Whether
you're trying to dig for diamonds or drill to the center of the earth
or simply trying to cut into one of my mom's over-baked cakes. You're
going to want a pretty strong material, but assuming that there's no unobtainium
or adamantium lying around, where can you turn just.
What is the strongest
stuff that we can get our hands on?
Well, turns out
it really depends on what you're trying to do, because materials can be strong
in different ways depending on which direction the stress is applied.
In if we
take something and squeeze it, we are subjecting it to compressive stress
and to withstand that stress without breaking it needs a large enough compressive
strength. If instead of squeezing we pull it in opposite directions, we are
subjecting it to tensile stress and the material must have enough tensile
strength to resist the force.
In real-life
situations through objects are subjected to a combination of these stresses, as
well as shear stress, which comes from forces sliding past each other to
be of any use to the heroically minded. The world's strongest material must be
able to withstand all these kinds of forces.
In reality,
though most materials are either high in tensile strength or compressive
strength, for example, it's fair to say that concrete is pretty
strong. They certainly thought so in the 60s, opting to build basically
everything out of that gray Wonder stuff, and it does have a pretty high
compressive strength. Able to withstand up to 14 mega Pascal's of pressure.
This is what you get if you balanced 325,000 London buses on a phone box.
But when it comes to tensile and flexural strength, that's its
resistance to stretching and bending, it's around eight times
weaker and will fail when exposed to a stress of just 5 mega Pascal's.
To properly
understand what makes something strong, we need to delve into the microscopic
and see exactly what it is that holds stuff together. You might remember from
your school chemistry lessons that the molecules in a material are held
together by bonds. There are lots of different types of bonds: ionic, covalent,
metallic, but they all basically work in the same way, to strongly
attract atoms to each other. It's these bonds that help a substance hold
its structure. Without them, you'd have gas.
So if bonds
are what hold solids together, it makes sense to say that the more bonds the
stronger the solid will be, right? Well, yeah, kinda. Kinda because there is a
limit to how many bonds every atom can make.
Carbon, for example, can only bond with
four other atoms. Oxygen only with two. So as you
can't have an unlimited number of attachment points between atoms, the arrangement
of the bonds.
The atomic structure
of a substance becomes very important. Take graphite and diamond,
both are made of pure carbon, but their atomic structure is very
different. Graphite is the soft black stuff in pencil lead and it has
its carbon atoms arranged in flat sheets which can easily slide over each other.
When it's exposed to shear stress like drawing a pencil across a piece
of paper, those super weak bonds break and sheets just get wiped off.
In contrast, a diamond which many people recognize as one of the world's hardest materials, and more on that later. That has its carbon atoms held together in a regular 3d
pattern, an interlocking tetrahedral structure, now
with each atom locked tightly in the structure is brilliant at distributing force:
there are no weak links to limit material strength.
So, in our search for the world's strongest material,
should we be looking at the atomic scale for a perfectly even crystal
structure to share the load when force is applied, well it makes sense but no
sorry. In reality, a material can actually be made stronger by the presence of imperfections
and defects in that atomic order. Any breaks in the perfect order
of bonds can help to stop any cracks or deformation. In fact, several
techniques for developing stronger and stronger materials have attempted to do
just that, introduced imperfections through processes such as grain
boundary and solid solution strengthening.
Back to Diamond
then. If it's so hard then why hasn't anyone had the genius idea of making indestructible
diamond body armor or building towering diamond skyscrapers. Well,
even if you manage to get enough diamonds together and do such a thing, you'd
be sorely disappointed. While the diamond is extremely strong, not very tough. Plus,
it's incredibly brittle, which means that just a relatively gentle
hammer strike would be all that you've been needed to shatter the entire
structure. While strength is defined as the maximum stress that material
can support before starting to break. Toughness describes a material's ability
to absorb energy and deform before breaking.
In most
materials you can either have strength or toughness just like a diamond
which is very strong but not very tough, it will break really easy when the
right kind of stress is applied, or like aluminum which is tough and can
deform easily without breaking which nobody in their right mind would describe
as strong.
So for all
practical purposes, the world's strongest material needs the best of both
worlds, strength, and toughness which given that as one increases
the other tends to decrease, it's no easy task.
So what can
we do? Well, as with all great innovations like penicillin, gliders,
and leopard print jeggings. Material scientists turn to the natural
world for inspiration, where geology has failed us in providing the frankly
inferior diamond. Biology can pick up the slack. Deep in the Madagascan
jungle, Darwin's bark spider is casually producing one of the
world's strongest materials out of its backside. From spiracles on
its abdomen, this spider produces silk, whose extraordinary
composition achieves that holy grail of material strength and is both strong
and tough. In fact, this dragline silk which is produced by the spider
as the first anchoring strand of one of the largest webs in the world has a tensile
strength that is several times that of Steel. All while being only 1/10
of the width of a human hair.
Exactly why it
is so strong? is still poorly understood, but we do know that is made up of two
different types of proteins. The first forms an amorphous stretchable
matrix, which gives its elasticity, and the other has a form of pleated
crystalline structure, which gives it its strength. The organization of the
two types of proteins within the Strand makes it a biological marvel,
and one that scientists have been very keen to develop.
But you know
what we can do better than that. Remember the graphite in our pencil lead,
just that slight pressure and a sideways swipe is all it takes to shear off
layers of carbon atoms, it isn't strong and it isn't tough but
keep sliding those layers off separating the ultrafine leaves off the
graphite book and you can find yourself with a substance that
is quite remarkable.
You see when
you're left with just a single sheet of carbon atoms all bonded to each other
in a hexagonal pattern; you don't have graphite anymore; you have graphene,
and graphene is being widely proclaimed as one of the strongest
materials have ever been made.
First
developed in 2004, it also achieves the highly desired combination of strength
and elasticity. In fact, it's able to stretch by up to 25% of its
original size before it breaks-and it's able to withstand an impressive amount of
localized force, a thin film requires a pressure equivalent to an
elephant standing on a pencil point before it breaks. With such impressive
credentials, you'd think that graphene would have been snapped up for
all manner of engineering and defense applications, but in actual fact, no one
really knows what to do with it. Most ideas involve combining graphene
with another material such as plastic or rolling it up into fibers,
but at the moment it is so costly to separate individual atom thin layers of
carbon that such composite materials are not economical to develop.
So, whether
you choose to get your super-strong material out of spider's butts. All through
expensively deconstructing a pencil, it's clear that scientists are still some
way from achieving true indestructibility. This is just as well because as
soon as they do they're probably going to start making those fiddly plastic
packets at graphene and it's going to be no hope for any of us.
I want to
know if you had access to the world’s strongest material, what would you do
with it.
Let us
know in the comment:
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