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.

Structural Relaxation Process in CuHfTi Amorphous Alloys

2009 ◽  
Vol 283-286 ◽  
pp. 533-538 ◽  
Author(s):  
Kazumasa Yamada ◽  
N. Shinagawa ◽  
M. Sogame ◽  
I.A. Figueroa ◽  
Hywel A. Davies ◽  
...  
Keyword(s):  
Activation Energy ◽  
Relaxation Process ◽  
Structural Relaxation ◽  
Amorphous Alloys ◽  
Melt Spinning ◽  
Amorphous Materials ◽  
Ternary Alloys ◽  
Relaxation Processes ◽  
Scanning Calorimetry ◽  
Structure Relaxation

The aim of this research is to clarify a quantitative evaluation in the structural relaxation processes focusing on the activation energy in Cu based amorphous alloys. The activation energy for structural relaxation process in a metal type amorphous CuHfTi ternary alloys, with cross sections of typically 0.03 mm x 2.0 mm, prepared by chill-block melt spinning has been investigated by Differential Scanning Calorimetry (DSC) with a cyclically heating technique. Activation energies for structural relaxation with a spatial quantity in amorphous materials have been discussed by use of a relaxed ratio function that depends on annealing temperature and time. In the present work, the distributions for the Activation Energy Spectrum (AES) were observed almost 152 kJmol-1 (1.58 eV). Another result has been also established that the “reversible” AES model energy distribution though the cyclically structure relaxation occurs even in amorphous Cu60Hf20Ti20 alloy.

Structural Relaxation Process by Addition of B in CuHfTi Amorphous Alloys

2010 ◽  
Vol 297-301 ◽  
pp. 702-707
Author(s):  
Kazumasa Yamada ◽  
N. Miura ◽  
A. Yamamoto ◽  
I.A. Figueroa ◽  
Hywel A. Davies ◽  
...  
Keyword(s):  
Activation Energy ◽  
Relaxation Process ◽  
Structural Relaxation ◽  
Amorphous Alloys ◽  
Melt Spinning ◽  
Amorphous Materials ◽  
Relaxation Processes ◽  
Quaternary Alloys ◽  
Scanning Calorimetry ◽  
Structure Relaxation

The aim of this research is to clarify a quantitative evaluation in the structural relaxation processes focusing on the activation energy on the addition of B to Cu-based amorphous alloys. The activation energy for structural relaxation process in a metal type amorphous CuHfTi ternary and CuHfTiB quaternary alloys, with cross sections of typically 0.03 mm x 2.0 mm, prepared by chill-block melt spinning has been investigated by Differential Scanning Calorimetry (DSC) with a cyclically heating technique. Activation energies for structural relaxation with a spatial quantity in amorphous materials have been discussed by use of a total relaxed ratio function that depends on annealing temperature and time. In the present work on CuHfTi ternary and CuHfTiB quaternary alloys, the distributions for the Activation Energy Spectrum (AES) by calculation with derivative-type relaxed ratio function were observed almost 160 kJmol-1, whereas in difference for shape only in the CuHfTi-B3% quaternary alloy. Another result has been also established that the ‘reversible’ AES model energy distribution though the cyclically structure relaxation occurs even in amorphous CuHfTiB alloy system.

The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite

2007 ◽  
Vol 555 ◽  
pp. 497-502
Author(s):  
Dejan Miličević ◽  
S. Trifunović ◽  
N. Ignjatović ◽  
E. Suljovrujić
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Structural Relaxation ◽  
Absorbed Dose ◽  
Gel Permeation Chromatography ◽  
Chain Scission ◽  
Scanning Calorimetry ◽  
Dsc Measurements

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma irradiation has been successfully employed in the modification/sterilization of such porous composites and that it has advantages over other procedures. In this study, differential scanning calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass transition behavior and structural relaxation, as well as to estimate the activation energy for this process. The apparent activation energy ΔH* for structural relaxation in the glass transition region was determined on the basis of the heating rate dependence of the glass transition temperature Tg. Furthermore, the results were correlated with those obtained by gel permeation chromatography (GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is the main reason for the decrease of the glass transition temperature and/or activation energy with the absorbed dose.

Enthalpy Relaxation Kinetics of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 Supercooled Liquid Close to the Glass Transition

2003 ◽  
Vol 806 ◽  
Author(s):  
Minalben B. Shah ◽  
Ralf Busch
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Enthalpy Relaxation ◽  
Medium Size ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Relaxation Kinetics ◽  
State Diffusion

ABSTRACTIsothermal relaxation studies of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glass forming alloy were performed using Differential Scanning Calorimetry in the glass transition and the supercooled liquid region. A new experimental method was developed to study the isothermal enthalpy relaxation kinetics. The results reveal that the enthalpy relaxes in an Arrhenius fashion. The activation energy obtained from the Arrhenius fit is comparable to the activation energy required for the diffusion of the medium size atoms. This suggests that the solid-state diffusion governs the enthalpy relaxation process. The stretching exponents for the relaxation are close to unity, which indicates that the alloy is a rather strong glass former.

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.

