The Institute of Making - Network Rail engineering education (10 of 15)


Uploaded by networkrail on 27.03.2012

Transcript:
[train passing]
♪ background music ♪
(Zoe) Hello, my name's Zoe Laughlin
and I'm a materials expert.
I'm one of the directors
of the Institute of Making
at King's College London.
At the heart of our institute
is the most wondrous collection
of materials - a materials library that
has stuff from NASA, stuff from mines,
stuff from my garden shed.
But is all about celebrating the
ordinary and extraordinary nature
of materials.
Materials are around us all the time.
They're what makes up the world and so
it's very difficult to do any subject
without encountering materials:
it might be arts, it might be design,
it might be technology,
it could be music, you know
but the matter, the stuff that makes up
the objects that we use
is our materials.
And it's the use of materials science
that really is central to some of
the most extraordinary feats
of engineering today.
So what I'm going to do today,
is show you some of our
favourite materials from the collection
and reveal how the structures inside
those materials give them really
wondrous characteristics
and properties.
So this first material I'm going
to show you is a pretty unassuming
stick of tin.
All metals are made up of crystals.
So this tin stick has crystals inside
which, when you bend the tin,
they slide over each other and
they don't move easily - in fact,
so uneasily do they move
that they make a noise
and they grate over each other
and you can hear the cry of tin.
So here's the sound:
[crack, crack]
That's a rather crispy, cracky sound.
[crack]
That's the crystals
sliding over each other.
And what you get is actually vibrations
in the hand.
The material which is bendy and soft
actually feels like glass shattering
and splintering.
So you can hear the crystals in the
tin stick but actually
in this piece of aluminium
you can see them; you can see
just how small they can really be.
But actually we have an example
of another material which is just
one whole metallic crystal: that's this
single crystal jet turbine engine blade
and this whole object
is one metallic crystal. And it's made
by having the liquid metal in the mould,
cooling it here and then starting to
pull it out of the mould.
And that makes the crystals grow
in this downwards direction and
they grow a bit like Christmas trees
with these arms that race forwards and
compete with each other
to travel through this helix
and actually, what happens is
at the end of the helix
only one crystal arm
has actually got to this point.
It's blocked off the others behind it.
And it solidifies this whole object.
And that enables it to be made from
one crystal and have no
grain boundaries,
no boundaries between those crystals,
and therefore have no potential cracks
and be really high performance object
that can operate in a jet engine under
massive temperatures, massive pressures
and yeah, be pretty much indestructible
in that situation.
Now this material really is magical.
This is aero-gel,
which is the lightest solid
in the world.
It's made by NASA,
for catching stardust.
It's basically a silicone foam,
a kind of glass foam if you will,
but the pores of the foam
are nano-scale. Teeny tiny pores.
And this gives it very specific
properties.
Predominantly, this blue colour.
So this material is blue
for the same reasons
that the sky is blue.
It's due to the way in which the light
passes through it and scatters.
So it's not blue because of a pigment
and to do with absorption and
reflection. This is the way the light
passes through it.
What they do is take it up and
expose it to the vacuums of space
and all the tiny particles of dust
that are flying around get a chance to
whack into this material
and lodge themselves inside it and then
they can be brought down to earth
and examined.
Because it contains so much air,
it's a really good insulator.
And if I hold this piece in my hand
it's actually warm to the touch.
It's incredible.
Next up, we have a ceramic.
And not just any ceramic.
A super conductor.
Now this is extraordinary.
Something very special happens
when you get it very cold.
And the best way to get things
cold quickly is liquid nitrogen.
So I'm trying to cool this ceramic
to -197 degrees centigrade.
So if I take this magnet
and I bring it into contact
with the ceramic
something extraordinary happens.
It levitates! Look at that!
[laughs]
Brilliant!
I can even push quite hard and
it's not going to touch the ceramic!
Those lines of magnetic field
that previously passed straight through
the material are now being repelled
just by making it extremely cold.
Look at that! It's amazing!
It's levitating!
Superconductors are so named because
when they're at these
extremely cold temperatures
they conduct electricity
extraordinarily efficiently.
And if we were able to make materials
that could do that at room temperature
it would revolutionise
the electricity industry.
Now we're moving onto something
completely different.
This is a material which
almost skirts the boundary between
animate and inanimate, living and dead.
This is a bio-glass scaffold.
A material which is made to be
an implant into the body,
a kind of substitute for bone
but you impregnate it with proteins
and stem cells, and when
it's in your body you actually start
to grow and eat into it
and it turns into bone, the idea being
if you were to break your wrist and,
you know, have a nasty fracture
and this kind of thing
you might have had pins and bars
put in your arm but you can actually
cut back to nice clean bone,
nice flat ends
and make a piece of this stuff
and implant it in that gap.
And you impregnate it with stem cells
and protein, close your arm up,
and then your body starts
to eat this material and grow into it
and it turns into your own bone.
So in a couple of years' time
you don't have an implant any more,
you just have your own bone.
Composition wise this is
a kind of glass. Reason being,
that the body doesn't reject glass.
It's relatively inert,
so it can sit happily inside us.
This material has been engineered
to have this strange, porous,
crater-like structure so that
when the bone starts to grow,
it can actually start to grow
in three dimensions and burrow its way
down inside the material. And, in fact,
it's designed to no longer exist.
It's designed to be impermanent because
in a few years' time you no longer have
this material implanted in your body
you just have your own bone.
I can't tell you what the
exact composition of this is because,
like many materials in our collection,
this is straight from a research lab
and it's either secret or
it's not fully known,
they haven't published the research.
But this is cutting edge science.
Now this is what they make
aircraft out of.
It's basically the walls and the floor,
that kind of thing.
It's incredibly strong,
really, really light.
Both important properties for
materials for aircraft.
And how they do it is, essentially,
by sandwiching this stuff
in between this composite material
making it rigid.
And this is an aluminium honeycomb.
Now it's actually quite weak this way,
but really strong in compression
in this direction.
And this starts off life...
...like this.
And what we've got here
is sheets of aluminium
which are glued together on these nodes
and then it gets pulled out,
beyond its elastic limit,
until it stays rigid in this structure.
And then can be faced
and turned into aircraft.
So this is a great example
of the relationship between materials
and the shapes you make them into.
It's the same material
all the way through,
but a different shape
gives it a different property.
So there we have it.
There's just a few of the
extraordinary materials we have here at
the Institute of Making.
But what I hope you can
take away from this is a sense that
these properties are due to
the structures inside materials
and that understanding that is what
material science is all about.