Boasting the highest strength of any material ever discovered, as well as a host of other properties, carbon nanotubes have been a hot topic in nanotechnology for a while now. But researchers last month discovered a new form of carbon tubes. Being bigger than traditional carbon nanotubes, this new material falls under the category of colossal carbon tubes (CCTs), but with diameters on the order of tens of microns, they are still very tiny.
What makes these new CCTs interesting compared with carbon nanotubes or other carbon fibers is their spongy nature which not only makes them light, but strong and tough, too.
Properties and Applications
The structure of these tubes is porous which makes them extremely light – about 20 times lighter than conventional carbon fibers. A sugar cube-sized lump of the material would weigh as much as one tenth of a paper clip, and with performance that might surpass Kevlar, it could be used to make the next generation of ultra-light body armor, other textiles, or super-strong cables (space elevator, anyone?). The porous structure also provides high conductivity meaning this material could have electronic applications, as well.
While not nearly as strong as the strongest carbon nanotubes, the structures are significantly stronger than other carbon fibers. But while strength may be the sexiest of material properties, perhaps just as important or more important in certain applications is toughness. The new spongy CCTs show a higher toughness than other carbon tubes and fibers. Strength and toughness are sometimes thought to mean the same thing, so let me briefly explain the difference.
Strength vs. Toughness
Strength relates to the amount of force needed to cause permanent deformation, while toughness is defined by the amount of energy a material can absorb before fracturing. I know those sounds similar, and that is why they are often confused, but, though related to each other, they are different. Often, there is a trade off between the two properties.
For example, think of a piece of chalk. Chalk has high strength, but low toughness. Try to pull on the two ends of a piece of chalk without twisting or bending it and you are going to have to pull really hard to break it in two (if you even can break it). Chalk is strong. But if you were to bend if like you were snapping a twig or pencil, it would break really easily. Chalk is brittle (or the opposite of tough).
Chalk is brittle because it cannot absorb much energy (or deform) before breaking. Alternatively, rubber is usually very tough. You can bend, twist, or otherwise deform it a great deal before it breaks. Such a material is described as being ductile.
The reason toughness can be so important is because of the nature of failure of a tough versus brittle material. We could, for example, decide to build bridges out of ceramics because ceramics are very strong (in some cases stronger than metal alloys), but ceramics are brittle (not tough) so if a component of the bridge fails it will fail “catastrophically”, as they say. Instead, we build bridges out of steel. Steel is relatively strong and tough, so if it starts to fail, it will fail slowly by deforming and the problem can be spotted long before anything disastrous happens.
Given the trade off between toughness and strength, new materials that have both high strength and toughness are highly sought after. As mentioned above, the spongy CCTs have good ductility as well as high strength, and that is a valuable combination, especially considering they are extremely light-weight.
Image from: Peng, H. et al. Phys. Rev. Lett. 101, 145501 (2008)
Been listening to this one a lot, pretty much the whole way through.
This novel was published after the Chilean-Mexican author's death, and I'm not even sure if it was entirely finished or not. It is broken up into five parts which, while connected, stand pretty much on there own. I have not yet made it to the grim part about the murders of hundreds of women in Mexico, so I have so far found it enjoyable and even funny despite some dark underpinnings. It's had a ton of critical praise, and I like it much more than my last foray into the violent novel genre: Blood Meridian.
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I love having friends who know a lot about stuff I know nothing about. Thanks for the education!
You mean you kept reading when it got all nerdy? Wow, thanks. I’m glad I have friends who read this stuff…or at least one friend.
…and by “when it go all nerdy” I mean half way through the post title.
What about the applications for generating electricity through wind? It would seem wind mills would rely heavily on a material’s toughness, and improve efficiency based on their extremely light weight.
Nathan -
Sounds like a great idea. You could probably think of lots of useful applications where a strong, tough, and light-weight material would be desired. It is interesting that the paper and subsequent news coverage focuses primarily on textiles. The authors write that the physical dimensions of the tubes are similar to cotton fibers, but it could also be that they began this work trying to make stronger textiles for body armor, an application they mention more than once.
However, at the end of the paper the authors also discuss possible uses for “light-weight, high strength composite structures”, as well as “in situ self-healing composite structures, medical devices to deliver/release multiple drugs simultaneously, and microelectromechanical systems, to name only a few.”
The biomedical applications sounds promising, as researchers are always exploring small, porous structures that could be used for drug delivery or scaffolding for tissue engineering. For instance, due to their size, shape, and structure, carbon nanotubes are often talked about as possible vehicles for drug delivery or otherwise treating illnesses. But one of the many problems is that they are very toxic for humans. So the toxicity of these new structures would need to be investigated, as well the structures ability to be functionalized, or attached with, drugs or molecules necessary for these biomedical applications.
I know this is a re-post, but I just want to say that I love reading your sciencey blogs. It makes me feel smart by proxy.
I never expected to make someone feel smart by reading my blog, but thanks.
I would like to write more posts like this, but I often put them off until they feel less relevant. But since you like them, I’ll try harder. You just continue making me feel cultured by proxy.