The steel of Damascus blades, which were first encountered by the Crusaders when fighting against Muslims, had features not found in European steels--a characteristic wavy banding pattern known as damask, extraordinary mechanical properties, and an exceptionally sharp cutting edge. Here we use high-resolution transmission electron microscopy to examine a sample of Damascus sabre steel from the seventeenth century and find that it contains carbon nanotubes as well as cementite nanowires. This microstructure may offer insight into the beautiful banding pattern of the ultrahigh-carbon steel created from an ancient recipe that was lost long ago.

The surface and cross-section of a genuine Damascus sword was characterised by means of wide-angle X-ray scattering techniques complemented by optical and transmisssion electron microscopy. Position-resolved Xray phase analysis revealed that, unlike ferrite and martensite, the distribution of cementite is inhomogeneous in different spatial zones parallel to the cutting edge of the blade. For the first time a quantitative X-ray phase and texture analysis was made possible by averaging all spatial zones of the surface and the cross-section of the sword and applying the Rietveld method with code TOPAS. Differences concerning texture and structure characteristics of ferrite, martensite and cementite are discussed. More evidence for the structure of cementite nanowires is supplied.

Comparison of the structure of ancient Damascene steel blades at nanoscale with more recent ones -all made using crucible (wootz) technology and exhibiting ultra-high carbon content -showed for the first time a common feature. Despite different microstructures, colonies of wire-and tube-like particles with diameters of 40-50 nm have been observed with the aid of high-resolution transmission electron microscopy. Crystalline Fe 3 C is the main phase forming those particles covered in numerous cases by a tube-like layer. These tubes were also found in an empty or partly -covered filled variant. To assess the strengthening capacity of cementite various models were compared. Dispersion strengthening seems the most efficient. Cutting edge qualities may be related to surface corrugations due to nanoparticles. Dedicated to Prof. Wolfgang Neumann on the occasion of his 65th birthday

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