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Direct Evidence for Topological Phases in Sodium Phosphate Glasses from Raman Scattering, Infrared Reflectance and Modulated DSC

Mohanty, Chandi P
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535377235070592

Abstract Details

2018, MS, University of Cincinnati, Engineering and Applied Science: Materials Science.
In the present Thesis, we report, to the best of our knowledge, the first experimental evidence of the presence of the three Topological Phases- Elastically flexible, Isostatic Intermediate Phase, and the Stressed-Rigid Phase in (Na2O)x(P2O5)100-x glasses in the 0 < x < 50% range. To observe these Topological phases especially dry and homogeneous bulk glasses were synthesized. The base material, P2O5, is extremely hygroscopic and required special handling. Bulk glasses were synthesized over a wide composition range and characterized by Calorimetric methods including DSC and Modulated-DSC, Optical methods including Raman scattering and Infrared Reflectance, and Mass density measurements. Furthermore, melt dynamics were established by measuring the variation in the melt fragility index using Modulated- DSC. From MDSC experiments we established compositional trends in the glass transition temperature Tg(x), the enthalpy of relaxation at Tg , ?Hnr(x) and observed a square-well like thermally reversing window (RW) in the 37.5(3)% < x < 46.0(2) % range fixing the isostatically rigid, and stress-free IP which shows characteristic features like non-aging of ?Hnr and a local minimum in the molar volumes, underscoring the compacted nature of glassy networks in the IP. From MDSC experiments performed starting from the melt and in a cool down mode, we deduced trends in the fragility index , m(x) of these glassy melts. These m(x) trends, remarkably, also display a square-well like minimum, defining the fragility window. And the Fragility window is found to coincide with the RW in composition space; a result that underscores that super-strong melts formed in the fragility window upon cooling give rise to glasses in the IP. These findings reinforce a general view that melt dynamics encode the glass topological phases. Raman scattering complemented by IR reflectance reveal rich line-shapes that have permitted us to decode the molecular structure of the glasses. The quasi-tetrahedral local structure, Ot=P(O1/2)3 of the base glass(P2O5), also labelled as Q3 species in the NMR notation (having 3 bridging Oxygen near neighbors) has been well characterized by 31P NMR and Raman scattering. On the other hand, the molecular structure at x = 50%, i.e., NaPO3 (Na- meta phosphate) is composed of long polymeric P-O-P-O-P chains. These chains are made up PO4 tetrahedra having two bridging Oxygen (Ob) atoms along the chains and two terminal Oxygen atoms (Ot). The terminal pair of Oxygen atoms are charge-compensated by a Na+ ion. The local structure of NaPO3 in NMR notation is labelled as Q2, since there are two bridging Oxygen near-neighbors. From Raman scattering and independently from IR reflectance measurements we deduced the glass compositional (x) variation in the fraction of the f(Q3) and f(Q2 ) units. The compositional variation in the fractions of f(Q3) and f(Q2 ) units from Raman and NMR, both closely track the expected variation based on Na2O partitioning between Q3 and Q2 units. The correlation between Raman and IR results on these fractions with the NMR ones reported earlier is demonstrated in this work for the first time.
Punit Boolchand, Ph.D. (Committee Chair)
Marc Cahay, Ph.D. (Committee Member)
Peter Kosel, Ph.D. (Committee Member)
Matthew Steiner, Ph.D. (Committee Member)
Vijay Vasudevan, Ph.D. (Committee Member)
127 p.
Engineering
Glass; Intermediate Phase; Topological Phases; Modulated DSC; Raman

Recommended Citations

Citations

  • Mohanty, C. P. (2018). Direct Evidence for Topological Phases in Sodium Phosphate Glasses from Raman Scattering, Infrared Reflectance and Modulated DSC [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535377235070592

    APA Style (7th edition)

  • Mohanty, Chandi. Direct Evidence for Topological Phases in Sodium Phosphate Glasses from Raman Scattering, Infrared Reflectance and Modulated DSC. 2018. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535377235070592.

    MLA Style (8th edition)

  • Mohanty, Chandi. "Direct Evidence for Topological Phases in Sodium Phosphate Glasses from Raman Scattering, Infrared Reflectance and Modulated DSC." Master's thesis, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535377235070592

    Chicago Manual of Style (17th edition)

ucin1535377235070592
162
© 2018, some rights reserved.Creative Commons License Direct Evidence for Topological Phases in Sodium Phosphate Glasses from Raman Scattering, Infrared Reflectance and Modulated DSC by Chandi P Mohanty is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.