Fundamentals of the glassy state and the glass transition
Michael I. Ojovan Department of Nuclear Energy, IAEA
Joint ICTP-IAEA Workshop on Fundamentals of Vitrification and Vitreous Materials for Nuclear Waste Immobilization. 6 - 10 November 2017, Leonardo Building, ICTP, Trieste, Italy Outline
I. Background to solid melting and glass transition II. Bonds breaking on irradiation III. Viscosity on irradiation IV. Glass transition on irradiation V. Nuclear waste vitrification VI.Conclusions
2 I. Background to solid melting and glass transition
We are interested in understanding fundamentals of vitrification to ensure a safe utilisation of vitreous materials for immobilisation of nuclear wastes.
Jerzy Zarzycki, Professor of Materials Science at the University of Montpellier:
3 3 4 Finding Tg
log 푇푔 = 9 ÷ 13 6 Configuron Percolation Theory (CPT)
7 Depending on the kind of measurement performed, the glass transition thus manifests itself either as a continuous or as a discontinuous transformation. As for first-order thermodynamic properties (volume, enthalpy, entropy), there is no discontinuity of transport properties (viscosity, electrical conductivity, etc.), but a change in temperature dependence. In contrast, the variations of second-order thermodynamic properties across the glass transition range are rapid enough to be considered practically as discontinuities.
8 If the glass is just a very viscous liquid then …
Kauzmann paradox: A configurational contribution causes the heat capacity of a liquid to be generally higher than that of a crystal of the same composition. As a consequence, the entropy of the liquid decreases faster than that of a crystal when the temperature is lowered. Configuron Percolation Theory (CPT)
Solid
Crystalline structure (crystal) Solid-like material
12 Crystalline structure (crystal) Solid-like material
13 1D 2D 3D
Topological equivalence of objects
14 1D 2D
0D
1D 2D 3D
Broken bonds Fragmentation (disintegration) of objects
15 1D 2D
0D
1D 2D 3D An approach to melting of solids and glass transition: based on analysing broken bonds Since 2004
summary
16 0D
1D 2D 3D Thermal fluctuations break bonds causing solids melting
We account that: (i) Broken bonds are randomly generated within a solid; The higher the temperature the higher broken bond concentration; (ii) Broken bonds are mobile (Brownian motion) and can associate to form clusters. Clusters are larger at higher temperatures. 1D 2D 1D 91/48 2D 2.4 … 2.5
17 0D
1D 2D 3D
The melting temperature corresponds approximately to the bond percolation threshold
1996
2003
18 Configuron Percolation Theory (CPT)
19 Vitrification has been considered as a second order phase transition in which a supercooled melt yields, on cooling, a glassy structure and properties similar to those of crystalline materials e.g. of an isotropic solid material.
IUPAC. Compendium of Chemical Terminology. 66, 583, RSC, Cambridge 1997
20 20 C.A. Angell, K.J. Rao. Configurational excitations in condensed matter, and “bond lattice” model for the liquid-glass transition. J. Chem. Phys. 1972, 57, 470-481
Configuron Percolation Theory (CPT)
Increase of temperature
The physical picture of the glass transition in amorphous materials involves the representation of the topology change of disordered bonds lattice (network) and of its Hausdorff dimension. MI Ojovan, WE Lee. J. Physics: Condensed Matter 18, 11507 (2006) 21 21 Configuron Percolation Theory (CPT)
Material Tg, K , K err% Log() Reference for experiment Exper Tgth 1475 4 0.3 G. Urbain, Y. Bottinga, and P. Richet, Geochim. 1479 11.7 Cosmochim. Acta 46, 1061 (1982). SiO2 1480 -1 0.08 B.O. Mysen, P. Richer. Silicate glasses and melts.
Elsevier, Amsterdam, 2005. E.H. Fontana and W.A. Plummer, “A study of Viscosity- GeO2 786 795 9 1 13 Temperature relationships in the GeO2 and SiO2
Systems,” Phys. Chem. Glasses, 7, 139-46 (1966) H. R. Lillie, “Viscosity-Time-Temperature Relations in SLS 870 870 0 0 8.8 Glass at Annealing Temperatures,” J. Am. Ceram. Soc., 16, 619-31 (1933). Salol 220 250 30 14 9.8 Laughlin, W.T and Uhlmann D. R., J. Phys. Chem. 76, 2317 (1972) Cresol 220 242 22 10 8.83 Laughlin, W.T and Uhlmann D. R., J. Phys. Chem. 76, 2317 (1972) Diopside 1005 1109 104 10 11.5 B.O. Mysen, P. Richer. Silicate glasses and melts. Elsevier, Amsterdam, 2005.
22 Cooling rate (q) dependence
Bartenev (1951) – Ritland (1954) equation
Configuron Percolation Theory (CPT)
Theory
23 Sample size (L) dependence Experiment
Theory
24 Glass transition interval
Theory The percolation transition is not a sharp threshold, actually it is a region of non-zero width for systems of finite size [A. Coniglio. Cluster structure near the percolation threshold. J. Phys. A, 15, 3829–3844 (1982)].
