iom3 materials presentation
TRANSCRIPT
Dr Diane Aston
Materials in Action
Dr Diane Aston Training and Education Executive The Institute of Materials, Minerals and Mining
All of the materials we use around us come from natural resources that are found somewhere in the Earths crust.
Dr Diane Aston
Materials in Action
First we have to find them... Geologists,
geophysicists and geochemists explore the globe and find the pockets of useful natural resources. Assess whether the deposit is a viable resource. Viable resources are called reserves.Dr Diane Aston Materials in Action
Then we have to get them out... Mining engineers
decide on the best way to get the useful natural resources out of the ground. Surface extraction in quarries. Underground extraction from mines. Pumping from below ground.Dr Diane Aston Materials in Action
Then we extract the useful stuff... Minerals engineers use a
range of physical and chemical techniques to separate the useful material from its natural resource. Physical processes include crushing and grinding, flotation and magnetic separation. Chemical reaction used to isolate particular materials.Dr Diane Aston Materials in Action
Processing
Structure
Properties
Dr Diane Aston
Materials in Action
We can make hundreds of thousands of materials from the elements; we split these up into four main groups.
The Chemists Perspective
Classes of materialsMetals Polymers
Ceramics
Composites
Structural and functional materials
Characterising materials
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Materials in Action
Improvements in our technology have gone hand in hand with the discovery of new materials or improvements in our understanding of the ones we have already.
Dr Diane Aston
Materials in Action
Materials for jet engines
Materials for aircraft
Materials for cars
Materials for sports equipment
Materials for body parts
Materials for packaging
Materials for communication
Smart materials
Nanotechnology
Dr Diane Aston
Materials in Action
Summary Materials play a vital role in our modern society. Without new materials our technology would stand
still. Materials Scientists and Engineers play a vital role in developing new materials and improving the technology we rely on. Please take the materials that are used around you a little bit less for granted!
Dr Diane Aston
Materials in Action
[email protected] www.iom3.org www.iom3.org/sas
Dr Diane Aston
Materials in Action
Dr Diane Aston
Materials in Action
Understanding processing Materials are
processed, formed, shaped or manufactured to make the products that we take for granted. Processing generally involves the application of heat and force.
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Casting processes Pour molten material
into a mould to make a component close to its final shape: Injection moulding and
die casting Sand casting and
investment casting Continuous casting
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Forming processes HOT WORKING above
about two thirds of the melting point. COLD WORKING below two thirds of the melting point. Rolling, extrusion, drawing, forging used to make wide variety of shapes.Dr Diane Aston Materials in Action
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Finishing processes Machining used to: Remove waste Drill holes Improve surface finish Traditional cutting tools
are very hard (tungsten carbide, silicon carbide, PCD, tool steels). Modern methods include laser cutting, electrical discharge machining and water cutting.Dr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
Understanding structure All materials are comprised of atoms.
How are the atoms bonded together to form
molecules or crystals? How are the molecules or crystals arranged?
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The number of electrons in the outer shell and their distance from the nucleus affects the type of bonding and this in turn affects some of the materials properties. Aim is to have an outer full electron shell.Covalent Ionic Metallic Weak bonds Mixture and compounds
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Covalent bonding Characterised by atoms
sharing pairs of electrons to achieve a full outer shell. Tend to be poor electrical and thermal conductors and have relatively low melting points. Can form single molecules or large macromolecules.Dr Diane Aston Materials in Action
Bonding
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Covalent bonding Electrons have the
same negative charge and since like charges repel each other they try to be as far away from each other as possible. This leads to molecules with specific fixed shapes.Dr Diane Aston Materials in Action
Bonding
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Ionic bonding Characterised by
electrostatic attraction between oppositely charged ions in order to get a full outer electron shell. Tend to conduct electricity in liquid state and have relatively high melting points. Can form large crystal lattices.Dr Diane Aston Materials in Action
Ionic bonding Ionic crystal lattices can take on a number of different
geometries depending on the relative size of the ions. There are 14 possible crystal structures.Sodium chloride adopts a face centred cubic structure Caesium chloride adopts a body centred cubic structure
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Bonding
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Metallic bonding Characterised by sharing
of free electrons among a lattice of positively charged nuclei. Tend to be good electrical and thermal conductors. Form close packed lattices due to nondirectional nature of the bonding.Dr Diane Aston Materials in Action
Metallic bonding Different ways of laying up planes of close packed atoms. Three main equilibrium crystal structures but others are
possible.Hexagonal close packed
Face centred cubic
Body centred cubic
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Bonding
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Weak bondsVan der Waals forces Intermolecular force Sum of attractive and
Hydrogen bonding Interaction of hydrogen
repulsive forces between molecules. Important in polymer chemistry, nanotechnology and surface science.
