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January 20, 2009

Alan Windle Past Carbon Nanotube Work Suggests Recent Announcement Could be Huge


Carbon nanotube fiber on spindle from Alan Windle group. 2007 picture

The Times UK claims Alan Windle's team at Cambridge University has created the world’s strongest ribbon: a cylindrical strand of carbon that combines lightweight flexibility with incredible strength and has the potential to stretch vast distances. There may have been no advance or minimal advance from the Dec 7, 2008 European Spaceward presentation on the Cambridge carbon nanotubes.

UPDATE: Found the specifics. Strength 9 GPa in centimeter lengths which they are scaling to meter lengths and 10GPa in a few months and to industrial scale in a few years This material is 2.5 times stronger than Spectra 2000 (by strength/weight) and four times stronger than Kevlar.

Prof Alan Windle has claimed to have made the strongest ribbon of material ever.

This could mean material suitable for space elevators in 5 to 10 years.

Spectra 2000 fiber used in body armor and stronger than Kevlar has: Strength 3.5 GPa and Density: 0.97 g/c

Carbon nanotubes on a molecular scale or in small quantities have strength up to 70-200 GPa. 20 to 55 times stronger than Spectra 2000.

The new work is bringing the large scale strength of carbon nanotubes up to 2.5 to 10 GPa. From a little less strong than Spectra up to 3 times stronger.

What does it mean ?
- Better military and police armor.
- Better tethers for space (shorter versions of the space elevator)
- wider use of carbon nanotubes for reinforcing many things.
- When production volumes increase they can be used to make lighter cars and planes so that they are more fuel efficient.

Here is a review of announcements from Alan Windle's team from 2004 to 2008.

New Scientist Reported in 2004, Alan Windle's group had made 100 meter long carbon nanotube thread but the threads were not strong. If Alan Windle has made the world's strongest ribbon and these threads are still 100 meters long or more then this would be a monster breakthrough.

MIT Technology Review reported in 2007 that Alan Windle had made stronger carbon nanotubes stronger.

Alan Windle, a professor of materials science at the University of Cambridge, in England, made and tested the new nanotube fibers along with researchers at the Natick Soldier Research Development Center, in Massachusetts. Windle and his colleagues tugged on the nanotube fibers, finding that the weaker ones snapped at stresses around one gigapascal, making them comparable to steel, gram for gram.

The better-performing carbon-nanotube fibers broke at around six gigapascals, beating the strengths that manufacturers report for materials used in bullet-proof vests, such as Kevlar. These nanotube fibers matched the highest reported strengths for a couple of the strongest commercially available fibers, Zylon and Dyneema, also used in bullet-proof vests. A lone, extremely strong nanotube fiber was off the charts, reaching nine gigapascals of stress--far beyond any other reported material--before breaking. Earlier work with carbon nanotubes has produced fibers that withstand at most three gigapascals.


In 2008, Alan Windle was making 20 gigapascal strength carbon nanotubes but only for gauge length sections [less than one millimeter]

Both Nanocomp and Dr. Alan Windle’s group at the University of Cambridge are making some exciting materials by continuous-draw processes, and a number of other groups are working on some exciting other approaches such as spinning from nanotube forests grown on silicon wafers. [from 2008]


Nanowerk describes the Alan Windle continuous spin process from late 2007.

As in the proverb 'A chain is only as strong as its weakest link', the performance of a CNT fiber depends on the weak points along its length, caused by defects on its internal structure. The major challenge for materials engineers therefore is to develop a production process that avoids these defects and makes CNT fibers suitable for commercial applications.

"We have developed successful strategies to avoid particulate defects amongst the network of nanotube bundles forming the fibers" Dr. Marcelo S. Motta, a Research Associate in Windle's group, tells Nanowerk. "Recent improvements in our process have enabled us to spin continuously with iron contents down to 25 ppm. At present, these fibers are spun at a rate of 5–25 meters per minute, with diameters in the range 2–20 µm. Because they are so thin, a kilometer of fiber weighs much less than a gram."



