Journal articles: 'Vogel-Fulcher model'

1

EDWARDS, S. F. "THE EDWARDS MODEL: THE GLASS TRANSITION." International Journal of Modern Physics B 06, no. 10 (May 20, 1992): 1587–94. http://dx.doi.org/10.1142/s0217979292000785.

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The structure of the transport coefficients in the approach to the glass transition is characterized by an essential singularity in their behaviour as functions of the temperature, variously known as the Vogel-Fulcher or Dolittle or Williams-Landel-Ferry laws. This behaviour can be derived directly in certain simple models notably a glass of liquid crystal polymers where mean field theory may be applied. In this paper a new class of closed expressions for transport coefficients are derived and it is shown that they can be used to derive the Vogel-Fulcher law.

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Shiri, Parisa, Earl Jon S. Dacanay, Brennan Hagen, and Loren G. Kaake. "Vogel–Tammann–Fulcher model for charging dynamics in an organic electrochemical transistor." Journal of Materials Chemistry C 7, no. 41 (2019): 12935–41. http://dx.doi.org/10.1039/c9tc02563d.

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The dynamics of organic electrochemical transistors were studied using in situ infrared spectroscopy. The diffusivity of mixed ion-carrier pairs were quantified and fit with the VTF equation by considering the enthalpy of mixing of the process.

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Gan, Lei, Chaobin Lai, and Huihui Xiong. "Non-Arrhenius Viscosity Models for Molten Silicate Slags with Constant Pre-Exponential Parameter: A Comparison to Arrhenius Model." High Temperature Materials and Processes 35, no. 3 (March 1, 2016): 261–67. http://dx.doi.org/10.1515/htmp-2014-0197.

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AbstractThe accuracies of molten slag viscosity fitting and low-temperature extrapolation were compared between four two-variable models: Arrhenius, Weymann–Frenkel (WF), and Vogel–Fulcher–Tammann (VFT) and Mauro, Yue, Ellison, Gupta and Allan (MYEGA) models with constant pre-exponential parameter, based on a molten slag viscosity database consisting of over 800 compositions and 5,000 measurements. It is found that over wide ranges of pre-exponential parameter, the VFT and MYEGA models have lower viscosity fitting errors and much higher low-temperature viscosity extrapolation accuracies than Arrhenius and WF models. The pre-exponential parameter values of –2.8 for VFT and –2.3 for MYEGA are recommended.

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Migahed, M. D., M. T. Ahmed, and A. E. Kotp. "Computation of TSDC Peak Parameters in Amorphous Polymers using Vogel‐Tammann‐Fulcher Relaxation Model." Journal of Macromolecular Science, Part B 44, no. 1 (February 8, 2005): 43–53. http://dx.doi.org/10.1081/mb-200044579.

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Mahiuddin, Sekh. "Mixed alkali effect in 0.2[xKNO3 + (1 − x)NaNO3] + 0.8glycerol systems." Canadian Journal of Chemistry 72, no. 11 (November 1, 1994): 2286–90. http://dx.doi.org/10.1139/v94-291.

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Density, electrical conductivity, and fluidity of 0.2[xKNO3 + (1 − x)NaNO3] + 0.8glycerol systems were measured as functions of temperature (363.15 to428.15 K) and composition (0.0to 1.0 mole fraction). Densities were linear functions of temperature. The temperature dependence of conductivity and fluidity has been analysed by using the Vogel–Tammann–Fulcher (VTF) equation. Deviation from additivity has been observed in the electrical conductivity, fluidity isotherms to a lesser extent, and in electrical conductivity under isofluidity condition. The onset of the mixed alkali effect (MAE) in the present system has been explained by the anion polarization model.

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Zhou, Lejun, and Wanlin Wang. "Study of the Viscosity of Mold Flux Based on the Vogel–Fulcher–Tammann (VFT) Model." Metallurgical and Materials Transactions B 48, no. 1 (October 17, 2016): 220–26. http://dx.doi.org/10.1007/s11663-016-0835-2.

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Shankaraiah, N., K. P. N. Murthy, Turab Lookman, and S. R. Shenoy. "Athermal Martensites, Temperature-Time-Transformation Diagrams and Thermal Hysteresis: Monte Carlo Simulations of Strain Pseudospins." Solid State Phenomena 185 (February 2012): 31–33. http://dx.doi.org/10.4028/www.scientific.net/ssp.185.31.

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We explore the kinetics of a three-state strain pseudospin model for a square/rectangle ferroelastic transition, described by a temperature dependent hamiltonian without quenched disorder, using temperature quench Monte Carlo simulations. The model hamiltonian includes power law anisotropic long range interactions, which lock the domain walls in a symmetry breaking diagonal direction. In athermal parameter regime, there are fast conversions at the athermal transition temperature, but with delay tails above it, as in experiment. The conversion delay tails have a Vogel-Fulcher divergence at transition to austenite. The incubation delays and their insensitivity to elastic energy scales are attributed to entropy barriers. Temperature cycling shows hysteretic behavior in physical quantities.

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Aniya, Masaru, and Masahiro Ikeda. "Viscosity of Metallic Glass Forming Liquids: Analysis Based on Bond Strength-Coordination Number Fluctuations." Materials Science Forum 638-642 (January 2010): 1621–26. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1621.

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A model that describes the viscous behavior in terms of the mean values of the bond strength, the coordination number, and their fluctuations of the structural units that form the melt has been proposed by one of the authors. In the present study, the viscous behavior of several metallic glass forming systems are analyzed by using the model. From the analysis, microscopic information such as the number of bonds that must be broken to observe the viscous flow is obtained. It is also shown that when the magnitudes of energy and coordination number fluctuations are equal, the behavior of the viscosity described by our model corresponds perfectly to the behavior described by the Vogel-Fulcher-Tammann (VFT) equation.

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Civan, Faruk. "Effective Correlation of Stress and Thermal Effects on Porosity and Permeability of Naturally Fractured Formations by a Modified Power Law." SPE Journal 24, no. 05 (September 9, 2019): 2378–97. http://dx.doi.org/10.2118/198893-pa.

