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.

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.

Changes of Structure and Magnetic Properties of Fe66Co24Si3B7 Amorphous Alloy under Heat Treatment

2013 ◽  
Vol 718-720 ◽  
pp. 42-46 ◽  
Author(s):  
Aleksandr Kotvitckii ◽  
Galina Kraynova ◽  
Anatoly Frolov
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moment ◽  
Structural Relaxation ◽  
Amorphous Alloys ◽  
Amorphous Material ◽  
Relaxation Processes ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Structure Sensitive ◽  
Melt Spun

In this paper features of structure at the atomic level, magnetic properties, and mechanisms of structural relaxation during thermal annealing of melt-spun ribbon Fe66Co24Si3B7(ribbon thickness is 28 microns) will be discussed. By means of differential scanning calorimetry and X-ray diffraction analysis of melt-spun alloy it has been shown that structural relaxation processes have complex multi-step nature, primarily related with instability of alloy. Using this data it has been shown that magnetic structure-sensitive properties, such as coercivity and magnetic moment, can be considered as structural relaxation indicators in amorphous alloys. The original amorphous material when heated to crystallization temperature partially passes to the crystalline state, causing the increase in residual magnetic moment and coercivity.

Crystallization of Amorphous Silicon-Aluminum thin Films: IN-SITU Observation and Thermal Analysis.

1991 ◽  
Vol 237 ◽  
Author(s):  
Toyohiko J. Konno ◽  
Robert Sinclair
Keyword(s):  
Activation Energy ◽  
Amorphous Alloys ◽  
Amorphous Matrix ◽  
In Situ Observation ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Higher Temperature ◽  
Sputter Deposited

ABSTRACTThe crystallization of sputter-deposited Si/Al amorphous alloys was examined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). In-situ high-resolution TEM reveals the existence of an Al layer between the amorphous matrix and the growing crystalline phase. The activation energy for the growth is about 1.2eV, roughly corresponding to the activation energy of Si diffusion in Al. These two observations support the view that a crystallization mechanism, in which an Al buffer layer provides the shortest reaction path, is responsible for the reaction. The product microstructure exhibits secondary crystallization at a higher temperature.

Structural Relaxation of Open Volume in Hyper-Eutectic Zr-Cu-Al Bulk Amorphous Alloys Measured by Positron Annihilation

2017 ◽  
Vol 373 ◽  
pp. 130-133
Author(s):  
Taishi Ishiyama ◽  
Kazukui Kobayashi ◽  
Yoshihiko Yokoyama ◽  
Toyohiko J. Konno ◽  
Akihiro Iwase ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Structural Relaxation ◽  
Amorphous Alloys ◽  
Density Measurement ◽  
High Strength ◽  
Eutectic Alloys ◽  
Ordered Structure ◽  
Compositional Dependence ◽  
Scanning Calorimetry ◽  
Bulk Amorphous Alloys

The Zr-Cu-Al bulk amorphous (BA) alloys, which have no long-range ordered structure, possess various properties such as high strength and toughness with compositional dependence. In the present study, in order to estimate the natures of local structure change and relaxation behavior of hyper-eutectic BA alloys during annealing, positron annihilation measurements and density measurement have been performed for hyper-eutectic Zr-Cu-Al BA alloys with annealing. The enthalpy relaxation and structural relaxation was also measured by differential scanning calorimetry (DSC) measurement. These results show that the relaxation process of free volume containing in hyper-eutectic BA alloys is different from that in hypo-eutectic alloys.

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.

Stress Relaxation Mechanisms in Rubbers Reinforced with Carbon Blacks

1972 ◽  
Vol 45 (1) ◽  
pp. 82-93 ◽  
Author(s):  
G. M. Bartenev ◽  
N. M. Lyalina
Keyword(s):  
Activation Energy ◽  
Stress Relaxation ◽  
Relaxation Process ◽  
Activation Energies ◽  
Relaxation Processes ◽  
Carbon Blacks ◽  
Multi Stage ◽  
Chemical Relaxation ◽  
Filled Rubbers ◽  
Weight Structures

