Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates

Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates

Bibliographic Details
Main Author: Skipper, Charles
Language:English
Published: University of Cincinnati / OhioLINK 2019
Subjects:
Electrical Engineering
Glass
Fragility
Intermediate Phase
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=ucin1562672753116725
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-ucin15626727531167252021-08-16T05:10:40Z Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates Skipper, Charles Electrical Engineering Glass Fragility Intermediate Phase We examine the fragility index m(x) of (Na2O)x(B2O3)100-x (NBG) and (Li2O)x(B2O3)100-x (LBG) melts over a wide composition range 0 < x < 40% using Modulated -Differential Scanning Calorimetry (MDSC). Special care was taken to use dry and homogeneous glass specimen. Our results show evidence of broad minima in m(x) in the range 20=x=40% and 14=x=27% for NBG and LBG respectively, which are identified as fragility windows. Earlier, the enthalpy of relaxation at the glass transition temperature Tg , ?Hnr(x) of corresponding glasses were reported by Vignarooban et al. They observed square well-like reversibility windows in the same 20=x=40% and 14=x=27% composition ranges for NBG and LBG respectively. The correlation of the fragility windows with reversibility windows underscores that melt dynamics encode glass Topological phases, viz, strong melts give rise to isostatically rigid glasses also called the Intermediate Phase (IP)glasses, while fragile melts giving rise to either flexible or stressed-rigid glasses. Furthermore, for flexible glasses, m(x) increases with Tg(x), for Stressed -rigid glasses, the reverse is the case, i.e., m(x) decreases with Tg(x). Furthermore, the activation energy of enthalpy relaxation, Ea(x) deduced from the fragility index (m(x)) measurements display broad global minima in the fragility windows. The inverse of the activation energy, 1/Ea, which provides a measure of the configurational entropy change (Sc) of melts as they are cooled to Tg, show a global maximum in the IP. The latter finding confirms that the IP glasses are stabilized by their high configurational entropy determined by several structural groupings. These striking compositional trends are conspicuously absent in wet or heterogenous melts/glasses as noted by earlier reports, underscoring the crucial role of connectivity in determining these Topological properties of disordered networks. 2019-10-24 English text University of Cincinnati / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ucin1562672753116725 http://rave.ohiolink.edu/etdc/view?acc_num=ucin1562672753116725 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Electrical Engineering
Glass
Fragility
Intermediate Phase
spellingShingle Electrical Engineering
Glass
Fragility
Intermediate Phase
Skipper, Charles
Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates
author Skipper, Charles
author_facet Skipper, Charles
author_sort Skipper, Charles
title Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates
title_short Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates
title_full Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates
title_fullStr Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates
title_full_unstemmed Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates
title_sort melt dynamics correlated with glass topological phases in dry li- and na- borates
publisher University of Cincinnati / OhioLINK
publishDate 2019
url http://rave.ohiolink.edu/etdc/view?acc_num=ucin1562672753116725
work_keys_str_mv AT skippercharles meltdynamicscorrelatedwithglasstopologicalphasesindryliandnaborates
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