This document summarizes a presentation on characterizing glassy materials using ultrasonic non-destructive techniques. It discusses the amorphous nature of glasses and their structure, including examples like silicate, borate, tellurite and phosphate glasses. It also describes preparing glass samples, analyzing their density and molar volume using various techniques, and measuring their ultrasonic properties to characterize the materials without damaging them.

1. Physical Characterization
of Glassy Materials Using
Ultrasonic Non-Destructive
Technique
Sidek Ab Aziz
Department of Physics, Faculty of Science
Universiti Putra Malaysia
43400 UPM Serdang, Selangor
Seminar on Materials Science and Technology 2013, June 24, 2013, ITMA

2. General Discussion
Glass
(amorphous)
Crystalline

3. Scope of Presentation
Free Web 2.0 Apps. http://mindmap.crazenut.org

4. What is a glass?
Glass - hard, brittle solid material that is normally lustrous and
transparent in appearance and shows great durability under
exposure to the natural elements.
Obsidian - super-
heated sand or rock
that rapidly cooled.
Moldavite formed by
meteorite impact (Besednice,
Bohemia)
4
obsidianites, kind of alumino-silicate
(SiO2–Al2O3) glasses containing
crystalline particles such as Fe2O3.).
Man-
Made
Glass

5. Principles of Glass
Formation
5
Glass (amorphous) Crystalline
The viscosity increases with undercooling until
the liquid freezes to a glass
Crystals
 ordered atomic
structures mean
smaller volumes (high
density) & lower
energies
 thermodynamically
stable phase
Glasses
 lack of long-range
order results in larger
volumes (lower
density), higher
energies;
 thermodynamically
metastable phase
Knowledge of glass
structure is important
which relates to other
Free Web 2.0 Apps. http://www.text2mindmap.com

6. Silicate Borate
• Glass structure has short range order but no long range
order.
• Silicate tetrahedra link up to form 3D glass network.
• Some ions such as Na will modify the network but are
not part of it.
Some structural groupings in borate glasses as indicated
from nuclear magnetic resonance experiments (Bray
1985).
Small solid circles represent boron atoms, open circles
oxygen atoms and an open circle with negative sign
indicates non-bridging oxygen.
Glass Structure

7. Bonding Structure of Tellurite
2D chain:
crystalline TeO2
TeO2 chains Deformation and
breaking of TeO2
chain by modifier
The structure
basic TeO2 –based glass structural unit namely, TeO4 trigonal
bipyramids (tbp) and TeO3 trigonal pyramid (tp) .
TeO4 tbp TeO3 tp
Both structure have a lone pair of electron in one of its
equatorial /axial sites.
7
Phosphate
Basic glass former,
P2O5
Effects of Mg
cation content on
the phosphate
glass

8. Glass Sample Preparation
www.glassforever.co.uk/howisglassmade/
glass furnace cooling
systems
8

9. 9
Some pigments used to produce coloured glass
Compounds Colors Compounds Colors
iron oxides greens, browns selenium compounds reds
manganese oxides deep amber, amethyst,
decolorizer
carbon oxides amber/brown
cobalt oxide deep blue mix of mangnese, cobalt,
iron
black
gold chloride ruby red antimony oxides white
uranium oxides yellow green (glows!) sulfur compounds amber/brown
copper compounds light blue, red tin compounds white
lead with antimony yellow

10. Research Project
To produce the fiber optics and flat glasses for the
future applications
Glass Research @ UPM
 Fiber Optics are cables that are made of optical fibers that can
transmit large amounts of information at the speed of light.
(www.dictionary.com)
 Dominated by Silicate based glass

11. Glass
Research
@ UPM
Key
Researchers
A goal of solid-state science, which intends to give universal understandings of
macroscopic properties through simple theories on the basis of known atomic
structures.
11

12. Glass Research @ UPM
12
Tellurite
(TeO2)
Phosphate
(P2O5)
Borate
(B2O3)
Lithium
Chloroborate
Lead Borate
Lead Bismuth
Borate
Bismuth Borate
Zink Chloride Phosphate
Silver Phosphate
Lithium Phosphate
Lithium Chlorophosphate
Lead Magnesium
Chlorophosphate
Lead Bismuth Phosphate
Lithium Chloride Phosphate
Lithium Zink Phosphate
Lead Zink Metaphosphate
Zinc magnesium phosphate
Zinc Tellurite
Borotellurite
Zinc oxyfluorotellurite
Lead Borotellurite
Silver Borotellurite
Zinc Neodymium
Tellurite
Zinc borotellurite
Zinc oxyfluorotellurite
Ferum Tellurite
Glass research activities conducted at the Universiti Putra Malaysia.
Formation
Physical Studies
Elastic Properties
Optical
Characterization
Thermal Properties
Dielectric Properties
Research
Scope