atom with an atom of oxygen, nitrogen or fluorine from another molecule or within the same molecule. Reason that water expands slightly as it freezes.
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Bonding
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Mixtures and compoundsCompound Made from two or more chemical elements held together in a particular spacial arrangement by chemical bonds. Properties are different to those of
Mixture Made from two or more chemical substances by mechanical means (e.g. stirring, shaking, melting). Properties closely related and dependent on ingredients.
the constituent elements. Elements are present in a specific and constant ratio water is always two hydrogen and one oxygen.
Ingredients can be present in any ratio. Ingredients can be separated by mechanical means (e.g. filtering, evaporation, magnetism).
Elements can only be joined or separated by a chemical reaction.Bonding Home
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It is important to know how the individual molecules or crystals in a material arrange themselves with regards to each other.
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Crystalline materials In a crystalline material the atoms or molecules arrange
themselves in a regular way and this pattern is constant throughout the material. A monocrystalline material exhibits long range order. In a polycrystalline material the atoms in each individual crystallite or grain have the same structure but the orientation varies between adjacent grains.
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Non-crystalline materials Amorphous materials only demonstrate short range
ordering. Glassy materials show no ordering at all.
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Materials in Action
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Dr Diane Aston
Materials in Action
Atoms Central nucleus
containing protons and neutrons which give the atoms its mass. Electron cloud surrounds nucleus and does not contribute towards mass. Number of protons and electrons is equal.Dr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
Understanding properties Physical and chemical properties: Melting and boiling point, density, corrosion resistance, toxicity. Structural or mechanical properties: Strength, toughness, hardness, stiffness (Youngs Modulus), ductility, malleability, fatigue and creep resistance. Functional properties: Magnetic properties, thermal properties, electrical properties, optical properties, Smart behaviourDr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
Metals Most of the elements in the Periodic Table are
metallic. Metallic materials tend to: have good mechanical properties be ductile, malleable, sonorous and lustrous be good electrical and thermal conductors
Wide range of densities, melting points and corrosion
resistance.
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Alloys Dont tend to make things out of pure metals. Making metal 100% pure can be difficult. Having some kind of impurity can improve
properties. Alloys are made by mixing different metals and nonmetals together in different proportions. An infinite number of alloys with exactly the right properties.
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Substitutional alloys Formed when the
solvent and solute metals have about the same atomic radius. Slightly larger or smaller atoms introduce strain into the crystal lattice which provides strengthening.
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Materials in Action
Interstitial alloys Formed when the
solvent atoms are much larger then the solute atoms. Solute sits in the gaps in the lattice and make it more difficult for the planes to slide across each other.
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Materials in Action
Alloy composition - simple Simple alloys are made by mixing just two metals
together. By changing relative proportions of constituents can alter properties. For example: Brass mixture of copper and zinc Bronze mixture of copper and tin Solder mixture of lead and tin
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Materials in Action
Alloy composition complex More complex alloys involve the addition of more than one ingredient. Each ingredient contributes towards improving properties in a particular way. Mixture of substitutional and interstitial
ingredients. For example: Steel is Fe and C with other elements added to give
particular properties such as Nb, Ti, N, Ni, Cr, Mn, B, Si Ni-based superalloys contain Cr, Mo, Mn, Al, Fe, B, Re, RuDr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
Polymers Tend to be covalently bonded organic compounds
consisting of large molecules of repeated structural units. Poly many, mer parts Includes many natural and synthetic materials. Tend to have relatively low melting points and densities, electrical and thermal insulators.
