## Northern Kentucky University

#### Poster Title

Search for the Rigidity Transition in Lithium Oxide Silicate Glass System Using Modulated Differential Scanning Calorimetry

#### Institution

Northern Kentucky University

#### Faculty Advisor/ Mentor

Wayne Bresser; Chari Ramkumar; Kisa Ranasinghe

#### Abstract

The objective of this project was to determine the existence of the rigidity transition in glass compositional system, xLi2O*(1-x)SiO2 where 0 < x < 1, using Modulated Differential Scanning Calorimetry (MDSC). Accurate values of Tg were deduced using MDSC, a more sensitive variant of the traditional differential scanning Calorimetry. MDSC permits deconvoluting the total heat flow (Ht) into a reversing component, îHr, and a non-reversing component, îHnr. The delta-Hnr tracked the temperaturemodulations and provided a true measure of change in the heat capacity, delta-Cp and Tg, while the delta-Hnr captured the kinetic effects associated with changes in network configurations as a precursor to softening of the glass at Tg. Therefore the delta-Hnr term provided a measure of internal stress in the network glass. As the amount of lithium oxide increased, the results showed a local minimum in the delta-Hnr, between x = 0.31 and x = 0.33. The Tg showed a local maximum in the same compositional range. In conclusion, the rigidity transition in this xLi2O*(1-x)SiO2 glass system was observed in the compositional window 0.31 < x < 0.33.

Search for the Rigidity Transition in Lithium Oxide Silicate Glass System Using Modulated Differential Scanning Calorimetry

The objective of this project was to determine the existence of the rigidity transition in glass compositional system, xLi2O*(1-x)SiO2 where 0 < x < 1, using Modulated Differential Scanning Calorimetry (MDSC). Accurate values of Tg were deduced using MDSC, a more sensitive variant of the traditional differential scanning Calorimetry. MDSC permits deconvoluting the total heat flow (Ht) into a reversing component, îHr, and a non-reversing component, îHnr. The delta-Hnr tracked the temperaturemodulations and provided a true measure of change in the heat capacity, delta-Cp and Tg, while the delta-Hnr captured the kinetic effects associated with changes in network configurations as a precursor to softening of the glass at Tg. Therefore the delta-Hnr term provided a measure of internal stress in the network glass. As the amount of lithium oxide increased, the results showed a local minimum in the delta-Hnr, between x = 0.31 and x = 0.33. The Tg showed a local maximum in the same compositional range. In conclusion, the rigidity transition in this xLi2O*(1-x)SiO2 glass system was observed in the compositional window 0.31 < x < 0.33.