Hello everyone
Today I want to tell you about this refractory and also a conflict-making metal, Tantalum.
In the periodic table of chemical elements
Tantalum is located in the fifth group
among the so-called transitional refractory metals.
Due to its rarity and difficulty in obtaining
Tantalum was named after the Greek king, Tantalus.
According to the legend, he offended Zeus and the other gods
for which he was cast out of heaven
for an eternal torment.
Like the ancient Greek king, many scientists and researchers have suffered and endured trying to obtain this element in its pure form.
Externally Tantalum looks like a grey shiny metal
and by the weight, quite heavy.
In its density it comes next after the Gold.
If you take the current market price, 1kg of Tantalum costs around $150.
Therefore this metal is quite expensive.
Tantalum is very ductile; it's very easy to make a wire or foil from it.
This metal is extracted from the mineral Coltan
the deposits of which are located in Brazil
but especially rich deposits of Tantalum ores
are formed in Central Africa.
Recently Tantalum is referred to as a conflict-making metal
because a lot of African countries are fighting to get their hands on it.
For example, in Congo and Rwanda there are military conflicts
associated with the smuggling of Tantalum ore.
From about the last decade, about nine African countries
and twenty different military groups
were involved in the Tantalum wars.
However, let's go back to the chemical properties of the Tantalum metal.
From the chemical point of view, this metal is extremely stable.
It's not soluble in dilute acids
even in the Hydrochloric acid
due to a very robust oxide film covering the metal.
One of the very few caustic environments that can dissolve Tantalum
is a mixture of Hydrofluoric acid and Nitric acid
in which, from the Tantalum, a complex compound forms
that is soluble in water.
In the form of a powder, Tantalum burns quite well in air
forming the Tantalum Oxide.
In spite of all this chemical stability
this metal also reacts well with molten alkalies
forming Tantalates.
For example, if you pour a bit of dry Sodium Hydroxide on the Tantalum foil
and then melt it
such an aggressive environment can easily dissolve the Tantalum
and burn a hole in the Tantalum foil.
Though that's pretty much it. You cannot conduct any other special chemical experiments with Tantalum
due to its inertness.
The only thing we can do is heat a Tantalum rod
and see how fast will it oxidize
in the hot flame of a gas burner.
After such an abuse, Tantalum rod gets covered with a white and inert substance
Tantalum Oxide, from a reaction with Oxygen in air.
This material is also used in creating glass
that absorbs gamma rays.
Because of its plasticity and chemical stability
in the olden days Tantalum was used for making filaments for light-bulbs
but later, with the rise of the price for this metal
Tantalum was replaced with the much cheaper Tungsten.
The internal resistivity of Tantalum
is comparable to the one of steel
hence this element can be used to create heating elements instead of using Nichrome
especially in places where you need a very high temperature, as Tantalum melts
at more or less about 3,000 degrees Celsius.
So, for example
it's possible to heat the Tantalum wire, and it will not oxidize as much.
At the moment, one of the most important applications of Tantalum
is in manufacturing the most efficient Tantalum capacitors
in Electronics.
In the capacitors, like anode a very fine Tantalum powder is used
which is pressed around the Tantalum wire
and is sintered to the form of a sponge.
Then such sponge is anodized - i.e. covered with a layer of Tantalum Pentoxide
that acts as a dielectric layer.
Next the anodized Tantalum sponge is covered with a layer of the cathode, of Manganese Dioxide.
Then, on top, a layer of Graphite and a layer of Silver is added.
And now the capacitor is ready.
The advantage of these capacitors is that they can be made to be extremely small
due to the very thin dielectric film.
These kind of capacitors can be put into any computer, smart phone or a tablet.
So say thanks to Tantalum
for the smart phones.
Recently jewellers are trying to use Tantalum in the jewellery
as this metal is quite dense and is completely non-toxic to humans.
Now even the Chinese sell Tantalum rings.
Hmm, would you give a Tantalum decoration?
In my opinion it would be quite original.
However, Tantalum by itself is grey
and doesn't shine as beautifully as Gold.
That, I decided to fix with the help of electro-chemistry.
For this I took a piece of Tantalum foil
and placed it into the solution of table salt
and then connected it to the anode of the power source that will pick up electrons from the metal.
As cathode you can take the same plate of Tantalum foil, or another piece of metal.
Next, and the most easy part, you simply need to input the necessary voltage
and voila, grey Tantalum becomes golden.
The higher the voltage, the more interesting will be colours of the anodized Tantalum.
In this photo you can see what colour will the anodized Tantalum take
depending on the voltage.
That is, the higher the voltage the more blue will be the colour.
So you may ask, what happens in this miracle system?
It's actually quite simple.
Depending on the applied voltage on the Tantalum foil, which is the anode
a layer of Tantalum Oxide is formed.
The higher the voltage, the thicker will be the film of oxide on the metal surface.
The thickness of the film will change the colour reflected from it
in consequence of the effect of superimposing waves
of the reflected light and the light transmitted through the film layer.
Through the gradual removal of the metal from the solution you can get some beautiful effects
like a rainbow colouring
or a colour gradient.
Sometimes you can get cool masterpieces
with a simple power supply and paste.
So in theory you can attach a new colour to the Tantalum wedding ring
every year of life being together
because the oxide film is almost un-erasable
and the new ones will be brighter and bluer.
I feel that you can attach a whole philosophic theory to this effect.
After playing with this system, I got some interesting samples that you are now seeing on the screen.
In addition to these aesthetic purposes
now pure Tantalum is also used in the creation of super-alloys
for example, in the alloy of Titanium and the alloy of Hafnium.
Additionally, due to the excellent bio-compatibility of Tantalum
it is used as a bio-prosthesis in surgeries.
Ever since the year 2006, Kazakhstan issued commemorative coins made of Silver and Tantalum.
For providing Tantalum for the experiments, I will thank the company
Stanford Advanced Materials
I put a link to their site in the video description.
Now you know a little bit more about one of other metals.
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