DailyDirt: Harder Than Diamond (But Not As Pretty Or Available)

from the urls-we-dig-up dept

Tue, Dec 8th 2015 5:00pm — Michael Ho

Diamond is a fascinating material. We haven't quite perfected how to make diamonds, so they're still rare -- and somewhat valuable, depending on the eye of the beholder. One aspect of diamond that everyone learns in school is that it is really, really hard. However, the title of "hardest" material might have to be awarded to other exotic substances.

Diamond is the standard for comparing the upper end of the hardness scale -- and it's a naturally occurring mineral that defines what "ultra-hard" materials are. A newly discovered form of carbon called Q-carbon is harder than diamond (pending verification), and it can be made at room temperature and pressure with lasers (though currently only as a film up to 500 nanometers thick). This synthesis method can also produce diamond-like films, too. [url]
A material called ultrahard fullerite is difficult to synthesize, but researchers are still looking for better methods to make this stuff. Ultrahard fullerite, made of a 3D polymer of connected fullerenes, can be twice as hard as natural diamond. Similar synthesis methods might also lead to aggregated diamond nanorods -- the least compressible known material (so far). [url]
Diamond was once the hardest known naturally occurring material, but lonsdaleite (aka hexagonal diamond) was first identified in meteorites in 1967 -- and could be harder than diamond. There are a few other "harder than diamond" candidates, too, but they're not naturally occurring. Lonsdaleite is "theoretically" harder than diamond, but natural samples vary in quality and many are softer than diamond. [url]

After you've finished checking out those links, take a look at our holiday gift ideas for cool gadgets and other awesome stuff.

Filed Under: aggregated diamond nanorods, allotrope, carbon, diamond-like, diamonds, hexagonal diamond, lonsdaleite, materials, q-carbon, ultrahard fullerite, ultrahard materials

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Lawrence D’Oliveiro, 8 Dec 2015 @ 5:33pm

Could Other Group-14 Elements Form Long Chains Besides Carbon?
Under Earth-surface conditions, it seems the answer is no. But what about other conditions, particularly under much higher pressures, or much lower temperatures, or both?
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- Michael Ho (profile), 8 Dec 2015 @ 5:46pm
  
  Re: Could Other Group-14 Elements Form Long Chains Besides Carbon?
  Actually... polysilanes, polygermanes, polystannanes, etc exist, but they're not as stable as the carbon analogs. Also, aromatic ring structures aren't favorable with the larger atoms. So nanotube/buckyball/graphene/etc analogs from silicon/etc aren't going to be very likely to form under practical conditions.
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  - Lawrence D’Oliveiro, 8 Dec 2015 @ 7:31pm
    
    Re: under practical conditions
    Thinking about places like on Titan, inside Jupiter, or even deep underground here on Earth.
    
    The JOIDES Resolution research ship has set sail for the Indian Ocean to drill the first-ever hole through to the mantle.
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  - Vitomir Jovanovic, 10 Dec 2015 @ 2:29pm
    
    Re: Re: Could Other Group-14 Elements Form Long Chains Besides Carbon?
    What does that mean term "practical conditions"? If You want to say that there are still no conditions to produce in large quantities, does not mean that there is no chance that something like that in the near future be done.
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