina, Margarita

    2000-03-01

    More than a decade ago inelastic neutron scattering studies revealed a surprising characteristic feature in the atomic dynamics near the glass transition, which was often called the betta-process, with reference to predictions of the mode coupling theory (MCT). This process appears on the ps time scale, i.e. fast compared to the ordinary flow viscosity governed relaxation and slow compared to usual atomic vibrations, and its nature remained a puzzle over the years. Although inelastic neutron scattering is ideally suited to observe dynamics on microscopic time and length scales, experimental difficulties due to strong multiple scattering effects prevented the exploration of the spatial character of this process. By a new experimental approach to correct for these spurious contributions with a high precision, we were now able to extend the spatial domain of our observations from just about nearest neighbor atomic distances by close to an order of magnitude larger ones, which length scale includes that of the intermediate range order, which can be expected to reveal most sensitively collective, as opposed to the local, behavior. Our results in the fragile glass forming liquid Ca-K-NO3 show, that the betta-process is a first fast step of the structural relaxation, which confirms a most fundamental prediction of MCT. Furthermore, by investigating the Debye-Waller factor associated with this process, we found that its geometrical nature corresponds to quasi-rigid, correlated displacement of mobile groups of atoms, which move much faster than the ordinary flow of the bulk of the supercooled liquid. This is the first direct experimental evidence for the existence of heterogeneous fast flow processes similar to the string-flow motion recently observed in molecular dynamic simulations of model liquids close to the glass transition.

  20. Configurons: Thermodynamic Parameters and Symmetry Changes at Glass Transition

    Directory of Open Access Journals (Sweden)

    Michael I. Ojovan

    2008-09-01

    Full Text Available Thermodynamic parameters of configurons – elementary excitations resulting from broken bonds in amorphous materials – are found from viscosity-temperature relationships. Glass-liquid transition phenomena and most popular models are described along with the configuron model of glass transition. The symmetry breaking, which occurs as a change of Hausdorff dimension of bonds, is examined at glass-liquid transition. Thermal history effects in the glass-liquid transition are interpreted in terms of configuron relaxation.

  1. Volume changes in glass induced by an electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Gavenda, Tadeáš, E-mail: gavendat@vscht.cz [Department of Glass and Ceramics, Institute of Chemical Technology, Technická 5, CZ-166 28 Prague (Czech Republic); Gedeon, Ondrej [Department of Glass and Ceramics, Institute of Chemical Technology, Technická 5, CZ-166 28 Prague (Czech Republic); Jurek, Karel [Institute of Physics, Academy of the Czech Republic, Na Slovance 2, CZ-182 21 Prague (Czech Republic)

    2014-03-01

    Three glasses (float, borosilicate float and Schott D263 glasses) were irradiated by 50 keV electron beams with doses within the range of 0.21–318.5 kC/m{sup 2}. Volume changes induced by electron bombarding were monitored by means of Atomic Force Microscopy. Incubation doses, related to mobility of alkali ions, were measured. Low doses showed compaction of all glasses while higher doses revealed volume inflation, except for borosilicate float glass. Both surfaces of float glass were irradiated and significant differences between them were found.

  2. Volume changes in glass induced by an electron beam

    Science.gov (United States)

    Gavenda, Tadeáš; Gedeon, Ondrej; Jurek, Karel

    2014-03-01

    Three glasses (float, borosilicate float and Schott D263 glasses) were irradiated by 50 keV electron beams with doses within the range of 0.21-318.5 kC/m2. Volume changes induced by electron bombarding were monitored by means of Atomic Force Microscopy. Incubation doses, related to mobility of alkali ions, were measured. Low doses showed compaction of all glasses while higher doses revealed volume inflation, except for borosilicate float glass. Both surfaces of float glass were irradiated and significant differences between them were found.

  3. Intermolecular forces and the glass transition.

    Science.gov (United States)

    Hall, Randall W; Wolynes, Peter G

    2008-01-17

    Random first-order transition theory is used to determine the role of attractive and repulsive interactions in the dynamics of supercooled liquids. Self-consistent phonon theory, an approximate mean field treatment consistent with random first-order transition theory, is used to treat individual glassy configurations, whereas the liquid phase is treated using common liquid-state approximations. Free energies are calculated using liquid-state perturbation theory. The transition temperature, T*A, the temperature where the onset of activated behavior is predicted by mean field theory; the lower crossover temperature, T*C, where barrierless motions actually occur through fractal or stringy motions (corresponding to the phenomenological mode coupling transition temperature); and T*K, the Kauzmann temperature (corresponding to an extrapolated entropy crisis), are calculated in addition to T*g, the glass transition temperature that corresponds to laboratory cooling rates. Relationships between these quantities agree well with existing experimental and simulation data on van der Waals liquids. Both the isobaric and isochoric behavior in the supercooled regime are studied, providing results for DeltaCV and DeltaCp that can be used to calculate the fragility as a function of density and pressure, respectively. The predicted variations in the alpha-relaxation time with temperature and density conform to the empirical density-temperature scaling relations found by Casalini and Roland. We thereby demonstrate the microscopic origin of their observations. Finally, the relationship first suggested by Sastry between the spinodal temperature and the Kauzmann temperatures, as a function of density, is examined. The present microscopic calculations support the existence of an intersection of these two temperatures at sufficiently low temperatures.

  4. Effect of Heating Rate on Glass Foaming: Transition to Bulk Foam

    Energy Technology Data Exchange (ETDEWEB)

    Hrma, Pavel R.

    2009-02-15

    Foaming of glass is an undesirable side effect of glass fining. According to a recent experimental study, the gas-phase volume in the melt heated at a constant rate dramatically increased with an increased rate of heating. This observation indicates that an increased rate of heating (a natural consequence of the increased processing rate experienced as a result of transition to oxy-fuel firing) may exert a substantial influence on glass foaming in advanced glass-melting furnaces. This paper attributes this effect to the change of mode of foam formation in response to an increased rate of heating.

  5. The Glass Transition of Driven Molecular Materials

    Science.gov (United States)

    Descamps, M.; Willart, J. F.; Aumelas, A.

    2008-02-01

    There are many cases of practical interest where materials are maintained in nonequilibrium conditions by some external dynamical forcing: typical examples of these driven materials are provided by irradiation, grinding, extrusion…Contrary to usual phase transitions which are properly addressed by thermal equilibrium states, equilibrium and irreversible thermodynamics, no such general framework is available for driven systems. The purpose of this paper is to show some examples of phase transformations in driven molecular materials. These materials are considered because they are extremely sensitive to external disturbances and are generally very good glass formers. This allows investigating more easily a broad range of the parameters which possibly influence the nature of the end product. We will examine mainly the effect of grinding. Contrary to other materials, metals or minerals, systematic investigations of transformations induced by grinding of molecular materials have not yet been done despite the practical and fundamental interests of such investigations in pharmaceutical and agro-chemical science. We will address several modes of interconversions between crystalline and glassy states of the same compound. We will further discuss specific processing effects on the physical state of the glass itself. It will be shown from these investigations that rationalization and possibilities of prediction are emerging. The use of effective temperature concepts to describe the end product of milling will be discussed. These findings may be of general concern for driven materials of any chemical nature.

  6. Predicting Glass Transition Temperature of Polyethylene/Graphene Nanocomposites by Molecular Dynamic Simulation

    Institute of Scientific and Technical Information of China (English)

    SHENG Yan-zhen; YANG Hua; LI Jun-yin; SUN Miao

    2013-01-01

    The glass transition temperature of polyethylene/graphene nanocomposites was investigated by molecular dynamic simulation.The specific volumes of three systems(polyethylene,polyethylene with a small graphene sheet and two small graphene sheets) were examined as a function of temperature.We found that the glass transition temperature decreases with increasing graphene.Then the van der Waals energy changes obviously with increasing graphene and the torsion energy also plays an important role in the glass transition of polymer.The radial distribution functions of the inter-molecular carbon atoms suggest the interaction between PE and graphene weakens with increasing graphene.These indicate that graphene can prompt the motion of chain segments of polymer and decrease the glass transition temperature (Tg) of polymer.

  7. Glass Property Data and Models for Estimating High-Level Waste Glass Volume

    Energy Technology Data Exchange (ETDEWEB)

    Vienna, John D.; Fluegel, Alexander; Kim, Dong-Sang; Hrma, Pavel R.

    2009-10-05

    This report describes recent efforts to develop glass property models that can be used to help estimate the volume of high-level waste (HLW) glass that will result from vitrification of Hanford tank waste. The compositions of acceptable and processable HLW glasses need to be optimized to minimize the waste-form volume and, hence, to save cost. A database of properties and associated compositions for simulated waste glasses was collected for developing property-composition models. This database, although not comprehensive, represents a large fraction of data on waste-glass compositions and properties that were available at the time of this report. Glass property-composition models were fit to subsets of the database for several key glass properties. These models apply to a significantly broader composition space than those previously publised. These models should be considered for interim use in calculating properties of Hanford waste glasses.

  8. Cooperative rearranging region size and free volume in As-Se glasses.

    Science.gov (United States)

    Saiter, A; Saiter, J-M; Golovchak, R; Shpotyuk, M; Shpotyuk, O

    2009-02-18

    Glasses of the As-Se system have been used as model objects of the covalent disordered inorganic polymers to investigate the correlation between the cooperative rearranging region (CRR) size determined at the glass transition temperature and the free volume fraction in the glassy state. The CRR size has been determined using temperature modulated differential scanning calorimetry data according to Donth's approach, while the free volume fraction in the investigated materials has been estimated using positron annihilation lifetime spectroscopy data. The obtained results testify that the appearance of open-volume defects greater than 80 Å(3) leads to a significant decrease in the CRR size.

  9. Cooperative rearranging region size and free volume in As-Se glasses

    Energy Technology Data Exchange (ETDEWEB)

    Saiter, A; Saiter, J-M [Laboratoire PBM, UMR 6522, LECAP, Institut des Materiaux de Rouen, Universite de Rouen, Faculte des Sciences, Avenue de l' Universite BP 12, 76801 Saint Etienne du Rouvray (France); Golovchak, R; Shpotyuk, M; Shpotyuk, O [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska street, Lviv, UA-79031 (Ukraine)

    2009-02-18

    Glasses of the As-Se system have been used as model objects of the covalent disordered inorganic polymers to investigate the correlation between the cooperative rearranging region (CRR) size determined at the glass transition temperature and the free volume fraction in the glassy state. The CRR size has been determined using temperature modulated differential scanning calorimetry data according to Donth's approach, while the free volume fraction in the investigated materials has been estimated using positron annihilation lifetime spectroscopy data. The obtained results testify that the appearance of open-volume defects greater than 80 A{sup 3} leads to a significant decrease in the CRR size.

  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.

  11. Irreversible transitions in the exchange-striction model of spin-glass state

    Science.gov (United States)

    Valkov, V. I.; Golovchan, A. V.

    2014-08-01

    Based on the assumption of a negative volume dependence of random exchange integrals, it is possible to switch to a compressible Sherrington-Kirkpatrick spin-glass model. Within the proposed model, temperature-pressure phase diagrams were calculated and pressure- and magnetic-field-induced first-order phase transitions from the initial paramagnetic and spin-glass states to the ferromagnetic state were predicted. It was shown that the application of pressure in the spin-glass state not only increases and shifts magnetic susceptibility, but also reduces the critical magnetic fields of irreversible induced phase transitions from the spin-glass to the ferromagnetic state. The obtained results are used to describe the spin-glass state in (Sm1-xGdx)0.55Sr0.45MnO3.

  12. Glass transition of ionic liquids under high pressure

    Science.gov (United States)

    Ribeiro, Mauro C. C.; Pádua, Agílio A. H.; Gomes, Margarida F. Costa

    2014-06-01

    The glass transition pressure at room temperature, pg, of six ionic liquids based on 1-alkyl-3-methylimidazolium cations and the anions [BF4]-, [PF6]-, and bis(trifluromethanesulfonyl)imide, [NTf2]-, has been obtained from the pressure dependence of the bandwidth of the ruby fluorescence line in diamond anvil cells. Molar volume, Vm(pg), has been estimated by a group contribution model (GCM) developed for the ionic liquids. A density scaling relation, TVγ, has been considered for the states Vm(pg, 295 K) and Vm(Tg, 0.1 MPa) using the simplifying condition that the viscosity at the glass transition is the same at pg at room temperature and at atmospheric pressure at Tg. Assuming a constant γ over this range of density, a reasonable agreement has been found for the γ determined herein and that of a previous density scaling analysis of ionic liquids viscosities under moderate conditions. Further support for the appropriateness of extrapolating the GCM equation of state to the GPa pressure range is provided by comparing the GCM and an equation of state previously derived in the power law density-scaling regime.

  13. 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.

  14. Thermodynamic signature of the dynamic glass transition in hard spheres.

    Science.gov (United States)

    Hermes, Michiel; Dijkstra, Marjolein

    2010-03-17

    We use extensive event-driven molecular dynamics simulations to study the thermodynamic, structural and dynamic properties of hard-sphere glasses. We determine the equation of state of the metastable fluid branch for hard spheres with a size polydispersity of 10%. Our results show a clear jump in the slope of the isothermal compressibility. The observation of a thermodynamic signature at the transition from a metastable fluid to a glassy state is analogous to the abrupt change in the specific heat or thermal expansion coefficient as observed for molecular liquids at the glass transition. The dynamic glass transition becomes more pronounced and shifts to higher densities for longer equilibration times.

  15. 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.

  16. Stochastic qualifier of gel and glass transitions in laponite suspensions

    Science.gov (United States)

    Shayeganfar, F.; Jabbari-Farouji, S.; Movahed, M. Sadegh; Jafari, G. R.; Tabar, M. Reza Rahimi

    2010-06-01

    The existence of the important similarities between gelation and glass transition makes it hard to distinguish between the two types of nonergodic states experimentally. Here, we report on a stochastic analysis of the scattered light intensity through a colloidal particles suspension during the gel and glass formation. In this analysis, we exploit the methods developed for complex hierarchical systems, such as turbulence. Using the multiplicative log-normal cascade models, we provide a criterion to distinguish gels from glasses.

  17. Relationship Between Free Volume and Glass Transition Temperature of Zr50Cu50 Metallic Glasses Based on Molecular Dynamics Simulation%Zr50Cu50金属玻璃形成过程中自由体积与玻璃态转变温度关系的分子动力学模拟

    Institute of Scientific and Technical Information of China (English)

    党一纵; 王鲁; 范群波

    2012-01-01

    Atomic structure evolution and diffusivity during the cooling of Zr5oCu50 metallic liquid are studied by molecular dynamics (MD) simulation. Based on the theory that free volume is equal to the volume difference between the amorphous materials and their crystalline counterpart, a new method of annihilating rate of free volume has been developed and applied to predict the critical microscopic glass transition temperature. The predicted critical temperature Tc was 969. 5 K, which is close to the MCT(mode-coupling theory) value of 978. 4 K, and the caloric glass transition temperature Tg was 731 K, which is also close to the value of 725 K determined from the curve of average atomic volume with temperature. Without calculation of diffusion coefficients at a serial of specified temperatures, the developed method is more convenient than former methods to calculate Tc and Tg.%利用分子动力学模拟了Zr50Cu50金属玻璃的形成过程,并获得了不同温度下合金的原子构型.借助金属玻璃中自由体积量等于金属玻璃与对应晶体的体积差理论提出一种自由体积湮没速度法,对Zr50Cu50金属玻璃形成过程中的临界玻璃态转变温度Tc以及热力学玻璃态转变温度Tg进行预测.用该方法确定出的Tc(969.5 K)与利用模式耦合理论计算获得的Tc (978.4 K)接近;Tg(731 K)与利用平均原子体积随温度变化关系曲线确定的Tg(725 K)相近.运用自由体积湮没速度法计算的Tc和Tg无需计算各温度下的原子扩散系数,节省了计算时间.

  18. 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 well-s

  19. 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)

  20. 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.

  1. Glass transition phenomena applied to powdered amorphous food carbohydrates

    OpenAIRE

    Ronkart, Sebastien N; Blecker, Christophe; Deroanne, Claude; Paquot, Michel

    2009-01-01

    Glass transition phenomena applied to powdered amorphous food carbohydrates. During these last fifteen years, some food technologists and scientists have become aware of the importance of the glass transition, a thermal property of glassy or amorphous material, in food preparation processes. Recent studies have successfully correlated this fundamental notion to technofunctional changes within the powder. The aim of this paper is to present in a non exhaustive manner the relationship between g...

  2. Testing the paradigms of the glass transition in colloids via dynamic simulation

    Science.gov (United States)

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

    2016-11-01

    Upon cooling, molecular glass-formers undergo a glass transition during which viscosity appears to diverge, and the material transitions from a liquid to an amorphous solid. However, the new state is not an equilibrium phase: material properties such as enthalpy continue to evolve in time. Rather, the material evolves toward an "intransient" state, as measured by the Kovacs signature experiments, e.g. the intrinsic isotherm, which reveals a paradoxical dependence of transition time on quench depth, and suggests that whether the glass transition occurs at the beginning or end of this transition is an open question. Colloidal glass formers provide a natural way to model such behavior, owing to the disparity in time scales that allow tracking of particle dynamics. We interrogate these ideas via dynamic simulation of a hard-sphere colloidal glassy state induced by jumps in volume fraction. We explore three methods to model the jump: evaporation, aspiration, and particle-size jumps. During and following each jump, the positions, velocities, and particle-phase stress are tracked and utilized to characterize relaxation time scales and structural changes. Analogs for the intrinsic isotherms are developed. The results provide insight into the existence of an "ideal" glass transition.

  3. Theoretical Insights from Facile Microsecond Simulation of the Glass Transition

    Science.gov (United States)

    Hung, Jui-Hsiang; Patra, Tarak; Simmons, David

    Despite more than half a century of research, the fundamental nature of the glass transition remains one of the major open questions in polymer science and condensed matter physics. Molecular dynamics simulations have provided key insights into this problem, but their ability to firmly establish the underlying nature of glass formation have been limited by the extreme computational difficulty of directly probing the deeply supercooled regime most relevant to this process. Here we describe a new protocol for simulation of the glass transition enabling facile access to in-equilibrium segmental relaxation times approaching and exceeding one microsecond - well into the deeply supercooled regime of most glass-forming liquids. Coupled with a well-validated strategy for extrapolation to experimental timescales, this approach provides vastly improved prediction of experimental glass transition temperatures. Here we combine data acquired through this protocol for the deeply supercooled regime of polymeric, inorganic, organic, and metallic glass formers to robustly test several theories of glass formation and identify microscopic phenomenological features shared across all classes of glass-forming liquid in the deeply supercooled regime. We acknowledge the W. M. Keck Foundation for financial support of this research.

  4. DWPF Glass Melter Technology Manual: Volume 4

    Energy Technology Data Exchange (ETDEWEB)

    Iverson, D.C.

    1993-12-31

    This document details information about the design of a glass melter to be used at the Defense Waste Processing Facility located at the Savannah River Plant. Information contained in this document consists solely of a machine drawing and parts list and purchase orders with specifications of equipment used in the development of the melter.

  5. DWPF Glass Melter Technology Manual: Volume 3

    Energy Technology Data Exchange (ETDEWEB)

    Iverson, D.C.

    1993-12-31

    This document details information about the design of a glass melter to be used at the Defense Waste Processing Facility located at the Savannah River Site. Topics discussed include: Information collected during testing, equipment, materials, design basis, feed tubes, and an evaluation of the performance of various components. Information is conveyed using many diagrams and photographs.

  6. From Gelation and Glass Transition of Colloidal Systems to Polymers

    Science.gov (United States)

    Han, Charles; Yuan, Guangcui; Cheng, He

    Charles C. Han, Guangcui Yuan and He Cheng Joint Laboratory of Polymer Science and Materials, ICCAS, Beijing, China and Institute for Advanced Study, Shenzhen University, Shenzhen, China Aggregation and gelation behavior of mixed suspensions of polystyrene microspheres and poly(N-isopropylacrylamide) microgels have been studied. In dilute microsphere suspensions, with increasing concentration of microgel (MG), microspheres (MS) first aggregated with each other through the bridging of the microgels, then dispersed individually when saturated adsorption was achieved, and finally depletion clusters formed at even higher concentrations of microgel. In concentrated microsphere suspensions, with saturated MG adsorption, a state transition from attractive glass to repulsive glass can be observed. This type of system can be viewed as a molecular model system which has a long range repulsive interaction potential and a short range attractive potential. A comparison between the glass transition of the colloidal systems and the glass transition of polymeric systems can be made.

  7. Transit Scratchitti Removal and Glass Resurfacing by Controlled Fire Polishing

    Science.gov (United States)

    Jun, Seongchan; Hong, Shane Y.

    Scratchitti vandalism, a new type of graffiti vandalism, in public transits systems and city neighborhood is a serious problem. To solve this problem, an innovative approach was developed-controlled fire polishing, which incorporates a technique of localized softening and surface tension. Intensive heat is positioned near to the scratch marks on the glass panel. The heat melts a thin layer of glass into liquid, changing the glass’s viscosity to a formable state. The glass is melted to a level close to the depth of the scratch, and allowed to cool down naturally. During the cooling process, the surface tension of the melted glass will even out the scratching indent. After cooling, the glass will be as even and smooth as it was originally. The process will enable the reuse of the damaged window/door and eliminate the otherwise waste by replacement new glass.

  8. 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.

  9. Spin-glass transition of the three-dimensional Heisenberg spin glass.

    Science.gov (United States)

    Campos, I; Cotallo-Aban, M; Martin-Mayor, V; Perez-Gaviro, S; Tarancon, A

    2006-11-24

    It is shown, by means of Monte Carlo simulation and finite size scaling analysis, that the Heisenberg spin glass undergoes a finite-temperature phase transition in three dimensions. There is a single critical temperature, at which both a spin glass and a chiral glass ordering develop. The Monte Carlo algorithm, adapted from lattice gauge theory simulations, makes it possible to thermalize lattices of size L = 32, larger than in any previous spin-glass simulation in three dimensions. High accuracy is reached thanks to the use of the Marenostrum supercomputer. The large range of system sizes studied allows us to consider scaling corrections.

  10. Volume Phase Masks in Photo-Thermo-Refractive Glass

    Science.gov (United States)

    2014-10-06

    2014 Approved for public release; distribution is unlimited. Volume phase masks in photo- thermo -refractive glass The views, opinions and/or findings...in photo- thermo -refractive glass Report Title In many applications such as beam shaping, mode conversion, and phase encoding it is necessary to alter...requiring a new means of producing phase masks. In this dissertation a method for producing robust phase masks in the bulk of photo- thermo - refractive

  11. DWPF Glass Melter Technology Manual: Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Iverson, D.C.

    1993-12-31

    This document details information about the design of a glass melter to be used at the Defense Waste Processing Facility located at the Savannah River Site. Topics include: melter overview, design basis, materials, vessel configuration, insulation, refractory configuration, electrical isolation, electrodes, riser and pour spout heater design, dome heaters, feed tubes, drain valves, differential pressure pouring, and melter test results. Information is conveyed using many diagrams and photographs.

  12. Understanding ductile-to-brittle transition of metallic glasses from shear transformation zone dilatation

    Directory of Open Access Journals (Sweden)

    M.Q. Jiang

    2015-08-01

    Full Text Available A theoretical model that takes into account the free-volume aided cooperative shearing of shear transformation zones (STZs is developed to quantitatively understand the ductile-to-brittle transition (DBT of metallic glasses. The STZ dilatational strain is defined as the ratio of STZ-activated free volume to STZ volume itself. The model demonstrates that the STZ dilatational strain will increase drastically and exceed the characteristic shear strain of STZ as temperature decreases below a critical value. This critical temperature is in good agreement with the experimentally measured DBT temperature. Our results suggest that the DBT of metallic glasses is underpinned by the transition of atomic-cluster motions from STZ-type rearrangements to dilatational processes (termed tension transformation zones (TTZs.

  13. 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.

  14. Does Glass Size and Shape Influence Judgements of the Volume of Wine?

    Science.gov (United States)

    Pechey, Rachel; Attwood, Angela S; Couturier, Dominique-Laurent; Munafò, Marcus R; Scott-Samuel, Nicholas E; Woods, Andy; Marteau, Theresa M

    2015-01-01

    Judgements of volume may influence the rate of consumption of alcohol and, in turn, the amount consumed. The aim of the current study was to examine the impact of the size and shape of wine glasses on perceptions of wine volume. Online experiment: Participants (n = 360; recruited via Mechanical Turk) were asked to match the volume of wine in two wine glasses, specifically: 1. the Reference glass holding a fixed reference volume, and 2. the Comparison glass, for which the volume could be altered until participants perceived it matched the reference volume. One of three comparison glasses was shown in each trial: 'wider' (20% wider but same capacity); 'larger' (same width but 25% greater capacity); or 'wider-and-larger' (20% wider and 25% greater capacity). Reference volumes were 125 ml, 175 ml and 250 ml, in a fully factorial within-subjects design: 3 (comparison glass) x 3 (reference volume). Non-zero differences between the volumes with which participants filled comparison glasses and the corresponding reference volumes were identified using sign-rank tests. Participants under-filled the wider glass relative to the reference glass for larger reference volumes, and over-filled the larger glass relative to the reference glass for all reference volumes. Results for the wider-and-larger glass showed a mixed pattern across reference volume. For all comparison glasses, in trials with larger reference volumes participants tended to fill the comparison glass less, relative to trials with smaller reference volumes for the same comparison glass. These results are broadly consistent with people using the relative fullness of glasses to judge volume, and suggest both the shape and capacity of wine glasses may influence perceived volume. Perceptions that smaller glasses contain more than larger ones (despite containing the same volume), could slow drinking speed and overall consumption by serving standard portions in smaller glasses. This hypothesis awaits testing.

  15. Frustration in Vicinity of Transition Point of Ising Spin Glasses

    Science.gov (United States)

    Miyazaki, Ryoji

    2013-09-01

    We conjecture the existence of a relationship between frustration and the transition point at zero temperature of Ising spin glasses. The relation reveals that, in several Ising spin glass models, the concentration of ferromagnetic bonds is close to the critical concentration at zero temperature when the output of a function about frustration is equal to unity. The function is the derivative of the average number of frustrated plaquettes with respect to the average number of antiferromagnetic bonds. This relation is conjectured in Ising spin glasses with binary couplings on two-dimensional lattices, hierarchical lattices, and three-body Ising spin glasses with binary couplings on two-dimensional lattices. In addition, the same argument in the Sherrington--Kirkpatrick model yields a point that is identical to the replica-symmetric solution of the transition point at zero temperature.

  16. Structural relaxation time and cooling rate of a melt in the glass transition region

    Science.gov (United States)

    Sanditov, D. S.; Sydykov, B. S.

    2015-03-01

    The nature of the parameter involved in the Bartenev equation qτg = C relating the cooling rate of a glass-forming melt to its structural relaxation time in the glass transition region is discussed on the basis of the Volkenshtein-Ptitsyn theory using a number of known relationships. It is established that parameter C for amorphous substances with the same fragility is linearly temperature dependent. This parameter is shown to equal the narrow temperature range δ T g characterizing the liquid-glass transition region (by Nemilov); i.e., C = δ T g. It is concluded that δ T g for most glassy systems is only ˜0.7% of the glass transition temperature T g. The narrowness of temperature range δ T g is explained by the small fluctuation volume fraction f g "frozen" at the glass transition temperature. The concept of a close relationship between constant C and the structural order at T g (i.e., the characteristic of the inner state of a nonequilibrium "frozen" amorphous system) is developed.

  17. Kinetics of Glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite.Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.

  18. 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.

  19. A NEURAL NETWORK STUDY ON GLASS TRANSITION TEMPERATURE OF POLYMERS

    Institute of Scientific and Technical Information of China (English)

    Lin-xi Zhanga; De-lu Zhao; You-xing Huang

    2002-01-01

    In this paper, an artificial neural network model is adopted to study the glass transition temperature of polymers. In our artificial neural networks, the input nodes are the characteristic ratio C∞, the average molecular weight M, between entanglement points and the molecular weight Mmon of repeating unit. The output node is the glass transition temperature Tg,and the number of the hidden layer is 6. We found that the artificial neural network simulations are accurate in predicting the outcome for polymers for which it is not trained. The maximum relative error for predicting of the glass transition temperature is 3.47%, and the overall average error is only 2.27%. Artificial neural networks may provide some new ideas to investigate other properties of the polymers.

  20. Glass transition and heavy oil dynamics at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Abivin, P.; Indo, K.; Cheng, Y.; Freed, D.; Taylor, S. D. [Schlumberger (Canada)], email: PAbivin@slb.com

    2011-07-01

    In the oil industry, the viscosity of crude oils is a key factor as it affects market value, field developments and the design of production strategies. In heavy oils, a glass transition occurs and previous work related this to oil's temperature-viscosity behavior. This study aimed at better characterizing heavy oil dynamics and the temperature dependency of viscosity. Experiments were conducted with differential scanning calorimetry and shear rate sweeps on heavy oils from Asia, South America and North America over a wide range of temperatures to measure their viscosities and characterize their glass transition. The glass transition was observed at around 210K and results showed that the Arrhenius model does not fit the experimental data at low temperatures but the WLF model does. This research provided a better understanding of heavy oil dynamics but further work is required to explain the viscosity-temperature behavior of heavy oils at low temperatures.

  1. 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.

  2. Structural, optical and glass transition studies on Nd{sup 3+}-doped lead bismuth borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Karthikeyan, B.; Mohan, S

    2003-07-01

    Nd{sup 3+}-doped lead bismuth borate (PbO-Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3}) glasses were prepared with different concentrations of Nd{sup 3+}. The structural studies were done through FTIR spectral analysis. The glass transition studies were done through differential scanning calorimetry. The optical analysis was done by using Judd-Ofelt theory. The structural study reveals that the glass has [BiO{sub 3}], BO{sub 4}, BO{sub 3} and PbO{sub 4} units as the local structures.

  3. Glass transition temperature and conductivity in Li2O and Na2O doped borophosphate glasses

    Science.gov (United States)

    Ashwajeet, J. S.; Sankarappa, T.; Ramanna, R.; Sujatha, T.; Awasthi, A. M.

    2015-08-01

    Two alkali doped Borophosphate glasses in the composition, (B2O3)0.2. (P2O5)0.3. (Na2O)(0.5-x). (Li2O)x, where x = 0.05 to 0.50 were prepared by standard melt quenching method at 1200K. Non-crystalline nature was confirmed by XRD studies. Room temperature density was measured by Archimedes principle. DC conductivity in the temperature range from 300K to 575K has been measured. Samples were DSC studied in the temperature range from 423K to 673K and glass transition temperature was determined. Glass transition temperature passed through minima for Li2O con.2centration between 0.25 and 0.30 mole fractions. Activation energy of conduction has been determined by analyzing temperature variation of conductivity determining Arrhenius law. Conductivity passed through minimum and activation passed through maximum for Li2O content from 0.25 to 0.30 mole fractions. Glass transition temperature passed through minimum for the same range of Li2O content. These results revealed mixed alkali effect taking place in these glasses. It is for the first time borophosphate glasses doped with Li2O and Na2O have been studied for density and dc conductivity and, the mixed alkali effect (MAE) has been observed.

  4. Glass transition in binary eutectic systems: best glass-forming composition.

    Science.gov (United States)

    Wang, Li-Min; Li, Zijing; Chen, Zeming; Zhao, Yue; Liu, Riping; Tian, Yongjun

    2010-09-23

    The glass transition and glass-forming ability in a binary eutectic system of methyl o-toluate (MOT) versus methyl p-toluate (MPT) are studied across the whole composition range. The phase diagram is constructed to explore the best glass-forming composition as the characteristic temperatures of the glass transition, crystallization, eutectic, and liquidus are determined. The best vitrification region is found to locate between the eutectic and the midpoint compositions of the eutectic line, indicating a remarkable deviation from the eutectic composition. The compilation of various simple binary eutectic systems covering inorganic, metallic, ionic, and molecular glass-forming liquids reproduces the rule. Kinetics and thermodynamics in binary systems are investigated to associate with the rule. The composition dependence of the structural relaxation time and the kinetic fragility are presented with dielectric measurements. It is found that whereas mixing of binary miscible liquids kinetically favors glass formation, thermodynamic contribution to the deviation of the best glass-forming composition from eutectics is implied.

  5. QCD Phase Transitions, Volume 15

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, T.; Shuryak, E.

    1999-03-20

    The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.

  6. Is the glass half full or half empty? How to reverse the effect of glass elongation on the volume poured.

    Directory of Open Access Journals (Sweden)

    Simone R Caljouw

    Full Text Available To reduce the volume of drinks and the risk of overconsumption, health professionals recommend the use of tall skinny instead of short wide glasses. Yet the results of the present study contradict this health advice. Participants who generously filled up a glass with lemonade served 9% more in tall narrow compared with short wide glasses (p<0.05. In addition, when pouring a small amount (i.e., a shot, participants poured 3% more in a short wide than in a tall narrow glass (p<0.05. Elongation may bias the perceived volume that is poured but also the perceived volume of the free space in the glass. We hypothesised that shifting attention from the bottom to the brim of the glass when filling it close to capacity might reverse the glass elongation effect on the quantity poured. This hypothesis was tested, by investigating two pouring tasks that differed in the required focus of attention. When the instruction was to match a reference volume, participants poured more liquid in the short wide compared with the tall narrow glass (p<0.05. The effect of glass elongation on poured volume was the opposite when the instruction was to leave space in the glasses for the reference volume. It seems likely that task and individual factors affect the pourer's viewing strategy and thus may determine the direction of the glass elongation effect on the volume poured.

  7. 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.

  8. Thermal and fragility aspects of microwave synthesized glasses containing transition metal ions and heavy metal ions

    Science.gov (United States)

    Renuka, C.; Viswanatha, R.; Reddy, C. Narayana

    2017-02-01

    A simple, clean and energy efficient microwave heating route is used to prepare glasses in the systems xMnO-33(0.09PbCl2:0.91PbO)-(67-x) NaPO3 and xPbCl2-33PbO-(67-x) NaPO3 where 0.1 ≤ x ≤ 4 (mol%). Thermal data extracted from differential scanning calorimetry (DSC) thermograms are used to study the composition dependence of glass transition temperature (Tg), heat capacity, thermal stability and fragility. The decrease in glass transition temperature with modifier oxide (Na2O + MnO) content can be ascribed to network degradation and the volume increasing effect caused by PbCl2. The change in heat capacity of MnPb glass being greater than that of PbNP glass, suggests that MnPb glasses are more covalent than PbNP glasses. DSC thermograms taken at different heating rates (φ) reveal the dependence of Tg on φ, and the thermal stability of the glass increases due to MnO addition. Fragility aspects have also been studied by calculating the fragility functions ( {{Δ {{C}}_{{p}} }/{{{C}_{{pl}} }}{{and}}{[ {{NBO}} ]}/{{{V}_{{m}}3 {{T}}_{{g}} }}} ). Results obtained from both the fragility functions compare well and reveal the dependence of fragility functions on modifier content and PbCl2 mol%. Further, the decrease in Tg and Hv are suggested to be due to the increase in the number of non-bridging oxygens, which results in the lowering of stiffness and rigidity of the glass network. Analysis of the infrared spectra confirms that the glassy matrix is composed of P-O-P, P-O-Pb, P=O and P-O- bonding.

  9. 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.

  10. Electrical Resistance Measurement of Glass Transition and Crystallization Characteristics of Zr-Al-Cu-Ni Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In this paper, glass transition and thermal stability of the Zr-Al-Cu-Ni metallic glasses were investigated by using electrical resistance measurement (ERM), DSC and X-ray diffraction techniques. The experimental results show that the ERM is capable of detecting the glass transition of the amorphous alloys and can help to distinguish the crystallization products of the Zr-Al-Cu-Ni metallic glasses owing to the difference of the electrical resistivity between the precipitation phases.

  11. Understanding the glass transition in GeSbTe materials

    Science.gov (United States)

    Martyna, Glenn

    2010-03-01

    Moore's law demands the continual reduction in size of the components of computers. One future direction for memory technology involves the use of phase change materials which can be switched by pulsed electrically heating from a conducting crystalline phase to an insulating amorphous phase. These materials are typically alloys of Germanium, Antimony and Tellurium (GST). In order to form multi-state bits, it is necessary to arrest the glass transition via varying annealing time such that differences in resistivity can be measured based. As might be expected, this process is hinder by ``creep'' of the glass towards higher resistance states after the quench is halted. In this lecture, simulation studies are employed to study the glass transition from the crystalline state and discern the mechanism for the gap opening. The nature of mid gaps states found from the simulated quenches gives insight into the mechanism of the creep and suggests ways in which the phenomena can be arrested.

  12. Theoretical approaches to the glass transition in simple liquids

    Indian Academy of Sciences (India)

    Chandan Dasgupta

    2005-05-01

    Theoretical approaches to the development of an understanding of the behaviour of simple supercooled liquids near the structural glass transition are reviewed and our work on this problem, based on the density functional theory of freezing and replicated liquid state theory, are summarized in this context. A few directions for further work on this problem are suggested.

  13. Polymer glass transitions switch electron transfer in individual molecules

    NARCIS (Netherlands)

    Siekierzycka, J.R.; Hippius, C.; Würthner, F.; Williams, R.M.; Brouwer, A.M.

    2010-01-01

    Essentially complete photoinduced electron transfer quenching of the fluorescence of a perylene−calixarene compound occurs in poly(methyl acrylate) and poly(vinyl acetate) above their glass transition temperatures (T-g), but the fluorescence is completely recovered upon cooling the polymer matrix to

  14. Predictions of Glass Transition Temperature for Hydrogen Bonding Biomaterials

    NARCIS (Netherlands)

    Sman, van der R.G.M.

    2013-01-01

    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

  15. 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 a

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    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...

  17. 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

  18. Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions

    Science.gov (United States)

    Henderson, Mark

    The goal of this dissertation is to characterize the basic transport properties of phosphate glasses containing various amounts of TIs and to identify and explain any electronic phase transitions which may occur. The P2 O5-V2O5-WO3 (PVW) glass system will be analyzed to find the effect of TI concentration on conduction. In addition, the effect of the relative concentrations of network forming ions (SiO2 and P2O5) on transport will be studied in the P2O5-SiO2-Fe2O 3 (PSF) system. Also presented is a numerical study on a tight-binding model adapted for the purposes of modelling Gaussian traps, mimicking TI's, which are arranged in an extended network. The results of this project will contribute to the development of fundamental theories on the electronic transport in glasses containing mixtures of transition oxides as well as those containing multiple network formers without discernible phase separation. The present study on the PVW follows up on previous investigation into the effect on mixed transition ions in oxide glasses. Past research has focused on glasses containing transition metal ions from the 3d row. The inclusion of tungsten, a 5d transition metal, adds a layer of complexity through the mismatch of the energies of the orbitals contributing to localized states. The data have indicated that a transition reminiscent of a metal-insulator transition (MIT) occurs in this system as the concentration of tungsten increases. As opposed to some other MIT-like transitions found in phosphate glass systems, there seems to be no polaron to bipolaron conversion. Instead, the individual localization parameter for tungsten noticeably decreases dramatically at the transition point as well as the adiabaticity. Another distinctive feature of this project is the study of the PSF system, which contains two true network formers, phosphorous pentoxide (P2O 5) and silicon dioxide (SiO2). It is not usually possible to do a reliable investigation of the conduction properties of

  19. Molecular Dynamics Simulations of a Pressure-induced Glass Transition

    CERN Document Server

    Shumway, S L; Jonsson, H; Shumway, Shelly L.; Clarke, Andrew S.

    1994-01-01

    We simulate the compression of a two-component Lennard-Jones liquid at a variety of constant temperatures using a molecular dynamics algorithm in an isobaric-isothermal ensemble. The viscosity of the liquid increases with pressure, undergoing a broadened transition into a structurally arrested, amorphous state. This transition, like the more familiar one induced by cooling, is correlated with a significant increase in icosahedral ordering. In fact, the structure of the final state, as measured by an analysis of the bonding, is essentially the same in the glassy, frozen state whether produced by squeezing or by cooling under pressure. We have computed an effective hard-sphere packing fraction at the transition, defining the transition pressure or temperature by a cutoff in the diffusion constant, analogous to the traditional laboratory definition of the glass transition by an arbitrary, low cutoff in viscosity. The packing fraction at this transition point is not constant, but is consistently higher for runs c...

  20. AR-Glass Fibre-Cement Interfacial Transition Zone

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure of ITZ (Interfacial Transition Zone) in single glass fibre-cement was investigated by SEM (Scanning Electron Microscope), EPXM (Electron Probe X-ray Microanalyzer) and ESEM (Environmental Scanning Electron Microscope). The surface morphology of glass fibres and the hydration products in the vicinity of the interfaces were observed.Chemical element (Zr, Ca and Si) distributions over the ITZ thickness were determined by line-scanning with EPXM.The results show that a low-density transition zone existed in the vicinity of glass fibres. The shape of the fibre-cement ITZ was non-symmetrical and its thickness was variable. In the present study, the width of the zone ranged from 1-5μm.Locally, it came to 10μm.Occasionally, some hydration products with high alkalinity were embedded inside the ITZ, and attached on the glass surface,making the ITZ denser and causing local glass to corrode.The test results are helpful for the further understanding of the GRC degradation.

  1. Glass transitions in the cellular Potts model

    Science.gov (United States)

    Chiang, M.; Marenduzzo, D.

    2016-10-01

    We study the dynamical transition between a fluid-like and a solid-like phase in a confluent cell monolayer, by using the cellular Potts model and computer simulations. We map out the phase diagram as a function of interfacial tension and of cell motility. While in the fluid phase there is normal diffusion, in the solid phase we observe sub-diffusion, very slow relaxation, and ageing, thereby strongly suggesting that this phase is glassy. Our results complement previous theoretical work within the vertex model and show that the cellular Potts model can account for the experimentally observed glassy dynamics of some biological tissues.

  2. On the nature of the liquid-to-glass transition equation

    Science.gov (United States)

    Sanditov, D. S.

    2016-09-01

    Within the model of delocalized atoms, it is shown that the parameter δ T g , which enters the glasstransition equation qτ g = δ T g and characterizes the temperature interval in which the structure of a liquid is frozen, is determined by the fluctuation volume fraction {f_g} = {( {{{Δ {V_e}} / V _{T = {T_g}}} frozen at the glass-transition temperature T g and the temperature T g itself. The parameter δ T g is estimated by data on f g and T g . The results obtained are in agreement with the values of δ T g calculated by the Williams-Landel-Ferry (WLF) equation, as well as with the product qτ g —the left-hand side of the glass-transition equation ( q is the cooling rate of the melt, and τ g is the structural relaxation time at the glass-transition temperature). Glasses of the same class with f g ≈ const exhibit a linear correlation between δ T g and T g . It is established that the currently used methods of Bartenev and Nemilov for calculating δ T g yield overestimated values, which is associated with the assumption, made during deriving the calculation formulas, that the activation energy of the glass-transition process is constant. A generalized Bartenev equation is derived for the dependence of the glass-transition temperature on the cooling rate of the melt with regard to the temperature dependence of the activation energy of the glasstransition process. A modified version of the kinetic glass-transition criterion is proposed. A conception is developed that the fluctuation volume fraction f = Δ V e / V can be interpreted as an internal structural parameter analogous to the parameter ξ in the Mandelstam-Leontovich theory, and a conjecture is put forward that the delocalization of an active atom—its critical displacement from the equilibrium position—can be considered as one of possible variants of excitation of a particle in the Vol'kenshtein-Ptitsyn theory. The experimental data used in the study refer to a constant cooling rate of q = 0.05 K

  3. Holographic Recording and Applications of Multiplexed Volume Bragg Gratings in Photo-Thermo-Refractive Glass

    Science.gov (United States)

    2014-10-06

    applications of multiplexed volume bragg gratings in photo- thermo -refractive glass Volume Bragg grating (VBG) structures are capable of diffracting...research in the holographic recording of volume Bragg gratings in photo- thermo -refractive (PTR) glass has shown that these gratings are extremely...ABSTRACT Holographic recording and applications of multiplexed volume bragg gratings in photo- thermo -refractive glass Report Title Volume Bragg grating (VBG

  4. Glass and percolation transitions in dense attractive micellar system

    Science.gov (United States)

    Mallamace, F.; Beneduci, R.; Gambadauro, P.; Lombardo, D.; Chen, S. H.

    2001-12-01

    In this work, we study a copolymer-micellar system characterized by clustering processes due to a short-range attractive interaction. This originates a percolation process and a new type of kinetic glass transition. We have studied these intriguing dynamical situations by means of an extensive set of light scattering and viscoelasticity experiments. Obtained data, in both the phenomena, are accounted for by considering in a proper way fractal clustering processes and the related scaling concepts. Near the percolation line the main role in the system structure and dynamics is played by the cluster's partial screening of hydrodynamic interaction, that behaves, on approaching the percolation threshold, dramatic effects on the rheological properties and on the density decay relaxations. The ergodic-nonergodic transition line (glass transition) is studied in terms of the intermediate scattering functions (ISF) in the frame of the mode coupling theory. The measured ISF gives evidence of a logarithmic decay on the density fluctuation followed by a power law behavior. This latter phenomenon is the signature of a high-order glass transition of the A3 type (cusp-like singularity).

  5. Instantaneous Normal Modes and the Protein Glass Transition

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Roland [University of Tennessee, Knoxville (UTK); Krishnan, Marimuthu [ORNL; Daidone, Isabella [University of Heidelberg; Smith, Jeremy C [ORNL

    2009-01-01

    In the instantaneous normal mode method, normal mode analysis is performed at instantaneous configurations of a condensed-phase system, leading to modes with negative eigenvalues. These negative modes provide a means of characterizing local anharmonicities of the potential energy surface. Here, we apply instantaneous normal mode to analyze temperature-dependent diffusive dynamics in molecular dynamics simulations of a small protein (a scorpion toxin). Those characteristics of the negative modes are determined that correlate with the dynamical (or glass) transition behavior of the protein, as manifested as an increase in the gradient with T of the average atomic mean-square displacement at 220 K. The number of negative eigenvalues shows no transition with temperature. Further, although filtering the negative modes to retain only those with eigenvectors corresponding to double-well potentials does reveal a transition in the hydration water, again, no transition in the protein is seen. However, additional filtering of the protein double-well modes, so as to retain only those that, on energy minimization, escape to different regions of configurational space, finally leads to clear protein dynamical transition behavior. Partial minimization of instantaneous configurations is also found to remove nondiffusive imaginary modes. In summary, examination of the form of negative instantaneous normal modes is shown to furnish a physical picture of local diffusive dynamics accompanying the protein glass transition.

  6. 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...

  7. Direct Measurement of the Pressure Dependence of the Glass Transition Temperature: A Comparison of Methods

    Science.gov (United States)

    Oliver, William, III; Ransom, Timothy; Cooper, James, III

    2013-03-01

    Two methods for the direct measurement of the pressure dependence of the glass-transition temperature Tg are presented and compared. These methods involve the use of the diamond anvil cell (DAC), and hence, enable the ability to measure Tg(P) to record high pressures of several GPa. Such studies are increasingly relevant as new methods have pushed other high-pressure experimental investigations of glass-forming systems into the same pressure regime. Both methods use careful ruby fluorescence measurements in the DAC as temperature is increased from the glass (TTg) . Method 1 observes the disappearance of pressure gradients as the viscous liquid region is entered, whereas method 2 involves observation of slope changes in the P-T curve during temperature ramps. Such slope changes are associated with the significant change in the volume expansion coefficient between the highly viscous, metastable, supercooled liquid state and the solid glassy state. In most cases, the two methods yield good agreement in the Tg(P) curve. Data will be presented for more than one glass-forming system, including the intermediate strength glass-forming system glycerol and the fragile glass former salol. We acknowledge support from the NSF under DMR-0552944

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

    CERN Document Server

    Bi, Dapeng; Marchetti, M Cristina; Manning, M Lisa

    2015-01-01

    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 demonstrat...

  9. 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

  10. 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 Arrh...... Arrhenius temperature dependence. The same behavior is found for four other viscous liquids, indicating that the phenomenon is possibly general....

  11. Motility-Driven Glass and Jamming Transitions in Biological Tissues

    Science.gov (United States)

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

    2016-04-01

    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 model that simultaneously captures polarized cell motility and multibody 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 solidlike state to a fluidlike 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.

  12. Heat capacities and glass transitions of ion gels.

    Science.gov (United States)

    Yamamuro, Osamu; Someya, Takenori; Kofu, Maiko; Ueki, Takeshi; Ueno, Kazuhide; Watanabe, Masayoshi

    2012-09-06

    We have investigated thermodynamic properties of ion gels consisting of a PMMA [poly(methyl methacrylate)] network and EMITFSI [1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide] ionic liquid by means of an adiabatic calorimeter. The heat capacity data were measured in the temperature range between 5 and 375 K for 7 samples with x = 0 (pure PMMA), 0.10, 0.18, 0.27, 0.48, 0.65, and 1.0 (pure ionic liquid) where x is a mole fraction of EMITFSI. These data revealed that two broad but distinct glass transitions appeared in the low x region. The upper glass transition is mainly due to the freezing of the PMMA motion, while the lower one is due to the ionic liquid. The upper glass transition temperature T(g) drastically decreased with increasing x, reflecting a large plasticization effect observed in mechanical experiments. The x dependence of the T(g)s and the excess heat capacities gave new physical insight to the interaction between polymer and ionic liquid in ion gels.

