Surface Chemistry of Glass - · PDF fileSurface Chemistry of Glass: Interfacial water and...
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Surface Chemistry of Glass: Interfacial water and mechanochemical properties
Hongtu He, Laura C. Bradley, Zachary R. Dilworth,
Carlo G. Pantano, and Seong H. Kim
Materials Research Institute, Pennsylvania State University
Engineering Conferences International Functional Glasses
January 6 -11, 2013 Sicily, Italy
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Acknowledgement
• Laura Bradley, Zach Dilworth – undergraduate REU through support from NSF IMI for New Functionality in Glass (Grant No. DMR-0844014).
• Hongtu He – an exchange student from China through support from NSF IMI for New Functionality in Glass (Grant No. DMR-0844014).
• This work was supported by National Science Foundation (Grant No. DMR-1207328).
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Surface properties in ambient conditions are not
intrinsic properties of materials;
they are sensitive to extrinsic factors… (often, unpredictable & difficult to understand)
vacuum
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Effects of vapor adsorption on SiO2/Si wear
0 100 200 300 400 500 600-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
He
igh
t (
m)
Width (m)
dry
humid
n-pentanol vapor
(Nominal PHertzian = 360 MPa)
Optical profilometry
0.7 N load on 3mm dia fused silica ball sliding on SiO2/Si
Barnette, Asay, Kim, Guyer, Lim, Janik, and Kim, Langmuir 2009, 25, 13052–13061
In alcohol vapor
In dry
In humid
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MEMS Reliability Taxonomy
Romig, et. al. Acta Materialia 51 (2003) 5837
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6
Unreliable Dynamic Interfaces have Limited the Development of Complex MEMS
mechanical lock: enabled by 24 independent A/B events
500 m
500 m
M. T. Dugger
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"Courtesy Sandia National Laboratories, SUMMiT™ Technologies, www.sandia.gov/mstc"
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MEMS side-wall tribometer
20m
Initially coated with “lubricious” fluorinated self-assembled monolayer
In collaboration with M. Dugger (Sandia)
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100
101
102
103
104
105
106
107
0.0
0.2
0.4
0.6
0.8
1.0
Fri
ctio
n C
oef
f.
Cycles
Device fails once the lubricious coating layer is worn off
and the adhesion of the newly exposed bare surfaces
becomes larger than the actuation force.
Device fails when
Fadhesion > Facuation
2 Minutes @100 Hz operation
D. B. Asay, M. T. Dugger, and S. H. Kim, Tribol. Lett. 2008, 29, 67.
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In the presence of alcohol vapor, the device
does not fail …
MEMS
tribometer
Load
Slide
100
m
10 m
1 00
1 01
1 02
1 03
1 04
1 05
1 06
1 07
1 08
0 .0
0 .2
0 .4
0 .6
0 .8
1 .0
1 0-7
1 0-6
1 0-5
1 0-4
1 0-3
1 0-2
1 0-1
1 00
1 01
D a ys o f O p era tio n
Fric
tio
n C
oe
ff.
