An activation energy approach for viscous flow: A complementary tool for the study of microstructural evolutions in sheared suspensions

2017 ◽  
Vol 308 ◽  
pp. 318-323 ◽  
Author(s):  
F.J. Rubio-Hernández ◽  
A.I. Gómez-Merino ◽  
R. Delgado-García ◽  
N.M. Páez-Flor
Keyword(s):  
Activation Energy ◽  
Viscous Flow ◽  
Energy Approach ◽  
Sheared Suspensions

ENTROPY INFLUENCE ON THE DEPENDENCE OF THE NANOFLUIDS VISCOSITY ON TEMPERATURE AND SHEAR RATE

2021 ◽  
Vol 7 (3) ◽  
pp. 89-105
Author(s):  
Lyudmila P. SEMIKHINA ◽  
Daniil D. Korovin
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Shear Rate ◽  
Viscous Flow ◽  
High Reliability ◽  
Narrow Particle Size Distribution ◽  
Disperse Systems ◽  
Rotational Viscometer ◽  
Surfactant Micelles ◽  
Dispersed Systems

A Brookfield DV-II + Pro rotational viscometer was used to study the viscosity of 7 samples of concentrated nanodispersed systems (nanofluids) with a similar viscosity (6-22 mPa ∙ s), the particles of the dispersed phase in which are nanosized surfactant micelles and conglomerates from them. It was found that for 5 out of 7 studied reagents, there is a decrease in viscosity typical for dispersed systems with an increase in the shear rate, and their flow curves, that is, the dependence of the shear stress on the shear rate, correspond to the ideal plastic flow of non-Newtonian fluids. Moreover, with high reliability, R2 ≥ 0.999 is described by the Bingham equation with a small value of the limiting shear stress (less than 0.2 Pa). It is shown that all the studied reagents are also characterized by an increase in the activation energy of a viscous flow Е with an increase in the shear rate. As a result, a decrease in viscosity with an increase in shear rate, typical for disperse systems, including nanofluids, is provided by a more significant increase in entropy changes ΔS compared to Е. It has been substantiated that, depending on the ratio between the activation energy of viscous flow Е and the change in entropy ΔS, the viscosity of concentrated micellar dispersed systems with an increase in the shear rate can decrease, remain unchanged, and increase. The last two cases, not typical for disperse systems and nanofluids, were identified and studied using the example of two demulsifiers, RIK-1 and RIK-2, with a maximum of a very narrow particle size distribution at 160 ± 5 nm, corresponding to the size of a special type of very stable micelles Surfactant — vesicle.

Viscosity Of Molten Rare Earth Metal Trichlorides I. Cecl3, Ndcl3, Smcl3, Dycl3 And Ercl3

2003 ◽  
Vol 58 (7-8) ◽  
pp. 457-463 ◽  
Author(s):  
A. Potapov ◽  
V. Khokhlov ◽  
Y. Satoa
Keyword(s):  
Activation Energy ◽  
Rare Earth ◽  
Viscous Flow ◽  
Rare Earth Metal ◽  
Dynamic Viscosity ◽  
Kinematic Viscosity ◽  
Arrhenius Equation ◽  
Earth Metal ◽  
Capillary Viscometer ◽  
Density Data

The kinematic viscosity of molten CeCl3, NdCl3, SmCl3, DyCl3 and ErCl3 has been measured by using a capillary viscometer. The dynamic viscosity was computed by using density data taken from the literature. The viscosity increases with going from CeCl3 to ErCl3. The activation energy of the viscous flow, calculated by the Arrhenius equation, rises in the same order.

scholarly journals Kinetic Processes in Amorphous Materials Revealed by Thermal Analysis: Application to Glassy Selenium

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2725 ◽  
Author(s):  
Málek ◽  
Svoboda
Keyword(s):  
Activation Energy ◽  
Crystal Growth ◽  
Viscous Flow ◽  
Structural Relaxation ◽  
Amorphous Materials ◽  
Supercooled Liquid ◽  
Thermomechanical Analysis ◽  
Growth Data ◽  
Scanning Calorimetry ◽  
Kinetic Processes

It is expected that viscous flow is affecting the kinetic processes in a supercooled liquid, such as the structural relaxation and the crystallization kinetics. These processes significantly influence the behavior of glass being prepared by quenching. In this paper, the activation energy of viscous flow is discussed with respect to the activation energy of crystal growth and the structural relaxation of glassy selenium. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and hot-stage infrared microscopy were used. It is shown that the activation energy of structural relaxation corresponds to that of the viscous flow at the lowest value of the glass transition temperature obtained within the commonly achievable time scale. The temperature-dependent activation energy of crystal growth, data obtained by isothermal and non-isothermal DSC and TMA experiments, as well as direct microscopic measurements, follows nearly the same dependence as the activation energy of viscous flow, taking into account viscosity and crystal growth rate decoupling due to the departure from Stokes–Einstein behavior.

scholarly journals The Glass Transition Temperature and Temperature Dependence of Activation Energy of Viscous Flow of Ovalbumin

2016 ◽  
Vol 39 (1) ◽  
pp. 13-25
Author(s):  
Karol Monkos
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Viscous Flow ◽  
Solvent Interactions ◽  
Model Free ◽  
Free Volume Model ◽  
Wide Range ◽  
Different Temperatures

Abstract The paper presents the results of viscosity determinations on aqueous solutions of ovalbumin at a wide range of concentrations and at temperatures ranging from 5°C to 55°C. On the basis of these measurements and three models of viscosity for glass-forming liquids: Avramov’s model, free-volume model and power-law model, the activation energy of viscous flow for solutions and ovalbumin molecules, at different temperatures, was calculated. The obtained results show that activation energy monotonically decreases with increasing temperature both for solutions and ovalbumin molecules. The influence of the energy of translational heat motion, protein-protein and protein-solvent interactions, flexibility and hydrodynamic radius of ovalbumin on the rate of decrease in activation energy with temperature has been discussed. One of the parameters in the Avramov’s equation is the glass transition temperature Tg. It turns out that the Tg of ovalbumin solutions increases with increasing concentration. To obtain the glass transition temperature of the dry ovalbumin, a modified Gordon-Taylor equation is used. Thus determined the glass transition temperature for dry ovalbumin is equal to (231.8 ± 6.1) K.

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