  13. The glass-liquid transition of water on hydrophobic surfaces.

    Science.gov (United States)

    Souda, Ryutaro

    2008-09-28

    Interactions of thin water films with surfaces of graphite and vitrified room-temperature ionic liquid [1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)])] were investigated using time-of-flight secondary ion mass spectrometry as a function of temperature and annealing time to elucidate the glass-liquid transition of water at the molecular level. Surface diffusion of water occurs at temperatures higher than 120 K, thereby forming three-dimensional clusters (a two-dimensional layer) on the [bmim][PF(6)] (graphite) surface. The hydrophobic effect of the surface decreases with increasing coverage of water; the bulklike properties evolve up to 40 ML, as evidenced by the occurrence of film dewetting at around the conventional glass transition temperature (140 K). Results also showed that aging is necessary for the water monolayer (a 40 ML water film) to dewet the graphite ([bmim][PF(6)]) surface. The occurrence of aging is explainable by the successive evolution of two distinct liquids during the glass-liquid transition: low density liquid is followed by supercooled liquid water. The water monolayer on graphite is characterized by the preferred orientation of unpaired OH groups toward the surface; this structure is arrested during the aging time despite the occurrence of surface diffusion. However, the water monolayer formed on the [bmim][PF(6)] surface agglomerates immediately after the commencement of surface diffusion. The structure of low density liquid tends to be arrested by the attractive interaction with the neighbors.

  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. Mo

  15. 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.

  16. 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.

  17. 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.

  18. First-principles computation of random-pinning glass transition, glass cooperative length scales, and numerical comparisons

    Science.gov (United States)

    Cammarota, Chiara; Seoane, Beatriz

    2016-11-01

    As a guideline for experimental tests of the ideal glass transition (random-pinning glass transition, RPGT) that shall be induced in a system by randomly pinning particles, we performed first-principle computations within the hypernetted chain approximation and numerical simulations of a hard-sphere model of a glass former. We obtain confirmation of the expected enhancement of glassy behavior under the procedure of random pinning. We present the analytical phase diagram as a function of c and of the packing fraction ϕ , showing a line of RPGT ending in a critical point. We also obtain microscopic results on cooperative length scales characterizing medium-range amorphous order in hard-sphere glasses and indirect quantitative information on a key thermodynamic quantity defined in proximity to ideal glass transitions, the amorphous surface tension. Finally, we present numerical results of pair correlation functions able to differentiate the liquid and the glass phases, as predicted by the analytic computations.

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

    Energy Technology Data Exchange (ETDEWEB)

    Stavrou, E; Tsiantos, C; Tsopouridou, R D; Kripotou, S; Kontos, A G; Raptis, C [Department of Physics, National Technical University of Athens, GR-15780 Athens (Greece); Capoen, B; Bouazaoui, M [Laboratoire de Physique des Lasers, Atomes et Molecules (CNRS, UMR 8523), Batiment P-5, Centre d' Etudes et de Recherches Lasers et Applications (CERLA-FR CNRS 2416), Universite de Sciences et Technologies de Lille, F-59655 Villeneuve d' Ascq Cedex (France); Turrell, S; Khatir, S, E-mail: craptis@central.ntua.g [Laboratoire de Spectrochimie Infrarouge et Raman (CNRS 8516), Batiment C-5, Centre d' Etudes et de Recherches Lasers et Applications (CERLA-FR CNRS 2416), Universite de Sciences et Technologies de Lille, F-59655 Villeneuve d' Ascq Cedex (France)

    2010-05-19

    Raman scattering and differential scanning calorimetry (DSC) measurements have been carried out on four mixed tellurium-zinc oxide (TeO{sub 2}){sub 1-x}(ZnO){sub 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{sub g} has been determined for each glass, showing a monotonous decrease of T{sub 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{sub d} very close to the respective T{sub 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{sub 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{sub g} and confirms the correlation between the BP and the MRO of glasses.

  20. 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.

  1. 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.

  2. Single-particle dynamics near the glass transition of a metallic glass

    Science.gov (United States)

    Lü, Y. J.; Wang, W. H.

    2016-12-01

    The single-particle dynamics of the glass-forming C u50Z r50 alloy, from the supercooled liquid well above the glass-transition temperature, Tg to the glassy state, is studied by using the molecular dynamics simulations. When the liquid is cooled below 1.2 Tg , the dynamics heterogeneity characterized by the cage-jump motion becomes increasingly pronounced. The analyses based on the continuous time random walk method indicate that the liquid falls out of equilibrium in the present simulation time scale when it is cooled into the regime below 1.02 Tg . However, we find that the jump length and the jump rate do not display the non-equilibrium behaviors even in the glassy state below Tg, which allows us to study the intrinsic dynamic characteristics through Tg. The mean waiting time between two successive jumps has a rapid growth following the Vogel-Fulcher-Tammann law as the non-equilibrium regime is approached, in analogy with the temperature behaviors of transport properties for fragile supercooled liquids. In contrast, the jump rate maintains the Arrhenius decay and the jump length has even a weaker temperature dependence when the liquid is cooled into glassy state. We find that a pronounced enhancement of the spatial correlation of jumps occurs accompanied by the glass transition: the string-like cooperative jumps dominate the fast motion instead of the uncorrelated and individual jumps. Our work offers an insight into the equilibrium effect of the single-particle dynamics in glass transition.

  3. Effect of chain end group on surface glass transition temperature of thin polymer film

    Science.gov (United States)

    Jiang, Xiqun; Yang, Chang Zheng; Tanaka, Keiji; Takahara, Atsushi; Kajiyama, Tisato

    2001-04-01

    Surface glass transition behaviors of proton end capped poly(2-vinylpyridine) (P2VP-H) and perfluoroalkyl end capped poly(2-vinylpyridine) (P2VP-C 2C 8F) thin films were investigated based on temperature-dependent lateral force microscopic (TDLFM) measurement. It is found that the species of chain end groups have significant influence on the surface glass transition temperature of the thin polymer film. For both samples, it is revealed that the surface glass transition temperatures decrease significantly in comparison to the bulk ones, and the magnitude order of reduction in surface Tg for P2VP-C 2C 8F is larger than that for P2VP-H. The apparent activation energy of surface α-relaxation calculated from the Arrhenius plot is ca. 292±40 and 212±40 kJ/mol for P2VP-H and P2VP-C 2C 8F, respectively, and is much smaller than the bulk one. The depression of the surface Tg for thin polymer films is explained by the excess free volume induced by the enrichment of chain end groups at the surface.

  4. Dynamic Heterogeneity in Highly Cross-linked Epoxy in the Vicinity of Glass Transition

    Science.gov (United States)

    Lin, Po-Han; Khare, Rajesh

    2010-03-01

    Cross-linked epoxy has been widely used in aerospace and electronics industries. The highly cross-linked nature of these systems leads to different chain dynamics as compared to the linear polymeric systems. In this work, we have used molecular dynamics (MD) simulations to study the dynamic heterogeneity in cross-linked epoxy near the glass transition temperature. Well-relaxed atomistic models of cross-linked epoxy were first created by employing the simulated annealing polymerization approach. The specific epoxy system studied consisted of diglycidyl ether of bisphenol-A (DGEBA) as the epoxy monomer and trimethylene glycol di-p-aminobenzoate (TMAB) as the cross-linker. The glass transition temperature of these model structures was determined from MD simulation by monitoring their volume-temperature behaviour in a stepwise cooling run. The chain dynamics of these systems were characterized by their local translational and orientational mobility. Furthermore, dynamic heterogeneity was studied by analyzing the spatial distribution of the mobile and immobile atoms in the system near the glass transition temperature.

  5. Affinity and its derivatives in the glass transition process

    Science.gov (United States)

    Garden, J.-L.; Guillou, H.; Richard, J.; Wondraczek, L.

    2012-07-01

    The thermodynamic treatment of the glass transition remains an issue of intense debate. When associated with the formalism of non-equilibrium thermodynamics, the lattice-hole theory of liquids can provide new insight in this direction, as has been shown by Schmelzer and Gutzow [J. Chem. Phys. 125, 184511 (2006)], 10.1063/1.2374894, by Möller et al. [J. Chem. Phys. 125, 094505 (2006)], 10.1063/1.2346673, and more recently by Tropin et al. [J. Non-Cryst. Solids 357, 1291 (2011), 10.1016/j.jnoncrysol.2010.11.111; Tropin et al., J. Non-Cryst. Solids 357, 1303 (2011)], 10.1016/j.jnoncrysol.2010.12.005. Here, we employ a similar approach. We include pressure as an additional variable, in order to account for the freezing-in of structural degrees of freedom upon pressure increase. Second, we demonstrate that important terms concerning first order derivatives of the affinity-driving-force with respect to temperature and pressure have been previously neglected. We show that these are of crucial importance in the approach. Macroscopic non-equilibrium thermodynamics is used to enlighten these contributions in the derivation of Cp,κT, and αp. The coefficients are calculated as a function of pressure and temperature following different theoretical protocols, revealing classical aspects of vitrification and structural recovery processes. Finally, we demonstrate that a simple minimalist model such as the lattice-hole theory of liquids, when being associated with rigorous use of macroscopic non-equilibrium thermodynamics, is able to account for the primary features of the glass transition phenomenology. Notwithstanding its simplicity and its limits, this approach can be used as a very pedagogical tool to provide a physical understanding on the underlying thermodynamics which governs the glass transition process.

  6. Pressure Dependence of the Glass Transition Temperature in the Fragile Glass Former Cumene

    Science.gov (United States)

    Raty, Jean-Yves; Baris Malcioglu, Osman; Bichara, Christophe

    2013-03-01

    The glass transition temperature, Tg, is one of the most important characteristics of glassy systems. While Tg has been measured for many systems at atmospheric pressure, direct measurement of the glass transition is difficult at high pressures due to small sample sizes and long time scales. Tg(P) measurements to date mostly involve extrapolations of high-pressure viscosity or relaxation data to η = 1013 P or t = 100 s, respectively. In this study we present direct measurement of Tg at pressures up to several GPa through a combination of pressure gradient tracking and observation of increases in the thermal expansion coefficient upon heating from the glass to the viscous liquid state. High pressures are attained through the use of a diamond anvil cell and precise temperatures are maintained via custom heating and cryogenic systems. By directly mapping this phase boundary, we can compare models for Tg(P). In addition, high-pressure analysis requiring knowledge of Tg at pressure will be greatly aided.

  7. Dynamic mechanical behavior of a Zr-based bulk metallic glass during glass transition and crystallization

    Institute of Scientific and Technical Information of China (English)

    CHAO Qi; WANG Qing; DONG Yuanda

    2009-01-01

    The dynamic mechanical behaviors of the Zr41Ti14Cu12.5Ni8Be22.5Fe2 bulk metallic glass (BMG) during continuous heating at a constant rate were investigated. The glass transition and crystallization of the Zr-based BMG were thus characterized by the measurements of storage modulus E and internal friction Q-1. It was found that the variations of these dynamic mechanical quantifies with temperature were interre-lated and were well in agreement with the DSC trace obtained at the same heating rate. The origin of the first peak in the internal friction curve was closely related to the dynamic glass transition and subsequent primary crystallization. Moreover, it can be well described by a physical model, which can characterize atomic mobility and mechanical response of disordered condense materials. In comparison with the DSC trace, the relative position of the first internal friction peak of the BMG was found to be dependent on its thermal stability against crys-tallization.

  8. Is the Glass Half Full or Half Empty? How to Reverse the Effect of Glass Elongation on the Volume Poured

    NARCIS (Netherlands)

    Caljouw, Simone R.; van Wijck, Ruud

    2014-01-01

    To reduce the volume of drinks and the risk of overconsumption, health professionals recommend the use of tall skinny instead of short wide glasses. Yet the results of the present study contradict this health advice. Participants who generously filled up a glass with lemonade served 9% more in tall

  9. QSPR Study on the Glass Transition Temperature of Polyacrylates

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Structural parameters of 22 polyacrylic compounds were computed at two levels using Hartree-Fock and DFT methods. Based on the experimental data of glass transition temperature (Tg), four-parameter (energy of the lowest unoccupied molecular orbital (ELOMO), the highest positive charge (Qmax+), dipole moments (μ) and the next highest occupied molecular orbital (ENLOMO)) dependent equations were developed using structural parameters as theoretical descriptors. Especially, Tg dependent equation calculated at the HF/6-31G(d) level is more advantageous than others in view of their correlation and predictive abilities. This dependent equation was validated by variance inflation factors (VIF) and t-test methods.

  10. Molecular Dynamics Simulation of Glass Transition Behavior of Polyimide Ensemble

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of chromophores to the glass transition temperature of polyimide ensemble has been investigated by means of molecular dynamics simulation in conjunction with barrier analysis. Simulated Tg results indicated a good agreement with experimental value. This study showed the MD simulation could estimate the effect of chromophores to the Tg of polyimide ensemble conveniently and an estimation approach method had a surprising deviation of Tg from experiment. At the same time, a polyimide structure with higher barrier energy was designed and validated by MD simulation.

  11. 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

  12. Glass transition temperatures of epoxy resins by pulsed nuclear magnetic resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rutenberg, A.C.; Dorsey, G.F.; Peck, C.G.

    1976-04-21

    Pulsed nuclear magnetic resonance spectroscopy has been used to measure the glass transition temperatures of cured epoxy resins. These measurements make it possible to monitor the cure and determine the glass transition temperature as a function of the curing conditions and the concentration of the components. Knowledge of the glass transition temperature of the cured epoxies allows screening of them for a number of uses, including adhesives and coatings operations.

  13. Transition and post-transition metal ions in borate glasses: Borate ligand speciation, cluster formation, and their effect on glass transition and mechanical properties

    Science.gov (United States)

    Möncke, D.; Kamitsos, E. I.; Palles, D.; Limbach, R.; Winterstein-Beckmann, A.; Honma, T.; Yao, Z.; Rouxel, T.; Wondraczek, L.

    2016-09-01

    A series of transition and post-transition metal ion (Mn, Cu, Zn, Pb, Bi) binary borate glasses was studied with special consideration of the cations impact on the borate structure, the cations cross-linking capacity, and more generally, structure-property correlations. Infrared (IR) and Raman spectroscopies were used for the structural characterization. These complementary techniques are sensitive to the short-range order as in the differentiation of tetrahedral and trigonal borate units or regarding the number of non-bridging oxygen ions per unit. Moreover, vibrational spectroscopy is also sensitive to the intermediate-range order and to the presence of superstructural units, such as rings and chains, or the combination of rings. In order to clarify band assignments for the various borate entities, examples are given from pure vitreous B2O3 to meta-, pyro-, ortho-, and even overmodified borate glass compositions. For binary metaborate glasses, the impact of the modifier cation on the borate speciation is shown. High field strength cations such as Zn2+ enhance the disproportionation of metaborate to polyborate and pyroborate units. Pb2+ and Bi3+ induce cluster formation, resulting in PbOn- and BiOn-pseudophases. Both lead and bismuth borate glasses show also a tendency to stabilize very large superstructural units in the form of diborate polyanions. Far-IR spectra reflect on the bonding states of modifier cations in glasses. The frequency of the measured cation-site vibration band was used to obtain the average force constant for the metal-oxygen bonding, FM-O. A linear correlation between glass transition temperature (Tg) and FM-O was shown for the metaborate glass series. The mechanical properties of the glasses also correlate with the force constant FM-O, though for cations of similar force constant the fraction of tetrahedral borate units (N4) strongly affects the thermal and mechanical properties. For paramagnetic Cu- and Mn-borate glasses, N4 was determined

  14. Assignment of the glass transition temperature using dielectric analysis: A review

    Energy Technology Data Exchange (ETDEWEB)

    Bidstrup, S.A. [Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemical Engineering; Day, D.R. [Auburn International, Danvers, MA (United States)

    1994-09-01

    The use of dielectric analysis for the determination of the glass transition temperature for polymers is reviewed. Both a sharp increase in the permittivity and the dielectric loss peak have been correlated with the glass transition. Dielectric data for an epoxy resin and polyvinylchloride are presented and compared with data obtained by differential scanning calorimetry (DSC). The dielectric glass transition approaches the DSC glass transition as the frequency of the dielectric measurement is decreased. The effects of contact resistance and moisture on the dielectric measurement are also discussed.

  15. Kinetics of glass transition and crystallization in multicomponent bulk amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    庄艳歆[1; 赵德乾[2; 张勇[3; 汪卫华[4; 潘明祥[5

    2000-01-01

    Differential scanning calorimeter (DSC) is used to investigate apparent activation energy of glass transition and crystallization of Zr-based bulk amorphous alloys by Kissinger equation under non-isothermal condition. It is shown that the glass transition behavior as well as crystallization reaction depends on the heating rate and has a characteristic of kinetic effects. After being isothermally annealed near glass transition temperature, the apparent activation energy of glass transition increases and the apparent activation energy of crystallization reaction decreases. However, the kinetic effects are independent of the pre-annealing.

  16. Glass transition of polymers in bulk, confined geometries, and near interfaces

    Science.gov (United States)

    Napolitano, Simone; Glynos, Emmanouil; Tito, Nicholas B.

    2017-03-01

    When cooled or pressurized, polymer melts exhibit a tremendous reduction in molecular mobility. If the process is performed at a constant rate, the structural relaxation time of the liquid eventually exceeds the time allowed for equilibration. This brings the system out of equilibrium, and the liquid is operationally defined as a glass—a solid lacking long-range order. Despite almost 100 years of research on the (liquid/)glass transition, it is not yet clear which molecular mechanisms are responsible for the unique slow-down in molecular dynamics. In this review, we first introduce the reader to experimental methodologies, theories, and simulations of glassy polymer dynamics and vitrification. We then analyse the impact of connectivity, structure, and chain environment on molecular motion at the length scale of a few monomers, as well as how macromolecular architecture affects the glass transition of non-linear polymers. We then discuss a revised picture of nanoconfinement, going beyond a simple picture based on interfacial interactions and surface/volume ratio. Analysis of a large body of experimental evidence, results from molecular simulations, and predictions from theory supports, instead, a more complex framework where other parameters are relevant. We focus discussion specifically on local order, free volume, irreversible chain adsorption, the Debye–Waller factor of confined and confining media, chain rigidity, and the absolute value of the vitrification temperature. We end by highlighting the molecular origin of distributions in relaxation times and glass transition temperatures which exceed, by far, the size of a chain. Fast relaxation modes, almost universally present at the free surface between polymer and air, are also remarked upon. These modes relax at rates far larger than those characteristic of glassy dynamics in bulk. We speculate on how these may be a signature of unique relaxation processes occurring in confined or heterogeneous polymeric

  17. Predict the glass transition temperature of glycerol-water binary cryoprotectant by molecular dynamic simulation.

    Science.gov (United States)

    Li, Dai-Xi; Liu, Bao-Lin; Liu, Yi-shu; Chen, Cheng-lung

    2008-04-01

    Vitrification is proposed to be the best way for the cryopreservation of organs. The glass transition temperature (T(g)) of vitrification solutions is a critical parameter of fundamental importance for cryopreservation by vitrification. The instruments that can detect the thermodynamic, mechanical and dielectric changes of a substance may be used to determine the glass transition temperature. T(g) is usually measured by using differential scanning calorimetry (DSC). In this study, the T(g) of the glycerol-aqueous solution (60%, wt/%) was determined by isothermal-isobaric molecular dynamic simulation (NPT-MD). The software package Discover in Material Studio with the Polymer Consortium Force Field (PCFF) was used for the simulation. The state parameters of heat capacity at constant pressure (C(p)), density (rho), amorphous cell volume (V(cell)) and specific volume (V(specific)) and radial distribution function (rdf) were obtained by NPT-MD in the temperature range of 90-270K. These parameters showed a discontinuity at a specific temperature in the plot of state parameter versus temperature. The temperature at the discontinuity is taken as the simulated T(g) value for glycerol-water binary solution. The T(g) values determined by simulation method were compared with the values in the literatures. The simulation values of T(g) (160.06-167.51K) agree well with the DSC results (163.60-167.10K) and the DMA results (159.00K). We drew the conclusion that molecular dynamic simulation (MDS) is a potential method for investigating the glass transition temperature (T(g)) of glycerol-water binary cryoprotectants and may be used for other vitrification solutions.

  18. High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 3

    Energy Technology Data Exchange (ETDEWEB)

    Cunnane, J.C. [comp.; Bates, J.K.; Bradley, C.R. [Argonne National Lab., IL (United States)] [and others

    1994-03-01

    The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II.

  19. Evidence for a simple monatomic ideal glass former: the thermodynamic glass transition from a stable liquid phase.

    Science.gov (United States)

    Elenius, Måns; Oppelstrup, Tomas; Dzugutov, Mikhail

    2010-11-01

    Under cooling, a liquid can undergo a transition to the glassy state either as a result of a continuous slowing down or by a first-order polyamorphous phase transition. The second scenario has so far always been observed in a metastable liquid domain below the melting point where crystalline nucleation interfered with the glass formation. We report the first observation of the liquid-glass transition by a first-order polyamorphous phase transition from the equilibrium stable liquid phase. The observation was made in a molecular dynamics simulation of a one-component system with a model metallic pair potential. In this way, the model, demonstrating the thermodynamic glass transition from a stable liquid phase, may be regarded as a candidate for a simple monatomic ideal glass former. This observation is of conceptual importance in the context of continuing attempts to resolve the long-standing Kauzmann paradox. The possibility of a thermodynamic glass transition from an equilibrium melt in a metallic system also indicates a new strategy for the development of bulk metallic glass-forming alloys.

  20. The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

    Energy Technology Data Exchange (ETDEWEB)

    Ebert, W.L. [Argonne National Lab., IL (United States). Chemical Technology Div.

    1995-03-01

    This report reviews and summarizes the present state of knowledge regarding the effects of the glass surface area/solution volume (SA/V) ratio on the corrosion behavior of borosilicate waste glasses. The SA/V ratio affects the rate of glass corrosion through the extent of dilution of corrosion products released from the glass into the leachate solution: glass corrosion products are diluted more in tests conducted at low SA/V ratios than they are in tests conducted at high SA/V ratios. Differences in the solution chemistries generated in tests conducted at different SA/V ratios then affect the observed glass corrosion behavior. Therefore, any testing parameter that affects the solution chemistry will also affect the glass corrosion rate. The results of static leach tests conducted to assess the effects of the SA/V are discussed with regard to the effects of SA/V on the solution chemistry. Test results show several remaining issues with regard to the long-term glass corrosion behavior: can the SA/V ratio be used as an accelerating parameter to characterize the advanced stages of glass corrosion relevant to long disposal times; is the alteration of the glass surface the same in tests conducted at different SA/V, and in tests conducted with monolithic and crushed glass samples; what are the effects of the SA/V and the extent of glass corrosion on the disposition of released radionuclides? These issues will bear on the prediction of the long-term performance of waste glasses during storage. The results of an experimental program conducted at ANL to address these and other remaining issues regarding the effects of SA/V on glass corrosion are described. 288 refs., 59 figs., 16 tabs.

  1. The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

    Energy Technology Data Exchange (ETDEWEB)

    Ebert, W.L. [Argonne National Lab., IL (United States). Chemical Technology Div.

    1995-03-01

    This report reviews and summarizes the present state of knowledge regarding the effects of the glass surface area/solution volume (SA/V) ratio on the corrosion behavior of borosilicate waste glasses. The SA/V ratio affects the rate of glass corrosion through the extent of dilution of corrosion products released from the glass into the leachate solution: glass corrosion products are diluted more in tests conducted at low SA/V ratios than they are in tests conducted at high SA/V ratios. Differences in the solution chemistries generated in tests conducted at different SA/V ratios then affect the observed glass corrosion behavior. Therefore, any testing parameter that affects the solution chemistry will also affect the glass corrosion rate. The results of static leach tests conducted to assess the effects of the SA/V are discussed with regard to the effects of SA/V on the solution chemistry. Test results show several remaining issues with regard to the long-term glass corrosion behavior: can the SA/V ratio be used as an accelerating parameter to characterize the advanced stages of glass corrosion relevant to long disposal times; is the alteration of the glass surface the same in tests conducted at different SA/V, and in tests conducted with monolithic and crushed glass samples; what are the effects of the SA/V and the extent of glass corrosion on the disposition of released radionuclides? These issues will bear on the prediction of the long-term performance of waste glasses during storage. The results of an experimental program conducted at ANL to address these and other remaining issues regarding the effects of SA/V on glass corrosion are described. 288 refs., 59 figs., 16 tabs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R. Scott; Kay, Bruce D.

    2012-03-15

    Experimental measurements of the properties supercooled liquids at temperatures near their respective 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.

  3. 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.

  4. 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...... effect on crystallization is studied by in situ high-pressure and high-temperature XRD using synchrotron radiation. Two crystallization temperatures, observed by in-situ XRD, behave differently with varying pressure. The onset crystallization temperature increases with pressure with a slope of 9.5 K...

  5. Effects of transition metal oxide doping on the structure of sodium metaphosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Zotov, N.; Kirfel, A.; Beuneu, B.; Delaplane, R.; Hohlwein, D.; Reinauer, F.; Glaum, R

    2004-07-15

    Neutron diffraction measurements of transition metal-oxide-doped sodium metaphosphate glasses and melts show an anomalous increase of the first sharp diffraction peak both with increasing transition metal content and temperature due to progressive increase of the structural disorder.

  6. Comment on "Liquid Limits: The Glass Transition and Liquid-Gas Spinodal Boundaries of Metastable Liquids"

    OpenAIRE

    2000-01-01

    In ref. cond-mat/0005372, Sastry studies by numerical simulations the phase diagram of a simple fragile glass-forming liquid, presenting very interesting and clear results. We apply to this system, at various density values, the analytic approach to structural glass thermodynamics recently introduced and we compare our theoretical predictions on the liquid-glass transition temperature with Sastry's data.

  7. Effect of incongruent crystallization on glass–liquid transition features of a bulk metal glass

    Energy Technology Data Exchange (ETDEWEB)

    Aji, D.P.B.; Johari, G.P., E-mail: joharig@mcmaster.ca

    2015-09-10

    Highlights: • Ce{sub 66}Al{sub 10}Cu{sub 20}Co{sub 4} glass did not crystallize during aging for nine years. • Crystallization's onset temperature was higher for the aged glass. • Incongruent melt embedding the crystals had higher viscosity and T{sub g}. • Increase in crystallization increased the T{sub g} and broadened the T{sub g}-endotherm. - Abstract: It is known that most multi-component glasses cold-crystallize incongruently on heating through the temperature range of their ultraviscous melt. If the incongruent melt's composition changes with time, its viscosity, η, and the glass–liquid transition temperature, T{sub g}, would change. Since the η, relaxation time, and expansion coefficient of a liquid in its partially crystallized mixture cannot be determined, we used scanning calorimetry to study the liquid–glass–liquid transition during thermal cycling of the incongruently crystallizing Ce{sub 66}Al{sub 10}Cu{sub 20}Co{sub 4} glass. Its T{sub g} is 358 K for 20 K/min and 354 K for 10 K/min heating rates, and its ultraviscous melt crystallized incongruently when heated beyond the hysteresis peak of its heat capacity scan. Its sample that had been aged for nine years at ambient conditions had a higher crystallization-onset temperature than an un-aged sample. Delayed enthalpy gain on heating of the aged glass is ∼1/5th of the enthalpy lost on its crystallization. Crystallization of the melt occurred on both the heating and cooling paths of a thermal cycle and T{sub g} of the un-aged glass increased as the volume fraction of the compositionally different glass, f{sub gl}, decreased. The increase was by 8 K after the 24th cycle of 20 K/min, and by 11 K after the 13th cycle of 10 K/min cooling-heating. The highest T{sub g} values reached differed by ∼1 K, which indicates that closely similar T{sub g}s may be reached if the total time period for thermal cycling (at different rates) is kept the same. As f{sub gl} approached its limiting

  8. The glass transition process in humid biopolymers. DSC study

    Energy Technology Data Exchange (ETDEWEB)

    Grunina, N A; Belopolskaya, T V; Tsereteli, G I [V.A. Fock Research Institute for Physics of Saint-Petersburg State University, 198504, Petrodvorets (Russian Federation)

    2006-05-15

    Thermal properties of native and denatured biopolymers with quite different chemical and steric structure (globular and fibrillar proteins, DNA, starches) were studied by means of differential scanning calorimetry in a wide range of temperatures and concentrations of water. It was shown that both native and denatured humid biopolymers are glassy systems. The glass transition temperature of these systems strongly depends on percentage of water, with water being simultaneously an intrinsic element of systems' ordered structure and a plasticizer of its amorphous state. On the base of the absolute values of heat capacities for biopolymer-water systems as a whole, heat capacities for biopolymers themselves were calculated as functions on water concentration at fixed temperatures. The S-shaped change of heat capacity observed on diagrams of state both for native and denatured biopolymers is the manifestation of biopolymers' passing through the vitrification region, as it occurs for denatured samples at heating.

  9. Modeling the nonlinear PMMA behavior near glass transition temperature: application to its thermoforming

    Science.gov (United States)

    Gilormini, P.; Chevalier, L.; Régnier, G.

    2011-01-01

    Using suitable constitutive equations, numerical simulation allows predicting the properties of transparencies that are thermoformed near their glass transition temperature. Such equations are presented, which describe the nonlinear viscoelastic behavior of poly(methyl methacrylate) at large deformations near glass transition. The simulation of the thermoforming of a transparency at constant and uniform temperature is performed and compared with experimental results.

  10. High-level waste borosilicate glass: A compendium of corrosion characteristics. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Cunnane, J.C. [comp.; Bates, J.K.; Bradley, C.R. [Argonne National Lab., IL (United States)] [and others

    1994-03-01

    The objective of this document is to summarize scientific information pertinent to evaluating the extent to which high-level waste borosilicate glass corrosion and the associated radionuclide release processes are understood for the range of environmental conditions to which waste glass may be exposed in service. Alteration processes occurring within the bulk of the glass (e.g., devitrification and radiation-induced changes) are discussed insofar as they affect glass corrosion.This document is organized into three volumes. Volumes I and II represent a tiered set of information intended for somewhat different audiences. Volume I is intended to provide an overview of waste glass corrosion, and Volume 11 is intended to provide additional experimental details on experimental factors that influence waste glass corrosion. Volume III contains a bibliography of glass corrosion studies, including studies that are not cited in Volumes I and II. Volume I is intended for managers, decision makers, and modelers, the combined set of Volumes I, II, and III is intended for scientists and engineers working in the field of high-level waste.

  11. 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 ...

  12. Glass transition and crystallization process of hard magnetic bulk Nd60Al10Fe20Co10 metallic glass

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Glass transition and crystallization process of bulk Nd60Al10Fe20Co10 metallic glass were investigated by means of dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electronic microscopy (SEM). It is shown that the glass transition and onset crystallization temperature determined by DMTA at a heating rate of 0.167 K/s are 480 and 588 K respectively. The crystallization process of the metallic glass is concluded as follows: amorphous α→α′+metastable FeNdAl novel phase →α′+primary δ phase→primary δ phase+eutectic δ phase Nd3Al phase+Nd3Co phase. The appearance of hard magnetism in this alloy is ascribed to the presence of amorphous phase with highly relaxed structure. The hard magnetism disappeared after the eutectic crystallization of amorphous phase.

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

    Science.gov (United States)

    Šmit, Žiga; Knific, Timotej; Jezeršek, David; Istenič, Janka

    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.

  15. 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.

  16. Effect of UV exposure on photochromic glasses doped with transition metal oxides

    Science.gov (United States)

    El-Zaiat, S. Y.; Medhat, M.; Omar, Mona F.; Shirif, Marwa A.

    2016-07-01

    Silver halide photochromic glasses doped with one of the transition metal oxides, (Ti O2) , (CoO) ,(Cr2 O3) are prepared using the melt quench technique. Glass samples are exposed to a UV source for 20 min. Spectral reflectance and transmittance at normal incidence of the prepared glasses are recorded before and after UV exposure with a double beam spectrophotometer in the spectral range 200-2500 nm. Dispersion parameters such as: single oscillator energy, dispersion energy and Abbe's number are deduced and compared. Absorption dispersion parameters, like optical energy gap for direct and indirect transitions, Urbach energy and steepness parameter, are deduced for the different glass prepared. Reflection loss, molar refractivity and electronic polarizability are deduced and compared. The effect of UV light exposure of these glasses on transmittance, reflectance, the linear and the predicted nonlinear optical parameters are investigated and discussed for the three transition metals. Nonlinear parameters increase in the three glass samples after UV exposure.

  17. Transition from stress-driven to thermally activated stress relaxation in metallic glasses

    Science.gov (United States)

    Qiao, J. C.; Wang, Yun-Jiang; Zhao, L. Z.; Dai, L. H.; Crespo, D.; Pelletier, J. M.; Keer, L. M.; Yao, Y.

    2016-09-01

    The short-range ordered but long-range disordered structure of metallic glasses yields strong structural and dynamic heterogeneities. Stress relaxation is a technique to trace the evolution of stress in response to a fixed strain, which reflects the dynamic features phenomenologically described by the Kohlrausch-Williams-Watts (KWW) equation. The KWW equation describes a broad distribution of relaxation times with a small number of empirical parameters, but it does not arise from a particular physically motivated mechanistic picture. Here we report an anomalous two-stage stress relaxation behavior in a Cu46Zr46Al8 metallic glass over a wide temperature range and generalize the findings in other compositions. Thermodynamic analysis identifies two categories of processes: a fast stress-driven event with large activation volume and a slow thermally activated event with small activation volume, which synthetically dominates the stress relaxation dynamics. Discrete analyses rationalize the transition mechanism induced by stress and explain the anomalous variation of the KWW characteristic time with temperature. Atomistic simulations reveal that the stress-driven event involves virtually instantaneous short-range atomic rearrangement, while the thermally activated event is the percolation of the fast event accommodated by the long-range atomic diffusion. The insights may clarify the underlying physical mechanisms behind the phenomenological description and shed light on correlating the hierarchical dynamics and structural heterogeneity of amorphous solids.

  18. Conformational Fluctuations of Polymers in a Melt Associated with Glass Transition

    Science.gov (United States)

    Iwaoka, Nobuyuki; Takano, Hiroshi

    2017-03-01

    The conformational fluctuations of a glassy short polymer melt are studied by coarse-grained molecular dynamics simulations and principal component analysis (PCA). The distribution of PCA eigenvalues, which measure static fluctuations of the polymers, shows a clear difference between above and below the conventional glass transition temperature Tg. The approximate conformational entropy of the polymers also indicates a transition near Tg. This is evidence that the static properties of polymers in the melt signal the glass transition.

  19. Replica symmetry breaking transition of the weakly anisotropic Heisenberg spin glass in magnetic fields.

    Science.gov (United States)

    Imagawa, Daisuke; Kawamura, Hikaru

    2004-02-20

    The spin and the chirality orderings of the three-dimensional Heisenberg spin glass with the weak random anisotropy are studied under applied magnetic fields by equilibrium Monte Carlo simulations. A replica symmetry breaking transition occurs in the chiral sector accompanied by the simultaneous spin-glass order. The ordering behavior differs significantly from that of the Ising spin glass, despite the similarity in the global symmetry. Our observation is consistent with the spin-chirality decoupling-recoupling scenario of a spin-glass transition.

  20. Soft glassy colloidal arrays in an ionic liquid: colloidal glass transition, ionic transport, and structural color in relation to microstructure.

    Science.gov (United States)

    Ueno, Kazuhide; Sano, Yuta; Inaba, Aya; Kondoh, Masashi; Watanabe, Masayoshi

    2010-10-21

    The colloidal glass transition, ionic transport, and optical properties of soft glassy colloidal arrays (SGCAs) that consist of poly(methyl methacrylate) (PMMA)-grafted silica nanoparticles (PMMA-g-NPs) and a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfonyl)amide ([C(2)mim][NTf(2)]), were investigated. At lower particle concentrations, PMMA-g-NPs were well-suspended in the IL without any aggregation or sedimentation, and the dilute suspensions showed liquid-like behavior. However, above a certain particle concentration, the suspensions became solidified and exhibited different structural colors depending on the particle concentrations. The liquid-solid transition of the SGCAs was essentially caused by colloidal glass transition. Due to the soft repulsive interaction between the particles, the effective volume fraction of the particle (ϕ(eff)) required for colloidal glass transition was higher than that of the hard sphere system and found to be approximately 0.70-0.74. The SGCA had sufficient ionic conductivity, which was greater than 10(-3) S cm(-1) at room temperature, even in the highly concentrated region. For ionic transport of the cation and the anion in the SGCAs, the decrease in diffusivity observed with the addition of the particles (D(g)/D(0)) was slightly greater for the [NTf(2)] anion than that of the [C(2)mim] cation, suggesting that the [NTf(2)] anion preferentially interacts with the PMMA chains. The SGCAs showed homogeneous, nonbrilliant, and angle-independent structural colors above the glass transition volume fraction. In addition, the color of the SGCAs changed from red to green to blue as the particle concentration increased. A linear relationship was found between the maximum wavelength of the reflection spectra and the center-to-center distance in the SGCAs.

  1. Investigation of the atypical glass transition and recrystallization behavior of amorphous prazosin salts.

    Science.gov (United States)

    Kumar, Lokesh; Popat, Dharmesh; Bansal, Arvind K

    2011-08-25

    This manuscript studied the effect of counterion on the glass transition and recrystallization behavior of amorphous salts of prazosin. Three amorphous salts of prazosin, namely, prazosin hydrochloride, prazosin mesylate and prazosin tosylate were prepared by spray drying, and characterized by optical-polarized microscopy, differential scanning calorimetry and powder X-ray diffraction. Modulated differential scanning calorimetry was used to determine the glass transition and recrystallization temperature of amorphous salts. Glass transition of amorphous salts followed the order: prazosin mesylate > prazosin tosylate ~ prazosin hydrochloride. Amorphous prazosin mesylate and prazosin tosylate showed glass transition, followed by recrystallization. In contrast, amorphous prazosin hydrochloride showed glass transition and recrystallization simultaneously. Density Functional Theory, however, suggested the expected order of glass transition as prazosin hydrochloride > prazosin mesylate > prazosin tosylate. The counterintuitive observation of amorphous prazosin hydrochloride having lower glass transition was explained in terms of its lower activation energy (206.1 kJ/mol) for molecular mobility at Tg, compared to that for amorphous prazosin mesylate (448.5 kJ/mol) and prazosin tosylate (490.7 kJ/mol), and was further correlated to a difference in hydrogen bonding strength of the amorphous and the corresponding recrystallized salts. This study has implications in selection of an optimal amorphous salt form for pharmaceutical development.

  2. The Gardner Transition: A new approach for understanding low-temperature glasses

    Science.gov (United States)

    Charbonneau, Patrick

    Recent theoretical advances in the mean-field theory of glasses predict the existence deep in the glass phase of a novel phase transition, a so-called Gardner transition. This transition signals the emergence of a complex free energy landscape composed of a marginally stable hierarchy of sub-basins within a broad glass metabasin. It is thus the onset of marked changes in thermal and transport properties of glasses, and ultimately leads to the unusual critical behavior at jamming. The Gardner transition itself is immediately related to a diverging (i) characteristic relaxation time, (ii) caging susceptibility and (iii) correlation length of the caging heterogeneity as well as aging, even in well-thermalized glasses. We have detected some of these signatures both in a mean-field model and in standard hard-sphere glass formers. We find the results to quantitatively agree with theory in the former and qualitatively so in the latter, which suggest that the transition should be detectable in a wide array of numerical and experimental systems. Interestingly, although the Gardner transitions is primarily associated with structural glass formers, we also find features of the transition in crystals of polydisperse particles once the landscape becomes rough.

  3. The Calorimetric Glass Transition of Polystyrene Ultrathin Films

    Science.gov (United States)

    Gao, Siyang; Koh, Yung; Simon, Sindee; Texas Tech University Team

    2013-03-01

    The glass transition temperature (Tg) for nanoconfined materials have been widely studied since the early 1990s. For supported polystyrene ultrathin films, Tg differs from bulk value. Recent work has attributed nanoconstrained Tg effects to artifact. In this study, we attempted to resolve this controversy and measure Tg for single polystyrene ultrathin films using Flash DSC. Films have been prepared in two ways: spincast films placed on a layer of inert oil or grease and films directly spincast on the back of the calorimetric chip. For the films on oil or on grease, the 160 nm thick films show no Tg depression. On the other hand, thinner films on oil and on grease show a Tg depression which decreases with increasing cooling rate. The depression reverts to the bulk values over the course of a day at 160 °C due to dewetting and thickening. For directly spincast films, no Tg depression is observed, consistent with results from other nanocalorimetry work. Our results are consistent with literature results that Tg decreases with decreasing substrate surface energy, and they also demonstrate that the Tg depression observed is not due to degradation or to plasticization effects.

  4. Coupling of gelation and glass transition in a biphasic colloidal mixture--from gel-to-defective gel-toglass

    Science.gov (United States)

    Cheng, He; Jia, Di; Han, Charles

    The state transition from gel to glass is studied in a biphasic mixture of polystyrene core/poly (N-isopropylacrylamide) shell (CS) microgels and sulfonated polystyrene (PSS) particles. At 35 °C, the interaction between CS is due to short-range Van der Waals attraction while that between PSS is from long-range electrostatic repulsion. During variation of the relative ratio of the two species at a fixed apparent total volume fraction, the mixture exhibits a gel-to-defective gel-to-glass transition. When small amounts of PSS are introduced into the CS gel network, some of them are kinetically trapped, causing a change in its fractal structure, and act as defects to weaken the macroscopic gel strength. An increase of PSS content in the mixture promotes the switch from gel to defective gel, e . g . , the typical two-step yielding gel merges into one-step yielding. This phenomenon is an indication that inter-cluster bond breakage coincides with intra-cluster bond fracture. As the relative volume fraction of PSS exceeds a critical threshold, the gel network can no longer be formed; hence, the mixture exhibits characteristics of glass. A state diagram of the biphasic mixture is constructed, and the landscape of the different transitions will be described in future studies The financial support from the National Basic Research Program of China (973 Program, 2012CB821500) is gratefully acknowledged.

  5. In-volume waveguides by fs-laser direct writing in rare-earth-doped fluoride glass and phosphate glass

    Science.gov (United States)

    Esser, D.; Wortmann, D.; Gottmann, J.

    2009-02-01

    Refractive index modifications are fabricated in the volume of rare-earth-doped glass materials namely Er- and Pr-doped ZBLAN (a fluoride glass consisting of ZrF4, BaF2, LaF3, AlF3, NaF), an Er-doped nano-crystalline glass-ceramic and Yb- and Er-doped phosphate glass IOG. Femtosecond laser radiation (τ=500fs, λ=1045nm, f=0.1-5MHz) from an Ybfiber laser is focused with a microscope objective in the volume of the glass materials and scanned below the surface with different scan velocities and pulse energies. Non-linear absorption processes like multiphoton- and avalanche absorption lead to localized density changes and the formation of color centers. The refractive index change is localized to the focal volume of the laser radiation and therefore, a precise control of the modified volume is possible. The width of the written structures is analyzed by transmission light microscopy and additionally with the quantitative phase microscopy (QPm) software to determine the refractive index distribution perpendicular to a waveguide. Structures larger than 50μm in width are generated at high repetition rates due to heat accumulation effects. In addition, the fabricated waveguides are investigated by far-field measurements of the guided light to determine their numerical apertures. Using interference microscopy the refractive index distribution of waveguide cross-sections in phosphate glass IOG is determined. Several regions with an alternating refractive index change are observed whose size depend on the applied pulse energies and scan velocities.

  6. The Effects of Fibre Volume Fraction on a Glass-Epoxy Composite Material

    Directory of Open Access Journals (Sweden)

    Ciprian LARCO

    2015-09-01

    Full Text Available This paper focuses on the analysis of the longitudinal mechanical properties of Glass Fibre Reinforce Plastic (GFRP plates with different fibre volume fraction, Vf, by considering both analytical and experimental methods. The laminate is 0/90 E-glass/epoxy woven composite material made by hand lay-up technique. Fiber volume fraction, determined by ignition loss method, has a direct influence on the ultimate strength and modulus of elasticity of the composite plate. Tensile tests on specimens with different volume fractions allow the identification of the mathematical relationship between the fibre volume fraction and the longitudinal elastic modulus.

  7. Non-monotonic effect of confinement on the glass transition

    Science.gov (United States)

    Varnik, Fathollah; Franosch, Thomas

    2016-04-01

    The relaxation dynamics of glass forming liquids and their structure are influenced in the vicinity of confining walls. This effect has mostly been observed to be a monotonic function of the slit width. Recently, a qualitatively new behaviour has been uncovered by Mittal and coworkers, who reported that the single particle dynamics in a hard-sphere fluid confined in a planar slit varies in a non-monotonic way as the slit width is decreased from five to roughly two particle diametres (Mittal et al 2008 Phys. Rev. Lett. 100 145901). In view of the great potential of this effect for applications in those fields of science and industry, where liquids occur under strong confinement (e.g. nano-technology), the number of researchers studying various aspects and consequences of this non-monotonic behaviour has been rapidly growing. This review aims at providing an overview of the research activity in this newly emerging field. We first briefly discuss how competing mechanisms such as packing effects and short-range attraction may lead to a non-monotonic glass transition scenario in the bulk. We then analyse confinement effects on the dynamics of fluids using a thermodynamic route which relates the single particle dynamics to the excess entropy. Moreover, relating the diffusive dynamics to the Widom’s insertion probability, the oscillations of the local dynamics with density at moderate densities are fairly well described. At high densities belonging to the supercooled regime, however, this approach breaks down signaling the onset of strongly collective effects. Indeed, confinement introduces a new length scale which in the limit of high densities and small pore sizes competes with the short-range local order of the fluid. This gives rise to a non-monotonic dependence of the packing structure on confinement, with a corresponding effect on the dynamics of structural relaxation. This non-monotonic effect occurs also in the case of a cone-plate type channel, where the degree

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

    DEFF Research Database (Denmark)

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

    substitution) or glass systems of different bonding types (covalent, metallic and ionic bonds). In addition, we discuss how chemical bond is associated with glass Cp (at T ... 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...

  9. Resolution of conflicting views on thermodynamics of glass transition: A unified model

    Indian Academy of Sciences (India)

    K T Jacob; Sagar Prabhudev; R M Mallya

    2010-10-01

    Classical description of thermodynamic properties during glass transition has been questioned by the entropy-loss model. The uncompensated loss of entropy at the glass transition temperature and zero residual entropy is at the heart of the controversy. Both the models are critically reviewed. A unified model is presented which incorporates features of both entropy loss and residual entropy. It implies two different types of contributions to the entropy of the supercooled liquid, one of which vanishes at the transition and the other which contributes to residual entropy. Entropy gain during spontaneous relaxation of glass, and the nature of heat capacity ‘hysteresis’ during cooling and heating through the glass transition range support the proposed model. Experiments are outlined for differentiating between the models.

  10. Effect of the metal-insulator transition on the spin-glass interaction

    Science.gov (United States)

    Hauser, J. J.; Felder, R. J.; Blitzer, L. D.

    1986-03-01

    The effect of the metal-insulator transition on the spin-glass interaction was studied by measuring the magnetic properties of (MnSi)O X as a function of oxygen content X. As X varies from 0 to 3.6 one changes from a metallic to an insulating spin-glass. The transition at X ≲ 1 is marked by a sharp decrease in the susceptibility and a change of the Curie-Weiss temperature (θ) from ferromagnetic to antiferromagnetic.

  11. Direct evidence of entropy driven fluid-like - glass-like transition in microgel suspensions

    Science.gov (United States)

    Guo, Yun Xia; Liu, Ying Dan; Liu, Riping; Tian, Yongjun; Chen, Ke; Wang, Li-Min

    2017-02-01

    The phase transitions in poly (N-isopropylacrylamide) (PNIPAM) microgel suspensions are studied using rheological and calorimetric measurements at various concentrations. Two transitions are resolved, one being the hydrophilic-hydrophobic transition imposed by the gain/release of H2O molecules in PNIPAM particles via H-bond interactions, the other the fluid-like - glass-like transition of the hydrated microgels. The relaxation behaviors in the frozen glass-like states are observed by monitoring the shear modulus upon aging. Nevertheless, no enthalpic signature is detected in the relaxation process, suggesting entropy-driven relaxation dynamics.

  12. Large N Phase Transitions, Finite Volume, and Entanglement Entropy

    CERN Document Server

    Johnson, Clifford V

    2014-01-01

    Holographic studies of the entanglement entropy of field theories dual to charged and neutral black holes in asymptotically global AdS4 spacetimes are presented. The goal is to elucidate various properties of the quantity that are peculiar to working in finite volume, and to gain access to the behaviour of the entanglement entropy in the rich thermodynamic phase structure that is present at finite volume and large N. The entropy is followed through various first order phase transitions, and also a novel second order phase transition. Behaviour is found that contrasts interestingly with an earlier holographic study of a second order phase transition dual to an holographic superconductor.

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

    Indian Academy of Sciences (India)

    Subir Sachdev

    2002-02-01

    We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment. 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 magnetoconductance measurements. We present a quantum field theory for such a transition and compute its mean field properties.

  14. Study of structural and optical properties of lead borate glasses containing transition metal ion

    Science.gov (United States)

    Sanjay, Kaushik, A.; Kishore, N.; Agarwal, A.; Pal, I.; Dhar, R.