C yc le s
NO Device
Failure -
Dry Dev 1
Dry Dev. 2
Dry Dev. 3
15 ±5% P/Psat
95 ±3 % P/Psat
95 ±3 % P/Psat
Dry Dev 1
Dry Dev. 2
Dry Dev. 3
15 ±5% P/Psat
95 ±3 % P/Psat
95 ±3 % P/Psat
Device
Failure
In alcohol vapor
D. B. Asay, M. T. Dugger, and S. H. Kim, Tribol. Lett. 2008, 29, 67.
D. B. Asay, M. T. Dugger, J. A. Ohlhausen, and S. H. Kim, Langmuir 2008, 24, 155.
1~2 min
continuous operation for 2 weeks
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Micro-scale lubrication with a
molecular adsorbate film
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12
Increased Operating Life of Gear Train with Vapor Phase Lubrication
gear train on aging module
500 m
gear 1 (output gear)
gear 6
left/right
actuator
up/down
actuator
50 m gear 3
assembly
contacts:
dimples
hubs
teeth
1/2 DMS with uengine actuator
(90V square wave)
1000
10000
100000
Cumulative Percent Failed
Ac
cu
mu
late
d C
yc
les
to
Fa
ilu
re
10 20 9080705030
t50 = 46.6 Kcycles
sigma = 0.069
t50 = 31.0 Kcycles
sigma = 0.304100 Hz
500 Hz
FOTAS monolayer alone, t50 = 4.7x104
With VPL, device was stopped at 4.8x108
cycles without failure
• 1000 ppm pentanol, <100 ppm H2O
M. T. Dugger
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13
VPL is Effective on MEMS Devices with Thermal Actuators
VPL with pentanol produces extraordinary operating life in a variety of MEMS devices
single crystal silicon Fiber Switch
100 m100 m
5x106 cycles in air 5x106 cycles in 20% Psat pentanol
M. T. Dugger
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Understanding
accelerated wear of SiO2 by water
and wear prevention by alcohol
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Density Functional Theory (DFT) calculation of
Si-O-Si bond dissociation by rxn with gas molecule
Model System:
β-cristobalite (111)
Si-O-Si Rupture via Methanol
Red – O
Yellow – Si
White – H
Grey – C
CH3OH(gas)
Stable & low density
form of SiO2
Ea
Barnette, Asay, Kim, Guyer, Lim, Janik, and Kim, Langmuir 2009, 25, 13052–13061
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DFT calculation of activation energy for
different surface terminations
Transition State for Si-O-Si break
R1
R2
Si
RT
ErateRxn aexp
R1 R2 Ea (kJ/mol)
H H 114
CH3 H 151
H CH3 112
CH3 CH3 154
propyl propyl 224
Alcohol termination (OR) increases the activation barrier necessary to break Si-O-Si linkages…
Barnette, Asay, Kim, Guyer, Lim, Janik, and Kim, Langmuir 2009, 25, 13052–13061
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“Amorphous oxide of Si is boring; multicomponent silicate glasses
are more complicated & interesting”
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Water adsorption and penetration can cause ion-exchange with mobile/leachable ions and hydrolysis of Si-O-Si network
Si-O- Na+ + H2O
Si-OH + Na+ + OH-
Si-O-Si + OH- Si-OH + Si-O-
Si-O- + H2O Si-OH + OH-
Si-O-Si + H2O Si-OH + HO-Si
R.A.Schaut, C.G.Pantano. 2005
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Molecules possessing proton donor sites and lone-pair orbitals can enhance the crack growth rate by coupling across the Si-O bond to form an activated complex…
Charles & Hillig Theory
Influence of water vapor on crack propagation in soda lime glass
S. M. Wiederhorn J. Am. Ceram. Soc. 50, 407-414 (1967)
Stress-intensity factor, KI (MPam1/2) 0.4 0.8 0.7 0.6 0.5
RH
I
II
III
Freiman, Wiederhorn, & Mecholsky, J. Am. Ceram. Soc. 92, 1371 (2009)
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How does water adsorption affect scratch behaviors of glass?
