Elasticity, Vibrations, and Corrosion Mechanisms at Nanoscale in Oxide Glasses

Transcription

1 Elasticity, Vibrations, and Corrosion Mechanisms at Nanoscale in Oxide Glasses Bernard Hehlen Laboratoire charles Coulomb, University Montpellier II and CNRS The Physics of Glass Group in few keywords Fracture, stress corrosion mechanisms (AFM) M. George, A-C.Genix Elasticity, plasticity, High pressure, vibrations (Brillouin scattering) B.Rufflé, M. Foret, R. Vacher, C. Weigel Vibrations and structure (Raman & Hyper-Raman scattering) B. Hehlen In close connection with The numerical simulation group (classical MD & ab-initio) S. Ispas, W. Kob VibrationalOptical Spectroscopies from GHz to THz Brillouin, IR-absorption, Raman (tunable lasers), hyper-raman

2 Elasticity, Vibrations, and Corrosion Mechanisms at Nanoscale in Oxide Glasses Bernard Hehlen Laboratoire charles Coulomb, University Montpellier II and CNRS The Physics of Glass Group in few keywords Fracture, stress corrosion mechanisms (AFM) M. George, A-C.Genix Elasticity, plasticity, High pressure, vibrations (Brillouin scattering) B.Rufflé, M. Foret, R. Vacher, C. Weigel Vibrations and structure(raman & Hyper-Raman scattering) B. Hehlen In close connection with The numerical simulation group (Classical MD & ab-initio) S. Ispas, W. Kob VibrationalOptical Spectroscopies from GHz to THz Brillouin, IR-absorption, Raman (tunable lasers), hyper-raman

3 Fracture and stress corrosion mechanisms : an Atomic Force Microscopy study Sample geometry σ DCDC Double Cleavage Drilled Compression 2a c a σ Opening K I = c Mode a + 2 Dimensions : σ Crack Propagation 4x4x40 mm 3 Polishing : Mechanical + CeO 2 RMS : 0.25 nm (10x10 µm 2 area)

4 Slow crack propagation in glasses by AFM

5 In situ observation of liquid condensate Signal de hauteur 100 nm Silice Suprasil 311 v = 0.1 nm/s RH = 45 ± 1 % AFM NS3 (AM AFM) Signal de Phase

6 Glass-water interactions in corrosion Chemical bond-by-bond breaking at the crack tip Damage in volume due to the water diffusion Stress Water diffusion OH contents increases Wiederhorn and Bolz, JACS (1970) Michalske et Bunker, J. Appl. Phys. (1984) + Ion exchange leaching (e.g. Na + ) Changes in mechanical properties (essentially weakening of the vitreous structure) Tomozawa, Ann Rev Mat Sci (1996)

7 Profile of the condensate? Hypothesis A: Slow evaporation constant volume Hc Hc L Hypothesis B: Stress K I Fast evaporation constant critical width Hc (thermodynamic equilibrium condition) Hc H 2 O Hc L H 2 O L

8 Experimental answer A B Grimaldi et al, PRL(2008)

9 Influence on crack propagation Kinetic effect Crack velocity increases with humidity H 2 O H 2 O H 2 O but H 2 O H 2 O Crack velocity Wiederhorn, JACS (1967) 100% RH 0% Humidity Reduction of the transport limited regime Stress K I Mechanical effect P~-100 atm (<0!) inside the condensate (Laplace) Stress Silice Suprasil 311 RH = 40 ± 3 % T = 22 ± 0.5 C Closure effect Crack length(mm)

10 Chemical effect : alkaline diffusion Sodalime glass, 45% RH, V 1 nm/s 30 nm 5 µm 1. Tensile stress 2. Sodium diffusion toward the crack tip 3. Water layer thickens 4. Accelerated corrosion Célarié et al., JNCS (2007) Corrosion + Ionic exchange Change in ionic concentration H 2 O H 2 O Na + ph CO 2 Wetting properties

11 Perspectives Determination of stress-strain field around the crack tip. non-linear behaviour (simulations) Link between macroscopic and nanoscopic scales : Simulations Experiments?? AFM, FEM, Near field opt. spectroscopies Non-linear elastic zone < 10 nm in SiO 2 Han et al. submitted to PRL

