Neville Greaves. Visualising Glass. Mathematical and Physical Sciences, University of Wales, Aberystwyth. Si K 5fs per frame K 2 O 5

Transcription

1 Visualising Glass Neville Greaves Mathematical and Physical Sciences, University of Wales, Aberystwyth Glass Learning Series: prepared for and produced by the International Material Institute for New Functionality in Glass An NSF sponsored program material herein not for sale Available at K 2 Si 2 O K 5fs per frame

2 Welsh Physics Teachers Conference Builth Wells Thursday 10 October 2002 history glass formation visualisation glass transition computer simulation Glass what its cracked up to be and more glass structure Patrick Reyntiens - Homage to Hector Bérlioz Photograph provided courtesy of Patrick Reyntiens

3 History

4 Natural glass Very rapid quench = natural glass

5 Volcanic Glass glassy toes ropy lava Pele s hair pitchstone froth tear drops

6 History If you want to produce zaginduru-coloured glass, you grind, separately, ten minas of immanakku-stone, fifteen minas of naga-plant ashes (and) 1 2/3 minas of White Plant. You mix (these) together. You put (them) into a cold kiln which has four openings (literally eyes) and arrange (the mixture) between the openings. You keep a good smokeless fire burning until the metal (molten glass) becomes fritted. You take it out and allow it to cool off. You grind it finely again. You collect in a clean dabtu-pan. You put into a cold chamber kiln. You keep a good smokeless fire burning until it glows golden yellow. You pour it into a kiln-fired brick and this is called (zuku-glass). Assyrian recipe 3500 BC

7 History...with great wonder I observe that fire is almost everywhere the active agent. Fire takes in sand and gives back, now glass, now silver... now lead, now pigments, now medicines... Pliny, Natural History (68AD) p. xxxvi

8 History the Romans invented glass blowing between 1 BC and 1 AD also dichroic glass Lycurgus Cup

9 History the Venetians learned to fashion and decorate glass starting around the Renaissance Venetian filigrana tazza 16 th 17 th century

10 History flat glass manufacture was perfected in Britain opening of the Great Exhibition 1 st may 1851 in the Crystal Palace by Queen Victoria D Winfield

11 History Glass Sculpture Dale Chuhuly Venturi Window at the Seattle Art Museum.

12 Glass Formation

13 Glass Formation network Sand SiO % modifiers Soda Na 2 O 13% Lime CaO 9.3% also Al 2 O 3 K 2 O MgO Fe 2 O 3 batch containing crystalline ingredients and glass cullet on the way into the glory hole

14 Glass Formation float glass process floating molten glass on liquid tin

15 architectural glass Palace of Justice Washington dc

16 Glass Formation Glass Transition temperature below which viscosity is too great for crystallisation to occur Molar Volume Glass Glass Transition Supercooled Liquid T g T m Crystal Temperature Melting Liquid

17 SAMPLE FOUNDARY Preparation of a YA20 glass y melting three glass pieces to ~2000 C and cooling Molar Volume Glass Glass Transition Melting Supercooled Liquid T g T m Liquid Crystal Temperature

18 SAMPLE FOUNDARY Preparation of crsytalline Al 2 O 3 from melt at 2500 C Molar Volume Glass Glass Transition Melting Supercooled Liquid T g T m Liquid Crystal Temperature LASER cutoff Temperature ( C) Free cooling of the liquid Recalescence Time(s)

19 Shear in Solids and Liquids z x Elastic Shear A F σ = Newton s Law of Viscosity F v A F x A z Shear Stress σ = Gγ Shear Strain γ = x z G, Shear Modulus η, Viscosity Institute of Mathematical and Physical Sciences University of Wales, Aberystwyth dγ σ =η dt dγ = dt σ = GHFγ x = vxτ G HF, High Frequency Modulus σ = GHF dγ τ dt η = GHFτ Shear Strain Rate v z Maxwell s Viscosity Equation x τ, Structural Relaxation Time

20 22 Decades of Viscosity Room Tem perature Pas Log Viscosity Supercooled Liquid Glass G lass Transition Flow Point S tra in P o in t T g Pas Pas 10 4 Pas Liquid T M M e ltin g P o in t 10 Pas 1/Tem perature Water at 0 C Pas Institute of Mathematical and Physical Sciences University of Wales, Aberystwyth