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Scratching glass surface in humid conditions
Applied load
Friction force
Load: 0.2 N
Sliding speed:~4.2mm/s
Hertzian Pressure: ~200 MPa
Gas with controlled humidity
Carrier gas
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 100 200 300 400
Fric
tio
n C
oe
ffic
ien
t
Number of Passes
20% RH
40% RH
90% RH
-21000 m3 -32000 m3 -30000 m3 Total displaced volume
20% RH 40% RH 90% RH
Humidity dependence of wear of fused quartz surface rubbed with pyrex ball
Optical profilometry images of the substrate
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20% RH
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 100 200 300 400
Fric
tio
n C
oe
ffic
ien
t
Number of Passes
20% RH
40% RH
90% RH
-13000 m3 +25000 m3 -18500 m3
Humidity dependence of wear of soda lime glass surface rubbed with pyrex ball
40% RH 90% RH
Total displaced volume
Optical profilometry images of the substrate
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Optical profilometry image of pyrex ball rubbed in 20% RH Deposition of substrate wear debris
Optical profilometry image of pyrex ball rubbed in 90% RH Wear of ball
-200 -150 -100 -50 0 50 100 150 200
-12
-8
-4
0
4
Hig
ht
(m
)
Distance (m)
-200 -150 -100 -50 0 50 100 150 200
-12
-8
-4
0
4
Heig
ht
(m
)
Distance (m)
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-100 -50 0 50 100
-1.6
-1.2
-0.8
-0.4
0.0
0.4
0.8
20%RH
40%RH
90%RH
Sodium silicateFused quartz
90%RH
40%RH
He
igh
t (
m)
Position (m)
20%RH
-100 -50 0 50 100
-1.6
-1.2
-0.8
-0.4
0.0
0.4
0.8
Heig
ht
(m
)
Position (m)
-200 -150 -100 -50 0 50 100 150 200
-12
-8
-4
0
4
Hig
ht
(m
)
Distance (m)
-200 -150 -100 -50 0 50 100 150 200
-12
-8
-4
0
4
He
igh
t (
m)
Distance (m)
Pyrex ball rubbed against sodium silicate substrate
20% RH
90% RH
L. Bradley, Z. Dilworth,,, C. G. Pantano, & S. H. Kim “Hydronium Ions in Soda-lime Silicate Glass Surfaces” J. Am. Ceram. Soc. (DOI: 10.1111/jace.12136)
(Article first published online: 24 DEC 2012)
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In 20% RH
A small increase in humidity from dry air drastically
change the surface scratch behavior of glass
-100 0 100
20
10
0
-10
Distance (m)
In dry N2
-100 0 100
20
10
0
-10
Distance (m)
100 200 300 4000.0
0.5
1.0
20%RH
Frictio
n C
oe
ffic
ien
t
Sliding cyles
Dry N2
8.8m 4.3m
Pyrex ball
SLG substrate
Pyrex ball
SLG substrate
Hei
ght
(m
)
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-100 0 10010
0
-10
Distance (m)
100 200 300 4000.0
0.5
1.0
90%RH
40%RH
20%RH
Frictio
n C
oe
ffic
ien
t
Sliding cyles
As RH approaches saturation, the SLG surface becomes
“wear-resistant”…
-11.8m
-100 0 10010
0
-10
Distance (m)
SLG substrate
Pyrex ball Pyrex ball Pyrex ball
In 20% RH In 40% RH In 90% RH
-100 0 10010
0
-10
Distance (m)
4m
SLG substrate SLG substrate
4.3m
Hei
ght
(m
)
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0 100 200 300 400
-1.2
-0.8
-0.4
0.0
400 cycles
200 cycles
100 cycles
50 cycles 20 cycles
He
igh
t(m
)
Distance(um)
10 cycles
0 100 200 300 400
-1.2
-0.8
-0.4
0.0
400cycles
200cycles
100cycles50cycles
20cycles
He
igh
t (
m)
Distance (m)
10cycles
In 20% RH, the wear of the SLG substrate continues as the # of scratch cycles increases
In 90% RH, the damage to the SLG substrate is made initially by a few asperity contacts; but it does not grow.