    2012-06-01

    Glasses with compositions xFe2O3.(40-x)PbO.60B2O3: V2O5 (2 mol%) have been prepared by the standard melt-quenching technique. Various properties such as glass transition temperature, density, IR spectra and optical band gap energy have been studied. The structural changes in these glasses have been monitored by IR spectroscopy. The values of optical band gap for indirect allowed and indirect forbidden transitions have been determined using available theories. The Urbach's energy is used to characterize the degree of disorder in amorphous solids.

  15. 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.

  16. Observation of exchanging role of gold and silver nanoparticles in bimetallic thin film upon annealing above the glass transition temperature

    Science.gov (United States)

    Htet Kyaw, Htet; Tay Zar Myint, Myo; Hamood Al-Harthi, Salim; Maekawa, Toru; Yanagisawa, Keiichi; Sellai, Azzouz; Dutta, Joydeep

    2017-08-01

    The exchange role of gold (Au) and silver (Ag) in bimetallic films co-evaporated onto soda-lime glass substrates with Au-Ag volume ratios of 1:2, 1:1 and 2:1 have been demonstrated. Annealing of the films above the glass transition temperature in air led to non-alloying nature of the films, silver neutrals (Ag0) and gold nanoparticles (AuNPs) on the surface, along with silver nanoparticles (AgNPs) inside the glass matrix. Moreover, the size distribution and interparticle spacing of the AuNPs on the surface were governed by the Ag content in the deposited film. In contrast, the content of Au in the film played an opposite role leading to the migration of Ag ions (i.e. Ag0 being transformed to Ag ions after annealing in oxygen ambient) to form AgNPs inside the glass matrix. The higher the Au content in the film is, the more likely Ag0 to stay on the surface and impacts on the size distribution of AuNPs and consequently on the refractive index sensitivity measurements. Experimental realisation of this fact was reflected from the best performance for localized surface plasmon resonance (LSPR) sensitivity test achieved with Au-Ag ratio of 1:2. The Au/Ag/glass bimetallic dynamic results of this study can be pertinent to sensor applications integrated with optical devices.

  17. Dependence of the width of the glass transition interval on cooling and heating rates

    Science.gov (United States)

    Schmelzer, Jürn W. P.; Tropin, Timur V.

    2013-01-01

    In a preceding paper [J. W. P. Schmelzer, J. Chem. Phys. 136, 074512 (2012), 10.1063/1.3685510], a general kinetic criterion of glass formation has been advanced allowing one to determine theoretically the dependence of the glass transition temperature on cooling and heating rates (or similarly on the rate of change of any appropriate control parameter determining the transition of a stable or metastable equilibrium system into a frozen-in, non-equilibrium state of the system, a glass). In the present paper, this criterion is employed in order to develop analytical expressions for the dependence of the upper and lower boundaries and of the width of the glass transition interval on the rate of change of the external control parameters. It is shown, in addition, that the width of the glass transition range is strongly correlated with the entropy production at the glass transition temperature. The analytical results are supplemented by numerical computations. Analytical results and numerical computations as well as existing experimental data are shown to be in good agreement.

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

    Science.gov (United States)

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

    2012-05-01

    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.

  19. Kinetics of the glass transition of fragile soft colloidal suspensions

    Science.gov (United States)

    Saha, Debasish; Joshi, Yogesh M.; Bandyopadhyay, Ranjini

    2015-12-01

    Microscopic relaxation time scales are estimated from the autocorrelation functions obtained by dynamic light scattering experiments for Laponite suspensions with different concentrations (CL), added salt concentrations (CS), and temperatures (T). It has been shown in an earlier work [D. Saha, Y. M. Joshi, and R. Bandyopadhyay, Soft Matter 10, 3292 (2014)] that the evolutions of relaxation time scales of colloidal glasses can be compared with molecular glass formers by mapping the waiting time (tw) of the former with the inverse of thermodynamic temperature (1/T) of the latter. In this work, the fragility parameter D, which signifies the deviation from Arrhenius behavior, is obtained from fits to the time evolutions of the structural relaxation time scales. For the Laponite suspensions studied in this work, D is seen to be independent of CL and CS but is weakly dependent on T. Interestingly, the behavior of D corroborates the behavior of fragility in molecular glass formers with respect to equivalent variables. Furthermore, the stretching exponent β, which quantifies the width w of the spectrum of structural relaxation time scales, is seen to depend on tw. A hypothetical Kauzmann time tk, analogous to the Kauzmann temperature for molecular glasses, is defined as the time scale at which w diverges. Corresponding to the Vogel temperature defined for molecular glasses, a hypothetical Vogel time tα ∞ is also defined as the time at which the structural relaxation time diverges. Interestingly, a correlation is observed between tk and tα ∞ , which is remarkably similar to that known for fragile molecular glass formers. A coupling model that accounts for the tw-dependence of the stretching exponent is used to analyse and explain the observed correlation between tk and tα ∞ .

  20. 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...

  1. Multidiffusion mechanisms for noble gases (He, Ne, Ar) in silicate glasses and melts in the transition temperature domain: Implications for glass polymerization

    Science.gov (United States)

    Amalberti, Julien; Burnard, Pete; Laporte, Didier; Tissandier, Laurent; Neuville, Daniel R.

    2016-01-01

    of the silicate network itself as the glass transition temperature is approached: as the available free volume (available site for diffusive jumps) is modified, noble gas diffusion is no longer solely temperature-activated but also becomes sensitive to the kinetics of network rearrangements. The non-Arrhenian behavior of noble gas diffusion close to Tg is well described by a modified Vogel-Tammann-Fulcher (VTF) equation: Finally, our step heating diffusion experiments suggest that at T close to Tg, noble gas isotopes may suffer kinetic fractionation at a degree larger than that predicted by Graham's law. In the case of 40Ar and 36Ar, the traditional assumption based on Graham's law is that the ratio D40Ar/D36Ar should be equal to 0.95 (the square root of the ratio of the mass of 36Ar over the mass of 40Ar). In our experiment with glass G1, D40Ar/D36Ar rapidly decreased with decreasing temperature, from near unity (0.98 ± 0.14) at T > 1040 K to 0.76 when close to Tg (T = 1003 K). Replicate experiments are needed to confirm the strong kinetic fractionation of heavy noble gases close to the transition temperature.

  2. Thermodynamic signature of the dynamic glass transition in hard spheres

    NARCIS (Netherlands)

    Hermes, M|info:eu-repo/dai/nl/304829854; Dijkstra, M.|info:eu-repo/dai/nl/123538807

    2010-01-01

    We use extensive event-driven molecular dynamics simulations to study the thermodynamic, structural and dynamic properties of hard-sphere glasses. We determine the equation of state of the metastable fluid branch for hard spheres with a size polydispersity of 10%. Our results show a clear jump in

  3. Local order evolution of liquid Cu during glass transition under different pressures: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.D., E-mail: ydli@ustc.edu [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Lu, Q.L. [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Wang, C.C., E-mail: ccwang@ahu.edu.cn [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Huang, S.G. [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Liu, C.S. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei 230031 (China)

    2013-01-01

    Based on the second-moment approximation of tight-binding scheme, constant-pressure molecular dynamics simulations are performed for liquid Cu during the glass transition under different pressures. By means of pair analysis technique and bond orientational order analysis we find that the dominant bond pairs are those related to fcc and hcp crystalline order not those representing icosahedral short-range order (ISRO) when the systems enter into glass transition region. Although these two kinds of bond pairs compete with each other, the system tends towards a mixture of crystalline bond pairs during glass formation. The effect on various bond pairs brought about by higher pressure is much less for liquids than for glasses. The experimental observation of a shoulder on the second peak of the structure factor for supercooled liquids might not merely attribute to ISRO, since supercooled liquid Cu exhibits such a shoulder, but does not display an enhanced icosahedral symmetry.

  4. Physical aging and structural recovery in a colloidal glass subjected to volume-fraction jump conditions

    Science.gov (United States)

    Peng, Xiaoguang; McKenna, Gregory B.

    2016-04-01

    Three important kinetic phenomena have been cataloged by Kovacs in the investigation of molecular glasses during structural recovery or physical aging. These are responses to temperature-jump histories referred to as intrinsic isotherms, asymmetry of approach, and memory effect. Here we use a thermosensitive polystyrene-poly (N -isopropylacrylamide)-poly (acrylic acid) core-shell particle-based dispersion as a colloidal model and by working at a constant number concentration of particles we use temperature changes to create volume-fraction changes. This imposes conditions similar to those defined by Kovacs on the colloidal system. We use creep experiments to probe the physical aging and structural recovery behavior of colloidal glasses in the Kovacs-type histories and compare the results with those seen in molecular glasses. We find that there are similarities in aging dynamics between molecular glasses and colloidal glasses, but differences also persist. For the intrinsic isotherms, the times teq needed for relaxing or evolving into the equilibrium (or stationary) state are relatively insensitive to the volume fraction and the values of teq are longer than the α -relaxation time τα at the same volume fraction. On the other hand, both of these times grow at least exponentially with decreasing temperature in molecular glasses. For the asymmetry of approach, similar nonlinear behavior is observed for both colloidal and molecular glasses. However, the equilibration time teq is the same for both volume-fraction up-jump and down-jump experiments, different from the finding in molecular glasses that it takes longer for the structure to evolve into equilibrium for the temperature up-jump condition than for the temperature down-jump condition. For the two-step volume-fraction jumps, a memory response is observed that is different from observations of structural recovery in two-step temperature histories in molecular glasses. The concentration dependence of the dynamics

  5. Computational modelling of large deformations in layered-silicate/PET nanocomposites near the glass transition

    Science.gov (United States)

    Figiel, Łukasz; Dunne, Fionn P. E.; Buckley, C. Paul

    2010-01-01

    Layered-silicate nanoparticles offer a cost-effective reinforcement for thermoplastics. Computational modelling has been employed to study large deformations in layered-silicate/poly(ethylene terephthalate) (PET) nanocomposites near the glass transition, as would be experienced during industrial forming processes such as thermoforming or injection stretch blow moulding. Non-linear numerical modelling was applied, to predict the macroscopic large deformation behaviour, with morphology evolution and deformation occurring at the microscopic level, using the representative volume element (RVE) approach. A physically based elasto-viscoplastic constitutive model, describing the behaviour of the PET matrix within the RVE, was numerically implemented into a finite element solver (ABAQUS) using an UMAT subroutine. The implementation was designed to be robust, for accommodating large rotations and stretches of the matrix local to, and between, the nanoparticles. The nanocomposite morphology was reconstructed at the RVE level using a Monte-Carlo-based algorithm that placed straight, high-aspect ratio particles according to the specified orientation and volume fraction, with the assumption of periodicity. Computational experiments using this methodology enabled prediction of the strain-stiffening behaviour of the nanocomposite, observed experimentally, as functions of strain, strain rate, temperature and particle volume fraction. These results revealed the probable origins of the enhanced strain stiffening observed: (a) evolution of the morphology (through particle re-orientation) and (b) early onset of stress-induced pre-crystallization (and hence lock-up of viscous flow), triggered by the presence of particles. The computational model enabled prediction of the effects of process parameters (strain rate, temperature) on evolution of the morphology, and hence on the end-use properties.

  6. 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.

  7. First-order phase transitions in spin-glass models with multiple paramagnetic solutions

    Energy Technology Data Exchange (ETDEWEB)

    Lozza, H.F. [Departamento de Fisica, FCEyN, Universidad de Buenos Aires, Pab. I, Ciudad Universitaria - (1428) Buenos Aires (Argentina)]. E-mail: homero@df.uba.ar

    2004-12-31

    The paramagnetic and the one-step replica-symmetry-breaking spin-glass solutions of a p-spin-glass model in the presence of a transverse field are studied in the neighborhood of the phase transition curve. Two qualitatively different regions are found in the phase diagram. For a transition temperature higher than a certain value Tc, the thermodynamic transition is of second order, otherwise it is of first order with latent heat. The temperature Tc is joined to a point in the phase diagram where a transition between two paramagnetic solutions happens. A discussion about the order of the thermodynamic-phase transition in the quantum random orthogonal model is presented.

  8. First-order phase transitions in spin-glass models with multiple paramagnetic solutions

    Science.gov (United States)

    Lozza, H. F.

    2004-12-01

    The paramagnetic and the one-step replica-symmetry-breaking spin-glass solutions of a p-spin-glass model in the presence of a transverse field are studied in the neighborhood of the phase transition curve. Two qualitatively different regions are found in the phase diagram. For a transition temperature higher than a certain value Tc, the thermodynamic transition is of second order, otherwise it is of first order with latent heat. The temperature Tc is joined to a point in the phase diagram where a transition between two paramagnetic solutions happens. A discussion about the order of the thermodynamic-phase transition in the quantum random orthogonal model is presented.

  9. POLYMER CHAIN DIFFUSION AT A TEMPERATURE BELOW ITS BULK GLASS TRANSITION TEMPERATURE

    Institute of Scientific and Technical Information of China (English)

    Tisato Kajiyama; Daisuke Kawaguchi; Keiji Tanaka

    2003-01-01

    In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in the bulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtained results clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristic length scale of usual segmental motion even at a temperature below its bulk glass transition temperature, Tbg. This is consistent with our previous results that the surface glass transition temperature is much lower than the corresponding Tbg.Also, it was experimentally revealed that there was a gradient of molecular motion in the surface region.

  10. 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.

  11. Glass Transition Temperature of Water: from Simulations of Diffusion and Excess Entropy

    Institute of Scientific and Technical Information of China (English)

    LIU Jia; WANG Shu-Ying; ZHENG Cai-Ping; XIN Li-Juan; WANG Dan; SUN Min-Hua

    2007-01-01

    We report a computer simulation study of the glass transition of water with SP2 potential. The temperature dependences of the diffusion coefficient and the excess entropy on cooling process are calculated. It is found that both the diffusion coefficient and the excess entropy show a break point at 160K. Our results support the viewpoint that the glass transition temperature is 160K. According to the calculated viscosity, we obtain a fragility index of water to be 326, which is much larger than the value accepted before.

  12. Glass transition behavior of ternary disaccharide-ethylene glycol-water solutions

    Science.gov (United States)

    Yu, Tongxu; Zhao, Lishan; Wang, Qiang; Cao, Zexian

    2017-06-01

    Glass transition behavior of ternary disaccharide-ethylene glycol-water solutions, in reference to that of the binary combinations, has been investigated towards a better understanding of their cryoprotective ability. In water-deficient solutions, the disaccharides, including trehalose, sucrose and maltose, can associate with more than 100 ethylene glycol molecules to form amorphous complex, one order of magnitude larger than the corresponding hydration numbers. In water-rich solutions, a second glass transition emerges with increasing molar fraction of ethylene glycol, indicating the possible synergy of disaccharides and ethylene glycol in vitrification of the ternary aqueous solution.

  13. Measurement and modeling of the glass transition temperatures of multi-component solutions

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Binal N. [Department of Chemical and Environmental Engineering, University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606 (United States); Schall, Constance A. [Department of Chemical and Environmental Engineering, University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606 (United States)]. E-mail: cschall@eng.utoledo.edu

    2006-04-01

    Protein crystals are usually grown in multi-component aqueous solutions containing salts, buffers and other additives. To measure the X-ray diffraction data of the crystal, crystals are rapidly lowered to cryogenic temperatures. On flash cooling, ice frequently forms affecting the integrity of the sample. In order to eliminate this effect, substances called cryoprotectants are added to produce a glassy (vitrified) state rather than ice. Heretofore, the quantity of cryoprotectant needed to vitrify the sample has largely been established by trial and error. In this study, differential scanning calorimetry (DSC) was used to measure the melting (T {sub m}), devitrification (T {sub d}) and glass transition (T {sub g}) temperatures of solutions with a range of compositions typical of those used for growing protein crystals, with the addition of glycerol as cryoprotectant. The addition of cryoprotectant raises the T {sub g} and lowers the T {sub m} of bulk solution thereby decreasing the cooling rates required for vitrification of protein crystals. The theoretical T {sub g} value was calculated using the apparent volume fraction using the Miller/Fox equation extended for multi-component systems. The experimental values of T {sub g} were within approximately {+-}4% of that predicted by the model. Thus, the use of the model holds the promise of a rational method for the theoretical determination of the composition of cryoprotectant requirement of protein crystallization solutions.

  14. 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.

  15. 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.

  16. Manipulating the glass transition behavior of sulfonated polystyrene by functionalized nanoparticle inclusion

    Science.gov (United States)

    Kim, Sung-Kon; Nguyen, Ngoc A.; Wie, Jeong Jae; Park, Ho Seok

    2015-05-01

    Nanoscale interfaces can modify the phase transition behaviors of polymeric materials. Here, we report the double glass transition temperature (Tg) behavior of sulfonated polystyrene (sPS) by the inclusion of 14 nm amine-functionalized silica (NH2-SiO2) nanoparticles, which is different from the single Tg behaviors of neat sPS and silica (SiO2)-filled sPS. The inclusion of 20 wt% NH2-SiO2 nanoparticles results in an increase of Tg by 9.3 °C as well as revealing a second Tg reduced by 44.7 °C compared to the Tg of neat sPS. By contrast, when SiO2 nanoparticles with an identical concentration and size to NH2-SiO2 are dispersed, sPS composites possess a single Tg of 7.3 °C higher than that of the neat sPS. While a nanoscale dispersion is observed for SiO2 nanoparticles, as confirmed by microscopic and X-ray scattering analyses, NH2-SiO2 nanoparticles show the coexistence of micron-scale clustering along with a nanoscale dispersion of the individual nanoparticles. The micro-phase separation contributes to the free volume induced Tg reduction by the plasticization effect, whereas the Tg increase originates from the polymer segment mobility constrained by nanoconfinement and the rigid amorphous fractions deriving from strong polymer-particle interactions.Nanoscale interfaces can modify the phase transition behaviors of polymeric materials. Here, we report the double glass transition temperature (Tg) behavior of sulfonated polystyrene (sPS) by the inclusion of 14 nm amine-functionalized silica (NH2-SiO2) nanoparticles, which is different from the single Tg behaviors of neat sPS and silica (SiO2)-filled sPS. The inclusion of 20 wt% NH2-SiO2 nanoparticles results in an increase of Tg by 9.3 °C as well as revealing a second Tg reduced by 44.7 °C compared to the Tg of neat sPS. By contrast, when SiO2 nanoparticles with an identical concentration and size to NH2-SiO2 are dispersed, sPS composites possess a single Tg of 7.3 °C higher than that of the neat sPS. While a

  17. Spin-glass transition in Heisenberg spin system with ± J random bonds

    Science.gov (United States)

    Ghazali, A.; Lallemand, P.; Diep, H. T.

    1986-02-01

    We investigate by Monte Carlo simulations the simple cubic lattice with Heisenberg spins interacting via short range ± J random bonds for different antiferromagnetic bond concentrations x. We find that for x<0.25, a transition of the para-ferromagnetic type occurs. For 0.25⪅ x⩽0.5, the existence of a remanant magnetization and of a rounded peak of the specific heat together with other data support a paramagnetic-spin-glass transition at finite temperature.

  18. Water sorption and glass transition temperatures in red raspberry (Rubus idaeus)

    Energy Technology Data Exchange (ETDEWEB)

    Syamaladevi, Roopesh M. [Biological Systems Engineering Department, Washington State University, PO Box 646120, Pullman, WA 99164-6120 (United States); Sablani, Shyam S., E-mail: ssablani@wsu.edu [Biological Systems Engineering Department, Washington State University, PO Box 646120, Pullman, WA 99164-6120 (United States); Tang, Juming [Biological Systems Engineering Department, Washington State University, PO Box 646120, Pullman, WA 99164-6120 (United States); Powers, Joseph; Swanson, Barry G. [School of Food Science, Washington State University, PO Box 6463760, Pullman, WA 99164-6376 (United States)

    2010-05-20

    Water sorption isotherms and glass transition temperatures of raspberries were determined to understand interactions between water and biopolymers. Water adsorption and desorption isotherms of raspberries were determined with an isopiestic method. Thermal transitions of raspberries equilibrated at selected water concentrations using adsorption and desorption were determined by differential scanning calorimetry (DSC). The sorption isotherm data were modeled by BET and GAB equations, while the plasticizing influence of water on glass transition was modeled by the Gordon-Taylor equation. Equilibrium water concentrations varied at equivalent water activities during adsorption and desorption indicating occurrence of hysteresis and irreversibility of thermodynamic processes. The monolayer water concentrations of 0.099 and 0.108 kg water/kg dry raspberry solids obtained by BET and GAB models during desorption were larger than those during adsorption (0.059 and 0.074 kg water/kg dry raspberry solids). The glass transition temperature of raspberries decreased with increasing water concentrations. The Gordon-Taylor parameters T{sub gs} and k obtained for raspberries during adsorption were 42.6 {sup o}C and 4.73 and during desorption were 44.9 {sup o}C and 5.03, respectively. The characteristic glass transition temperature of the maximally freeze concentrated solution T{sup '}{sub g} was -63.1 {+-} 5 {sup o}C and the onset of ice crystal melting temperature T{sup '}{sub m} was -32.3 {+-} 0.4 {sup o}C. Although the water activity differed significantly at equivalent water concentrations obtained using absorption or desorption, the glass transition temperatures of raspberries were dependent on the concentration of water present not the method of equilibration.

  19. Glass Transition Temperature Depression at the Percolation Threshold in Carbon Nanotube-Epoxy Resin and Polypyrrole-Epoxy Resin Composites

    OpenAIRE

    Barrau, Sophie; Demont, Philippe; Maraval, Céline; Bernès, Alain; Lacabanne, Colette

    2005-01-01

    The glass transition temperatures of conducting composites, obtained by blending carbon nanotubes (CNTs) or polypyrrole (PPy) particles with epoxy resin, were investigated by using both differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). For both composites, dc and ac conductivity measurements revealed an electrical percolation threshold at which the glass transition temperature and mechanical modulus of the composites pass through a minimum.

  20. 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.

  1. Glass transition in driven granular fluids: A mode-coupling approach

    Science.gov (United States)

    Kranz, W. T.; Sperl, M.; Zippelius, A.

    2013-02-01

    We consider the stationary state of a fluid comprised of inelastic hard spheres or disks under the influence of a random, momentum-conserving external force. Starting from the microscopic description of the dynamics, we derive a nonlinear equation of motion for the coherent scattering function in two and three space dimensions. A glass transition is observed for all coefficients of restitution, ɛ, at a critical packing fraction φc(ɛ) below random close packing. The divergence of timescales at the glass transition implies a dependence on compression rate upon further increase of the density—similar to the cooling-rate dependence of a thermal glass. The critical dynamics for coherent motion as well as tagged particle dynamics is analyzed and shown to be nonuniversal with exponents depending on space dimension and degree of dissipation.

  2. 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

    2003-01-01

    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 Anal

  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

    The slow dynamics of glass-forming liquids is a complex subject of the condensed matter science. But the fragile-to-strong transition, which was observed not long ago [Ito, et al, Nature 1999], makes this subject even more complex since it is extremely challenging to directly probe the structural...

  4. 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.

  5. 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...

  6. Cooperative length scale of Aroclor near its dynamic glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Rizos, A.K. [Univ. of Crete, Heraklion (Greece); Ngai, K.L. [Naval Research Lab., Washington, DC (United States)

    1997-12-31

    Photon correlation spectroscopy in the depolarized mode has been used to monitor the reorientational dynamics of Aroclor (A1248) (polychlorinated biphenyls) that contain in solutions various amounts of low and high molecular weight (M{sub W}) polymers. For the high M{sub W} polymer/A1248 solutions the authors observe a very small dependence of the stretched exponential parameter {beta} on temperature. In contrast, the low M{sub W} polymer/A1248 solutions display a pronounced temperature dependence of {beta}. These preliminary experiments allow them to use the effect of modification of the solvent dynamics by added polymer to estimate the length scale of cooperative motion in glass forming systems from the size of the polymer chain.

  7. Volume variation of Gruneisen parameters of fcc transition metals

    Indian Academy of Sciences (India)

    C V Pandya; P R Vyas; T C Pandya; V B Gohel

    2002-02-01

    The volume variation of the Gruneisen parameters of ten fcc transition metals, up to 40% compression, has been studied on the basis of a model approach proposed by Antonov et al. The results are reasonably good for six metals except for Rh, Ag, Au and Ni when compared with available experimental and other theoretical values. The model requires an appropriate modification for Rh, Ag, Au and Ni.

  8. Estimation of liquid volume fraction using ultrasound transit time spectroscopy

    Science.gov (United States)

    Al-Qahtani, Saeed M.; Langton, Christian M.

    2016-12-01

    It has recently been proposed that the propagation of an ultrasound wave through complex structures, consisting of two-materials of differing ultrasound velocity, may be considered as an array of parallel ‘sonic rays’, the transit time of each determined by their relative proportion; being a minimum (t min) in entire higher velocity material, and a maximum (t max) in entire lower velocity material. An ultrasound transit time spectrum (UTTS) describes the proportion of sonic rays at an individual transit time. It has previously been demonstrated that the solid volume fraction of a solid:liquid composite, specifically acrylic step-wedges immersed in water, may be reliably estimated from the UTTS. The aim of this research was to investigate the hypothesis that the volume fraction of a two-component liquid mixture, of unequal ultrasound velocity, may also be estimated by UTTS. A through-transmission technique incorporating two 1 MHz ultrasound transducers within a horizontally-aligned cylindrical tube-housing was utilised, the proportion of silicone oil to water being varied from 0% to 100%. The liquid volume fraction was estimated from the UTTS at each composition, the coefficient of determination (R 2%) being 98.9  ±  0.7%. The analysis incorporated a novel signal amplitude normalisation technique to compensate for absorption within the silicone oil. It is therefore envisaged that the parallel sonic ray concept and the derived UTTS may be further applied to the quantification of liquid mixture composition assessment.

  9. 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.

  10. Molecular Dynamic Simulations of Glass Transition Temperature and Mechanical Properties in the Amorphous Region of Oil-Immersed Transformer Insulation Paper

    Science.gov (United States)

    Wang, You-Yuan; Yang, Tao; Liao, Rui-Jin

    2012-07-01

    The glass transition temperature (Tg) in the amorphous region of an insulation paper is one of the most important characteristics for thermal stability. Molecular dynamic simulations have been performed on three micro-structural models, namely, amorphous pure cellulose, amorphous cellulose with water and amorphous cellulose with oil, to study the microscopic mechanism of the glass transition process for oil-immersed transformer insulation paper. Using the method of specific volume versus temperature curve, the Tg of amorphous pure cellulose, cellulose with water, and cellulose with oil was determined as 448, 418 and 440 K, respectively. The current study may provide some information for thermal aging. The simulation results show that during the glass transition process, both the chain motion and mechanical properties of cellulose changes significantly. Relative to the oil molecules, water molecules immersed in the amorphous region of insulation paper can disrupt hydrogen bonds between cellulose chains. This phenomenon results in a significant reduction in the glass transition temperature and affects the thermal stability of the insulation paper.

  11. Impact-Induced Glass Transition in Elastomeric Coatings

    Science.gov (United States)

    Roland, C. M.

    2013-03-01

    When an elastomer layer is applied to the front surface of steel, the resistance to penetration by hard projectiles increases significantly. It is not obvious why a soft polymer should affect this property of metals, and most rubbers do not. However, we have found that a few are very effective; the requirement is that the polymer undergo a viscoelastic phase transition upon impact. This means that the frequency of its segmental dynamics correspond to the impact frequency. The latter is estimated as the ratio of the projectile velocity to the coating thickness, and is on the order of 105 s-1 for the experiments herein. Our data and a non-linear dynamics finite-element analysis offer support for this resonance condition as a primary mechanism underlying the penetration-resistance of elastomer-coated metal substrates. The impact-induced phase transition causes large energy absorption, decreasing the kinetic energy of the impacting projectile. However, this energy absorption only accounts for about half the enhanced stopping power of the elastomer/steel bilayer. An additional mechanism is lateral spreading of the impact force, resulting from the transient hardening of the elastomeric during its transition to the glassy state - the modulus of the rubber increases 1000-fold over a time period of microseconds. The penetration-resistance is a very nonlinear function of the coating thickness. Moreover, tests on various metals show that hardness is the principal substrate parameter controlling the contribution of the coating. This work was supported by the Office of Naval Research.

  12. Locating Malleable Bulk Metallic Glasses in Zr-Ti-Cu-Al Alloys with Calorimetric Glass Transition Temperature as an Indicator

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    We defined the plastic deformability under constrained loading conditions as malleability for bulk metallic glass (BMG) materials. Quaternary Zr-Ti-Cu-Al alloys in the Zr-rich composition range are selected to investigate the compositional dependence of malleability assessed by bending testing and glass transition temperature (Tg ). As indicated, increasing the Al or Cu concentration in the alloys leads to the rise of T g . The Zr(61)Ti2Cu(25)Al(12) (ZT1) and Zr(61.6)Ti(4.4)Cu(24)Al(10) (ZT3) alloys exhibit an optimal combination of lower T g and higher glass-forming ability. The malleable BMGs such as ZT1 manifests two characters during deformation, the stable propagation of a single shear band indicated by large shear offsets and easy proliferation of shear bands. With increasing the T g of BMG, the yield strength σy,Young's modulus and shear modulus simultaneously increase as well, while the Poisson s ratio decreases. The σy of ZT1 BMG is about 1680 MPa in compression and 1600 MPa in tension. In tensile loading, no any visible plasticity appears even when the strain rate increases up to the order of magnitude of 10(-1)s(-1). In consistent with the T g , malleability of Zr-Ti-Cu-Al BMGs manifests significant compositional dependence. The malleable BMG is associated with lower Tg , as well as lower shear modulus or higher Poisson s ratio, which can be understood on the basis of the correlation of Tg with shear energy barrier in metallic glass. Thus, the calorimetric Tg can be used as an indicator to screen malleable BMG-forming composition, with advantage of experimental accessibility.

  13. 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.

  14. 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.

  15. 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...... 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...

  16. 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...... of cooling rates (15−25 m/s) exhibit an anomalous crystallization behavior upon reheating as compared to the glasses formed at other cooling rates. This anomalous crystallization behavior implies the existence of a thermodynamic F−S transition, could be used as an alternative method for detecting the F...

  17. Critical Free Volume Concentration of Shear Banding Instability in Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    LIU Long-Fei; CAI Zhi-Peng; LI Hui-Qiang; ZHANG Guang-Ye; GUO Shi-Bo

    2011-01-01

    We present a model which predicts the critical free volume concentration of shear banding instability in metallic glasses(MGs). Fl-om the stability map, this model demonstrates that the prediction of shear band thickness is valid only for a short time after shear instability, and the diffusion of defects should be included in the mature shear band in MGs. The results agree well with the experimental observations and simulations.

  18. High-throughput in-volume processing in glass with isotropic spatial resolutions in three dimensions

    CERN Document Server

    Tan, Yuanxin; Chu, Wei; Liao, Yang; Qiao, Lingling; Cheng, Ya

    2016-01-01

    We report on fabrication of three dimensional (3D) microstructures in glass with isotropic spatial resolutions. To achieve high throughput fabrication, we expand the focal spot size with a low-numerical-aperture lens, which naturally results in a degraded axial resolution. We solve the problem with simultaneous spatial temporal focusing which leads to an isotropic laser-affected volume with a spatial resolution of ~100 micron.

  19. Melting of Pb Charge Glass and Simultaneous Pb-Cr Charge Transfer in PbCrO3 as the Origin of Volume Collapse.

    Science.gov (United States)

    Yu, Runze; Hojo, Hajime; Watanuki, Tetsu; Mizumaki, Masaichiro; Mizokawa, Takashi; Oka, Kengo; Kim, Hyunjeong; Machida, Akihiko; Sakaki, Kouji; Nakamura, Yumiko; Agui, Akane; Mori, Daisuke; Inaguma, Yoshiyuki; Schlipf, Martin; Rushchanskii, Konstantin Z; Ležaić, Marjana; Matsuda, Masaaki; Ma, Jie; Calder, Stuart; Isobe, Masahiko; Ikuhara, Yuichi; Azuma, Masaki

    2015-10-07

    A metal to insulator transition in integer or half integer charge systems can be regarded as crystallization of charges. The insulating state tends to have a glassy nature when randomness or geometrical frustration exists. We report that the charge glass state is realized in a perovskite compound PbCrO3, which has been known for almost 50 years, without any obvious inhomogeneity or triangular arrangement in the charge system. PbCrO3 has a valence state of Pb(2+)(0.5)Pb(4+)(0.5)Cr(3+)O3 with Pb(2+)-Pb(4+) correlation length of three lattice-spacings at ambient condition. A pressure induced melting of charge glass and simultaneous Pb-Cr charge transfer causes an insulator to metal transition and ∼10% volume collapse.

  20. Influence of fibre volume fraction and temperature on fatigue life of glass fibre reinforced plastics

    Directory of Open Access Journals (Sweden)

    Konrad Wegener

    2016-07-01

    Full Text Available The influence of fibre volume fraction and temperature on fatigue life of continuous glass fibre reinforced plastics is investigated in detail. The physical causes of the two effects on the slope of the S-N-curve in fibre direction at R = 0.1 are researched and can be explained with help of micrographs. A new phenomenological approach is presented to model both effects in fibre dominated laminates with different stacking sequences using only the static ultimate strength as an input. Static and fatigue tests of different layups and fibre volume fractions are performed at different temperatures to validate the fatigue life predictions. Additionally it is derived that there is an optimal fibre volume fraction regarding a minimum damage sum. This fibre volume fraction is dependent on a given loading spectra and can be calculated using the phenomenological model.

  1. The Effects of Electron Radiation on the Glass Transition Temperature of a Polyetherimide.

    Science.gov (United States)

    Kern, Kristen Tulloch

    The effects of electron radiation on a polyetherimide (PEI), Ultem^{cdot}, were investigated. In particular, the changes in the glass transition temperature (T_{g} ) with absorbed radiation dose were studied. The polymer was exposed to mono-energetic beams of 100-keV electrons and 1.0-MeV electrons for doses up to 100 megagray (MGy). Dosimetry for the exposures was based on Monte -Carlo simulations of the transfer of energy from an energetic electron to the polymer and on comparison to Nylon standards. Dynamic mechanical analysis was used to determine the T _{g} for non-exposed PEI and the changes in T_{g} resulting from irradiation. The T_{g} did not change significantly for doses up to and including 75 MGy, while a significant increase in T_ {g} occurred for a dose of 100 MGy. The cross-link and chain scission densities in the irradiated PEI were determined using infrared spectroscopy. The cross -link density increased with dose for all doses investigated. The chain scission density increased with dose for doses up to 75 MGy, but was lower for a dose of 100 MGy than for a dose of 75 MGy. Radical population kinetics, based in part on data from an electron paramagnetic resonance study, were correlated with the cross-link density and chain scission density to investigate the mechanism for the observed density variations with dose. The radical population simulations suggest that chain scissioning occurs less readily when the average radical separation during the exposure is less than three molecular radii. Finally, a model for the combined effects of cross-linking and chain scissioning is proposed which combines a statistical-mechanical model for the change in T_{g} with cross-link density and a free-volume model for the change in T _{g} with chain scission density.

  2. Coherent Beam Combining Element for Five 150-W Fiber Lasers by Volume Bragg Gratings in PTR Glass

    Science.gov (United States)

    2011-08-03

    glasses,” Glass Science and Technology 75 C1 (2002) 73-90. 8. O.M. Efimov , L.B. Glebov, V.I. Smirnov, and L.N. Glebova, “Process for production of...high efficiency volume diffractive elements in photo-thermo-refractive glass,” U.S. Patent 6,586,141 (2003). 9. O.M. Efimov , L.B. Glebov, and V.I

  3. Anomalous crystallization as a signature of the fragile-to-strong transition in metallic glass-forming liquids.

    Science.gov (United States)

    Yang, Xiunan; Zhou, Chao; Sun, Qijing; Hu, Lina; Mauro, John C; Wang, Chunzhen; Yue, Yuanzheng

    2014-08-28

    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 of cooling rates (15-25 m/s) exhibit an anomalous crystallization behavior upon reheating as compared to the glasses formed at other cooling rates. This anomalous crystallization behavior implies the existence of a thermodynamic F-S transition, could be used as an alternative method for detecting the F-S transition in MGFLs, and sheds light on the structure origin of the F-S transition. This work also contributes to obtaining a general thermodynamic picture of the F-S transition in supercooled liquids.

  4. Volume phase transitions of cholesteric liquid crystalline gels

    Energy Technology Data Exchange (ETDEWEB)

    Matsuyama, Akihiko, E-mail: matuyama@bio.kyutech.ac.jp [Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502 (Japan)

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  5. 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 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...... 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....

  6. RNA Denaturation: Excluded Volume, Pseudoknots, and Transition Scenarios

    Science.gov (United States)

    Baiesi, M.; Orlandini, E.; Stella, A. L.

    2003-11-01

    A lattice model of RNA denaturation which fully accounts for the excluded volume effects among nucleotides is proposed. A numerical study shows that interactions forming pseudoknots must be included in order to get a sharp continuous transition. Otherwise a smooth crossover occurs from the swollen linear polymer behavior to highly ramified, almost compact conformations with secondary structures. In the latter scenario, which is appropriate when these structures are much more stable than pseudoknot links, probability distributions for the lengths of both loops and main branches obey scaling with nonclassical exponents.

  7. 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...... absorber and a radical scavenger) to the coating were also explored. The extended model includes photoinitiated oxidation reactions, intrafilm oxygen permeability, water absorption and diffusion, reduction of crosslink density, absorption of ultraviolet radiation, a radical scavenger reaction......, and simulates the transient development of an oxidation zone. Simulations are in good agreement with experimental data for a fast degrading epoxy-amine coating with a glass transition temperature of −50°C. It was found that the degradation rate of the non-stabilized coating was influenced significantly...

  8. Amorphous to amorphous insulator-metal transition in GeSe3:Ag glasses

    Science.gov (United States)

    Prasai, Kiran; Chen, Gang; Drabold, D. A.

    2017-06-01

    We study an insulator-metal transition in a ternary chalcogenide glass (GeSe3)1 -xAgx for x =0.15 and 0.25. The conducting phase of the glass is obtained by using gap sculpting [Prasai et al., Sci. Rep. 5, 15522 (2015), 10.1038/srep15522] and it is observed that the metallic and insulating phases have nearly identical density functional energies but have a conductivity contrast of ˜108 . As such, we demonstrate an example of polyamorphism for which energetically close phases exhibit dramatically different optical properties. The transition from insulator to metal involves growth of an Ag-rich phase accompanied by a depletion of tetrahedrally bonded Ge (Se1/2)4 in the host network. The relative fraction of the amorphous Ag2Se phase and GeSe2 phase is shown to be a critical determinant of dc conductivity.

  9. Terahertz spectral change associated with glass transition of poly-ε-caprolactone

    Energy Technology Data Exchange (ETDEWEB)

    Komatsu, Marina, E-mail: mkomatsu@toki.waseda.jp [Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo 169-8555 (Japan); Mizuno, Maya; Fukunaga, Kaori [Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795 (Japan); Saito, Shingo [Advanced ICT Research Institute, National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795 (Japan); Ohki, Yoshimichi, E-mail: yohki@waseda.jp [Department of Electrical Engineering and Bioscience, Waseda University, Shinjuku, Tokyo 169-8555 (Japan); Research Institute for Materials Science and Technology, Waseda University, Shinjuku, Tokyo 169-8555 (Japan)

    2015-04-07

    We measured absorption spectra of unidirectionally stretched poly-ε-caprolactone (PCL) film in a range from 0.3 to 3.6 THz at temperatures from 10 to 300 K. Several absorption peaks were observed, when the electric field of THz waves was set in directions parallel and perpendicular to the stretching direction. The absorption bandwidths became significantly broad at around 200 K and above at least in two specific peaks. This temperature is close to the glass transition temperature of PCL. Further, it is shown by quantum chemical calculations that all the peaks obtained experimentally originate in skeletal vibrations of PCL. Therefore, it has become clear that a specific feature appears in the THz absorption spectrum of PCL associated with its glass transition.

  10. Study of the avalanche to streamer transition in the glass RPC exited by UV light

    CERN Document Server

    Ammosov, V; Kulemzin, A; Semak, A A; Sviridov, Yu; Zaetz, V G; Sviridov, Yu.

    2002-01-01

    A small glass RPC filled with Ar/Isob./Freon mixture has been exposed to a UV laser light. Avalanche and streamer regimes of discharge were reached in a fixed region of the RPC exited by the UV. A dependence of avalanche to streamer transition process on the laser beam intensity and on the applied high voltage was studied. Two types of the streamer signal have been observed. Using a CCD TV camera, pictures on multi-streamer propagation over RPC were obtained.

  11. Molecular dynamics simulations on specific heat capacity and glass transition tempera-ture of liquid silver

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The embedded-atom method is adopted to simulate the specific heat capacity of liquid silver. The relationship between the specific heat capacity and the temperature above and below melting point is derived. The results show that there exists an anormaly of the specific heat capacity of liquid silver near 950 K. Simulated pair distribution functions show that the liquid-to-glass transition takes place at this temperature.

  12. Retrogradation of Waxy Rice Starch Gel in the Vicinity of the Glass Transition Temperature

    OpenAIRE

    2013-01-01

    The retrogradation rate of waxy rice starch gel was investigated during storage at temperatures in the vicinity of the glass transition temperature of a maximally concentrated system (T g ′), as it was hypothesized that such temperatures might cause different effects on retrogradation. The T g ′ value of fully gelatinized waxy rice starch gel with 50% water content and the enthalpy of melting retrograded amylopectin in the gels were investigated using differential scanning calorimetry. Starch...

  13. 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....

  14. 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....

  15. 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

  16. Viscoelastic processes in non-ergodic states (percolation and glass transitions) of attractive micellar systems

    Science.gov (United States)

    Mallamace, F.; Broccio, M.; Tartaglia, P.; Chen, W. R.; Faraone, A.; Chen, S. H.

    2003-12-01

    We report a set of viscoelastic measurements in aqueous solutions of a copolymer micellar system with attractive interactions, a system characterized by a percolation line (PT), and a structural arrest (SA) in the particle diffusion motions of a kinetic glass transition (KGT). We observe, in both transitions, dramatic variations in both the elastic (or storage G‧( ω)) and loss components ( G″( ω)) of the shear moduli. At the PT, rheological data are characterized by a scaling behavior, whereas at the SA G‧ and G″ develop a plateau and a marked minimum, respectively. These behaviors are described in the frame of percolation models and mode coupling theory (MCT).

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

    Directory of Open Access Journals (Sweden)

    Yiming Li

    2016-02-01

    Full Text Available Tm3+ ions doped β-PbF2 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 Tm3+ 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 Oh to D4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.

  18. Cubic to tetragonal phase transition of Tm{sup 3+} doped nanocrystals in oxyfluoride glass ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua, E-mail: zhaolj@nankai.edu.cn, E-mail: yuhua@nankai.edu.cn [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071 (China); Zhao, Lijuan, E-mail: zhaolj@nankai.edu.cn, E-mail: yuhua@nankai.edu.cn [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071 (China); Applied Physics School of TEDA, Nankai University, Tianjin 300457 (China)

    2016-02-15

    Tm{sup 3+} ions doped β-PbF{sub 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{sup 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{sub h} to D{sub 4h} site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm{sup 3+} doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.

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

    Science.gov (United States)

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

    2016-04-01

    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 reversibility and hysteresis of the sharp symmetry change from anisotropic solid to isotropic liquid dynamics observed in the oscillatory shear of colloidal glasses (D. Denisov, M.T. Dang, B. Struth, A. Zaccone, P. Schall, Sci. Rep. 5 14359 (2015)). We use strain sweeps with increasing and decreasing strain amplitude to show that, in analogy with equilibrium transitions, this sharp symmetry change is reversible and exhibits systematic frequency-dependent hysteresis. Using the non-affine response formalism of amorphous solids, we show that these hysteresis effects arise from frequency-dependent non-affine structural cage rearrangements at large strain. These results consolidate the first-order-like nature of the oscillatory shear transition and quantify related hysteresis effects both via measurements and theoretical modelling.

  20. Kinetics of Ge20Se80–As ( = 0, 5, 10, 15 and 20) in glass transition region

    Indian Academy of Sciences (India)

    Kedar Singh; N S Saxena

    2003-08-01

    The results of differential scanning calorimetric (DSC) measurements on Ge20Se80–As ( = 0, 5, 10, 15 and 20) system with the specific aim of investigating the effect of heating rate and composition on glass transition temperature have been discussed. The results indicate that the glass transition temperature () is dependent both on the heating rate and composition. The glass transition activation energy () and heat absorbed in glass transition region () are higher for Ge20Se65As15 as compared to the values of other compositions of arsenic. An effort has also been made to develop an empirical model for the composition dependence of . A good agreement has been observed between the experimental values and the results of model calculation.

  1. Thermodynamic aspects of the glass transition phenomenon. II. Molecular liquids with variable interactions

    Science.gov (United States)

    Alba-Simionesco, C.; Fan, J.; Angell, C. A.

    1999-03-01

    As a contribution to the understanding of the thermodynamics of the glass transition phenomenon a series of molecules having the same steric character, but differing in the strength and nature of intermolecular interactions, has been investigated. The series is based on systematic changes of substituents on disubstituted benzene ring compounds, the simplest example of which is meta-xylene. Meta-isomers are chosen in each instance because of their greater tendency to supercool. In particular, m-fluoroaniline cannot be crystallized at ambient pressure. The principal measurements performed were of heat capacity and enthalpy change, using the technique of differential scanning calorimetry, and these have been examined in the light of literature data on the liquid viscosities and some recent data for dielectric relaxation. As the strength of hydrogen-bonding interactions between the ring substituents on adjacent molecules increases, the glass transition temperature Tg increases by almost 100 degrees from the lowest value in the series, 122.5 K, for m-fluorotoluene. Empirical rules involving Tb/Tm and Tg/Tm are found wanting. The important thermodynamic characteristic of the glass transition, viz., the change in heat capacity at the glass transition, ΔCp, remains approximately constant until the -OH substituent is introduced, whereupon a new element appears. This is a specific component of ΔCp which appears at temperatures above an initially small jump at Tg. It is well accounted for by the addition of a two-state H-bond breaking component (with the usual H⋯-OH bond energy) to the total excess heat capacity. The liquid ground state (or Kauzmann) temperature TK assessed from thermodynamic data acquired in this study, falls 20%-30% below the glass transition temperature. From the limited transport data available, these liquids appear to be quite fragile in character implying that the phenyl group influence dominates the hydrogen bond factor which has often seemed

  2. Plasma waves excited at interface by femtosecond laser irradiation enabling formation of volume nanograting in glass

    CERN Document Server

    Liao, Yang; Qiao, Lingling; Huang, Min; Bellouard, Yves; Sugioka, Koji; Cheng, Ya

    2014-01-01

    Irradiation of intense ultrafast laser pulses in glasses can lead to formation of nanogratings whose periods are significantly smaller than the incident irradiation wavelength. The mechanism of the exotic phenomenon is still under debate. Here, we access the snapshots of morphologies in the laser affected regions in a porous glass which reveal the evolution of the formation of nanogratings with increasing number of laser pulses. Combined with further theoretical analyses, our observation provides important clues which suggest that excitation of standing plasma waves at the interfaces between areas modified and unmodified by the femtosecond laser irradiation plays a crucial role for promoting the growth of periodic nanogratings. The finding indicates that the formation of volume nanogratings induced by irradiation of femtosecond laser pulses is initiated with a mechanism similar to the formation of surface nanoripples.

  3. Single-frequency dielectric relaxation used to characterize the glass transition time of polydextrose

    Science.gov (United States)

    Buehler, Martin G.; Campbell, Zachary J.; Carter, Brady P.

    2017-02-01

    Dielectric relaxation methods are applicable to powdery materials such as carbohydrates. These materials have relaxations that occur in the milli-Hz range while samples are held at fixed temperatures and fixed water activities, a w, (relativity humidity). Under proper conditions these materials undergo physical changes where the initially glassy powder transitions to an amorphous equilibrium state at the glass transition temperature, T g. Determining this transition involves characterizing the boundary curve (T g versus a w) which determines T g and a w conditions where materials are stable with long-shelf life or unstable with very a short shelf-life. This paper serves to illustrate multiple methodologies which can be used to characterize glass transition from frequency-spectra. Three methodologies are described: peak-broadening, peak-shift, and single-frequency. The new single frequency method not only provides results that identical to those of the peak-shift method but increases the data acquisition speeds by a factor of 5. This method is illustrated on polydextrose, a common sugar substitute. The information gathered can then be used to construct the boundary curve which is used to characterize the shelf-life of a material at various conditions.

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

    Energy Technology Data Exchange (ETDEWEB)

    Peter, S [Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex (France); Meyer, H [Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex (France); Baschnagel, J [Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex (France); Seemann, R [Max Planck Institute for Dynamics and Self-Organization, D-37018 Goettingen (Germany)

    2007-05-23

    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{sub 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{sub 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{sub c}(y) can be expressed in terms of the depression of T{sub c}(h)-the global T{sub c} for a film of thickness h-if we assume that T{sub c}(h) is the arithmetic mean of T{sub c}(y) and parameterize the depression of T{sub c}(h) by T{sub c}(h) = T{sub c}/(1+h{sub 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.

