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Thursday, July 17, 2008

Strongest Material Ever Tested

Graphene, praised for its electrical properties, has been proven the strongest known material.

By Katherine Bourzac
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Strongest material: By depressing a sharp diamond probe into graphene until it broke, researchers established that the material is the strongest ever tested. This image, an illustration, shows the atomic structure of graphene, which is one atom thick and made up of carbon and hydrogen arranged in a chicken-wire-like mesh.
Credit: Jeffrey Kysar, Columbia University

Materials scientists have been singing graphene's praises since it was first isolated in 2005. The one-atom-thick sheets of carbon conduct electrons better than silicon and have been made into fast, low-power transistors. Now, for the first time, researchers have measured the intrinsic strength of graphene, and they've confirmed it to be the strongest material ever tested. The finding provides good evidence that graphene transistors could take the heat in future ultrafast microprocessors.

Jeffrey Kysar and James Hone, mechanical-engineering professors at Columbia University, tested graphene's strength at the atomic level by measuring the force that it took to break it. They carved one-micrometer-wide holes into a silicon wafer, placed a perfect sample of graphene over each hole, and then indented the graphene with a sharp probe made of diamond. Such measurements had never been taken before because they must be performed on perfect samples of graphene, with no tears or missing atoms, say Kysar and Hone.

Hone compares his test to stretching a piece of plastic wrap over the top of a coffee cup, and measuring the force that it takes to puncture it with a pencil. If he could get a large enough piece of the material to lay over the top of a coffee cup, he says, graphene would be strong enough to support the weight of a car balanced atop the pencil.

It's unlikely that graphene's incredible strength will be put to use in such a task. At the macroscopic level of coffee cups and cars, "any material will be full of cracks and flaws," says Kysar. It's at the level of such cracks and flaws that airplane wings and bridge supports fail. "Only a tiny sample can be perfect and superstrong," says Hone.
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carbon nanotubes graphene materials transistors

Comments

  • Graphene strength
    dib on 07/18/2008 at 3:29 AM
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    It's just a 1-atom slice thru a diamond, yes? You'd expect it to be strong, no?

    dib
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  • Diamond vs. Graphene
    Simon Shine on 07/18/2008 at 4:38 AM
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    Graphene isn't a one-slice through diamond, although both are very strong carbon bonds. Graphene is one flat layer of hexagon-shaped bonds (like in a bee hive) whereas diamonds follow a tetrahedal pattern (three-cornered pyramid).

    One can easier imagine why diamonds should be strong because there are no weak angles - it all consists of perfect triangles (minus impurities).

    But why exactly graphene is so strong is beyond me.
    Rate this comment: 12345
  • Actually.
    Symptom on 07/18/2008 at 5:41 AM
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    Actually The strongest metal known to man is Dragonforce.


    Herman Li is a god.

    Look it up, you will understand... silly scientists.
    Rate this comment: 12345
    • Re: Actually.
      stradric on 07/18/2008 at 9:59 AM
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      Heh, Dragonforce is awesome, but Graphene is not a metal...  Sorry to ruin your joke.
      Rate this comment: 12345
  • Define strength
    deltapapamike on 07/18/2008 at 6:59 AM
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    The article didn't mention exactly what material property was measured by the researchers, or what was meant by "strength."  Yield tensile stress? Ultimate tensile stress? Elastic modulus?  How about a numerical value for the quantity?

    As a mono-atomic sheet, I'm guessing it's not one of the strongest materials in compression.
    Rate this comment: 12345
    • Re: Define strength
      stradric on 07/18/2008 at 10:02 AM
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      I'm not familiar with the exact definition of those metrics, but maybe you can determine what they mean by their analogy of a car balanced atop a pencil balanced on a sheet of graphene stretched over the opening of a coffee cup.
      Rate this comment: 12345
    • Re: Define strength
      maverick on 07/19/2008 at 6:20 PM
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      Given by the description, it appears they have conducted something akin to a hardness test (google it).  What they are measuring is a relative metric--how much energy it takes to break the material.  From this they can compare it to other known thin film materials and interpolate the strength--and other properties--of graphene.  This test just gives researchers and manufacturers a ballpark for expected strength of the material.  Manufacturers will probably not be making "perfect" graphene anyways. 
      Rate this comment: 12345
  • Applications of Graphene
    mkogrady on 07/18/2008 at 12:43 PM
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    Aside from balancing cars on pencils on top of coffee cups - what are some practical applications of this stuff?

    If's it made of carbon atoms, can we use it to convert GHH's to a super strong product, and use it to sequester Co2 indefintely?

    Can we make car bumpers out of it? How about beehives due to it's crystalin structure?

    Just Curious


    ****

    Scratch that....I just read page two...
    Rate this comment: 12345
  • hard numbers
    Katherine Bourzac on 07/18/2008 at 2:33 PM    		 Technology Review TR Staff
    Materials Science Editor
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    The researchers measured graphene's intrinsic strength and elastic properties. Those readers who want the numbers can find them in this Science paper: http://www.sciencemag.org/cgi/content/abstract/321/5887/385
    Rate this comment: 12345
  • Space Elevator Tethers
    RichC on 07/20/2008 at 1:29 PM
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    If graphene is stronger than nanotubes, it can be a candidate material for space elevator tethers.  Made into a hose shape, it could be used to squirt air into space at modest rates, enlarging the cooling area, so cooled air comes back down from space.  So the carbon is sequestered, the space elevator makes space travel cheap, and global warming is cooled all in one project. 
    Rate this comment: 12345
    • Re: Space Elevator Tethers
      mkogrady on 07/21/2008 at 12:42 PM
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      Wouldn't the air escaping from Earth make a farting sound and cause the planet to fly around erratically - just like toy balloons?


      (Sorry - that image just got stuck in my head (I couldn't resist))
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  • strongest
    gwink on 07/21/2008 at 10:03 AM
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    Is it as strong as spiderweb silk?  Now that's a well-designed material & production facility.  Hopefully with lots of smart hard-working people we can match it someday.
    Rate this comment: 12345
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