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Water adsorption on glass surface matters…
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If the substrate is SiO2, it’s easy to measure water adsorption isotherm…
vent
IR
Humid gas
Silicon ATR Crystal
Penetration depth @ 3000 cm-1 = ~ 300 nm
detect adsorbed molecules only
heated
bubbler
1
carrier gas (Ar or dry clean air)
heated
bubbler
2
condenser
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Water adsorption on SiO2 in humid ambience
D. B. Asay and S. H. Kim, J. Phys. Chem. B 2005, 109, 16760
3230cm-1
solid-like (ice-like)
3400cm-1
liquid-like
ATR-IR measurement
0.5
1.0
3.0
2.0
2.5
1.5
Av
era
ge t
hic
kn
ess (
nm
)
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3800 3600 3400 3200 3000 2800 2600
3390
3360
PM
-RA
IRS
inte
nsity (
au) 2850
2918
Wavenumber (cm-1)
Dry
15%
35%
55%
75%
95%
0 20 40 60 80 1000
1
2
3
4
Water adsorbed
upon increase of humidity
Strongly bound water
not removable by Ar purging
Alcoholic hydroxyl
O
H /
CH
inte
nsity (
au)
Relative Humidity (%)
A. Tu, H. R. Kwak, A. L. Barnette, S. H. Kim, Langmuir 2012, 28, 15263–15269.
Water contact angle alone cannot tell you much about the structure of water on the solid surface.
Water adsorption on OH-SAM on Au; the “strongly bound” water on organic OH surface does not form ice-like structure
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380036003400320030002800 180016001400
1738
1412
1467
15761712
2848
2918
PM
-RA
IRS
In
ten
sity (
a.u
.)
Wavenumber (cm-1)
3430
Dry
5%
15%
45%
75%
95%
0 20 40 60 80 1000
1
2
3
4
5
6
7
O
H /
C
H in
ten
sity (
au
)
Relative Humidity (%)
Although COOH-SAM/Au also show a water contact angle is <5o, it behaves quite different from OH-SAM/Au and OH/SiO2.
A. Tu, H. R. Kwak, A. L. Barnette, S. H. Kim, Langmuir 2012, 28, 15263–15269.
Water contact angle alone cannot tell you much about the structure of water on the solid surface.
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Sum-Frequency-Generation (SFG) Vibration Spectroscopy
2800 2850 2900 2950 3000
SFG
sig
nal
(a.
u.)
Frequency, cm -1
2000~4000 cm-1
532nm w1
w2 w1+w2
SFG occurs at the interface or in the bulk
with no inversion symmetry (2)2 0
IRVISeffSFG III www2
)2(
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To generate SFG signals:
Random Inversion symmetry
No inversion symmetry in both molecular and optical length scales
Amorphous polymers Bulk water & vapor Glass
Piezoelectric crystals Crystalline biopolymers
Interfaces
Centrosymmetric crystals (such as NaCl)
Symmetrically arranged groups (such as CH2 in well-packed SAM or lipid bilayer)
χeff(2)
≠ 0
χeff(2)
= 0
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2800 2900 3000 3300 3600
Lo
g(1
/R)
Wavenumber cm-1
Propanol mole fraction
in the vapor mixture
of proanol & water
y=1.00
y=0.88
y=0.60
y=0.40
y=0.36
y=0.35
y=0.35
y=0.24
y=0.00
2800 2900 3000 3300 3600
SF
G inte
nsity (
au
)
Wavenumber cm-1
Propanol mole fraction
in the vapor mixture of
propanol & water
y=1.00
y=0.88
y=0.60
y=0.50
y=0.40
y=0.36
y=0.35
y=0.35
y=0.35
y=0.24
y=0.00
0.0 0.2 0.4 0.6 0.8 1.02.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Vapor
xWater,yWater
Pre
ssure
(kP
a)
xPropanol,yPropanol
Liquid
Azeotrope
1.0 0.8 0.6 0.4 0.2 0.0
Co-adsorption of water & alcohol on SiO2 A. L. Barnette and S. H. Kim, J. Phys. Chem. C 2012, 116, 9909-9916.