  5. Polymer glass transition occurs at the marginal rigidity point with connectivity z* = 4.

    Science.gov (United States)

    Lappala, Anna; Zaccone, Alessio; Terentjev, Eugene M

    2016-09-21

    We re-examine the physical origin of the polymer glass transition from the point of view of marginal rigidity, which is achieved at a certain average number of mechanically active intermolecular contacts per monomer. In the case of polymer chains in a melt/poor solvent, each monomer has two neighbors bound by covalent bonds and also a number of central-force contacts modelled by the Lennard-Jones (LJ) potential. We find that when the average number of contacts per monomer (covalent and non-covalent) exceeds the critical value z* ≈ 4, the system becomes solid and the dynamics arrested - a state that we declare the glass. Coarse-grained Brownian dynamics simulations show that at sufficient strength of LJ attraction (which effectively represents the depth of quenching, or the quality of solvent) the polymer globule indeed crosses the threshold of z*, and becomes a glass with a finite zero-frequency shear modulus, G∝ (z-z*). We verify this by showing the distinction between the 'liquid' polymer droplet at z z*, which changes shape and adopts the spherical conformation in equilibrium, and the glassy 'solid' droplet at z > z*, which retains its shape frozen at the moment of z* crossover. These results provide a robust microscopic criterion to tell the liquid apart from the glass for the linear polymers.

  6. Theory of activated dynamics and glass transition of hard colloids in two dimensions.

    Science.gov (United States)

    Zhang, Bo-kai; Li, Hui-shu; Tian, Wen-de; Chen, Kang; Ma, Yu-qiang

    2014-03-07

    The microscopic nonlinear Langevin equation theory is applied to study the localization and activated hopping of two-dimensional hard disks in the deeply supercooled and glass states. Quantitative comparisons of dynamic characteristic length scales, barrier, and their dependence on the reduced packing fraction are presented between hard-disk and hard-sphere suspensions. The dynamic barrier of hard disks emerges at higher absolute and reduced packing fractions and correspondingly, the crossover size of the dynamic cage which correlates to the Lindemann length for melting is smaller. The localization lengths of both hard disks and spheres decrease exponentially with packing fraction. Larger localization length of hard disks than that of hard spheres is found at the same reduced packing fraction. The relaxation time of hard disks rises dramatically above the reduced packing fraction of 0.88, which leads to lower reduced packing fraction at the kinetic glass transition than that of hard spheres. The present work provides a foundation for the subsequent study of the glass transition of binary or polydisperse mixtures of hard disks, normally adopted in experiments and simulations to avoid crystallization, and further, the rheology and mechanical response of the two-dimensional glassy colloidal systems.

  7. 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.

  8. Finite size scaling study of dynamical phase transitions in two dimensional models: ferromagnet, symmetric and non symmetric spin glasses

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, A.U.; Derrida, B.

    1988-10-01

    We study the time evolution of two configurations submitted to the same thermal noise for several two dimensional models (Ising ferromagnet, symmetric spin glass, non symmetric spin glass). For all these models, we find a non zero critical temperature above which the two configurations always meet. Using finite size scaling ideas, we determine for these three models this dynamical phase transition and some of the critical exponents. For the ferromagnet, the transition T/sub c/ approx. = 2.25 coincides with the Curie temperature whereas for the two spin glass models +- J distribution of bonds) we obtain T/sub c/ approx. = 1.5-1.7.

  9. Transmitting volume Bragg gratings in PTR glass written with femtosecond Bessel beams

    Science.gov (United States)

    Cheng, G. H.; Zhang, Y. J.; Liu, Q.

    2017-05-01

    Transmitting volume Bragg gratings were fabricated in photo-thermo-refractive glass using femtosecond laser Bessel beams and thermal treatment. The phase contrast images of gratings under different writing power were investigated before and after annealing. Microstructures composed of nano-sized crystals were observed in the exposed regions. Optimized writing power (100 mW) achieved dense nano-crystals distribution. A maximum diffraction efficiency of 92.36% was achieved with 1 mm grating thickness at period of 5 μm.

  10. Free-volume evolution and its temperature dependence during rolling of Cu60Zr20Ti20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhou, Y.H.

    2005-01-01

    The free-volume evolution during rolling Cu60Zr20Ti20 bulk metallic glass at room and cryogenic temperatures has been investigated by differential scanning calorimetry. When the specimen is rolled at cryogenic temperature, the free-volume content increases as the rolling proceeds first...

  11. Comprehensive data base of high-level nuclear waste glasses: September 1987 status report: Volume 2, Additional appendices

    Energy Technology Data Exchange (ETDEWEB)

    Kindle, C.H.; Kreiter, M.R.

    1987-12-01

    The Materials Characterization Center (MCC) is assembling a comprehensive data base (CDB) of experimental data collected for high-level nuclear waste package components. The status of the CDB is summarized in Volume I of this report. Volume II contains appendices that present data from the data base and an evaluation of glass durability models applied to the data base.

  12. Disorder-assisted melting and the glass transition in amorphous solids

    Science.gov (United States)

    Zaccone, Alessio; Terentjev, Eugene

    2013-03-01

    The mechanical response of solids depends on temperature because the way atoms and molecules respond collectively to deformation is affected at various levels by thermal motion. This is a fundamental problem of solid state science and plays a crucial role in metallurgy, aerospace engineering, energy. In disordered solids (glass, amorphous semiconductors, ceramics, metallic glass, polymers) the vanishing of rigidity as a function of temperature is not well understood because continuum elasticity is inapplicable due to the disorder leading to nontrivial (nonaffine) components in the atomic displacements. Our theory explains the basic mechanism of the melting transition of amorphous solids in terms of the lattice energy lost to nonaffine motion, compared to which thermal vibrations turn out to play a negligible role. The theory is in good agreement with data on melting of amorphous polymers (where no alternative theory can be found in the literature) and offers new opportunities in materials science.

  13. 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.

  14. On the glass transition of the one-component metallic melts

    Science.gov (United States)

    Fedorchenko, A. I.

    2017-10-01

    In this paper, the conditions for one-component metallic melts vitrification by quenching from a liquid state were formulated. It is shown that the tendency to the glass formation drastically increases with the temperature of melting. The maximum glass layer thickness and the associated cooling rates along with the vitrification temperatures was determined for Al, Cu, and Ni melts deposited on the Cu substrate. The results are in agreement with the available experimental data. Based on analytical solution of the impinging droplet solidification, the numerical value of the early-introduced asymptotic Ω criterion, which separates equilibrium and non-equilibrium phase transitions, was determined. Good agreement between the calculated and experimental values of the thickness of the splats shows that Ω criterion indeed predicts a priori a scenario of solidification.

  15. Glass Transitions in Monodisperse Cluster-Forming Ensembles: Vortex Matter in Type-1.5 Superconductors

    Science.gov (United States)

    Díaz-Méndez, Rogelio; Mezzacapo, Fabio; Lechner, Wolfgang; Cinti, Fabio; Babaev, Egor; Pupillo, Guido

    2017-02-01

    At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster crystal. In the present Letter, we explore the out-of-equilibrium dynamics for a two-dimensional realization, which is relevant to superconducting materials with multiscale intervortex forces. We find that, for small temperatures following a quench, the suppression of the thermally activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in terms of an "effective polydispersity" induced by multiscale interactions. This demonstrates that a vortex glass can form in clean systems of thin films of "type-1.5" superconductors. An additional setup to study this physics can be layered superconducting systems, where the shape of the effective vortex-vortex interactions can be engineered.

  16. Spin-glass transition in bond-disordered Heisenberg antiferromagnets coupled with local lattice distortions on a pyrochlore lattice.

    Science.gov (United States)

    Shinaoka, Hiroshi; Tomita, Yusuke; Motome, Yukitoshi

    2011-07-22

    Motivated by puzzling characteristics of spin-glass transitions widely observed in pyrochlore-based frustrated materials, we investigate the effects of coupling to local lattice distortions in a bond-disordered antiferromagnet on the pyrochlore lattice by extensive Monte Carlo simulations. We show that the spin-glass transition temperature T(f) is largely enhanced by the spin-lattice coupling and, furthermore, becomes almost independent of Δ in a wide range of the disorder strength Δ. The critical property of the spin-glass transition is indistinguishable from that of the canonical Heisenberg spin glass in the entire range of Δ. These peculiar behaviors are ascribed to a modification of the degenerate manifold from a continuous to semidiscrete one by spin-lattice coupling.

  17. Phase field crystal modelling of the order-to-disordered atomistic structure transition of metallic glasses

    Science.gov (United States)

    Zhang, W.; Mi, J.

    2016-03-01

    Bulk metallic glass composites are a new class of metallic alloy systems that have very high tensile strength, ductility and fracture toughness. This unique combination of mechanical properties is largely determined by the presence of crystalline phases uniformly distributed within the glassy matrix. However, there have been very limited reports on how the crystalline phases are nucleated in the super-cooled liquid and their growth dynamics, especially lack of information on the order-to-disordered atomistic structure transition across the crystalline-amorphous interface. In this paper, we use phase field crystal (PFC) method to study the nucleation and growth of the crystalline phases and the glass formation of the super cooled liquid of a binary alloy. The study is focused on understanding the order-to-disordered transition of atomistic configuration across the interface between the crystalline phases and amorphous matrix of different chemical compositions at different thermal conditions. The capability of using PFC to simulate the order-to-disorder atomistic transition in the bulk material or across the interface is discussed in details.

  18. The glass transition and diffusion in simulated liquid TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Vo Van Hoang [Department of Physics, Institute of Technology, National University of HochiMinh City, 268 Ly Thuong Kiet Street, District 10, HochiMinh City (Viet Nam)

    2007-10-17

    The glass transition and diffusion in liquid TiO{sub 2} have been studied in a model containing 3000 atoms via molecular dynamics (MD) simulation. The density dependence of the glass transition temperature, T{sub g}, of liquid TiO{sub 2} has been found and is discussed. Diffusion of atomic species in 3.80 g cm{sup -3} TiO{sub 2} models has been investigated over a wide temperature range from 2100 to 7000 K. We found that the temperature dependence of the diffusion constant of atomic species follows an Arrhenius law at relatively low temperatures above the melting point, and at higher temperatures it deviates from an Arrhenius law. Differences between the structures of amorphous TiO{sub 2} models at three different densities in the range from 3.80 to 4.20 g cm{sup -3} have been found and are discussed. In addition, a transition from a low-density liquid (ldl) form to a high-density liquid (hdl) form was found and is discussed.

  19. Effects of temperature and pressure on the glass transitions of plastic bonded explosives

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, M.S.; Garcia, D.; Idar, D.

    1998-12-31

    Various plastic bonded explosives (PBXs) contain about 5-wt% polymer, plasticizer, and stabilizer as binder. The glass-transition temperature (T{sub g}) determines, in part, if the binder will reduce or increase the sensitivity of the PBX to impact. A soft binder reduces the impact sensitivity; however, too soft a binder compromises the mechanical strength below that desirable for dimensional stability. Glass transitions were measured by temperature modulated DSC for PBXs before and after pressing. Pressing temperature was 90 C. The T{sub g} of Estane, a polyester/polyurethane used in some PBX binders, was investigated. Only small changes were observed in the low temperature T{sub g} of the soft segments but larger changes were seen in the higher temperature transitions due to the relaxation of the hard segments. The T{sub g} of Kel F 800, a binder used in insensitive PBX 9502, was observed near ambient temperature. The PBX 9502 had a lower T{sub g} than the neat polymer. Mechanical strength will be measured for the samples.

  20. On the Pr3+ interconfigurational optical transitions in glasses and an comparative study of the Photon Cascade Emission in crystals and glasses

    Science.gov (United States)

    Srivastava, A. M.

    2013-04-01

    This paper offers a study that compares the nature of Pr3+ luminescence in crystalline and glass modifications of LaB3O6, LiLaP4O12 and SrB4O7. In the crystalline derivative of these materials, the crystal-field split Pr3+ 4f15d1 state is higher in energy than the 1S0 state. The resulting energy level structure permits the observation of the Pr3+ 1S0 → 1I6 emission transition and the production of two photons for every absorbed UV photon, a process which is referred to as Photon Cascade Emission. In the corresponding glass derivatives, the Pr3+ 4f15d1 lies below the 1S0 state with the consequence that the emission is dominated by the interconfigurational (broad-band) Pr3+ 4f15d1 → 4f2 transition. The reason for this is traced to increased strength of the crystalline field at the Pr3+ site in the glass phase. The increased crystal-field strength is traceable to decreased local coordination number and to shorter Pr3+-O2- bond distances. In this paper we also analyze the results of the Pr3+ ion luminescence in fluoride, oxyfluoride, borate and phosphate glasses. With the exception of one pure fluoride glass (ZBLAN), the Pr3+ luminescence in all these glasses is dominated by the interconfigurational Pr3+ 4f15d1 → 4f2 emission transition. It is pointed out that under broad-band excitation, emission from the Pr3+ 1S0 state has yet to be observed in an oxide based glass (phosphates and borates).

  1. Differential scanning calorimetry study of glass transition in frozen starch gels.

    Science.gov (United States)

    Tananuwong, Kanitha; Reid, David S

    2004-06-30

    The effects of initial water content, maximum heating temperature, amylopectin crystallinity type, and annealing on the glass transition of starch gels were studied by differential scanning calorimetry (DSC). The glass transition temperatures of the frozen gels measured as the onset (T(g,onset)) or midpoint temperature (T(g,midpoint)), heat capacity change during the glass transition (deltaC(p)), unfrozen water of starch gels, and additional unfrozen water (AUW) arising from gelatinization were reported. The results show that T(g,onset) and T(g,midpoint) of the partially gelatinized gels are independent of the initial water content, while both of the T(g) values of the fully gelatinized gel increase as the initial water content increases. These observations might result from the difference in the level of structural disruption associated with different heating conditions, resulting in different gel structures as well as different concentrations of the sub-T(g) unfrozen matrix. The amylopectin crystallinity type does not greatly affect T(g,onset) and T(g,midpoint) of the gels. Annealing at a temperature near T(g,onset) increases both T(g,onset) and T(g,midpoint) of the gels, possibly due to an increase in the extent of the freeze concentration as evidenced by a decrease in AUW. Annealing results in an increase in the deltaC(p) value of the gels, presumably due to structural relaxation. A devitrification exotherm may be related to AUW. The annealing process decreases AUW, thus also decreasing the size of the exotherm.

  2. Interfacial and topological effects on the glass transition in free-standing polystyrene films

    Science.gov (United States)

    Lyulin, Alexey V.; Balabaev, Nikolay K.; Baljon, Arlette R. C.; Mendoza, Gerardo; Frank, Curtis W.; Yoon, Do Y.

    2017-05-01

    United-atom molecular-dynamics computer simulations of atactic polystyrene (PS) were performed for the bulk and free-standing films of 2 nm-20 nm thickness, for both linear and cyclic polymers comprised of 80 monomers. Simulated volumetric glass-transition temperatures (Tg) show a strong dependence on the film thickness below 10 nm. The glass-transition temperature of linear PS is 13% lower than that of the bulk for 2.5 nm-thick films, as compared to less than 1% lower for 20 nm films. Our studies reveal that the fraction of the chain-end groups is larger in the interfacial layer with its outermost region approximately 1 nm below the surface than it is in the bulk. The enhanced population of the end groups is expected to result in a more mobile interfacial layer and the consequent dependence of Tg on the film thickness. In addition, the simulations show an enrichment of backbone aliphatic carbons and concomitant deficit of phenyl aromatic carbons in the interfacial film layer. This deficit would weaken the strong phenyl-phenyl aromatic (π -π ) interactions and, hence, lead to a lower film-averaged Tg in thin films, as compared to the bulk sample. To investigate the relative importance of the two possible mechanisms (increased chain ends at the surface or weakened π -π interactions in the interfacial region), the data for linear PS are compared with those for cyclic PS. For the cyclic PS, the reduction of the glass-transition temperature is also significant in thin films, albeit not as much as for linear PS. Moreover, the deficit of phenyl carbons in the film interface is comparable to that observed for linear PS. Therefore, chain-end effects alone cannot explain the observed pronounced Tg dependence on the thickness of thin PS films; the weakened phenyl-phenyl interactions in the interfacial region seems to be an important cause as well.

  3. Fabrication, testing, and analysis of anisotropic carbon/glass hybrid composites: volume 1: technical report.

    Energy Technology Data Exchange (ETDEWEB)

    Wetzel, Kyle K. (Wetzel Engineering, Inc. Lawrence, Kansas); Hermann, Thomas M. (Wichita state University, Wichita, Kansas); Locke, James (Wichita state University, Wichita, Kansas)

    2005-11-01

    Anisotropic carbon/glass hybrid composite laminates have been fabricated, tested, and analyzed. The laminates have been fabricated using vacuum-assisted resin transfer molding (VARTM). Five fiber complexes and a two-part epoxy resin system have been used in the study to fabricate panels of twenty different laminate constructions. These panels have been subjected to physical testing to measure density, fiber volume fraction, and void fraction. Coupons machined from these panels have also been subjected to mechanical testing to measure elastic properties and strength of the laminates using tensile, compressive, transverse tensile, and in-plane shear tests. Interlaminar shear strength has also been measured. Out-of-plane displacement, axial strain, transverse strain, and inplane shear strain have also been measured using photogrammetry data obtained during edgewise compression tests. The test data have been reduced to characterize the elastic properties and strength of the laminates. Constraints imposed by test fixtures might be expected to affect measurements of the moduli of anisotropic materials; classical lamination theory has been used to assess the magnitude of such effects and correct the experimental data for the same. The tensile moduli generally correlate well with experiment without correction and indicate that factors other than end constraints dominate. The results suggest that shear moduli of the anisotropic materials are affected by end constraints. Classical lamination theory has also been used to characterize the level of extension-shear coupling in the anisotropic laminates. Three factors affecting the coupling have been examined: the volume fraction of unbalanced off-axis layers, the angle of the off-axis layers, and the composition of the fibers (i.e., carbon or glass) used as the axial reinforcement. The results indicate that extension/shear coupling is maximized with the least loss in axial tensile stiffness by using carbon fibers oriented 15{sup

  4. A simple real space density functional theory of freezing, with implications for the glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Stoessel, J.P.; Wolynes, P.G.

    1989-01-01

    With analogy to the ''highly accurate'' summation of cluster diagrams for hard sphere fluids a la Carnahan-Starling, we present a simple, real space free energy density functional for arbitrary potential systems, based on the generalization of the second virial coefficient to inhomogeneous systems which, when applied to hard sphere, soft-sphere, and Lennard-Jones freezing, yield melting characteristics in remarkable agreement with experiment. Implications for the liquid-glass transition in all three potential systems are also presented. 45 refs., 7 figs., 1 tab.

  5. Predicting the glass transition temperature as function of crosslink density and polymer interactions in rubber compounds

    Science.gov (United States)

    D'Escamard, Gabriella; De Rosa, Claudio; Auriemma, Finizia

    2016-05-01

    Crosslink sulfur density in rubber compounds and interactions in polymer blends are two of the composition elements that affect the rubber compound properties and glass transition temperature (Tg), which is a marker of polymer properties related to its applications. Natural rubber (NR), butadiene rubber (BR) and styrene-butadiene rubber (SBR) compounds were investigated using calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicate that the Di Marzio's and Schneider's Models predict with accuracy the dependence of Tg on crosslink density and composition in miscible blends, respectively, and that the two model may represent the base to study the relevant "in service" properties of real rubber compounds.

  6. 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.

  7. Liquid droplets on a free-standing glassy membrane: Deformation through the glass transition.

    Science.gov (United States)

    Fortais, Adam; Schulman, Rafael D; Dalnoki-Veress, Kari

    2017-07-01

    In this study, micro-droplets are placed on thin, glassy, free-standing films where the Laplace pressure of the droplet deforms the free-standing film, creating a bulge. The film's tension is modulated by changing temperature continuously from well below the glass transition into the melt state of the film. The contact angle of the liquid droplet with the planar film as well as the angle of the bulge with the film are measured and found to be consistent with the contact angles predicted by a force balance at the contact line.

  8. Random pinning glass transition: hallmarks, mean-field theory and renormalization group analysis.

    Science.gov (United States)

    Cammarota, Chiara; Biroli, Giulio

    2013-03-28

    We present a detailed analysis of glass transitions induced by pinning particles at random from an equilibrium configuration. We first develop a mean-field analysis based on the study of p-spin spherical disordered models and then obtain the three-dimensional critical behavior by the Migdal-Kadanoff real space renormalization group method. We unveil the important physical differences with the case in which particles are pinned from a random (or very high temperature) configuration. We contrast the pinning particles approach to the ones based on biasing dynamical trajectories with respect to their activity and on coupling to equilibrium configurations. Finally, we discuss numerical and experimental tests.

  9. 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...

  10. Infrared absorption spectra of transition metals-doped soda lime silica glasses

    Science.gov (United States)

    Khalil, E. M. A.; ElBatal, F. H.; Hamdy, Y. M.; Zidan, H. M.; Aziz, M. S.; Abdelghany, A. M.

    2010-03-01

    Infrared (IR) absorption spectra of some prepared undoped and transition metals-doped soda-lime-silicate glasses have been studied in the region of 400-4000 cm -1. IR spectra were analyzed to determine and differentiate the various vibrational modes by applying a deconvolution method to the IR spectra. Although the first sight reveals close similarity between the different transition metal- (TM) doped samples; careful inspection indicates some minor differences depending on the type of TM ions. These observed data are correlated with similar energy of the 3d orbitals of TM atoms in the neutral state and when the atoms are ionized, the 3d orbitals becomes more stable than the 4 s orbitals.

  11. Optical transitions and upconversion properties of Er3+-doped chloride tellurite glasses

    Institute of Scientific and Technical Information of China (English)

    Wen Lei; Li Shun-Guang; Huang Guo-Song; Hu Li-Li; Jiang Zhong-Hong

    2004-01-01

    Er3+-doped lead chloride tellurite glasses were prepared using the conventional melting and quenching method.The absorption spectra were measured and the Judd-Ofelt analysis was performed. The spectroscopic parameters such as the intensity parameters, transition probabilities, radiative lifetimes, and branching ratios were obtained. Intense infrared emission and visible upconversion luminescence under 976nm excitation were observed. For the 1.55μm emission, the full width at half maximum and the emission cross sections are more than 50 nm and 8×10-20cm2,respectively. Three efficient visible luminescences centred at 525, 547, and 658 nm are assigned to the transitions from the excited states 2H11/2, 4S3/2, and 4F9/2 to the ground state 4I15/2, respectively. The upconversion mechanisms and the power-dependent intensities are also discussed and evaluated.

  12. Structural transition and orbital glass physics in near-itinerant CoV2O4

    Science.gov (United States)

    Reig-i-Plessis, D.; Casavant, D.; Garlea, V. O.; Aczel, A. A.; Feygenson, M.; Neuefeind, J.; Zhou, H. D.; Nagler, S. E.; MacDougall, G. J.

    2016-01-01

    The ferrimagnetic spinel CoV2O4 has been a topic of intense recent interest, both as a frustrated insulator with unquenched orbital degeneracy and as a near-itinerant magnet which can be driven metallic with moderate applied pressure. Here, we report on our recent neutron diffraction and inelastic scattering measurements on powders with minimal cation site disorder. Our main new result is the identification of a weak (Δ/a a ˜10-4 ), first order structural phase transition at T*=90 K, the same temperature where spin canting was seen in recent single crystal measurements. This transition is characterized by a short-range distortion of oxygen octahedral positions, and inelastic data further establish a weak Δ ˜1.25 meV spin gap at low temperature. Together, these findings provide strong support for the local orbital picture and the existence of an orbital glass state at temperatures below T*.

  13. 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.

  14. Composition and size dependent brittle-to-malleable transitions of Mg-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Jian, E-mail: yinjiandonic@yahoo.com; Ma, Xiujun; Zhou, Zhijian

    2014-05-01

    Mg-based bulk metallic glasses (BMGs) were often treated as brittle materials. However, some Mg-based BMGs were recently reported to show malleability. In order to identify the reasons for the achievement of the brittle-to-malleable transitions in the Mg-based BMGs, we systematically investigated the mechanical properties of four Mg-based BMGs (Mg{sub 65}Cu{sub 25}Gd{sub 10}, Mg{sub 65}Cu{sub 20}Ni{sub 5}Gd{sub 10}, Mg{sub 75}Ni{sub 15}Gd{sub 10}, and Mg{sub 75}Ni{sub 15}Gd{sub 5}Nd{sub 5} BMGs) using the uniaxial compression tests on the samples with sizes of ∅1×2 mm{sup 2} and ∅2×4 mm{sup 2}. The corresponding fracture morphology was observed by scanning electron microscopy (SEM). These Mg-based BMGs displayed the composition or size dependent brittle-to-malleable transitions, accompanied by the fracture mode transition from the cleavage fracture to the shear fracture. It appeared that the Mg-based BMGs were sensitive to cleavage cracks upon loading. The brittle-to-malleable transitions of the Mg-based BMGs were related to not only the stability of shear banding but also the nucleation and propagation of cleavage cracks. It was demonstrated that the suppression of the nucleation and propagation of cleavage cracks could favor the transition from the cleavage fracture to the shear fracture and encourage the brittle-to-malleable transition for the Mg-based BMGs. The underlying mechanism for the brittle-to-malleable transitions of the Mg-based BMGs was discussed with respect to both the composition and size effects.

  15. Determination of the Glass Transition Temperature of Freestanding and Supported Azo-Polymer Thin Films by Thermal Assisted Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Chernykh Elena

    2017-01-01

    Full Text Available In this paper we introduce and apply the method for determination of the glass transition temperature of the sub-100 nm thick freestanding and supported polymer films based on thermally assisted atomic force microscopy (AFM. In proposed approach changes of the phase of an oscillating AFM cantilever are used to determine glass transition temperature. An anomalous decrease of the glass transition temperature for both free-standing and supported azobenzene-functionalized polymer thin films is shown.

  16. Glass transition of adsorbed stereoregular PPMA by inverse gas chromatography at infinite dilution

    Science.gov (United States)

    Hamieh, T.; Rezzaki, M.; Grohens, Y.; Schultz, J.

    1998-10-01

    In this paper, we used inverse gas chromatography (IGC) at infinite dilution that proved to be a powerful technique to determine glass transition and other transitions of PMMA adsorbed on α-alumina. We highlighted the glass transition temperature of the system PMMA/α-Al2O3 with defined polymer tacticity at various covered surface fractions. Thus, the Tg of the adsorbed isotactic PMMA increases strongly as compared to the bulk value. The study of the physical chemical properties of PMMA/α-alumina revealed an important difference in the acidic and basic behaviour, in Lewis terms, of aluminium oxide covered by various concentrations of PMMA. It appears that there is a stabilisation of the physical chemical properties of PMMA/α-Al2O3 for a surface coverage above 50%. This study also highlighted an important effect of the tacticity of the polymer on the acid-base character of the system PMMA/Al2O3. Dans cet article, nous montrons que la chromatographie gazeuse inverse (CGI) à dilution infinie se révèle être une technique très intéressante pour la détermination de la transition vitreuse de polymères stéréoréguliers adsorbés sur des substrats solides tels que l'alumine. Nous avons mis en évidence des transitions attribuées aux phénomènes de relaxation béta, transition vitreuse et autres transitions des systèmes PMMA/Al2O3 de tacticité définie à différents taux de recouvrement. Ainsi, la Tg du PMMA isotactique adsorbé augmente de façon significative par rapport a celle du polymère massique. L'étude des propriétés physico-chimiques du système PMMA/Al2O3, révèle une différence importante dans le comportement acido-basique, au sens de Lewis, de l'alumine pour de taux de recouvrement en PMMA variables. Il apparaît qu'il y a stabilisation des propriétés physico-chimiques de PMMA/Al2O3 pour un taux de recouvrement en PMMA supérieur à 50 %. Cette étude a montré également une influence importante de la tacticité du polymère sur le

  17. Calcium chloride effects on the glass transition of condensed systems of potato starch.

    Science.gov (United States)

    Chuang, Lillian; Panyoyai, Naksit; Katopo, Lita; Shanks, Robert; Kasapis, Stefan

    2016-05-15

    The effect of calcium chloride on the structural properties of condensed potato starch undergoing a thermally induced glass transition has been studied using dynamic mechanical analysis and modulated differential scanning calorimetry. Extensive starch gelatinisation was obtained by hot pressing at 120°C for 7 min producing materials that covered a range of moisture contents from 3.7% w/w (11% relative humidity) to 18.8% w/w (75% relative humidity). FTIR, ESEM and WAXD were also performed in order to elucidate the manner by which salt addition affects the molecular interactions and morphology of condensed starch. Experimental protocol ensured the development of amorphous matrices that exhibited thermally reversible glassy consistency. Both moisture content and addition of calcium chloride affected the mechanical strength and glass transition temperature of polymeric systems. Highly reactive calcium ions form a direct interaction with starch to alter considerably its structural properties via an anti-plasticizing effect, as compared to the polymer-water matrix.

  18. Interparticle interactions mediated superspin glass to superferromagnetic transition in Ni-bacterial cellulose aerogel nanocomposites

    Science.gov (United States)

    Thiruvengadam, V.; Vitta, Satish

    2016-06-01

    The interparticle interactions in the magnetic nanocomposites play a dominant role in controlling phase transitions: superparamagnetic to superspin glass and to superferromagnetic. These interactions can be tuned by controlling the size and number density of nanoparticles. The aerogel composites, 0.3Ni-BC and 0.7Ni-BC, consisting of Ni nanoparticles distributed in the bacterial cellulose have been used as a model system to study these interactions. Contrary to conventional approach, size of Ni-nanoparticles is not controlled and allowed to form naturally in bacterial cellulose template. The uncontrolled growth of Ni results in the formation of nanoparticles with 3 different size distributions - 100 nm particles in voids formed by reticulate structure. At room temperature, the composites exhibit a weakly ferromagnetic behaviour with a coercivity of 40 Oe, which increases to 160 Oe at 10 K. The transition from weakly ferromagnetic state to superferromagnetic state at low temperatures is mediated by the superspin glass state at intermediate temperatures via the interparticle interactions aided by nanoparticles present along the length of fibres. A temperature dependent microstructural model has been developed to understand the magnetic behaviour of nanocomposite aerogels.

  19. RECOVERY OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE) FILM UNIAXIALLY DRAWN JUST BELOW THE GLASS TRANSITION TEMPERATURE

    Institute of Scientific and Technical Information of China (English)

    Nan-jian Sun; Juan Yang; De-yan Shen; Ren-yuan Qian

    2000-01-01

    Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethylene terephthalate) (PET) film sample uniaxially drawn at 69℃ to the draw ratios λ0 = 1.26~2.20 were studied at temperatures around the glass transition temperature (Tg = 73 ℃). Experimental results indicate that the length recovery took place in two distinct steps: a fast first step (fast relaxation) followed by a slow second step (slow relaxation). The relaxation processes were accompanied by the reversion of trans-conformers (1340 cm-1) to gauche, and the dichroic function of the 1340 cm-1 band characterizing the segmental orientation along the chain direction decreased to a very low value at the end of the fast relaxation. This fact led us to assign the fast relaxation as the segmental orientation while the slow relaxation as relaxation of the global chain orientation. It was found that the slow relaxation follows a single exponential function, with relaxation times strongly dependent on the temperature resembling the glass transition process. The fast relaxation does not follow a single exponential decay, presumably a distribution of relaxation times is involved.

  20. On the theoretical determination of the Prigogine-Defay ratio in glass transition

    Science.gov (United States)

    Tropin, Timur V.; Schmelzer, Jürn W. P.; Gutzow, Ivan; Schick, Christoph

    2012-03-01

    In a recent analysis [J. W. P. Schmelzer and I. Gutzow, J. Chem. Phys. 125, 184511 (2006), 10.1063/1.2374894] it was shown for the first time that - in contrast to earlier belief arising from the works of Prigogine and Defay [Chemical Thermodynamics (Longman, London, 1954), Chap. 19; The first French edition of this book was published in 1950] and Davies and Jones [Adv. Phys. 2, 370 (1953), 10.1080/00018735300101252; Davies and Jones Proc. R. Soc. London, Ser. A 217, 26 (1953), 10.1098/rspa.1953.0044] - a satisfactory theoretical interpretation of the experimentally observed values of the so-called Prigogine-Defay ratio Π, being a combination of jumps of thermodynamic coefficients at glass transition, can be given employing only one structural order parameter. According to this analysis, this ratio has to be, in full agreement with experimental findings, larger than one (Π > 1). Its particular value depends both on the thermodynamic properties of the system under consideration and on cooling and heating rates. Based on above-mentioned analysis, latter dependence on cooling rates has been studied in detail in another own preceding paper [T. V. Tropin, J. W. P. Schmelzer, and C. Schick, J. Non-Cryst. Solids 357, 1303 (2011), 10.1016/j.jnoncrysol.2010.12.005]. In the present analysis, an alternative general method of determination of the Prigogine-Defay ratio is outlined, allowing one to determine this ratio having at ones disposal the generalized equation of state of the glass-forming melts under consideration and, in particular, the knowledge of the equilibrium properties of the melts in the glass transformation range. Employing, as an illustration of the method, a particular model for the description of glass-forming melts, theoretical estimates are given for this ratio being, again, in good agreement with experimental data.

  1. Use of a theoretical equation of state to interpret time-dependent free volume in polymer glasses

    Energy Technology Data Exchange (ETDEWEB)

    Curro, J.G.; Lagasse, R.R.; Simha, R.

    1981-10-01

    Many physical properties of polymer glasses change spontaneously during isothermal aging by a process commonly modeled as collapse of free volume. The model has not been verified rigorously because free volume cannot be unambiguously measured. In the present investigation we tentatively identify the free-volume fraction with the fraction of empty sites in the equation of state of Simha and Somcynsky. With this theory, volume recovery measurements can be analyzed to yield directly the time-dependent, free-volume fraction. Using this approach, recent volume measurements on poly(methyl methacrylate) are analyzed. The resulting free-volume fractions are then used in the Doolittle equation to predict the shift in stress relaxation curves at 23 /sup 0/C. These predicted shift factors agree with the experimental measurements of Cizmecioglu et al. In addition, it is shown that previous assumptions concerning temperature dependence of free volume are inconsistent with the theory.

  2. Use of a theoretical equation of state to interpret time-dependent free volume in polymer glasses

    Science.gov (United States)

    Curro, J. G.; Lagasse, R. R.; Simha, R.

    1981-10-01

    Many physical properties of polymer glasses change spontaneously during isothermal aging by a process commonly modeled as collapse of free volume. The model has not been verified rigorously because free volume cannot be unambiguously measured. In the present investigation we tentatively identify the free-volume fraction with the fraction of empty sites in the equation of state of Simha and Somcynsky. With this theory, volume recovery measurements can be analyzed to yield directly the time-dependent, free-volume fraction. Using this approach, recent volume measurements on poly(methyl methacrylate) are analyzed. The resulting free-volume fractions are then used in the Doolittle equation to predict the shift in stress relaxation curves at 23 °C. These predicted shift factors agree with the experimental measurements of Cizmecioglu et al. In addition, it is shown that previous assumptions concerning temperature dependence of free volume are inconsistent with the theory.

  3. Free-Volume Nanostructurization in Ga-Modified As2Se3 Glass.

    Science.gov (United States)

    Shpotyuk, Ya; Ingram, A; Shpotyuk, O; Dziedzic, A; Boussard-Pledel, C; Bureau, B

    2016-12-01

    Different stages of intrinsic nanostructurization related to evolution of free-volume voids, including phase separation, crystalline nuclei precipitation, and growth, were studied in glassy As2Se3 doped with Ga up to 5 at. %, using complementary techniques of positron annihilation lifetime spectroscopy, X-ray powder diffraction, and scanning electron microscopy with energy-dispersive X-ray analysis. Positron lifetime spectra reconstructed in terms of a two-state trapping model testified in favor of a native void structure of g-As2Se3 modified by Ga additions. Under small Ga content (below 3 at. %), the positron trapping in glassy alloys was dominated by voids associated with bond-free solid angles of bridging As2Se4/2 units. This void agglomeration trend was changed on fragmentation with further Ga doping due to crystalline Ga2Se3 nuclei precipitation and growth, these changes being activated by employing free volume from just attached As-rich glassy matrix with higher content of As2Se4/2 clusters. Respectively, the positron trapping on free-volume voids related to pyramidal AsSe3/2 units (like in parent As2Se3 glass) was in obvious preference in such glassy crystalline alloys.

  4. Modeling the Effect of Glass Microballoon (GMB) Volume Fraction on Behavior of Sylgard/GMB Composites.

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Judith Alice [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Long, Kevin Nicholas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-05-01

    This work was done to support customer questions about whether a Sylgard/Glass Microballoon (GMB) potting material in current use could be replaced with pure Sylgard and if this would significantly change stresses imparted to internal components under thermal cycling conditions. To address these questions, we provide micromechanics analysis of Sylgard/GMB materials using both analytic composite theory and finite element simulations to better understand the role of the GMB volume fraction in determining thermal expansion coefficient, elastic constants, and behavior in both confined and unconfined compression boundary value problems. A key finding is that damage accumulation in the material from breakage of GMBs significantly limits the global stress magnitude and results in a plateau stress behavior over large ranges of compressive strain. The magnitude of this plateau stress is reduced with higher volume fractions of GMBs. This effect is particularly pronounced in confined compression, which we estimate bears the most similarity to the application of interest. This stress-limiting damage mechanism is not present in pure Sylgard, however, and the result is much higher stresses under confined compression. Thus, we recommend that some volume fraction greater than 10% GMBs be used for confined deformation applications.

  5. Studying the Effect of Volume Fraction of Glass Fiberson the Thermal Conductivity of the Polymer Composite Materials

    Directory of Open Access Journals (Sweden)

    Mohammed Sellab Hamza

    2008-01-01

    Full Text Available In this study the effect of fiber volume fraction of the glass fiber on the thermal conductivity of the polymer composite material was studied. Different fiber volume fraction of glass fibers were used (3%, 6%, 9%, 12%, and 15%. Specimens were made from polyester which reinforced with glass fibers .The fibers had two arrangements according to the direction of the thermal flow. In the first arrangement the fibers were parallel to the direction of the thermal flow, while the second arrangement was perpendicular; Lee's disk method was used for testing the specimens. The experimental results proved that the values of the thermal conductivity of the specimens was higher when the fibers arranged in parallel direction than that when the fibers arranged in the perpendicular direction. The percentage of increasing of experimental thermal conductivity was 96.91% for parallel arrangement and 13.33% for perpendicular arrangement comparison with its original value before the using of glass fibers. Also the experimental results indicated that the thermal conductivity increases with the increasing of the fiber volume fraction. Minimum value was (0.172 W/m.C for perpendicular arrangement at fiber volume fraction 3% and maximum value was (0.327 W/m.C for parallel arrangement at fiber volume fraction 15%.

  6. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water.

    Science.gov (United States)

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-10-27

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, T(g) . Here we report a universal water-content, X(aqu) , dependence of T(g) for aqueous solutions. Solutions with X(aqu)>X(cr)(aqu)vitrify/devitrify at a constant temperature, ~T(g) , referring to freeze-concentrated phase with X(aqu)left behind ice crystallization. Those solutions with X(aqu)recrystallization is stabilized at . Experiments on aqueous glycerol and 1,2,4-butanetriol solutions in literature were repeated, and the same samples subject to other annealing treatments equally reproduce the result. The upshift of T(g) by annealing is attributable to freeze-concentrated phase of solutions instead of 'liquid II phase of water'. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution.

  7. Pressure Induced Liquid-to-Liquid Transition in Zr-based Supercooled Melts and Pressure Quenched Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Dmowski, W.; Gierlotka, S.; Wang, Z.; Yokoyama, Y.; Palosz, B.; Egami, T.

    2017-07-26

    Through high-energy x-ray diffraction and atomic pair density function analysis we find that Zr-based metallic alloy, heated to the supercooled liquid state under hydrostatic pressure and then quenched to room temperature, exhibits a distinct glassy structure. The PDF indicates that the Zr-Zr distances in this glass are significantly reduced compared to those quenched without pressure. Annealing at the glass transition temperature at ambient pressure reverses structural changes and the initial glassy state is recovered. This result suggests that pressure causes a liquid-to-liquid phase transition in this metallic alloy supercooled melt. Such a pressure induced transition is known for covalent liquids, but has not been observed for metallic liquids. The High Pressure Quenched glasses are stable in ambient conditions after decompression.

  8. 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

    -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...... enthalpy and the Al–Y (or Cu–Y) mixing enthalpy. The findings contribute to distinguishing between phase separation and clusters motion scenarios....

  9. Instability Analysis and Free Volume Simulations of Shear Band Directions and Arrangements in Notched Metallic Glasses

    Science.gov (United States)

    Li, Weidong; Gao, Yanfei; Bei, Hongbin

    2016-01-01

    As a commonly used method to enhance the ductility in bulk metallic glasses (BMGs), the introduction of geometric constraints blocks and confines the propagation of the shear bands, reduces the degree of plastic strain on each shear band so that the catastrophic failure is prevented or delayed, and promotes the formation of multiple shear bands. The clustering of multiple shear bands near notches is often interpreted as the reason for improved ductility. Experimental works on the shear band arrangements in notched metallic glasses have been extensively carried out, but a systematic theoretical study is lacking. Using instability theory that predicts the onset of strain localization and the free-volume-based finite element simulations that predict the evolution of shear bands, this work reveals various categories of shear band arrangements in double edge notched BMGs with respect to the mode mixity of the applied stress fields. A mechanistic explanation is thus provided to a number of related experiments and especially the correlation between various types of shear bands and the stress state. PMID:27721462

  10. Instability Analysis and Free Volume Simulations of Shear Band Directions and Arrangements in Notched Metallic Glasses

    Science.gov (United States)

    Li, Weidong; Gao, Yanfei; Bei, Hongbin

    2016-10-01

    As a commonly used method to enhance the ductility in bulk metallic glasses (BMGs), the introduction of geometric constraints blocks and confines the propagation of the shear bands, reduces the degree of plastic strain on each shear band so that the catastrophic failure is prevented or delayed, and promotes the formation of multiple shear bands. The clustering of multiple shear bands near notches is often interpreted as the reason for improved ductility. Experimental works on the shear band arrangements in notched metallic glasses have been extensively carried out, but a systematic theoretical study is lacking. Using instability theory that predicts the onset of strain localization and the free-volume-based finite element simulations that predict the evolution of shear bands, this work reveals various categories of shear band arrangements in double edge notched BMGs with respect to the mode mixity of the applied stress fields. A mechanistic explanation is thus provided to a number of related experiments and especially the correlation between various types of shear bands and the stress state.

  11. Influence of pulsing current on the glass transition and crystallizing kinetics of a Zr base bulk amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wenfei; YAO Kefu; ZHAO Zhankui

    2004-01-01

    Based on the thermal analysis, the influence of pulsing current on the glass transition and crystallizing kinetics of Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy has been studied. The obtained results show that after the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy was pretreated by high-density pulsing current at low temperature, its glass transition temperature Tg, the initial crystallizing temperature Tx and the corresponding exothermic peak of crystallization Tpi were reduced. But the temperature range of supercooled liquid ΔT=Tx-Tg is almost the same. The calculated results with Kissinger equation show that the activation energy of glass transition of the alloy pretreated is reduced significantly, while the activation energy of crystallization is basically unchanged. The influence of pulsing current on the glass transition and crystallization of the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy is believed to be related with the structure relaxation of the glass caused by the current.

  12. Deconfinement phase transition in a finite volume in the presence of massive particles

    Energy Technology Data Exchange (ETDEWEB)

    Ait El Djoudi, A.; Ghenam, L. [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Superieure - Kouba, B.P. 92, 16050, Vieux Kouba, Algiers (Algeria)

    2012-06-27

    We study the QCD deconfinement phase transition from a hadronic gas to a Quark-Gluon Plasma, in the presence of massive particles. Especially, the influence of some parameters as the finite volume, finite mass, flavors number N{sub f} on the transition point and on the order of the transition is investigated.

  13. Kinetics of the Glass Transition of the Zr41Ti14Cu12.5Ni1oBe22.5 Alloy Solidified in a Drop Tube

    Institute of Scientific and Technical Information of China (English)

    李工; 孙力玲; 刘日平; 景勤; 张君; 李强; 王文魁

    2002-01-01

    Droplets of Zr41 Ti14Cu12.5Ni10Be22.5 glass-forming alloy with different sizes are solidified in a drop tube containerless process. The glass transition temperature Tg of Zr41 Ti14 Cu12.5Ni10Be22.5 glassy spheres solidified with different cooling rates is investigated by using a differential scanning calorimeter. It was found that all the amorphous spheres show an increase of Tg with the heating rate. The glassy spheres have a unique value for the glass transition activation energy E9 = 435.50 k J/mol, which is independent of cooling rate q. The insensitivity of Tg to q is interpreted by an extension of the free volume model for flow.

  14. 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

  15. Influence of the critical Fe atomic volume on the magnetism of Fe-rich metallic glasses evidenced by pressure-dependent measurements

    Science.gov (United States)

    Kiss, L. F.; Kemény, T.; Bednarčík, J.; Gamcová, J.; Liermann, H.-P.

    2016-06-01

    Despite the intensive studies for decades, it is still not well understood how qualitatively different magnetic behaviors can occur in a narrow composition range for the Fe-rich Fe-transition metal (TM) amorphous alloys. In this study of amorphous F e100 -xZ rx (x =7 , 9, 12) metallic glasses, normal ferromagnetism (FM) is found at 12 % Zr where only the FM-paramagnetic (PM) transition is observed at the Curie temperature, TC. In contrast, spin-glass (SG)-PM transition at a temperature, Tg, called SG temperature, is only observed at 7 % Zr, while in the transient re-entrant composition range (x =8 -11 ) , an SG-FM transition at a temperature, Tf, called spin-freezing temperature, is also observed at low temperature besides the normal FM-PM transition at TC. In order to understand this unusual behavior, a detailed characterization of pressure (atomic volume), composition, and temperature dependence of the magnetic properties is coupled with high pressure synchrotron x-ray diffraction determination of the pressure dependence of the atomic volume. The results on F e100 -xZ rx (x =7 , 9, 12) are compared to those obtained for the FM C o91Z r9 metallic glass not showing any kind of anomalous magnetic properties. It is confirmed that the unusual behavior is caused by a granularlike magnetic structure where weakly coupled magnetic clusters are embedded into a FM bulk matrix. Since the mechanism of the magnetization reversal was found to be of the curling type rather than homogeneous rotation, the energy barrier determining the blocking temperature of the clusters is calculated as AR, where A is the exchange constant and R is the cluster size, in contrast to the usual characterization of the energy barrier by KV where K is the anisotropy energy and V is the cluster volume. The volume fraction of the FM part is a fast changing function of the bulk composition: Almost 100% FM fraction is found at 12 % of Zr while no trace of real FM is observed at 7 at % Zr. The driving

  16. Yielding of glass under shear: A directed percolation transition precedes shear-band formation

    Science.gov (United States)

    Shrivastav, Gaurav Prakash; Chaudhuri, Pinaki; Horbach, Jürgen

    2016-10-01

    Under external mechanical loading, glassy materials, ranging from soft matter systems to metallic alloys, often respond via formation of inhomogeneous flow patterns, during yielding. These inhomogeneities can be precursors to catastrophic failure, implying that a better understanding of their underlying mechanisms could lead to the design of smarter materials. Here, extensive molecular dynamics simulations are used to reveal the emergence of heterogeneous dynamics in a binary Lennard-Jones glass, subjected to a constant strain rate. At a critical strain, this system exhibits for all considered strain rates a transition towards the formation of a percolating cluster of mobile regions. We give evidence that this transition belongs to the universality class of directed percolation. Only at low shear rates, the percolating cluster subsequently evolves into a transient (but long-lived) shear band with a diffusive growth of its width. Finally, the steady state with a homogeneous flow pattern is reached. In the steady state, percolation transitions also do occur constantly, albeit over smaller strain intervals, to maintain the stationary plastic flow in the system.

  17. Thermodynamic behaviour of gliadins mixture and the glass-softening transition of its dried state.

    Science.gov (United States)

    Ferrari, C; Johari, G P

    1997-10-01

    The glass-softening transition of a mixture of gliadins extracted from wheat flour has been studied in its dry state by differential scanning calorimetry (DSC). Further, the rate of removal of its water vapours on its evaporation from a gliadins mixture containing different amounts of water has been investigated, and through this the presence of any exothermic effect that could be attributed to polymerization of gliadins has been examined. The heat absorbed in this evaporation is comparable with the heat of evaporation of pure water measured in a separate experiment in identical conditions. This showed that the gliadins mixture did not polymerize on heating up to 473 K in the presence of moisture. In this respect the behaviour of the gliadins mixture differs remarkably from that of gluten studied before (J Phys Chem 1996:100:19692). The effects of purge gas, helium and argon, on the calorimetric effects during the evaporation of water have been studied. A restudy of gluten shows that helium decreases substantially the endothermic signal in the DSC measurements, and thereby reveals the exothermic effects of polymerization in gluten, but argon does not do so. The structural relaxation time, t, of dry gliadins mixtures at different temperatures has been calculated from an analysis of its glass-softening endotherm. The temperature at which t = 1 ks is 452 K, and the Tg, obtained by the usual method of intersection of the straight lines drawn, is 443 K, 7 K higher than for the polymerized dry gluten, the distribution of relaxation time parameter is 0.25, and increase in the heat capacity in this range is 0.21 J/g K. Physical ageing effects are considerable in the gliadins mixture, which alters the glass-softening endotherm but not the structural relaxation time or its distribution.

  18. A direct test of the correlation between elastic parameters and fragility of ten glass formers and their relationship to elastic models of the glass transition

    Science.gov (United States)

    Torchinsky, Darius H.; Johnson, Jeremy A.; Nelson, Keith A.

