Hello everyone, today i would like to tell about such a refractory metal as rhenium.
Without it, there wouldn't be (wouldn't exist) high octane petrol
and modern internal combustion engines.
In the periodic table of chemical elements, rhenium belongs to group 7
and is located on the bottom next tungsten.
Rhenium is one of the least abundant metals in earth’s crust.
It is truly a very rare and precious metal.
Because of being so rare, rhenium was discovered only in 1925
by three German scientists.
Today this metal is extracted as a by-product in molybdenum mining
from such a mineral as molybdenite.
Pure ammonium perrhenate, that metallic rhenium is extracted from,
is obtained as a result of refining and concentration of the ore.
The main product used for producing rhenium is rhenium powder,
which is later baked or melted into small drops.
Drops of this metal shine very well because of being highly resistant to oxidation by oxygen in the air.
Besides, the density of rhenium is just one percent smaller than that of osmium
the densest metal on Earth.
That is why such a small drop weighs a whole gram and costs whopping 15 euros.
When this drop is compared to one gram of lead,
the difference in size becomes evident.
Besides being high-density, this metal also has a high melting point,
which is just 236 Celsius degrees smaller than that of tungsten.
This metal is the second most refractory metal.
If a drop of rhenium is heated until red-hot with a powerful gas burner
you will see the drop of this metal start oxidizing at high temperatures.
It is also noteworthy that from temperatures higher than 250°C
the rhenium oxide layer will become volatile on the surface of the metal,
because of its low boiling point.
Besides, such a volatile metal paints
the flame in yellowish and greenish color.
This property of rhenium oxide is used to make
rhenium electrical contacts, which last a long time because rhenium oxide simply disappears
under the surface of the contacts,
leaving the shiny metal not oxidized.
Let us continue testing now this rhenium drop
and throw it into concentrated nitric acid.
Now, nothing seems to be happening.
Upon heating up, things get more interesting:
The rhenium drop slowly starts to dissolve in the acid, creating nitrogen oxide and rhenium acid,
which is very soluble in water.
Thus, we are aching the surface of the metallic rhenium drop
to see its structure.
After drying up and being throughly washed,
we can clearly see the crystal structure of the metallic drop in microshot.
It looks stunning.
However, this metal is not known for its beauty,
but rather for it's unusual properties and uses.
One of it's major properties is its extremely high melting point and its ability to make
an alloy with nickel and other metals.
That is why rhenium has recently begun being used for superalloys.
Such alloys can stand high pressure at high temperatures.
That is why they're used in the construction of reactor engines
especially those of military vehicles.
However, the most interesting use of rhenium to date
is in the production of high octane petrol.
The thing is, during regular rectification of oil
the light [inaudible] components releases
which easily detonates upon the application of high pressure
inside the automobile motor cylinder.
To avoid that, they get reformed.
That is, deprived from hydrogen.
The process of which is also known as isomerization.
In other words, it is decreasing the boiling temperature
and is increasing the octane number.
Usually in such a process, sillica gel covered rhenium and platinum particles are used
as a catalyst.
As a result, it creates petrol with high octane number that makes engines more efficent
and saves fuel.
To sum up I can say that rhenium is a metal
that not much is known about, but it is an extremely useful metal.
Without it, we wouldn't be able to drive gasoline powered efficent vehicles.
For the provided rhenium, I would thank the company Onyxmet.com
I will put a link to their site in the video description.
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