25 1D 2D
0D
1D 2D 3D Thermal fluctuations break bonds and this leads to 1D 91/48 2D 2.4 … 2.5 solids melting
(i) Broken bonds are randomly generated within a solid; The higher the temperature the higher broken bond concentration; (ii)Broken bonds are mobile (Brownian motion) and can associate to form clusters. Clusters are larger at higher temperatures. 26 27 27 28 II. Bonds breaking on Irradiation
Unbinding (bond-breaking mobilising) reactions:
Network-breaking reaction:
29 30 31 III. Viscosity without and with Irradiation
No irradiation
32 The universal viscosity equation has been derived using Angell’s bond lattice model. It relates the viscosity to thermodynamic parameters of broken bonds (configurons) via CPT equation:
Configuron motion entropy
Configuron motion enthalpy
Configuron formation entropy
Configuron formation enthalpy
MI Ojovan, KP Travis, RJ Hand. J. Physics: Condensed Matter 19, 415107 (2007). 33 At low temperatures the activation energy of viscosity takes the full value QH=Hd+Hm because the concentration of broken bonds is low.
34 At high temperatures the activation energy is completely due to the energy needed to transfer a molecule or a configuron from its original position to the adjacent
vacant site e.g. QL= Hm.
Ojovan MI, Travis KP and Hand RJ 2007 J. Physics: Condensed Matter 19, 415107. 35 No irradiation
36 Irradiation
K. Zheng et.al., Nature Communications, 1:24, 1 (2011).
37 Irradiation
38 IV. Glass transition on irradiation
Irradiation
39 Irradiation
40 V. Vitrification of nuclear waste
Vitrification is the world- wide accepted technology for the immobilization of high level radioactive wastes. • Glass can accommodate the range of constituents that are present in the waste into the glassy structure. • The excellent durability of vitrified radioactive waste ensures a high degree of environmental protection.
41 Facility Waste Melter Operational period Performance data R7/T7, La Hague, France HLW IHC Since 1989/92 5573 tonnes in 14045 canisters to 2008, 6430 106 Ci AVM, Marcoule, France HLW IHC 1978 – 2008 1138 tonnes in 3159 canisters, 45.67 106 Ci R7, La Hague, France HLW CCM Since 2003 GCM: U-Mo glass WVP, Sellafield, UK HLW IHC Since 1991 1800 tonnes in 4319 canisters to 2007, 513 106 Ci DWPF, Savannah River, USA HLW JHCM 1996 – 2011 5850 tonnes in 3325 canisters, 40 106 Ci. WVDP, West Valley, USA HLW JHCM 1996 – 2002 500 tonnes in 275 canisters, 24 106 Ci EP-500, Mayak, Russia HLW JHCM Since 1987 6200 tonnes to 2013, 643 106 Ci (P. Poluektov has earlier reported on 8000 tonnes and 900 106 Ci to 2009 [1]) CCM, Mayak, Russia HLW CCM Pilot plant 18 kg/h by phosphate glass Pamela, Mol, Belgium HLW JHCM 1985-1991 500 tonnes in 2200 canisters, 12.1 106 Ci VEK, Karlsruhe, Germany HLW JHCM 2010 – 2011 60 m3 of HLW (24 106 Ci) Tokai, Japan HLW JHCM Since 1995 > 100 tonnes in 241 canisters (110 L) to 2007, 0.4 106 Ci. Radon, Russia LILW JHCM 1987-1998 10 tonnes Radon, Russia LILW CCM Since 1999 > 30 tonnes Radon, Russia ILW SSV4 2001-2002 10 kg/h, incinerator ash VICHR, Bohunice, Slovakia HLW IHC 1997-2001, upgrading work to restart operation 1.53 m3 in 211 canisters WIP, Trombay, India HLW IHPT5 Since 2002 AVS, Tarapur, India HLW IHPT Since 1985 18 tonnes to 2010 (110 103 Ci) WIP, Kalpakkam, India HLW JHCM Under testing & commissioning LLW JHCM Pilot plant since 1998. 1000 tonnes to 2000. LLW/HLW vitrification plants WTP, Hanford, USA Capacities: LLW plant 2 x 15 tonnes/day; HLW plant under construction. 2 x 3 tonnes/day Taejon, Korea LILW CCM Pilot plant, planned 2005 ? Saluggia, Italy LILW CCM Planned ?
R.A. Robbins, M.I. Ojovan. Vitreous Materials for Nuclear Waste Immobilisation and IAEA Support Activities. 42 http://www.dpaonthenet.net/article/52704/Glass-offers-improved- means-of-storing-intermediate-level-nuclear-waste.aspx
43 Waste vitrification is a mature technology demonstrated at industrial scale.
• Continued advancements in glass waste forms and nuclear waste vitrification technologies will be keys in enabling widespread deployment of nuclear energy.
• Additionally, the pressing issues regarding hazardous domestic disposal may also be effectively solved using vitrification technologies.
• Stricter regulations regarding waste characterization and land disposal for hazardous wastes will necessitate the need for effective waste treatment methods.
Understanding the glass transition is important to successfully reveal the rearrangements behind changes in the behaviour of amorphous materials on vitrification. This is also important in respect to long term safety of nuclear waste glasses.
44 VI. Conclusions
Vitrification is the world-wide accepted technology for the immobilization of high level radioactive wastes which provides a high degree of environmental protection.
Interpretation of the glass transition in terms of configuron percolation rather than transitions from Deborah numbers < 1 to > 1 is preferable.
45 Thank you! 46