    2009-02-01

    We present an impulsive stimulated scattering test of the "shoving model" of the glass transition and of the correlation between the fragility index and the ratio of instantaneous elastic moduli of eight supercooled liquids. Samples of triphenyl phosphite, DC704 (tetramethyl tetraphenyl trisiloxane), m-fluoroaniline, Ca(NO3)2ṡ4H2O, diethyl phthalate, propylene carbonate, m-toluidine, phenyl salicylate (salol), 2-benzylphenol, and Santovac 5 (5-phenyl 4-ether), were cooled to their respective glass transition temperatures and the elastic moduli directly measured at the highest accessible shear frequencies. The shear modulus was then measured every 2 K as deeply as permitted into the liquid state for all liquids except propylene carbonate. Our results, in conjunction with dynamical relaxation data for these liquids obtained from the literature, lend credence to the notion that the dynamics of the glass transition are governed by the evolution of the shear modulus but do not suggest a strong correlation between the fragility index and the ratio of the elastic moduli.

  19. Retrogradation of Waxy Rice Starch Gel in the Vicinity of the Glass Transition Temperature

    Science.gov (United States)

    Charoenrein, Sanguansri; Udomrati, Sunsanee

    2013-01-01

    The retrogradation rate of waxy rice starch gel was investigated during storage at temperatures in the vicinity of the glass transition temperature of a maximally concentrated system (Tg′), as it was hypothesized that such temperatures might cause different effects on retrogradation. The Tg′ value of fully gelatinized waxy rice starch gel with 50% water content and the enthalpy of melting retrograded amylopectin in the gels were investigated using differential scanning calorimetry. Starch gels were frozen to −30°C and stored at 4, 0, −3, −5, and −8°C for 5 days. The results indicated that the Tg′ value of gelatinized starch gel annealed at −7°C for 15 min was −3.5°C. Waxy rice starch gels retrograded significantly when stored at 4°C with a decrease in the enthalpy of melting retrograded starch in samples stored for 5 days at −3, −5, and −8°C, respectively, perhaps due to the more rigid glass matrix and less molecular mobility facilitating starch chain recrystallization at temperatures below Tg′. This suggests that retardation of retrogradation of waxy rice starch gel can be achieved at temperature below Tg′. PMID:26904602

  20. Retrogradation of Waxy Rice Starch Gel in the Vicinity of the Glass Transition Temperature

    Directory of Open Access Journals (Sweden)

    Sanguansri Charoenrein

    2013-01-01

    Full Text Available The retrogradation rate of waxy rice starch gel was investigated during storage at temperatures in the vicinity of the glass transition temperature of a maximally concentrated system (, as it was hypothesized that such temperatures might cause different effects on retrogradation. The value of fully gelatinized waxy rice starch gel with 50% water content and the enthalpy of melting retrograded amylopectin in the gels were investigated using differential scanning calorimetry. Starch gels were frozen to −30°C and stored at 4, 0, −3, −5, and −8°C for 5 days. The results indicated that the value of gelatinized starch gel annealed at −7°C for 15 min was −3.5°C. Waxy rice starch gels retrograded significantly when stored at 4°C with a decrease in the enthalpy of melting retrograded starch in samples stored for 5 days at −3, −5, and −8°C, respectively, perhaps due to the more rigid glass matrix and less molecular mobility facilitating starch chain recrystallization at temperatures below . This suggests that retardation of retrogradation of waxy rice starch gel can be achieved at temperature below .

  1. Retrogradation of Waxy Rice Starch Gel in the Vicinity of the Glass Transition Temperature.

    Science.gov (United States)

    Charoenrein, Sanguansri; Udomrati, Sunsanee

    2013-01-01

    The retrogradation rate of waxy rice starch gel was investigated during storage at temperatures in the vicinity of the glass transition temperature of a maximally concentrated system (T g '), as it was hypothesized that such temperatures might cause different effects on retrogradation. The T g ' value of fully gelatinized waxy rice starch gel with 50% water content and the enthalpy of melting retrograded amylopectin in the gels were investigated using differential scanning calorimetry. Starch gels were frozen to -30°C and stored at 4, 0, -3, -5, and -8°C for 5 days. The results indicated that the T g ' value of gelatinized starch gel annealed at -7°C for 15 min was -3.5°C. Waxy rice starch gels retrograded significantly when stored at 4°C with a decrease in the enthalpy of melting retrograded starch in samples stored for 5 days at -3, -5, and -8°C, respectively, perhaps due to the more rigid glass matrix and less molecular mobility facilitating starch chain recrystallization at temperatures below T g '. This suggests that retardation of retrogradation of waxy rice starch gel can be achieved at temperature below T g '.

  2. Critical test of the mode-coupling theory of the glass transition.

    Science.gov (United States)

    Berthier, Ludovic; Tarjus, Gilles

    2010-09-01

    In its common implementation, the mode-coupling theory of the glass transition predicts the time evolution of the intermediate scattering functions in viscous liquids on the sole basis of the structural information encoded in two-point density correlations. We provide a critical test of this property and show that the theory fails to describe the strong differences of dynamical behavior seen in two model liquids characterized by very similar pair-correlation functions. Because we use "exact" static information provided by numerical simulations, our results are a direct indication that some important information about the dynamics of viscous liquids is not captured by pair correlations and is thus not described by the mode-coupling theory, even in the temperature regime where the theory is usually applied.

  3. Possible crossover to percolation scenario near superfluid-Bose-glass transition

    Science.gov (United States)

    Syromyatnikov, A. V.; Sizanov, A. V.

    2017-10-01

    We discuss magnetically ordered (;superfluid;) phase near quantum transition to Bose-glass phase in a simple modeling system, Heisenberg antiferromagnet in spatial dimension d > 2 in external magnetic field with disorder in exchange coupling constants. Our analytical consideration is based on hydrodynamic description of long-wavelength excitations and it is valid in the entire critical region near the quantum critical point (QCP). We demonstrate that the system behaves in full agreement with predictions by Fisher et al. (Phys. Rev. B 40, 546 (1989)) in close vicinity of QCP. On the other hand, we show that many recent experimental and numerical results obtained in various 3D systems can be described by our formulas using percolation critical exponents. Then, it is a possibility that a percolation critical regime arises in the ordered phase in some 3D systems not very close to QCP.

  4. Glass and Jamming Transitions: From Exact Results to Finite-Dimensional Descriptions

    Science.gov (United States)

    Charbonneau, Patrick; Kurchan, Jorge; Parisi, Giorgio; Urbani, Pierfrancesco; Zamponi, Francesco

    2017-03-01

    Despite decades of work, gaining a first-principles understanding of amorphous materials remains an extremely challenging problem. However, recent theoretical breakthroughs have led to the formulation of an exact solution of a microscopic glass-forming model in the mean-field limit of infinite spatial dimension. Numerical simulations have remarkably confirmed the dimensional robustness of some of the predictions. This review describes these latest advances. More specifically, we consider the dynamical and thermodynamic descriptions of hard spheres around the dynamical, Gardner, and jamming transitions. Comparing mean-field predictions with the finite-dimensional simulations, we identify robust aspects of the theory and uncover its more sensitive features. We conclude with a brief overview of ongoing research.

  5. Glass-to-Rubber Transition of Polymer Thin Films and Their Surface Dynamical Properties

    Institute of Scientific and Technical Information of China (English)

    X.P.Wang; H.F.Zhang; Xudong Xiao; Ophelia K.C.Tsui

    2000-01-01

    @@ Glass-to-rubber transition temperature, Tg' of polystyrene(PS) (Mw=500K, Mw/Mn=1.03)thin films (thickness, d= 100 to 2000 A) deposited on Si with native oxide was determined by variable angle spectroscopic ellipsometry(VASE. We observed that the Tg of the polymer films decreased monotonically as the film thickness was decreased. It had previously been proposed that this was due to a highly mobile surface rubbery layer that existed even well below Tg' We used atomic force microscopic(AFM)adhesion measurement as a direct probe to investigate the surface dynamical properties of the PS samples and a thin film ofpoly(tert-butyl acrylate) (PtBA) (Mw= 148K, Mw/Mn=17, and Tg bullk=50℃). By comparing the AFM results and those obtained from shear modulus measurements of a bulk sample, we found no enhancement in the molecular relaxation at the free surface of these samples.

  6. Glass transition temperature of PIB, PDMS and PMMA from small-time simulations

    Science.gov (United States)

    Duki, Solomon; Tsige, Mesfin; Taylor, Philip

    2009-03-01

    We have applied some new techniques to obtain predictions of the glass transition temperatures Tg of poly(isobutylene), poly(dimethyl-siloxane), and poly(methyl methacrylate) from small-time atomistic molecular dynamics simulations. The different fragilities of these materials are reflected in the results of the simulations. One approach involved measurement of the apparent softening of the ``cage'' in which a monomer is bound, while another involved studying autocorrelation of a convolution of the velocity with a smoothing function in order to detect the frequency of escapes from the ``cage.'' To check the accuracy of the short-time methods, the Tg of the polymers was also found using conventional diffusion simulations in which the rate of increase of the root mean squared displacement of an atom, monomer, or molecule is measured at very long times. The economical short-time simulations yielded results for Tg that were identical to those of the computer-intensive long-time simulations.

  7. Reduced glass transition temperatures in thin polymer films: surface effect or artifact?

    Science.gov (United States)

    Bäumchen, O; McGraw, J D; Forrest, J A; Dalnoki-Veress, K

    2012-08-03

    We have examined the direct effect of manipulating the number of free surfaces on the measured glass transition temperature T(g) of thin polystyrene films. Thin films in the range 35 nm thickness and refractive index of freestanding films. By noting the change in slope in each of these quantities, a T(g) value can be assigned in quantitative agreement with previously reported results. For thin freestanding films this value is reduced from that of the bulk. The exact same films are then transferred to a Si substrate and the T(g) of the resulting supported film was determined. The T(g) values of the now supported films are the same as the bulk value and the same as previous reports of similar supported films. These experiments unambiguously show that free interfaces are the dominant cause of the T(g) reductions for the film thicknesses studied.

  8. The glass transition temperature and microstructure of polyurethane/epoxy resin interpenetrating polymer networks nanocomposites

    Institute of Scientific and Technical Information of China (English)

    JIA Qingming; ZHENG Maosheng; SHEN Renjie; CHEN Hongxiang

    2006-01-01

    Nanocomposites with various contents of organophilic montmorillonite (oMMT) have been prepared by adding oMMT to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymeric technique. DSC experiment indicates a novel phenomenon that the glass transition temperature (Tg) of the nanocomposites increases with the oMMT content up to 3 %, then decreases with further increasing oMMT content. In order to explain this phenomenon, crosslink density, hydrogen bonding in the hard segments, crystallization of the nanocomposites and the exfoliation degree of oMMT in the nanocomposites have been investigated by swelling method, FT-IR, XRD, SEM and TEM, respectively. The results indicate that the crosslink density and the hydrogen bonding index of the nanocomposites increase, but the crystallization degree of the nanocomposites decreases with increasing oMMT content. In addition, oMMT improves the network structure of PU/EP.

  9. Relation Between Glass Transition Temperatures in Polymer Nanocomposites and Polymer Thin Films

    Science.gov (United States)

    Kropka, Jamie; Pryamitsyn, Victor; Ganesan, Venkat

    2009-03-01

    Motivated by recent experiments, we examine within a percolation model whether there is a quantitative equivalence in the glass transition temperatures of polymer thin films and polymer nanocomposites (PNCs). Our results indicate that while the qualitative behaviors of these systems are similar, a quantitative equivalence cannot be established in general. However, we propose a phenomenological scaling collapse of our results which suggests a simple framework by which the results of the thin films may be used to quantitatively predict the properties of PNCs. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  10. High-dimensional surprises neat the glass and the jamming transitions

    Science.gov (United States)

    Charbonneau, Patrick

    2013-03-01

    The glass problem is notoriously hard and controversial. Even at the mean-field level, there is little agreement about how a fluid turns 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, and explore its consequences. Non-Gaussian caging, for instance, persists all the way to the jamming limit of infinitely compressed hard spheres, which affects mechanical stability. We thus obtain new scaling relations, and establish clear mileposts for the emergence of a mean-field theory of jamming.

  11. Deformation of Thin Free-standing Films with Sessile Droplets Through the Glass Transition

    Science.gov (United States)

    Fortais, Adam; Schulman, Rafael; Dalnoki-Veress, Kari

    Droplets on a rigid substrate will form a contact angle determined by interfacial tensions according to Young's law. Likewise, the Laplace pressure of a droplet will deform a liquid substrate, and the contact line geometry can be determined through a Neumann construction. We explore the intermediate case of micro-droplets placed on thin, highly compliant, free-standing films. The Laplace pressure of the droplet deforms the free-standing film, creating a spherical bulge. The film's tension is modulated by changing temperature continuously from well below the glass transition into the melt state of the film. The contact angle of the liquid droplet with the undeformed film as well as the angle of the bulge with the film is measured and compared to the contact angles predicted by a force balance at the contact line.

  12. Glass transition of polystyrene (PS) studied by Raman spectroscopic investigation of its phenyl functional groups

    Science.gov (United States)

    Bertoldo Menezes, D.; Reyer, A.; Marletta, A.; Musso, M.

    2017-01-01

    In polymeric materials the glass transition (GT) is a well-known and very important relaxation process related to movements of functional groups in the polymeric chain. In this work, we show the potential of Raman spectroscopy for exploring the GT process in the polymer polystyrene. We collected Raman spectra during a step-by-step heating process of the sample, which allowed us to collect signatures of the GT process from peak parameters of specific vibrational modes, and to verify the GT temperature. Results of the latter were in accordance with published values obtained via other methods. We identified the aromatic ring vibrational modes of the phenyl functional groups to be those which, due to steric hindrance, suffer the largest influence during the GT process. This confirms that Raman spectroscopy can be used as a complementary technique to perform GT investigations in polymeric materials due to its sensitivity to small intermolecular changes affecting vibrational properties of relevant functional side groups.

  13. Effect of atmosphere on reductions in the glass transition of thin polystyrene films

    Science.gov (United States)

    Raegen, A. N.; Massa, M. V.; Forrest, J. A.; Dalnoki-Veress, K.

    2008-12-01

    We have used nulling ellipsometry to measure the glass transition temperature, T g , of thin films of polystyrene in ambient, dry nitrogen, and vacuum environments. For all environments, the measured T g values decrease with decreasing film thickness in a way that is quantitatively similar to previously reported studies in ambient conditions. These results provide strong reinforcement of previous conclusions that such reduced T g values are an intrinsic property of the confined material. Furthermore, the results are in contrast to recent reports which suggest that the T g reductions measured by many researchers are the results of artifacts (i.e. degradation of the polymer due to annealing in ambient conditions, or moisture content).

  14. Coupled effects of substrate adhesion and intermolecular forces on polymer thin film glass-transition behavior.

    Science.gov (United States)

    Xia, Wenjie; Keten, Sinan

    2013-10-15

    Intermolecular noncovalent forces between polymer chains influence the mobility and glass-transition temperature (Tg), where weaker interchain interactions, all else being the same, typically results in lower bulk polymer Tg. Using molecular dynamics simulations, here we show that this relation can become invalid for supported ultrathin films when the substrate-polymer interaction is extremely strong and the polymer-polymer interactions are much weaker. This contrasting trend is found to be due to a more pronounced substrate-induced appreciation of the film Tg for polymers with weaker intermolecular interactions and low bulk Tg. We show that optimizing this coupling between substrate adhesion and bulk Tg maximizes thin film Tg, paving the way for tuning film properties through interface nanoengineering.

  15. Enhancement in the Glass Transition Temperature in Latent Thiol-Epoxy Click Cured Thermosets

    Directory of Open Access Journals (Sweden)

    Dailyn Guzmán

    2015-04-01

    Full Text Available Tri and tetrafunctional thiol were used as curing agent for diglycidyl ether of bisphenol A (DGEBA catalyzed by a commercially available amine precursor, LC-80. Triglycidyl isocianurate (TGIC was added in different proportions to the mixture to increase rigidity and glass transition temperature (Tg. The cooperative effect of increasing functionality of thiol and the presence of TGIC in the formulation leads to an increased Tg without affecting thermal stability. The kinetics of the curing of mixtures was studied by calorimetry under isothermal and non-isothermal conditions. The latent characteristics of the formulations containing amine precursors were investigated by rheometry and calorimetry. The increase in the functionality of the thiol produces a slight decrease in the storage lifetime of the mixture. The materials obtained with tetrathiol as curing agent showed the highest values of Young’s modulus and Tg.

  16. The glass transition and enthalpy recovery of a single polystyrene ultrathin film using Flash DSC

    Science.gov (United States)

    Koh, Yung P.; Simon, Sindee L.

    2017-05-01

    The kinetics of the glass transition are measured for a single polystyrene ultrathin film of 20 nm thickness using Flash differential scanning calorimetry (DSC). Tg is measured over a range of cooling rates from 0.1 to 1000 K/s and is depressed compared to the bulk. The depression decreases with increasing cooling rate, from 12 K lower than the bulk at 0.1 K/s to no significant change at 1000 K/s. Isothermal enthalpy recovery measurements are performed from 50 to 115 °C, and from these experiments, the temperature dependence of the induction time along the glass line is obtained, as well as the temperature dependence of the time scale required to reach equilibrium, providing a measure of the shortest effective glassy relaxation time and the longest effective equilibrium relaxation time, respectively. The induction time for the ultrathin film is found to be similar to the bulk at all temperatures presumably because the Tg values are the same due to the use of a cooling rate of 1000 K/s prior to the enthalpy recovery measurements. On the other hand, the times required to reach equilibrium for the ultrathin film and bulk are similar at 100 °C, and considerably shorter for the ultrathin film at 90 °C, consistent with faster dynamics under nanoconfinement at low temperatures. The magnitude of the "Tg depression" is smaller when using the equilibrium relaxation time from the structural recovery experiment as a measure of the dynamics than when measuring Tg after a cooling experiment. A relaxation map is developed to summarize the results.

  17. Dielectric properties of NaF–B2O3 glasses doped with certain transition metal ions

    Indian Academy of Sciences (India)

    M Krishna Murthy; K S N Murthy; N Veeraiah

    2000-08-01

    Dielectric constant , loss tan , a.c. conductivity and dielectric breakdown strength of NaF–B2O3 glasses doped with certain transition metal ions (viz. Cu2+, VO2+, Ti4+ and Mn4+) are studied in the frequency range 102–107 Hz and in the temperature range 30–250°C. The values of , tan , a.c. are found to be the highest for Cu2+ doped glasses and the lowest for Mn4+ doped glasses. Activation energy for a.c. conduction and the value of dielectric breakdown strength are found to be the lowest for Cu2+ doped glasses and the highest for Mn4+ doped glasses. With the help of infrared spectra, increase in the values of and tan of these glasses with frequency and temperature are identified with space charge polarization. An attempt has been made to explain a.c. conduction phenomenon on the basis of quantum mechanical tunneling model (QMT)/carrier barrier hopping model.

  18. Non-ideal axicon-generated Bessel beam application for intra-volume glass modification.

    Science.gov (United States)

    Dudutis, Juozas; GeČys, Paulius; RaČiukaitis, Gediminas

    2016-12-12

    The extended focal depth of Bessel beams is a very attracting property for glass cutting applications. However, Bessel beam generation with a non-ideal conical lens induces beam pattern distortions. We present our novel results on bulk modifications of soda-lime glass using a non-ideal axicon-generated Bessel beam. Modelling of the Bessel beam pattern and experimental measurements indicated ellipticity of the central core diameter. That resulted in the formation of cracks in a transverse direction inside the bulk of glass. Furthermore, we demonstrate the possibility to control the transverse crack propagation direction, which is crucial in the case of glass cutting applications.

  19. Effects of molecular characteristics of on konjac glucomannan glass transitions of potato amylose, amylopection and their mixtures.

    Science.gov (United States)

    Guo, Li; Liang, Qin; Du, Xianfeng

    2011-03-15

    The purpose of this study was to explore further the functions of konjac glucomannan (KGM) in starch-based foods. Experiments were carried out using the mixed amylose/amylopectin/KGM system as a model. High-speed differential scanning calorimetry (hyper-DSC) with the support of high-performance size exclusion chromatography (HPSEC) equipped with multi-angle laser light scattering (MALLS) and differential refractive index (RI), X-ray diffractometry (XRD) and viscosimetry was used to investigate the effects of KGM on glass transition temperatures (T(g) s) of mixtures with different amylose/amylopectin ratios. Hyper-DSC results showed that the T(g) s of amylose, amylopection and their mixtures decreased with increasing concentration of KGM. Based on the molecular characteristics of KGM, HPSEC-MALLS-RI, viscosimetry and XRD results showed that the molar masses of KGM ranged from 1.023 × 10(6) to 1.329 × 10(6) g mol(-1) ; the root mean square (RMS) radii were distributed from 110.5 to 129.6 nm, and M(w) /M(n) was 1.017. KGM was a linear molecule with random-coil conformation in solution and the crystallinity was 0.00%. It is suggested that the addition of KGM has plasticizing effects on the structures of amylose and amylopectin, which can increase free volume and molecular movement of amylose and amylopectin chains, resulting in a decrease in their T(g) s. Copyright © 2010 Society of Chemical Industry.

  20. 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.

  1. Glass transition dynamics and charge carrier mobility in conjugated polyfluorene thin films

    Science.gov (United States)

    Qin, Hui; Liu, Dan; Wang, Tao

    Conjugated polymers are commonly used in organic optoelectronic devices, e.g. organic photovoltaics (OPVs), light-emitting diodes (LEDs) and field effect transistors (FETs). In these devices, the conjugated polymers are prepared as thin films with thicknesses in the range of tens to hundreds of nanometers, and are interfaced with different function layers made from organic or inorganic materials. We have studied the glass transition temperature (Tg) of poly(9, 9-dioctylfluorene)-co-N-(1, 4-butylphenyl)diphenylamine) (TFB) thin films supported on different substrates, as well as their SCLC charge carrier mobility in photodiodes. Both Monotonic and non-monotonic Tg deviations are observed in TFB thin films supported on Si/SiOx and PEDOT:PSS, respectively. With low to moderate thermal crosslinking, the thickness dependent Tg deviation still exists, which diminishes in TFB films with a high crosslinking degree. The vertical charge carrier mobility of TFB thin films extracted from the SCLC measurements is found increase with film thickness, a value increases from 1 to 50 x 10-6 cm2 V-1 s-1 in the thickness range from 15 to 180 nm. Crosslinking was found to reduce the carrier mobility in TFB thin films. The Tg deviations are also discussed using the classic layered models in the literature. Our results provide a precise guide for the fabrication and design of high performance optoelectronic devices.

  2. 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.

  3. Creep performance of PVC aged at temperature relatively close to glass transition temperature

    Institute of Scientific and Technical Information of China (English)

    Zhi-hong ZHOU; Yao-long HE; Hong-jiu HU; Feng ZHAO; Xiao-long ZHANG

    2012-01-01

    In order to predict the mechanical performance of the polyvinyl chloride (PVC) at a high operating temperature,a series of short-term tensile creep tests (onetenth of the physical aging time) of the PVC are carried out at 63 ℃ with a small constant stress by a dynamic mechanical analyzer (DMA).The Struik-Kohlrausch (SK)formula and Struik shifting methods are used to describe these creep data for various physical aging time.A new phenomenological model based on the multiple relaxation mechanisms of an amorphous polymer is developed to quantitatively characterize the SK parameters (the initial creep compliance,the characteristic retardation time,and the shape factor) determined by the aging time.It is shown that the momentary creep compliance curve of the PVC at 63 ℃ can be very well fitted by the SK formula for each aging time.However,the SK parameters for the creep curves are not constant during the aging process at the elevated temperatures,and the evolution of these parameters and the creep rate versus aging time curves at the double logarithmic coordinates have shown a nonlinear phenomenon. Moreover,the creep master curves obtained by the superposition with the Struik shifting methods are unsatisfactory in such a case.Finally,the predicted results calculated from the present model incorporating with the SK formula are in excellent agreement with the creep experimental data for the PVC isothermally aged at the temperature relatively close to the glass transition temperature.

  4. The Doping Effect on Conductivity and Glass Transition Temperature of Solid Polymeric Electrolyte Based on Polyvinylchloride (pvc)

    Science.gov (United States)

    Abd. Rahman, Mohd. Yusri; Mat Salleh, Muhammad; Abu Talib, Ibrahim; Yahaya, Muhamad

    2002-12-01

    Solid electrolyte materials have been widely used in electrochemical devices such as batteries, solar cells and displays. This is because of its advantages over the liquidmaterial.This paper is concerned with the preparation of solid polymeric electrolyte based on polyvinylchloride (PVC) and its conductivity .The effect of percentage by weight of dopant material (LiClO4) on conductivity and glass transition temperature of the electrolyte was studied by using differential scanning calorimeter (DSC) and impedance spectroscopy technique. The electrolyte doped with 4.8%wt LiClO4 exhibits the highest conductivitiy of 7 × 10-6Scm-1 at room temperature but has the lowest glass transition temperature of 36.37°C. The other results are presented in this paper.

  5. Glass transition dynamics of anti-inflammatory ketoprofen studied by Raman scattering and terahertz time-domain spectroscopy

    Science.gov (United States)

    Shibata, Tomohiko; Igawa, Hikaru; Kim, Tae Hyun; Mori, Tatsuya; Kojima, Seiji

    2014-03-01

    A liquid-glass transition and a crystalline state of pharmaceutical racemic ketoprofen were studied by Raman scattering and the broadband terahertz time-domain spectroscopy (THz-TDS) in the frequency range from 9 to 260 cm-1. The low-frequency Raman scattering spectra clearly shows the remarkable change related to a liquid-glass transition at about Tg = 267 K. After melt-quenching at liquid nitrogen temperature, a boson peak appears at about 16.5 cm-1 near and below Tg and the intensity of quasi-elastic scattering related to structural relaxation increases markedly on heating. The crystalline racemic ketoprofen of "conformer A" shows the noncoincidence effect of mode frequencies below 200 cm-1 between Raman scattering spectra and dielectric spectra observed by THz-TDS.

  6. Fragility and glass transition for binary mixtures of 1,2-propanediol and LiBF4

    Science.gov (United States)

    Terashima, Y.; Mori, M.; Sugimoto, N.; Takeda, K.

    2014-04-01

    The fragility and glass transition for binary mixtures of 1,2-propanediol and LiBF4 were investigated by measuring the heating rate dependence of glass transition temperature (Tg) using differential scanning calorimetry. With increasing LiBF4 mole fraction, x, up to 0.25, fragility, m, increased rapidly from 53 to 85, and then remained approximately unchanged for x > 0.25. The concentration dependences of Tg and heat capacity jump at Tg also showed anomalies around x = 0.25. We suggest this mixture transformed from a moderate to quite fragile liquid at x = 0.25 because of a structural change from a hydrogen-bonding- to ionic-interaction-dominant system.

  7. PECH和GAP的玻璃化转变温度研究%Glass-transition Temperature of PECH and GAP

    Institute of Scientific and Technical Information of China (English)

    宋晓庆; 周集义; 王文浩; 王建伟; 白森虎

    2008-01-01

    @@ Glycidyl azide polymer (GAP) is one of the most recognized and prominent azide polymer. Because of its superior properties,GAP is used extensively as a high energetic binder or plasticizer in propellants to increase burning and specific impulse. It is very important to research on the glass-transition temperature (Tg) of GAP and its precursor PECH (poly-epichlorohydrin) due to the Tg of binders is the key factor which can influence low temperature properties of solid propellants.

  8. 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...

  9. Coil–globule transition of a polymer involved in excluded-volume interactions with macromolecules

    Energy Technology Data Exchange (ETDEWEB)

    Odagiri, Kenta [School of Network and Information, Senshu University, Kawasaki 214-8580 (Japan); Seki, Kazuhiko, E-mail: k-seki@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, Tsukuba, Ibaraki 305-8565 (Japan)

    2015-10-07

    Polymers adopt extended coil and compact globule states according to the balance between entropy and interaction energies. The transition of a polymer between an extended coil state and compact globule state can be induced by changing thermodynamic force such as temperature to alter the energy/entropy balance. Previously, this transition was theoretically studied by taking into account the excluded-volume interaction between monomers of a polymer chain using the partition function. For binary mixtures of a long polymer and short polymers, the coil-globule transition can be induced by changing the concentration of the shorter polymers. Here, we investigate the transition caused by short polymers by generalizing the partition function of the long polymer to include the excluded-volume effect of short polymers. The coil-globule transition is studied as a function of the concentration of mixed polymers by systematically varying Flory’s χ-parameters. We show that the transition is caused by the interplay between the excluded-volume interaction and the dispersion state of short polymers in the solvent. We also reveal that the same results can be obtained by combining the mixing entropy and elastic energy if the volume of a long polymer is properly defined.

  10. A mode coupling theory analysis of viscoelasticity near the kinetic glass transition of a copolymer micellar system

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Tartaglia, Piero [Dipartimento di Fisica, INFM and Statistical Mechanics and Complexity Center, Universita di Roma La Sapienza, I-00185 Rome (Italy); Chen W R [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Faraone, Antonio [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Chen, S H [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2004-10-27

    We report a set of viscoelastic measurements in concentrated aqueous solutions of a copolymer micellar system with short-range inter-micellar attractive interactions, a colloidal system characterized, in different regions of the composition-temperature phase diagram, by the existence of a percolation line (PT) and a kinetic glass transition (KGT). Both these transitions cause dramatic changes in the system viscoelasticity. Whereas the observed variations of the shear moduli at the PT are described in terms of percolation models, for the structural arrest at the KGT we investigate the frequency-dependent shear modulus behaviours by using a mode coupling theory (MCT) approach.

  11. 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

    2013-03-01

    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 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

  12. SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing

    Directory of Open Access Journals (Sweden)

    Yaning Kong

    2016-08-01

    Full Text Available In order to investigate the effects of microwave curing on the microstructure of the interfacial transition zone of mortar prepared with a composite binder containing glass powder and to explain the mechanism of microwave curing on the improvement of compressive strength, in this study, the compressive strength of mortar under microwave curing was compared against mortar cured using (a normal curing at 20 ± 1 °C with relative humidity (RH > 90%; (b steam curing at 40 °C for 10 h; and (c steam curing at 80 °C for 4 h. The microstructure of the interfacial transition zone of mortar under the four curing regimes was analyzed by Scanning electron microscopy (SEM. The results showed that the improvement of the compressive strength of mortar under microwave curing can be attributed to the amelioration of the microstructure of the interfacial transition zone. The hydration degree of cement is accelerated by the thermal effect of microwave curing and Na+ partially dissolved from the fine glass powder to form more reticular calcium silicate hydrate, which connects the aggregate, calcium hydroxide, and non-hydrated cement and glass powder into a denser integral structure. In addition, a more stable triangular structure of calcium hydroxide contributes to the improvement of compressive strength.

  13. Effects of heating conditions on the glass transition parameters of amorphous sucrose produced by melt-quenching.

    Science.gov (United States)

    Lee, Joo Won; Thomas, Leonard C; Schmidt, Shelly J

    2011-04-13

    This research investigates the effects of heating conditions used to produce amorphous sucrose on its glass transition (T(g)) parameters, because the loss of crystalline structure in sucrose is caused by the kinetic process of thermal decomposition. Amorphous sucrose samples were prepared by heating at three different scan rates (1, 10, and 25 °C/min) using a standard differential scanning calorimetry (SDSC) method and by holding at three different isothermal temperatures (120, 132, and 138 °C) using a quasi-isothermal modulated DSC (MDSC) method. In general, the quasi-isothermal MDSC method (lower temperatures for longer times) exhibited lower T(g) values, larger ΔC(p) values, and broader glass transition ranges (i.e., T(g end) minus T(g onset)) than the SDSC method (higher temperatures for shorter times), except at a heating rate of 1 °C/min, which exhibited the lowest T(g) values, the highest ΔC(p), and the broadest glass transition range. This research showed that, depending on the heating conditions employed, a different amount and variety of sucrose thermal decomposition components may be formed, giving rise to wide variation in the amorphous sucrose T(g) values. Thus, the variation observed in the literature T(g) values for amorphous sucrose produced by thermal methods is, in part, due to differences in the heating conditions employed.

  14. 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.

  15. Roles of water and solids composition in the control of glass transition and stickiness of milk powders.

    Science.gov (United States)

    Silalai, Nattiga; Roos, Yrjö H

    2010-06-01

    Plasticization and glass transition of amorphous components in food powders often result in stickiness and caking. The glass transition temperature (T(g)) of milk powders was measured by differential scanning calorimetry (DSC) and a viscometer method was used to determine sticky-point temperatures. Water sorption isotherms were established for varying solids compositions. Lactose contents were analyzed by high-performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) and proteins were identified using SDS-PAGE gel electrophoresis. Solids composition and water affected both the T(g) and stickiness behavior. Stickiness was governed by carbohydrates and water plasticization. At low protein contents, precrystallization of lactose decreased the sticky point temperature, but increasing protein content in all milk powders decreased stickiness at all water activities. The results showed that glass transition can be used to describe time-dependent stickiness and crystallization phenomena, and it can be used as a parameter to control and reduce stickiness of dairy solids with various compositions.

  16. Study of the deconfinement phase transition in a finite volume with massive particles: Hydrodynamics of the system near the transition

    Energy Technology Data Exchange (ETDEWEB)

    Ghenam, L.; Djoudi, A. Ait El [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Superieure - Kouba, B.P. 92, 16050, Vieux Kouba, Algiers (Algeria)

    2012-06-27

    We study the finite size and finite mass effects for the thermal deconfinement phase transition in Quantum Chromodynamics (QCD), using a simple model of coexistence of hadronic (H) gas and quark-gluon plasma (QGP) phases in a finite volume. We consider the equations of state of the two phases with the QGP containing two massless u and d quarks and massive s quarks, and a hadronic gas of massive pions, and we probe the system near the transition. For this, we examine the behavior of the most important hydrodynamical quantities describing the system, at a vanishing chemical potential ({mu}= 0), with temperature and energy density.

  17. High-level waste borosilicate glass a compendium of corrosion characteristics. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Cunnane, J.C. [comp.; Bates, J.K.; Bradley, C.R. [Argonne National Lab., IL (United States)

    1994-03-01

    Current plans call for the United States Department of Energy (DOE) to start up facilities for vitrification of high-level radioactive waste (HLW) stored in tanks at the Savannah River Site, Aiken, South Carolina, in 1995; West Valley Demonstration Project, West Valley, New York, in 1996; and at the Hanford Site, Richland, Washington, after the year 2000. The product from these facilities will be canistered HLW borosilicate glass, which will be stored, transported, and eventually disposed of in a geologic repository. The behavior of this glass waste product, under the range of likely service conditions, is the subject of considerable scientific and public interest. Over the past few decades, a large body of scientific information on borosilicate waste glass has been generated worldwide. The intent of this document is to consolidate information pertaining to our current understanding of waste glass corrosion behavior and radionuclide release. The objective, scope, and organization of the document are discussed in Section 1.1, and an overview of borosilicate glass corrosion is provided in Section 1.2. The history of glass as a waste form and the international experience with waste glass are summarized in Sections 1.3 and 1.4, respectively.

  18. Multichannel 1 → 2 transition amplitudes in a finite volume

    Energy Technology Data Exchange (ETDEWEB)

    Briceno, Raul A. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Hansen, Maxwell T. [Univ. of Washington, Seattle, WA (United States); Walker-Loud, Andre [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)

    2015-02-03

    We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B⁰ → K*l⁺l⁻) or meson photo production (e.g., πγ* → ππ). We observe that, while the spectrum solely depends upon the on-shell scattering amplitude, the correlation functions also depend upon off-shell amplitudes. The main result of this work is a non-perturbative generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular-momentum. The result is exact up to exponentially suppressed corrections governed by the pion mass times the box size. We also apply our master equation to various examples, including two processes mentioned above as well as examples where the final state is an admixture of two open channels.

  19. Temperature-dependent phase transitions in zeptoliter volumes of a complex biological membrane

    Energy Technology Data Exchange (ETDEWEB)

    Nikiforov, Maxim P; Jesse, Stephen; Kalinin, Sergei V [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Hohlbauch, Sophia; Proksch, Roger [Asylum Research, Santa Barbara, CA 93117 (United States); King, William P [Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801 (United States); Voitchovsky, Kislon [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Contera, Sonia Antoranz [Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, Oxford (United Kingdom)

    2011-02-04

    Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50-60 deg. C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 {+-} 5 deg. C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.

  20. Temperature-dependent phase transitions of a complex biological membrane in zeptoliter volumes

    Energy Technology Data Exchange (ETDEWEB)

    Nikiforov, Maxim [ORNL; Hohlbauch, Sophia [Asylum Research, Santa Barbara, CA; King, William P [University of Illinois, Urbana-Champaign; Voitchovsky, K [Massachusetts Institute of Technology (MIT); Contera, S Antoranz [University of Oxford; Jesse, Stephen [ORNL; Kalinin, Sergei V [ORNL; Proksch, Roger [Asylum Research, Santa Barbara, CA

    2011-01-01

    Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50 60 C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 5 C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.

  1. Formation and dilatation of shear bands in a Cu-Zr metallic glass: A free volume perspective

    Science.gov (United States)

    Tang, Chunguang; Peng, Hailong; Chen, Yu; Ferry, Michael

    2016-12-01

    We report the tensile deformation behaviour of metallic glass Cu50Zr50 as a function of quenching rate using molecular dynamics simulations. The atomic-scale shearing is found to be independent of atomic free volume, and the macroscopic correlation between the yield strength and density (or average free volume) is a coincidence, whereby samples with large free volume also have a low density of shear-resistant local five-fold symmetry. In the relatively slowly quenched (≤1010 K/s) samples, shear bands have a dilatation about 0.5%, which compares well with recent experimental results. In contrast, although more active local shearing occurs in the rapidly quenched samples, shear banding is not observed. This is because the strain energy disperses into local atomic shearing at the macroscopically elastic stage and, hence, is not sufficient for shear band activation, resulting in homogeneous deformation and appreciable plasticity.

  2. The role of the cytoskeleton in volume regulation and beading transitions in PC12 neurites

    CERN Document Server

    Fernandez, Pablo

    2010-01-01

    We present investigations on volume regulation and beading shape transitions in PC12 neurites conducted using a flow-chamber technique. By disrupting the cell cytoskeleton with specific drugs we investigate the role of its individual components in the volume regulation response. We find that microtubule disruption increases both swelling rate and maximum volume attained, but does not affect the ability of the neurite to recover its initial volume. In addition, investigation of axonal beading --also known as pearling instability-- provides additional clues on the mechanical state of the neurite. We conclude that the initial swelling phase is mechanically slowed down by microtubules, while the volume recovery is driven by passive diffusion of osmolites. Our experiments provide a framework to investigate the role of cytoskeletal mechanics in volume homeostasis.

  3. Acute blood volume expansion delays the gastrointestinal transit of a charcoal meal in awake rats

    Directory of Open Access Journals (Sweden)

    de-Oliveira G.R.

    1998-01-01

    Full Text Available The present study evaluates the effect of blood volume expansion on the gastrointestinal transit of a charchoal meal (2.5 ml of an aqueous suspension consisting of 5% charcoal and 5% gum arabic in awake male Wistar rats (200-270 g. On the day before the experiments, the rats were anesthetized with ether, submitted to left jugular vein cannulation and fasted with water ad libitum until 2 h before the gastrointestinal transit measurement. Blood volume expansion by iv infusion of 1 ml/min Ringer bicarbonate in volumes of 3, 4 or 5% body weight delayed gastrointestinal transit at 10 min after test meal administration by 21.3-26.7% (P<0.05, but no effect was observed after 1 or 2% body weight expansion. The effect of blood volume expansion (up to 5% body weight on gastrointestinal transit lasted for at least 60 min (P<0.05. Mean arterial pressure increased transiently and central venous pressure increased and hematocrit decreased (P<0.05. Subdiaphragmatic vagotomy and yohimbine (3 mg/kg prevented the delay caused by expansion on gastrointestinal transit, while atropine (0.5 mg/kg, L-NAME (2 mg/kg, hexamethonium (10 mg/kg, prazosin (1 mg/kg or propranolol (2 mg/kg were ineffective. These data show that blood volume expansion delays the gastrointestinal transit of a charcoal meal and that vagal and yohimbine-sensitive pathways appear to be involved in this phenomenon. The delay in gastrointestinal transit observed here, taken together with the modifications of gastrointestinal permeability to salt and water reported by others, may be part of the mechanisms involved in liquid excess management.

  4. Optical stability of 3d transition metal ions doped-cadmium borate glasses towards γ-rays interaction

    Science.gov (United States)

    Marzouk, M.; ElBatal, H.; Eisa, W.

    2016-07-01

    This work reports the preparation of glasses of binary cadmium borate with the basic composition (mol% 45 CdO 55 B2O3) and samples of the same composition containing 0.2 wt% dopants of 3d transition metal (TM) oxides (TiO2 → CuO). The glasses have been investigated by combined optical and Fourier Transform infrared spectroscopic measurements before and after being subjected to gamma irradiation with a dose of 8 Mrad (8 × 104 Gy). Optical absorption of the undoped glass before irradiation reveals strong charge transfer UV absorption which is related to the presence of unavoidable contaminated trace iron impurities (mainly Fe3+) within the raw materials used for the preparation of the base cadmium borate glass. The optical spectra of the 3d TM ions exhibit characteristic bands which are related the stable oxidation state of the 3d TM ions within the host glass. Gamma irradiation produces some limited variations in the optical spectra due to the stability of the host glass containing high percent 45 mol% of heavy metal oxide (CdO) which causes some shielding effects towards irradiation. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (∆E) have been calculated. The values of the optical energy gap are found to be dependent on the glass composition. Infrared absorption spectral measurements reveal characteristic absorption bands due to both triangular and tetrahedral borate groups with the BO3 units vibrations more intense than BO4 units due to the known limit value for the change of BO3 to BO4 groups. The introduction of 3d TM ions with the doping level (0.2 wt%) causes no changes in the number or position of the IR bands because of the presence of TM ions in modifying sites in the glass network. It is observed that gamma irradiation causes some limited changes in the FT-IR spectral bands due to the stability of the host heavy cadmium borate glass.

  5. Confirmation of temperature independence in the fluorescence lifetime of the 3P 0 → 3F 2 transition in praseodymium-doped fluoride glass

    Science.gov (United States)

    Nguyen, Thinh B.; Vella, Vince; Baxter, Greg W.; Collins, Stephen F.; Newman, Peter J.; MacFarlane, Douglas R.

    2006-05-01

    The dependence of the fluorescence lifetime from the 3P0 → 3F2 transition in praseodymium-doped fluoride glass as a function of dopant concentration and temperature was investigated. It was found that the fluorescence lifetime at the concentration of 7000 ppm was constant with temperature, confirming the prediction of temperature independence in the lifetime for this transition in Pr3+-doped ZBLAN glass.

  6. Study on the pulmonary mean transit time and the pulmonary blood volume by RI-cardiogram

    Energy Technology Data Exchange (ETDEWEB)

    Ushio, N.

    1987-03-01

    The pulmonary mean transit time and the pulmonary blood volume in cases of cardio-pulmonary disease were measured using Giuntini's method which is considered the most appropriate among radiocardiographic methods. The errors in this method were confirmed to be almost negligible. The results obtained were as follows: 1) The pulmonary mean transit time was related to the systemic mean transit time and markedly prolonged in left heart failure. On the other hand, it was markedly shortened in some cases of chronic pulmonary disease, particularly pulmonary emphysema. 2) The pulmonary blood volume tended to increase in left heart disorders and mitral valve disease and tended to decrease in the chronic pulmonary disease. The decrease was conspicuous particularly in some cases of pulmonary emphysema. 3) A structural change of the pulmonary vascular system in the chronic pulmonary disease appeared to bring about shortening of the pulmonary mean transit time and a decrease in the pulmonary blood volume. The pathophysiology of cardio-pulmonary disease can be more clarified by the RI-cardiogram used in this study, in which the pulmonary mean transit time and the pulmonary blood volume are used as the indicator.

  7. Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields

    Science.gov (United States)

    Morais, C. V.; Zimmer, F. M.; Lazo, M. J.; Magalhães, S. G.; Nobre, F. D.

    2016-06-01

    The behavior of the nonlinear susceptibility χ3 and its relation to the spin-glass transition temperature Tf in the presence of random fields are investigated. To accomplish this task, the Sherrington-Kirkpatrick model is studied through the replica formalism, within a one-step replica-symmetry-breaking procedure. In addition, the dependence of the Almeida-Thouless eigenvalue λAT (replicon) on the random fields is analyzed. Particularly, in the absence of random fields, the temperature Tf can be traced by a divergence in the spin-glass susceptibility χSG, which presents a term inversely proportional to the replicon λAT. As a result of a relation between χSG and χ3, the latter also presents a divergence at Tf, which comes as a direct consequence of λAT=0 at Tf. However, our results show that, in the presence of random fields, χ3 presents a rounded maximum at a temperature T* which does not coincide with the spin-glass transition temperature Tf (i.e., T*>Tf for a given applied random field). Thus, the maximum value of χ3 at T* reflects the effects of the random fields in the paramagnetic phase instead of the nontrivial ergodicity breaking associated with the spin-glass phase transition. It is also shown that χ3 still maintains a dependence on the replicon λAT, although in a more complicated way as compared with the case without random fields. These results are discussed in view of recent observations in the LiHoxY1 -xF4 compound.

  8. Continuous Structural Transition in Glass-Forming Molten Titanate BaTi 2 O 5

    Energy Technology Data Exchange (ETDEWEB)

    Alderman, O. L. G.; Benmore, C. J.; Tamalonis, A.; Sendelbach, S.; Heald, S.; Weber, R.

    2016-12-01

    The structure of the model titanate glass former BaTi2O5 has been studied over a wide temperature (T) range in the molten, supercooled, and glassy states under conditions of aerodynamic levitation. Both high-energy X-ray diffraction and Ti K-edge X-ray absorption spectroscopy reveal a continuous structural transition involving reduction of the cation-oxygen (and oxygen-cation) average coordination numbers and bond lengths with increasing T. Ti-0 coordination in the moderately supercooled and equilibrium melt follows a linear trend n(Tio) = 5.4(1)- [3.5(7) x 10(-4)]T [K] (1300 <= T <= 1830 K, T-g = 960 K, T-m = 1660 K). Comparison to the melt-quenched glass implies an increase in partial derivative n(Tio)/partial derivative T at lower T, as T-g is approached from above. Both Ba-0 coordination and bond length also decrease at higher T, and the role of Ba addition is to reduce n(Tio) below its value in pure molten TiO2, which is related to the presence of density maxima in molten BaO-TiO2. Density measurements made by imaging of the levitated melt yielded rho(T) = 4.82(55)- 0.0004(3)T in units of K and g cm(-3). While BaTi2O5 glass likely consists of a fully connected Ti-0 network, free of nonbridging oxygen (NBO) [OTi1 and with at least 13(4)% [OTi3] triclusters, the 1835(40) K equilibrium melt contains at least 10(4)% NBO along with 90(4)% bridging oxygen [OTi2]. The results highlight the fact that glasses can be considered as structural analogues of melts only for those melts deeply supercooled into the glass transition region. The results imply possible fictive T dependence of titanate glass structure, suggesting applications as, e.g., laser written waveguides with large refractive indices and refractive index contrasts. The temperature-dependent structure further implies a super-Arrhenian melt viscosity with consequences for glass manufacture, titanate-rich slags produced in iron smelting, TiO2-bearing magmas, and by analogy silicate melts at high pressures, as

  9. 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.

  10. Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge -V -Te (V =As , Sb) Liquid Alloys: The Difference One Element Can Make

    Science.gov (United States)

    Wei, Shuai; Coleman, Garrett J.; Lucas, Pierre; Angell, C. Austen

    2017-03-01

    Glass-transition temperatures (Tg ) and liquid fragilities are measured along a line of constant Ge content in the system Ge-As-Te, and contrasted with the lack of glass-forming ability in the twin system Ge-Sb-Te at the same Ge content. The one composition established as free of crystal contamination in the latter system shows a behavior opposite to that of a more covalent system. The comparison of Tg vs bond density in the three systems Ge-As-chalcogen differing in chalcogen, i.e., S, Se, or Te, shows that as the chalcogen becomes more metallic, i.e., in the order S ambient pressure) melting point.

  11. 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.

  12. Heat capacities and volumetric changes in the glass transition range: a constitutive approach based on the standard linear solid

    Science.gov (United States)

    Lion, Alexander; Mittermeier, Christoph; Johlitz, Michael

    2017-09-01

    A novel approach to represent the glass transition is proposed. It is based on a physically motivated extension of the linear viscoelastic Poynting-Thomson model. In addition to a temperature-dependent damping element and two linear springs, two thermal strain elements are introduced. In order to take the process dependence of the specific heat into account and to model its characteristic behaviour below and above the glass transition, the Helmholtz free energy contains an additional contribution which depends on the temperature history and on the current temperature. The model describes the process-dependent volumetric and caloric behaviour of glass-forming materials, and defines a functional relationship between pressure, volumetric strain, and temperature. If a model for the isochoric part of the material behaviour is already available, for example a model of finite viscoelasticity, the caloric and volumetric behaviour can be represented with the current approach. The proposed model allows computing the isobaric and isochoric heat capacities in closed form. The difference c_p -c_v is process-dependent and tends towards the classical expression in the glassy and equilibrium ranges. Simulations and theoretical studies demonstrate the physical significance of the model.