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Summary Effective theory and methodology are proposed and validated for accurate correlation of stress–dependent petrophysical properties of naturally fractured or induced–fractured reservoir formations by means of a matrix/fracture dual–compressibility treatment. Inspection of various experimental data indicates a sudden change in trends at a certain critical net effective stress in the stress dependence of petrophysical properties of porous rocks as a result of a stress shock caused by the opening or closing of fractures. The variation of petrophysical properties in fractured–rock formations subjected to stress loading/unloading and thermally induced stress occurs mainly by deformation of the fractures below the critical effective stress and the deformation of the matrix above the critical effective stress. The alteration of petrophysical properties and a slope discontinuity might also be experienced when the stress exceeds the onset of other rock–alteration/damaging processes, such as pore collapsing and grain crushing. Proper formulations of the relevant processes and special correlation methods are presented in a manner to capture this nature of the petrophysical experimental data obtained by testing of cores extracted from naturally fractured or induced–fractured reservoir–rock formations. The dependency of porosity and permeability of fractured–rock samples under stress because of thermal, hydraulic, and mechanical effects is represented accurately by a modified–power–law equation derived from a kinetics model as confirmed by effective correlations of various experimental data. It is shown that this new model represents the thermal effect better than the frequently used Arrhenius (1889) equation and Vogel–Tammann–Fulcher (VTF) equation (Vogel 1921; Fulcher 1925; Tammann and Hesse 1926).

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Ikeda, Masahiro, and Masaru Aniya. "Understanding the Vogel–Fulcher–Tammann law in terms of the bond strength–coordination number fluctuation model." Journal of Non-Crystalline Solids 371-372 (July 2013): 53–57. http://dx.doi.org/10.1016/j.jnoncrysol.2013.04.034.

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Metatla, Noureddine, and Armand Soldera. "The Vogel−Fulcher−Tamman Equation Investigated by Atomistic Simulation with Regard to the Adam−Gibbs Model." Macromolecules 40, no. 26 (December 2007): 9680–85. http://dx.doi.org/10.1021/ma071788+.

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12

Liu, G. D., J. P. Wu, H. M. Dong, and H. Q. Zhang. "Nonlinear modification of vogel-fulcher-tamman (VFT) model and its application in enthalpy relaxation of glassy polystyrene." Journal of Non-Crystalline Solids 528 (January 2020): 119761. http://dx.doi.org/10.1016/j.jnoncrysol.2019.119761.

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13

CORBERI, F., and A. CONIGLIO. "LACK OF EQUILIBRATION IN A MODEL FOR CONTINUOUSLY SUPERCOOLED LIQUIDS." Fractals 11, supp01 (February 2003): 109–18. http://dx.doi.org/10.1142/s0218348x0300177x.

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We consider the dynamics of supercooled fluids subject to a continuous quenching procedure, with cooling rate r = dT(t)/dt. The analysis is carried out analytically in the framework of a mean field schematic model recently introduced.1 We show the existence of a glass temperature Tg(r) below which the system falls out of equilibrium. Tg(r) approaches logarithmically in r the ideal glass temperature T0 = lim r→0Tg(r), where the relaxation time diverges á la Vogel-Fulcher, similarly to some experimental observations. Well above Tg(r) a simple fluid behavior is observed. As Tg is approached from above a characteristic wave vector kd divides an high momenta equilibrated region, where a fluid-like behavior is obeyed, from the non thermalized modes with k < kd, for which time translational invariance lacks. Below Tg the system is found in a globally off-equilibrium glassy state characterized by a logarithmic decay of the density fluctuations and aging. The two time correlator decays as an enhanced power law.

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14

Bartoš, Josef. "A Phenomenological Description of the PALS Response in Glass - Forming Systems." Materials Science Forum 607 (November 2008): 48–52. http://dx.doi.org/10.4028/www.scientific.net/msf.607.48.

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A phenomenological description of the ortho-positronium (o-Ps) response from positron annihilation spectroscopy (PALS) and the dynamics from viscosity studies on two typical glass-forming compounds within the framework of the two-order parameter (TOP) model is presented. The dynamical data are accounted for by the modified Vogel – Fulcher – Tamman - Hesse (M-VFTH) equation. Subsequently, the quasi-sigmoidal course of the o-Ps lifetime, τ3, with or without the high-temperature plateau region as a function of the temperature over a wide temperature range can be described by an effective free volume version of the TOP model. This simultaneous description suggests a close relationship between the PALS response and the dynamics of supercooled liquids and seems to support the liquid - like and solid - like domain physical picture of all the three physical states of the disordered phase of the condensed systems.

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15

Safarov, J., G. Huseynova, M. Bashirov, E. Hassel, and I. M. Abdulagatov. "Viscosity of 1-ethyl-3-methylimidazolium methanesulfonate over a wide range of temperature and Vogel–Tamman–Fulcher model." Physics and Chemistry of Liquids 56, no. 6 (September 25, 2017): 703–17. http://dx.doi.org/10.1080/00319104.2017.1379080.

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16

Islam, Shakira S., and Kochi Ismail. "Mixed alkali effect in sodium thiosulfate pentahydrate melt." Canadian Journal of Chemistry 66, no. 2 (February 1, 1988): 242–45. http://dx.doi.org/10.1139/v88-040.

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Density and electrical conductance measurements of 0.35[XNaNO3 + (1 − X)KNO3] + 0.65Na2S2O3•5H2O melt were made as functions of temperature and X. Molar volume, V, is found to be additive. The percent deviation of Vext (extrapolated V of the pure solute from the plot of V vs. total added alkali ion fraction) from Vcal (calculated V of the pure solute from its high temperature density data) increases monotonically as the amount of NaNO3 in the hydrate melt increases, thereby manifesting a "structure-forming" tendency of NaNO3. The non-Arrhenius temperature dependence of molar conductance, Λ is analyzed in terms of the Vogel–Tammann–Fulcher (VTF) equation. Mixed alkali effect (MAE) has been observed on Λ and T0 (ideal glass transition temperature). A competitive polarization model has been used to explain the MAE on Λ.

