Discovery of Nanotubes in Ancient Damascus Steel

Using high-resolution electron microscopy, we have found in a sample of Damascus sabres from the 17(th) century both cementite nanowires and carbon nanotubes. These might be the missing link between the banding and ancient recipes to make that ultrahigh carbon steel. The sample considered belonged to the wootz-type of Damascus steel which is fundamentally different from welded Damast. The nanotubes have only been revealed after dissolution of the sample in hydrochloric acid. Some remnants showed not yet completely dissolved cementite nanowires, suggesting that these wires were encapsulated by carbon nanotubes. Only recently. considerable progress has been achieved in reproducing the process of making the characteristic pattern of wootz. We propose a connection between impurity segregation, nanotube formation, nanotube filling with cementite, cementite wire growth, and formation of large cementite particles. Needless to say that the presence of a nanostructure will have ail impact upon the mechanical properties.