  13. Solid volume fraction estimation of bone:marrow replica models using ultrasound transit time spectroscopy.

    Science.gov (United States)

    Wille, Marie-Luise; Langton, Christian M

    2016-02-01

    The acceptance of broadband ultrasound attenuation (BUA) for the assessment of osteoporosis suffers from a limited understanding of both ultrasound wave propagation through cancellous bone and its exact dependence upon the material and structural properties. It has recently been proposed that ultrasound wave propagation in cancellous bone may be described by a concept of parallel sonic rays; the transit time of each ray defined by the proportion of bone and marrow propagated. A Transit Time Spectrum (TTS) describes the proportion of sonic rays having a particular transit time, effectively describing the lateral inhomogeneity of transit times over the surface aperture of the receive ultrasound transducer. The aim of this study was to test the hypothesis that the solid volume fraction (SVF) of simplified bone:marrow replica models may be reliably estimated from the corresponding ultrasound transit time spectrum. Transit time spectra were derived via digital deconvolution of the experimentally measured input and output ultrasonic signals, and compared to predicted TTS based on the parallel sonic ray concept, demonstrating agreement in both position and amplitude of spectral peaks. Solid volume fraction was calculated from the TTS; agreement between true (geometric calculation) with predicted (computer simulation) and experimentally-derived values were R(2)=99.9% and R(2)=97.3% respectively. It is therefore envisaged that ultrasound transit time spectroscopy (UTTS) offers the potential to reliably estimate bone mineral density and hence the established T-score parameter for clinical osteoporosis assessment.

  14. Glass-covering of large building volumes. An interdisciplinary evaluation of a shopping centre

    Energy Technology Data Exchange (ETDEWEB)

    Oeman, R. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Building Technology

    1994-12-31

    Systematized experiences of the function of large glass-covered spaces related to shopping centres, hotels, office buildings etc. are still relatively limited. With the glazed pedestrian precincts of the rebuilt Skaerholmen Centre in Stockholm as the main object of interdisciplinary studies, the aim of this thesis is to provide additional knowledge of large glass-covered spaces (atrium buildings). The studies comprises thermal comfort, temperature conditions, ventilation, energy balance, humidity - mycology, acoustics, operation - maintenance - durability and sociology. To sum up, it is clear that in the Scandinavian climate there is every likelihood of large glass-covered spaces in the public places functioning well from a technical as well as a social point of view. The energy consumption on heating the whole complex, based on theoretical calculations and measurement, is shown to have been reduced by the order of 10%. figs., tabs., refs.

  15. Estimating changes in Stroke Volume by non-invasive pulse-oximetry Pulse Transit Time Measurements

    NARCIS (Netherlands)

    ten Bokkel-Andela, J.; Poterman, Marieke; Scheeren, Thomas; Kalmar, A.F.

    2015-01-01

    Background and Goal of Study:  Pulse wave transit time (PTT), the interval between the R-wave peak on an electrocardiogram (ECG) and arrival of the pulse waves in the periphery (e.g. the finger), is reported to be a reliable estimate for stroke volume[1,2]. In this study, the PTT based on ECG and th

  16. Transitions of amorphous- crystalline-amorphous in bulk metallic glass under HP and HT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In-situ SR-XRD measurements revealed that the crystallization process in Zr41.2Ti13.sCu12.5Ni10Be22.5 bulk metallic glass is significantly different from that in traditional glasses. Subsequent heating at 10 GPa converts the sample from amorphous phase into the metastable fcc phase and then leads to the fcc phase back to the amorphous phase,nomena in the material under high pressure and high temperature.``

  17. [Calculation and analysis of optical transitions of Pr3+ ions in fluoride glass].

    Science.gov (United States)

    Kang, Dong-guo; Chen, Xiao-bo; Li, Song; Cui, Jian-sheng; Cai, Qing; Yu, Bao-Ting

    2007-01-01

    Intensity parameters of Pr3+ in ZBLAN glass were calculated using Judd-Ofelt(J-O) theory with absorption spectrum measurement. The anomalous behavior of Pr3+ was discussed using J-O theory. Base on the intensity parameters, the optical parameters such as spontaneous emission rate, branching ratio, and integrated emission cross section etc were predicted. The future of the glass as a laser material was discussed, and the probability of photon avalanche in the material was also analysed.

  18. Vanishing linear term in chemical potential difference in volume term of work of critical nucleus formation for phase transition without volume change

    CERN Document Server

    Mori, Atsushi

    2013-01-01

    A question is given on the form n({\\mu}_{\\beta}-{\\mu}_{\\alpha}) for the volume term of work of formation of critical nucleus. Here, n is the number of molecule undergone the phase transition, {\\mu} denotes the chemical potential, {\\alpha} and {\\beta} represent the parent and nucleating phases, respectively. In this paper we concentrate phase transition without volume change. We have calculated the volume term in terms of the chemical potential difference {\\mu}_{re}-{\\mu}_{eq}$ for this case. Here, {\\mu}_{re} is the chemical potential of the reservoir and {\\mu}_{eq} that at the phase transition. We have W_{vol} = -[({\\kappa}_{\\beta}-{\\kappa}_{\\alpha})/(2v_{eq}^2)] ({\\mu}_{re}-{\\mu}_{eq})^2 V_{\\beta} with {\\kappa} denoting the isothermal compressibility, v_{eq} being the molecular volume at the phase transition, V_{\\beta} the volume of the nucleus.

  19. Pulmonary blood volume and transit time in cirrhosis: relation to lung function

    DEFF Research Database (Denmark)

    Møller, Søren; Burchardt, H; Øgard, CG;

    2006-01-01

    not been determined separately we assessed PBV and pulmonary transit time (PTT) in relation to lung function in patients with cirrhosis and in controls. METHODS: Pulmonary and cardiac haemodynamics and transit times were determined by radionuclide techniques in 22 patients with alcoholic cirrhosis......BACKGROUND/AIMS: In cirrhosis a systemic vasodilatation leads to an abnormal distribution of the blood volume with a contracted central blood volume. In addition, the patients have a ventilation/perfusion imbalance with a low diffusing capacity. As the size of the pulmonary blood volume (PBV) has...... and in 12 controls. The lung function including diffusing capacity for carbon monoxide (DL, CO) was determined by conventional single breath technique. RESULTS: In the patients, PTT was shorter, 3.9+/-1.2 vs 5.7+/-1.0 s in the controls, P

  20. Pulmonary blood volume and transit time in cirrhosis: relation to lung function

    DEFF Research Database (Denmark)

    Møller, Søren; Burchardt, H; Øgard, CG

    2006-01-01

    BACKGROUND/AIMS: In cirrhosis a systemic vasodilatation leads to an abnormal distribution of the blood volume with a contracted central blood volume. In addition, the patients have a ventilation/perfusion imbalance with a low diffusing capacity. As the size of the pulmonary blood volume (PBV) has...... not been determined separately we assessed PBV and pulmonary transit time (PTT) in relation to lung function in patients with cirrhosis and in controls. METHODS: Pulmonary and cardiac haemodynamics and transit times were determined by radionuclide techniques in 22 patients with alcoholic cirrhosis...... and in 12 controls. The lung function including diffusing capacity for carbon monoxide (DL, CO) was determined by conventional single breath technique. RESULTS: In the patients, PTT was shorter, 3.9+/-1.2 vs 5.7+/-1.0 s in the controls, P

  1. 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.

  2. Optical properties and weakening of elastic moduli with increasing glass transition temperature (T{sub g}) in (80-x)TeO{sub 2}-xBaO-20ZnO glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Muliana; Supardan, Siti Nurbaya; Yahya, Ahmad Kamal [Univ. Teknologi Mara (Malaysia). School of Physics and Materials Studies; Abd-Shukor, Roslan [Univ. Kebangsaan Malaysia (Malaysia). School of Applied Physics

    2015-08-15

    BaO addition to ternary (80-x)TeO{sub 2}-20ZnO-xBaO (x = 0-20 mol.%) glasses resulted in a decrease in ultrasonic velocities and independent elastic moduli; this result indicated that the rigidity of the glass network weakened possibly because non-bridging oxygen increased. Thermal analysis results showed that glass transition temperature increased as BaO content increased because of the stabilizing effect of Ba{sup 2+} on the glass network. Additional analyses using bulk compression and ring deformation models revealed that the ratio between theoretical bulk modulus and experimental bulk modulus increased; this result indicated that the compression mechanism mainly involved isotropic ring compression. Furthermore, the increase in non-bridging oxygen formation with BaO addition caused a decrease in optical energy gap and an increase in refractive index. An increase in Urbach energy indicated that the degree of disorder in the glass system also increased.

  3. Volume 9 No. 3 2009 May 2009 859 ADAPTATION OF GLASS ...

    African Journals Online (AJOL)

    ADAPTATION OF GLASS COLUMNS FOR CLEAN-UP IN RP-HPLC. DETERMINATION OF ... C, the loss range was 20-50% and 30-55%, respectively. Aflatoxin recoveries .... Fifty grams of ground food sample were weighed out into a conical flask. 50µl was ..... In: Modern methods in the analysis and structural elucidation of ...

  4. The Compositional Variation of Microindentation Induced Densified and Plastic Deformation Volumes in Simple Silicate Glasses

    DEFF Research Database (Denmark)

    Hermansen, Christian; Matsuoka, Jun; Yoshida, Satoshi

    2012-01-01

    The densification and plastic deformation occurring in glass subjected to microindentation are established as two independent deformation mechanisms, and thought to be intimately linked to the concept of hardness and crack nucleation (quantified by the load at which radial cracks nucleate at half...

  5. 膨化干燥灰枣粉玻璃化转变及贮藏稳定性%Glass transition and storage stability for explosion puffing dried jujube powder

    Institute of Scientific and Technical Information of China (English)

    毕延娣; 陈芹芹; 毕金峰; 颜廷才; 吴昕烨; 赵悦

    2015-01-01

    为了综合水分活度及玻璃化转变理论构建状态图,获得灰枣粉的较佳贮藏条件,该文采用静态称量法和差示扫描量热法测定灰枣粉的吸附特性及玻璃化转变温度。结果表明,膨化干燥灰枣粉水分吸附的平衡干基含水率随水分活度的增加而增加,水分吸附等温线呈J型,描述灰枣粉水分吸附特性的适宜模型为GAB模型(R2=0.9968);灰枣粉的玻璃化转变温度随含水率升高而降低,湿基含水率由0.064增加到0.175 g/g时,玻璃化转变温度由29.90降低到−35.02℃;灰枣粉干基含水率≤0.1223 g/g、贮藏温度≤−0.062°C时其稳定性较好,研究结果为灰枣粉加工、运输等过程中的贮藏条件提供理论参考。%Since the 1980s, water activity has been commonly used to evaluate the food storage stability, and food storage will be more stable in or below the moisture content of monolayer molecular layer. Water activity is related to the composition, temperature and physical state of the compounds, and the physical state of food compounds is also related to the stability. But recently, some scholars had found the limitations of using water activity to assess the food storage stability, so the glass transition theory was proposed. Glass transition is a well-known change in the state of amorphous materials, and the characteristic temperature is the glass transition temperature. When the temperature is lower than the glass transition temperature, the system is in glass state, energy is low, viscosity is high, and the molecular chain is segmented into “frozen” state, so the system is relatively stable. On the contrary, when the system temperature is higher than the glass transition temperature, the system is in rubbery state, which leads to the viscosity reduction, the free volume increasing and a variety of changes in motion by diffusion-controlled reactions acceleration, so the system is unstable. Therefore, food in

  6. Determination of production efficiency, color, glass transition, and sticky point temperature of spray-dried pomegranate juice powder

    OpenAIRE

    Khalid Muzaffar; Sajad Ahmad Wani; Bijamwar Vilas Dinkarrao; Pradyuman Kumar

    2016-01-01

    The aim of the study was to determine the powder recovery, color characteristics, glass transition temperature (Tg), and sticky point (Ts) temperature of spray-dried pomegranate juice powder as affected by different concentrations of maltodextrin (DE 20). Five different combinations of pomegranate juice and maltodextrin (95:5, 90:10, 85:15, 80:20 and 75:25 v/w) were prepared and spray dried in a laboratory-type spray dryer. Increase in concentration of maltodextrin significantly increased the...

  7. Solving the initial condition of the string relaxation equation of the string model for glass transition: part-Ⅱ

    Institute of Scientific and Technical Information of China (English)

    Zhang Jin-Lu; Wang Li-Na; Zhao Xing-Yu; Zhang Li-Li; Zhou Heng-Wei; Wei Lai; Huang Yi-Neng

    2011-01-01

    The string model for the glass transition can quantitatively describe the universal α-relaxation in glassformers. The string relaxation equation (SRE) of the model simplifies the well-known Debye and Rouse-Zimm relaxation equations at high and low enough temperatures, respectively. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the general initial condition of the SRE for stochastically spatially configurative strings is solved exactly based on the obtained special initial condition of the SRE for straight strings in a previous paper (J. L. Zhang et al. 2010 Chin. Phya. B 19, 056403).

  8. 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…

  9. Stability, Tunneling and Flux Changing de Sitter Transitions in the Large Volume String Scenario

    CERN Document Server

    de Alwis, S; Hatefi, E; Quevedo, F

    2013-01-01

    We study the non-perturbative stability of the Large Volume Scenario (LVS) of IIB string compactifications, by analysing transitions mediated by the Brown-Teitelboim (BT) brane nucleations and by Coleman De Luccia tunneling (CDL). We find that, as long as the effective field theory description holds, the LVS AdS minima are stable despite being non-supersymmetric. This opens the possibility of having a CFT dual. Metastable de Sitter vacua behave differently depending on the uplifting mechanism. We find explicit expressions for the different decay rates in terms of exponentials of the volume. Among the transitions of dS to dS those with increasing volume and decreasing vacuum energy are preferred, though dS decays to AdS (big-crunch sinks) have higher probability. Transitions via the CDL mechanism to decompactification are exponentially suppressed compared to these. The BT decays correspond to flux/D3 brane transitions mediated by the nucleation of D5/NS5 branes. We compare our results with previous analysis fo...

  10. Relaxation times of nanoscale deformations on the surface of a polymer thin film near and below the glass transition

    Science.gov (United States)

    Papaléo, R. M.; Leal, R.; Carreira, W. H.; Barbosa, L. G.; Bello, I.; Bulla, A.

    2006-09-01

    We report on measurements of relaxation times of nanometer-sized deformations resulting from the impact of individual energetic ions on poly(methyl methacrylate) surfaces at temperatures close to and below the glass transition Tg . The temporal evolution of the dimensions of the deformations is well described by a stretched exponential function, but with relaxation times τ(T) many orders of magnitude smaller than bulk values at the same T . The local Tg was around 86°C , roughly 30°C below the conventional bulk Tg . At the vicinity of the local Tg , τ(T) follows the Vogel-Fulcher type of T dependence, but at lower T a transition towards a less steep behavior is seen.

  11. Observation of a Dynamic Crossover in RNA Hydration Water which Triggers the Glass Transition in the Biopolymer

    CERN Document Server

    Chu, X; Chen, S H; Faraone, A; Fratini, E; Baglioni, Piero; Chen, Sow-Hsin; Chu, Xiang-qiang; Faraone, Antonio; Fratini, Emiliano

    2007-01-01

    High-resolution quasi-elastic neutron scattering spectroscopy was used to measure H2O and D2O hydrated RNA samples. The contribution of scattering from RNA was subtracted out by taking the difference of the signals between the two samples. The measurements were made at a series of temperatures from 270 K down to 180 K. The Relaxing-Cage Model was used to analyze the difference quasi-elastic spectra. We observed clear evidence of a fragile-to-strong dynamic crossover (FSC) at TL = 220 K in RNA hydration water. We further show that the mean-square displacement of the hydrogen atoms in both RNA and its hydration water exhibit a sharp change in slope at approximately the same temperature 220 K. This latter fact suggests that the dynamic transition (or the glass transition) in RNA is triggered by the abrupt change of mobility of the hydration water at its FSC temperature TL.

  12. 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.

  13. Temperature-driven volume transition in hydrogels: Phase-coexistence and interface localization

    Science.gov (United States)

    Cirillo, E. N. M.; Nardinocchi, P.; Sciarra, G.

    2016-05-01

    We study volume transition phenomenon in hydrogels within the framework of Flory-Rehner thermodynamic modelling; we show that starting from different models for the Flory parameter different conclusions can be achieved, in terms of admissible coexisting equilibria of the system. In particular, with explicit reference to a one-dimensional problem we establish the ranges of both temperature and traction which allow for the coexistence of a swollen and a shrunk phase. Through consideration of an augmented Flory-Rehner free-energy, which also accounts for the gradient of volume changes, we determine the position of the interface between the coexisting phases, and capture the connection profile between them.

  14. Unraveling protein stabilization mechanisms : Vitrification and water replacement in a glass transition temperature controlled system

    NARCIS (Netherlands)

    Grasmeijer, N; Stankovic, M; de Waard, H; Frijlink, H W; Hinrichs, W L J

    2013-01-01

    The aim of this study was to elucidate the role of the two main mechanisms used to explain the stabilization of proteins by sugar glasses during drying and subsequent storage: the vitrification and the water replacement theory. Although in literature protein stability is often attributed to either v

  15. 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 frequen...

  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

    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. Dynamical transition in molecular glasses and proteins observed by spin relaxation of nitroxide spin probes and labels

    Science.gov (United States)

    Golysheva, Elena A.; Shevelev, Georgiy Yu.; Dzuba, Sergei A.

    2017-08-01

    In glassy substances and biological media, dynamical transitions are observed in neutron scattering that manifests itself as deviations of the translational mean-squared displacement, , of hydrogen atoms from harmonic dynamics. In biological media, the deviation occurs at two temperature intervals, at ˜100-150 K and at ˜170-230 K, and it is attributed to the motion of methyl groups in the former case and to the transition from harmonic to anharmonic or diffusive motions in the latter case. In this work, electron spin echo (ESE) spectroscopy—a pulsed version of electron paramagnetic resonance—is applied to study the spin relaxation of nitroxide spin probes and labels introduced in molecular glass former o-terphenyl and in protein lysozyme. The anisotropic contribution to the rate of the two-pulse ESE decay, ΔW, is induced by spin relaxation appearing because of restricted orientational stochastic molecular motion; it is proportional to τc, where is the mean-squared angle of reorientation of the nitroxide molecule around the equilibrium position and τc is the correlation time of reorientation. The ESE time window allows us to study motions with τc τc temperature dependence shows a transition near 240 K, which is in agreement with the literature data on . For spin probes of essentially different size, the obtained data were found to be close, which evidences that motion is cooperative, involving a nanocluster of several neighboring molecules. For the dry lysozyme, the τc values below 260 K were found to linearly depend on the temperature in the same way as it was observed in neutron scattering for . As spin relaxation is influenced only by stochastic motion, the harmonic motions seen in ESE must be overdamped. In the hydrated lysozyme, ESE data show transitions near 130 K for all nitroxides, near 160 K for the probe located in the hydration layer, and near 180 K for the label in the protein interior. For this system, the two latter transitions are not

  18. 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.

  19. Spectroscopic data of the 1.8-, 2.9-, and 4.3- mu m transitions in dysprosium-doped gallium lanthanum sulfide glass

    Science.gov (United States)

    Schweizer, T.; Hewak, D. W.; Samson, B. N.; Payne, D. N.

    1996-10-01

    Infrared emission at 1.8, 2.9, and 4.3 mu m is measured in dysprosium-doped gallium lanthanum sulfide (Ga:La:S) glass excited at 815 nm. Emission cross sections were calculated by Judd-Ofelt analysis, the Fuchtbauer-Ladenburg equation, and the theory of McCumber. The sigma tau value for the 4.3- mu m transition is \\similar 4000 times larger in the Ga:La:S glass than in a dysprosium-doped LiYF4 crystal, which has lased on this transition. The large sigma tau value and the recently reported ability of Ga:La:S glass to be fabricated into fiber form show the potential for an efficient, low-threshold mid-infrared fiber laser. The fluorescence peak at 4.3 mu m coincides with the fundamental absorption of atmospheric carbon dioxide, making the glass a potential laser source for gas-sensing applications.

  20. Spectroscopic data of the 1.8-, 2.9-, and 4.3-microm transitions in dysprosium-doped gallium lanthanum sulfide glass.

    Science.gov (United States)

    Schweizer, T; Hewak, D W; Samson, B N; Payne, D N

    1996-10-01

    Infrared emission at 1.8, 2.9, and 4.3 microm is measured in dysprosium-doped gallium lanthanum sulfide (Ga:La:S) glass excited at 815 nm. Emission cross sections were calculated by Judd-Ofelt analysis, the Füchtbauer- Ladenburg equation, and the theory of McCumber. The sigmatau value for the 4.3-microm transition is ~4000 times larger in the Ga:La:S glass than in a dysprosium-doped LiYF(4) crystal, which has lased on this transition. The large sigmatau value and the recently reported ability of Ga:La:S glass to be fabricated into fiber form show the potential for an efficient, low-threshold mid-infrared fiber laser. The f luorescence peak at 4.3 microm coincides with the fundamental absorption of atmospheric carbon dioxide, making the glass a potential laser source for gas-sensing applications.

  1. Raman scattering study of glass crystallization kinetics

    Science.gov (United States)

    Balkanski, M.; Haro, E.; Espinosa, G. P.; Phillips, J. C.

    1984-08-01

    Laser induced glass-crystalline transition is studied by light scattering. Three significant effects are observed depending on the incident laser energy density: (i) Spectral band narrowing indicating cluster enlargement constitutes a precursor effect, (ii) an intensity increase effect indicates a rapid rise of the density of clusters attaining microcrystalline size and (iii) a dynamical reversal effect indicative of glass-crystalline instability. Cluster volume and crystallization appear as separate but related threshold phenomena.

  2. Kinetics analysis of volume phase transition of intelligent neutral thermo-sensitive hydrogels

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this work,utilizing the first law of thermodynamics and the Flory mean-field theory,the kinetic deformation studies concerning the volume phase transition of the neutral thermo-sensitive hydrogels were performed analytically.The hydrogel was assumed as a biphasic mixture medium in the framework of the continuum mixture theory.From the energy conservation of the thermodynamics system of the hydrogel,the governing equations for the kinetics of the nonlinear large deforma-tion were derived.The explicit analytical expressions of the effective stress tensor and the chemical potential of the fluid of the thermo-sensitive hydrogel PNIPA were also obtained from the Helmholtz free energy,which can model the steady-static volume phase transition quantitatively.

  3. Kinetics analysis of volume phase transition of intelligent neutral thermo-sensitive hydrogels

    Institute of Scientific and Technical Information of China (English)

    WANG XiaoGui; LI YiQuan

    2008-01-01

    In this work, utilizing the first law of thermodynamics and the FIory mean-field theory, the kinetic deformation studies concerning the volume phase transition of the neutral thermo-sensitive hydrogels were performed analytically. The hydrogel was assumed as a biphasic mixture medium in the framework of the continuum mixture theory. From the energy conservation of the thermodynamics system of the hydrogel, the governing equations for the kinetics of the nonlinear large deforma-tion were derived. The explicit analytical expressions of the effective stress tensor and the chemical potential of the fluid of the thermo-sensitive hydrogel PNIPA were also obtained from the Helmholtz free energy, which can model the steady-static volume phase transition quantitatively.

  4. Prevalence for the universal distribution of relaxation times near the glass transitions in experimental model systems: Rodlike liquid crystals and orientationally disordered crystals

    OpenAIRE

    Martínez García, Julio Cesar; Tamarit Mur, José Luis; Rzosca, S. J.

    2011-01-01

    Recently, Nielsen et al. [J. Chem. Phys. 130, 154508 (2009); Philos. Mag. 88, 4101 (2008)] demonstrated a universal pattern for the high frequency wing of the loss curve for primary relaxation time on approaching the glass transition for organic liquids. In this contribution it is presented that a similar universality occurs for glass-forming liquid crystals and orientationally disordered crystals (plastic crystals). Empirical correlations of the found behavior are also briefly di...

  5. Prevalence for the universal distribution of relaxation times near the glass transitions in experimental model systems: Rodlike liquid crystals and orientationally disordered crystals

    OpenAIRE

    2011-01-01

    Recently, Nielsen et al. [J. Chem. Phys. 130, 154508 (2009); Philos. Mag. 88, 4101 (2008)] demonstrated a universal pattern for the high frequency wing of the loss curve for primary relaxation time on approaching the glass transition for organic liquids. In this contribution it is presented that a similar universality occurs for glass-forming liquid crystals and orientationally disordered crystals (plastic crystals). Empirical correlations of the found behavior are also briefly di...

  6. Study of rigidity of semiconducting vanadate glasses and its importance in use of coatings

    Indian Academy of Sciences (India)

    Yasser B Saddeek; M S Gaafar

    2014-05-01

    The elastic moduli of some multicomponent vanadate based glasses were analysed in terms of the bond compression model by some physical parameters such as, the density, average stretching force constant and average atomic ring size. These parameters were calculated for all the glass series and for all the glass composition to estimate the rigidity of these glasses. The results showed that the average force constant and the elastic moduli of these glasses are sensitive to the decrease in PbO content. This behaviour was attributed to the increase in the molar volume and the role of different modifiers. 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.

  7. Free volume effects on the fluorescence characteristics of sol-gel glasses doped with quinine sulphate

    Science.gov (United States)

    Meneses-Nava, M. A.; Barbosa-García, O.; Díaz-Torres, L. A.; Chávez-Cerda, S.; King, T. A.

    1999-12-01

    The broadening of the absorption and fluorescence spectra and the red shift of the fluorescence maximum of quinine sulfate doped sol-gel glasses, before and after PMMA polymer impregnation, are investigated at different concentrations. The fluorescence decay of the quinine sulfate doped samples does not fit to a single exponential, as it does in ethanol solutions. We found that a double exponential gives a good fit to the obtained results. Introduction of solvent to fill the pores of the matrix does not only have the same effect as the polymer, but also reveals the strong attachment of the molecules to the pore walls and the influence of the interaction with the cage.

  8. Highly Mobile Metastable State of He-4 Thin Films: A Glass Transition by Mechanical Perturbation?

    Science.gov (United States)

    Minoguchi, Tomoki

    2017-01-01

    Solid layers of helium on graphite surface are known to go into a highly mobile state (HMS) once the solid layer is enforced to slip on the substrate. The HMS collapses to the stable inert state with the lifetime extending over 10^4 s. In this paper, we suggest that the HMS is a structural glass by showing the similarities between the present system and an organic conductor named BEDT-TTF. The latter was recently discovered to be an electronic glass if the cooling rate is rapid enough across the freezing temperature (Wigner crystal formation temperature). We then address a novel annealing process promoted by a local condensate which should be seen for the present He-4 case as the condensation fraction grows in the liquid overlayer.

  9. Study on the spin crossover transition and glass transition for Fe(II) complex film, [Fe(II)(H-triazole){sub 3}]-Nafion, by means of Moessbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nakamoto, Akio; Kamebuchi, Hajime, E-mail: cc106909@mail.ecc.u-tokyo.ac.jp [University of Tokyo, Graduate School of Arts and Sciences (Japan); Enomoto, Masaya [Tokyo University of Science, Department of Chemistry, Faculty of Science Division I (Japan); Kojima, Norimichi [University of Tokyo, Graduate School of Arts and Sciences (Japan)

    2012-03-15

    [Fe(II)(H-trz){sub 3}]-Nafion (trz = triazole) is a transparent spin crossover complex film, where the spin crossover transition between the low-spin (S = 0) and the high-spin (S = 2) states takes place between 225 K and 300 K. In this film, two doublets corresponding to the low-spin and high-spin states were observed in the {sup 57}Fe Moessbauer spectra, reflecting the spin crossover transition. From the analysis of {sup 57}Fe Moessbauer spectra, the Debye temperatures of the low-spin and high-spin sites were estimated at 185 K and 176 K, respectively, in the temperature range between 10 K and 150 K. In this film, the total intensity of the Moessbauer spectra corresponding to the low-spin and high-spin sites drastically decreases above 200 K, reflecting the glass transition of Nafion, where the lattice vibration of [Fe(H-trz){sub 3}]{sub n}{sup 2n+} is softened just as in solution due to micro-Brown motion of the segment of Nafion polymer membrane.

  10. [Parameters with possible influence in PSA adjusted for transition zone volume].

    Science.gov (United States)

    Jara Rascón, J; Subirá Ríos, D; Lledó Garcia, E; Martínez Salamanca, J I; Moncada Iribarren, I; Cabello Benavente, R; Hernández Fernández, C

    2005-05-01

    To evaluate the effect of age, digital rectal examination results and prostatic volume on PSA value adjusted to transition zone (PSA-TZ) in the detection of prostatic cancer. Data of 243 patients with serum PSA of 4 to 20 ng/ml who underwent biopsy because of prostatic cancer suspicion are analyzed. In this population, cancer was detected in 62 cases (24.8%). Total prostatic volume and transition zone volume were calculated by transrectal echography applying the ellipsoid formula. Applying lineal regresion analysis, it was found no correlation between age and PSA-TZ (Pearson coefficient 0.00). By dividing these patients among those with normal rectal examination (84%) and those with suspicious digital rectal examination (16%), cutoff values of PSA-TZ were found to be not different by ROC curves analysis for 95% sensitivity varying specificity only among 24 and 26% between these two groups of patients. Prostatic size (40 cc) showed that, for obtaining the same 95% sensitivity in the detection of cancer, PSA-TZ value would require to be modified, being 0.17 in large prostates (> 40 cc) and 0.25 in small prostates (< or =40 cc). The utility of PSA-TZ as a potential predictor parameter of prostatic cancer did not need to be modified with respect to age or to data of digital rectal examination. However, for supporting sensivity of its best cutoff value, PSA-TZ would need to be modified with respect to total prostatic volume.

  11. Theoretical Study of Role of Sb in Se_0.85-xTe_0.15Sbx Chalcogenide Glass in Influencing Glass Transition Temperature

    Science.gov (United States)

    Maharjan, N. B.; Paudyal, D. D.; Jeong, J.; Scheicher, R. H.; Das, T. P.

    2001-03-01

    The influence of Sb impurity on glass transition temperature (Tg) has recently been studied using Differential Scanning Calorimetry(N. B. Maharjan et al., Phy. Stat. Sol. (a) 178, 663 (2000)). The results indicate that Tg initially increases with Sb concentration (x), reaching a maximum at 0.04, subsequently decreasing till x=0.06 and then becoming constant. Qualitative explanation of this behavior for Tg has been suggested^1 using earlier ideas in the literature regarding the role of Sb in the interaction between chains in the Se_1-xTex system and bond energy strength considerations involving Se-Se and Sb-Se bonds. These ideas are being tested quantitatively using Hartree-Fock Cluster procedures, previously utilized by our group for study(H. S. Cho et al., (to be published); H. S. Cho et al., Hyperfine Interactions 96, 213 (1995)) of nuclear quadrupole interactions including that of ^125Te in Selenium and Tellurium(P. Boolchand et al., Phys. Rev. Lett. 30, 1292 (1973)).

  12. Rings, chains and planes: Variation of g with composition in chalcogenide glasses

    Indian Academy of Sciences (India)

    P K Thiruvikraman

    2006-08-01

    We propose a microscopic, phenomenological model for the decrease in the viscosity observed at glass transition. Our model is primarily applicable to chalcogenide glasses. According to this model, the decrease in the viscosity at glass transition is mainly due to the breaking of the Van der Waals bonds in the chalcogenides. Using this model, we derive a relationship between the glass transition temperature, g, and the molar volume m. The validity of this relation is checked using experimental data available in the literature for two binary systems (Ge–Se and As–S) and a pseudo-binary system (As40SeTe60–).

  13. Characterizing the kinetics of volume recovery in glasses by instantaneous temperature-jump experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lagasse, R.R. (Sandia National Labs., Albuquerque, NM); Cohen, R.E.; Letton, A.

    1982-03-01

    This article proposes a temperature-jump (T-jump) approach for characterizing the kinetics of volume recovery in glassy materials. The kinetic characterization is based on the Kovacs-Aklonis model. This incorporates a retardation-time spectrum which shifts according to both the temperature and the instantaneous volume. The proposed experiments involve measuring the change in recovery rate caused by an abrupt temperature jump. Although an analogous procedure has been used to determine the activation energy for linear viscoelastic creep, the analysis for volume recovery is complicated by its inherent nonlinearity. Nevertheless, accounting for the nonlinearity by a reduction of the time scale permits the T-jump results to be analyzed. In particular, the T-jump approach can be used to: (i) test a particular functional form for the shift factor; and (ii) determine the previously unmeasurable parameter x, which defines the relative importance of the temperature dependence and the volume dependence in this function. In addition, numerical simulations indicate that the proposed method can be implemented in the laboratory. 7 figures.

  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. Snapshotted glass and gel transitions of stable colloidal dispersions after shear-driven aggregation in a microchannel.

    Science.gov (United States)

    Meng, Xia; Wu, Hua; Morbidelli, Massimo

    2015-02-07

    Intense shear can lead to aggregation of colloids that are highly stable at rest. The aggregation process typically has an induction time, and then becomes explosive, leading to rapid phase transitions. We study the phase evolution during shear-driven aggregation in a short microchannel (MC) under intense shear for a colloid with a high interaction energy barrier that ensures high stability of particles and clusters before and after intense shear. The short residence time allows us to snapshot the phase evolution by repeatedly cycling the colloid in the MC. It is found that, depending on the particle concentration, in addition to a fluid of clusters and a solid-like gel, there is another solid-like state between them: Wigner glass of clusters. Their transitions occur over a large range of particle concentrations. We have proposed a phase diagram that describes how the transitions of the three phases evolve in the aggregation steady state in the colloidal interaction vs. particle concentration plane.

  16. Transition from glass to digital slide microscopy in the teaching of oral pathology in a Brazilian dental school.

    Science.gov (United States)

    Fonseca, Felipe-Paiva; Santos-Silva, Alan-Roger; Lopes, Márcio-Ajudarte; Almeida, Oslei-Paes de; Vargas, Pablo-Agustin

    2015-01-01

    Several medical and dental schools have described their experience in the transition from conventional to digital microscopy in the teaching of general pathology and histology disciplines; however, this transitional process has scarcely been reported in the teaching of oral pathology. Therefore, the objective of the current study is to report the transition from conventional glass slide to virtual microscopy in oral pathology teaching, a unique experience in Latin America. An Aperio ScanScope® scanner was used to digitalize histological slides used in practical lectures of oral pathology. The challenges and benefits observed by the group of Professors from the Piracicaba Dental School (Brazil) are described and a questionnaire to evaluate the students' compliance to this new methodology was applied. An improvement in the classes was described by the Professors who mainly dealt with questions related to pathological changes instead of technical problems; also, a higher interaction with the students was described. The simplicity of the software used and the high quality of the virtual slides, requiring a smaller time to identify microscopic structures, were considered important for a better teaching process. Virtual microscopy used to teach oral pathology represents a useful educational methodology, with an excellent compliance of the dental students.

  17. Transition from glass to digital slide microscopy in the teaching of oral pathology in a Brazilian dental school

    Science.gov (United States)

    Fonseca, Felipe-Paiva; Santos-Silva, Alan-Roger; Lopes, Márcio-Ajudarte; de Almeida, Oslei-Paes

    2015-01-01

    Objectives: Several medical and dental schools have described their experience in the transition from conventional to digital microscopy in the teaching of general pathology and histology disciplines; however, this transitional process has scarcely been reported in the teaching of oral pathology. Therefore, the objective of the current study is to report the transition from conventional glass slide to virtual microscopy in oral pathology teaching, a unique experience in Latin America. Study Design: An Aperio ScanScope® scanner was used to digitalize histological slides used in practical lectures of oral pathology. The challenges and benefits observed by the group of Professors from the Piracicaba Dental School (Brazil) are described and a questionnaire to evaluate the students’ compliance to this new methodology was applied. Results: An improvement in the classes was described by the Professors who mainly dealt with questions related to pathological changes instead of technical problems; also, a higher interaction with the students was described. The simplicity of the software used and the high quality of the virtual slides, requiring a smaller time to identify microscopic structures, were considered important for a better teaching process. Conclusions: Virtual microscopy used to teach oral pathology represents a useful educational methodology, with an excellent compliance of the dental students. Key words:Digital microscopy, virtual microscopy, dental education, virtual slides, oral pathology. PMID:25129250

  18. Molecular dynamics simulation of cross-linked urea-formaldehyde polymers for self-healing nanocomposites: prediction of mechanical properties and glass transition temperature.

    Science.gov (United States)

    Arab, Behrouz; Shokuhfar, Ali

    2013-11-01

    Urea-formaldehyde polymers, which are utilized in the adhesives industry, have recently been shown to be suitable materials for synthesizing micro/nanocapsules for use in self-healing (nano)composites. In this study, molecular dynamics was employed to simulate the process in which urea and formaldehyde are cross-linked via methylene and ether cross linkers, and to study the structure and mechanical/thermal properties of simulated poly(urea-formaldehyde)s (PUFs). The elastic stiffness constants of the simulated materials were calculated using the constant-strain (static) method. A temperature cycle was applied to the cross-linked PUFs, and the glass transition behavior of each material was investigated through the mean squared displacement (MSD) and temperature evolution of the energy and the specific volume of the polymer. The simulation results confirmed that there was considerable improvement in the properties of the poly(UF) materials upon cross linking. The radial distribution function was also used to study the local structures of the polymers, and this revealed that increasing the temperature and cross linking density results in a significant drop in hydrogen bonding intensity in the cross-linked PUF systems.

  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) < 102 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 Ecoop(T) ≡ E(T)-E∞ increases exponentially while cooling. A scaling is introduced, specifically Ecoop(T)/E∞ ∝ exp[-λ(T/TA-1)], where λ is a fragility parameter and TA 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. Freeze-Drying Above the Glass Transition Temperature in Amorphous Protein Formulations While Maintaining Product Quality and Improving Process Efficiency.

    Science.gov (United States)

    Depaz, Roberto A; Pansare, Swapnil; Patel, Sajal Manubhai

    2016-01-01

    This study explored the ability to conduct primary drying during lyophilization at product temperatures above the glass transition temperature of the maximally freeze-concentrated solution (Tg′) in amorphous formulations for four proteins from three different classes. Drying above Tg′ resulted in significant reductions in lyophilization cycle time. At higher protein concentrations, formulations freeze dried above Tg′ but below the collapse temperature yielded pharmaceutically acceptable cakes. However, using an immunoglobulin G type 4 monoclonal antibody as an example, we found that as protein concentration decreased, minor extents of collapse were observed in formulations dried at higher temperatures. No other impacts to product quality, physical stability, or chemical stability were observed in this study among the different drying conditions for the different proteins. Drying amorphous formulations above Tg′, particularly high protein concentration formulations, is a viable means to achieve significant time and cost savings in freeze-drying processes.

  1. Spin-glass transition in Ni carbide single crystal nanoparticles with Ni3C − type structure

    Directory of Open Access Journals (Sweden)

    S. Fujieda

    2016-05-01

    Full Text Available Hexagonal shaped nanoparticles about 60 nm in size were successfully synthesized in tetraethylene glycol solution containing polyvinylpyrrolidone. By the analysis of the electron diffraction pattern, these were identified as a single crystal of Ni carbide with Ni3C − type structure. Their magnetization curve at 5 K was not completely saturated under a magnetic field of 5 T. The thermomagnetization curves after zero-field cooling and after field cooling exhibited the magnetic cooling effect at low temperatures. Furthermore, the 2nd order nonlinear term of AC magnetic susceptibility exhibited a negative divergence at about 17 K. It is concluded that Ni carbide single crystal nanoparticles with the Ni3C − type structure exhibit spin-glass transition at low temperatures.

  2. Phenomenological theory of a renormalized simplified model based on time-convolutionless mode-coupling theory near the glass transition

    Science.gov (United States)

    Tokuyama, Michio

    2017-01-01

    The renormalized simplified model is proposed to investigate indirectly how the static structure factor plays an important role in renormalizing a quadratic nonlinear term in the ideal mode-coupling memory function near the glass transition. The renormalized simplified recursion equation is then derived based on the time-convolutionless mode-coupling theory (TMCT) proposed recently by the present author. This phenomenological approach is successfully applied to check from a unified point of view how strong liquids are different from fragile liquids. The simulation results for those two types of liquids are analyzed consistently by the numerical solutions of the recursion equation. Then, the control parameter dependence of the renormalized nonlinear exponent in both types of liquids is fully investigated. Thus, it is shown that there exists a novel difference between the universal behavior in strong liquids and that in fragile liquids not only for their transport coefficients but also for their dynamics.

  3. Comparative study of bulk metallic glass composites with high-volume-fractioned dendritic and spherical b. c. c. phase precipitates

    Directory of Open Access Journals (Sweden)

    Guo-yuan Sun

    2015-05-01

    Full Text Available A dendritic β-phase reinforced bulk metallic glass (BMG composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction (XRD, scanning electron microscopy (SEM observation and room-temperature compression test. The microstructure and mechanical properties were compared with those of the spherical β-phase reinforced composite named as composite S2. It was found that the composite D2 contains β-phase dendrites up to 56% in volume-fraction, and exhibits a ductile compressive behavior with plastic strain of 12.7%. As the high-volume-fractioned β-phase dendrites transferred to coarse spherical particles of about 20 μm in diameter in the composite S2, a much improved plastic strain up to 20.4% can be achieved. Micrographs of the fractured samples reveal different interaction modes of the propagating shear bands with the dendritic and spherical β phase inclusions, resulting in different shear strains in the composite samples. The matrix of composite S2 undergoes a significantly larger shear strain than that of the composite D2 before ultimate failure, which is thought to be mainly responsible for the greatly increased global plastic strain of the S2 relative to D2.

  4. Hilbert-Glass Transition: New Universality of Temperature-Tuned Many-Body Dynamical Quantum Criticality

    Directory of Open Access Journals (Sweden)

    David Pekker

    2014-03-01

    Full Text Available We study a new class of unconventional critical phenomena that is characterized by singularities only in dynamical quantities and has no thermodynamic signatures. One example of such a transition is the recently proposed many-body localization-delocalization transition, in which transport coefficients vanish at a critical temperature with no singularities in thermodynamic observables. Describing this purely dynamical quantum criticality is technically challenging as understanding the finite-temperature dynamics necessarily requires averaging over a large number of matrix elements between many-body eigenstates. Here, we develop a real-space renormalization group method for excited states that allows us to overcome this challenge in a large class of models. We characterize a specific example: the 1 D disordered transverse-field Ising model with generic interactions. While thermodynamic phase transitions are generally forbidden in this model, using the real-space renormalization group method for excited states we find a finite-temperature dynamical transition between two localized phases. The transition is characterized by nonanalyticities in the low-frequency heat conductivity and in the long-time (dynamic spin correlation function. The latter is a consequence of an up-down spin symmetry that results in the appearance of an Edwards-Anderson-like order parameter in one of the localized phases.

  5. 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.

    2013-08-01

    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 Tg is covered. We focus on low-Tg 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" Ecoop(T) depending exponentially on temperature [Schmidtke et al., Phys. Rev. E 86, 041507 (2012)], 10.1103/PhysRevE.86.041507. 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 Ecoop(T)/E∞ vs. T/E∞ plot and suggests that E∞ controls the energy scale of the glass transition phenomenon.

  6. Glass transition and dynamics in BSA-water mixtures over wide ranges of composition studied by thermal and dielectric techniques.

    Science.gov (United States)

    Panagopoulou, A; Kyritsis, A; Sabater I Serra, R; Gómez Ribelles, J L; Shinyashiki, N; Pissis, P

    2011-12-01

    Protein-water dynamics in mixtures of water and a globular protein, bovine serum albumin (BSA), was studied over wide ranges of composition, in the form of solutions or hydrated solid pellets, by differential scanning calorimetry (DSC), thermally stimulated depolarization current technique (TSDC) and dielectric relaxation spectroscopy (DRS). Additionally, water equilibrium sorption isotherm (ESI) measurements were performed at room temperature. The crystallization and melting events were studied by DSC and the amount of uncrystallized water was calculated by the enthalpy of melting during heating. The glass transition of the system was detected by DSC for water contents higher than the critical water content corresponding to the formation of the first sorption layer of water molecules directly bound to primary hydration sites, namely 0.073 (grams of water per grams of dry protein), estimated by ESI. A strong plasticization of the T(g) was observed by DSC for hydration levels lower than those necessary for crystallization of water during cooling, i.e. lower than about 0.3 (grams of water per grams of hydrated protein) followed by a stabilization of T(g) at about -80°C for higher water contents. The α relaxation associated with the glass transition was also observed in dielectric measurements. In TSDC a microphase separation could be detected resulting in double T(g) for some hydration levels. A dielectric relaxation of small polar groups of the protein plasticized by water, overlapped by relaxations of uncrystallized water molecules, and a separate relaxation of water in the crystallized water phase (bulk ice crystals) were also recorded.

  7. Composition-driven spin glass to ferromagnetic transition in the quasicrystal approximant Au-Al-Gd

    Science.gov (United States)

    Ishikawa, A.; Hiroto, T.; Tokiwa, K.; Fujii, T.; Tamura, R.

    2016-01-01

    We investigated the composition dependence of the magnetic susceptibility of the quasicrystal approximant Au-Al-Gd. A composition-driven ferromagnetic transition is observed in a quasicrystal approximant, which is attributed to the Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillation via a variation in the Fermi wave vector. The ferromagnetic transition is most simply understood as a result of the close matching of the nearest and second-nearest spin distances with the maximum positions of the RKKY potential. The present work provides an idea that allows us to tailor the magnetic order via the electron concentration in quasicrystal approximants as well as in quasicrystals.

  8. PAL signature of physical ageing in chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ingram, Adam; Kozdras, Andrzej [Physics Faculty of Opole University of Technology, 75, Ozimska Str., Opole 45370 (Poland); Shpotyuk, Oleh [Institute of Physics of Jan Dlugosz University, 13/15, al. Armii Krajowej, Czestochowa 42201 (Poland); Golovchak, Roman [Physics Faculty of Opole University of Technology, 75, Ozimska Str., Opole 45370 (Poland); Lviv Scientific Research Institute of Materials of SRC ' ' Carat' ' , 202, Stryjska Str., Lviv 79031 (Ukraine)

    2012-05-15

    Kinetics of physical ageing (PhA) far below the glass transition temperature (T{sub g}) is studied by positron annihilation lifetime and differential scanning calorimetry techniques for vitreous As{sub 20}Se{sub 80} as typical representative of network glasses. The increased density fluctuations are shown to be responsible for the initial stage of PhA in this glass at below-T{sub g} temperatures. These fluctuations are correlated with changes in thermodynamic parameters of structural relaxation through the glass-to-supercooled liquid transition interval. General shrinkage, occurred during the next stage of PhA, is shown to be determined by the ability of system to release these redundant open volumes from the glass bulk through densification process of glass network. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Solidification of a colloidal hard sphere like model system approaching and crossing the glass transition.

    Science.gov (United States)

    Franke, Markus; Golde, Sebastian; Schöpe, Hans Joachim

    2014-08-07

    We investigated the process of vitrification and crystallization in a model system of colloidal hard spheres. The kinetics of the solidification process was measured using time resolved static light scattering, while the time evolution of the dynamic properties was determined using time resolved dynamic light scattering. By performing further analysis we confirm that solidification of hard sphere colloids is mediated by precursors. Analyzing the dynamic properties we can show that the long time dynamics and thus the shear rigidity of the metastable melt is highly correlated with the number density of solid clusters (precursors) nucleated. In crystallization these objects convert into highly ordered crystals whereas in the case of vitrification this conversion is blocked and the system is (temporarily) locked in the metastable precursor state. From the early stages of solidification one cannot clearly conclude whether the melt will crystallize or vitrify. Furthermore our data suggests that colloidal hard sphere glasses can crystallize via homogeneous nucleation.

  10. Physical Aging of Thin and Ultrathin Free-Standing Polymer Films: Effect of Stress and Reduced Glass Transitions

    Science.gov (United States)

    Pye, Justin; Roth, Connie

    2014-03-01

    While great effort has been made in elucidating the effect of confinement on the glass transition (Tg) in polymers, considerably less work has been done on physical aging. Starting with supported films, we have previously shown that the reduced physical aging rates in ultrathin polystyrene (PS) films can be linked to the reduced Tg near the free surface [Macromolecules 2010, 43, 8296]. We then showed that high molecular weight (MW) free-standing PS films have two reduced Tgs suggesting that two separate mechanisms are acting simultaneously to propagate enhanced mobility at the free surface deeper into the film [PRL 2011, 107, 235701]. To help determine the mechanisms of these two reduced Tgs, we performed physical aging measurements on these high MW free-standing PS films. For thick films (220-1800 nm) in which there are no Tg reductions, we find that the physical aging rate depends strongly on stress caused by thermal expansion mismatch between film and support. This stress, applied to the films as they are quenched into the glassy state, can nearly double the physical aging rate when changing the frame material from polycarbonate to silicon [Macromolecules 2013, DOI:10.1021/ma401872u]. Finally, ultrathin high MW PS films held at a temperature between the two Tgs do exhibit physical aging, indicating that at least some of the film is glassy between these two transitions.

  11. Effects of mechanical stress on the volume phase transition of poly(N-isopropylacrylamide) based polymer gels

    Science.gov (United States)

    Takigawa, T.; Araki, H.; Takahashi, K.; Masuda, T.