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Materials in Action
Polymers Molecules tend to have long backbone with side
groups coming off. Geometry of molecules dictates whether polymer will be crystalline or amorphous. Can be split into three subgroups: Thermosoftening materials Thermosetting materials Elastomers
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Thermosoftening polymers Often called thermoplastics, they can be melted and
shaped by the application of heat. Consist of long, covalently bonded molecules held together by weaker Van der Waals forces. Can be elastic and flexible or glassy and brittle. Include PE, PP, PS, PC, PVC, PMMA.
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Thermosoftening polymers Non-renewable materials
originating from oil. Can be recycled provided they are sorted. Very durable materials, lasting for many hundreds of years without degradation. Many used in low-tech, high volume applications such as packaging, textiles and seating.Dr Diane Aston Materials in Action
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Thermosetting polymers Molecules bonded together by cross links to create a
continuous three dimensional lattice. Once a thermoset has solidified in a particular shape it cannot be remelted. Tend to be stronger than thermoplastics but more brittle. Include melamine, epoxy resin, bakelite, vulcanized rubber.
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Elastomers Can be thermosoftening or thermosetting.
Generally consist of cross-linked 3D networks. Characterised by ability to extend considerably
without plastic deformation. Include natural rubber and synthetic rubbers such as nitrile, butyl, polybutadiene, silicone rubber.
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Dr Diane Aston
Materials in Action
Ceramics Inorganic, non-metallic solid prepared by the action
of heat and subsequent cooling. Can be crystalline or amorphous. Bonding can be ionic, covalent or a mixture. Can have very high melting points. Strong and stiff in compression but brittle. Can be electrical and thermal insulators or conductors.
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Four groups of ceramicsStructural ceramics Clay-based materials Bricks, pipes, tiles
Engineering ceramics Used for their thermal, electrical or impact properties Oxides, nitrides, carbides
Refractories Kiln linings, fire retardants, crucibles
Whitewares Earthenware, stoneware, porcelain for tableware, sanitaryware,
pottery and tiles.Dr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
Composites Made by mixing two materials from the other groups
together. New material has superior properties to constituent materials. Defined by the matrix or background material and the reinforcement material. By changing size, type, shape and amount of reinforcement the properties can be controlled.
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Polymer matrix composites Matrix can be a thermoset such as epoxy resin or
thermoplastic such as PP. Reinforcement can be in the form of glass, carbon or Kevlar fibres. Properties can be controlled by changing type, size, shape and amount of reinforcement. Strong, lightweight materials but expensive to manufacture.
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Materials in Action
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Dr Diane Aston
Materials in Action
Structural & functional materialsStructural materials Been using these materials
Functional materials Started to make an impact
for thousands of years. Chosen for their structural or mechanical properties: Strength
on our technology in the last 50 years or so. Chosen for their functional properties: Optical properties Electrical properties Thermal properties Magnetic properties Smart materialsHome
Toughness Hardness Stiffness
Used in the construction of
everything around us.Dr Diane Aston Materials in Action
Dr Diane Aston
Materials in Action
Characterising structure
Characterising properties
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Materials in Action
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Characterising structure Characterise structure in many ways: Measure grain size Measure particles Measure degree of crystallinity
Measure relative amounts of different constituents
To do this we have to be able to observe the material
on many levels.
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Macrostructure This is the scale that
we live at. Can look at the material with the naked eye or use a magnifying glass or stereomicroscope. Typical magnification is x2 to x10 and observing at a scale of a few millimetres.Dr Diane Aston Materials in Action
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Microstructure using light Optical microscopy,
using either transmitted light or reflected light can be used to look at structure on a micrometre scale. Typical magnification of up to a few hundred times.
240m
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Microstructure using electrons Scanning electron
microscopy used to look at magnifications of up to a few thousand times. Useful for looking at surfaces as get more appreciation of topography. Sample needs to conduct electricity so may need to coat in gold or carbon.Dr Diane Aston Materials in Action
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Looking even smaller... Transmission electron
microscopy can be used to observe materials on the nanoscale. Useful for characterising defects and particles in materials. Use thin films or carbon replicas.Dr Diane Aston Materials in Action
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Looking smaller still... Scanning tunnelling
microscope is used for imaging surfaces at the atomic level and can achieve a resolution around 0.01 to 0.1 nanometres. Atomic force microscopy newer and even more powerful.Dr Diane Aston Materials in Action
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Analysing structure and composition X-ray diffraction can be
used to determine crystal structure in metals. Various spectroscopy techniques can be used to analyse chemical composition.
