Guo, Xiaoju

Liu, Hao

Mauro, John C.

Yue, Yuanzheng

    Aalborg UniversitetGlass transition in mixed network former glassesLiu, Hao; Guo, Xiaoju; Mauro, John C.; Yue, YuanzhengPublished in:The 24th International Congress on Glass - AbstractsPublication date:2016Link to publication from Aalborg UniversityCitation for published version (APA):Liu, H., Guo, X., Mauro, J. C., & Yue, Y. (2016). Glass transition in mixed network former glasses: Insights fromcalorimetric measurements. In The 24th International Congress on Glass - Abstracts (pp. 120). InternationalCommission on Glass (ICG).General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.Downloaded from vbn.aau.dk on: April 30, 2017Glass transition in mixed network former glasses: Insights from calorimetric measurements    H. Liu1,2, X.J. Guo3, J.C. Mauro3, Y.Z. Yue1,2 1 State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China 2 Department of Chemistry and Bioscience, Aalborg University, DK-9200 Aalborg, Denmark 3 Science and Technology Division, Corning Incorporated, Corning, New York 14831, United States hal@bio.aau.dk  Modifier-free mixed network former glasses are technically important due to their special properties, e.g., low thermal expansion coefficient, low Young’s modulus, and high strain points ( ≥650 °C).1) In addition, many mixed network former glasses have high liquidus viscosities (>3×105 poise), which is a requirement for the fusion sheet manufacturing process.2) Some previous studies have shown the evolution of structural units with composition in ternary network former glasses.1),2) Moreover, it has been reported that there is a preference for Al-P instead of B-P association in quaternary network former glasses.3) In order to explore the change of the degree of connectivity in mixed network formers with composition, it is highly interesting to study the composition dependent glass transition temperature (Tg) of mixed network former glass. Now the questions arise: For this type of glass, how do the thermodynamic properties evolve with composition, such as Tg and Cp jump (ΔCp) during glass transition? By performing calorimetric measurements, can we gain an insight into the degree of distribution of different network formers? In this work, we explore the thermodynamic properties of B2O3-SiO2-P2O5-Al2O3 mixed network former glasses with a substitution of B2O3 for SiO2 using differential scanning calorimetry (DSC). Figure 1 shows that there are multiple crystallization peaks and two glass transition regions for each sample, and the addition of B2O3 causes the number of crystallization peaks increasing and the crystallization temperature decreasing. It has been recently reported the existence of three Tgs in an ionomer glass.4) Although our studied compositions are far away from the immiscible region in the B2O3-P2O5-SiO2 phase diagram if Al2O3 (4 mol% in all studied glasses) is considered to be replaced by B2O3, two Tgs exist in all studied glasses, implying the presence of two non-crystalline phases4). As shown in Figure 2, both of the two Tgs decrease linearly with addition of B2O3 content, suggesting that the network would be depolymerized with further addition of B2O3. Moreover, Tg1 decreases much faster than Tg2. The different changing rate of two Tgs may lead to Tg merging in a critical composition if we extrapolate the linear fitting lines as shown in Figure 2. As a measure of indirect thermodynamic fragility, the ΔCp during the glass transition is calculated. It increases about 20% when B2O3 content increasing from 16 mol% to 27 mol%, indicating that the mixed network former liquid becomes more fragile with the increase of B2O3 content.  400 500 600 700 800 900 10001.01.11.21.31.41.51.6300 500 700 900 1100DSC Output (arb. unit)T (°C)1st upscan10 K/minexo2nd upscan10 K/min(B2O3 mol%)  T (K)Cp (J g-1 K-1)17232931Figure1. The Cp curves for the 2nd upscan at a heating rate of 10 K/min subsequent to a cooling procedure at the same rate. Inset: DSC output for the 1st upscan at a heating rate of 10 K/min.  4 8 12 16 20 24 28 327008009001000Tg1Tg2Tg (K)B2O3 (mol%)Critical B2O3 (mol%): 4.63Figure 2. The evolution of Tg with composition. The dash lines are linear fitting. 1) R. E. Youngman, B. G. Aitken, J. E. Dickinson, Multi-nuclear NMR studies of borosilicophosphate glasses and micro foams, J. Non-Cryst. Solids 263-264 (2000) 111-116. 2) B. G. Aitken, R. E. Youngman, Borophosphosilicate glasses: properties and structure, Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B 47 (2006) 381-387. 3) R. E. Youngman, B. G. Aitken, Network structure of xB2O3-(22.5-x)Al2O3-7.5P2O5-70SiO2 glasses, Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B 50 (2009) 183-188. 4) M. T. Pedersen, K. V. Tian, C. Dobó-Nagy, G. A. Chass, G. N. Greaves, Y. Z. Yue, Phase separation in an ionomer glass: insight from calorimetry and phase transitions, J. Non-Cryst. Solids 415 (2015) 24-29. 

Glass transition in mixed network former glasses:Insights from calorimetric measurements

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Glass transition in mixed network former glasses:Insights from calorimetric measurements

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