    2000-11-01

    The effects of mechanical stress on the volume phase transition of a poly(N-isopropylacrylamide) (PNIPA) gel as well as a copolymer gel composed of N-isopropylacrylamide (NIPA) and sodium acrylate (SA) were investigated in the relatively low stress region. The PNIPA gel without elongational stress showed the behavior close to the second order phase transition. The character of the first order transition became clear under tension, and the transition temperature increased with increasing applied stress. Similar behavior was observed for the NIPA-SA copolymer gel, but the copolymer gel showed the first order transition in the whole stress range investigated. The thermodynamical linear region, where the transition temperature varies linearly with applied stress, was narrower than the mechanical linear region determined by the stress-strain relation of the gels. The change in the transition behavior by the application of the mechanical stress originated chiefly from the volume change in the gels by the applied mechanical stress. It was found that the curve of the transition temperature against applied stress corresponds to the phase boundary between the swollen and collapsed phases for the gels. On the basis of the experimental data, a phenomenological model describing the volume phase transition of the polymer gels is proposed in the frame of the Landau-type free energy expression.

  12. Molecular dynamics simulations to calculate glass transition temperature and elastic constants of novel polyethers.

    Science.gov (United States)

    Sarangapani, Radhakrishnan; Reddy, Sreekantha T; Sikder, Arun K

    2015-04-01

    Molecular dynamics simulations studies are carried out on hydroxyl terminated polyethers that are useful in energetic polymeric binder applications. Energetic polymers derived from oxetanes with heterocyclic side chains with different energetic substituents are designed and simulated under the ensembles of constant particle number, pressure, temperature (NPT) and constant particle number, volume, temperature (NVT). Specific volume of different amorphous polymeric models is predicted using NPT-MD simulations as a function of temperature. Plots of specific volume versus temperature exhibited a characteristic change in slope when amorphous systems change from glassy to rubbery state. Several material properties such as Young's, shear, and bulk modulus, Poisson's ratio, etc. are predicted from equilibrated structures and established the structure-property relations among designed polymers. Energetic performance parameters of these polymers are calculated and results reveal that the performance of the designed polymers is comparable to the benchmark energetic polymers like polyNIMMO, polyAMMO and polyBAMO. Overall, it is worthy remark that this molecular simulations study on novel energetic polyethers provides a good guidance on mastering the design principles and allows us to design novel polymers of tailored properties.

  13. Property/composition relationships for Hanford high-level waste glasses melting at 1150{degrees}C volume 2: Chapters 12-16 and appendices A-K

    Energy Technology Data Exchange (ETDEWEB)

    Hrma, P.R.; Piepel, G.F.

    1994-12-01

    A Composition Variation Study (CVS) is being performed within the Pacific Northwest Laboratory Vitrification Technology Development (PVTD) project in support of a future high-level nuclear waste vitrification plant at the Hanford site in Washington. From 1989 to 1994, over 120 nonradioactive glasses were melted and properties measured in five statistically-designed experimental phases. Glass composition is represented by the 10 components SiO{sub 2}, B{sub 2}O{sub 3}, ZrO{sub 2}, Na{sub 2}O, Li{sub 2}O, CaO, MgO, and Others (all remaining components). The properties measured include viscosity ({eta}), electrical conductivity ({epsilon}), glass transition temperature (T{sub g}), thermal expansion of solid glass ({alpha}{sub s}) and molten glass ({alpha}{sub m}), crystallinity (quenched and canister centerline cooled glasses), liquidus temperature (T{sub L}), durability based on normalized elemental releases from the Materials Characterization Center-1 28-day dissolution test (MCC-1, r{sub mi}) and the 7-day Product Consistency Test (PCT, r{sub pi}), and solution pHs from MCC-1 and PCT. Amorphous phase separation was also evaluated. Empirical first- and second-order mixture models were fit using the CVS data to relate the various properties to glass composition. Equations for calculating the uncertainty associated with property values predicted by the models were also developed. The models were validated using both internal and external data. Other modeling approaches (e.g., non-bridging oxygen, free energy of hydration, phase-equilibria T{sub L}) were investigated for specific properties. A preliminary Qualified Composition Region was developed to identify glass compositions with high confidence of being processable in a melter and meeting waste form acceptance criteria.

  14. Property/composition relationships for Hanford high-level waste glasses melting at 115{degrees}C volume 1: Chapters 1-11

    Energy Technology Data Exchange (ETDEWEB)

    Hrma, P.R.; Piepel, G.F.

    1994-12-01

    A Composition Variation study (CVS) is being performed within the Pacific Northwest Laboratory Vitrification Technology Development (PVTD) project in support of a future high-level nuclear waste vitrification plant at the Hanford site in Washington. From 1989 to 1994, over 120 nonradioactive glasses were melted and properties measured in five statistically-designed experimental phases. Glass composition is represented by the 10 components SiO{sub 2}, B{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}, ZrO{sub 2}, Na{sub 2}O, Li{sub 2}O, CaO, MgO, and Others (all remaining components). The properties measured include viscosity ({eta}), electrical conductivity ({epsilon}), glass transition temperature (T{sub g} ), thermal expansion of solid glass ({alpha}{sub s}) and molten glass ({alpha}{sub m}), crystallinity (quenched and canister centerline cooled glasses), liquidus temperature (T{sub L}), durability based on normalized elemental releases from the Materials Characterization Center-1 28-day dissolution test (MCC-1, r{sub mi}) and the 7-day Product Consistency Test (PCT, r{sub pi}), and solution pHs from MCC-1 and PCT. Amorphous phase separation was also evaluated. Empirical first- and second-order mixture models were fit using the CVS data to relate the various properties to glass composition. Equations for calculating the uncertainty associated with property values predicted by the models were also developed. The models were validated using both internal and external data. Other modeling approaches (e.g., non-bridging oxygen, free energy of hydration, phase-equilibria T{sub L}) were investigated for specific properties. A preliminary Qualified Composition Region was developed to identify glass compositions with high confidence of being processable in a melter and meeting waste form acceptance criteria.

  15. An investigation of iron phosphate glasses

    Science.gov (United States)

    Fang, Xiangyu

    The effect of melting history on the iron redox equilibrium, structure, crystallization and properties of a binary iron phosphate glass with a 40Fe 2O3-60P2O5, mol%, batch composition were investigated. The structure and properties of single and mixed alkali iron phosphate glasses were also studied. Mossbauer, Raman and infrared spectroscopy were used to determine the changes in the concentration of iron ions and phosphate units in the structure. Differential thermal analysis, X-ray diffraction and thermogravimetric analysis were used to investigate crystallization. Density, molar volume, thermal expansion, dc electrical conductivity and dielectric constant and loss tangent were measured. The heat capacity and glass transition behavior of the glasses was also measured by the differential scanning calorimeter method. The effect of the melting temperature is stronger than the melting time on the concentration of Fe2+ ions in iron phosphate glasses. The pyrophosphate network in iron phosphate glasses and their general properties do not change either with melting temperature and time or with adding up to 20 mol% of single and mixed alkali oxides. The dissolution rate (in deionized water) of these glasses is generally very low (˜10-9 g/cm2/min) and nearly independent of the relative concentration of Fe 2+ or Fe3+ ions. The dissolution rate of the iron phosphate glasses containing 20 mol% of single or mixed alkali oxide can be comparable to that of window glass. There is no mixed alkali effect in the iron phosphate glasses. The crystallization tendency indicates that the glass structure becomes closer to that of crystalline Fe3(P2O 7)2 with increasing concentration of Fe2+ ions in the glass. The large fragility parameters indicates that the iron phosphate glasses belong in the category of the fragile glass-forming liquids.

  16. Thermodynamics of Rotating Black Holes and Black Rings: Phase Transitions and Thermodynamic Volume

    Directory of Open Access Journals (Sweden)

    Natacha Altamirano

    2014-03-01

    Full Text Available In this review we summarize, expand, and set in context recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. We specifically consider the thermodynamics of higher-dimensional rotating asymptotically flat and AdS black holes and black rings in a canonical (fixed angular momentum ensemble. We plot the associated thermodynamic potential—the Gibbs free energy—and study its behavior to uncover possible thermodynamic phase transitions in these black hole spacetimes. We show that the multiply-rotating Kerr-AdS black holes exhibit a rich set of interesting thermodynamic phenomena analogous to the “every day thermodynamics” of simple substances, such as reentrant phase transitions of multicomponent liquids, multiple first-order solid/liquid/gas phase transitions, and liquid/gas phase transitions of the van derWaals type. Furthermore, the reentrant phase transitions also occur for multiply-spinning asymptotically flat Myers–Perry black holes. These phenomena do not require a variable cosmological constant, though they are more naturally understood in the context of the extended phase space. The thermodynamic volume, a quantity conjugate to the thermodynamic pressure, is studied for AdS black rings and demonstrated to satisfy the reverse isoperimetric inequality; this provides a first example of calculation confirming the validity of isoperimetric inequality conjecture for a black hole with non-spherical horizon topology. The equation of state P = P(V,T is studied for various black holes both numerically and analytically—in the ultraspinning and slow rotation regimes.

  17. 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.)

  18. Rigidity and soft percolation in the glass transition of an atomistic model of ionic liquid, 1-ethyl-3-methyl imidazolium nitrate, from molecular dynamics simulations—Existence of infinite overlapping networks in a fragile ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Habasaki, Junko, E-mail: habasaki.j.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8502 (Japan); Ngai, K. L. [CNR-IPCF Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, I-56127 Pisa (Italy)

    2015-04-28

    The typical ionic liquid, 1-ethyl-3-methyl imidazolium nitrate (EMIM-NO{sub 3}), was examined by molecular dynamics simulations of an all-atomistic model to show the characteristics of networks of cages and/or bonds in the course of vitrification of this fragile glass-former. The system shows changes of dynamics at two characteristic temperatures, T{sub B} (or T{sub c}) and the glass transition temperature T{sub g}, found in other fragile glass forming liquids [K. L. Ngai and J. Habasaki, J. Chem. Phys. 141, 114502 (2014)]. On decreasing temperature, the number of neighboring cation-anion pairs, N{sub B}, within the first minimum of the pair correlation function, g(r){sub min}, increases. On crossing T{sub B} (>T{sub g}), the system volume and diffusion coefficient both show changes in temperature dependence, and as usual at T{sub g}. The glass transition temperature, T{sub g}, is characterized by the saturation of the total number of “bonds,” N{sub B} and the corresponding decrease in degree of freedom, F = [(3N − 6) − N{sub B}], of the system consisting of N particles. Similar behavior holds for the other ion-ion pairs. Therefore, as an alternative, the dynamics of glass transition can be interpreted conceptually by rigidity percolation. Before saturation occurring at T{sub g}, the number of bonds shows a remarkable change at around T{sub B}. This temperature is associated with the disappearance of the loosely packed coordination polyhedra of anions around cation (or vice versa), related to the loss of geometrical freedom of the polyhedra, f{sub g}, of each coordination polyhedron, which can be defined by f{sub g} = [(3N{sub V} − 6) − N{sub b}]. Here, 3N{sub v} is the degree of freedom of N{sub V} vertices of the polyhedron, and N{sub b} is number of fictive bonds. The packing of polyhedra is characterized by the soft percolation of cages, which allows further changes with decreasing temperature. The power spectrum of displacement of the central ion

  19. Glass and glass-ceramics along the SrTiO3-NaPO3 line

    Directory of Open Access Journals (Sweden)

    Sinouh H.

    2013-09-01

    Full Text Available The xSrTiO3-(1−xNaPO3 (x = 0−0.20 mol% glasses were prepared by the conventional melt-quenching method. The amorphous state of the samples was verified by X-ray diffraction. The glass-ceramic materials were obtained by the well known thermal controlled crystallization process. It is found that several physical properties such as the density, molar volume, and the glass transition temperature depend strongly on the chemical composition. Vickers test on the glasses showed that the micro-hardness increases with the SrTiO3 content. The structural approach of the glasses was realized by IR spectroscopy. This technique has highlighted the co-existence of different phosphate and titanium structural units in the glassy-matrix. Crystallization of the glasses was enhanced by heat treatments and followed by X-ray diffraction. A mechanism for this glass crystallization was proposed.

  20. Evolution of shear bands, free volume, and structure in room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yuanli; Shi, Bo; Ma, Zhikun; Li, Jiangong, E-mail: lijg@lzu.edu.cn

    2015-01-19

    The evolution of the shear band, free volume, and structure in room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass was investigated. It was found that the average shear band density increases monotonously with increasing strain. For the room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass with a strain of 99%, a high density of shear bands with an average spacing of 31 nm was observed. The absolute free volume content was determined based on the free volume model and found to increase monotonously with increasing strain. The free volume content in the room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass with a strain of 99% is 34% higher than its as-cast counterpart. Neither phase separation nor crystallization occurs in all the deformed samples. The coordination number of the first coordination shell decreases and the degree of disorder of atomic arrangement increases with increasing strain.

  1. Effects of glass surface area-to-solution volume ratio (S/V) on glass dissolution. Part one: Relationship between S/V and leachate pH

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X. [Argonne National Lab., IL (United States). Chemical Technology Div.; Pegg, I.L. [Catholic Univ. of America, Washington, DC (United States)

    1992-11-01

    The observed relationship between S/V and leachate pH is discussed in terms of a simple model of the glass dissolution process. Data from leach tests on several nuclear waste glass compositions at different S/V ratios show that the leachate pH increases with time and then stabilizes at a nearly constant value beyond about 28 days. This stabilized pH increases systematically with the S/V ratio of the test. The model developed here reproduces the essential features of the data and suggests that a single parameter describing the intrinsic rate of alkali diffusion and ion exchange from the glass is sufficient to represent the major glass composition dependence. Interestingly, the results are essentially independent of the rate constant for matrix dissolution. This study suggests that the diffusion-ion exchange process is central in determining the solution pH and its dependence on S/V and the glass reaction, at least under static or low-flow-rate test conditions, is driven by alkali release.

  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

    Poly(lactic acid) (PLA) is a bio-based and compostable thermoplastic polyester that has rapidly evolved into a competitive commodity material over the last decade. One key bottleneck in expanding the field of application of PLA is the control of its structure and properties. Therefore, in situ...... by differential scanning calorimetry (DSC). The obtained results showed that the deformation and yield stress of glassy PLA are strongly dependent on the stretching temperatures together with the transition from mesophase to mesocrystal and the formation of cavities. With the increase in drawing temperature...

  3. Camera on Vessel: A Camera-Based System to Measure Change in Water Volume in a Drinking Glass

    Directory of Open Access Journals (Sweden)

    Idowu Ayoola

    2015-09-01

    Full Text Available A major problem related to chronic health is patients’ “compliance” with new lifestyle changes, medical prescriptions, recommendations, or restrictions. Heart-failure and hemodialysis patients are usually placed on fluid restrictions due to their hemodynamic status. A holistic approach to managing fluid imbalance will incorporate the monitoring of salt-water intake, body-fluid retention, and fluid excretion in order to provide effective intervention at an early stage. Such an approach creates a need to develop a smart device that can monitor the drinking activities of the patient. This paper employs an empirical approach to infer the real water level in a conically shapped glass and the volume difference due to changes in water level. The method uses a low-resolution miniaturized camera to obtain images using an Arduino microcontroller. The images are processed in MATLAB. Conventional segmentation techniques (such as a Sobel filter to obtain a binary image are applied to extract the level gradient, and an ellipsoidal fitting helps to estimate the size of the cup. The fitting (using least-squares criterion between derived measurements in pixel and the real measurements shows a low covariance between the estimated measurement and the mean. The correlation between the estimated results to ground truth produced a variation of 3% from the mean.

  4. 铁基块体非晶合金玻璃形成能力与特征自由体积的关系%CORRELATION BETWEEN THE GLASS-FORMING ABILITY AND CHARACTERISTIC FREE VOLUMES OF THE IRON BASE BULK METALLIC GLASSES

    Institute of Scientific and Technical Information of China (English)

    胡强; 曾燮榕; 钱海霞; 谢胜辉; 盛洪超

    2012-01-01

    Many researches have demonstrated that the free volume have a great effect on the properties of bulk metallic glasses (BMGs). For different BMGs, however, quantitative measurement of free volumes and analysis of properties of BMGs using the measurement results are still difficult. In this work, the two types of characteristic free volumes, the free volume released in structural relaxation, △Vf-sr and the free volume generated in glass transition, △Vf_gt are given from the △(dV(T)/V0) curve, where the △(dV(T)/V0) is the thermal expansion difference between amorphous and crystalline samples measured by a cyclic thermal dilation test. In a series of Fe-(Er)-Cr-Mo-C-B BMGs, it is found that the BMG with the largest critical diameter (Dc) has also the largest △Vf_gt, and Dc increases sensitively with the decrease of △Vf-sr. More impressively, D2c or Dc can be fitted with high regression coefficient of 0.998 by a negative exponential function of △Vf-sr- Hence, the characteristic free volume has a sensitive and close correlation with the glass forming ability of BMGs.%运用循环热膨胀法获得了块体非晶合金与其晶态合金的体膨胀差曲线△(dV(T)/Vo),由此定义出块体非晶合金的2个特征自由体积,即结构弛豫中释放出的自由体积△Vf-sr和玻璃转变中生成的自由体积△Vf-gt.Fe-(Er)-Cr-Mo-C-B系列块体非晶合金的实验结果表明:非晶合金的玻璃形成能力与其特征自由体积关系密切,临界尺寸Dc最大的非晶合金的△Vf-gt也最大;且Dc随△Vf-sr变化趋势明显,D2c或Dc可以拟合成△Vf-sr的负指数函数,回归系数高达0.998.

  5. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    Science.gov (United States)

    Madathingal, Rajesh Raman

    hydrogen bonded to the silanols, and was independent of particle morphology. For methylated silica, (CH3) 3-SiO2, the adsorption isotherms were identical for colloidal and fumed silica, but Tg was depressed for the former, and comparable to the bulk value for the latter. The increased Tg of PMMA adsorbed onto fumed (CH3)3-SiO2 was attributed to the larger loops formed by the bridging PMMA chains between the silica aggregates. For nanocomposites the interphase region becomes more important as the surface/volume ratio of the nanoparticles increases. Polymers have chain dimensions (characterized by the radius of gyration, Rg) similar to the nanoparticles (Rnanoparticle) themselves, so that chain conformation, mobility and crystallinity can be affected by Rg/Rnanoparticle. Here, both the glass transition temperature (Tg) and degree of crystallinity (Xc) of polyethylene oxide (PEO) on individual SiO 2 nanoparticles of nominal 15, 50 and 100 nm diameter (2 RSiO2 ) , in which Rg (PEO) was greater, equal to or less than RSiO2 was investigated. Plateau adsorption of PEO on SiO2 nanoparticles (PEO-SiO2) increased in the order PEO-SiO 2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm). At plateau adsorption after melting and solidification, the samples were completely amorphous. The Tg of the adsorbed PEO increased in the order PEO-SiO 2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm); since the Tgs were above 25°C in all cases, the PEO behaved more like a brittle solid than an elastomer. For comparable amounts of PEO that were adsorbed from solution but not melted, the melt endotherm increased in the order PEO-SiO2 (15 nm) > PEO-SiO2 (50 nm) > PEO-SiO 2 (100 nm). These trends were interpreted as due to an increase in loop/tail lengths and thus flexibility, with a concomitant ability to crystallize, as Rg (PEO)/RSiO2 decreased and which was the result of less hydrogen bond formation between the oxygens of PEO and the silanols (SiOH) of the SiO 2 as the nanoparticle size decreased. This

  6. 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.

  7. 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.

  8. Influence of microwave vacuum drying on glass transition temperature, gelatinization temperature, physical and chemical qualities of lotus seeds.

    Science.gov (United States)

    Zhao, Yingting; Jiang, Yajun; Zheng, Baodong; Zhuang, Weijing; Zheng, Yafeng; Tian, Yuting

    2017-08-01

    This study investigated the effects of microwave power density on effective moisture diffusion coefficient (Deff), glass transition temperature (Tg), gelatinization temperature (TP), physical and chemical qualities of lotus seeds during microwave vacuum drying. Deff increased by 42% and 127% at 15W/g and 20W/g, respectively, when compared with 10W/g. TP was negatively correlated with the relaxation times of T21 and T22, while Tg was negatively correlated with the relative areas A22. The rates of change of color were observed to be divided roughly into two periods, consisting of a rapid change caused by enzymatic browning and a slow change caused by non-enzymatic browning. An equation is provided to illustrate the relationship of k1 and k2 of Peleg's model depending on power density during rehydration kinetics. The samples at 20W/g exhibited the higher content of amino acid (540.19mg/100gd.b.) while lower starch (17.53g/100gd.b.).

  9. Dramatic slowing of compositional relaxations in the approach to the glass transition for a bimodal colloidal suspension

    Science.gov (United States)

    Hannam, S. D. W.; Daivis, P. J.; Bryant, G.

    2017-08-01

    Molecular dynamics simulation was used to study a model colloidal suspension with two species of slightly different sized colloidal particles in an explicit solvent. In this work we calculated the four interdiffusion coefficients for the ternary system, which were then used to calculate the decay coefficients D± of the two independent diffusive modes. We found that the slower D- decay mode, which is associated with the system's ability to undergo compositional changes, was responsible for the long-time decay in the intermediate scattering function. We also found that a decrease in D- to negligible values at a packing fraction of Φg=0.592 resulted in an extreme slow-down in the long-time decay of the intermediate scattering function often associated with the glass transition. Above Φg, the system formed a long-lived metastable state that did not relax to its equilibrium crystal state within the simulation time window. We concluded that the inhibition of crystallization was caused by the inability of the quenched fluid to undergo the compositional changes needed for the formation of the equilibrium crystal.

  10. Glass transition with decreasing correlation length during cooling of Fe50Co50 superlattice and strong liquids

    CERN Document Server

    Wei, Shuai; Busch, Ralf; Angell, C Austen

    2010-01-01

    The glass transition GT is usually thought of as a structural arrest that occurs during the cooling of a liquid, or sometimes a plastic crystal, trapping a metastable state of the system before it can recrystallize to stabler forms1. This phenomenon occurs in liquids of all classes, most recently in bulk metallic glassformers2. Much theoretical interest has been generated by the dynamical heterogeneity observed in cooling of fragile liquids3, 4, and many have suggested that the slow-down is caused by a related increasing correlation length 5-9. Here we report both kinetics and thermodynamics of arrest in a system that disorders while in its ground state, exhibits a large !Cp on arrest (!Cp = Cp,mobile - Cp,arrested), yet clearly is characterized by a correlation length that is decreasing as GT is approached from above. We show that GT kinetics in our system, the disordering superlattice Fe50Co50, satisfy the kinetic criterion for ideally 'strong' glassformers10, and since !Cp behavior through Tg also correlat...

  11. Influence of compression on water sorption, glass transition, and enthalpy relaxation behavior of freeze-dried amorphous sugar matrices.

    Science.gov (United States)

    Imamura, Koreyoshi; Kagotani, Ryo; Nomura, Mayo; Tanaka, Kazuhiro; Kinugawa, Kohshi; Nakanishi, Kazuhiro

    2011-04-15

    An amorphous matrix comprised of sugar molecules are frequently used in the pharmaceutical industry. The compression of the amorphous sugar matrix improves the handling. Herein, the influence of compression on the water sorption of an amorphous sugar matrix was investigated. Amorphous sugar samples were prepared by freeze-drying, using several types of sugars, and compressed at 0-443 MPa. The compressed amorphous sugar samples as well as uncompressed samples were rehumidified at given RHs, and the equilibrium water content and glass transition temperature (T(g)) were then measured. Compression resulted in a decrease in the equilibrium water content of the matrix, the magnitude of which was more significant for smaller sized sugars. Diffusivity of water vapor in the sample was also decreased to one-hundredth by the compression. The T(g) value for a given RH remained unchanged, irrespective of the compression. Accordingly, the decrease in T(g) with increasing water content increased as the result of compression. The structural relaxation of the amorphous sugar matrices were also examined and found to be accelerated to the level of a non-porous amorphous sugar matrix as the result of the compression. The findings indicate that pores contained in freeze-dried sugar samples interfere with the propagation of structural relaxation.

  12. The glass transition and sub-T(g)-relaxation in pharmaceutical powders and dried proteins by thermally stimulated current.

    Science.gov (United States)

    Reddy, Renuka; Chang, Liuquan ' Lucy '; Luthra, Suman; Collins, George; Lopez, Ciro; Shamblin, Sheri L; Pikal, Michael J; Gatlin, Larry A; Shalaev, Evgenyi Y

    2009-01-01

    The main goal of the study was to evaluate the applicability of thermally stimulated current (TSC) as a measure of molecular mobility in dried globular proteins. Three proteins, porcine somatotropin, bovine serum albumin, and immunoglobulin, as well as materials with a strong calorimetric glass transition (T(g)), that is, indomethacin and poly(vinypyrrolidone) (PVP), were studied by both TSC and differential scanning calorimetry (DSC). Protein/sugar colyophilized mixtures were also studied by DSC, to estimate calorimetric T(g) for proteins using extrapolation procedure. In the majority of cases, TSC detected relaxation events that were not observed by DSC. For example, a sub-T(g) TSC event (beta-relaxation) was observed for PVP at approximately 120 degrees C, which was not detected by the DSC. Similarly, DSC did not detect events in any of the three proteins below the thermal denaturation temperature whereas a dipole relaxation was detected by TSC in the range of 90-140 degrees C depending on the protein studied. The TSC signal in proteins was tentatively assigned as localized mobility of protein segments, which is different from a large-scale cooperative motions usually associated with calorimetric T(g). TSC is a promising method to study the molecular mobility in proteins and other materials with weak calorimetric T(g). (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

  13. QSPR Analysis of Copolymers by Recursive Neural Networks: Prediction of the Glass Transition Temperature of (Meth)acrylic Random Copolymers.

    Science.gov (United States)

    Bertinetto, Carlo Giuseppe; Duce, Celia; Micheli, Alessio; Solaro, Roberto; Tiné, Maria Rosaria

    2010-09-17

    The glass transition temperature (Tg ) of acrylic and methacrylic random copolymers was investigated by means of Quantitative Structure-Property Relationship (QSPR) methodology based on Recursive Neural Networks (RNN). This method can directly take molecular structures as input, in the form of labelled trees, without needing predefined descriptors. It was applied to three data sets containing up to 615 polymers (340 homopolymers and 275 copolymers). The adopted representation was able to account for the structure of the repeating unit as well as average macromolecular characteristics, such as stereoregularity and molar composition. The best result, obtained on a data set focused on copolymers, showed a Mean Average Residual (MAR) of 4.9 K, a standard error of prediction (S) of 6.1 K and a squared correlation coefficient (R(2) ) of 0.98 for the test set, with an optimal rate with respect to the training error. Through the treatment of homopolymers and copolymers both as separated and merged data sets, we also showed that the proposed approach is particularly suited for generalizing prediction of polymer properties to various types of chemical structures in a uniform setting.

  14. Sorption isotherms, thermodynamic properties and glass transition temperature of mucilage extracted from chia seeds (Salvia hispanica L.).

    Science.gov (United States)

    Velázquez-Gutiérrez, Sandra Karina; Figueira, Ana Cristina; Rodríguez-Huezo, María Eva; Román-Guerrero, Angélica; Carrillo-Navas, Hector; Pérez-Alonso, César

    2015-05-05

    Freeze-dried chia mucilage adsorption isotherms were determined at 25, 35 and 40°C and fitted with the Guggenheim-Anderson-de Boer model. The integral thermodynamic properties (enthalpy and entropy) were estimated with the Clausius-Clapeyron equation. Pore radius of the mucilage, calculated with the Kelvin equation, varied from 0.87 to 6.44 nm in the temperature range studied. The point of maximum stability (minimum integral entropy) ranged between 7.56 and 7.63kg H2O per 100 kg of dry solids (d.s.) (water activity of 0.34-0.53). Enthalpy-entropy compensation for the mucilage showed two isokinetic temperatures: (i) one occurring at low moisture contents (0-7.56 kg H2O per 100 kg d.s.), controlled by changes in water entropy; and (ii) another happening in the moisture interval of 7.56-24 kg H2O per 100 kg d.s. and was enthalpy driven. The glass transition temperature Tg of the mucilage fluctuated between 42.93 and 57.93°C.

  15. 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%TeO 2 + 5%Fe 2O 3 + 10%TMO], where transition metal oxides (TMO) are TiO 2, V 2O 5, 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 TeO 44- triagonal bipyramid ( C2v) and Te 2O 76- 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 (TeO 3+1 binds to TeO 3 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).

  16. 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.

  17. 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.

  18. Molecular weight dependence of surface flow near the bulk glass transition temperature

    Science.gov (United States)

    Chai, Yu; Salez, Thomas; Benzaquen, Michael; Raphael, Elie; Forrest, James A.

    2014-03-01

    We present the study on molecular weight dependent sub-Tg surface dynamics of polymer thin films by using the Nano-step experiment [McGraw et al. Soft Matter 7, 7832 (2011)]. By varying the molecular weight, we are able to probe the surface dynamics of the free surface below Tg with the polymer size comparable to the surface depth. In particular, we define and use a correlation function to compare measured and calculated profiles to analyze the transition from the bulk flow to flow restricted to the surface region. Surprisingly, even for the polymers with Mw = 22,000 surface flow is still observed below the bulk Tg value. A numerical simulation of random walk is used to find the fraction of polymer of which all of the polymer segments are located in the free surface region. The simulation results indicate that there are still a significant fraction of polymer molecules where all segments are in the near free surface region. These molecules can undergo flow consistent with the experimental results.

  19. Structure-property-glass transition relationships in non-isocyanate polyurethanes investigated by dynamic nanoindentation

    Science.gov (United States)

    Weyand, Stephan; Blattmann, Hannes; Schimpf, Vitalij; Mülhaupt, Rolf; Schwaiger, Ruth

    2016-07-01

    Newly developed green-chemistry approaches towards the synthesis of non-isocyanate polyurethane (NIPU) systems represent a promising alternative to polyurethanes (PU) eliminating the need for harmful ingredients. A series of NIPU systems were studied using different nanoindentation techniques in order to understand the influence of molecular parameters on the mechanical behavior. Nanoindentation revealed a unique characteristic feature of those materials, i.e. stiffening with increasing deformation. It is argued that the origin of this observed stiffening is a consequence of the thermodynamic state of the polymer network, the molecular characteristics of the chemical building blocks and resulting anisotropic elastic response of the network structure. Flat-punch nanoindentation was applied in order to characterize the constitutive viscoelastic nature of the materials. The complex modulus shows distinct changes as a function of the NIPU network topology illustrating the influence of the chemical building blocks. The reproducibility of the data indicates that the materials are homogeneous over the volumes sampled by nanoindentation. Our study demonstrates that nanoindentation is very well-suited to investigate the molecular characteristics of NIPU materials that cannot be quantified in conventional experiments. Moreover, the technique provides insight into the functional significance of complex molecular architectures thereby supporting the development of NIPU materials with tailored properties.

  20. 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)

  1. Correlation of transrectal and transabodominal ultrasound measurement of transition zone volume with post-operative enucleated adenoma volume in benign prostatic hypertrophy.

    Science.gov (United States)

    Ajayi, Idowu; Aremu, Ademola; Olajide, Abimbola; Bello, Tope; Olajide, Folake; Adetiloye, Victor

    2013-01-01

    Benign prostatic hyperplasia is a common disease of ageing men worldwide. Though transrectal ultrasonography (TRUS) is the standard in most parts of the world in evaluation of benign prostatic hyperplasia (BPH), it is rarely done in some less developed countries because of non availability of appropriate probes and or specialists. Transabdominal ultrasonography (TAUS) remains the mainstay in these areas. Some controversies still exist in literature about the accuracy of TAUS evaluation of prostatic volume in patients with BPH. This study aimed at comparing the transition zone volume estimation of the prostate on transrectal and transabdominal ultrasound with post-operative enucleated adenoma volume in Nigeria patients with BPH and to suggest better predictor of prostate volume in evaluation of BPH. Forty-six (46) patients with lower urinary tract symptoms due to BPH attending the urologic clinic were evaluated ultrasonographically and eventually managed with open surgery (prostatectomy) after due counselling. The post operative samples were weighted using a sensitive top loading weighing balance and converted to volume. Since the specific gravity of the prostate is equivalent to that of water,the weight is the same as volume. Patients' ages ranged between 59 and 90 years with a peak age incidence at seventh decade. Transition Zone (TZ) volume estimation on both transrectal and transabdominal ultrasound showed positive correlation with the post operative enucleated adenoma(r = 0.594, p < 0.001) but the transrectal method was more accurate. There was no significant relationship between the TZ volume and patients' symptoms(r = 0.491, p = 0.007). Both TRUS and TAUS are comparable at TZ volume estimation and therefore TAUS can be utilized in regions where intracavitary probes and or the expertise is/are not available.

  2. Molecular mobility with respect to accessible volume in Monte Carlo lattice model for polymers

    Science.gov (United States)

    Diani, J.; Gilormini, P.

    2017-02-01

    A three-dimensional cubic Monte Carlo lattice model is considered to test the impact of volume on the molecular mobility of amorphous polymers. Assuming classic polymer chain dynamics, the concept of locked volume limiting the accessible volume around the polymer chains is introduced. The polymer mobility is assessed by its ability to explore the entire lattice thanks to reptation motions. When recording the polymer mobility with respect to the lattice accessible volume, a sharp mobility transition is observed as witnessed during glass transition. The model ability to reproduce known actual trends in terms of glass transition with respect to material parameters, is also tested.

  3. Ion- and pH-dependent volume transitions in biopolymer gels

    Science.gov (United States)

    Horkay, Ference

    2008-03-01

    Swelling and collapse of polyelectrolyte gels are the result of a balance of different interactions that control the osmotic pressure and network elasticity. In biopolymer systems ions often play a central role in determining the phase behavior. For example, DNA condensation induced by multivalent cations is crucial for its packaging. It is known that biological processes, such as nerve excitation and muscle contraction, are mediated by divalent cations. In general, relatively little is known about the interaction between multivalent ions and charged biopolymers due to the lack of an appropriate theory and the absence of a sufficiently broad base of experimental data. Recent experimental observations made by anomalous small-angle X-ray scattering indicate that the spatial extent of the counterion cloud is significantly reduced in the case of divalent ions relative to the monovalent ions. An understanding of ion induced swelling/collapse transition in polyelectrolyte gels may shed light on the mechanism of important physiological processes. We compare the effects of pH, ionic strength and counterion valence on the structure and osmotic properties of biopolymer gels. Systematic studies made on DNA gels indicate that monovalent salts gradually reduce gel swelling but do not cause discontinuous volume transition. Introducing calcium ions into the gels produces a reversible volume change. Similarly, decreasing the pH in the surrounding environment leads to shrinkage of the swollen networks. Scattering observations reveal that cations mediate the equilibrium properties by modifying the local environment and the organization of the polymer chains. Osmotic pressure measurements detect significant differences between the effects of pH and ion valence.

  4. Mechanical and Barrier Properties of Epoxy/ultra-short Glass Fibers Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    Yongsheng Hao; Fuchun Liu; En-Hou Han

    2012-01-01

    Epoxy coatings containing different volume fractions of ultra-short glass fibers were prepared successfully. Ultra-short glass fiber not only can improve the hardness, adhesion of the coating, and glass transition tem-perature (Tg), but also can decrease the coefficient of thermal expansion (CTE) of the coating. Electrochemical impedance spectroscopy (EIS) was used to evaluate the barrier properties of the coatings containing different volume fractions of ultra-short glass fibers. The EIS results showed that the coating had the best barrier property when it contained 20% (volume fraction) ultra-short glass fibers. The functions of the ultra-short glass fibers in epoxy coating are two fold: first, they can improve the coating mechanical properties as reinforcement materials; second, they parallel to the substrate and inhibit the corrosive medium to pass through the coating.

  5. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with g-Alumina Nanoparticles

    Directory of Open Access Journals (Sweden)

    Sergio Diez-Berart

    2015-06-01

    Full Text Available 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.

  6. When is a single molecule heterogeneous? A multidimensional answer and its application to dynamics near the glass transition

    Science.gov (United States)

    Verma, Sachin Dev; Vanden Bout, David A.; Berg, Mark A.

    2015-07-01

    Even for apparently simple condensed-phase processes, bulk measurements of relaxation often yield nonexponential decays; the rate appears to be dispersed over a range of values. Taking averages over individual molecules is an intuitive way to determine whether heterogeneity is responsible for such rate dispersion. However, this method is in fundamental conflict with ergodic behavior and often yields ambiguous results. This paper proposes a new definition of rate heterogeneity for ergodic systems based on multidimensional time correlation functions. Averages are taken over both time and molecules. Because the data set is not subdivided, the signal-to-noise ratio is improved. Moment-based quantities are introduced to quantify the concept of rate dispersion. As a result, quantitative statements about the fraction of the dispersion due to heterogeneity are possible, and the experimental noise is further averaged. The practicality of this approach is demonstrated on single-molecule, linear-dichroism trajectories for R6G in poly(cyclohexyl acrylate) near its glass transition. Single-molecule averaging of these data does not provide useful conclusions [C. Y. Lu and D. A. Vanden Bout, J. Chem. Phys. 125, 124701 (2006)]. However, full-ensemble, two- and three-dimensional averages of the same data give clear and quantitative results: the rate dispersion is 95% ± 5% due to heterogeneity, and the rate exchange is at least 11 times longer than the mean rotation time and possibly much longer. Based on these results, we suggest that the study of heterogeneous materials should not focus on "ensemble" versus "single-molecule" experiments, but on one-dimensional versus multidimensional measurements.

  7. 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 τα(T) of three glass-forming liquids (salol, o-terphenyl, and α-picoline) were investigated by a depolarized light scattering technique. A detailed description of τα(T) near TA, the temperature of the transition from the Arrhenius law at high temperatures to a non-Arrhenius behavior of τα(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 τα(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), 10.1103/PhysRevE.53.751], 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), 10.1103/PhysRevE.86.041507], where the activation energy includes the term depending exponentially on temperature.

  8. 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.

  9. Linear and nonlinear resistivity of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} ceramics at chiral-glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Deguchi, H., E-mail: deguchi@tobata.isc.kyutech.ac.j [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu (Japan); Hashimoto, Y.; Shoho, T.; Mito, M.; Takagi, S. [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu (Japan); Koyama, K. [Faculty of Integrated Arts and Sciences, University of Tokushima, Tokushima (Japan); Hagiwara, M. [Faculty of Engineering and Design, Kyoto Institute of Technology, Kyoto (Japan)

    2010-12-15

    Ceramic YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} composed of sub-micron size grains has shown successive phase transitions under zero field. The first transition occurs inside each grain at T{sub c1} and the second transition occurs among the grains at T{sub c2} (glass ordering occurs at T{sub c2}.

  10. Optical Properties of Li2B4O7 Glasses Doped with Rare-Earths and Transition Metal Ions

    Science.gov (United States)

    2001-01-01

    K.P. O’Donnell, B. Henderson and D. Hollis, " Disorder and the optical spectroscopy of Cr 3+- doped glasses: II. Glasses with high and low ligand...ions in oxide compounds", Fiz. Tw. Tela, 31(1), pp. 243-249, 1989. 11. W. Chen, J.O. Maim, V. Zwiller, Y. Huang, S. Liu, R. Wallenberg , J.O. Bovin and L

  11. Investigation of luminescence and laser transition of Dy3+ in Li2O-Gd2O3-Bi2O3-B2O3 glasses

    Science.gov (United States)

    Zaman, F.; Kaewkhao, J.; Srisittipokakun, N.; Wantana, N.; Kim, H. J.; Rooh, G.

    2016-05-01

    The aim of this study is to develop Li2O-Gd2O3-Bi2O3-B2O3 glass doped with different concentration of Dy3+ ions by melt quenching technique for different applications in photonics and laser devices. From the experimental oscillator strength (fexp) of the absorption spectra the JO intensity parameters (Ω λ = 2, 4, 6) have been calculated, and by using these JO intensity parameters various radiative parameters were calculated. By using JO theory the radiative transition probability (AR), radiative lifetime (τR) and branching ratio (βR) for Dy3+ ion have been found. A decrease in lifetimes of the prepared glass by increasing concentration of Dy3+ is because of the energy transfer through cross relaxation and resonant energy transfer channels in the present glass matrix. Using experimental and calculated lifetimes, the quantum efficiency (η) and non-radiative relaxation rates (WNR) of 4F9/2 excited state have been calculated. From emission spectra, effective bandwidths (Δλeff) and emission stimulated emission cross section σ (λp) were found for 4F9/2 → 6HJ (J = 15/2, 13/2, 11/2 and 9/2). Chromaticity results revealed that the CCT values of the LGBiBDy glass samples are in between to those of day light and commercial white light LED sources. Further investigations are under way for the optimization of dopant concentration in the Li2O-Gd2O3-Bi2O3-B2O3 glass.

  12. Long-Term Stability of New Co-Amorphous Drug Binary Systems: Study of Glass Transitions as a Function of Composition and Shelf Time.

    Science.gov (United States)

    Martínez, Luz María; Videa, Marcelo; Sosa, Nahida González; Ramírez, José Héctor; Castro, Samuel

    2016-12-14

    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 formulation.

  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. Sugar-induced blue membrane: release of divalent cations during phase transition of purple membranes observed in sugar-derived glasses.

    Science.gov (United States)

    Rhinow, Daniel; Hampp, Norbert A

    2008-04-17

    The formation of blue membrane from purple membranes (PM) has been observed in glassy films made from PM and various sugars. The phase transition of PM at about 70 degrees C causes the complexation of divalent cations to be weakened. The vicinal diol structures in sugars are capable to complex divalent cations and delocalize them throughout the matrix as long as its glass transition temperature is lower than the phase transition temperature of PM. The loss of divalent cations from bacteriorhodopsin (BR), the only protein in PM, causes the formation of blue membrane (BM), which is accompanied by a loss of beta-sheet structure observable in the infrared spectrum. Glassy sugars are particular useful to observe this transition, as sugar entrapment does not restrict conformational changes of BR but rather retards them. The material obtained was named sugar-induced blue membrane (SIBM). The formation of SIBM is inhibited by the addition of divalent cations. Furthermore, SIBM is reverted immediately to PM by addition of water. A characteristic time dependence of the thermal reversion of SIBM to PM proves that the phase transition of PM triggers the release and uptake of divalent cations and the corresponding color change.

  15. Estimating subsurface water volumes and transit times in Hokkaido river catchments, Japan, using high-accuracy tritium analysis

    Science.gov (United States)

    Gusyev, Maksym; Yamazaki, Yusuke; Morgenstern, Uwe; Stewart, Mike; Kashiwaya, Kazuhisa; Hirai, Yasuyuki; Kuribayashi, Daisuke; Sawano, Hisaya

    2015-04-01

    The goal of this study is to estimate subsurface water transit times and volumes in headwater catchments of Hokkaido, Japan, using the New Zealand high-accuracy tritium analysis technique. Transit time provides insights into the subsurface water storage and therefore provides a robust and quick approach to quantifying the subsurface groundwater volume. Our method is based on tritium measurements in river water. Tritium is a component of meteoric water, decays with a half-life of 12.32 years, and is inert in the subsurface after the water enters the groundwater system. Therefore, tritium is ideally suited for characterization of the catchment's responses and can provide information on mean water transit times up to 200 years. Only in recent years has it become possible to use tritium for dating of stream and river water, due to the fading impact of the bomb-tritium from thermo-nuclear weapons testing, and due to improved measurement accuracy for the extremely low natural tritium concentrations. Transit time of the water discharge is one of the most crucial parameters for understanding the response of catchments and estimating subsurface water volume. While many tritium transit time studies have been conducted in New Zealand, only a limited number of tritium studies have been conducted in Japan. In addition, the meteorological, orographic and geological conditions of Hokkaido Island are similar to those in parts of New Zealand, allowing for comparison between these regions. In 2014, three field trips were conducted in Hokkaido in June, July and October to sample river water at river gauging stations operated by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). These stations have altitudes between 36 m and 860 m MSL and drainage areas between 45 and 377 km2. Each sampled point is located upstream of MLIT dams, with hourly measurements of precipitation and river water levels enabling us to distinguish between the snow melt and baseflow contributions

  16. Molecular dynamics study of structure and glass forming ability of Zr70Pd30 alloy

    Science.gov (United States)

    Celtek, Murat; Sengul, Sedat; Domekeli, Unal; Canan, Cem

    2016-03-01

    In this study, the temperature effects on the structural evolution of the Zr70Pd30 binary alloy in the glassy and liquid states were studied using the molecular dynamics simulations based on the many-body type tight-binding potential. We considered the following properties in detail: the temperature dependence of the volume, the partial and total pair distribution functions and the simulated glass transition temperature. The effects of the cooling rates on the glass transition temperature were examined. The Wendt-Abraham parameter was calculated to determine the glass transition temperature of Zr70Pd30 glassy alloy. The pair analysis technique of Honeycutt-Andersen was applied to define local atomic arrangements produced from molecular dynamics simulations. The results show that the icosahedral ordering in glassy state has been composed during quenching period, and the simulated glass transition temperature and the total pair distribution functions are in good agreement with the experimental data.

  17. Bragg Gratings, Photosensitivity, and Poling in Glass Fibers and Waveguides: Applications and Fundamentals. Technical Digest Series, Volume 17

    Science.gov (United States)

    1998-05-26

    integrated photonics, A.J. Bruce, Lucent Technologies. (P. 86) JSuE30 ■ Preparation and nonlinear optical proper- ties of Au/glass composite thin films, I...crystalline arrangements alike. For example, the local clusters of cristobalite and quartz are compared in Figure 2. The first contains 29 tetrahedra and only...6-rings; the second contains 63 tetrahedra and is dominated by 8- rings. Figure 2: Local clusters of a) cristobalite (29 tetrahedra, 6 12 -rings

  18. Evidence of PPII-like helical conformation and glass transition in a self-assembled solid-state polypeptide-surfactant complex: poly(L-histidine)/docylbenzenesulfonic acid.

    Science.gov (United States)

    Ramani, Ramasubbu; Hanski, Sirkku; Laiho, Ari; Tuma, Roman; Kilpeläinen, Simo; Tuomisto, Filip; Ruokolainen, Janne; Ikkala, Olli

    2008-05-01

    We present lamellar self-assembly of cationic poly(L-histidine) (PLH) stoichiometrically complexed with an anionic surfactant, dodecyl benzenesulfonic acid (DBSA), which allows a stabilized conformation reminiscent of polyproline type II (PPII) left-handed helices. Such a conformation has no intrapeptide hydrogen bonds, and it has previously been found to be one source of flexibility, e.g., in collagen and elastin, as well as an intermediate in silk processing. PLH(DBSA)1.0 complexes were characterized by Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The PPII-like conformation in PLH(DBSA)1.0 is revealed by characteristic CD and FTIR spectra, where the latter indicates absence of intrachain peptide hydrogen bonds. In addition, a glass transition was directly verified by DSC at ca. 135 degrees C for PLH(DBSA)1.0 and indirectly by SAXS and TEM in comparison to pure PLH at 165 degrees C, thus indicating plasticization. Glass transitions have not been observed before in polypeptide-surfactant complexes. The present results show that surfactant binding can be a simple scheme to provide steric crowding to stabilize PPII conformation to tune the polypeptide properties, plasticization and flexibility.

  19. 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.

  20. 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 (Tg), 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 ΔTg (≡Tg - Tg0; where Tg0 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].

  1. 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.

  2. Activation volume in heterogeneous deformation of Mg{sub 65}Cu{sub 12.5}Ni{sub 12.5}(Ce{sub 75}La{sub 25}){sub 10} metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Thurieau, Nicolas; Perrière, Loïc; Laurent-Brocq, Mathilde [ICMPE, CNRS-UPEC, 2 rue Henri Dunant 94320 Thiais, Cedex (France); Champion, Yannick, E-mail: yannick.champion@simap.grenoble-inp.fr [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France)

    2015-11-28

    Depth variation at constant load in instrumented nano-indentation was used to measure activation volume controlling shear band formation in the Mg{sub 65}Cu{sub 12.5}Ni{sub 12.5}(Ce{sub 75}La{sub 25}){sub 10} metallic glass. A series of measurements revealed a large scattering of the data spanning from 100 Å{sup 3} to 800 Å{sup 3}. The distribution of values, which is not following a normal one, may be attributed to the atomic structure of metallic glasses with the absence of long range order, leading to different volume fraction of shear bands for independent experiments. Activation volume is analyzed considering the variation of shear band volume fraction leading to a unique value of a true activation volume. An interpretation for the distribution of values is proposed.

  3. Thermal Conductivity of Foam Glass

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    Due to the increased focus on energy savings and waste recycling foam glass materials have gained increased attention. The production process of foam glass is a potential low-cost recycle option for challenging waste, e.g. CRT glass and industrial waste (fly ash and slags). Foam glass is used...... as thermal insulating material in building and chemical industry. The large volume of gas (porosity 90 – 95%) is the main reason of the low thermal conductivity of the foam glass. If gases with lower thermal conductivity compared to air are entrapped in the glass melt, the derived foam glass will contain...... only closed pores and its overall thermal conductivity will be much lower than that of the foam glass with open pores. In this work we have prepared foam glass using different types of recycled glasses and different kinds of foaming agents. This enabled the formation of foam glasses having gas cells...

