Name: 碳纳米管将如何改变世界（How Carbon Nanotubes Will Change the World）
Uploaded: 2021-06-09T12:43:33.000Z
Duration: 19 min 35 s
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In 1991 a Japanese physicist, Sumio Iijima, conducted a momentous experiment.

An experiment that introduced the world to material so strong that it could revolutionise

Taking two graphite rods as electrodes, Sumio applied a current across the rods.

A spark arched between them and with it a cloud of carbon gas puffed into existence,

As the carbon laden air settled on the chamber walls it formed a thin layer of black soot,

within it a strange new material appeared.

Sumio Iijima had just created carbon nanotubes.

Laboratory testing of these mysterious little tubes in the following years would reveal

that these nanometer-wide hexagonal lattices of carbon had the strongest tensile strength

known to man, and this was just As one of the many incredible material properties they

Carbon nanotubes are light, conductive and biocompatible.

It soon became clear that the carbon nanotube had the potential to be the building block

The most efficient computers, transformative medical devices, synthetic muscles, or perhaps

the most ambitious of all, space elevators, the dream of countless sci-fi authors,

Carbon nanotubes has promised to be the catalyst for the next revolution in technology.

But, putting this revolutionary material to work will not be easy.

It turns out that building a fibre, that is actually a single molecule, of any significant

To understand this fascinating molecule, let's dive into the chemical makeup of carbon nanotubes.

It's in everything we eat, sleep on and step over.

It is the element that holds our DNA together.

It forms the carbohydrates, proteins and lipids that we depend on to build and fuel our bodies.

It's ubiquity in our lives is a result of its versatility.

It's chemical properties allow it to take many different shapes, each impacting it's

material properties in diverse and unique ways.

To understand this we need to understand the basic models of how we visualize electron

To start we have the simplified bohr model, which separates the electrons into shells.

The first shell can contain 2 electrons, while the next shell can hold 8.

An atom wants to fill each shell to be stable.

Let's take an atom of carbon, which has 6 electrons, to see how this plays out.

First we fill the first shell with it's 2 electrons, then we have 4 electrons left

to fill the next shell, leaving 4 open positions in its outer shell

The 4 open positions mean that carbon willingly interacts with many other elements as well

Often by sharing electrons in a special type of bond, called a covalent bond.

This versatility allows carbon to create many different kinds of molecules.

Hydrogen has 1 electron, and seeks 1 electron to fill it's inner shell.

So, carbon likes to form 4 covalent bonds with 4 hydrogen atoms to form a stable 8 electron

outer shell, while helping hydrogen form a stable 2 electron shell.

This is methane, an incredibly common molecule that is the main ingredient in natural gas

This is just one arrangement carbon can take.

Hydrocarbons take a huge range of shapes and configurations, but what we are interested

in is how carbon bonds to itself, but this simplified Bohr model doesn't give us an

understanding of how carbon to carbon bonds take radically different shapes.

We need to dive a little deeper before we can understand the magic of carbon nanotubes.

Electrons don't travel in neat 2D circular orbits as the Bohr model would suggest, in

fact we can't even know the position and speed of an electron.

Instead we can make predictions about electrons' general locations in 3D space.

We call these orbitals, and they are regions where we have about a 90% certainty that an

electron is located somewhere within that region.

This can get pretty complicated, but for now we just need to concern ourselves with two

S orbitals are spherical in shape with the nucleus of the atom at their centre.

P orbitals are often called dumbbell shaped, but I don't know what gym these nerds are

going to, because I have never seen a dumbbell like this.

It's more like a figure of 8 shape like the infinity symbol.

In the ground state, electrons will occupy the lowest energy orbitals first, which in

Next we have the 2S orbital, which is a larger sphere, and can also hold 2 electrons.

Then we have our three P orbitals, one aligned along the X, Y and Z axis, each capable of

Carbon in its ground state has the 1S and 2S orbitals filled, with one electron in the

To be stable, Carbon wants to fill these three p orbitals with 2 electrons each.

Now this where things get a little funky and confusing, and it will be on your final exam.

Carbon can bond to itself in different ways that affect these orbital shapes.

To fill these orbitals, carbon bonds with 4 neighbouring carbon atoms.

To do this it promotes one electron from it's 2S orbital into the empty Pz orbital.

[5] This Pz orbital is higher energy than the 2S orbital, and the electron doesn't

want to stay there, so the carbon atom takes on new hybrid orbital shapes to compensate.

This is called sp3 hybridisation, which is a mixture of S and P orbital shapes and looks

Where one side of the figure of 8 expands while the other contracts.

The 2S and 3 P orbitals are transformed into these new SP3 orbital shapes.

They repel each other equally in this 3D space to form this four lobed tetrahedral shape

Covalent bonds now form between the carbon molecules where these orbital lobes overlap

This creates a repeating structure like this and it's this rigid framework of carbon

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碳纳米管将如何改变世界（How Carbon Nanotubes Will Change the World）

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