21 Institute of Mathematical and Physical Sciences University of Wales, Aberystwyth Crystalline Network

22 Institute of Mathematical and Physical Sciences University of Wales, Aberystwyth Continuous Random Network

23 Atomic Structure and Dynamics of Glass

24 Modelling the Atomic Structure of Glass Modified Random Network network SiO % modifiers Na 2 O 28.5% EXAFS and The Structure of Glass Greaves G N, J. Non-Cryst. Solids, 71,, (1985)

25 Inter-atomic potentials U short range - repulsive thermal expansion U = A/r 12 -B/r 6 Lennard-Jones Potential du/dr = 0 r 0 r inter-atomic separation long range - attractive figure 5

26 MD Simulation Pair Distribution Functions and Alkali Channels network cations modifier cations Cation Microsegregation and Ionic Mobility in Mixed Alkali Glasses Nature 356, (1992)

27 MD Simulation compared to Neutron Scattering Na 2 Si 2 O 5 Glass Si-O O-O Radial Distribution Function Na-O Structure Factor Computer Simulation of Sodium Disilicate Glass Smith W, Greaves GN and Gillan MJ J. Chem. Phys. 103, (1995) First Sharp Diffraction Line

28 Atomic Mean Square Displacements 40 MSD MSD D=1/6 d(msd)dt D = D 0 exp (W/k B T) K 2 Si 2 O 5 W = 0.6 ev MD Simulation- Modelling Ionic Diffusion Si4+ Si4+ O2- O2- K+ K Time (fs)

29 Virtual Reality Techniques isosurfaces, ion tracks

30 isosurfaces static alkali channels metaballs Channel formation and intermediate range order in sodium silicate melts and glasses Meyer A, Horbach J, Kob W, Karg F and Schober H, 2004, PRL 93, /4

31 network isosurface Alkalis

32 network isosurface channels & chains Silicate chains Alkali channels

33 K K network isosurface channels & chains O O Si O O K K K K K K 2 Si 2 O K 5fs per frame

34 Ion tracks - K 2 Si 2 O 5 correlated alkali motion K 3 K 2 10 ps cf Boson Peak period 6 ps K 4 K 1 linear tracks

35 ion tracks - Na 2 Si 2 O 5 correlated alkali motion Na 3 Na 4 Na 2 Na 2 Na 1 intersecting tracks 10 ps cf period at Boson Peak 6 ps

36 Visualising cooperative dynamics local frequencies

37 ion tracks -Na 2 Si 2 O 5 modifier sites identified by immersive inspection Lévy flight dynamics Habasaki J & Okada I, PRB 55, 6309 (1997) vacancy free structure forward hops assisted by motion proceeding ion mobile and immobile ions Funke K, Bruckner S, Cramer C and Wilmer D, J. Non-Cryst. Solids , 921 (2002) localised hopping 100 ps

38 local frequencies sodium, oxygen, silicon Intensity (FT.ν 2 ) Na ω Na ω 1 O ω 3 ω 2 ω 4 Si alkali rattling modes ν Hz SiO 4 tetrahedra bending & stretching modes

39 visualising co-operative operative ion dynamics O 1 Positional Correlation Na 1 reference Ψ 3 distance is greatest correlation O 3 shared frequencies Na 2 Na 3 O 2 between network (NBO) and modifiers (Na) alkalis approximately synchronised in anti-phase..huygens clocks.

40 visualising cooperative ion dynamics O 1 Directional Correlation O 1, O 2 and O 3 are shared nonbridging oxygens (NBOs) Na 1 reference O 2 Ψ 1 direction weakest correlation Na 2 Na 1, Na 2 and Na 3 involved in correlated motion over 10ps O 3 Na 3 probability is that ions are moving in opposite directions

41 shared low frequencies sodium, oxygen, silicon Boson Peak SiO 2 ω BP Intensity (FT) ω Na O Na Si if ions are synchronised at low frequencies, Lévy flight is excited by mode-locking behaviour ν Hz alkali rattling modes

42 history vessels Virtual Reality ionic diffusion stained glass volcanoes random networks architecture glass transition shear and flow windows frozen liquid Peter Drieser Price of Oil Photograph provided courtesy of Peter Drieser