Download Equilibrium condition and physico-chemical effects of capillary

Equilibrium condition and physico-chemical
effects of capillary condensation of water at
crack tips in oxide glasses in moist air
M. Ciccotti, M. George, A. Grimaldi, G. Pallares
Laboratoire des Colloïdes, Verres et Nanomatériaux
Université Montpellier 2, France
C. Marlière
Géosciences Montpellier, UM2, France
FFAG4, Nov 2007, Shiga, Japan
Slow Crack Propagation
in Glasses
StressCorrosion
Critical
Fracture
~ nm/s
~ km/s
Effect of temperature and humidity
Sodalime glass
Wiederhorn, JACS (1967)
Wiederhorn and Bolz, JACS (1970)
Sample Geometry
DCDC
Double Cleavage Drilled Compression
σ
Opening
Mode
2a
c
σ a
KI =
c
0.375 + 2
a
Dimensions :
4x4x40 mm3
Crack
Propagation
σ
Polishing :
Mechanical + CeO2
RMS : 0.25 nm (10x10 µm2 area)
Load Cell (Deben)
Heads
Force
Veeco
gauge
Dimension 3100
Nanoscope IIIa
‘Tapping’ mode
• Controlled atmosphere : N2 + H2O
• RH : ~1% ⇒ 80% ± 2% T: 22.0 ± 0.5 °C
Slow Crack Propagation Observed by AFM
K-v curve
Time
RH
v
Time
v
v
KI
KI
Temperature anomaly on phosphate glass
Crichton et al, JACS (1999)
In-situ observation of a liquid condensate
50 nm
Height signal
100 nm
Silica glass
v = 0.1 nm/s
RH = 45 %
Wondraczek et al. JACS (2006)
Ciccotti et al. JNCS (2007, in press)
50 nm
10 nm
Phase signal
Energy dissipation due to the formation of
a capillary neck between tip and sample
Nanometric water
layer is both present
on the glass surface
and AFM tip
Histeretic
force-distance
behaviour is
responsible for a
net energy loss
at each contact
Zitzler et al., PRB (2002)
1
2
3
Capillary condensation
Hc
rK
H2O
Lc ~ 1 µm
Hc
• Mechanical equilibrium : Laplace equation
• Thermodynamical equilibrium : Kelvin relation
Irwin equation:
Lc =
f
• Critical distance : Hc
• Crack profile : 2uy(X)
Calibration of the crack opening profile
300
2U (nm)
1. FE Simulation
150
X (µm)
D. Ponson et al (2007), in preparation
0
100
200
2. Reflection
Interferometry
2
U
3.
Irwin model up to 30 µm !
Two limit hypotheses
A ) Slow evaporation : constant volume
L
KI
B ) Rapid evaporation : critical distance
H2O
Hc
L
Hc
H2O
Equilibrium
Experimental data support hypothesis B
Grimaldi et al. (2007, submitted)
The condensate length is determined by an
equilibrium condition !
No apparent dependence on velocity !
Why is the critical distance so large?
VdW model for
wetting surfaces
Hc = 2 rK +3 e
rK , e = f(RH) ~ nm
Effects to account for:
•
•
•
•
•
Surface roughness
Surface charge
Hydration forces
Ion exchange
Impurities
Entailments
1. Kinetical
H2O
H2O
H2O
H2O
H2O
H2O
H2O
or
H2O
H2O
Easier access of water
molecules at the crack tip
Reduction of region II
plateau at high humidity
Wiederhorn, JACS (1967)
Entailments
2. Mechanical
∆P~-100 atm inside the condensate (Laplace)
Closure effect
Affect chemical reactions
3. Chemical
Corrosion + Ionic exchange
Change in ionic concentration
pH
Wetting properties
H2O
H2O
CO2
Na+
Effect of pH on fracture in water
Silica glass
Wiederhorn et Johnson, JACS (1973)
Sodalime
Perspectives
A) New insights in the relation between the
parameters of subcritical crack growth and
1) the environmental condition
2) the glass chemistry
B) Exploring the fracture surface chemistry
through the effect on the wetting properties
Thank you for your attention !
Acknowledgements:
L. Wondraczek, Corning, France
E. Charlaix, L. Bocquet, LPMCN, Lyon
C. Frétigny, ESPCI, Paris
M. Ramonda, LAIN, Montpellier
F. Célarié, L. Ponson, CEA-Saclay
G. Prevot, JP Fromental, P. Solignac, LCVN, Montpellier