Glass

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Glass
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Module Outcomes

• What is glass?
• Definitions of hydrophilic, hydrophobic, wetting,
  beading
• The Lotus Leaf effect
• How does self cleaning glass work?
• Applications of nanotechnology.

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What If?

• you could have a fish tank which is self
  cleaning?

Image Danny de Bruyne _at_ Stock.xchng
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What If?

• you could see what was in the fridge without
  opening it?

Image Courtesy of Nanotechnology Victoria Pty
Ltd
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The Bizarre Properties of Glass

• Is it a solid or a liquid?

Despite the solid appearance, glass is actually
in a jammed state of matter. It is somewhere
between liquid and solid It has random
un-oriented molecules as opposed to a crystal
solid with arranged fixed molecules It moves
very slowly and never quite becomes a proper
solid.
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Activity 1

• Glass Basics

• List 5 properties of glass
• How is it produced?
• What makes it such a useful material?

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Experiment 1 Magic Sand

• What do hydrophobic and hydrophilic mean?

Image Courtesy Bridge8/Flinders University
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Hydrophilic Water Loving
When water hits a hydrophilic surface, it
flattens and spreads out to form a thin sheet.
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Hydrophobic Water Hating
When water hits a hydrophobic surface, it beads.
Image Viktors Kozers _at_ Stock.xchng
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Wetting Beading
Good wetting Contact angle lt 90
Contact angles below 90 indicate good wetting,
while contact angles above 90 indicate poor
wetting (beading).
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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
Images top to bottom T. Filewich _at_ Stock.xchng,
Daniel Clarke _at_ Stock.xchng
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Self Cleaning Glass
Scientists have mimicked nature at the nanoscale
to create glass surfaces that are self-cleaning
like the Lotus leaf.
Self cleaning glass
Normal glass
No more scrubbing of shower screens!
No more Spiderman window cleaner!
Images L to R Francois Schnell _at_ Flickr, Diamond
ShellTM
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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.
Self cleaning glass
Normal glass
Image PGG Industries
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Self Cleaning Glass
How does it work?
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
looseneddebris on the surface of the glass as
it falls. This is the hydrophilic stage.
Self cleaning glass
Normal glass
Watch Video-http//kitson.co.uk/WhatsNew.html
Image PGG Industries
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So Can a Fish Tank Be Self-Cleaning?
Australian company Diamond Shell has made self
cleaning aquarium glass called Barracouta Glass
based on the photocatalytic and hydrophilic
process.
Self cleaning glass
Normal glass
Watch animation - http//www.nanovic.com.au/flash/
barracouta.swf
Image Danny de Bruyne _at_ Stock.xchng
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Self Cleaning Glass
How does it work?
Another type of self cleaning glass uses
hydrophobicity, not hydrophilicity. This type of
glass is given a coating which makes it super
hydrophobic, meaning water forms beads and runs
of the glass. This type of glass is indoors, such
as in shower screen, where there is no sunlight
enable use of the other type of glass.
Self cleaning glass
Normal glass
Watch video-http//www.kitson.co.uk/WhatsNew.html
Image Saint-Gobain Glas
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Experiment 2
Applying a Monolayer to Glass

• Glass Nano Coatings

Besides titanium dioxide in self-cleaning glass,
other nano-coatings can be used to change the
properties of glass and give it a specific
application.
Lets learn about how glass coatings changes
surface properties.
Image University of Wisconsin
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Glass Nano-Coatings
Anti-reflective Glass
Type 1 Glass, is coated with multiple layers of
metal oxides such as TiO2 which have a high
refractive index, meaning light passes through
them very quickly. The thickness of the layers is
related to the wavelength of light, resulting in
destructive interference of light reflected off
the surfaces, making the glass non-reflective. Ty
pe 2 Another method of producing anti-reflective
glass is to coat it with a single layer of
nanoporous SiO2. The refractive index of the
porous coating is between that of the glass
surface and air, thereby reducing the
reflectivity and increasing the transmission of
light at the glass surface.
Self cleaning glass
Normal glass
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Anti-reflective Glass
OptiView Anti-reflective glass made by Australian
company Pilkington.
Self cleaning glass
Normal glass
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Other Nano Applications
Switchable Glass
Switchable glass changes from transparent to
opaque.An nano-layer of a rod-like particle
suspension is placed between two layers of
glass.Under normal conditions, thesuspended
particles are arranged in random orientations
and tend to absorb light, so that the
glasspanel looks frosted or opaque. But when a
voltage is applied, the suspended particles
align and let light pass, turning the glass
clear.
Self cleaning glass
Normal glass
Image Beijing All Brilliant Technology Co., Ltd
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Other Nano Applications
Switchable Glass
Switchable glass was used in the Big Brother
house to control the view into the rewards room.
Self cleaning glass
Normal glass
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Switchable Glass
Switchable glass has applications in car sun
roofs, office buildings, and residential
apartments.
Skydeck 88 in the Eureka Tower in Melbourne is
the only observation deck in the world that can
thrill you with 'The Edge' - a glass cube made of
switchable glass, which projects 3 metres out
from the building and suspended almost 300 metres
above the ground, with you in it!
Self cleaning glass
Normal glass
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Other Nano Applications
Aerogels
Aerogels have exceptional thermal insulation, are
light weight, and translucent. These properties
result from the nanoporous structure of the
aerogel.  The material is 99 air and only 1
solid. In glazing, aerogels have been laminated
between two panes of glass for applications where
high thermal insulation is required, while still
allowing light diffusion.
Self cleaning glass
Normal glass
Image John Barrie _at_ flickr
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Activity 2

• Research other nano applications in glass.

• Conductive glass
• Solar heat control
• Any others?

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The Future

• Nanotechnology provides new materials that could
  potentially have profound affects on building
  design.
• For instance, glass can be used more liberally if
  it is optically tuned to block heat and UV.
• It would be possible to construct a building with
  many more, larger windows than is currently
  viable, since heat can be kept out and UV
  photo-damaged prevented.

Image University of Technology, Sydney
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Revision

• List some properties of glass
• Define hydrophilic, hydrophobic, wetting and
  beading
• Describe the Lotus Leaf effect
• How does self cleaning glass work?
• List 5 examples of glass with enhanced properties.

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