Shear modulus and internal friction hystereses during structural relaxation of metallic glasses based on Pd and Zr in the vicinity of the glass transition range

2015 ◽  
Vol 57 (8) ◽  
pp. 1574-1578 ◽  
Author(s):  
V. A. Khonik ◽  
Yu. P. Mitrofanov ◽  
A. S. Makarov ◽  
G. V. Afonin ◽  
A. N. Tsyplakov
Keyword(s):  
Glass Transition ◽  
Internal Friction ◽  
Shear Modulus ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Transition Range ◽  
Glass Transition Range

scholarly journals Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1778
Author(s):  
Jürgen E. K. Schawe ◽  
Claus Wrana
Keyword(s):  
Glass Transition ◽  
Structural Relaxation ◽  
Random Sequence ◽  
High Sensitivity ◽  
Random Copolymers ◽  
High Time Resolution ◽  
Scanning Calorimetry ◽  
Transition Range ◽  
Glass Transition Range ◽  
And Control

Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the high sensitivity, the fast cooling rates, and the high time resolution. Crystallization in HNBR causes a segregation of non-crystallizable segments in the macromolecule. This yields a reduction in mobility in the vicinity of the formed crystals and as a consequence an increased amount of so-called “rigid amorphous fraction” (RAF). The RAF can be interpreted as self-assembled confinements, which limit and control the crystallization. An analysis of the crystallization and the relaxation shows that the kinetic of both is identical. This means that the Kohlrausch exponent of relaxation and the Avrami exponent of crystallization are identical. Therefore, the crystallization is not controlled by nucleation but by diffusion and is terminated by the formation of RAF.

scholarly journals Metallic Glasses: A New Approach to the Understanding of the Defect Structure and Physical Properties

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 605 ◽  
Author(s):  
Vitaly Khonik ◽  
Nikolai Kobelev
Keyword(s):  
Shear Modulus ◽  
Physical Properties ◽  
Experimental Verification ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Defect Structure ◽  
Relaxation Phenomena ◽  
Volume Changes ◽  
New Approach ◽  
Heat Effects

The work is devoted to a brief overview of the Interstitialcy Theory (IT) as applied to different relaxation phenomena occurring in metallic glasses upon structural relaxation and crystallization. The basic hypotheses of the IT and their experimental verification are shortly considered. The main focus is given on the interpretation of recent experiments on the heat effects, volume changes and their link with the shear modulus relaxation. The issues related to the development of the IT and its relationship with other models on defects in metallic glasses are discussed.

.alpha.-Relaxation in the Glass Transition Range of Amorphous Polymers. 1. Temperature Behavior across the Glass transition

1995 ◽  
Vol 28 (5) ◽  
pp. 1516-1527 ◽  
Author(s):  
A. Alegria ◽  
E. Guerrica-Echevarria ◽  
L. Goitiandia ◽  
I. Telleria ◽  
J. Colmenero
Keyword(s):  
Glass Transition ◽  
Amorphous Polymers ◽  
Temperature Behavior ◽  
Transition Range ◽  
Glass Transition Range
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