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.

It is believed that Damascus blades were

forged directly from small cakes of steel (named

thermomechanical treatment of forging

and annealing was applied to these cakes

to refine the steel to its exceptional quality.

However, European bladesmiths were unable

to replicate the process, and its secret was lost

at about the end of the eighteenth century. It

was unclear how medieval blacksmiths would

have overcome the inherent brittleness of the

as cohenite) that form in steel with a carbon

characteristic banding could have arisen from

these plates.

Mechanical processing at the appropriate

temperature can cause the steel’s microstructure

to become fine-grained, and superplastic

Small additions of the elements vanadium,

chromium, manganese, cobalt, nickel and

others are known to facilitate the formation

of cementite bands during thermal cycling at

temperatures below the cementite formation

Damascene steel contains rare-earth elements

and shows evidence of cementite nanowires in

Using high-resolution transmission electron

microscopy, we have now also detected

carbon nanotubes in a specimen taken from

a genuine Damascus sabre (sabre no.10 (ref.

6); sample kindly provided by E. J. Kläy of

Berne Historical Museum, Switzerland)

produced by the famous blacksmith Assad

Ullah in the seventeenth century. Its microstructure

but the nanotubes only become apparent

(Fig. 1) after dissolution of the sample in

hydrochloric acid (for methods, see supplementary

information). Some remnants

(Fig. 1c) show evidence of incompletely dissolved

these wires could have been encapsulated

well as from hydrocarbons inside micropores

that our finding could link the distinctive

banding seen in Damascus blades with ‘impurities’

optimizing their blade-treatment procedure,

craftsmen ended up making nanotubes more

than 400 years ago.

According to an early report on Indian

and ores taken from particular mines in India.

The diminishing supply of some of these ores

during the eighteenth century may have

prevented bladesmiths, who would not have

been aware of the importance of these alloying

elements, from practising their ancient

recipes.

Thermal cycling and cyclic forging cause

catalytic elements to segregate gradually into

These elements may give rise to the growth

of carbon nanotubes, which in turn initiate

formation of cementite nanowires and coarse

cementite particles. As the nanoscale structure

of Damascus steel emerges, a refined

inter pretation of its remarkable mechanical

properties should become possible.

M. Reibold*†, P. Paufler*, A. A. Levin*,

W. Kochmann‡, N. Pätzke*, D. C. Meyer*

*Institut fur Strukturphysik, †Triebenberg

Laboratory, Technische Universität Dresden,

01062 Dresden, Germany

e-mail: paufler@physik.tu-dresden.de

‡Krüllsstrasse 4b, 06766 Wolfen, Germany

5. Reibold, M., Levin, A. A., Meyer, D. C., Paufler, P. &

17–20 (2004).

109–115 (2006).

Received 24 July; accepted 25 October 2006.

Carbon nanotubes in an ancient Damascus sabre

a

b

c

(ref. 12), as indicated by the Fourier transforms

of cementite nanowires encapsulated by carbon

nanotubes, which prevent the wires from

dissolving in acid. Scale bar, 5 nm. The fringe

spacing of the wire is 0.635 nm, taken from the

Fourier transform (inset), and is attributed to

the (010) lattice planes of cementite.