Hello everyone! Today I'd like to tell you
about the lightest material on planet Earth - Aerogel
As a matter of fact there exist quite a lot kinds of aerogel
some of them consist of metal oxides
for instance aluminium oxides
Others can consist of carbon tubes and graphenes
By the way, such an aerographene is a few times lighter than air
However, I cannot manage to get this rare material
that is why today I am going to show you classic silicon dioxide based aerogel
As you can see, this material is very fragile
and it crumbled when it was transported in the package
When aerogel crumbles are put on paper sheet
it looks translucent and very light
and it is almost invisible against a light background
Aerogel's density is extremely small
about 1/10th of a gram per cubic centimeter
The density of aerogel of higher quality
can even be compared to that of air.
It's not surprising because aerogel mostly consists of air.
To illustrate what aerogel's structure is like
we can compare it to that of any other gel like substance
For instance water ball or shampoo
Now try to imagine that our water in such a material has been substituted with air.
Roughly speaking, this is what aerogel looks like from inside - small porous material filled with air or another gas.
It's quite easy to make aerogel.
First, regular silica gel has to be made
for instance by mixing together tetraethyl orthosilicate and ammonia solutions in methanol medium.
Later such a gel is washed with methanol
in order to wash away all traces of water.
After that it is sent to a supercritical extractor
Let the complex names not scare you
because everything works as simple as a bicycle
Carbon dioxide is pumped under pressure into such an extractor
after that, the case of the extractor starts to heat up
The liquid carbon dioxide passes to the supercritical state that is become something between liquid and gas
In such a state, it can easily wash away methanol from gel substituting it with gas.
This is how aerogel forms.
The first thing you can notice when working with this material
is the sound it makes when falling on the solid ground
Since aerogel has a solid silica framework
it makes a lot of noise when it hits another surface
Besides, aerogel is one of the best heat resisting materials
Heat conductivity of which can be lower than that of air
I decided to conduct a classical experiment with it
I put a small flower on a piece of aerogel and started heating up the aerogel with a powerful blue torch
The flower withers on the edge, but it practically doesn't change in the middle
If we take the smaller flower and more powerful gas burner, the effect will be even better observed
I'm heating up the aerogel with a very powerful spot burner
with the temperature exceeding 1000°C
but nothing is happening to the flower because it is protected by the most heat resistant material
Such a low heat conductivity is also the result of extremely small pores of this material
that rarely exceed 30 nanometers in diameter
It's even smaller than the mean free path of a gas molecule before colliding with another such molecule
By the way, I also noticed that upon heating up the surface of aerogel starts melting
because silicon dioxide this material consists of, begin to melt at such high temperatures
However, not everything is so rosy, there are certain cons too
First of all, aerogel is very fragile. Look at how easily it crumbles when slightly pressed.
Later, it turns into fine powder, as it is hard to remove
The main problem with aerogel, especially with silica aerogel however
is the fact that it is hydrophilic
Because this material has hydroxyl groups on it's surface
When it comes into contact with water aerogel soaks all the liquid
and turns into a whitish surface, similar to colloidal silicon.
Thus if water is spilled on aerogel, it will immediately loose it's unique properties
and will turn into quite expensive rubbish.
Anyway, progress does not stand still
and people have managed to make water resistant aerogel
with the help of some hydrophobic materials
It substitutes hydroxyl groups on the surface with hydrophobic ones
The production and use of this material is steadily growing
Some companies have invented flexible aerogel, having mixed silica gel pieces with fibrous tissue
This material is widely used for insulating rooms and also for making modern warm and light clothes
Besides aerogel pieces can perfectly absorb extremely small particles
because of that, they are used as comet dust catchers on stardust spacecraft
Also because of large surface area, carbon aerogel can be used to make supercapacitors
and silica aerogel can be covered with particles of other materials and used as an effective catalyst in the chemical industry
It's also noteworthy that aerogel is used for thermal protection in some cars
for instance in the transmission of Chevrolet Corvette C7
As a result we can say that aerogels are modern and useful materials
new uses of which we are yet to discover
for the provided aerogel I'll thank the company Onyxmet.com
I'll put the link to their site in video description
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