ATR-IR spectra SFG spectra
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A. L. Barnette and S. H. Kim J. Phys. Chem. C 2012, 116, 9909−9916
0.0 0.2 0.4 0.6 0.8 1.00.0
0.5
1.0
1.5
Th
ickn
ess o
f p
rop
an
ol (n
m)
Vapor mole fraction (y) of propanol
0
2
4
6
8
Thic
kness o
f wa
ter (n
m)
Co-adsorption of water & alcohol on SiO2
Silica surface
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3000 3200 3400 3600 3800
SF
G I
nte
nsity (
au
)
Wavenumber cm-1
Dry
40% RH
60% RH
80% RH
Saturation
Water adsorption on Glass as ftn of RH (glass cleaning = ethanol rinsed, and then soaked/aged in water for 3 hr)
3000 3200 3400 3600 3800
SF
G in
ten
sity (
au
)
Wavenumber cm-1
Dry
20% RH
40% RH
60% RH
80% RH
Satruation
Soda lime glass Fused quartz glass
3000 3200 3400 3600 3800
Air/water
Air/0.1MNaOH
0 20 40 60 80 100
Square
root of S
FG
inte
nsity (
a.u
)
Relative humidity (%)
FQ:3760cm-1
SL:3430cm-1
L. Bradley, Z. Dilworth,,, C. G. Pantano, & S. H. Kim “Hydronium Ions in Soda-lime Silicate Glass Surfaces”
J. Am. Ceram. Soc. (DOI: 10.1111/jace.12136) (Article first published online: 24 DEC 2012)
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Na+
Na+
Na+
Na+
Na+
Na+
Na+ Na+
Na+ Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+ leach
during aging in liquid water
Equili-brium with
adsorbed water layer
Na+
Na+
Na+
Na+
H3O+
H3O+
H3O+
H3O+
H3O+
H3O+
H3O+ H2O
H3O+
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H3O+
H3O+
In water or near-saturation humidity Pristine Na-silicate glass
H3O+
H3O+
H3O+
Na+
Na+
Na+
Na+
H+
H3O+
H+
H3O+
H3O+
H3O+
H3O+
In dry ambient
H3O+
H3O+
H3O+
H+
H+
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H+
The water molecules diffusing into the glass surface may find protons in the Na+-leached sites and form hydronium ions.
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Arun K. Varshneya et al. 2010
Na+ = 0.1nm K+ = 0.14nm H3O+ = 0.14nm
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2800 3000 3200 3400 3600 3800
SF
G in
ten
sity (
au
)
Wavenumber cm-1
high humidity
high humidity
Soda lime glass
Laura Bradley, Zach Dilworth, et al. J. Am. Ceram. Soc. (DOI: 10.1111/jace.12136)
Low humidity
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Si
O
Si
H H O
Si
O
Si
O H
H
Si
O
H H
Si
O
Hydrolysis & network corrosion
Michalske and Bunker. 1984.
L. C. Bradley et al. JACERS 2013
Solvation of H+ in the leached Na+ site forming H3O+
Water ingression into glass
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Formation of H3O+ formation in the Na+-leached site??
Searching for more supporting evidences..
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Dry N2
20%RH
40%RH
90%RH -100 0 100
-1.2
-0.8
-0.4
0.0
90%RH
40%RH
He
igh
t(m
)Distance(m)
20%RH
-100 0 100
-10
-5
0
He
igh
t (
m)
Distance (m)
-100 0 100
5
0
-5
-10
He
igh
t (
m)
Distance (m)
2.2 m
-100 0 100
5
0
-5
-101.6 m
He
igh
t (
m)
Distance (m)
-100 0 100
5
0
-5
-10
He
igh
t (
m)
Distance (m)
4.2 m
-100 0 100
5
0
-5
-10
He
igh
t (
m)
Distance (m)
7.3 m
The wear resistance at 90% RH is not observed for pyrex glass substrate rubbed with pyrex glass ball
Pyrex ball Pyrex glass 100 200 300 400
0.0
0.3
0.6
0.9
90%RH
40%RH
20%RH
Friction
Co
effic
ien
t
Sliding cyles
Dry N2
In dry N2
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The wear resistance at 90% RH is not observed for AF45 alkali-free borosilicate glass rubbed with pyrex glass ball
Dry N2 20%RH 40%RH 90%RH
-100 0 100
-15
-10
-5
0
He
igh
t (
m)
Distance (m)-100 0 100
-0.8
-0.4
0.0
90%RH
40%RH
He
igh
t(m
)
Distance(m)
20%RHIn dry N2
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How about chemically-strengthened glasses?