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Materials in Action
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Dr Diane Aston
Materials in Action
Characterising properties A range of techniques can be employed to quantify
properties Mechanical testing to quantify structural properties is of great importance to Materials Engineers
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Quantifying strengthThe Tensile Test: Uses standard test specimen which has a section with a constant cross section gauge length. Test piece is clamped into the machine and a load applied steadily until the specimen fails.Dr Diane Aston Materials in Action
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Tensile test resultsCERAMICYield point Ultimate tensile strength
Stress
METAL
POLYMERStiffness
Strain
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Quantifying toughnessThe Impact Test: Uses standard test specimen with a notch on one side. Sample is placed in machine and hit with a swinging hammer. Measure energy required to break the sample at different temperatures.Dr Diane Aston Materials in Action
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Impact test results Materials experience a
Temperature
change in behaviour from ductile to brittle at a particular temperature (DBTT) Behaviour varies with crystal structure. Other factors also affect toughness.
Energy
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Materials in Action
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Quantifying hardnessThe Vickers Hardness Test A small pyramidshaped diamond is pressed into the surface of a polished sample under a given load. Measure indent to get hardness number.Dr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
Materials operate in and environment of extreme stress and temperature in this safety critical application but jet engines are beautiful pieces of engineering.
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Materials in Action
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How a turbofan works
Fan
Compressor
Turbine
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Materials for the fan Blade design was limiting
factor in jet engine size. Fan diameter 2-3 metres. Blades need to be lightweight, strong and stiff. Titanium blades made by super-plastic forming and diffusion bonding. Blades have a hollow, corrugated cross section.Materials in Action
This photograph is reproduced with the permission of Rolls-Royce plc, copyright Rolls-Royce plc 2010
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Engine
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Materials for the compressor Air entering the
compressor is squeezed causing to speed up and heat up. When it exits the high pressure compressor it is at around 600C. Compressor blades made from titanium as it is strong, light and able to operate at 600C.Dr Diane Aston Materials in Action
Engine
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Materials for the turbine Forced rotation of turbine
drives rest of engine. Operate under extremes of temperature and pressure. Made from nickel-based superalloy. Blades attach to disc with fir tree root. Blades have in-built cooling system.Materials in Action
Dr Diane Aston
Engine
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Dr Diane Aston
Materials in Action
We are always looking for better materials to build bigger aircraft that can fly further and faster and carry more people more efficiently. Minimising weight is paramount!
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Materials in Action
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Traditional aircraft materials Wood, canvas and piano
wire have been replaced! Undercarriage made from very high strength steels. Engines made from complex alloys. Frame and skin made from aluminium alloys. Constant driving force to decrease weight...Materials in Action
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Modern aircraft materials Metallic materials
superceeded by modern composites. Strong, tough, stiff and lightweight. About one third of A380 made from composites: GLARE and CFRC Fuselage of B787 is all CFRC.Dr Diane Aston Materials in Action
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Dr Diane Aston
Materials in Action
We all want more efficient cars. Advanced materials are helping to drive down weight and improve safety standards. Materials are also vital and in the development of new fuel technologiesCars Fuels
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Materials in Action
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Materials for car structures Body panels have changed
from steel to aluminium to polymer and composite materials. Polymeric materials used in trims, bumpers and upholstery. Body frame made from steels or aluminium. Engines contain range of materials including steels and aluminium alloysDr Diane Aston Materials in Action
Cars
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Materials for fuels Traditionally fossil fuels
have been used. Alternatives such as biodiesel from used cooking oil and bioethanol from sugar beet now available. Electric cars rely on battery technology. Hybrid cars now available.Dr Diane Aston Materials in Action
Cars
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Hydrogen fuel cells Proton exchange membrane
fuel cell. Anode and cathode have
channels etched into surface to ensure gas is dispersed fully. Proton exchange membrane is
separates anode and cathode. Platinum catalyst facilitates
reaction of hydrogen and oxygen.
