Conny Waters - AncientPages.com - Scientists have discovered the oldest known human-made nanomaterials in the “unique black coatings” of ancient pottery shards — dated to 600 BC — unearthed from an archeological site in Keeladi, Tamil Nadu.
These are “the oldest nanostructures observed till now,” according to a new study. These coatings are made of carbon nanotubes (CNTs).
CNTs have enabled the layer to last more than 2,600 years, raising questions on the tools used during those periods to achieve high temperatures for making earthenwares.
“Until this discovery, to our knowledge, the most ancient known nanostructures in human-made artifacts are from the eighth or ninth century AD,” study co-author Vijayanand Chandrasekaran from Vellore Institute of Technology (VIT) in Tamil Nadu told PTI agency.
Chandrasekaran explained that CNTs are tubular structures of carbon atoms arranged in an ordered manner, and they have remarkably strong mechanical properties. The researcher said that coatings in ancient artifacts may not usually last this long due to wear and tear caused by changing conditions.
However, the CNT based coating as the one discovered in Tamil Nadu had helped the layer sustain more than 2600 years.
“But the people of this time may not have intentionally added CNTs, instead, during the processing at high temperatures, these would have just formed accidentally.
If there is some processing of the potteries, which probably would have involved some high-temperature treatment, then it will add more justification to the findings,” said nanomaterial scientist M. M. Shaijumon from IISER Thiruvananthapuram, adding that carbon nanotubes have superlative properties, including high thermal and electrical conductivity, and very high mechanical strength.
According to Mr. Chandrasekaran, the closest scientific explanation for the finding is that some “vegetal fluid or extract” might have been used in the coatings of these pots which may have led to the formation of CNTs during high-temperature processing.
See also:
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Rajavelu S., Professor of History at Alagappa University in Tamil Nadu, who was unrelated to the study, told PTI that the people of this time may have added or coated something similar to plant-sap to the inside of the pots, and subject it to the nearly 1100-1400 degree Celsius high-temperature fire treatment as seen in kilns.
“This fire treatment may have led to the formation of the coating which has likely strengthened the pot and made the coating durable,” Mr. Rajavelu told PTI.
“Normally with high-temperature processing of carbon, they form these type of tubular nanostructures, but until about the 1990s, there were no sophisticated instruments available to characterize them. So these structures are already even present in nature and only now we are observing them,” explained Mr. Shaijumon.
Mr. Rajavelu concurred, and said the ancient people would not have known these as CNTs but may have just had the need to make their pots have high durability, “and may have needed a certain color out of their products on applying high-temperature firing."
"They likely knew the technique to make these coatings practically, but may not have known this as a thesis with any kinds of formulae,” Mr. Rajavelu added.
Commenting on the significance of the research, Sharada Srinivasan, an expert in archaeometallurgy associated with the National Institute of Advanced Studies (NIAS) in Bengaluru, said nanotechnology has made strides since the 90s with the advent of advanced techniques like scanning tunneling microscopy.
“But it is increasingly recognized from archaeological studies that past skilled artisans sometimes accidentally or empirically made nanomaterials — such as the famous Egyptian Blue — without being aware of the science of working at the nano-scale,” Ms. Srinivasan told PTI.
Based on their analysis, Mr. Chandrasekaran said the ancient Tamil civilization of this time were aware of, and mastered high-temperature processing, but added that the means and mechanism by which they produced these artifacts with carbon-nanotubes is not widely explored.
“Black and red pottery ware associated with megalithic sites in southern India continues into Keeladi dated back to 6th century BCE. The fine black and red effect was achieved by high temperature firing temperatures at about 1100 degrees in the presence of carbon-rich matter and iron-rich red soils,” Ms. Srinivasan said.
“They do not look like normal pots, these have glazed finishes, and are made of high-quality clay,” Mr. Rajavelu added.
He said these earthenwares were likely used by the “sophisticated people of the time”, adding that “a lot of the shards” have been found in Keeladi, “some dating back even as early as 900 BCE”.
“We have known for a long time that in iron smelting and manufacture, India was a world leader at the time. Even the Sangam ancient Tamil literature has noted about steel manufacture,” Mr. Rajavelu said.
“The technological skills of the Tamils in high-temperature manipulation of carbonaceous matter to make ultra-high carbon crucible steel known as wootz by about the mid to late centuries BCE was also reported by us, while carbon nanotubes were reported in medieval patterned ‘Damascus’ blades forged from such steel,” Ms. Srinivasan explained.
It is worth mentioning that Damascus steel was a remarkable feat of engineering. The metal was derived from wootz, a type of steel originating in India that is unusually rich in carbon.
Written by Conny Waters - AncientPages.com Staff Writer