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Apple iPad glass
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
0.3 m
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
3.6 m
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
1.8 m
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
9.3 m
Dry N2
20%RH
40%RH
90%RH
-100 0 100-0.8
-0.4
0.0
Dry N2 90%RH
40%RH
He
igh
t(m
)Distance(m)
20%RH
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HTC cellphone glass
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
2.2 m
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
3 m
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
3.7 m
-100 0 1005
0
-5
-10
He
igh
t (
m)
Distance (m)
4.8 m
Dry N2
20%RH
40%RH
90%RH -100 0 100
-0.8
-0.4
0.0
90%RH
40%RH
He
igh
t(m
)Distance(m)
20%RH
-100 0 100
-6
-3
0
He
igh
t (
m)
Distance (m)
48
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The surface chemistry of counter-surface sliding against glass
matters…
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Not only vapor environment, but also counter surface of rubbing matter…
Diamond tip (curvature=200nm) When Pcontact < Hardness hillock (surface protrusion) When Pcontact > Hardness wear (material removal)
SiO2 ball (diameter=1000nm) Pcontact << Hardness
Substrate = Si wafer with native SiO2
J. Yu, S. H. Kim, B. Yu, L. Qian, and Z. , ACS Appl. Mater. Interfaces 2012, 4, 1585-1593.
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We expect a soft material would get
easily damaged when rubbed with
a hard material…
Hardness:
Ball Substrate
Al2O3 = 20GPa
Si3N4 = 14.5GPa
SiO2 = 6.0GPa
pyrex = 4.3GPa
Soda lime glass
= 5.9GPa vs.
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SiO2 ball Soda lime glass
-100 0 100-15
-10
-5
0
He
igh
t (
m)
Distance (m)
-100 0 10015
10
5
0
-5
He
igh
t (
m)
Distance (m)
12 m
Si3N4 ball Soda lime glass
-100 0 100-15
-10
-5
0
He
igh
t (
m)
Distance (m)
-100 0 10015
10
5
0
-5
He
igh
t (
m)
Distance (m)
10.4 m
-100 0 100
5
0
-5
-10
He
igh
t (
m)
Distance (m)
5.1 m
-100 0 100-15
-10
-5
0
He
igh
t (
m)
Distance (m)
Al2O3 ball
No surprise in dry N2 environment…
Soda lime glass
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In 90% RH, SiO2 ball wears and the scratch in soda lime glass is negligible.
SiO2 ball Soda lime glass
-100 0 100
5
0
-5
He
igh
t (
m)
Distance (m)
6.3 m
-100 0 100
5
0
-5
He
igh
t (
m)
Distance (m)
2 m
-100 0 100
-1.6
-1.2
-0.8
-0.4
0.0
90%RH
40%RH
He
igh
t(m
)Distance(m)
20%RH
-100 0 100-15
-10
-5
0
He
igh
t (
m)
Distance (m)
-100 0 10015
10
5
0
-5
He
igh
t (
m)
Distance (m)
12 m
-100 0 100
5
0
-5
-10
He
igh
t (
m)
Distance (m)
6.6 m
Dry N2
20%RH
40%RH
90%RH
100 200 300 4000.0
0.3
0.6
0.9 90%RH
40%RH
20%RH
Friction
Co
effic
ien
t
Sliding cyles
Dry N2
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In all humidity, the “hard” Si3N4 ball wears and the “soft” soda lime glass is almost intact.
