Nanotechnology may not be as new as we like to think. At least, not if Peter Paufler and his colleagues at Dresden University are right, and carbon nanotubes are to be found in ancient Saracen sabres from Damascus.
The Damascene blades are made of a type of steel known as wootz, which was first made in India, possibly as early as 300 CE. Wootz steel became especially popular in the Middle East, where it became known as Damascus steel, and its high strength made it ideal for use in blades which possess an exceptionally sharp cutting edge. The original Damascus swords were made between around 500 CE and 1750 CE.
Paufler and his colleagues took electron-microscope images of an 18th century Damascus sword, and found that the steel has a microstructure of nanometre-scale tubes. These were revealed when a piece of the sword was dissolved in hydrochloric acid to remove wires of iron-carbide, or cementite, which give the steel its strength. The findings were reported recently in the journal Nature (subscription required).
Asked how the discovery came about, Paufler replied: “Seeking nanostructures was proposed by Werner Kochmann ten years ago. He convinced me to do it.” Kochmann is a bladesmith with whom Paufler intends to recreate the wootz process.
The suggestion is that high temperatures catalyse the growth of nanotubes from carbon in the burning wood of the forge, and these fill with cementite to produce the wires that give wootz its remarkable strength. But steel expert John Verhoeven of Iowa State University is not convinced: “It is my guess that the structures Peter is observing – nanowires and nanotubes – are probably present in the rod form of pearlite found in almost all high carbon steels.”
Pearlite is a mixture of the minerals cementite and ferrite.
Whether or not carbon nanotubes exist in wootz steel, nanoscale structures most certainly do, and it should be a fascinating exercise to recreate the long-lost process.
Article first published in Nanomaterials News. © 2006 Pira International – all rights reserved.