13. Glass Research @ UPM
13
Tellurite
(TeO2)Phosphate
(P2O5)
Borate
(B2O3)
Selected some of the prepared binary and ternary glass samples at the Department
of Physics, Universiti Putra Malaysia.
Ag2O-B2O3
PbO-B2O3
Bi2O3-B2O3
Li2O-P2O5
PbO-B2O3
PbCl2-P2O5
LiCl-P2O5
ZnCl2-P2O5
B2O3-TeO2
ZnO-TeO2
Fe2O3-TeO2
PbO-Bi2O3-B2O3
LiCl-Li2O-P2O5
PbCl2-MgO-
P2O5
Li2O-ZnO-P2O5
PbO-ZnO-P2O5
PbO-Bi2O3-P2O5
Cu2O-CaO-P2O5
Ag2O-B2O3-TeO2
PbO- B2O3-TeO2
ZnO- B2O3-TeO2
Nb2O5- ZnO- TeO2
AlF-ZnO-TeO2
binary
ternary

14. Glass Oxide Former Modifier Glass Samples Researchers
Binary Oxide Glass Series
Borate (B) Silver (Ag) Ag2O-B2O3 Sidek et al. (1994)
Lead (Pb) PbO-B2O3 Azman et al. (2002)
Bismuth (Bi) Bi2O3-B2O3 Sidek et al.(2007)
Phosphate (P) Lithium (Li) Li2O-P2O5 Low et al. (1999)
Sidek et al.(2003)
Lead (Pb) PbO-B2O3 Azman et al. (2002)
Talib et al. (2003)
Lead Chloride (PbCl2) PbCl2-P2O5 Talib et al. (2003)
Lithium Chloride (LiCl) LiCl-P2O5 Loh et al. (2005)
Tellurite (Te) Boron (B) B2O3-TeO2 Halimah et al.(2005)
Sidek et al.(2006)
Zink (Zn) ZnO-TeO2 Rosmawati et al. (2008)
Sidek et al.(2009)
Ferrum (Fe) Fe2O3-TeO2 Zarifah et al. (2010)
PbO-P2O5
B2O3-TeO2
Ag2O-B2O3
Glass samples prepared by melt
quenching technique @ UPM

15. Glass Former Network Modifier Glass Samples Researchers
Ternary Oxide Glass Series
Borate (B) Bismuth (Bi) Lead (Pb) PbO-Bi2O3-B2O3 Sidek et al. (2005)
Hamezan et
al.(2006)
Phosphate (P) Lithium (Li) Lithium Chloride
(LiCl)
LiCl-Li2O-P2O5 Low et al. (1999)
Sidek et al.(2003)
Magnesium (Mg) Lead Chloride
(PbCl2)
PbCl2-MgO-P2O5 Sidek et al.(2004)
Zink (Zn) Lithium (Pb) Li2O-ZnO-P2O5 Sidek et al.(2005)
Zink (Zn) Lead (Pb) PbO-ZnO-P2O5 Sidek et al.(2005)
Bismuth (Bi) Lead (Pb) PbO-Bi2O3-P2O5 Sidek et al.(2006)
Calsium (Ca) Copper (Cu) Cu2O-CaO-P2O5 Talib et al. (2008)
Tellurite (Te) Boron (B) Silver (Ag) Ag2O-B2O3-TeO2 Halimah et al.
(2005)
Zink (Zn) Aluminum Floride
(AlF)
AlF-ZnO-TeO2 Sidek et al.(2009)
Boron (B) Lead (Pb) PbO- B2O3-TeO2 Iskandar et al.
(2010)
Zink (Zn) Neodymium (Nb) Nb2O5- ZnO- TeO2 Mohamed et al.
(2010)
Boron (B) Zink (Zn) ZnO- B2O3-TeO2 Ayuni et al (2011)
Selected some of the prepared ternary glass samples at the Department of Physics, Universiti Putra
Malaysia.
GeO2-PbO-Bi2O3
AgI-B2O3-TeO2
PbO-B2O3