Abstract 1. In vulcanized rubbers containing blacks a multi-stage mechanism for stress relaxation was observed. It was discovered that the stress relaxation process consists of five fundamental processes: the first three relaxation processes, related to the slow stages of physical relaxation within the bulk of the rubber, have no connection with the fillers (“soft” domains); the fourth process has to do with the relaxation in the black-rubber domain; the fifth process involves the chemical relaxation of vulcanizates. 2. The fundamental mechanisms of the first 3 relaxation processes in the soft domains have the same activation energy values and the same segmental mechanism as the rearranged domains found in supermolecular weight structures, which are also present in unfilled vulcanizates. 3. In the investigated stress range of up to 200% elongation, the activation energy for the first 3 relaxation processes in the soft domains of filled vulcanizates is not a function of the deformation strain, whereas the activation energy of the fourth relaxation process in the black-rubber domains of filled rubbers is a function of the deformation and of the filler content. For these reasons, rubber loaded with carbon blacks, in contrast to unfilled rubbers, possess the typical nonlinearity of viscoelastic materials. 4. The activation energies of the relaxation processes in the black-rubber domains decrease in a linear fashion with the value for the initial tensile stress in filled vulcanizates, and decrease in like manner for vulcanizates containing different proportions of fillers. The kinetic units, determined from the activation energies of these processes, appeared to be segments of chains with activation energies of up to 40% more than the activation energies of the physical relaxation processes in the soft domains. The other kinetic units of the processes proved to be black particles, the dimensions of which were calculated from the values for the coefficients in the formula for relaxation time.

ULTRASONIC ABSORPTION IN BUTYRIC ACID

1958 ◽  
Vol 36 (8) ◽  
pp. 1135-1137 ◽  
Author(s):  
P. White ◽  
G. C. Benson
Keyword(s):  
Activation Energy ◽  
Relaxation Process ◽  
Butyric Acid ◽  
Relaxation Frequency ◽  
Relaxation Processes ◽  
Ultrasonic Absorption ◽  
Kcal Mole ◽  
Pulse Technique

Ultrasonic absorption has been measured in pure butyric acid by a pulse technique from 0 ° to 40 °C. and values of the relaxation frequency obtained. The activation energy of the relaxation process is shown to be 1.1 kcal./mole. These results are compared with published values for acetic and propionic acids and possible relaxation processes are discussed.

scholarly journals Effect of cobalt content on non-isothermal crystallization kinetics of Fe-based amorphous alloys

2019 ◽  
pp. 44-52
Author(s):  
Carolina Parra-Velásquez ◽  
Darling Perea-Cabarcas ◽  
Francisco Javier Bolivar-Osorio
Keyword(s):  
Activation Energy ◽  
Crystallization Kinetics ◽  
Melt Spinning ◽  
Cobalt Content ◽  
Amorphous Structure ◽  
Scanning Calorimetry ◽  
Jma Model ◽  
Nucleation Mechanisms ◽  
Local Activation Energy ◽  
Kinetics Of

In the present study, FeSiBP and FeCoSiBP ribbons with a fully amorphous structure were made by melt spinning technique. A detailed analysis of the isochronal crystallization behavior is presented in this paper. The influence of cobalt on the crystallization kinetics of the alloys was studied under isochronal conditions using differential scanning calorimetry (DSC). Apparent and local activation energy values were determined by Kissinger, Ozawa and Kissinger-Akahira-Sunose (KAS) methods. The results indicate that appropriate amounts of cobalt can significantly enhance the thermal stability of Fe-based alloys, through an increase in nucleation activation energy from 538kJ/mol to 701kJ/mol, obtained by Kissinger method. Furthermore, with the method proposed by Matusita, it was possible to obtain global values for the Avrami exponent, noting that from a general perspective, Co changes the mechanism from diffusion controlled to interface controlled. This leads to the conclusion that the crystallization process is complex and takes place in more than one stage. Therefore, the determination of nucleation mechanisms and dimensional growth is difficult due to the inapplicability of the Johnson-Melh-Avrami (JMA) model. As such, a study under isothermal conditions is suggested, in order to achieve a full understanding of the mechanisms involved.

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