Dr Diane Aston
Materials in Action
Cars
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Dr Diane Aston
Materials in Action
Improvements in sporting performance tend to be down to the introduction of new materials rather than the athletes.Cycling Pole vaulting Tennis
Swimming
Javelin
Protection Home
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Materials in Action
Materials for cycling Bicycle frame design
has changed little since the 1880s. Steel used for most everyday bikes, but aluminium and titanium alloys used for higher specs. Carbon fibre composite used in competition cycles.Dr Diane Aston Materials in Action
Sport
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Materials for pole vaulting Poles originally made
from hickory and then bamboo. Modern poles made from carbon and glass fibres embedded in an epoxy resin matrix. Composite poles are efficient at storing and releasing energy as they bend and then straighten.Dr Diane Aston Materials in Action
Sport
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Materials for tennis Originally made from solid then
laminated wood. Aluminium frames introduced
in 1970s. Modern racquets made from
CFC with fibres laid up to give optimum properties. Bigger head means more power. Carbon nanotubes now used
to give even greater performance.
Dr Diane Aston
Materials in Action
Sport
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Materials for swimming As swimmer moves through
the water three types of drag are created. Frictional drag accounts for most of this (up to 29%). Speedo Fastskin suit can
reduce drag by 4%, the Tyr Aquashift suit claims to reduce drag by upto 10%. Fabric is covered in pattern
which mimics shark skin.Dr Diane Aston Materials in Action
Sport
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Materials for javelin IAAF rules state that javelin
must be 2.6-2.7m and >800g for men or 2.2-2.3m and >600g for women. Centre of mass moved forwards by 4cm to make the nose heavy and reduce possibility of it being thrown out of the stadium. Made from steel or aluminium alloys.
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Sport
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Materials for protection Traditional materials
are bulky and can restrict natural movement. D3o is lightweight and flexible but its stiffness is strain rate dependent. Absorbs impact energy to protect the body.Dr Diane Aston Materials in Action
Sport
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Dr Diane Aston
Materials in Action
Biomaterials are being used alongside and inside the body to repair and replace broken or worn out body parts.Hips Blood vessels Lenses Limbs Tissue engineering Home
Knees
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Materials in Action
Materials for hip replacements Artificial hips have
changed since their introduction. Surgical steel and nylon replaced by UHMWPE and other alloys. Ceramic coatings can be used instead of bone cement.Dr Diane Aston Materials in Action
Body parts
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Materials for artificial knees Made from similar
materials to artificial hips. Recoat natural joint by covering bottom of femur and top of tibia. Polymer plate acts as man-made cartilage.
Dr Diane Aston
Materials in Action
Body parts
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Materials for vascular grafts Vascaular grafts can be
sewn in or inserted into a blood vessel to provide reinforcement or repair. Made from woven polyester fabric.
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Materials in Action
Body parts
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Materials for prosthetic limbs Early examples made from
wood. Carbon fibre composites, lightweight alloys and polymer foams are used to create prostheses that look and behave like the limbs they are replacing. Modern prosthetic limbs incorporate electronics and are designed with increased functionality.
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Materials in Action
Body parts
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Materials for intraocular lenses Used to replace the
lens of cataract patients. Inserted into eye through a small incision. Made from PMMA.
Dr Diane Aston
Materials in Action
Body parts
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Materials for tissue engineering Use of man-made materials
as a scaffold on which to grown natural tissues. Man-made scaffold, such as PLA, PCL PGA, dissolves over time. Possible to grow simply structure such as skin, vascular grafts and bladders. More complex organs may be possible in the future.Dr Diane Aston Materials in Action
Body parts
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Dr Diane Aston
Materials in Action
Modern functional materials have revolutionised our communications industry.
Processing
Transmitting
Storing
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Materials in Action
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Materials for processing data Microchips made from
silicon. Silicon is the second most common element in the Earths crust. Very pure silicon is processed in order to change its structure and properties. Can produce chips with millions of electronic components.Dr Diane Aston Materials in Action
Comms
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Processing silicon Structure modified on a
microstructural level: polycrystalline to monocrystalline. Single crystals are sliced to produce very thin wafers. Structure is modified on an atomic level by doping to make it easier for electrons to flow through the structure.Dr Diane Aston Materials in Action
Comms
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Materials for storing data Before the advent of the
printing press the only way to store information was to manually copy manuscripts. Early computers used punched cards. Magnetic storage on tapes and discs has a higher storage density and allows re-recording. Optical technology is used for CDs and DVDsDr Diane Aston Materials in Action
Comms
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Materials for storing data Now possible to store
large amounts of data on a very small drive. Hard discs use magnetic storage technology on a much smaller scale than cassette or video tapes.
