Transcript Slide 1

Armourers and
Brasiers Company
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
The future is materials
Prepared by Dr Diane Aston, IOM3
The aim of this module is to introduce you to
materials which have come to the fore in
more recent years. These are the materials
that will be helping to shape our future.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
Armourers and
Brasiers Company
Prepared by Dr Diane Aston, IOM3
The session aims to introduce you to the interesting
collection of materials called Smart Materials.
At the end of this session you should be able to:
• Give a broad definition of smart materials and cite an example
of a type of smart material;
• Describe three types of colour changing polymer
• Describe three useful properties of shape memory alloys
• Give an example of where piezoelectric ceramics are used
• Give an example of where quantum tunnelling composite is
used
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• Everything around us is made from something and
all of the materials we rely on come from natural
resources found within the Earth’s crust.
• Materials are used everywhere and they are chosen
for particular applications because of their specific
useful properties.
• We split materials up into four main classes :
metals, ceramics, polymers and composites.
• Within these groups we can describe materials as
structural or functional.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
Structural materials
Functional materials
• Been using these materials for
thousands of years.
• Started to make an impact on
our technology in the last 50
years or so.
• Chosen for their structural or
mechanical properties:
– Strength
– Toughness
– Hardness
– Stiffness
• Used in the construction of
everything around us.
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• Chosen for their functional
properties:
– Optical properties
– Electrical properties
– Thermal properties
– Magnetic properties
– Smart behaviour
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• A special group of metallic, polymeric, ceramic and
composite materials that exhibit unusual
behaviour.
• They experience a change in one specific property
with a change in a specific aspect of their
surroundings.
• Some change colour, opacity, size/shape, electrical
conductivity, viscosity, stiffness.
• Some change with a change in temperature, UV
light level, presence of an electrical or magnetic
field, strain rate, shear rate, applied pressure.
Prepared by Dr Diane Aston, IOM3
Armourers and
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• Change is not controlled by external circuits or
microchips.
• Change is inherent to the material.
• Change occurs because the structure of the
material is changing.
• Atoms or molecules moving their position very
slightly produce a change which is easy to see,
measure or detect.
Prepared by Dr Diane Aston, IOM3
Armourers and
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• The shape memory effect was first observed in a goldcadmium alloy in 1932.
• In the 1960’s Nitinol was developed and despite there being
other SMAs available it is still by far the most commonly used
as it is by far the most versatile SMA.
• The memory temperature can be controlled by controlling
the composition of the alloy and by changing how it is
processed it can be designed to show one of three useful
properties.
• Entirely by coincidence, Nitinol is biocompatible so it can
safely be used alongside and inside the human body.
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• Very flexible materials, can
be bent without suffering
permanent deformation.
• Used in flexible spectacle
frames, mobile phone aerials
and under-wired bras.
• Useful in surgical tools
which need to be kinkresistant.
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Brasiers Company
• Remembers a memory shape
above the memory
temperature .
• Can be bent to shape during
use and then reset by
heating.
• Trained by heating and then
quenching.
• Can go through thousands of
cycles.
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Brasiers Company
• The material ‘remembers’
different structures above
and below the memory
temperature.
• As it is heated or cooled it
changes from one structure
to the other.
• Change in structure
generates a force, so can be
used as a switch in a
temperature controlled
circuit.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• A number of different types of smart polymers
which exhibit useful behaviour
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Thermochromic materials
Photochromic polymers
Electrochromic polymers
Shape memory polymers
Strain and shear rate sensitive polymers
Prepared by Dr Diane Aston, IOM3
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• Appear to change colour at a
given temperature.
• Based on polymers called
leucodyes or liquid crystals.
• Change occurs because
molecules are changing
position.
• Available as pigments, paints
and inks and used in many
everyday applications
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• Appear to change colour
with a change in the level of
UV light.
• Used for coatings on
spectacle lenses.
• Can also get photochromic
paints and pigments.
Prepared by Dr Diane Aston, IOM3
Armourers and
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• Liquid crystal-based
materials that change colour
at the flick of a switch.
• The polymer molecules are
charged so they align in the
presence of an electrical field
giving an opaque or tinted
appearance.
• When the applied field
disperses the molecules
return to a random
arrangement and the
material becomes
transparent.
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Armourers and
Brasiers Company
• These are probably the oldest group of smart
materials.
• Although the effects were first discovered in
natural minerals such a quartz and this is still used
in some instances, we now tend to use complex
man-made minerals with a crystal structure
designed to give the most exaggerated effect.
• Smart ceramics can be described as:
• Piezoelectric
• Pyroelectric – used in thermal imaging cameras
• Ferroelectric – used in RAM for computers
Prepared by Dr Diane Aston, IOM3
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• First discovered by the Curie brothers in 1880 in quartz.