16. SEM Photos XRD Pattern of Starting
Materials
TeO2 powder
TeO2 glass
ZnO Powder
TeO2-ZnO glass
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
10 20 30 40 50
2 theta
Intensity(a.u)
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
10 20 30 40 50
2 Theta
Intensity(a.u)
0
5000
10000
15000
20000
25000
30000
35000
10 20 30 40 50
2 Theta
Intensity(a.u)
TeO2-ZnO-AlF3
glass
AlF3 (97.0%)
Powder 16

17. XRD patterns
100
600
1100
1600
2100
10 20 30 40 50
2 theta
Intensity(a.u)
TZ7
TZ6
TZ5
TZ4
TZ3
TZ2
TZ1
TZ0
• no discrete or continuous sharp peaks
• but broad halo at around 2 260 - 300, which reflects the characteristic of
amorphous materials.
• absence of long range atomic arrangement and the periodicity of the 3D network
in the quenched material
400
600
800
1000
1200
1400
1600
1800
10 20 30 40 50
2 theta
Intensity(a.u)
S5
S4
S3
S2
S1
TeO2)1-x (ZnO)x (x = 0.1 to 0.4 in 0.05) (TeO2)90(AlF3)10-x(ZnO)x (x = 1 to 9)
binary ternary
17

18. Ultrasonic System
Schematic representation of (a)
simple pulse ultrasonic system. (b)
Envelope of pulse echo train and (c)
detail of each echo as seen on
oscilloscope display
18

19. Ultrasonic Pulse Echo Overlap System
Pulse echo overlap system
Pulse echo overlap waveforms
Block diagram of the experimental
set up – ultrasonic wave velocity
and attenuation measurement
(Mepco Engineering College,
INDIA)
19

20. Ultrasonic System
Ultrasonic – MBS
8000 Ultrasonic Data
Acq. System
20

21. 21
Important Physical Properties
Density is defined as the mass per unit
volume.
– Density is an intensive property of
matter, meaning it remains the
same regardless of sample size.
– It is considered a characteristic
property of a substance and can be
used for material’s classification
Density Measurement
(Archimedes Method)
ac
aca
a
s
ww
w  







Molar volumes

M
V 

22. Physical Properties
Variation of density and molar volume with mol% Bi2 O3
in Bi2 O3–B2 O3 glass systems.
The increase of the density of the glasses
accompanying the addition of Bi2 O3 is probably
attributable to a change in cross-link density and
coordination numbers of Bi3+ ions.
26
26.5
27
27.5
28
28.5
29
0.55 0.6 0.65 0.7 0.75 0.8 0.85
Mole fraction of TeO2
Molarvolume(cm3
mol-1
)
4650
4700
4750
4800
4850
4900
4950
5000
Density(kgm-3
)
Density and molar volume of TeO2.B2O3 glasses
28
28.5
29
29.5
30
30.5
0.05 0.10 0.15 0.20 0.25 0.30 0.35
Pecahan Mol Ag2O
Isipadumolar(cm3
)
4800
4900
5000
5100
5200
5300
Ketumpatan(kg/m3
)
Density and molar volume of [(TeO2)x (B2O3)1-x)]1-y [Ag2O]y
22

23. Density and Molar Volume
3500
4500
5500
6500
7500
0 20 40 60 80
Bismuth Oxide (mol%)
Density(kgm-3)
Dependence of density on the composition of bismuth oxide
glass systems as measured by El-Adawy and Moustafa (1999)
(5 - 45 mol%), Wright et al (1977) (20 – 42.5 mol%) and
present works (40 – 70 mol%).
23

24. Density & Molar Volume
4700
4800
4900
5000
5100
5200
5300
5400
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Mole fraction of ZnO
Density(kg/m
3
)
22
24
26
28
30
32
34
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Mole fraction of ZnO
Molarvolume(10
-6
m
3
mol
-1
)
•Similar behaviour as El-
Mallawany (1993).
•Addition of ZnO causes some
type of structural
rearrangement of the atoms
(Hoppe et al. (2004).
•Possibility for the alteration of
the geometrical configuration
upon substitution of ZnO into
the tellurite glassy network.
24

25. Density & Molar Volume
4700
4800
4900
5000
5100
5200
5300
5400
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Mole fraction of ZnO
Density(kg/m
3
)
22
24
26
28
30
32
34
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Mole fraction of ZnO
Molarvolume(10
-6
m
3
mol
-1
)
•The increase in density indicates zinc ions enter
the glassy network
•The decreases in the molar volume was due to the
decrease in the bond length or inter-atomic spacing
between the atoms
• The stretching force constant (216 N/m – 217.5
N/m) of the bonds increase resulting in a more
compact and dense glass.
• Atomic Radius (Shelby, 2005).
•R(Zn2+)(0.074 nm) << R(Te2+)(0.097 nm)
•there is no anomalous structural change (non-linear
behaviour)
25