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17

Saeed, Maryam A. M., and Omed Gh Abdullah. "Effect of High Ammonium Salt Concentration and Temperature on the Structure, Morphology, and Ionic Conductivity of Proton-Conductor Solid Polymer Electrolytes Based PVA." Membranes 10, no. 10 (September 28, 2020): 262. http://dx.doi.org/10.3390/membranes10100262.

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Polyvinyl alcohol (PVA) based proton-conducting solid polymer electrolyte was prepared with a high salt concentration of ammonium nitrate (NH4NO3) by the technique of solvent casting. From the X-ray diffraction studies, the semicrystalline nature of PVA with the inclusion of NH4NO3 was studied. XRD analysis indicates that the highest ion conductive sample exhibits the minimum crystalline nature. The decreasing trend of Jonscher-exponent with temperature rise reveals that the present system is insured by the correlated barrier hopping (CBH) model. The maximum room temperature conductivity was found to be 5.17 × 10−5 S/cm for PVA loaded 30 wt.% of NH4NO3. The ionic transport of the proton-conducting solid polymer electrolyte was studied at the temperature range of 303–353 K. The conductivity-temperature relationship of the systems was analyzed using both the Arrhenius and Vogel–Tammann–Fulcher (VTF) models to explain the ionic hopping mechanism for the system.

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Schlenz, U., A. Dölle, and H. G. Hertz. "Molecular Motion in Liquids: The Partially Rigid Molecule 1,2,3,4-Tetrahydro-5,6-Dimethyl-1,4-Methanonaphthalene. Temperature Dependence of 13C Magnetic Relaxation and Correlation Times." Zeitschrift für Naturforschung A 50, no. 7 (July 1, 1995): 631–42. http://dx.doi.org/10.1515/zna-1995-0703.

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For the hydrocarbon 1,2,3,4-tetrahydro-5,6-dimethyl-1,4-methanonaphthalene (5,6-Me2-THMN) 13C longitudinal relaxation times and NOE factors were measured over a wide temperature range at frequencies of 22.63 and 100.62 MHz. Additionally, 13C transversal relaxation times were measured at 100.62 MHz. The relaxation data show that the dispersion region is already reached at moderate temperatures. The experimental data were modeled by the combination of the Vogel- Fulcher-Tammann ansatz and a scaling of the dipolar coupling constant with a factor of 0.70. From the fit of the data also activation parameters of the rotational motion of the molecules were obtained. Although the molecules of 5,6-Me2-THMN have a rigid structure (except the two internally rotating methyl groups), the model of the rotational diffusion of rigid bodies does not satisfactorily describe the relaxation data.

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Mahiuddin, Sekh. "Mixed alkali effect in sodium thiocyanate–potassium thiocyanate – acetamide melt systems." Canadian Journal of Chemistry 74, no. 5 (May 1, 1996): 760–65. http://dx.doi.org/10.1139/v96-083.

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Electrical conductivity and molar volume of the 0.25[xNaSCN + (1 −x)KSCN] + 0.75CH3CONH2 systems were measured as functions of temperature [Formula: see text] and composition (x = 0.0 – 1.0 mol fraction). Temperature dependence of the electrical conductivity was non-Arrhenius in nature and has been analysed by using the Vogel–Tammann–Fulcher (VTF) equation. Molar volume data were fitted to an equation similar to the VTF equation based on the free volume model. Molar volumes and intrinsic volumes were found to be additive in nature. Electrical conductivity isotherms deviate from linearity in different fashion for different temperature regions. The onset of the mixed alkali effect is governed by the anion polarization effect, by a contribution of the auto-dissociated molten acetamide, and by polymeric-type solvated ions. Key words: electrical conductivity, sodium thiocyanate, potassium thiocyanate, acetamide, mixed alkali effect.

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20

Kalita, Gautam, Nashiour Rohman, and Sekh Mahiuddin. "Electrical Conductivity, Viscosity and Molar Volume of Potassium Nitrate - Sodium Nitrate in Cadmium Nitrate Tetrahydrate Melt." Australian Journal of Chemistry 51, no. 3 (1998): 201. http://dx.doi.org/10.1071/c97007.

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The electrical conductivities, viscosities and molar volumes of the 0·3[xKNO3+(1 – x)NaNO3]+ 0·7Cd(NO3)2.4·4H2O systems were measured as functions of temperature (293·15 ≤ T/K ≤ 363·15) and composition (x = 0·0 to 1·0 mole fraction). The temperature dependence of the electrical conductivity and viscosity was non-Arrhenius in nature and has been analysed by using the Vogel–Tammann–Fulcher (VTF) equation. Both conductivity and viscosity vary non-linearly with the molar volume and have been explained by using VTF-type equations based on the free volume model. In the present system the molar volume and the intrinsic volume are additive. A significant mixed alkali effect has been observed in the normalized electrical conductivity and viscosity and in the electrical conductivity at the isofluidity condition. The variation of the electrical conductivity is governed by the mobility of the potassium ions. The onset of the mixed alkali effect has been explained by the anion polarization model.

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Wang, L. W., and H. J. Fecht. "A kinetic model for liquids: Relaxation in liquids, origin of the Vogel–Tammann–Fulcher equation, and the essence of fragility." Journal of Applied Physics 104, no. 11 (December 2008): 113538. http://dx.doi.org/10.1063/1.3033521.

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Kozmidis-Petrovic, Ana. "Equations of viscous flow of silicate liquids with different approaches for universality of high temperature viscosity limit." Processing and Application of Ceramics 8, no. 2 (2014): 59–68. http://dx.doi.org/10.2298/pac1402059k.

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The Vogel-Fulcher-Tammann (VFT), Avramov and Milchev (AM) as well as Mauro, Yue, Ellison, Gupta and Allan (MYEGA) functions of viscous flow are analysed when the compositionally independent high temperature viscosity limit is introduced instead of the compositionally dependent parameter ??. Two different approaches are adopted. In the first approach, it is assumed that each model should have its own (average) hightemperature viscosity parameter ??. In that case, ?? is different for each of these three models. In the second approach, it is assumed that the high-temperature viscosity is a truly universal value, independent of the model. In this case, the parameter ?? would be the same and would have the same value: log ?? = ?1.93 dPa?s for all three models. 3D diagrams can successfully predict the difference in behaviour of viscous functions when average or universal high temperature limit is applied in calculations. The values of the AM functions depend, to a greater extent, on whether the average or the universal value for ?? is used which is not the case with the VFT model. Our tests and values of standard error of estimate (SEE) show that there are no general rules whether the average or universal high temperature viscosity limit should be applied to get the best agreement with the experimental functions.

