The blackest material on Earth should have no color at all since black is no color. Black is the extent of not seeing an object! A thing which reflects no light or minimum light by absorbing almost all of it appears black. So an absolutely black material should reflect no light (a perfect black body) and we don’t see the absolutely black object. What is the blackest material on Earth?
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What is the blackest material on Earth?
As the blackness of the material depends on the light-absorbing capacity of it, enhancing the light absorption capacity makes a material blacker. Modern research has led to blacker materials as we march to the pinnacle of technological development. So, the blackest material on Earth is changing with technological advancements and at the recent time it is vantablack (vertically aligned carbon nanotube (CNT) arrays black) or VACNT (vertically aligned carbon nano tubes).
Modern super black materials
Dark chameleon dimmers : Dark chameleon dimmers are gold nanoparticles which has extraordinary light absorption capacity and can absorb light as high as 99.2% to a fixed wavelength light of 497 nanometers whereas it has absorption greater than 98% in other visible and infrared region of light.
Vantablack : Completely different from gold nanoparticles, vantablack is a material made from CNTs and has 99.96% of optical absorption for the light of 663 nanometers wavelength. This material consists of vertically aligned CNTs over a substrate metal so that the light falling on it continually strikes on the vertically aligned wires and gets absorbed.
The absorption of vantablack is being improved by the researchers. The changes in different parameters such as the substrates, length of CNTs, nanotube growth procedures, etc can affect the absorption values.
The blackest material till date
Most recent development of the CNTs has enabled scientists to achieve reflectance value of 0.00001 i.e. absorption of 99.999 %. A group of scientist at MIT have recently developed a material whose absorption is 10 order of magnitude greater than the recent best absorbers within a wide range of frequencies of light. That makes it the blackest material on Earth till date.
This material has CNT – a metal hierarchical structure which means CNTs are grown over the metal substrate. The metal used was surface activated aluminium over which vertically aligned CNTs were grown from oxygen dehydrogenation reaction.
An ideal black body
An ideal black body is a material which absorbs 100% of light incident upon it. As for physicists, there exists no perfection and world has flaws. So, there is no such object as a perfect black body and hence the term ideal is introduced.
A black hole can be considered as an ideally black object. No light can be reflected from the black hole and it does not give any color hence appears black. The absorption, in this case, is due to the strong gravitational attraction of the black hole while it is due to the vibrational absorption in case of materials.
Application of such black materials
Black materials absorb light well. So, mostly they can be used for the absorption of light. Light absorbers are used in cameras, telescopes and other optical instruments in order to absorb the stray light.
The black materials are widely used in solar power concentrator. Since they absorb almost all the light energy incident upon them and get heated, they can be used for water heating purpose as well as electricity generation. They are also used by artist to change the contrast of color.
The enhancement of material science is inducing the evolution of materials. So, blackest material on Earth is evolving and we will see new materials much blacker than the one that is now. So, today it is VACNT and in coming days it might be another one which absorbs nearly 100% of light.