Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM 3
Armourers and Brasiers Company The future is materials Prepared by Dr Diane Aston, IOM 3
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, IOM 3 Armourers and Brasiers Company
Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM 3
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, IOM 3 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, IOM 3 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. Prepared by Dr Diane Aston, IOM 3 • Chosen for their functional properties: – Optical properties – Electrical properties – Thermal properties – Magnetic properties – Smart behaviour Armourers and Brasiers Company
• 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, IOM 3 Armourers and Brasiers Company
• 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, IOM 3 Armourers and Brasiers Company
• 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. Prepared by Dr Diane Aston, IOM 3 Armourers and Brasiers Company
• 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 kink-resistant. Prepared by Dr Diane Aston, IOM 3 Armourers and 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. Prepared by Dr Diane Aston, IOM 3 Armourers and 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, IOM 3 Armourers and Brasiers Company
• A number of different types of smart polymers which exhibit useful behaviour • • • Thermochromic materials Photochromic polymers Electrochromic polymers Shape memory polymers Strain and shear rate sensitive polymers Prepared by Dr Diane Aston, IOM 3 Armourers and Brasiers Company
• 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, IOM 3 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, IOM 3 Armourers and Brasiers Company
• 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. Prepared by Dr Diane Aston, IOM 3 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, IOM 3 Armourers and Brasiers Company
• 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, IOM 3 Armourers and Brasiers Company
• Quantum tunnelling composite (QTC) is made of a fine nickel powder dispersed in a polymer resin. • Discovered in 1990 s 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, IOM 3 Armourers and 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, IOM 3 Armourers and Brasiers Company
Sports • – Fencing jacket touch senor – Training shoes pressure analysis Functional textiles Consumer electronics • • – – – • 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, IOM 3 Armourers and Brasiers Company
• • • 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, IOM 3 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, IOM 3 Armourers and Brasiers Company
Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM 3
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, IOM 3
• 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 e. Library. • 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, IOM 3 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 e. Library. • 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, IOM 3 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 e. Library. • 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, IOM 3 Armourers and Brasiers Company
• • • 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 e. Library 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 IOM 3 Discovery Boxes also contain examples of all these smart materials, for more information on how to borrow a box contact diane. aston@iom 3. org Prepared by Dr Diane Aston, IOM 3 Armourers and Brasiers Company
Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM 3
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