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Tuncer, Enis. "Change in dielectric relaxation with the presence of water in highly filled composites." Journal of Advanced Dielectrics 07, no. 05 (October 2017): 1750033. http://dx.doi.org/10.1142/s2010135x17500333.

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It is important to determine the dielectric characteristics of semiconductor encapsulation materials based on epoxy resins. We employed the dielectric spectroscopy technique to investigate the dielectric relaxation in the presence of water and how it changes the relaxation. It was observed that the dielectric relaxation of the material was significantly influenced by absorbed water, the local segmental motion (also known as Johari–Goldstein ([Formula: see text]) relaxation) was influenced most by the presence of the water, it was modified by the wet sample compared to dry one, and required high activation energy. The relaxation related to the glass transition was contributed by the cooperative motion (the [Formula: see text]-relaxation) of the epoxy resin system. The [Formula: see text]-relaxation was shifted to a low temperature in the wet sample compared to dry one. The relaxation was modeled with a clear Vogel–Fulcher–Tammann–Hesse (VFTH) behavior; the Vogel temperature of the wet sample was 8[Formula: see text]K lower than the dry sample. The presence of water acts as a plasticizer for the molecular relaxation, and speed-up the cooperative process. The measured data were also used to estimate the electrical properties of the resin system by employing an effective-medium model together with a porous media continuum model by taking into account the physical properties of the system. It is already known that the influence of water in semiconductor packaging is important in sensitive applications. The presented measurements and the analysis method would be appreciated within the semiconductor packaging community to improve material selection and performance evaluation efforts.

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Casalini, R., M. Paluch, T. Psurek, and C. M. Roland. "Temperature and pressure dependences of the structural dynamics: an interpretation of Vogel–Fulcher behavior in terms of the Adam–Gibbs model." Journal of Molecular Liquids 111, no. 1-3 (April 2004): 53–60. http://dx.doi.org/10.1016/s0167-7322(03)00260-5.

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Špitalský, Z., S. N. Georga, C. A. Krontiras, and C. Galiotis. "Dielectric Spectroscopy and Tunability of Multi-Walled Carbon Nanotube / Epoxy Resin Composites." Advanced Composites Letters 19, no. 6 (November 2010): 096369351001900. http://dx.doi.org/10.1177/096369351001900601.

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The dielectric response of oxidized multi-walled carbon nanotube / epoxy resin composites, is investigated with respect to filler content concentration, over a wide temperature and frequency range. Specimens, below the percolation threshold, exhibit similar behaviour to that of the neat epoxy. Two relaxation modes are observed in the low temperature region, attributed to the re-arrangement of small parts of the polymer chain (γ-mode) and the reorientation of polar side groups (β-mode) respectively, where in the high temperature region the evolution of the α-mode is present. Direct current (DC) conduction follows the Vogel – Tamann - Fulcher equation as expected. The dielectric response of specimens, above the percolation threshold, follows the “Random Free Energy Barrier Model”. DC conductivity exhibits Arrhenius temperature dependence with two distinct regions. The activation energies of both regions were evaluated. The contact resistance between two adjacent carbon nanotubes was also calculated. The effective dielectric constant as well as the capacitance of the specimens, above the percolation threshold, can be modulated by means of an applied DC bias voltage.

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Ikeda, Masahiro, and Masaru Aniya. "Bond Strength—Coordination Number Fluctuation Model of Viscosity: An Alternative Model for the Vogel-Fulcher-Tammann Equation and an Application to Bulk Metallic Glass Forming Liquids." Materials 3, no. 12 (December 10, 2010): 5246–62. http://dx.doi.org/10.3390/ma3125246.

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Pink, David A., Marjorie Ladd-Parada, Alejandro G. Marangoni, and Gianfranco Mazzanti. "Crystal Memory near Discontinuous Triacylglycerol Phase Transitions: Models, Metastable Regimes, and Critical Points." Molecules 25, no. 23 (November 30, 2020): 5631. http://dx.doi.org/10.3390/molecules25235631.

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It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been detected. Solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered. We outlined a mathematical model, with a single phase transition, that shows how the time-temperature observations can be explained, makes predictions, and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. A plot of the lifetime of a metastable state versus temperature, using the modified VFT equation, agrees with recent time-temperature data. The model can be falsified through its predictions: the model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime. The model predicts that the phenomenon of “crystal memory” will not be observed unless the system is cooled from a superheated metastable regime associated with a discontinuous phase transition.

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Naik, Jagadish, RF Bhajantri, Sunil G. Rathod, and Ishwar Naik. "Proton conducting diazanium hydrogen phosphate/poly(vinyl alcohol) electrolytes: Transport, electrical, thermal, structural, and optical properties." Journal of Elastomers & Plastics 51, no. 5 (July 19, 2018): 390–405. http://dx.doi.org/10.1177/0095244318788128.

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Proton conducting solid polymer electrolyte films, which are composed of diazanium hydrogen phosphate (DAHP) and poly(vinyl alcohol) (PVA), were prepared by a solution casting method. The prepared films were characterized by ultraviolet-visible, X-ray diffraction, and differential scanning calorimetry. The optical activation energy and band gap increases with increase in DAHP content in PVA. The direct current (DC) and alternating current (AC) conductivity studies have been carried out using an impedance analyzer. The sample containing 15 wt% DAHP shows highest AC conductivity of the order of 10−4 S cm−1 and DC conductivity about 4.27 × 10−7 S cm−1 at ambient conditions. The crystallinity has decreased and glass transition temperature ( T g) has increased with increase in DAHP content. The Williams–Landel–Ferry and Vogel–Fulcher–Tamman equations were used to calculate dynamic fragility ( m) and apparent activation energy ( E g) from T g values. The Rice and Roth model was successfully applied to determine the transport parameters for DAHP/PVA electrolytes. This article mainly focused on understanding the contribution of different parameters to conductivity phenomenon in solid polymer electrolytes.