26. Elastic constants of the glasses
Longitudinal modulus
Shear modulus
Bulk modulus
Poisson’s ratio
Young’s modulus
Debye Temperature
2
lVL 
2
sVG 







22
3
4
sl VVK 
 
 22
22
2
2
sl
sl
VV
VV



 
22
222
43
sl
sls
VV
VVV
E




mDt V
M
Np
k
h 3
1
4
9










3
1
33
12










lS
m
VV
V
26

27. 27
[(TeO2)65(B2O3)35]1–y[Ag2O]y glasses
(Halimah et al. 2010)
Pure and WO3 dopedCeO2–PbO–B2O3 glasses
(Singh & Singh 2011)
Figure 17 Density and molar volume of selected glass samples.
Table 6 Measured density (ρ), molar volume (V), longitudinal ultrasonic velocity (vl), shear
ultrasonic velocity (vs), elastic moduli, Poisson's ratio (σ), and fractal dimension (d = 4G/K )
and (E/G) ratio of (TeO2)90(AlF3)10-x(ZnO)x glasses (Sidek et al. 2009).
Elastic modulus of zinc oxyfluorotellurite glasses

28. Ultrasonic Wave Velocity
Compositional dependence of the velocity of
longitudinal and shear acoustic waves in Bi2
O3–B2 O3 glass systems.
Both increase at first with increasing Bi2 O3
mol% up to a maximum at 25 mol% Bi2 O3
and then decrease as the Bi2 O3 mol%
increases further.
1000
1500
2000
2500
3000
3500
4000
0.05 0.10 0.15 0.20 0.25 0.30 0.35
Pecahan mol of Ag2O
Halajuultrasonik(m/s)
Compositional dependence of the velocity of longitudinal and
shear acoustic waves in [(TeO2)x (B2O3)1-x)]1-y [Ag2O]y glass
1500
2000
2500
3000
3500
4000
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Mole fraction of ZnO
Velocity(m/s) Longitudinal
Longitudinal
Shear
Shear
Compositional dependence of the
velocity of longitudinal and shear
acoustic waves in [(ZnO)(TeO2) glass
28

29. Ultrasonic Wave Velocity
Lead Magnesium Chloride
Phosphate Glass
29

30. Elastic Modulus
Dependence of longitudinal modulus on
the composition of Bi2 O3–B2 O3 glass
systems.
One reason for this difference may come from the
volume effect, in that C44 expresses the resistance
of the body to deformation where no change in
volume is involved, while C11 expresses the
resistance where compressions and expansions
are involved.
10
20
30
40
50
60
70
0.05 0.10 0.15 0.20 0.25 0.30 0.35
Pecahan mol Ag2O
Moduluskenyal(GPa)
L
E
K
G
Compositional dependence of the longitudinal and shear modulus of
[(TeO2)x (B2O3)1-x)]1-y [Ag2O]y glass
30

31. Elastic Moduli
15
20
25
30
35
40
45
50
55
60
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4
Mole fractionofZnO
ElasticModuli(GPa)
Longitudinal Modulus, L
Young’s Modulus, E
Bulk Modulus, K
Shear Modulus, G
31

32. Elastic Properties
Mole fraction, x 0.3 0.4 0.45 0.5 0.6
Elastic stiffness (GPa)
C11
C44
C12
48.9
18.0
12.9
48.8
18.0
12.7
47.5
17.4
12.7
47.3
17.5
12.3
47.3
17.2
13.0
Young's modulus, E
(GPa)
43.5 43.5 42.2 42.2 41.8
Bulk modulus, B (GPa) 24.9 24.7 24.3 24.0 24.4
Poisson's ratio,  0.208 0.207 0.211 0.207 0.215
Fractal dimension 2.90 2.92 2.87 2.92 2.82
Molar volume, V
(cm3/mole)
34.2 33.8 34.2 33.9 33.3
Number of atoms per
volume (x1028
atoms/m3)
9.67 8.90 8.37 8.00 7.24
Debye Temperature (K) 291 275 263 255 238
The room temperature elastic properties
of (PbO)x(P2O5)1-x glasses
Mole fraction, y 0.04 0.06 0.07 0.1
Elastic stiffness (GPa)
longitudinal, c11
shear, c44
c12
50.4
17.1
16.3
44.3
16.0
12.3
43.0
15.9
11.2
35.7
14.8
6.03
Young's modulus, E
(GPa)
42.4 39.0 38.4 33.9
Bulk modulus, B (GPa) 27.6 23.0 21.8 15.9
Poisson's ratio,  0.244 0.217 0.206 0.145
Fractal dimension 2.47 2.79 2.92 3.73
Molar volume, V
(cm3/mole)
33.5 33.5 33.3 33.4
Number of atoms per
volume (x1028
atoms/m3)
9.60 9.65 9.72 9.78
Debye Temperature (K) 276 266 264 251
Room temperature elastic properties of
(PbCl2)y(PbO.2P2O5)1-y glasses
32

