Thursday, July 1, 2010

Damascus Sword : Nanotech Used 2000 Years Ago to Make History’s Sharpest Swords


the Sharpest Sword in the World is Damascus swords — sharp enough to slice a falling piece of silk in half, strong enough to split stones without dulling — owe their legendary qualities to carbon nanotubes, says chemist and Nobel laureate Robert Curl.

The blades used so-called wootz steel, smelted with a technique developed 2000 years ago in India, where craftsmen added wood and other organic debris to their furnaces. The resulting carbon-laced steel, hard but flexible, was soon celebrated across the ancient world.

Perhaps because the tungsten-rich ores used to make wootz steel ran out, the making of Damascus blades stopped during the 18th century. The techniques vanished from metalsmith lore. Modern metallurgists tried again and again to recreate the blades, but without success. Then, a little more than a year ago, German scientists explained their difficulty: wootz steel was full of carbon nanotubes, a miracle material "discovered" in 1991. Some chemists argued that regular steel possesses these nanotubes, but Curl, speaking at the just-concluded Indian Science Congress, sides with the Germans.

Cyberpunk pioneer turned history junky Neal Stephenson described the manufacture of wootz steel in The Confusion, the second volume of his frustrating, exhilirating and historical awe-inspiring Baroque Cycle. As luck would have it, much of The Confusion is available on Google Books:

They moved on to a pile of crucibles that had been removed from the furnace and allowed to cool. A boy picked these up one at a time, tossing them from hand to hand because they were still too hot to hold, and dashed them against a flat stone to shatter the clay crucible. What remained among those smoking pot-shards was a hemisphere of spongy grey metal.
"The egg!" exclaimed Enoch.

A smith picked up each egg with a pair of tongs, set it on an anvil, and struck it at once with a a hammer, then examined it carefully. Eggs that dented were tossed away on a discard-heap. Some were so hard that the hammer left no mark on them — these were put into a hod that was eventually carried acrss the compound to another pit where an entirely different sort of clay was being mixed up, according to some arane recipe, by the stomping feet of Hindoo boys, while a village elder walked around the edge peering into it and occasionally tossing handfuls of mysterious powders into the mix. The eggs of metal were coated in thick jackets of this clay and then set aside to dry. The first clay had been red when wet and yellow when fired, but this stuff was grey, as if the clay itself were metalliferous.

Once the gray clay had dried around the eggs, these were carried to a different furnace to be heated — but only to a dull red heat. The difference became obvious to Jack only when the sun went down, and he could stand between the two furnaces and compare the glow of one with that of the other. Again, the firing continued for a long time. Again, the eggs that emerged were cooled slowly, over a period of days. Agin they were subjected to the test of the anvil — but with different results. For something about this second firing caused the steel egg to become more resilient. Still, most of them were not soft enough to be forged after a single firing in the gray clay, and had to be put through it again and again. But out of every batch, a few responded in just the right way to the hammer, and these were set aside. But not for long, because Persians and Armenians bought them up almost before they had hit the ground.

‘Indian craftsmen, artisans used nanotech 2000 yrs ago’ [The Hindu]

Image: Persian Carpet Guide

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