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Aziz, Karim, Brza, Abdulwahid, Saeed, Al-Zangana, and Kadir. "Ion Transport Study in CS: POZ Based Polymer Membrane Electrolytes Using Trukhan Model." International Journal of Molecular Sciences 20, no. 21 (October 23, 2019): 5265. http://dx.doi.org/10.3390/ijms20215265.

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In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF3SO3)2) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes composed of chitosan (CS) and poly (2-ethyl-2-oxazoline) (POZ). From X-ray diffraction (XRD) patterns, improvement in amorphous phase for the blend samples has been observed in comparison to the pure state of CS. From impedance plot, bulk resistance (Rb) was found to decrease with increasing temperature. Based on direct current (DC) conductivity (σdc) patterns, considerations on the ion transport models of Arrhenius and Vogel–Tammann–Fulcher (VTF) were given. Analysis of the dielectric properties was carried out at different temperatures and the obtained results were linked to the ion transport mechanism. It is demonstrated in the real part of electrical modulus that chitosan-salt systems are extremely capacitive. The asymmetric peak of the imaginary part (Mi) of electric modulus indicated that there is non-Debye type of relaxation for ions. From frequency dependence of dielectric loss (ε″) and the imaginary part (Mi) of electric modulus, suitable coupling among polymer segmental and ionic motions was identified. Two techniques were used to analyze the viscoelastic relaxation dynamic of ions. The Trukhan model was used to determine the diffusion coefficient (D) by using the frequency related to peak frequencies and loss tangent maximum heights (tanδmax). The Einstein–Nernst equation was applied to determine the carrier number density (n) and mobility. The ion transport parameters, such as D, n and mobility (μ), at room temperature, were found to be 4 × 10−5 cm2/s, 3.4 × 1015 cm−3, and 1.2 × 10−4 cm2/Vs, respectively. Finally, it was shown that an increase in temperature can also cause these parameters to increase.

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Revil, André, Antoine Coperey, Deqiang Mao, Feras Abdulsamad, Ahmad Ghorbani, Magali Rossi, and Dominique Gasquet. "Induced polarization response of porous media with metallic particles — Part 8: Influence of temperature and salinity." GEOPHYSICS 83, no. 6 (November 1, 2018): E435—E456. http://dx.doi.org/10.1190/geo2018-0089.1.

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We have investigated the influence of temperature and salinity upon the spectral induced polarization of 10 samples including rocks with their mineralization (galena, chalcopyrite) plus sand mixed with semiconductors such as magnetite grains, graphite, and pyrite cubes of two different sizes. Measurements are made in a temperature-controlled bath with a high-precision impedance meter and using NaCl solutions. We cover the temperature range 5°C−50°C and the frequency range [Formula: see text] to 45 kHz. For one large pyrite cube, we also investigated six salinities from 0.1 to [Formula: see text] (at 25°C, NaCl) and three salinities for graphite. The spectra are fitted with a Cole-Cole complex parametric conductivity model for which we provide a physical meaning to the four Cole-Cole parameters. As expected, the Cole-Cole exponent and the chargeability are independent of the temperature and salinity. The instantaneous and steady state (direct current [DC]) conductivities depend on the salinity and temperature. This temperature dependence can be fitted with an Arrhenius law (combining the Stokes-Einstein and Vogel-Fulcher-Tammann equations) with an activation energy in the range of [Formula: see text]. This activation energy is the same as for the bulk pore-water conductivity demonstrating the control by the background electrolyte of these quantities, as expected. The instantaneous and DC conductivities depend on the salinity in a predictable way. The Cole-Cole relaxation time decreases with the temperature and decreases with the salinity. This behavior can be modeled with an Arrhenius law with an apparent activation energy of [Formula: see text]. A finite-element model is used further to analyze the mechanisms of polarization, and it can reproduce the temperature and salinity dependencies observed in the laboratory.

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31

Permanadewi, Indrasukma, Andri Cahyo Kumoro, Dyah Hesti Wardhani, and Nita Aryanti. "Mathematical Approach for Estimation of Alginate-Iron Salt Solutions Viscosity at Various Solid Concentrations and Temperatures." Current Research in Nutrition and Food Science Journal 9, no. 1 (April 27, 2021): 75–87. http://dx.doi.org/10.12944/crnfsj.9.1.08.

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Alginate has been widely used in the pharmaceutical industries as tablet binder and disintegrant, release agent and controlled release drug delivery system. Whereas in the food industries, alginate is generally employed as thickener, emulsifier, stabilizer, texturizer, formulation aid, firming agent, flavor adjuvant, and surface-active agent. As one of the important raw materials in the functional food preparation, iron is hard to manage due to its vulnerability to oxidization, degradation and possesses a strong unique aroma. Considering its superior coating and release properties, alginate gel can be the best choice to preserve iron from various undesirable effects. Unfortunately, there has been lack information in the published literature to estimate the effect of temperature, concentration, and stirring time on the mechanical properties of alginate. Although many mathematical models have been developed based on these factors to predict the viscosity of the alginate-Fe solutions used as feed in spray drying application, no clear information have been reported for their accuracy. This study aims to examine four physical models for their suitability in estimating alginate-Fe solution viscosity, namely the Walther, Mark Houwink, Vogel – Tamman – Fulcher (VTF), and Intrinsic models. Prior to model validation, alginate-Fe solutions containing alginate: Fe (2:1) mass ratio were prepared. They were heated to desirable temperatures (30°, 45°, 60°, and 75°C), stirred for various stirring times (0 to 60 minutes), and subjected to viscosity measurement. The results exhibited that the viscosity of alginate-Fe solution with 5% alginate concentration stirred for 15 minutes at 30°C reached 320 cP. Whereas the viscosity of Alginate-Fe solution with 1% (m/m) concentration at the same temperature and stirring time was only 250 cP. This observation suggested that a higher alginate solution concentration leads to a higher the viscosity. As expected, a higher temperature and longer stirring time resulted in the decline of the Alginate-Fe solution viscosity. Although the proposed models demonstrated the similar trend, it can be concluded that the Walther model was proven to be the most accurate model used for the prediction of the Alginate-Fe solution viscosity compared to the other models as shown by its highest R2 value, which was 0.987.

