Dr. Çetiner’s Blogs (Dr. Beytullah Gültekin Çetiner)

The Damascus swords of the Middle East were legendarily sharp, strong and flexible. Now, an analysis of one of these weapons under an electron microscope reveals that the key to its properties is nanotechnology, inadvertently used by blacksmiths centuries before modern science.

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.

Figure Nanotubes 

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.

The bundles run parallel to the blade’s surface and may help larger particles of cementite arrange in layers. These hard layers, which have softer steel in between, could help explain how the steel remains strong yet flexible.

This combination of strength and flexibility makes the steel ideal for forging swords.

The blades were generally made from metal ingots prepared in India using special recipes, which probably put just the right amount of carbon and other impurities into the iron (India map).

By following these recipes and following specific forging techniques, “craftsmen ended up making nanotubes more than 400 years ago,” Paufler and his colleagues write.

When these blades were nearly finished, blacksmiths would etch them with acid. This brought out the wavy light and dark lines that make Damascus swords easy to recognize.

But it could also give the swords their sharpness, Paufler says. Because carbon nanotubes are resistant to acid, they would protect the nanowires, he theorizes.

After etching, many of these nanostructures could stick out from the blade’s edge, giving it tiny saw-like teeth.

Skeptical Smiths

The techniques for making the steel were lost around A.D. 1700. But many researchers are studying how to recreate the blades—even though metallurgical experts warn that the blades, though exceptional for their time, are far outperformed by modern steels.

While some scientists have claimed success, others dispute that the reproductions are truly the same as the originals.

And many experts doubt that the new findings will clear things up.

John Verhoeven, a metallurgist at Iowa State University at Ames who has worked on reproducing the Damascus sword-making techniques, is skeptical that Paufler and his colleagues have cracked the secret of Damascus blades.

“I don’t think that [the nanowires] are anything unusual,” Verhoeven said. “I think those structures would be found in normal steels.”

The Damascus sword is also an example of how unexpected nanosize structures can show up in materials—and sometimes give them surprising properties, experts say.

References

• National Geographics News http://news.nationalgeographic.com/news/2006/11/061116-nanotech-swords.html
• http://en.wikipedia.org/wiki/Carbon_nanotube 
• http://en.wikipedia.org/wiki/Damascus_steel 

Carbon nanotubes (CNTs) are an allotrope of carbon. They take the form of cylindrical carbon molecules and have novel properties that make them potentially useful in a wide variety of applications in nanotechnology, electronics, optics and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized.

Nanotubes are members of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 50,000 times smaller than the width of a human hair), while they can be up to several millimeters in length. There are two main types of nanotubes: single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).

The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. Nanotubes are composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamond, provides the molecules with their unique strength. Nanotubes naturally align themselves into “ropes” held together by Van der Waals forces.

Damascus Steel

Damascus steel is a steel used in Middle Eastern swordmaking from about 1100 to 1700 AD. Damascus swords were of legendary sharpness and strength, and were apocryphally claimed to be able to cut through more “ordinary” European swords and even rock. The technique for making Damascus steel remains a mystery even with the presences of numerous well-preserved examples. Recent research into the structure and composition of the steel by a Dresden scientist claims that the strength of the steel was a result of carbon nanotubes and carbide nanowires present in the structure of the forged metal.

Damascus swords often had an obvious patterned texture on their surface. Several other steelmaking techniques also result in patterned surfaces, and have often been sold as Damascus steel, Damascened steel and sometimes watered steel. The most common technique for producing these materials is the pattern welding, which is today widely used for custom knife making. Skilled swordsmiths can manipulate the patterns to mimic the complex designs found in the surface of the original, medieval Damascus steel.

Another theory behind the hardness of Damascus steel is that the steel contains a small amount of vanadium, which would theoretically strengthen the blade.

Manufacture of Damascus Steel
The original Damascus steel swords may have been made in the vicinity of Damascus, Syria, in the period from 900 AD to as late as 1750 AD. Damascus steel is a type of steel alloy that is both hard and flexible, a combination that made it ideal for the building of swords. It is said that when Damascus-made swords were first encountered by Europeans during the Crusades it garnered an almost mythical reputation—a Damascus steel blade was said to be able to cut a piece of silk in half as it fell to the ground, as well as being able to chop through normal blades, or even rock, without losing its sharp edge. Recent metallurgical experiments, based on microscopic studies of preserved Damascus-steel blades, have claimed to reproduce a very similar steel via possible reconstructions of the historical process.

