Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization
Melt dynamics and glass Topological phases of especially dry and homogenized binary AsxS100−x melts/glasses are examined in Modulated-DSC, Raman scattering, and volumetric experiments. In the S-rich glasses (12% < x < 23%), direct evidence for the elusive 537 cm−1 stretch vibrational m...
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Frontiers Media S.A.
2019-07-01
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| Series: | Frontiers in Materials |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fmats.2019.00166/full |
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| author | Soumendu Chakravarty Ralph Chbeir Ping Chen Matthieu Micoulaut Punit Boolchand |
| author_facet | Soumendu Chakravarty Ralph Chbeir Ping Chen Matthieu Micoulaut Punit Boolchand |
| author_sort | Soumendu Chakravarty |
| collection | DOAJ |
| description | Melt dynamics and glass Topological phases of especially dry and homogenized binary AsxS100−x melts/glasses are examined in Modulated-DSC, Raman scattering, and volumetric experiments. In the S-rich glasses (12% < x < 23%), direct evidence for the elusive 537 cm−1 stretch vibrational mode of the Quasi-Tetrahedral (QT), S = As(S1/2)3, local structure is observed in FT-Raman scattering once melts are homogenized and glasses cycled through Tg+10°C for an extended period. The enthalpy of relaxation at Tg, ΔHnr(x), fragility index, m(x), Molar volumes, Vm(x) each display three distinct regimes of variation. Specifically, m(x) displays a Gaussian like global minimum (fragility window), and ΔHnr(x) displays an abrupt square-well like variation (reversibility window), while Vm(x) displays a Gaussian-like local minimum (Volumetric window) in the isostatically rigid phase (22.5% < x < 28.5%). At low x (< 20%) in the Flexible phase, glasses are segregated with a S8-rich nanophase that decouples from the As-S glassy backbone. At medium x (22.5% < x < 28.5%) glassy backbones form an isostatically rigid phase displaying a vanishing ΔHnr(x) term, and compacted structures with corresponding melts being superstrong (m < 20). At high x (28.5% < x < 40%) in the Stressed-Rigid phase, glasses possess an increasing ΔHnr(x) term, and melts become increasingly fragile, with m(x) >20 as x increases. Taken together, these results underscore that superstrong melts yield isostatically rigid glasses, while fragile ones form either Flexible or Stressed-rigid glasses upon cooling. The onset of the rigidity transition near <r> = 2.22, instead of the usual value of <r> = 2.40, is identified with presence of QT local structures in addition to Pyramidal As(S1/2)3 local structures in the glassy backbone, and with a small but finite fraction of polymeric Sn chains being decoupled from the backbone. |
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| institution | Directory Open Access Journal |
| issn | 2296-8016 |
| language | English |
| last_indexed | 2024-12-13T15:43:35Z |
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| spelling | doaj.art-fefb5cc17d7b41458acf90ceb4e4d1c02022-12-21T23:39:46ZengFrontiers Media S.A.Frontiers in Materials2296-80162019-07-01610.3389/fmats.2019.00166471975Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass HomogenizationSoumendu Chakravarty0Ralph Chbeir1Ping Chen2Matthieu Micoulaut3Punit Boolchand4Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, United StatesDepartment of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, OH, United StatesDepartment of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, OH, United StatesLaboratoire de Physique Théorique de la Matière Condensée, CNRS UMR 7600, Sorbonne Université, Paris, FranceDepartment of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, OH, United StatesMelt dynamics and glass Topological phases of especially dry and homogenized binary AsxS100−x melts/glasses are examined in Modulated-DSC, Raman scattering, and volumetric experiments. In the S-rich glasses (12% < x < 23%), direct evidence for the elusive 537 cm−1 stretch vibrational mode of the Quasi-Tetrahedral (QT), S = As(S1/2)3, local structure is observed in FT-Raman scattering once melts are homogenized and glasses cycled through Tg+10°C for an extended period. The enthalpy of relaxation at Tg, ΔHnr(x), fragility index, m(x), Molar volumes, Vm(x) each display three distinct regimes of variation. Specifically, m(x) displays a Gaussian like global minimum (fragility window), and ΔHnr(x) displays an abrupt square-well like variation (reversibility window), while Vm(x) displays a Gaussian-like local minimum (Volumetric window) in the isostatically rigid phase (22.5% < x < 28.5%). At low x (< 20%) in the Flexible phase, glasses are segregated with a S8-rich nanophase that decouples from the As-S glassy backbone. At medium x (22.5% < x < 28.5%) glassy backbones form an isostatically rigid phase displaying a vanishing ΔHnr(x) term, and compacted structures with corresponding melts being superstrong (m < 20). At high x (28.5% < x < 40%) in the Stressed-Rigid phase, glasses possess an increasing ΔHnr(x) term, and melts become increasingly fragile, with m(x) >20 as x increases. Taken together, these results underscore that superstrong melts yield isostatically rigid glasses, while fragile ones form either Flexible or Stressed-rigid glasses upon cooling. The onset of the rigidity transition near <r> = 2.22, instead of the usual value of <r> = 2.40, is identified with presence of QT local structures in addition to Pyramidal As(S1/2)3 local structures in the glassy backbone, and with a small but finite fraction of polymeric Sn chains being decoupled from the backbone.https://www.frontiersin.org/article/10.3389/fmats.2019.00166/fullmodulated differential scanning calorimeter (MDSC)Ramanmolar volumetopological constraint theoryconfigurational entropy |
| spellingShingle | Soumendu Chakravarty Ralph Chbeir Ping Chen Matthieu Micoulaut Punit Boolchand Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization Frontiers in Materials modulated differential scanning calorimeter (MDSC) Raman molar volume topological constraint theory configurational entropy |
| title | Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization |
| title_full | Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization |
| title_fullStr | Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization |
| title_full_unstemmed | Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization |
| title_short | Correlating Melt Dynamics and Configurational Entropy Change With Topological Phases of AsxS100–x Glasses and the Crucial Role of Melt/Glass Homogenization |
| title_sort | correlating melt dynamics and configurational entropy change with topological phases of asxs100 x glasses and the crucial role of melt glass homogenization |
| topic | modulated differential scanning calorimeter (MDSC) Raman molar volume topological constraint theory configurational entropy |
| url | https://www.frontiersin.org/article/10.3389/fmats.2019.00166/full |
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