Ultra-Strong Nanotube Composites

TheMatt writes "In a story that makes you say "Cool!", Nicholas Kotov and co-workers have created a nanotube composite material six times stronger than carbon-fiber composites. Their final product is a crosslinked material which appears to be just as strong as silicon carbide and tantalum carbide!"

Comments

Re:No big uses soon...

[Drishmung]

'strong' is a much overused word, and pretty meaningless without significant qualification. Which is stronger: Balsa wood or Teak? OK, so when was the last time you made a model plane out of teak then?

Materials have the following attributes (and others of course):

• brittle/tough (glass vs steel)
• elastic/inelastic (aka stiffness)
• isotropic/anisotrpic
• density
• tempera ture stability
• chemical stability (resistance to corrosion)
• cost of raw material
• cost of manufacture
• hardness

Now, stiffness is one of the important ones. High Young's modulus (stiffness) good, low Young's modulus bad. Stiff and light is better; stiff, light and tough really attracts attention.

For a very readable introduction to this, I recommend The New Science of Strong Materials (or why you don't fall through the floor) by J.E. Gordon, also his Structures.

All the data you can't understand

[mstorer3772]

(or at least, "data *I* can't understand) can be found by following the "references" link at the bottome of the linked page.

It lead me to a nature.com, where, after registering with them (and opting out of EVERYTHING, which was easy), I read the Far More Technical nature article. It went way over my head.

WAY over:

"
The mechanical properties of the layered composites were tested on a custom-made thin-film tensile strength tester (McAllister) recording the displacement and applied force by using pieces cut from ((PEI/PAA)(PEI/SWNT)5)6 and ((PEI/PAA)(PEI/SWNT)5)8 freestanding films. The tester was calibrated on similar pieces made from cellulose acetate membranes and nylon threads. ((PEI/PAA)(PEI/SWNT)5)6 and ((PEI/PAA)(PEI/SWNT)5)8 samples had an average thickness, measured by TEM, of 0.75 and 1.0 m respectively.Their typical stress ( ä) versus strain ( å) curves differed quite markedly from stretching curves seen previously for SWNT composites10 and for LBL films made solely from polyelectrolytes, (PEI/PAA)40, obtained by the same assembly procedure (Fig. 4b). They displayed a characteristic wave-like pattern,a gradual increase of the d ä/d åderivative, and the complete absence of the plateau region for high strains corresponding to plastic deformations (Fig. 4a).The latter correlates well with the enhanced connectivity of SWNT with the polymer matrix (Fig. 2).
"

And that's the relatively clear stuff. I could actually follow some of it. Yow!

Re:All the data you can't understand

[florescent_beige]

The notation they are using is (resin-type/fiber-type)subscript-number-of-layers so ((PEI/PAA)(PEI/SWNT)5)8 means one layer of polyethyleneimine and polyacrylic acid followed by 5 layers of PEI and Single Wall Nano Tubes with the whole shebang repeated 8 times for a total of 48 layers.

Checking out the stress-strain curves, the peak is around 160 MPa. A typical modern graphite composite might give you 4 or 5 times higher than that. It just goes to show that high fiber properties are just a portion of the final composite strength.

Another thing I notice about the stress strain curves is the non-linearity. It looks like there is some internal damage maybe happening in the material before failure. This is a concern for repeated loading (fatigue).

Re:Flexibility? Tech usefulness?

[Sir Holo]

Anybody have any more information or links that explain how flexible this new material is?

Yup. If the nanotubes are chemically bonded to the matrix, as the article suggests, and it is comprised of 50% nanotubes, it would be extremely stiff. Far stiffer than any carbon fiber composite.

As far as flexibility of a physical shape (thread, cable) goes, anything is flexible if it is thin enough that opposite faces don't develop significant compressive/tensile stresses on bending. This is one reason why most cables are a bundle of smaller wires/threads. (Reliability is another issue, since if one goes it doesn't take the others out with it, as would happen if a cable was a solid piece of material (e.g., metal)). You can bend a multifilament line easily, whereas a solid cable of the same diameter would either be too stiff to bend easily, or would break or permanently deform as a result of the bending.

So, tethers or cables made from these nanocomposites would most likely be multifilament, making them flexible enough to be spooled easily, while still being very strong.