33. Elastic Properties
33

34. 34
Elastic properties of ZnO-TeO2 glasses (Sidek et al. 2010)
1500
2000
2500
3000
3500
4000
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Mole fraction of ZnO
Velocity(m/s)
15
20
25
30
35
40
45
50
55
60
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Mole fraction of ZnO
ElasticModuli(GPa)
0.19
0.2
0.21
0.22
0.23
0.24
0.25
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Mole fraction of ZnO
Poisson'sRatio
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Mole fraction of ZnO
Microhardness(GPa)
Shear
Longitudinal
L
E
K
G
Ultrasonic velocities
Elastic moduli
Poisson’s ratio
Micro-hardness

35. 35
Elastic moduli of selected binary glassy materials.
Elastic Moduli (GPa)

Material Density L G K E References
15Sm2O3-85P2O5 3.280 66.42 23.63 34.91 57.84 0.224 Sidek et al. (1988)
15La2O3-85P2O5 3.413 67.63 23.05 36.90 57.23 0.241 Sidek et al. (1988)
15Nd2O3-85P2O5 3.233 70.50 24.80 37.40 60.90 0.229 Senin et al. (1993)
15Bi2O3-85P2O5 4.418 56.8 19.2 31.2 47.9 0.244 Sidek et al. (2011)
20Ho2O3-80P2O5 3.327 73.1 24.7 40.1 Senin et al. (1996)
20Nd2O3-80P2O5 3.358 67.4 24.1 35.3 58.8 0.22 Sidek et al. (1993)
20Sm2O3-80P2O5 3.326 63.1 23.4 31.9 56.5 0.20 Sidek et al. (1993)
20Ce2O3-80P2O5 3.254 74.4 25.0 41.1 62.3 0.23 Sidek et al. (1993)
14Ag2O-86B2O3 2.850 44.15 13.37 26.32 Saunders et al. (1987)
20PbO-80B2O3 3.801 45.4 14.70 25.90 43.0 0.262 Azman et al. (2002)
40PbO-B2O3 4.852 76.09 25.15 42.54 63.04 0.253 Sidek et al. (2003)
40Bi2O3-B2O3 5.262 74.67 27.70 37.75 66.75 0.205 Sidek et al. (2003)
30PbO-70B2O3 4.019 71.40 22.80 41.00 57.60 0.265 Azman et al. (2002)
30PbO-70P2O5 4.135 47.30 15.70 24.00 39.20 0.252 Azman et al. (2002)
26Tb2O3-74P2O5 3.578 76.2 25.4 42.00 64.0 0.246 Senin et al. (1994)
26Ce2O3-74P2O5 3.234 72.5 24.00 40.60 60.00 0.233 Saunders et al. (2001)
26Pr2O3-74P2O5 3.338 74.3 24.3 41.9 61.1 0.257 Senin et al. (2000)
33Ag2O-67B2O3 4.030 72.18 19.17 46.61 Saunders et al. (1987)
30ZnO-70TeO2 5.211 56.06 19.39 30.21 47.92 0.236 Rosmawati et al. (2008)

