Q-Carbon, a substance harder than diamond | Hacker News Reader

Q-Carbon, a substance harder than diamond

nytimes.com

41 pointsrglovejoy18 comments

The press release seems significantly better, includes the abstract of the papers, links to full texts, and isn't behind a paywall: https://news.ncsu.edu/2015/11/narayan-q-carbon-2015/

> Make Diamond at Room Temperature

then

> ... the temperature of the carbon is raised to 4,000 Kelvin

4000 K locally, due to laser heating, as opposed to being in a kiln. More importantly, it is done at ambient pressure, and doesn't need a diamond anvil or other high-pressure chamber.

There's also https://news.ycombinator.com/item?id=10671674. Not sure if better.

In case you want to see the original paper: http://scitation.aip.org/content/aip/journal/jap/118/21/10.1...

The Q-Carbon age... This will be a revolution in tooling if they deliver and it can be made cheap enough.

Promising but this looks too good to be true. Most of the articles I can find are regurgitations of the press release. Anyone find anything with an independent take?

There won't be an independent take until someone can try to reproduce the results which, given how simple the experimental setup seems to be, might not take long but hasn't happened yet. I have read the paper, though, and it appears to be a fairly complete study with good detail. It is a slightly surprising result, but I would not characterize it as obviously challenging the laws of physics or anything, it is just a manifestation of structural changes on a nano-scale that yields pretty nice properties.

I also happen to know Jay Narayan's previous work (and have debated him on a few occasions). I would say as a scientist, he is well respected and his results have been verified over a long career, so there is more than likely something here—even if it is more than meets the eye.

The whole idea makes perfect sense. Quenching has been used to harden other materials since ancient times, what happens is that the quenching causes rapid contraction which in turn creates a density change. So I believe this is real, there is no reason carbon should not exhibit this.

That's not at all how or why quenching works. Quenching is used to accelerate the rate at which a metal alloy solidifies/crystalizes such that the internal arrangement of the components is affected. Quenching has nothing to do with density, and since pure carbon is neither metallic or an alloy, quenching pure carbon makes no sense at all.

Hm, ok. I'm happy to stand corrected. What I remembered was the outer layer cooling more rapidly than the inner layer resulting in a different crystal layer on the outside and tension in the steel leading to a different density than you'd get otherwise but that is apparently wrong. I'll read up on it, I don't like mis-remembering stuff like this. Thanks for the correction!

IIRC that's what happens in glass with Prince Rupert's Drops (according to Smarter Every Day).

Here they are talking about surface quenching, where the amorphous carbon thin film is heated then rapidly cooled on the surface. Instead of forming smaller precipitates, like in an alloy, it just forms very small crystals that happen to be extremely hard. They are embedded in amorphous material. The key phrase that capture this is: "This Q-carbon has amorphous structure with some embedded nanocrystalline diamonds the number density of which is determined by the nucleation time available for growth." Hopefully this clears things up somewhat.

Pure carbon is actually metallic at sufficiently high temperatures, as reported in this paper and in this citation: [1].

1. F. P. Bundy , W. A. Bassett , M. S. Weathers , R. J. Hemley , H. U. Mao , and A. F. Goncharov , Carbon 34, 141 (1996).http://dx.doi.org/10.1016/0008-6223(96)00170-4

From the press release it sounds like the important property is that the carbon is amorphous (at least, before it's heated by the laser), i.e. it doesn't follow a simple, repeating crystal pattern. It sounds like the laser pulse is forming something like a glass, although it's been a while since I studied condensed matter physics ;)

The carbon is amorphous before it is heated, then it forms various crystalline structures it appears (you can see that in the Raman, EELS, and other measurements, though the quick way to identify that is all the discussion of various crystalline planes).

EDIT for clarity: *forms various crystal structures that are embedded in the amorphous layer.

"[R]esearchers say" this, "researchers say" that... Why not do real reporting, and write a real article, which has verified facts, and doesn't need weasel phrases?

I'm not sure how they would be able to do that effectively without input from researchers. I don't see that as a weasel phrase, but as a (reasonable IMO) deference to experts in the field.

Reporters can contact sources. They call the person who wrote the paper or other experts and then quote them in the article.

This has the benefit of making the reporter's story contain some actual unique information. More importantly, it meant that the person reporting the story had checked with a person to confirm what they were reporting. One of the reasons that wrong stories get repeated in online journalism is that people just rush to repost something without checking with anyone to make sure its true.

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