New studies of Damascus swords are revealing that the legendary blades contain nanowires, carbon nanotubes, and other extremely small, intricate structures that might explain their unique features.
Damascus swords, first made in the eighth century A.D., are renowned for their complex surface patterns and sharpness. According to legend, the blades can cut a piece of silk in half as it falls to the ground and maintain their edge after cleaving through stone, metal, or even other swords.
But since the techniques for making these swords have been lost for hundreds of years, no one is sure exactly why these swords are so exceptional.
Now studies of the swords' molecular structure are uncovering the tiny structures that may explain these properties.
Peter Paufler, a crystallographer at Technical University in Dresden, Germany, and his colleagues had previously found tiny nanowires and nanotubes when they used an electron microscope to examine samples from a Damascus blade made in the 17th century.
Today in the journal Nature, the teams reports that it has also discovered carbon nanotubes in the sword—the first nanotubes ever found in steel, Paufler says.
The nanotubes, which are remarkably strong, run through the blade's softer steel, likely making it more resilient. (Related: "Nano-Switches Could Yield Even Smaller Gadgets" [August 16, 2005].)
"It is a general principle of nature," Paufler said. "Materials that are softer, you can strengthen by including harder wires."
Secret Techniques
Some of the nanowires Paufler and his team had previously found were made of an extremely hard iron-based mineral called cementite.
In the new research, the team discovered that carbon nanotubes encase some cementite nanowires, protecting them.
These nanotube-nanowire bundles may give the swords their special properties, Paufler says.
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