scholarly journals Formation of Nanocrystalline and Amorphous Materials Causes Parallel Brittle‐viscous Flow of Crustal Rocks:Experiments on Quartz – Feldspar Aggregates

2021 ◽  
Author(s):  
Matej Pec ◽  
Saleh Al Nasser
Keyword(s):  
Viscous Flow ◽  
Amorphous Materials ◽  
Nanocrystalline And Amorphous

scholarly journals Kinematic features of viscous flow of amorphous materials during an equal channel multiple-angle extrusion through a 2-turn rectangular die

2011 ◽  
Vol 1 (4) ◽  
pp. 217-221 ◽  
Author(s):  
A. V. Perig ◽  
N. N. Golodenko ◽  
I. G. Zhbankov ◽  
I. I. Boiko ◽  
A. A. Sitnik
Keyword(s):  
Viscous Flow ◽  
Amorphous Materials

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.

On Fluidization of Borosilicate Glasses in Intense Radiation Fields

2009 ◽  
Author(s):  
Michael Ojovan ◽  
Guenter Mo¨bus ◽  
Jim Tsai ◽  
Stuart Cook ◽  
Guang Yang
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Viscous Flow ◽  
Electron Irradiation ◽  
Amorphous Materials ◽  
Flow Behaviour ◽  
High Electron ◽  
Borosilicate Glasses ◽  
Glassy Materials

The viscosity is rate-limiting for many processes in glassy materials such as homogenisation and crystallisation. Changes in the viscous flow behaviour in conditions of long-term irradiation are of particular interest for glassy materials used in nuclear installations as well as for nuclear waste immobilising glasses. We analyse the viscous flow behaviour of oxide amorphous materials in conditions of electron-irradiation using the congruent bond lattice model of oxide materials accounting for the flow-mediating role of broken bonds termed configurons. An explicit equation of viscosity was obtained which is in agreement with experimental data for non-irradiated glasses and shows for irradiated glasses, first, a significant decrease of viscosity, and, second, a stepwise reduction of the activation energy of flow. An equation for glass-transition temperature was derived which shows that irradiated glasses have lower glass transition temperatures. Intensive electron irradiation of glasses causes their fluidisation due to non-thermal bond breaking and can occur below the glass transition temperature. Due to surface tension forces fluidisation of glasses at enough high electron flux densities can result in modification of nano-size volumes and particles such as those experimentally observed under TEM electron beams.

About activation energy of viscous flow of glasses and melts

2015 ◽  
Vol 1757 ◽  
Author(s):  
Michael I. Ojovan
Keyword(s):  
Activation Energy ◽  
Viscous Flow ◽  
Amorphous Materials ◽  
Temperature Relationship ◽  
Defect Model ◽  
Transition Range ◽  
High Q ◽  
Liquid Transition ◽  
Variable Activation Energy ◽  
Continuous Temperature

ABSTRACTData on a viscous flow model based on network defects – broken bonds termed configurons – were analysed. An universal equation has been derived for the variable activation energy of viscous flow Q(T) of the generic Frenkel equation of viscosity η(T)=A∙exp(Q/RT) which is known to have two constant asymptotes – high QH at low temperatures and low QL at high temperatures. The defect model of flow used by e.g. Doremus, Mott, Nemilov, Sanditov states that higher the concentration of defects (e.g. configurons) the lower the viscosity. We have used the configuron percolation theory (CPT) which treats glass–liquid transition as a percolation-type phase transition. Additionally the CPT results in a continuous temperature relationship for viscosity valid for both glassy and liquid amorphous materials. We show that a particular result of CPT is the universal temperature relationship for the activation energy of viscous flow: Q(T)=QL+RT∙ln[1+exp(-Sd/R) exp((QH-QL)/RT)] which depends on asymptotic energies QL (for the liquid phase) and QH (for the glassy phase), and on entropy of configurons Sd. This equation has two asymptotes, namely Q(T<<Tg) = QH, and Q(T>>Tg) = QL. Moreover we demonstrate that the equation for Q(T) practically coincides in the transition range of temperatures with known Sanditov equation.

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