Dr Diane Aston
Materials in Action
Comms
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Materials for transmitting data Traditional copper
cables are being replaced by optical fibres with a much greater data capacity. Light is used to transmit signals over larger distances with less loss of signal.
Dr Diane Aston
Materials in Action
Comms
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Dr Diane Aston
Materials in Action
Packaging must fulfil a large number of criteria, from looking good to extending shelf life. Materials are chosen to meet the needs of the particular product.Paper & board
Metals
Plastics
Glass
Modern
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Materials in Action
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Metal packaging Two-piece cans, three
piece cans, tubes, trays, foil and closures. Materials used include tinplate, tin free steel and aluminium. In UK 8 billion food cans and 9 billions drinks cans per year. Packaging can be sorted and recycled.Dr Diane Aston Materials in Action
Packaging
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Plastics packaging Lightweight, durable
packaging materials. Use thermoplastics such as LDPE, HDPE, PP, PET, PS, PVC. Used for bottle, trays, tubes, tubs, closures and cushioning. Starch-based biopolymers being developed.Dr Diane Aston Materials in Action
Packaging
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Glass packaging Traditional packaging
material early vessels date to 1500BC. Inert, rigid, heat resistant and recyclable, but heavy and brittle.
Dr Diane Aston
Materials in Action
Packaging
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Paper and board packaging Wide range of papers
and boards used in packaging. Raw materials is cellulose fibre from wood, straw or cotton or recycled paper. Making folded cartons requires many stages.
Dr Diane Aston
Materials in Action
Packaging
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Modern packaging Active packaging used to
extend shelf life by trapping the gases produced as food goes off, controlling humidity or providing a protective atmosphere. Intelligent packaging indicates a change in internal or external conditions. Enhanced traceability with RFID tags.Dr Diane Aston Materials in Action
Packaging
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Dr Diane Aston
Materials in Action
The term Smart Materials was introduced in the 1960s to group together a group of metals, polymers, ceramics and composites with some unusual properties.
Metals
Polymers
Ceramics
Composites
Other
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Materials in Action
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Dr Diane Aston
Materials in Action
Many alloys are available but Nitinol most commonly used. It is made from nickel and titanium. The Ni-Ti ratio controls the memory temperature and the useful property can be changed by changing processing conditions.Superelastic Two way One way
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Materials in Action
Smart
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Superelastic behaviour 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.Dr Diane Aston Materials in Action
SMA
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Two way temperature memory Different structures
above and below memory temperature. Change over small temperature range. Change in structure generates a force, so can be used as a switch in a temperature controlled circuit.Dr Diane Aston Materials in Action
SMA
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One way temperature memory Remember a memory
shape above or below the memory temperature . Can be bent to shape during use and then reset by heating / cooling. Trained by heating and then quenching. Can go through thousands of cycles.SMA Home
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Materials in Action
Dr Diane Aston
Materials in Action
A number of different types of smart polymers which exhibit useful behaviour
Thermo
Photo
Electro
SMP
Visco
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Materials in Action
Smart
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Thermochromic polymers 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 applicationsDr Diane Aston Materials in Action
Polymers
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Photochromic polymers 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.
Dr Diane Aston
Materials in Action
Polymers
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Electrochromic polymers Liquid crystal- based
materials that change from transparent to opaque (or tinted) at the flick of a switch. Molecules align in the presence of an electrical field and then become randomly oriented as it disperses.Dr Diane Aston Materials in Action
Polymers
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Shape memory polymers SMP return to their
memory shape when heated to their memory temperature. Materials tend to be thermosetting polymers that can be reinforced with fibres.
