Yue, Yuanzheng

Zhang, Y.F.

Zhao, D.H.

    Aalborg UniversitetEnthalpy relaxation and microstructure evolution in hyperquenched SiO2–Al2O3-ZrO2systemZhang, Y.F.; Zhao, D.H.; Yue, YuanzhengPublished in:The 24th International Congress on Glass - AbstractsPublication date:2016Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Zhang, Y. F., Zhao, D. H., & Yue, Y. (2016). Enthalpy relaxation and microstructure evolution in hyperquenchedSiO2–Al2O3-ZrO2 system. In The 24th International Congress on Glass - Abstracts (pp. 129). 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, 2017Enthalpy relaxation and microstructure evolution in hyperquenched SiO2–Al2O3-ZrO2 system  Y. F. Zhang1, D. H. Zhao2, Y. Z. Yue1,3 1Key Laboratory of Processing and Testing Technology of Glass & Functional Ceramics of Shandong Province, Qilu University of Technology, Jinan 250353, China 2Unifrax I LLC, Tonawanda, NY 14150, USA 3Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark Zhang-yanfei@hotmail.com    A study of the sub-Tg enthalpy relaxation in glass far from equilibrium is crucial for understanding nature of glass. Recently, considerable progress has been made towards understanding the sub-Tg enthalpy relaxation in glass by using the hyperquenching-annealing calorimetry (HAC) method 1,2) as well as modeling. However, most of the sub-Tg enthalpy relaxation studies have been done on stable oxide glass systems, i.e., those with low tendency to crystallization. Only a very few studies have been carried out on extremely unstable glasses.1) In order to get a broad picture about glass relaxation and glass transition, it is also necessary to investigate those extremely poor glass formers. Such investigation can provide valuable information on the structural heterogeneity in glass and liquid. In this work, we study sub-Tg enthalpy relaxation and microstructure evolution of an extremely unstable glass former, i.e., a ternary oxide system SiO2–Al2O3-ZrO2. This special glass system arouses our interests mainly from three aspects. First, it is a material with broad applications in high temperature insulation. Second, it is obtained by hyperquenching (~106 K/s) the liquid during which high potential energy is frozen in. In the subsequent sub-Tg annealing process, the frozen-in energy will be gradually released, providing opportunities to study its microstructure evolution and sub-Tg enthalpy relaxation. The amorphous nature of the as-produced glass is verified by the X-Ray Diffraction (XRD) pattern as shown in Figure 1. Thirdly, it is an extremely unstable glass against crystallization since its crystallization peak overlaps with the glass transition peak in the isobaric heat capacity (Cp) curve. The results show that the structural ordering can take place during multiple DSC upscans to a temperature just above the glass transition temperature. Strikingly, the structural ordering is not just in nanoscale as our previous findings in a binary SiO2-Al2O3 glass system3), but forms the zirconia crystal phase which can be verified by XRD (see Figure 1). Figure 2 shows the Cp curves of the hyperquenched (HQ) glass. The numbers near the Cp curves refer to the sequence of DSC upscans from 333 to1260 K at 20 K min−1. In addition, the dynamics of microstructure evolution during sub-Tg annealing is also studied by XRD, high resolution transmission electron microscopy (HRTEM) and nuclear magnetic resonance (NMR). This work provides insight into both the thermal and structural origin of the extremely poor glass forming ability in SiO2–Al2O3-ZrO2 glass.     20 40 60 802 (0)Intensity (AU) Fresh sample Fresh sample after multiple unscan in DSC         Zirconia                 600 900 12000.00.30.60.91.21.51453Numbers near curves: Upscan sequenceCp (Jg-1K-1)T (K)2Tg=1174 K      1) Y.Z. Yue, A. Angell, Clarifying the glass-transition behaviour of water by comparison with hyperquenched inorganic glasses, Nature 427 (2004) 717–720. 2) C.A. Angell, Y.Z. Yue, L.M. Wang, J.R.D. Copley, S. Borick, S. Mossa, Potential energy, relaxation, vibrational dynamics and the boson peak, of hyperquenched glasses J. Phys. Condens. Matter 15 (2003) S1051–S1068. 3) Y. F. Zhang, L. N. Hu, S. J. Liu, C. F. Zhu and Y. Z. Yue, Sub-Tg enthalpy relaxation in an extremely unstable oxide glass and its implication for structural heterogeneity, J. Non-Cryst. Solids 381 (2013) 23-28. Figure 2. Isobaric heat capacity (Cp) against temperature for the HQ SiO2–Al2O3-ZrO2 glass subjected to multiple DSC upscans. Structural ordering could take place during the multiple upscans in DSC.  Figure 1. XRD patterns of both the fresh sample (HQ SiO2–Al2O3-ZrO2 glass, in black) and the sample  after multiple (5) DSC upscans (in red).   

Enthalpy relaxation and microstructure evolution in hyperquenched SiO2–Al2O3-ZrO2 system

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Enthalpy relaxation and microstructure evolution in hyperquenched SiO2–Al2O3-ZrO2 system

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