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Sodaee, Tahmineh, Ali Ghasemi, and Reza Shoja Razavi. "Non-interacting Neél–Brown or interacting Vogel–Fulcher models in magnetic CoFe2−Gd O4 nanocrystals." Journal of Magnetism and Magnetic Materials 417 (November 2016): 11–20. http://dx.doi.org/10.1016/j.jmmm.2016.05.056.

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Ehsani, Mohammad Hoseein, Parviz Kameli, Mohammad Ebrahim Ghazi, and Fereidon Saadat Razavi. "An Investigation on Magnetic Interacting La_0.6Sr_0.4MnO₃ Nanoparticles." Advanced Materials Research 829 (November 2013): 712–16. http://dx.doi.org/10.4028/www.scientific.net/amr.829.712.

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Nanoparticles of La0.6Sr0.4MnO3 (LSMO) with an equivalent average particle size of ~ 20nm were synthesized by nitrate-complex auto-ignition method. The structural and magnetic properties were investigated systematically. The X-Ray diffraction study coupled with the Rietveld refinement of XRD data showed that sample crystallize in a rhombohedral structure with space group of R-3C. The stretching and bending modes in Fourier transform infrared (FTIR) spectroscopy is observed which indicates the formation of the perovskite structure of LSMO. The nature of DC magnetization versus field M(H) plot for sample resembles qualitatively with ferromagnetic (FM) systems. The AC-susceptibility data obtained at different frequencies confirmed the presence of a frequencydependent freezing temperature around room temperature. Based on the interparticle interaction strength and phenomenological models (Neel-Brown, Vogel-Fulcher and Critical slowing down) the magnetic dynamic behavior of nanoparticles was characterized. By fitting the experimental data with mentioned models the possibility existence of superparamagnetic/spin glass states were considered. The obtained values from fitting performance showed that there is a strong interaction between magnetic nanoparticles of LSMO.

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34

Almessiere, Munirah Abdullah, Y. Slimani, H. Güngüneş, S. Ali, A. Manikandan, I. Ercan, A. Baykal, and A. V. Trukhanov. "Magnetic Attributes of NiFe2O4 Nanoparticles: Influence of Dysprosium Ions (Dy3+) Substitution." Nanomaterials 9, no. 6 (May 31, 2019): 820. http://dx.doi.org/10.3390/nano9060820.

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This paper reports the influence of dysprosium ion (Dy3+) substitution on the structural and magnetic properties of NiDyxFe2−xO4 (0.0 ≤ x ≤ 0.1) nanoparticles (NPs) prepared using a hydrothermal method. The structure and morphology of the as-synthesized NPs were characterized via X-ray diffraction (XRD), scanning and transmission electron microscope (SEM, and TEM) analyses. 57Fe Mössbauer spectra were recorded to determine the Dy3+ content dependent variation in the line width, isomer shift, quadrupole splitting, and hyperfine magnetic fields. Furthermore, the magnetic properties of the prepared NPs were also investigated by zero-field cooled (ZFC) and field cooled (FC) magnetizations and AC susceptibility measurements. The MZFC (T) results showed a blocking temperature (TB). Below TB, the products behave as ferromagnetic (FM) and act superparamagnetic (SPM) above TB. The MFC (T) curves indicated the existence of super-spin glass (SSG) behavior below Ts (spin-glass freezing temperature). The AC susceptibility measurements confirmed the existence of the two transition temperatures (i.e., TB and Ts). Numerous models, e.g., Neel–Arrhenius (N–A), Vogel–Fulcher (V–F), and critical slowing down (CSD), were used to investigate the dynamics of the systems. It was found that the Dy substitution enhanced the magnetic interactions.

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35

Odagaki, T., J. Matsui, and Y. Hiwatari. "Glass Transition Singularities and Slow Relaxation." MRS Proceedings 367 (1994). http://dx.doi.org/10.1557/proc-367-337.

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AbstractGeneralized susceptibility for the binary soft-sphere mixtures is computed for the frequency range including both the a and β peaks in a supercooled fluid phase with a superlong-time molecular dynamics simulation. It is shown that the a peak has a non-Debye type frequency dependence and the β peak is essentially of a Debye-type. The slow dynamics is analyzed on the basis of the trapping diffusion model which takes account of two types of diffusive dynamics. With the use of the coherent medium approximation, the frequency dependence of dynamical quantities are shown to agree with the observation. The primary relaxation time is shown to exponentially diverge at a certain temperature below the glass transition point, in line with the Vogel-Fulcher equation. A unified view for the Vogel-Fulcher temperature, the glass transition temperature and the kinetic transition temperature is give on the basis of the trapping diffusion model.

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Deshmukh, Dhananjay P., Praful D. Shirbhate, Sangita S. Yawale, and Shrikrishna P. Yawale. "Application of Vogel-Tamman-Fulcher (VTF) model to polythiophene composite thin films." Journal of Polymer Engineering 32, no. 2 (March 1, 2012). http://dx.doi.org/10.1515/polyeng.2011-0128.

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Abstract Synthesis of polymer composites poly (vinyl acetate) (PVAc) and polythiophene (PTh) was done by chemical oxidative method using FeCl3oxidant in methanol. Thin films with PTh-PVAc polymer composite were prepared for 5.5, 10.4, 14.9, 18.9 and 22.5 wt% of iodine as a dopant. Direct current (DC) conductivity as a function of temperature (313–363 K) was measured by the two probe method. Characterization of the sample was done via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG)/differential thermal analysis (DTA). The maximum value for DC electrical conductivity was found for 10.4 wt% (σ=9.78×10-10S cm-1). The decrease in conductivity for greater iodine concentrations may be due to reduced segmental motion. The temperature dependence conductivity shows percolative behavior and a clear cross over from Vogel-Tamman-Fulcher (VTF) to Arrhenius behavior. Ionic conduction decreased with increase in the concentration of iodine, which shows ionic charge transport. XRD of the samples showed an amorphous nature. FTIR spectra showed absorption in the range 550–3600 cm-1, which indicates various bands involved in the PTh-PVAc polymer composite with iodine doping. From TG/DTA studies, it was observed that all the samples with a different wt% of iodine showed degradation in a range 75–81% when heated up to 888 K.