Dr Diane Aston
Materials in Action
Polymers
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Strain and shear rate sensitive polymers The viscosity or stiffness
of some polymers changes depending on how quickly they are deformed or how easy it is for them to flow. Polyborosiloxane (Silly Putty) is a good example and is used in a number of commercial applications.Dr Diane Aston Materials in Action
Polymers
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Dr Diane Aston
Materials in Action
Probably the oldest group of smart materials. No longer simple natural materials; they are complex man-made minerals with a crystal structure designed to give the most exaggerated effect.Piezo Pyro Ferro
Dr Diane Aston
Materials in Action
Smart
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Piezoelectric ceramics First discovered in 1880 in quartz. Now lead zirconate
titanate (PZT) most used. Generate an electrical current when pressure is applied to change shape. 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 harvestingMaterials in Action
Dr Diane Aston
Ceramics
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Piezoelectric ceramics This actuator consists
of 300 layers of piezoelectric ceramic. It is designed to change in length by 1.5m per millimetre of its length. Used to control the amount of diesel injected in to the cylinder to optimise fuel efficiency.Dr Diane Aston Materials in Action
Ceramics
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Pyroelectric ceramics Closely related to piezoelectric
materials but in this case the electrical potential is produced by a change in temperature rather than shape. As the temperature changes the ions in the structure move and the material becomes polarised thus producing and electrical potential. Most common application is in heat sensing intruder alarms and thermal imaging cameras.Dr Diane Aston Materials in Action
Ceramics
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Ferroelectric ceramics These are spontaneously polarised and the direction of
polarisation can be switched by the application of an external field. Their behaviour can be compared to ferromagnetic materials. Vital to our electronics-led society as they can be used for capacitors and memory cells. These materials are used to make RAM for computers and radio frequency identity cards. These applications use a thin film of ferroelectric materials as these allow high field to be generated to switch the polarity, with the application of only a moderate voltage.
Dr Diane Aston
Materials in Action
Ceramics
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Dr Diane Aston
Materials in Action
Quantum tunnelling composite (QTC) is made of a fine nickel powder dispersed in a polymer resin.
Dr Diane Aston
Materials in Action
Smart
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QTC useful properties With no applied pressure
it is a near perfect electrical insulator. If enough pressure applied it is a reasonable good conductor. Electrical resistance of varies with applied pressure in a predictable way.
Dr Diane Aston
Materials in Action
Smart
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QTC - applications Sports Fencing jacket touch senor Training shoes pressure analysis
Functional textiles Consumer electronics
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 prothetic limbs
Industrial Variable speed controllers for tools Sensing for robotics
Dr Diane Aston
Materials in Action
Smart
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QTC how it works Metal particles are not
smooth spheres, rather they have a very spinkey surface Electrons can jump between the points to allow a current to flow Quantum Tunnelling
Dr Diane Aston
Materials in Action
Smart
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Dr Diane Aston
Materials in Action
Dr Diane Aston
Materials in Action
Smart
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Smart fluids 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.Dr Diane Aston Materials in Action
Smart
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Other smart materials Magnetostrictive materials are similar to piezoelectric materials but they change shape in a magnetic field. Terfenol-D is one material. They are used in: Sensors and actuators Ultrasound and sonar equipment Hearing aidsBar contracts if field applied Base state of material Bar expands if field applied
Dr Diane Aston
Materials in Action
Smart
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Dr Diane Aston
Materials in Action
Study of the design, characterisation, manipulation, production and application of materials on the nanoscale.
Definition
In nature
Coatings
Composites
Future
Dr Diane Aston
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What is nanotechnology?Football (22cm) Flea (1mm) Hair (80m) Red blood cell (7m) Virus (150nm) Buckyball (0.8nm)
1m
10-1m
10-2m
10-3m
10-4m
10-5m
10-6m
10-7m
10-8m
10-9m
10-10m
1m
1mm
1m
100nm
1nm
100nm
80nm
60nm
40nmSunscreen TiO2 (35nm)
20nmDNAstrand (2nm)
1nm
Dr Diane Aston
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All a matter of scale Materials have unusual properties on the nanoscale
because of the huge surface area.Cube edge length 1 metre 0.5 metre 1 centimetre I millimetre 1 micrometre 1 nanometre Number of cubes in a cubic metre 1 8 1,000,000 1,000,000,000 1018 1027 Total surface area (m2) 6 12 600 6,000 6,000,000 6,000,000,000
Dr Diane Aston
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Macroscale versus nanoscale On a 1cm3 of material around 10 in 1 million atoms
are on the surface. On a 1nm3 of material 4 out of 5 atoms are on the surface.Material Aluminium Copper Macroscale property Stable Opaque Nanoscale property Combustible Transparent
GoldPlatinum Silicon
Solid at room temperatureInert Insulator
Liquid at room temperatureReactive Conductor
Dr Diane Aston
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Creatures and plants have evolved to exploit materials on the nanoscale in the most efficient way.