When forming a batch of steel, impurities are added to control the properties of the resulting alloy. In general, notably during the era of Damascus steel, one could produce an alloy that was hard and brittle at one extreme by adding up to 2% carbon, or soft and malleable at the other, with about 0.5% carbon. The problem for a swordsmith is that the best steel should be both hard and malleable — hard to hold an edge once sharpened, but malleable so it would not break when hitting other metal in combat. This was not possible with normal processes.

Metalsmiths in India and Sri Lanka perhaps as early as 300 BC developed a new technique known as wootz steel that produced a high-carbon steel of unusually high purity. Glass was added to a mixture of iron and charcoal and then heated. The glass would act as a flux and bind to other impurities in the mixture, allowing them to rise to the surface and leave a more pure steel when the mixture cooled. Thousands of steel making sites were found in Samanalawewa area in Sri Lanka that made high carbon steel (Juleff, 1996). These steel making furnaces were built facing western monsoon winds and wind turbulance and suction was used to create heat in the furnace. Steel making sites in Sri Lanka have been dated to 300 BC using carbon dating technology. The technique propagated very slowly through the world, reaching modern-day Turkmenistan and Uzbekistan around 900 AD, and then the Middle East around 1000 AD.

This process was further refined in the middle east, either using locally produced steels, or by re-working wootz purchased from India. The exact process remains unknown, but allowed carbides to precipitate out as micro particles arranged in sheets or bands within the body of a blade. The carbides are far harder than the surrounding low carbon steel, allowing the swordsmith to make an edge which would cut hard materials with the precipitated carbides, while the bands of softer steel allowed the sword as a whole to remain tough and flexible.

The banded carbide precipitates appear in the blade as a swirling pattern. By manipulating the ingot of steel in a certain way during forging, various intentional patterns could be induced in the steel. The most common of these was a pattern of lateral bands, often called ‘Mohammed’s Ladder’, most likely formed by cutting or forging notches into the surface of the ingot, then forging it into the blade shape (this is the method Pendray (below) used to reproduce the pattern). The notches resulted in different degrees of work hardening between top and bottom, and thus controlled the size of the carbide particles in the surface at those areas, and thus the appearance of the bands.

Reference: Wikipedia

There was a seminar today about Nanotechnology and its applications given by professor of Illunois University. The seminar was organized by Industrial Engineering Department of King Abdulaziz University after a conference at the Conference Hall on 9th January, 2007.

Many students from Engineering College (mostly from Industrial Engineering Department) participated and asked very good questions. I will not go in to detail about the seminar. However, I will mention the most important part which seemed very interesting to me. This point was raised by one of the panelists. It was very short but interesting idea.

It is about the Damascus Swords or Damascus Steel. As we know from the history, the Damascus Swords are very famous with sharpness and hardness as well as flexibility. We also know that Salahaddin Ayyubi won the battle against crusading Christian knights who were reclaiming Jerusalem from the Muslims.  These damascus swords were containing nanotubes or nanotechnology according to the claim in seminar. I have made a quick search and found interesting articles about these Damascus Swords using Nanotechnology.

I hope you will find the compilation of articles useful. You can read from Nanotechnology used in Damascus Swords

Nanotechnology is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale smaller than one micrometre, as well as the fabrication of devices on this same length scale. It is a highly multidisciplinary field, drawing from fields such as colloidal science, device physics, and supramolecular chemistry. Much speculation exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research.

Despite the apparent simplicity of this definition, nanotechnology actually encompasses diverse lines of inquiry. Nanotechnology cuts across many disciplines, including colloidal science, chemistry, applied physics, biology. It could variously be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more modern term. Two main approaches are used in nanotechnology: one is a “bottom-up” approach where materials and devices are built from molecular components which assemble themselves chemically using principles of molecular recognition; the other being a “top-down” approach where nano-objects are constructed from larger entities without atomic-level control.

The impetus for nanotechnology has stemmed from a renewed interest in colloidal science, coupled with a new generation of analytical tools such as the atomic force microscope (AFM) and the scanning tunneling microscope (STM). Combined with refined processes such as electron beam lithography, these instruments allow the deliberate manipulation of nanostructures, and in turn led to the observation of novel phenomena. Nanotechnology is also an umbrella description of emerging technological developments associated with sub-microscopic dimensions. Despite the great promise of numerous nanotechnologies such as quantum dots and nanotubes, real applications that have moved out of the lab and into the marketplace have mainly utilized the advantages of colloidal nanoparticles in bulk form, such as suntan lotion, cosmetics, protective coatings, and stain resistant clothing.