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Polyyne said to be 40 times harder than diamond

Work in Israel reported in the Jerusalem Post: “Scientists from Bar-Ilan University and the Technion-Israel Institute of Technology say that using nanotechnology, they have discovered a material 40 times harder. Professors Eli Altus, Harold Basch and Shmaryahu Hoz, with doctoral student Lior Itzhaki have published their findings in the Internet edition of the world’s most influential chemistry journal, [Angewandte] Chemie.

“If nanotechnology can be applied to create tiny machines, scientists must first understand the connection between the quantum mechanical behavior of atoms and molecules and the classical world of mechanical engineering. For example, a miniature vacuum cleaner might be built to travel through human blood vessels and clean out excessive cholesterol. Yet it is unknown whether its tiny mechanical arm would be strong enough to remove the fatty plaques…

“The team broke the world hardness record by combining quantum mechanics, chemistry and mechanical engineering. They synthesized polyyne, a superhard molecular rod comprised of acetylene units – that resists 40 times more longitudinal compression than a diamond. Ironically, these glittery gems are comprised from the element carbon and have the weakest type of chemical bonds, while polyyne has the strongest bonds in carbon chemistry.”

Sounds great, although the claim that we can’t tell whether a tiny mechanical arm would be strong enough doesn’t seem quite right. We should be able to calculate the strength and stiffness of such an arm today, with different answers depending on the design.—Christine

7 Responses to “Polyyne said to be 40 times harder than diamond”

  1. Andrey Khavryuchenko Says:

    Anything designed from polyyne would be very chemically active that would render impossible any attempt to build any nanomechanical device around it.

  2. Andrey Khavryuchenko Says:

    Also the chemical reactivity strongly depends on spin state. This is directly shown by our calculations of highly conjugated systems like graphite. Also this is supported by experiment – everyone who seen graphite STM images know what I’m speaking about.

  3. Nanoman Says:

    But can we make MACROSCOPIC STRUCTURES FROM POLYYNE that are harder than diamond and stronger than steel? Like a “polyyne polymer alloy” that can be used for car body panels, I Beams, and more?

  4. Andrey Khavryuchenko Says:

    Nanoman: no, unless you want them to self-burn or explode.

  5. Petrus Says:

    You can conceive an element of polyyne for structural resistance covered with say a diamond layer for insulation. Possibly improved with a softer element to interface the two in case of different expansions and contractions – one can envision the diamond in scales “floating” on a binder over the polyyne.

    You still wouldn’t want to have the thing snap, though, as then you’d have your little firework.

  6. Andrey Khavryuchenko Says:

    Petrus: no, you can’t.

    That’s a chemistry, not a physics. Thus no “different expansions and contractions”. There’s nothing but nuclea and electrons, the “bond” are just an abstraction.

    So, if you’d someway cover polyyne with a diamondoid structure you will get either just less reactive compound or a diamondoid structure with defects.

  7. Autymn D. C. Says:

    Interfaces are interfaces no matter how small they are, Andrey.

    But these scientists make the common mistake of confusere stiffness for hardness–uniaxial stiffness especially is irrelevant to the question of hardness. Moreover, you can chete other materials into like stiffness greater than diamonds if you make unifilament anything with alternant, a’tweenlocking bond orders. But keep them in a cold, dark, dry, lull stead.

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