Dr Diane Aston
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Gecko grip Gecko is able to run upside
down. Has millions of nanoscale hairs on each toe which are individually attracted to the surface by Van der Waals forces. When combined these forces are sufficient to allow superb grip. Could still cling on carrying a 200 times its own weight!Dr Diane Aston Materials in Action
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Stenocara beetle Lives in the Namib Desert
where water is scarce. Water from atmosphere condenses on bumps on its back. Rest of body is hydrophobic so the water is channelled directly into the beetles mouth and none is wasted.
Dr Diane Aston
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Anti-glare eyes Many moths have anti-
reflective coatings on their eyes. These surfaces are very rough on the nanoscale and prevent light reflecting Coating makes it more difficult for predators to see them.
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All the colours of the rainbow Nanolayers and nanoparticles
used to give the effect of colour. Butterfly wings appear brightly coloured. Mother of Pearl on shells has a pearlescent appearance. Amazing sunsets caused by scattering of light.
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Coatings can be applied to provide a number of benefits including scratch resistance and surface smoothing.
Dr Diane Aston
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Superhydrophobic coatingsWater repellent materials!Textile coatings Self-cleaning windowsNanoparticle Water forms droplets on Dirt
Droplet
the surface which run off carrying dirt with them.Textile
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Scratch resistant coatings Nanoparticles of silica
or alumina can be added to paint for scratch resistance. Seven layers of paint are applied and top coat of lacquer contains nanoparticles.
Dr Diane Aston
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Anti-glare and anti-reflective coatings
Mimic moths eyes.
Reduce light reflection
and improve light transmission. Spectacle lenses Computer screens Car instrument panels
Dr Diane Aston
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Pollution-reducing coatings TiO2 in coating acts as
a catalyst to break down NOX and SOX pollution. Transparent coating. Could coat whole cities to reduce smog.
Dr Diane Aston
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UV barrier coatings Sunscreens use TiO2
particles to stop bad UV light from damaging the skin whilst letting the tanning radiation through. Traditional sunscreens appear white on the skin. If nanoparticles are used they scatter the light in such a way that they appear transparentDr Diane Aston Materials in Action
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Colour-effect coatings Colour without pigment
Examples from ancientLycergus Cup Roman dating to 400AD 400ppm gold and 300ppm silver 70nm nanoparticles
civilisations Modern examples Perfume bottles Car paints Consumer goods
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Coatings to fill surface defects Nanoparticles can sink
in to small surface defects to give a smoother appearance. Paints
Polishes Face creams Tooth paste
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Nanoparticles are added to other materials to provide reinforcement, strengthening and other useful properties.
Dr Diane Aston
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Barrier properties Nanoparticles of clay
added to tennis ball materials to slow the diffusion of oxygen. Balls can be used for longer. Hydrophobic coating on surface too.
Dr Diane Aston
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Antimicrobial properties Antimicrobial properties
of silver know since ancient times. Nanoparticles can be added to textiles to provide antimicrobial properties: Wound dressings Clothing
Nanoparticles can be
added to polymers too.Dr Diane Aston Materials in Action
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The future of nanotechnology New applications are being found all the time and it is
likely that nanotechnology will impact all areas of our lives: In medicine to deliver drugs and aid healing In communications to increase processing speeds In transport to reduce weight and improve fuel efficiency In construction to build longer, lighter bridges
Dr Diane Aston
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Dr Diane Aston
Materials in Action
The Material MapH Li Be Na Mg K Ca Sc Ti Rb Sr Y V B C N P O S He F Ne Cl Ar Al Si
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr I Xe
Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
Cs Ba Lu Hf Ta W Re Os Ir
Pt Au Hg Tl Pb Bi Po At Rn Uuq Uuh Uuo
Fr Ra Lr Rf Db Sg Bh Hs Mt Uun Uuu Uub
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Ac Th Ps U Pu Am Cm Bk Cf Es Fm Md No LrThe Materials Engineers Perspective