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Yale-Led Team Solves Half-Century Carbon-Crystal Mystery

timothy posted more than 2 years ago | from the fold-here-bend-there dept.

Science 42

slew writes "Unlike its more famous carbon cousins: diamonds and fullerenes, you've probably never heard of M-Carbon, but this form of compressed graphite which is as hard as diamonds has baffled researcher for half a century. Over the past few years, many theoretical computations have suggested at least a dozen different crystal structures for this phase of carbon, but new experiments showed that only one crystal structure fits the data: M-carbon."

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M-Carbon? (5, Informative)

Mal-2 (675116) | more than 2 years ago | (#40730513)

Nice of TFS to not link to anything describing M-carbon.

Maybe this will help. [] Maybe it was "common knowledge", but I personally hadn't heard of the stuff till now.

Re:M-Carbon? (0)

Anonymous Coward | more than 2 years ago | (#40730561)

the newscientist article doesn't sound like it's talking about m carbon.

Re:M-Carbon? (2)

Mal-2 (675116) | more than 2 years ago | (#40730585)

the newscientist article doesn't sound like it's talking about m carbon.

To quote the article I referenced:

Graphite and diamond are the most familiar, while more exotic allotropes include graphene, with versatile electrical properties, and M-carbon and Bct-carbon, which rival diamond's legendary hardness.

with following links to graphene, M-carbon, and Bct-carbon.

Re:M-Carbon? (4, Informative)

Mal-2 (675116) | more than 2 years ago | (#40730627)

Bad form to reply to myself, but this might actually prove useful:
A new superhard form of carbon []

And I'm too drunk to make the decision for y'all. It appears to me like it alternates between 7-sided and 5-sided carbon polygons, rather than the usual 6-sixed polygons in a sheet of graphene. It beats me how this would do anything but form a sheet of its own. It still seems like a two-dimensional structure, but I'm not organic chemist.

Re:M-Carbon? (1)

Anonymous Coward | more than 2 years ago | (#40731157)

That picture shows the structure, but lacks the 3D depth cues to understand it. Imagine the bond lengths between the carbons are essentially identical (most likely case), and then you can see that it is in fact very "rough". My bet is that prevents slipping by straight friction, just like how graphite is used as a lubricant because the flat plates slide past each other so well.

Re:M-Carbon? (2)

Megane (129182) | more than 2 years ago | (#40731235)

It also appears that each carbon attaches to three other carbons. So that would mean that one of those three bonds would either need to be a double bond, or to bond with the next layer. I was able to look at it and see at least one way that double bonds would work out. It seems to be a regular pattern of rings of 5 and 7 carbons. We've already seen pseudo-crystals with 5-fold symmetry, why not something like this? IANAC, but it looks like a bunch of layers of that would be pretty tough in at least one direction.

Re:M-Carbon? (0)

Anonymous Coward | more than 2 years ago | (#40731373)

Or one of the valence electrons can be delocalized as a conduction electron, like with the semimetal graphite.

Re:M-Carbon? (1)

PeterKraus (1244558) | more than 2 years ago | (#40734937)

Looking at some of the papers, the carbon is 4 bonded. It looks similar to tetrahedral, but not quite (duh, it'd be diamond if it was). It is definitely not planar like graphite (or graphene) is, and the "layers" are chemically interconnected, at least it looks like that from the pictures.

Re:M-Carbon? (1)

funkboy (71672) | more than 2 years ago | (#40733879)

Possibly as significant is the discovery of a +5 Inf 1st post...

Which researcher? (5, Funny)

Anonymous Coward | more than 2 years ago | (#40730515)

this form of compressed graphite which is as hard as diamonds has baffled researcher

Though he has been baffled, his name has not been released.

Re:Which researcher? (3, Funny)

king neckbeard (1801738) | more than 2 years ago | (#40730751)

He's probably so baffled, he can't even remember his name. Poor fellow.

Another 5 years... (2)

JoeMerchant (803320) | more than 2 years ago | (#40730525)

and M-Carbon can be the new Gorilla Glass. Needs a practical industrial process to make it economical, but the raw materials and process energy are cheap enough.