36. 36
Elastic moduli of selected binary glassy materials (cont)
33ZnCl2-67TeO2 4.63 50.8 15.10 30.6 39.0 0.289 El-Mallawany et al.
(1998)
30V2O5-70TeO2 4.564 44.1 11.5 28.8 30.5 0.289 El-Mallawany et al.
(1998)
30B2O3-70TeO2 4.89 63.62 23.33 32.51 56.48 0.21 Halimah et al. (2007)
30B2O3-70TeO2 4.78 0.21 Sidek et al.(2006)
TeO2 (pure glass) 5.101 56.40 19.90 Sidek et al. (1989)
TeO2 (pure glass) 5.105 59.1 20.6 31.7 50.7 0.233 El-Mallawany et al.
(1998)
TeO2 (pure crystal) 6.02 56.0 27.2 Arlt & Schweppe (1968)
P2O5 (pure glass) 2.52 12.1 Bridge et al. (1984)
SiO2 (pure glass) 2.203 30.7 Borgadus et al. (1965)
So far silicate based glasses are
practically well employed by
engineers for optoelectronic
devices development and
application.
However silicate glass has some
disadvantages. As an alternative, more
researchers are now preferred tellurite
based glass to be used as a host matrix in
laser applications.
We also found that tellurite is the best
glass host due to low melting temperature
and in absence of hygroscopic properties
as compared to borate and phosphate
based glasses.

37. Potential Application
of Glassy Materials
CD memory device
Optical switching device
Non-linear optical
devices
Electrochemical devices
Laser host
Infra-Red Fiber Optics
37

38. 38

39. Next-generation
large-scale panels
Glass substrates for LCDs
Next-generation large-scale panels by
contributing to form various functional films on
glass substrates.
39

40. …you could see what
was in the fridge
without opening it?
…you could have a
fish tank which is self
cleaning?
Self cleaning glass
40
When water hits
a hydrophilic
surface, it
flattens and
spreads out to
form a thin sheet.
Hydrophilic
surface
=wetting
Water spreads
HYDROPHOBIC
(WATER HATING)
When water hits a
hydrophobic
surface, it beads.
Hydrophobic
surface
= beading
Water
beads
HYDROPHILIC
(WATER LOVING)
Poor wetting
(beading)
Contact
angle > 90°
Good wetting
Contact angle < 90°

41. When water hits a
hydrophilic surface, it
flattens and spreads
out to form a thin
sheet.
Hydrophilic surface
=wetting
Water spreads
HYDROPHOBIC
(WATER HATING)
When water hits a
hydrophobic
surface, it beads.
Hydrophobic
surface
= beading
Water
beads
HYDROPHILIC
(WATER LOVING)
Poor wetting
(beading)
Contact
angle > 90°
Good wetting
Contact angle < 90°
41

42. SELF CLEANING GLASS
THE LOTUS LEAF EFFECT
The leaves of Lotus plants have
the unique ability to avoid
getting dirty.
They are coated with wax
crystals around 1 nanometre in
diameter and have a special
rough surface.
Droplets falling onto the leaves
form beads and roll off taking
dirt with them, meaning the
leaves are self-cleaning.
Sometimes referred to as
“The Lotus Leaf effect”
Scientists have mimicked nature
at the nanoscale to create glass
surfaces that are ‘self-cleaning’
like the Lotus leaf.
No more scrubbing of shower
screens!
Self cleaning glass Normal glass
No more Spiderman
window cleaner!
42

43. SELF CLEANING GLASS
HOW DOES IT WORK?
Glass is coated with a layer of
nanocrystalline titanium dioxide
(TiO2).
The titanium dioxide reacts to the
ultraviolet (UV) component of sunlight
causing a gradual break down and
loosening of dirt.
This is known as the
‘photocatalytic’ stage
The reaction also causes the glass surface
to become super hydrophilic. This forces
water to spread across the surface like a
sheet, rather than beading, thereby
washing away the loosened
debris on the surface of
The glass as it falls.
This is the ‘hydrophilic’
stage.

44. APPLYING A MONOLAYER TO GLASS
GLASS NANO COATINGS
OptiView Anti-reflective glass made by
Australian company Pilkington.
Switchable glass changes from transparent to opaque.
A nano-layer of a rod-like particle suspension is placed between two
layers of glass.
Under normal conditions, the suspended particles are arranged in
random orientations and tend to absorb light, so that the glass
panel looks frosted or opaque.
But when a voltage is applied, the suspended particles align and let
light pass, turning the glass clear.
SWITCHABLE GLASS

46. CONCLUSION
Glass is one of the most versatile and most
fascinating materials
Their uniqueness in physical, optical, thermal,
mechanical and chemical properties offer an
almost unlimited range of applications.
Ultrasonic system has been employed to
characterize their elastic properties.
Extensive series of investigation using borate,
phosphate and tellurite based glasses have
been carried out to study the effect of certain
oxides into those glass formers in terms of
physical properties such as density, molar
volumes and elasticity.