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Sahnoune, A., and L. Piché. "Relaxation Behavior in Polystyrene Near and Above the Glass Transiton Studied by Ultrasonic Technique." MRS Proceedings 407 (1995). http://dx.doi.org/10.1557/proc-407-173.

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ABSTRACTWe report measurements of the temperature and pressure dependence of ultrasonic modulus in polystyrene between 340 and 550 K and applied pressures up to 775 bar. The real and imaginary parts of the modulus are analyzed within the Havriliak-Negami model and very good agreement is found over the entire temperature and pressure ranges. Using the Vogel-Tammann-Fulcher equation for the relaxation time, the Kauzmann temperature TK and the fragility parameter D of polystyrene were determined. The value of D indicates that polystyrene is a fragile-glass former.

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38

Bossuyt, Sven, Marios D. Demetriou, William L. Johnson, and A. Lindsay. "Transient Deformation and Flow in Bulk Metallic Glasses and Deeply Undercooled Glass Forming Liquids — A Self-Consistent Dynamic Free Volume Model." MRS Proceedings 754 (2002). http://dx.doi.org/10.1557/proc-754-cc7.10.

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ABSTRACTRecently, a self-consistent dynamic free volume model was proposed to analyze the Newtonian and non-Newtonian uniform steady-state flow data for bulk glass forming liquids such as those of the Zr-Ti-Cu-Ni-Be Vitreloy family. The model is based on the traditional free volume model of the glass transition, the Vogel-Fulcher-Tammann (VFT) equation, and a simple treatment of free volume production and annihilation during flow. It was shown that the model results in a simple one-parameter fit to extend the VFT equation for Newtonian flow to non-Newtonian uniform steady-state flow. We further extend the model to include transient uniform flow, by considering the evolution of free volume with time.

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39

Sahnoune, A., and L. Piché. "Glass Transition and Ultrasonic Relaxation in Polystyrene." MRS Proceedings 455 (1996). http://dx.doi.org/10.1557/proc-455-183.

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ABSTRACTWe present measurements of the glass transition and the ultrasonic relaxation modulus in a series of monodisperse polystyrenes. The temperature dependence of the modulus was analyzed using Havriliak-Negami relaxation model (HN) and Vogel-Tammann-Fulcher equation (VTF) for the relaxation time. The results allowed us to determine the fragility index, m, which decreases with increasing molecular weight, Mn. Furthermore, the relaxation time was found to saturate at high molecular weights and varies as Mnp, in the low molecular weight region. The exponent is p≈2 at high temperatures and p ≈ 7 at low temperatures close to Tg.

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40

Funke, K. "Crystalline, Glassy and Molten Electrolytes: Conductivity Spectra and Model Consdderations." MRS Proceedings 455 (1996). http://dx.doi.org/10.1557/proc-455-319.

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ABSTRACTConductivity spectra of crystalline, glassy and molten electrolytes are presented and discussed. The spectra cover fourteen decades on the frequency scale as well as wide temperature ranges. In some crystalline ion conductors, the translational and vibrational contributions to the conductivity are well separated on the frequency scale. This is not observed in glasses and melts. In these cases, the vibrational components can, however, often be removed from the total spectra, yielding the translational component. We find that in crystalline, glassy, and molten electrolytes the conductivity caused by translational motion of the ions exhibits plateaux at both low and high frequencies, with a dispersive regime in between. The dispersive sections of the conductivity isotherms always cover a triangular area in a log-log plot of conductivity times temperature versus frequency. For an interpretation, the jump relaxation model turns out to be appropriate for crystalline electrolytes. The existence of different kinds of site is typical of glasses. For fragile molten electrolytes, a simple semimicroscopic model is presented which explains the experimental findings including the Vogel-Fulcher-Tammann temperature dependence of the dc conductivity.

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Matsui, J., M. Fujisaki, and T. Odagaki. "Separation of Diffusive Jump Motion and Trapped Motion of Atoms in a Glass Forming Process Via Molecular Dynamics Simulation." MRS Proceedings 455 (1996). http://dx.doi.org/10.1557/proc-455-285.

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ABSTRACTWe have carried out the molecular dynamics (MD) simulation for a binary soft-sphere system and calculated the self part of the generalized susceptibility χs(q, ω) at various temperatures. At higher temperatures in liquid state, only one peak appears in the imaginary part of Xa, which tends to split into two peaks, the so-called α- and β- peaks, as the temperature is reduced. The temperature dependence of the peak frequency is well described by the Vogel-Fulcher law for the α- peak, and the peak frequency does not change much for the α- peak. We have also measured the trajectory volume of a tagged atom V(t), which is related to the dynamical order parameter, the “generalized capacity”, in structural glass transitions recently proposed by J. F. Douglas. These results show the transition temperature which is in good agreement with that determined by the trapping diffusion model.

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42

Caprion, D., M. Kluge, and H. R. Schober. "Diffusion and Relaxation in Glasses and their Melts." MRS Proceedings 754 (2002). http://dx.doi.org/10.1557/proc-754-cc4.8.

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ABSTRACTResults of computer simulations of diffusion and relaxation in the liquid and the glassy state are presented for model systems and Cu33Zr67 and Se. The diffusion constant and the intermediate self scattering function show the typical behavior upon quenching from the liquid to the glass. The diffusion constant in the undercooled liquid can be fitted both with a Vogel-Fulcher or a mode coupling law. However, its pressure derivative, the activation volume, clearly follows the prediction of the mode coupling theory. From the diffusional isotope effect in the liquid we conclude that collectivity increases upon quenching to the glass transition. Checking the relaxations in the glass we find collective hopping of chains of atoms as elementary process. Both in the glassy state and in the undercooled liquid we observe an increase oc ∝√ι ofthe non-Gaussianity of the self correlation function, which measures the dynamic heterogeneity. This can be understood from the collective jump mechanism.

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Pakula, T., and J. Teichmann. "A Model for Relaxation in Supercooled Liquids and Polymer Melts." MRS Proceedings 455 (1996). http://dx.doi.org/10.1557/proc-455-211.