Now lead zirconate titanate (PZT) most commonly used.
• They generate an electrical field when pressure is applied to
change their shape.
• They change shape when an electrical current is applied.
• Found a wide variety of uses:
– Microphones and guitar pick ups
– Car air-bag actuators
– Linear motors
– Damping systems, e.g. in skis
– Flat panel speakers
– Energy harvesting
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• Quantum tunnelling composite (QTC) is made of a
fine nickel powder dispersed in a polymer resin.
• Discovered in 1990s and now exclusively produced
and licensed by Peratech, the company set up by
the inventor, at their site in North Yorkshire.
• The material is now used in applications
worldwide and has even been into space!
Prepared by Dr Diane Aston, IOM3
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Brasiers Company
• With no applied pressure it
is a near perfect electrical
insulator.
• If enough pressure applied
it is a reasonable metallic
conductor.
• Electrical resistance of
varies with applied
pressure in a predictable
way.
• The current flows by
electrons jumping between
the sharp points on spiky
metal particles.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
Sports
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– Fencing jacket touch senor
– Training shoes pressure analysis
Functional textiles
Consumer electronics
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Touch sensitive screens
Mouse buttons and games controllers
Wii board and dance mats
Flexible piano keyboard and drums
Flexible qwerty keyboard
Medicine
– Blood pressure cuff tension check
– Respiration monitor
– Functional prosthetic limbs
• Industrial
– Variable speed controllers for tools
– Sensing for robotics
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
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Not all smart materials are
solid!
Magneto-rheological fluids
consist of fine iron particles
suspended in a liquid such as
glycerol or vegetable oil.
In the a absence of a magnetic
field the material behaves as
a liquid.
When a magnetic field is
applied the particles in the
materials align and the liquid
becomes solid.
Used in braking and damping
systems.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• Smart materials are an interesting collection of
metals, polymers and ceramics with some useful
properties.
• Smart materials can act as sensors and actuators
that can be incorporated into larger systems to add
a degree of automation or functionality.
• New uses for smart materials are being found all
the time and these developments are being led by
materials specialists.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
Armourers and
Brasiers Company
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
If time permits all students should have a go at all activities.
However you may split the group in to three and each work on
one type of materials and then give feedback to the whole.
• Investigating thermochromic polymers
• Investigating shape memory alloys
• Investigating QTC
Prepared by Dr Diane Aston, IOM3
• Artefacts containing thermochromic pigments such as colour
changing baby feeding spoons, bath ducks and egg timers are
relatively cheap and readily available.
• Thermochromic sheet and paints are available from
Mindsetsonline.
• You could also have a go at some of the experiments in the
SEP Publication Hot and Cold: exploring temperature
changes with thermocolour film, available from the
National STEM Centre eLibrary.
• If you do not have the facilities to carry out practical work
you could get your students to research thermochromic
polymers and come up with an idea for a new application.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• In order to be able to do any practical investigative work on
these materials you will need some samples. The best place
to get them (if you haven’t already) is Mindsetsonline who
sell shape memory metal superelastic wire, one-way wire and
springs and wire and two-way coils.
• A range of activities are available in the SEP publication
Metals and Smart Alloys available from the National STEM
Centre eLibrary.
• If you do not have the facilities to carry out practical work
you could get your students to research SMAs and come up
with an idea for a new application.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
• QTC samples are available to purchase at a very low cost from
Mindsetsonline and you can get ideas of activities you can do
with the material in the SEP publication QTC: A Remarkable
New Material to Control Electricity available from the
National STEM Centre eLibrary.
• If you do not have the facilities to carry out practical work
you could get your students to research QTC and come up
with an idea for a new application.
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
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The Wikipedia articles on thermochromic, photochromic and electrochromic
polymers, shape memory alloys, nitinol and piezoelectric ceramics contain
some useful technical information.
The National Physical Laboratory do a considerable amount of research on
piezoelectric materials (and they also have some good general education
resources!)
The Peratech site contains a wealth of interesting and useful information on
QTC.
The National STEM Centre eLibrary contains many useful publications and
ideas for activities relating to all types of smart materials. You need to
register to use the site but it doesn’t cost anything to do this.
Although you can buy some examples of smart materials over the counter,
some are a bit trickier to source. The best supplier we have found is
Mindsetsonline who sell most of the smart materials discussed in this
module.
The IOM3 Discovery Boxes also contain examples of all these smart
materials, for more information on how to borrow a box contact
[email protected]
Prepared by Dr Diane Aston, IOM3
Armourers and
Brasiers Company
Armourers and
Brasiers Company
Prepared by Dr Diane Aston, IOM3