12 3D micro-brillouin mapping of a Vickers indentation in a soda-lime silicate glass Mechanical behavior of glasses: brittle but plastic at micro-scale and below Indentation test, crack tip Typical scales: nano to micrometers shear flow + permanent densification (a few % for a window glass, up to 20% for SiO 2 ) 20 µm Nanoscale hardly accessible by strandard spectroscopic tools µm-indentation

13 Principles of BrillouinScattering Light scattering from thermal agitation Scattered light has a different frequency ν s, depends on: sound velocity v and optical index n ± elastic moduli and density From spectra analysis: sound attenuation α or internal friction λ>>a continuous elastic medium Q 1 = δν Mechanical properties B = ν s ν0 = ± 2παv δν High resolution µ-brillouin spectrometer at the L2C-Montpellier B 2nv λ 0 θ sin 2 Frequency resolution 25 MHz 4-pass PFP interferometer + + Optical microscope SFP interferometer Spatial resolution 1.2x1.2x6 µm 3

14 Brillouin spectra of indented soda-lime silicate glasses 2 kg Vickers indentation pristine (a) 20 µm Counts ν B = GHz (b) Frequency shift (GHz) SGG Planilux Float Glass 5 µm beneath the surface

15 Brillouin spectra of indented soda-lime silicate glasses 2 kg Vickers indentation pristine (a) 20 µm Counts Counts ν B = GHz (b) Frequency shift (GHz) ν B = GHz (c) Frequency Shift (GHz) SGG Planilux Float Glass 5 µm beneath the surface

16 Counts Brillouin spectra of indented soda-lime silicate glasses kg Vickers indentation pristine 0 (a) 20 µm (d) ν B = GHz Counts Counts Frequency shift (GHz) ν B = GHz (b) Frequency shift (GHz) ν B = GHz (c) Frequency Shift (GHz) SGG Planilux Float Glass 5 µm beneath the surface [Tran et al., APL 2012] Zone Pristine Center ν B (GHz) ν B change: ~0.93 GHz Maximum at the center

17 ν s ρ Calibration : Brillouin scattering in densified samples (from T. Rouxel-Renne) Simple approach : Densification of 6.3% linear increase of 0.93 GHz (density gauge) [Tranet al., APL 2012] Float Glass Measured indented area Top view 20 µm Vickers indentation 2D Isotropic density gradient in agreement with - luminescence micro-spectroscopy - and Raman micro-spectroscopy [Perriot et al., Phil. Mag. 2010] [Deschamps et al., J. Phys. -Condens. Matter 2011] Microscopic origin of the densification???

18 v-sio 2 has an open network structure O Si Permanent densification : θ Si θ O Si Raman Scattering in permanently densifiedsilicas, d-sio 2 f 2 V = ρ s = 5.73 g/cm 3 v SiO 2 ρ SiO f as compared to v-geo 2 V 0. GeO 54 2 Reduction of the Si-O-Si angle θ In the network and in the small rings (?) ρ SiO 4 tetrahedraremain unchanged modification of the Raman spectra S 4-fold (Y.Inamura, M. Arai, et al. JNCS 2001) Puckering of the ring network + bond redistribution SiO 2 is filled of voids Is it possible to get quantitativestructural information on the local structure through the Raman spectra? 3-fold

19 )()(()Normalized Raman intensities ρ=2.63 g/cm 3 N (ω)(rel. units) I N ρ=2.43 RS(ω ρ=2.20 )I N I RS N n R D 1 D 2 RS 1 ω I ω ω = 3 (ω ρ ω s )[ n + 1 ] Glass density I RS N ω Coupling-to-light coefficient of the mode σ C σ g σ (ω For bending modes (σ= R, D 1, D 2 ) : C σ ω 2 s)[shuker& Gammon 1970] Density of state of the mode σ [B. Hehlen JPCM2010]

20 )(Density of states of O-bending modes Density of states g R IN ω g ω )B = 2 ω ( ω) dω (RS After normalization by C B (ω) : C te for the 3 glasses Angular-frequency relation g B (ω) (r.u.) ρ= 2.63 g/cm 3 ρ= 2.43 g/cm 3 ρ= 2.21 g/cm 3 R D 1 D Frequency (cm -1 ) O Si θ Si cosθ 2 ω For the R-band and also in the small rings!!