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ABSTRACTA new model for molecular rearrangements in liquids is proposed. The liquids are regarded as dense ensembles of vibrating molecules satisfying the excluded volume condition. A continuity condition is applied on the molecular scale of such systems and is regarded as controlling rearrangements leading to translations of molecules beyond the range of their vibration amplitude. It results in cooperative rearrangements which are considered as taking place in systems with fluctuating density. Rates of rearrangements are considered as being controlled by thermal activation with activation energy barriers dependent on local density. Various dependencies of the activation energy barriers on local density are examined. It is shown, that the model is able to reproduce the extremal cases of temperature dependencies of relaxation times represented on one edge by the Arrhenius relation and on the other edge by the Vogel-Fulcher-Tamman relation. The model can, however, provide a broad spectrum of other dependencies filling the gap between these extremes. All cases are based on the uniform microscopic picture of cooperative molecular rearrangements resulting from system continuity. The model is implemented as a simulation algorithm (Dynamic Lattice Liquid - DLL algorithm) which is used to simulate dynamic properties of liquids and polymer melts. Simulation results obtained for polymers are compared with experimental results obtained by means of the dynamic mechanical measurements on polyisobutylene samples with various molecular weights.

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Hu, Kai, Kai Tang, Xuewei Lv, Jafar Safarian, Zhiming Yan, and Bing Song. "Modeling Viscosity of High Titania Slag." Metallurgical and Materials Transactions B, November 4, 2020. http://dx.doi.org/10.1007/s11663-020-02002-8.

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Abstract TiO2-FeO-Ti2O3 slag system is the dominant system for industrial high-titania slag production. In the present work, viscosities of TiO2-FeO and TiO2-FeO-Ti2O3 systems were experimentally determined using the concentric rotating cylinder method under argon atmosphere. A viscosity model suitable for the TiO2-FeO-Ti2O3 slag system was then established based on the modification of the Vogel-Fulcher-Tammann (VFT) equation. The experimental results indicate that completely melted high-titania slags exhibit very low viscosity of around 0.8 dPa s with negligible dependence on temperature and compositions. However, it increases dramatically with decreasing temperature slightly below the critical temperature. Besides, the increase in FeO content was found to remarkably lower the critical temperature, while the addition of Ti2O3 increases it. The developed model can predict the viscosities of the TiO2-FeO-Ti2O3 and TiO2-FeO systems over wide ranges of compositions and temperatures within experimental uncertainties. The average relative error for the present model calculation is < 18.82 pct, which is better than the previously developed models for silicate slags reported in the literature. An iso-viscosity distribution diagram was made for the TiO2-FeO-Ti2O3 slag system, which can serve as a roadmap for the Ilmenite smelting reduction process as well as the high titania slags tapping process.

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Wei, Ying, Bing Wang, Zhen Zhao, Xin-yuan Zhang, Xuan-yu Wu, and Qing-Guo Zhang. "Estimation of Physico-Chemical Properties and Structure Characteristics of New Alkylimidazolium Salicylate Ionic Liquids." Zeitschrift für Physikalische Chemie 230, no. 8 (January 28, 2016). http://dx.doi.org/10.1515/zpch-2015-0576.

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AbstractTwo new ionic liquids derived from natural product salicylate, 1-methyl-3-ethylimidazolium salicylate ([Emim][Sal]) and 1,2-dimethyl-3-ethylimidazolium salicylate ([Emmim][Sal]), were synthesized and characterized. The density, surface tension, viscosity, and electrical conductivity of two ionic liquids were determined from 288.15 to 343.15 K. The physico−chemical properties of the ionic liquids were estimated from the experimental data by empiric or semi-empiric methods, such as, coefficients of thermal expansion, molecular volume, standard molar entropy, lattice energy, enthalpy of vaporization, and so on. According to the interstice model of ionic liquids, the interstice parameters like coefficients of thermal expansion and interstice volume etc. were estimated, too. The experimental results and Density Functional Theory (DFT) calculation were employed to discuss the structure characteristics caused by differences of cations/anions for properties of two ionic liquids. And by the Vogel–Fulcher–Tamman (VFT) equation, the temperature dependences of the ILs viscosities and electric conductivities were graphically described. The structures, the energetics and COSMO volumes of all investigated ions are obtained by combining DFT calculations and the COSMO–RS methodology to describe intermolecular interactions of ionic liquids.

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Gygli, Gudrun, Xinmeng Xu, and Jürgen Pleiss. "Meta-analysis of viscosity of aqueous deep eutectic solvents and their components." Scientific Reports 10, no. 1 (December 2020). http://dx.doi.org/10.1038/s41598-020-78101-y.

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AbstractDeep eutectic solvents (DES) formed by quaternary ammonium salts and hydrogen bond donors are a promising green alternative to organic solvents. Their high viscosity at ambient temperatures can limit biocatalytic applications and therefore requires fine-tuning by adjusting water content and temperature. Here, we performed a meta-analysis of the impact of water content and temperature on the viscosities of four deep eutectic solvents (glyceline, reline, N,N-diethylethanol ammonium chloride-glycerol, N,N-diethylethanol ammonium chloride-ethylene glycol), their components (choline chloride, urea, glycerol, ethylene glycol), methanol, and pure water. We analyzed the viscosity data by an automated workflow, using Arrhenius and Vogel–Fulcher–Tammann–Hesse models. The consistency and completeness of experimental data and metadata was used as an essential criterion of data quality. We found that viscosities were reported for different temperature ranges, half the time without specifying a method of desiccation, and in almost half of the reports without specifying experimental errors. We found that the viscosity of the pure components varied widely, but that all aqueous mixtures (except for reline) have similar excess activation energy of viscous flow $${E}^{excess}_{\eta}$$ E η excess = 3–5 kJ/mol, whereas reline had a negative excess activation energy ($${E}^{excess}_{\eta}$$ E η excess = − 19 kJ/mol). The data and workflows used are accessible at 10.15490/FAIRDOMHUB.1.STUDY.767.1.

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Journal articles on the topic 'Vogel-Fulcher model'

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