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Balitska V.,Lviv State University of Vital Activity Safety | Golovchak R.,Lehigh University | Shpotyuk O.,Lviv Institute of Materials
Solid State Phenomena | Year: 2013

Phenomenological description of below-Tg structural relaxation in network glass formers known also as long-term natural physical ageing is developed on the basis of the first-order kinetics. This kinetics in binary arsenic selenides was shown to obey a character stretched exponentional behavior being treated as sequence of aligning-shrinkage stages throughout the glassy matrix. © (2013) Trans Tech Publications, Switzerland. Source

Hacinliyan A.S.,Yeditepe University | Hacinliyan A.S.,Bogazici University | Skarlatos Y.,Yeditepe University | Skarlatos Y.,Bogazici University | And 10 more authors.
Journal of Non-Crystalline Solids | Year: 2014

Theory of chaos is shown to be adequately applied to analyze kinetics of natural physical aging revealed in structural relaxation of Se-rich As-Se glasses below glass transition. Kinetics of enthalpy losses induced by prolonged storage in natural conditions is used to determine phase space reconstruction parameters. The observed chaotic behavior (involving chaos and fractal consideration such as detrended fluctuation analysis, attractor identification using phase space representation, delay coordinates, mutual information, and false nearest neighbors) reconstructed via TISEAN is treated within potential energy landscape as diversity of multiple transitions between different basins-metabasins towards more thermodynamically equilibrium state, minimizing the free energy of the system. Natural physical aging, facilitates further atomic shrinkage of the glass backbone. © 2013 Elsevier B.V. Source

Balitska V.,Lviv Institute of Materials | Balitska V.,Lviv State University of Vital Activity Safety | Golovchak R.,Austin Peay State University | Kozdras A.,University of Opole | And 2 more authors.
Physica B: Condensed Matter | Year: 2014

Sigmoid behavior of natural physical ageing in glassy As 10Se90 reveals multi-step-wise growing kinetics of enthalpy losses. Phenomenological description of this kinetics can be adequately developed in terms of first-order relaxation processes, tending atomic structure from initial towards more thermodynamically equilibrium state. This kinetics is shown to obey characteristic stretched exponential behavior originated from a number of growing steps, attributed to the interconnected processes of chalcogen chain alignment and cooperative shrinkage of glass network. © 2013 Published by Elsevier B.V. Source

Shpotyuk O.,Lviv Institute of Materials | Shpotyuk O.,Jan Dlugosz University in Czestochowa | Balitska V.,Lviv Institute of Materials | Balitska V.,Lviv State University of Vital Activity Safety | And 2 more authors.
Journal of Alloys and Compounds | Year: 2011

Mixed Ni-Co-Cu oxymanganospinels of Cu 0.1Ni 0.8Co 0.2Mn 1.9O 4 composition with improved functional reliability are first developed for possible application as high-precise NTC thermistors. It is established the amount of additional rock-salt NiO phase in these ceramics, which was not externally introduced at the initial stages of ceramics processing, but extracted during sintering route occurs a decisive role to inhibit the parasitic degradation caused by thermal storage at the elevated temperatures. This effect is well revealed only in ceramics having a character fine-grain microstructure obtained due to injection of small amount of thermally transferred energy, while structural monolithization caused by great value of thermally transferred energy into ceramics bulk reveals an opposite influence. The fact, the ceramics with fine-grain microstructure and large content of rock-salt NiO extractions demonstrate the best suitability for stretched-exponential relaxation kinetics (the most appropriate one for describing degradation kinetics in structurally dispersive solids like ceramics) serves as additional confirmation to the above conclusion. © 2010 Elsevier B.V. All rights reserved. Source

Golovchak R.,Lehigh University | Golovchak R.,Lviv Institute of Materials | Kozdras A.,University of Opole | Balitska V.,Lviv Institute of Materials | And 3 more authors.
Journal of Physics Condensed Matter | Year: 2012

The long-term kinetics of physical ageing at ambient temperature is studied in Se-rich As-Se glasses using the conventional differential scanning calorimetry technique. It is analysed through the changes in the structural relaxation parameters occurring during the glass-to-supercooled liquid transition in the heating mode. Along with the time dependences of the glass transition temperature (Tg) and partial area (A) under the endothermic relaxation peak, the enthalpy losses (ΔH) and calculated fictive temperature (TF) are analysed as key parameters, characterizing the kinetics of physical ageing. The latter is shown to have step-wise character, revealing some kinds of subsequent plateaus and steep regions. A phenomenological description of physical ageing in the investigated glasses is proposed on the basis of an alignment-shrinkage mechanism and first-order kinetic equations. © 2012 IOP Publishing Ltd. Source

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