21 Si-O-Si angle θin d-sio 2 [B. Hehlen, J.Phys.: Cond Matter 2010] R-band Small rings : θ θ n= 3 n= 4 Network angle : θ n n 6 Max. of the distribution n> 6 Average angle

22 Si-O-Si angle θin d-sio 2 [B. Hehlen, J.Phys.: Cond Matter 2010] RMN (Devine et al. 1987) R-band Small rings : θ θ n= 3 n= 4 Network angle : θ n n 6 n> 6 Max. of the distribution Average angle

23 Si-O-Si angle θin d-sio 2 [B. Hehlen, J.Phys.: Cond Matter 2010] RMN (Devine et al. 1987) R-band Small rings : θ θ n= 3 n= 4 Network angle : θ n n 6 n> 6 Max. of the distribution Average angle Simulations (Rahmani, Benoit, PRB,2003)

24 Si-O-Si angle θin d-sio 2 [B. Hehlen, J.Phys.: Cond Matter 2010] RMN (Devine et al. 1987) R-band Small rings : θ θ n= 3 n= 4 Network angle : θ n n 6 n> 6 Max. of the distribution Average angle Simulations(Matsubara, Ispas, Kob, 2009) Simulations (Rahmani, Benoit, PRB,2003)

25 Si-O-Si angle in sodo-silicates SiO 2 4SiO 2 :Na 2 O (NS4) 2SiO 2 :Na 2 0 (NS2) P(θ) Intens sity P(θ Si-O-Si ) SiO 2 NS4 NS2 Distribution of Si-O-Si angles (computer simulations) NS2 NS4 SiO 2 Boson peak From Raman spectra Frequency Angle g B (ω) P(θ) (Truflandier, Ispas,Charpentier) (Ispas et al PRB 2001) Angle ( ) Comparison with the Raman Spectra : Frequency Angle g B (ω) P(θ)

26 Si-O-Si angle in sodo-silicates SiO 2 20Na 2 O:80SiO 2 (NS4) 33Na 2 0:67SiO 2 (NS2) P(θ) Intens sity P(θ) SiO 2 NS4 NS2 Boson peak From Raman spectra Frequency Angle g B (ω) P(θ) From computer (Truflandier, Ispas,Charpentier) simulations (Ispas et al PRB 2001) Angle ( ) Not perfect, but in qualitative agreement Angle at maximum of the distribution?

27 Si-O-Si angle in sodo-silicates SiO 2 Most probable angle (max. of the distribution) experimental simulation Angle ( ) NS4 NS3 NS2 NS1.5 Same trend!! % mol. Na 2 O

28 )(Relative densityof smallrings D 1 D 2 I RS N ω C σ g σ (ω Rigidstructures weak θ-dependence with ρ C σ (ρ) C te A σ ω )incoherent scatterers And RS = d max = I ( ω ) d ω N ω min N ω ω max min g σ ( ω) dω N σ σ Number of rings The Area of I RS (D 1, D 2 ) Numberof ring N Raman Raman + Time-domain Raman scattering (ISRS) ISRS

29 (Pasquarello et al. PRL 2003) Densityof smallrings in d-sio 2 Comparison Raman / ISRS (J. Burgin et al. PRB 2008) 2.20 g/cm g/cm 3 D 1 : 1 Ring / 555 SiO 2 D 1 : 1 Ring / 380 SiO 2 D 2 : 1 Ring / 670 SiO 2 D 2 : 1 Ring / 150 SiO 2 Concentration of rings is very small Relative ring density RS ISRS (3-fold) D 2 D 1 (4-fold) Increase of the threefold rings (denser structures) Concentration of fourfold rings Cte Density ρ (g/cm 3 ) Possible scenario upon densification : large rings (n 5) 4-fold rings (D 1 ) 4-fold rings (D 1 ) 3-fold rings (D 2 )

30 Summary Elasticity, plasticity, and structure of glasses : Observation of mechanical damages (AFM) - Crack propagation - Stress corrosion mechanisms - Plastic deformations (polymers) Continous elastic medium properties (Brillouin Scat.) - Densification - Elastic constants - Sound attenuation (or internal friction) - Shear strain Spatial resolution nanometer micrometer Atomic structure (Raman, Hyper-Raman) micrometer - Si-O-Si angles -Density of small rings - Mid-term project : Tip-Enhanced Raman Scattering (TERS) sub µm to nm