Si3N4 ball Soda lime glass
-100 0 100
-0.4
0.0
0.4
90%RH
40%RH
He
igh
t(m
)Distance(m)
20%RH
-100 0 100
-10
-5
0
He
igh
t (
m)
Distance (m)
-100 0 10015
10
5
0
-5
He
igh
t (
m)
Distance (m)
10.4 m
-100 0 100
0
-5
1.8 m
He
igh
t (
m)
Distance (m)
-100 0 100
0
-5
He
igh
t (
m)
Distance (m)
1.6 m
-100 0 100
2
0
-2
-4
-6
He
igh
t (
m)
Distance (m)
1.5 m
Dry N2
20%RH
40%RH
90%RH
100 200 300 4000.0
0.3
0.6
0.9 90%RH
40%RH
20%RH
Friction
Co
effic
ien
t
Sliding cyles
Dry N2
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In intermediate humidity, Al2O3 ball wears and the scratch into soda lime glass by is very small.
-100 0 100
2
0
-2
-4
-6
He
igh
t (
m)
Distance (m)
0.2 m
-100 0 100
0
-5
He
igh
t (
m)
Distance (m)
1.1 m
-100 0 100
5
0
-5
-10
He
igh
t (
m)
Distance (m)
5.1 m
-100 0 100
0
-5
He
igh
t (
m)
Distance (m)
1.1 m
-100 0 100-6
-3
0
He
igh
t (
m)
Distance (m)
-100 0 100
-0.4
-0.2
0.0
90%RH
40%RH
He
igh
t(m
)Distance(m)
20%RH
Dry N2
20%RH
40%RH
90%RH
SL glass Al2O3 glass 100 200 300 400
0.0
0.3
0.6
0.9
90%RH
40%RH
20%RH
Frictio
n C
oe
ffic
ien
t
Sliding cyles
Dry N2
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Protecting glass from being scratched using “simple” alcohol adsorption
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57 -100 0 100
0
10
20
30
n-propanol vaporn-pentanol vapor
90%RH
He
igh
t (
m)
Distance (m)
Dry N2
1 10 1000.0
0.3
0.6
0.9
n-propanol vapor
n-pentanol vapor
90%RH
Frictio
na
l co
eff
icie
nt
Sliding cycles(N)
dry N2
Pyrex ball
Dry N2
SLG substrate
90% RH
n-pentanol
vapor
The wear of SLG / pyrex glass interface can be shut off by one monolayer-thic alcohol adsorption
n-propanol
vapor
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Mechanical property of surface region of glass ???
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Indentation load–displacement curve
pA
FH max
pA
SEr
2
dh
dFS
Reduced elastic modulus
Hardness
Nanoindentation test
Contact stiffness
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0
10
20
30
40
Ha
rdn
ess (
GP
a)
Indent depth(nm)
air side of glass
tin side
aged wiht water
annealed glass
140nm90nm40nm0
50
100
150
200
140nm90nm
Ela
stic m
odu
lus (
GP
a)
Indent depth(nm)
air side of glass
tin side
aged with water
annealed glass
40nm
Indentation depth dependence of elastic modulus and harness of Asahi soda-lime glass surface
Humidity = 40 – 60%
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J.A. Howell et al. J. Non-Cryst. Solids, 354 (2008) 1891–1899
Does the surface have better mechanical strength than the bulk?
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A. Bolshakov, G.M. Pharr, J. Mater. Res. 13 (1998) 1049. K. O. kese, Z. C. Li, & B. Bergman, Mater. Sci. Eng. A 204 (2005) 1.
0.0 0.5 1.0 1.5 2.0-150
-100
-50
0
50
He
igh
t(n
m)
Distance(um)
Or is it just a measurement artifact?
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Conclusions
• Water activity at glass surface – equilibrium with the gas phase water – Quite different from that at SiO2 surface – At high RH, H3O+ ions seem to be formed in the
interfacial region
• Scratch resistance under shear – Mechanochemical effects; not just mechanical. – Different from stress corrosion or crack propagation – Functions of vapor condition and counter-surface
chemistry
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Nano-indentation of Diamond-like carbon (DLC)
Hf (nm) Er (GPa) H (GPa)
120 59.3 0.5 5.6 0.1
90 58.6 0.6 5.6 0.1
50 43.2 1.1 4.6 0.2