Thermal Stability and Crystallization Kinetics of Ti40Zr10Cu34Pd14Sn2 Bulk Metallic Glass

2012 ◽  
Vol 188 ◽  
pp. 3-10 ◽  
Author(s):  
Mariana Calin ◽  
Mihai Stoica ◽  
Na Zheng ◽  
Xiao Rui Wang ◽  
Sergio Scudino ◽  
...  
Keyword(s):  
Activation Energy ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Crystallization Process ◽  
Primary Crystallization ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Diffusion Controlled

In this work, the isochronal and isothermal activation energies for the primary crystallization process of Ti40Zr10Cu34Pd14Sn2bulk metallic glass have been studied by differential scanning calorimetry and determined using the Kissinger approach and the Johnson-Mehl-Avrami analysis, respectively. The activation energy for crystallization evaluated by the Kissinger method is 253 kJ/mol. Similar activation energy for crystallization was obtained from the viscosity measurements. The values of the differential Avrami exponent are also determined from the isothermal data. Assuming diffusion-controlled growth, it is shown that thermal treatment of the samples in the supercooled liquid region considerably influences the behavior of the nucleation rate during the crystallization process.

Analytical solution for the Kissinger equation

2009 ◽  
Vol 24 (10) ◽  
pp. 3095-3098 ◽  
Author(s):  
Pere Roura ◽  
Jordi Farjas
Keyword(s):  
Activation Energy ◽  
Analytical Solution ◽  
Kinetic Analysis ◽  
Relative Error ◽  
Structural Relaxation ◽  
Amorphous Materials ◽  
Reaction Rate ◽  
Large Range ◽  
Peak Temperature ◽  
Kissinger Equation

An analytical solution for the Kissinger equation relating the activation energy, E, with the peak temperature of the reaction rate, Tm, has been found. It is accurate (relative error below 2%) for a large range of E/RTm values (from 15 to above 60) that cover most experimental situations. The possibilities opened by this solution are outlined by applying it to the analysis of some particular problems encountered in structural relaxation of amorphous materials and in kinetic analysis.

Formation and Properties of Amorphous and Nanocrystalline Phases in Mechanically Alloyed Fe-Based Multicomponent Alloys

1996 ◽  
Vol 455 ◽  
Author(s):  
N. Schlorke ◽  
J. Eckert ◽  
L. Schultz
Keyword(s):  
Supercooled Liquid ◽  
Thermomechanical Analysis ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Structural Development ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Constant Rate ◽  
Nanocrystalline Phases

ABSTRACTMulticomponent Fe-Al-P-C-B alloys have been prepared by mechanical alloying of elemental powder mixtures. X-ray diffraction data were recorded to monitor the structural development of the powders. Coexistent amorphous and nanoscale crystalline phases are found for a variety of alloys. Some alloys exhibit an extended supercooled liquid region before crystallization. The compositional dependence of glass formation and the thermal stability of the resulting phases were investigated by constant-rate heating differential scanning calorimetry (DSC), isothermal annealing experiments, and thermomechanical analysis (TMA). The results are compared with data for melt-spun ribbons.

scholarly journals The Effect of Surface Treatment with Isocyanate and Aromatic Carbodiimide of Thermally Expanded Vermiculite Used as a Functional Filler for Polylactide-Based Composites

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 890
Author(s):  
Mateusz Barczewski ◽  
Olga Mysiukiewicz ◽  
Aleksander Hejna ◽  
Radosław Biskup ◽  
Joanna Szulc ◽  
...  
Keyword(s):  
Impact Strength ◽  
Mechanical Stability ◽  
Thermomechanical Analysis ◽  
Thermomechanical Properties ◽  
Phenyl Isocyanate ◽  
Sem Analysis ◽  
Scanning Calorimetry ◽  
Melt Mixing ◽  
Expanded Vermiculite ◽  
Chain Extenders

In this work, thermally expanded vermiculite (TE-VMT) was surface modified and used as a filler for composites with a polylactide (PLA) matrix. Modification of vermiculite was realized by simultaneous ball milling with the presence of two PLA chain extenders, aromatic carbodiimide (KI), and 4,4’-methylenebis(phenyl isocyanate) (MDI). In addition to analyzing the particle size of the filler subjected to processing, the efficiency of mechanochemical modification was evaluated by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The composites of PLA with three vermiculite types were prepared by melt mixing and subjected to mechanical, thermomechanical, thermal, and structural evaluation. The structure of composites containing a constant amount of the filler (20 wt%) was assessed using FTIR spectroscopy and SEM analysis supplemented by evaluating the final injection-molded samples’ physicochemical properties. Mechanical behavior of the composites was assessed by static tensile test and impact strength hardness measurements. Heat deflection temperature (HDT) test and dynamic thermomechanical analysis (DMTA) were applied to evaluate the influence of the filler addition and its functionalization on thermomechanical properties of PLA-based composites. Thermal properties were assessed by differential scanning calorimetry (DSC), pyrolysis combustion flow calorimetry (PCFC), and thermogravimetric analysis (TGA). The use of filler-reactive chain extenders (CE) made it possible to change the vermiculite structure and obtain an improvement in interfacial adhesion and more favorable filler dispersions in the matrix. This translated into an improvement in impact strength and an increase in thermo-mechanical stability and heat release capacity of composites containing modified vermiculites.

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