Look through the text and choose the headings
for each part. пустоSmart materials
Basic
materials are those that have been in use for centuries, such as paper, wood,
stone and metals. We have also developed *** materials.
Concrete,
aluminium and steel are all commonly used *** materials, but there are more.
Graphene is
a single carbon layer material, which is hypothetically 100 times stronger than
steel. It is hypothetical because we are yet to manufacture it in large enough
quantities to prove this.
Titanium is
a *** metal and is used in sporting and medical applications. It is an
excellent material for these purposes as it has a high strength-to-weight ratio
and is resistant to corrosion.
Metal foams
are a strong but lightweight *** material produced by injecting a gas or
foaming agent into molten metal. Metal foams are often used in vehicles such as
planes and cars as they absorb shock effectively if the vehicle crashes.
пустоModern materials
***
materials exhibit a physical change in response to some external stimuli.
Shape-memory
alloys (SMA) are metal alloys that can remember their shape when heated.
Nickel
titanium (nitinol) is a type of SMA, and it contracts when heated, whereas most
metals expand.
Thermochromic
pigments change colour when their temperature changes. The term ‘thermo’
relates to heat, and chroma means colour - so thermochromic pigments change
colour when they are heated up. An example of this technology is seen on
colour-changing cups.
Photochromic
pigments work in a similar way but 'photo' refers to light - so these pigments
change their properties when exposed to ultraviolet (UV) light. A well-known
example is glasses where the lenses are clear inside a building, but become
more like sunglasses when exposed to bright sunlight outside.
Self-healing
materials have the ability to repair themselves, which can extend the lifespan
of the products that use them. These include polymers that can heal knife cuts
in themselves, metals that resist corrosion and concrete that can heal when
cracked.
пустоComposite materials
***
materials are a combination of natural and synthetic materials. *** are
produced with fibres, particles and sheets which is especially important in building
industry.
Fibre-based
*** are reinforced with fibres. By mixing resin or concrete with fibres of
glass or carbon we get the ability to mould complex shapes, but reinforcing
them with the fibres makes them very strong.
Particle-based
*** are made with small particles of material. By mixing smaller particles of
sand with larger particles of cement and aggregate, such as stones, we get a
very strong and dense material for building large structures.
Sheet-based
*** are often available in large sheets. By mixing wood fibres or thin slices
of wood with resin, it is possible to form large and stable sheets for interior
construction.