  4. Characterization of structural relaxation in inorganic glasses using length dilatometry

    Science.gov (United States)

    Koontz, Erick

    The processes that govern how a glass relaxes towards its thermodynamic quasi-equilibrium state are major factors in understanding glass behavior near the glass transition region, as characterized by the glass transition temperature (Tg). Intrinsic glass properties such as specific volume, enthalpy, entropy, density, etc. are used to map the behavior of the glass network below in and near the transition region. The question of whether a true thermodynamic second order phase transition takes place in the glass transition region is another pending question. Linking viscosity behavior to entropy, or viewing the glass configuration as an energy landscape are just a couple of the most prevalent methods used for attempting to understand the glass transition. The structural relaxation behavior of inorganic glasses is important for more than scientific reasons, many commercial glass processing operations including glass melting and certain forms of optical fabrication include significant time spent in the glass transition region. For this reason knowledge of structural relaxation processes can, at a minimum, provide information for annealing duration of melt-quenched glasses. The development of a predictive model for annealing time prescription has the potential to save glass manufacturers significant time and money as well as increasing volume throughput. In optical hot forming processes such as precision glass molding, molded optical components can significantly change in shape upon cooling through the glass transition. This change in shape is not scientifically predictable as of yet though manufacturers typically use empirical rules developed in house. The classification of glass behavior in the glass transition region would allow molds to be accurately designed and save money for the producers. The work discussed in this dissertation is comprised of the development of a dilatometric measurement and characterization method of structural relaxation. The measurement and

  5. Glasses and grains : Poincaré seminar

    CERN Document Server

    Rivasseau, Vincent; Duplantier, Bertrand

    2011-01-01

    This tenth volume in "The Poincare Seminar Series" describes recent developments at one of the most challenging frontiers in statistical physics - the deeply related fields of glassy dynamics, especially near the glass transition, and of the statics and dynamics of granular systems. These fields are marked by a vigorous interchange between experiment, theory, and numerical studies, all of which are well represented by the leading experts who have contributed articles to this volume. These articles are also highly pedagogical, as befits their origin in lectures to a broad scientific a

  6. 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.

  7. 玻璃化转变温度测试方法对测试结果的影响%Influence of Glass Transition Temperature Test Methods on Test Results

    Institute of Scientific and Technical Information of China (English)

    张霞; 王从科; 郑素萍; 凡丽梅; 夏敏

    2012-01-01

    The glass transition temperature of fiber glass reinforced nylon 66 and PE-HD was measured by means of differential scanning calorimetry ( DSC ) and dilatomery (DIL ) .The results showed that the glass transition temperature changed with the different measurement methods and conditions, the glass transition temperature obtained by means of different measurement methods wasn't comparable. The adopted measurement methods and conditions should be specified in the description of glass transition temperature.%以玻纤增强尼龙66、高密度聚乙烯为样品,分别采用差示扫描量热法和热膨胀法测试了样品的玻璃化转变温度(Tg).结果表明,材料的Tg随测试方法、测试条件的不同而变化,采用不同的测试方法所得的Tg结果之间不具有可比性,在说明某种材料的Tg时,应注明所采用的测试方法和测试条件.

  8. 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

    2016-05-06

    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.

  9. 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

    2016-05-01

    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.

  10. Effects of cooling rates on the mechanical properties of a Ti-based bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Mechanical properties of the glassy specimens fabricated at different cooling rates with a composition of Ti40Zr25Cu12Ni3Be20 were systematically investigated. It was confirmed that faster cooling rates caused not only a larger amount of frozen-in free volume but also a higher glass transition temperature in the bulk glassy alloy. Increase in the free volume was found to favor plastic deformation and then to give rise to larger compressive plasticity, whilst the rise in the glass transition temperature seemed to be closely related to the higher yield strength. Moreover, the increase of yield strength and plasticity induced by fast cooling rates may also be associated with the residual stress generated during the fabrication process. Our results suggest that the deformation behavior of bulk metallic glasses is sensitive to various factors and influences from the other factors should be excluded as far as cooling-rate effects on bulk metallic glasses are considered.

  11. Multichannel 0-to-2 and 1-to-2 transition amplitudes for arbitrary spin particles in a finite volume

    CERN Document Server

    Briceño, Raúl A

    2015-01-01

    We present a model-independent, non-perturbative relation between finite-volume matrix elements and infinite-volume $\\textbf{0}\\rightarrow\\textbf{2}$ and $\\textbf{1}\\rightarrow\\textbf{2}$ transition amplitudes. Our result accommodates theories in which the final two-particle state is coupled to any number of other two-body channels, with all angular momentum states included. The derivation uses generic, fully relativistic field theory, and is exact up to exponentially suppressed corrections in the lightest particle mass times the box size. This work distinguishes itself from previous studies by accommodating particles with any intrinsic spin. To illustrate the utility of our general result, we discuss how it can be implemented for studies of $N+\\mathcal{J}~\\rightarrow~(N\\pi,N\\eta,N\\eta',\\Sigma K,\\Lambda K)$ transitions, where $\\mathcal{J}$ is a generic external current. The reduction of rotational symmetry, due to the cubic finite volume, manifests in this example through the mixing of S- and P-waves when the...

  12. Sink property of metallic glass free surfaces.

    Science.gov (United States)

    Shao, Lin; Fu, Engang; Price, Lloyd; Chen, Di; Chen, Tianyi; Wang, Yongqiang; Xie, Guoqiang; Lucca, Don A

    2015-03-16

    When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences. For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.

  13. Thermodynamics of rotating black holes and black rings: phase transitions and thermodynamic volume

    CERN Document Server

    Altamirano, Natacha; Mann, Robert B; Sherkatghanad, Zeinab

    2014-01-01

    In this review we summarize, expand, and set in context recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. We specifically consider the thermodynamics of higher-dimensional rotating asymptotically flat and AdS black holes and black rings in a canonical (fixed angular momentum) ensemble. We plot the associated thermodynamic potential-the Gibbs free energy-and study its behaviour to uncover possible thermodynamic phase transitions in these black hole spacetimes. We show that the multiply-rotating Kerr-AdS black holes exhibit a rich set of interesting thermodynamic phenomena analogous to the "every day thermodynamics" of simple substances, such as reentrant phase transitions of multicomponent liquids, multiple first-order solid/liquid/gas phase transitions, and liquid/gas phase transitions of the Van der Waals type. Furthermore, the reentrant phase tran...

  14. Effect of Fe2O3 on the physical and structural properties of bismuth silicate glasses

    Science.gov (United States)

    Parmar, Rajesh; Kundu, R. S.; Punia, R.; Aghamkar, P.; Kishore, N.

    2013-06-01

    Iron containing bismuth silicate glasses with compositions 70SiO2ṡ(100-x)Bi2O3ṡxFe2O3 have been prepared using conventional melt-quenching method and their amorphous nature has been investigated using XRD. Density has been measured using Archimedes' principle and molar volume (Vm) have also been estimated. With increase in Fe2O3 content, there is a decrease in density and molar volume of the glass samples. The glass transition temperature (Tg) have been determined using Differential Scanning Calorimetry (DSC) and are observed to increase with increase in Fe2O3 content. In the present glass system bismuth and iron plays the role of network modifier and the symmetry of silicate network goes on increasing with Fe2O3 content and it modifies the physical and structural properties of these glasses.

  15. Are the dynamics of silicate glasses and glass-forming liquids embedded in their elastic properties?

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Mauro, John C.

    According to the elastic theory of the glass transition, the dynamics of glasses and glass-forming liquids are controlled by the evolution of shear modulus. In particular, the elastic shoving model expresses dynamics in terms of an activation energy required to shove aside the surrounding atoms, ...... of the silicate glass transition are governed by additional factors beyond the evolution of the shear modulus....

  16. Gadolinium-Induced Multi-Effect on Properties of IR Transmitting Chalcogenide Glasses

    Institute of Scientific and Technical Information of China (English)

    ZHAO Dong-Hui; XIA Fang; NIE Jia-Xiang; CHEN Guo-Rong; ZHANG Xiang-Hua; MA Hong-Li; ADAM Jean-Luc

    2004-01-01

    @@ We introduce gadolinium in chalcogenide glasses to exert unexpectedly the multiple magical effects on both optical and thermal mechanical properties of chalcogenide glasses. Notable increases in transition temperature Tg and microhardness Hv were observed due to structural densitication and microcrystallization. Calculated molar volume values, differential scanning calorimetry and x-ray diffraction measurements provide supporting evidences. Gadolinium also acts as oxygen getter by removing or weakening oxygen-related absorption bands,which is associated with the higher negative electrode potential.

  17. Non-ergodicity transition and multiple glasses in binary mixtures: on the accuracy of the input static structure in the mode coupling theory.

    Science.gov (United States)

    Tchangnwa Nya, F; Ayadim, A; Germain, Ph; Amokrane, S

    2012-08-15

    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.

  18. Diphenylamino-substituted bicarbazole derivative: Hole-transporting material with high glass-transition temperature, good electron and triplet exciton blocking capabilities and efficient hole injection

    Science.gov (United States)

    Chen, Shanyong; Jiang, Shan; Yu, Hong

    2017-04-01

    A diphenylamino-substituted bicarbazole derivative (BCZDA) with high glass-transition temperature (170 °C) has been developed. The introduction of the strongly electron-donating diphenylamino group endows this compound with high HOMO (-4.94 eV), LUMO (-1.94 eV) and triplet energy (2.65 eV) levels which are beneficial for hole injection and electron/triplet exciton blocking. By adopting this compound as the hole-transporting layer, both fluorescent and phosphorescent devices with good performance have been realized. Through the device study, the performance of this compound is proved to be comparable to that of NPB. The utility of this compound as a host has also been evaluated.

  19. 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.

    2017-05-01

    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, Fs(qz, z, t), for distances z from the graphite walls in the range of a few nanometers. Temperatures from about 2Tg down to about 1.15Tg, where Tg 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 Tg 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.

  20. Iso-conversional approach for study of glass transition and crystallization kinetics of ternary glassy Se{sub 98−x}Ag{sub 2}In{sub x} (x = 0, 2, 4, 6) system

    Energy Technology Data Exchange (ETDEWEB)

    Dohare, C.; Mehta, N., E-mail: dr_neeraj_mehta@yahoo.co.in

    2014-02-25

    Highlights: • Novel glasses of Se–Ag–In system are prepared. • The effect of In incorporation on glass transition kinetics is studied. • The effect of In incorporation on crystallization kinetics is studied. • We have found remarkable increase in thermal stability. -- Abstract: The glass transition and crystallization kinetics of Se{sub 98−x}Ag{sub 2}In{sub x} (x = 0, 2, 4, 6) glasses have been studied under non-isothermal condition using differential scanning calorimetry (DSC). Using model free approach [Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Tang and Straink], the activation energy of glass transition, ΔE{sub αg} and crystallization kinetics, ΔE{sub αc} have been plotted as a function of extent of conversion, α. The kinetic parameters such as the activation energy (E), Avrami exponent (n), and rate of crystallization (K) have been determined using Kolmogorov–Johnson–Mehl–Avrami (KJMA) model. Glassy nature of as prepared samples was confirmed by XRD (X-ray diffraction), surface morphology and diffraction pattern by SEM and TEM, respectively.

  1. Effect of Boron Addition on the Thermal, Degradation, and Cytocompatibility Properties of Phosphate-Based Glasses

    Directory of Open Access Journals (Sweden)

    Nusrat Sharmin

    2013-01-01

    Full Text Available In this study eight different phosphate-based glass compositions were prepared by melt-quenching: four in the (P2O545-(CaO16--(MgO24- system and four in the system (P2O550-(CaO16--(MgO24-, where and 10 mol%. The effect of B2O3 addition on the thermal properties, density, molar volume, dissolution rates, and cytocompatibility were studied for both glass systems. Addition of B2O3 increased the glass transition (, crystallisation (, melting (, Liquidus ( and dilatometric softening ( temperature and molar volume (. The thermal expansion coefficient (α and density ( were seen to decrease. An assessment of the thermal stability of the glasses was made in terms of their processing window (crystallisation onset, minus glass transition temperature, , and an increase in the processing window was observed with increasing B2O3 content. Degradation studies of the glasses revealed that the rates decreased with increasing B2O3 content and a decrease in degradation rates was also observed as the P2O5 content reduced from 50 to 45 mol%. MG63 osteoblast-like cells cultured in direct contact with the glass samples for 14 days revealed comparative data to the positive control for the cell metabolic activity, proliferation, ALP activity, and morphology for glasses containing up to 5 mol% of B2O3.

  2. A formula to compute the microcanonical volume of reactive initial conditions in transition state theory

    NARCIS (Netherlands)

    Waalkens, H.; Burbanks, A.; Wiggins, S.

    2005-01-01

    We present the formal proof of a procedure to compute the phase-space volume of initial conditions for trajectories that, for a constant energy, escape or ‘react’ from a multi-dimensional potential well with one or several exit/entrance channels. The procedure relies on a phase-space formulation of

  3. A formula to compute the microcanonical volume of reactive initial conditions in transition state theory

    NARCIS (Netherlands)

    Waalkens, H.; Burbanks, A.; Wiggins, S.

    2005-01-01

    We present the formal proof of a procedure to compute the phase-space volume of initial conditions for trajectories that, for a constant energy, escape or ‘react’ from a multi-dimensional potential well with one or several exit/entrance channels. The procedure relies on a phase-space formulation of

  4. 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

    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....

  5. Investigation of spin-reorientation phase transitions at surface and in volume of alpha-Fe sub 2 O sub 3 monocrystals

    CERN Document Server

    Kamzin, A S

    2002-01-01

    The magnetic structure of the surface layer and volume and the processes, observed by the spin-reorientation phase transition (SRPT), are studied in the direct comparison of the properties of the thin surface layer and the volume of the hematite (alpha-Fe sub 2 O sub 3) macroscopic crystals. The method of simultaneous gamma, X-ray and electron Moessbauer spectroscopy was used in the studies. The direct data on the existence of the transition layer on the hematite crystals surface are obtained. It is established, that the Morin-type SRPT in the sample volume occurs by a jump (the first-order phase transition). The SRPT in the surface layer as well as in the crystal volume is accompanied by formation of the intermediate state, wherein the low- and high-temperature phases coexist. The obtained experimental data on the SRPT mechanism in the surface layer agree well with the conclusions of the phenomenological theory

  6. Thermomechanical Modeling of Laser-Induced Structural Relaxation and Deformation of Glass: Volume Changes in Fused Silica at High Temperatures [Thermo-mechanical modeling of laser-induced structural relaxation and deformation of SiO2 glass

    Energy Technology Data Exchange (ETDEWEB)

    Vignes, Ryan M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Ignition Facility and Photon Sciences; Soules, Thomas F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Ignition Facility and Photon Sciences; Stolken, James S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Ignition Facility and Photon Sciences; Settgast, Randolph R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Ignition Facility and Photon Sciences; Elhadj, Selim [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Ignition Facility and Photon Sciences; Matthews, Manyalibo J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Ignition Facility and Photon Sciences; Mauro, J.

    2012-12-17

    In a fully coupled thermomechanical model of the nanoscale deformation in amorphous SiO2 due to laser heating is presented. Direct measurement of the transient, nonuniform temperature profiles was used to first validate a nonlinear thermal transport model. Densification due to structural relaxation above the glass transition point was modeled using the Tool-Narayanaswamy (TN) formulation for the evolution of structural relaxation times and fictive temperature. TN relaxation parameters were derived from spatially resolved confocal Raman scattering measurements of Si–O–Si stretching mode frequencies. These thermal and microstructural data were used to simulate fictive temperatures which are shown to scale nearly linearly with density, consistent with previous measurements from Shelby et al. Volumetric relaxation coupled with thermal expansion occurring in the liquid-like and solid-like glassy states lead to residual stresses and permanent deformation which could be quantified. But, experimental surface deformation profiles between 1700 and 2000 K could only be reconciled with our simulation by assuming a roughly 2 × larger liquid thermal expansion for a-SiO2 with a temperature of maximum density ~150 K higher than previously estimated by Bruckner et al. Calculated stress fields agreed well with recent laser-induced critical fracture measurements, demonstrating accurate material response prediction under processing conditions of practical interest.

  7. Elastic properties of Li+ doped lead zinc borate glasses

    Science.gov (United States)

    Rajaramakrishna, R.; Lakshmikantha, R.; Anavekar, R. V.

    2014-04-01

    Glasses in the system 0.25PbO-(0.25-x) ZnO-0.5B2O3-xLi2O have been prepared by the melt quenching technique. Elastic properties, DSC studies have been employed to study the role of Li2O in the present glass system. Elastic properties and Debye temperature have been determined using pulsed echo ultrasonic interferometer operating at 10MHz. Sound velocities Vl, Vt and elastic moduli decrease up to 5 mol% and then gradually increase with increase in Li2O concentration. Debye temperature and the glass transition temperature decreases with increase in Li2O. Densities remains almost constant up to 15 mol% Li2O concentration and increases monotonically while the molar volume decreases with the increase of Li2O concentration. The results are discussed in view of the borate structural network and dual role of Zn and Pb in these glasses.

  8. Fast-ion conducting glass and glass-ceramics for the pH sensor Ionic conductivity

    CERN Document Server

    Niyompan, A

    2002-01-01

    Fast-ion conducting glasses of the compositions Na sub 1 sub + sub x M sub 2 sub - sub x sub / sub 3 Si sub x P sub 3 sub - sub x O sub 1 sub 2 sub - sub 2 sub x sub / sub 3 (0<= x <=3), where M = Zr, Ti, were studied to determine their structural arrangement, physical properties and ionic conductivity. Glass samples were prepared using the conventional melt-quench method in the melting temperature range, 1550 deg C to 1650 deg C. Glass products were characterised by XRD, DTA, dilatometry and density measurement. Solid state MAS NMR experiments of three accessible nuclei, sup 2 sup 3 Na, sup 2 sup 9 Si and sup 3 sup 1 P were used to determine short-range order arrangement in the glasses. XRD confirms the amorphicity of glasses for the compositions of x in range 0-3. Glass transition temperatures, T sub g , TEC, and molar volume are controlled by glass composition. The MAS NMR results suggest that glass structure could be visualised as the silicate network modified by Na sup + and Zr sup 4 sup + or Ti su...

  9. Probing effect of solvent concentration on glass transition and sub-Tg structural relaxation in polymer solvent mixtures: The case of polystyrene-toluene system

    Science.gov (United States)

    Pierleoni, Davide; Scherillo, Giuseppe; Minelli, Matteo; Mensitieri, Giuseppe; Doghieri, Ferruccio

    2016-05-01

    A novel experimental method for the analysis of volume relaxation induced by solvents in glassy polymers is presented. A gravimetric technique is used to evaluate the isothermal solvent mass uptake at controlled increasing/decreasing solvent pressure at constant rate. Fundamental properties of the solvent/polymer system can be obtained directly, and models can be applied, combining both nonequilibrium thermodynamics and mechanics of volume relaxation contribution. The fundamental case of polystyrene and toluene mixtures are thus accounted for, and various experimental conditions have been explored, varying the temperature, and spanning over different pressure increase/decrease rates. The results obtained allowed to evaluate the isothermal second order transition induced by solvent sorption, as well as the determination of the effect of the pressure rate. Therefore, this work proposes a new standard for the characterization and the understanding of the relaxational behavior of glassy polymers.

  10. Probing effect of solvent concentration on glass transition and sub-T{sub g} structural relaxation in polymer solvent mixtures: The case of polystyrene-toluene system

    Energy Technology Data Exchange (ETDEWEB)

    Pierleoni, Davide; Minelli, Matteo; Doghieri, Ferruccio [Department of Civil, Chemical, Environmental and Materials Engineering (DICAM) - Alma Mater Studiorum - University of Bologna - via Terracini 28 - 40132 Bologna (Italy); Scherillo, Giuseppe; Mensitieri, Giuseppe [Department of Chemical and Materials Engineering and Industrial Production DICMaPI, University of Naples Federico II –Piazzale Tecchio 80 – 80125 Napoli (Italy)

    2016-05-18

    A novel experimental method for the analysis of volume relaxation induced by solvents in glassy polymers is presented. A gravimetric technique is used to evaluate the isothermal solvent mass uptake at controlled increasing/decreasing solvent pressure at constant rate. Fundamental properties of the solvent/polymer system can be obtained directly, and models can be applied, combining both nonequilibrium thermodynamics and mechanics of volume relaxation contribution. The fundamental case of polystyrene and toluene mixtures are thus accounted for, and various experimental conditions have been explored, varying the temperature, and spanning over different pressure increase/decrease rates. The results obtained allowed to evaluate the isothermal second order transition induced by solvent sorption, as well as the determination of the effect of the pressure rate. Therefore, this work proposes a new standard for the characterization and the understanding of the relaxational behavior of glassy polymers.

  11. Exact Calculation of Antiferromagnetic Ising Model on an Inhomogeneous Surface Recursive Lattice to Investigate Thermodynamics and Glass Transition on Surface/Thin Film

    Science.gov (United States)

    Huang, Ran; Gujrati, Purushottam D.

    2017-01-01

    An inhomogeneous 2-dimensional recursive lattice formed by planar elements has been designed to investigate the thermodynamics of Ising spin system on the surface/thin film. The lattice is constructed as a hybrid of partial Husimi square lattice representing the bulk and 1D single bonds representing the surface. Exact calculations can be achieved with the recursive property of the lattice. The model has an anti-ferromagnetic interaction to give rise to an ordered phase identified as crystal, and a solution with higher energy to represent the amorphous/metastable phase. Free energy and entropy of the ideal crystal and supercooled liquid state of the model on the surface are calculated by the partial partition function. By analyzing the free energies and entropies of the crystal and supercooled liquid state, we are able to identify the melting and ideal glass transition on the surface. The results show that due to the variation of coordination number, the transition temperatures on the surface decrease significantly compared to the bulk system. Our calculation qualitatively agrees with both experimental and simulation works on the thermodynamics of surfaces and thin films conducted by others. Interactions between particles farther than the nearest neighbor distance are taken into consideration, and their effects are investigated. Supported by the National Natural Science Foundation of China under Grant No. 11505110, the Shanghai Pujiang Talent Program under Grant No. 16PJ1431900, and the China Postdoctoral Science Foundation under Grant No. 2016M591666

  12. 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.

  13. On the mutual relationships between spin probe mobility, free volume and relaxation dynamics in organic glass-formers: Glycerol

    Science.gov (United States)

    Bartoš, J.; Švajdlenková, H.

    2017-02-01

    The rotation dynamics of the spin probe TEMPO in glycerol from ESR is compared with the ortho-positronium (o-Ps) annihilation from PALS and interpreted using the relaxation dynamics from BDS. Rotation time scale within the slow motion regime exhibits two Arrhenius regions with the characteristic ESR temperature, TX1τ, close to the characteristic PALS temperature, Tb1L, which is related to the secondary β process above Tg. Next, a slow to fast motion regime transition at the characteristic ESR temperature, Tcτ, close to the characteristic PALS temperature, Tb2L, followed by non-Arrhenius fast motion regime region is fully coupled with the primary α process.

  14. Correlation functions between specific volume and stoichiometry for transition metal nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Soto, G. [Centro de Ciencias de la Materia Condensada, UNAM, Ap. Postal 2681, 22800 Ensenada B. C. (Mexico)]. E-mail: gerardo@ccmc.unam.mx; Aparicio, E. [Centro de Ciencias de la Materia Condensada, UNAM, Ap. Postal 2681, 22800 Ensenada B. C. (Mexico); Avalos-Borja, M. [Centro de Ciencias de la Materia Condensada, UNAM, Ap. Postal 2681, 22800 Ensenada B. C. (Mexico)

    2005-03-08

    A methodology is proposed to correlate the structural aspects of transition metal nitrides (TMN) to the stoichiometric ratio: x = [N]/[M]. The method is based on a numeric figure, {upsilon}, given by the difference between the atomic concentrations of nitride and parent metal normalized to the atomic concentration of parent metal. Numerical regression is used to construct interpolating functions for {upsilon}(x) using as input the available data for TMN in two well-recognized databases (ICDD and ICSD). In summary we obtain functions of x that describe the deformation caused in the parent metal lattice by the nitrogen assimilation. The results are attractive, since TMN show remarkable trends.

  15. Transition report, United States Department of Energy: A report to the President-Elect. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    1988-11-01

    This report is a description of the Department of Energy transition issues. The topics of the report include: Congressional, Intergovernmental and Public Affairs; Conservation and Renewable Energy; Defense Programs; New Production Reactors; Economic Regulatory Administration; Energy Information Administration; energy research; environment, safety and health; fossil energy; General Counsel; hearings and appeals, Inspector General, international affairs and energy emergencies; management and administration, minority economic impact; nuclear energy; policy, planning and analysis, radioactive waste management; and power marketing administrations: Bonneville Power Administration, Western Area Power Administration, Alaska Power Administration, Southeastern Power Administration, and Southwestern Power Administration.

  16. 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...

  17. Multi-channel 1-to-2 transition amplitudes in a finite volume

    Energy Technology Data Exchange (ETDEWEB)

    Briceno, Raul [JLAB; Hansen, Maxwell [Helmholtz Institute Mainz; Walker-Loud, Andre P [W& M. JLAB

    2015-04-01

    We derive a model-independent expression for finite-volume matrix elements. Specifically, we present a relativistic, non-perturbative analysis of the matrix element of an external current between a one-scalar in-state and a two-scalar out-state. Our result, which is valid for energies below higher-particle inelastic thresholds, generalizes the Lellouch-Luscher formula in two ways: we allow the external current to inject arbitrary momentum into the system and we allow for the final state to be composed an arbitrary number of strongly coupled two-particle states with arbitrary partial waves (including partial-wave mixing induced by the volume). We also illustrate how our general result can be applied to some key examples, such as heavy meson decays and meson photo production. Finally, we point out complications that arise involving unstable resonance states, such as B to K*+l+l when staggered or mixed-action/partially-quenched calculations are performed.

  18. Multichannel one-to-two transition amplitudes in a finite volume

    CERN Document Server

    Briceño, Raúl A; Walker-Loud, André

    2015-01-01

    We derive a model-independent expression for finite-volume matrix elements. Specifically, we present a relativistic, non-perturbative analysis of the matrix element of an external current between a one-scalar in-state and a two-scalar out-state. Our result, which is valid for energies below higher-particle inelastic thresholds, generalizes the Lellouch-Luscher formula in two ways: we allow the external current to inject arbitrary momentum into the system and we allow for the final state to be composed an arbitrary number of strongly coupled two-particle states with arbitrary partial waves (including partial-wave mixing induced by the volume). We also illustrate how our general result can be applied to some key examples, such as heavy meson decays and meson photo production. Finally, we point out complications that arise involving unstable resonance states, such as $B\\rightarrow K^*\\ell^+\\ell^-$ when staggered or mixed-action/partially-quenched calculations are performed.

  19. Multichannel one-to-two transition form factors in a finite volume

    CERN Document Server

    Briceño, Raúl A; Walker-Loud, André

    2014-01-01

    We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B-to-pi Kll) or meson photo production (e.g., pi gamma-to-pi pi). We observe that, while the spectrum solely depends upon the on-shell scattering amplitude, the correlation functions also depend upon off-shell amplitudes. The main result of this work is a non-perturbative generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular-momentum. The result is exact up to exponential corrections governed by mpi L. We p...

  20. A possible scenario for the fragile-to-strong dynamic crossover predicted by the extended mode-coupling theory for glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Chong, S-H [Institute for Molecular Science, Okazaki 444-8585 (Japan); Chen, S-H [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Mallamace, F, E-mail: chong@ims.ac.j [Dipartimento di Fisica, Universita di Messina and IRCCS Neurolesi ' Bonino-Pulejo' , I-98166 Messina (Italy)

    2009-12-16

    It is argued that the extended mode-coupling theory for glass transition predicts a dynamic crossover in the alpha-relaxation time and in the self-diffusion constant as a general implication of the structure of its equations of motion. This crossover occurs near the critical temperature T{sub c} of the idealized version of the theory, and is caused by the change in the dynamics from the one determined by the cage effect to that dominated by hopping processes. When combined with a model for the hopping kernel deduced from the dynamical theory for diffusion-jump processes, the dynamic crossover can be identified as the fragile-to-strong crossover (FSC) in which the alpha-relaxation time and the self-diffusion constant cross over from a non-Arrhenius to an Arrhenius behavior. Since the present theory does not resort to the existence of the so-called Widom line, to which the FSC in confined water has been attributed, it provides a possible explanation of the FSC observed in a variety of glass-forming systems in which the existence of the Widom line is unlikely. In addition, the present theory predicts that the Stokes-Einstein relation (SER) breaks down in different ways on the fragile and strong sides of the FSC, in agreement with the experimental observation in confined water. It is also demonstrated that the violation of the SER in both the fragile and strong regions can be fitted reasonably well by a single fractional relation with an empirical exponent of 0.85.

  1. Observation of the second-order magnetic and reentrant spin-glass transitions in LiNi{sub 0.5}Mn{sub 0.5}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bie, Xiaofei; Gao, Yu; Yang, Xu; Wei, Yingjin [Key Laboratory of Advanced Batteries Physics and Technology (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Ehrenberg, Helmut; Hinterstein, Manuel [Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Chen, Gang; Wang, Chunzhong [Key Laboratory of Advanced Batteries Physics and Technology (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Du, Fei, E-mail: dufei@jlu.edu.cn [Key Laboratory of Advanced Batteries Physics and Technology (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China)

    2015-03-25

    Highlights: • Rietveld refinement confirms that the sample is a single phase with the rhombohedral layered structure. • Dc susceptibility data suggest a FiM transition at 108 K. • The results of Arrott method indication of the second-order character of the transition. • The ac susceptibility data confirm the SG transition in LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} at 14 K. - Abstract: The structure and magnetic properties of LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} were studied by synchrotron X-ray diffraction, dc and ac susceptibilities. The material showed a continuous magnetic transition from paramagnetism into ferrimagnetism, followed by a spin glass with the decrease of temperature. Using a criterion given by Banerjee to distinguish first-order magnetic transition from second-order ones, it is shown that the ferrimagnetic transition at 108 K belongs to the second-order type. The frequency dependence of peak intensity and the shift in ac susceptibility at 14 K suggest a reentrant spin glass transition in LiNi{sub 0.5}Mn{sub 0.5}O{sub 2}.

  2. Sub-Tg features of glasses formed by cooling glycerol under pressure - Additional incompatibility of vibrational with configurational states in the depressurized, high density glass

    Science.gov (United States)

    Andersson, Ove; Johari, G. P.

    2016-11-01

    The vibrational state of a glass is naturally incompatible with its configurational state, which makes the glass structurally unstable. When a glass is kept at constant temperature, both the vibrational and configurational states of a glass change with time until it becomes metastable (equilibrium) liquid and the two states become compatible. The process, known as structural relaxation, occurs at a progressively higher rate during heating, and the properties of a glass change accordingly. We add to this incompatibility by depressurizing a glass that had been formed by cooling a liquid under a high pressure, p, and then investigate the effects of the added incompatibility by studying thermal conductivity, κ , and the heat capacity per unit volume ρ Cp of the depressurized glass. We use glycerol for the purpose and study first the changes in the features of κ and of ρ Cp during glass formation on cooling under a set of different p. We then partially depressurize the glass and study the effect of the p-induced instability on the features of κ and ρ Cp as the glass is isobarically heated to the liquid state. At a given low p, the glass configuration that was formed by cooling at high-p had a higher κ than the glass configuration that was formed by cooling at a low p. The difference is more when the glass is formed at a higher p and/or is depressurized to a lower p. On heating at a low p, its κ decreases before its glass-liquid transition range is reached. The effect is the opposite of the increase in κ observed on heating a glass at the same p under which it was formed. It is caused by thermally assisted loss of the added incompatibility of configurational and vibrational states of a high-p formed glass kept at low p. If a glass formed under a low-p is pressurized and then heated under high p, it would show the opposite effect, i.e., its κ would first increase to its high p value before its glass-to-liquid transition range.

  3. Low thermal expansion glass ceramics

    CERN Document Server

    1995-01-01

    This book is one of a series reporting on international research and development activities conducted by the Schott group of companies With the series, Schott aims to provide an overview of its activities for scientists, engineers, and managers from all branches of industry worldwide where glasses and glass ceramics are of interest Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated This volume describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization Thus glass ceramics with thermal c...

  4. Investigation of the boundary layer during the transition from volume to surface dominated H⁻ production at the BATMAN test facility.

    Science.gov (United States)

    Wimmer, C; Schiesko, L; Fantz, U

    2016-02-01

    BATMAN (Bavarian Test Machine for Negative ions) is a test facility equipped with a 18 scale H(-) source for the ITER heating neutral beam injection. Several diagnostics in the boundary layer close to the plasma grid (first grid of the accelerator system) followed the transition from volume to surface dominated H(-) production starting with a Cs-free, cleaned source and subsequent evaporation of caesium, while the source has been operated at ITER relevant pressure of 0.3 Pa: Langmuir probes are used to determine the plasma potential, optical emission spectroscopy is used to follow the caesiation process, and cavity ring-down spectroscopy allows for the measurement of the H(-) density. The influence on the plasma during the transition from an electron-ion plasma towards an ion-ion plasma, in which negative hydrogen ions become the dominant negatively charged particle species, is seen in a strong increase of the H(-) density combined with a reduction of the plasma potential. A clear correlation of the extracted current densities (j(H(-)), j(e)) exists with the Cs emission.

  5. Effects of the volume changes and elastic-strain energies on the phase transition in the Li-Sn battery

    Science.gov (United States)

    Zhang, Fan; Wang, Jianchuan; Liu, Shuhong; Du, Yong

    2016-10-01

    Sn and Sn-based compounds have been attracting a great interest as promising alternative materials for commercial anodes in lithium ion batteries. In this study, the phase evolution of the Li-Sn system during the lithiated processes and the effect of the elastic-strain energies caused by volume change on the phase transition are investigated by means of first-principles calculations. Our calculated results demonstrate that the distorted Li7Sn3 crystal tends to be formed in order to decrease the elastic-strain energy. In addition, our work indicates that the whole lithiated processes under the elastically constrained condition could be classified into two steps. The first step is the two-phase equilibrium process, in which the thermodynamic driving force is large enough to facilitate the phase transition and the plateau voltage could be established. The second step is considered to be the selective equilibrium, in which the thermodynamic driving force is not enough to facilitate the nucleation of the new equilibrium phase due to the elastically constrained conditions and the plateau voltage unformed. Besides, we find that in the Li0.4Sn matrix the nucleation of the αSn is more preferential than the βSn due to the effects of the elastic-strain energies.

  6. Investigation of the boundary layer during the transition from volume to surface dominated H- production at the BATMAN test facility

    Science.gov (United States)

    Wimmer, C.; Schiesko, L.; Fantz, U.

    2016-02-01

    BATMAN (Bavarian Test Machine for Negative ions) is a test facility equipped with a 1/8 scale H- source for the ITER heating neutral beam injection. Several diagnostics in the boundary layer close to the plasma grid (first grid of the accelerator system) followed the transition from volume to surface dominated H- production starting with a Cs-free, cleaned source and subsequent evaporation of caesium, while the source has been operated at ITER relevant pressure of 0.3 Pa: Langmuir probes are used to determine the plasma potential, optical emission spectroscopy is used to follow the caesiation process, and cavity ring-down spectroscopy allows for the measurement of the H- density. The influence on the plasma during the transition from an electron-ion plasma towards an ion-ion plasma, in which negative hydrogen ions become the dominant negatively charged particle species, is seen in a strong increase of the H- density combined with a reduction of the plasma potential. A clear correlation of the extracted current densities (jH-, je) exists with the Cs emission.

  7. Parametric investigation of a thermally driven QCD Deconfining Phase Transition in a finite volume at zero chemical potential

    Science.gov (United States)

    Bensalem, S.; Ait El Djoudi, A.

    2016-10-01

    This work deals with a statistical description of a thermally driven deconfining phase transition (DPT) from a hadronic gas consisting of massless pions to a color-singlet Quark- Gluon Plasma (QGP), in a finite volume. The thermodynamical approach, within a coexistence model is used to investigate the Quantum Chromo-Dynamics DPT occurring between the two phases, at vanishing chemical potential. Considering the color singletness condition for the QGP phase, with massless up and down quarks, the exact total partition function of the studied system is obtained and then employed to calculate mean values of physical quantities, well characterizing the system near the transition. The finite-size effects on the DPT have been investigated through the study of the thermal behavior of the order parameter, the susceptibility and the second cumulant of the probability density. The similarity between the susceptibility and the second cumulant representing the variance is probed for the studied DPT and a parameterization of the variance is proposed for the first time.

  8. Application of Kissinger analysis to glass transition and study of thermal degradation kinetics of phenolic–acrylic IPNs

    Indian Academy of Sciences (India)

    S Goswami; K Kiran

    2012-08-01

    Degradation kinetics of sequential IPNs, based on novolac resin and poly (2-ethyl hexyl acrylate), are studied at linear heating rates of 2°C/min, 5°C/min, 10°C/min and 20°C/min by thermogravimetric analyser (TGA). Activation energy (a) and order () of thermal decomposition reaction for IPNs and pure phenolic resin are evaluated from TGA curves using differential method of Freeman and Carroll. Decrease in Tg with an increase of acrylate content in IPNs are seen. Lower activation energy (a'), as calculated by applying Kissinger equation, for the concerned transition of IPNs, compared to that of pure phenolic resin is quite evident from DSC study.

  9. Following the Evolution of Hard Sphere Glasses in Infinite Dimensions under External Perturbations: Compression and Shear Strain

    Science.gov (United States)

    Rainone, Corrado; Urbani, Pierfrancesco; Yoshino, Hajime; Zamponi, Francesco

    2015-01-01

    We consider the adiabatic evolution of glassy states under external perturbations. The formalism we use is very general. Here we use it for infinite-dimensional hard spheres where an exact analysis is possible. We consider perturbations of the boundary, i.e., compression or (volume preserving) shear strain, and we compute the response of glassy states to such perturbations: pressure and shear stress. We find that both quantities overshoot before the glass state becomes unstable at a spinodal point where it melts into a liquid (or yields). We also estimate the yield stress of the glass. Finally, we study the stability of the glass basins towards breaking into sub-basins, corresponding to a Gardner transition. We find that close to the dynamical transition, glasses undergo a Gardner transition after an infinitesimal perturbation.

  10. Correlation between transition percentage of minute volume (TMV%) and outcome of patients with acute respiratory failure.

    Science.gov (United States)

    Peng, Chung-Kan; Wu, Shu-Fen; Yang, Shih-Hsing; Hsieh, Chuan-Fa; Huang, Chung-Chih; Huang, Yuh-Chin T; Wu, Chin-Pyng

    2017-06-01

    We have previously shown in patients receiving adaptive support ventilation (ASV) that there existed a Transition %MinVol (TMV%) where the patient's work of breathing began to reduce. In this study, we tested the hypothesis that higher TMV% would be associated with poorer outcome in patients with acute respiratory failure. In this prospective observational study, we recruited patients with acute respiratory failure on ASV between December 2012 and September 2013 in a mixed ICU. The TMV% was determined by adjusting % MinVol until mandatory respiratory frequency was between 0 and 1breath/min. TMV% was measured on the first two days of mechanical ventilation. A total of 337 patients (age: 70±16years) were recruited. In patients whose TMV% increased between Day 1 and Day 2, aOR for mortality was 7.0 (95%CI=2.7-18.3, pTMV% decreased. In patients whose TMV% was unchanged between Day 1 and Day2, aOR for mortality was 3.91 (95%CI=1.80-8.22, pTMV% from Day 1 to Day 2 was associated with higher risk of in-hospital death. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Magnetic nature of the austenite-martensite phase transition and spin glass behaviour in nanostructured Mn2Ni1.6Sn0.4 melt-spun ribbons

    Science.gov (United States)

    Singh, Nidhi; Borgohain, Barsha; Srivastava, A. K.; Dhar, Ajay; Singh, H. K.

    2016-03-01

    Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been synthesised by melt spinning of the arc-melted bulk precursor. The single-phase ribbons crystallize into a cubic structure and exhibit very fine crystallite size of phase transition that begins at M S ≈ 249 K and finishes at M f ≈ 224 K. During warming, the reverse AFM-M to FM-A transitions begins at A s ≈ 240 K and finishes at A f ≈ 261 K. A re-entrant FM transition is observed in the M-phase at T_{{CM}} ≈ 145 K. These transitions are also confirmed by temperature-dependent resistivity ( ρ- T) measurements. The hysteretic behaviour of M- T and ρ- T in the temperature regime spanned by the A-M transition is a manifestation of the first-order phase transition. M- T and ρ- T data also provide unambiguous evidence in favour of spin glass at T AC susceptibility measurements, confirms the existence of canonical spin glass at T phase.

  12. 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

    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......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......, 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)...

  13. Phenylene ring dynamics in phenoxy and the effect of intramolecular linkages on the dynamics of some engineering thermoplastics below the glass transition temperature.

    Science.gov (United States)

    Arrese-Igor, Silvia; Arbe, Arantxa; Alegría, Angel; Colmenero, Juan; Frick, Bernhard

    2007-05-01

    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 pi flips and oscillation motions for phenylene rings. The associated time scales are broadly distributed with mean activation energies equal to 0.41 and 0.21eV , respectively. Finally, a comparative study with the literature shows that the dielectric and mechanical gamma 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. Important property of polymer spheres for the preparation of three-dimensionally ordered macroporous (3DOM) metal oxides by the ethylene glycol method: the glass-transition temperature.

    Science.gov (United States)

    Sadakane, Masahiro; Sasaki, Keisuke; Nakamura, Hiroki; Yamamoto, Takashi; Ninomiya, Wataru; Ueda, Wataru

    2012-12-21

    We demonstrate that the glass-transition temperature (T(g)) of a polymer sphere template is a crucial factor in the production of three-dimensionally ordered macroporous (3DOM) materials. Metal nitrate dissolved in ethylene glycol-methanol was infiltrated into the void of a face-centered, close-packed colloidal crystal of poly(methyl methacrylate) (PMMA)-based spheres. The metal nitrate reacts with EG to form a metal oxalate (or metal glycoxylate) solid (nitrate oxidation) in the void of the template when the metal nitrate-EG-PMMA composite is heated. Further heating converts metal oxalate to metal oxide and removes PMMA to form 3DOM materials. We investigated the effect of T(g) of PMMA templates and obtained clear evidence that the solidification temperature of the metal precursor solution (i.e., nitration oxidation temperature) should be lower than the T(g) of the polymer spheres to obtain a well-ordered 3DOM structure.

  15. Determination of glass transition temperature of reduced graphene oxide-poly(vinyl alcohol) composites using temperature dependent Fourier transform infrared spectroscopy

    Science.gov (United States)

    Mahendia, Suman; Heena; Kandhol, Geeta; Deshpande, Uday P.; Kumar, Shyam

    2016-05-01

    In the present work, structural properties of reduced graphene oxide (RGO) synthesized using modified Hummer's method and its composites with Poly(vinyl alcohol) (PVA) fabricated using solution-cast method have been studied. The structural properties of prepared samples have been systematically studied through UV-Visible absorption, Raman, Fourier Transform Infrared (FTIR) and Differential Scanning Calorimeter (DSC) spectroscopy. Infrared spectroscopy indicates the grafting of PVA chains with graphene layer through the formation of H-bonding linkage in the composites. Temperature-dependent FTIR spectra of PVA-RGO composite films were recorded to obtain the glass transition temperature (Tg) and to study its molecular origin. From these spectra the values of Tg were obtained using two-dimensional (2D) mapping of the first derivative of the absorbance intensity with respect to temperature (dA/dT), over the space of wavenumber and temperature. The value of Tg obtained for pure PVA increases from 78 °C to 92 °C after loading 0.5 wt.% of RGO in PVA and can be attributed to the strong H-bonding interaction between polymer chains and grafted solid surface of RGO. These results are in good agreement with those obtained from DSC analysis. This clearly indicates that the thermal behavior of PVA gets modified with loading of RGO.

  16. Physical, structural and optical characterization of silicate modified bismuth-borate-tellurite glasses

    Science.gov (United States)

    Berwal, Neelam; Dhankhar, Sunil; Sharma, Preeti; Kundu, R. S.; Punia, R.; Kishore, N.

    2017-01-01

    The quaternary glass system xSiO2-(80-x) Bi2O3sbnd 15B2O3sbnd 5TeO2 has been prepared by melt-quench technique. The amorphous nature of glass samples has been ascertained by X-ray diffraction patterns. The variations in density, molar volume and crystalline volume with glass compositions have been discussed. A non-linear change has been observed in glass transition temperature and optical band gap energy. Raman and FTIR spectral studies suggest that glass network is mainly built up of BO3, BO4, SiO4, and TeO3 structural units, whereas BiO3 exists as both network modifying [BiO6] octahedral as well as network forming [BiO3] pyramidal structural units. The values of optical band gap energy have been estimated from fitting of both Mott and Davis's model and Hydrogenic excitonic model (HEM) with experimental data of absorption spectra. The HEM model shows good agreement with experimentally observed absorption spectra, which indicates the exciton formation in studied glass system. The non-linear compositional change in optical band gap energy is related with the structural changes occurring in present glass samples. The Urbach energy has also been estimated. The range of metallization criterion suggests that prepared glasses may be considered as new nonlinear optical materials.

  17. Glass sealing

    Energy Technology Data Exchange (ETDEWEB)

    Brow, R.K.; Kovacic, L.; Chambers, R.S. [Sandia National Labs., Albuquerque, NM (United States)

    1996-04-01

    Hernetic glass sealing technologies developed for weapons component applications can be utilized for the design and manufacture of fuel cells. Design and processing of of a seal are optimized through an integrated approach based on glass composition research, finite element analysis, and sealing process definition. Glass sealing procedures are selected to accommodate the limits imposed by glass composition and predicted calculations.

  18. Spin glass transition in the rhombohedral LiNi{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bie, Xiaofei; Yang, Xu [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China); Han, Bing [College of Physics, Jilin University, Changchun 130012 (China); Chen, Nan; Liu, Lina; Wei, Yingjin; Wang, Chunzhong [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China); Chen, Hong [College of Physics, Beihua University, Jilin 132013 (China); Du, Fei, E-mail: dufei@jlu.edu.cn [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China); Chen, Gang [Key Laboratory of Advanced Batteries Physics and Technology, Ministry of Education, College of Physics, Jilin University, Changchun 130012 (China)

    2013-09-25

    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{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 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.

  19. Effect of drying methods of microencapsulated Lactobacillus acidophilus and Lactococcus lactis ssp. cremoris on secondary protein structure and glass transition temperature as studied by Fourier transform infrared and differential scanning calorimetry.

    Science.gov (United States)

    Dianawati, Dianawati; Mishra, Vijay; Shah, Nagendra P

    2013-03-01

    Protective mechanisms of casein-based microcapsules containing mannitol on Lactobacillus acidophilus and Lactococcus lactis ssp. cremoris, changes in their secondary protein structures, and glass transition of the microcapsules were studied after spray- or freeze-drying and after 10 wk of storage in aluminum foil pouches containing different desiccants (NaOH, LiCl, or silica gel) at 25°C. An in situ Fourier transform infrared analysis was carried out to recognize any changes in fatty acids (FA) of bacterial cell envelopes, interaction between polar site of cell envelopes and microcapsules, and alteration of their secondary protein structures. Differential scanning calorimetry was used to determine glass transition of microcapsules based on glass transition temperature (T(g)) values. Hierarchical cluster analysis based on functional groups of cell envelopes and secondary protein structures was also carried out to classify the microencapsulated bacteria due to the effects of spray- or freeze-drying and storage for 10 wk. The results showed that drying process did not affect FA and secondary protein structures of bacteria; however, those structures were affected during storage depending upon the type of desiccant used. Interaction between exterior of bacterial cell envelopes and microencapsulant occurred after spray- or freeze-drying; however, these structures were maintained after storage in foil pouch containing sodium hydroxide. Method of drying and type of desiccants influenced the level of similarities of microencapsulated bacteria. Desiccants and method of drying affected glass transition, yet no T(g) ≤25°C was detected. This study demonstrated that the changes in FA and secondary structures of the microencapsulated bacteria still occurred during storage at T(g) above room temperature, indicating that the glassy state did not completely prevent chemical activities. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights

  20. Effect of Bi2O3 on structural, optical, and other physical properties of semiconducting zinc vanadate glasses

    Science.gov (United States)

    Punia, R.; Kundu, R. S.; Hooda, J.; Dhankhar, S.; Dahiya, Sajjan; Kishore, N.

    2011-08-01

    Zinc bismuth vanadate glasses with compositions 50V2O5-xBi2O3-(50-x) ZnO have been prepared using a conventional melt-quenching method and the solubility limit of Bi2O3 in zinc vanadate glass system has been investigated using x-ray diffraction. Density has been measured using Archimedes' principle; molar volume (Vm) and crystalline volumes (Vc) have also been estimated. With an increase in Bi2O3 content, there is an increase in density and molar volume of the glass samples. The glass transition temperature (Tg) and Hurby coefficient (Kgl) have been determined using differential scanning calorimetry (DSC) and are observed to increase with increase in Bi2O3 content (i.e., x), up to x = 15, thereby indicating the structural modifications and increased thermal stability of zinc vanadate glasses on addition of Bi2O3. FTIR spectra have been recorded and the analysis of FTIR shows that the structure depends upon the Bi2O3 content in the glass compositions. On addition of Bi2O3 into the zinc vanadate system, the structure of V2O5 changes from VO4 tetrahedral to VO5 trigonal bi-pyramid configuration. The optical parameters have been calculated by using spectroscopic ellipsometry for bulk oxide glasses (perhaps used first time for bulk glasses) and optical bandgap energy is found to increase with increase in Bi2O3 content.