From a European Spaceward Association presentation on Dec 7, 2008: At Cambridge University, we have recently introduced a method for the spinning of pure carbon nanotube fibres directly from the gas phase of a chemical vapour deposition reactor. The major benefit of this process is the ability to continuously collect the pure and uniform nanotubes as a transparent thin-film or as a high-performance fibre. While the best strength (2.5 N/tex) and stiffness (160 N/tex) promise competition for established carbon fibres, the maximum energy absorbed at fracture (up to 100 J/g) is considerably higher. When tested in small gauge lengths, and thus less sensitive to defects arisen from instabilities in the production line, these fibres show remarkable combination of tensile strengths (5-10 N/TEX), stiffness and toughness which makes them the strongest materials ever tested. In this presentation I will show in detail how these fibres are produced and discuss how their properties can still be significantly improved without the need to apply any extra additives or post-processing. These challenges will be set against the scaling-up plan already under development.


The Times UK claims Alan Windle's team at Cambridge University has created the world’s strongest ribbon: a cylindrical strand of carbon that combines lightweight flexibility with incredible strength and has the potential to stretch vast distances.

The Cambridge team is making about 1 gram of the high-tech material per day, enough to stretch to 18 miles in length. “We have Nasa on the phone asking for 144,000 miles of the stuff, but there is a difference between what can be achieved in a lab and on an industrial level,” says Alan Windle, professor of materials science at Cambridge University, who is anxious not to let the work get ahead of itself.

The Cambridge team have found a way of combining separate nanotubes into structures that bind to form longer strands.


How long is the carbon nanotube fiber ? could be 100 meters or longer
How strong is this carbon nanotube fiber ? Should be over 6 to 9 gigapascals which was the 2007 level. Windle still says that space elevator strength material is still 5-10 years away. So the new material could be in the 6 to 9 gigapascal (5-10 N/Tex) range if they have solved more of the defect issues. We will update when information becomes available. Awaiting definitive scientific paper or announcement with key metrics.

This could be a pretty monster development and the claim NASA is calling him would be correct if he has 100 meter + and 6-9 gigapascal strength material.


UPDATE: Found the specifics. Strength 9 GPa in centimeter lengths which they are scaling to meter lengths and 10GPa in a few months and to industrial scale in a few years This material is 2.5 times stronger than Spectra 2000 (by strength/weight) and four times stronger than Kevlar.

Spaceward has been tracking carbon nanotube bulk strength progress.

There are many "less than space elevator applications" for that kind of material.

Space Elevator blog also discusses this new information but also does not have specifics yet.





A previous abstract from a 2007 research paper "High-Performance Carbon Nanotube Fiber" with Windle as one of the writers.

BBC had coverage on Windle's work back in 2007

The fibre created in Cambridge is very strong, lightweight and good at absorbing energy in the form of fragments travelling at very high velocity.

Our fibre is up there with the existing high performance fibres such as Kevlar", said Professor Windle.

But he added: "We've seen bits that are much better than Kevlar in all respects".

A hydrocarbon feedstock, such as ethanol, is injected into the furnace along with a small amount of iron-based catalyst.

Inside the furnace, this feedstock is broken down into hydrogen and carbon. The carbon is then chemically "re-built" on particles of iron catalyst as long, thin-walled nanotubes.

To the eye, this "elastic smoke" looks a bit like an ever-expanding dark "sock".

To begin winding it up, a rod is inserted into the furnace from below to grab one end of the sock and yank it down. This stretches the sock into a filament that can be wound up continuously on a reel.

The researchers are currently seeking funds to investigate whether the method can be upgraded from a laboratory to an industrial process.

Cambridge Enterprise Limited, the commercialisation office of the University of Cambridge, filed an initial patent application in July 2003.

It has now granted a licence to Q-Flo Limited, a university spin-out company, which will exploit the technology.


Alan Windle's website at Cambridge University
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