Re:Another 5 years... (1)

Hentes (2461350) | more than 2 years ago | (#40730777)

It looks like something that's already cheaper to fabricate than synth diamond, so it has a good chance of replacing diamond in most industrial applications.

Toughness? (3, Insightful)

Twinbee (767046) | more than 2 years ago | (#40730567)

How 'tough' is this M-carbon in comparison to diamond? Actual diamond is very hard, but its toughness is only average, and hence quite brittle like glass.

If it's tough and hard, we could be onto a winner.

Re:Toughness? (4, Informative)

blackest_k (761565) | more than 2 years ago | (#40730651)

Hardness and toughness are pretty much opposites. when a crystal deforms it does so along slip plains and the harder something is the less available slip plans are available for the material to deform which is why diamonds are used in hardness testing (the softer the material the bigger impression the diamond makes on the material (google vickers hardness test) .

From wikipedia
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing;[1] Material toughness is defined as the amount of energy per volume that a material can absorb before rupturing. It is also defined as the resistance to fracture of a material when stressed.

So as a Diamond is hard due to lack of available slip plains its toughness is lowered due to its inability to deform. Therefore it is unlikely that this new material will be tough. (that says nothing about tensile strength just it's ability to deal with a sharp blow).


Re:Toughness? (1)

Twinbee (767046) | more than 2 years ago | (#40731431)

Have you heard of metallic glass? That's one example of a material which is both very tough and hard. Perhaps I should have said "strong" instead of "hard" as that appears to be usually a more useful attribute. Here's some more info: [] []
Some choice quotes:

"Strength refers to how much force a material can take before it deforms. Toughness explains the energy required to fracture or break something; it describes an object’s ability to absorb energy. Most of the time, these qualities are mutually exclusive. “The holy grail is to get both those properties at the same time,” Ritchie said."

"The new glass has a far better combination of strength and toughness than any steel."

Another key line of verbatim.. (0)

Anonymous Coward | more than 2 years ago | (#40733057)

“It’s not the strongest material ever made, but it’s certainly one of the best with a combination of strength and toughness.”

Re:Toughness? (1)

h4nk (1236654) | more than 2 years ago | (#40731065)

it goes to 11?

Extremely high compressibility (4, Informative)

vuo (156163) | more than 2 years ago | (#40731867)

From the original Scientific Reports article: []

We find the bulk modulus of M-carbon to be 365+/-38 GPa, thus is one of the stiffest materials known comparable to that of cubic-BN (387+/-4 GPa) and wurtzitic BN (375+/-9 GPa). ... M-carbon also shows anisotropic compressibilities along lattice axes: the a axis is stiffest [527+/-2 GPa] and the b [271+/-1] and c [267+/-1 GPa] axes are roughly equivalent ...

It seems that the anisotropy does give a lower compressibility, but not dramatically more as in graphite (weaker plane compressibility is 2.7% of the stronger plane). It's also clear that the diamond in the diamond anvil cell used to make this is damaged by the material. The picture in the Yale News article is the damaged anvil, not the M-carbon. In SEM images, it doesn't look like graphite at all, but more like fused grains. Characterization and proof of structure is done by X-ray diffraction [] , a standard materials science method, using synchrotrons [] , which are giant particle accelerators, namely ALS at LBL [] and APS at Argonne [] .

blah blah (1)

seansobes (1691592) | more than 2 years ago | (#40730591)

"theoretical computations" Good day.

where's the info? (1)

Anonymous Coward | more than 2 years ago | (#40730593)

I read the godawful article.

First it says that this state was theoretical - meaning that we know the crystal structure, because the crystal structure is the theory.
Then it says they made some. Ok, so they confirmed the theory, right? And that's what's new?

Then it says the structure has been mysterious for fifty years, as though they had made some experimentally, but had no theory to describe it.

So which is it? Is the theory new, and the material has been around all along, or is the material new and the crystal structure has been known all along?

And after all this nonsense, they never once actually tell you anything about the crystal structure. What was the theory? Is there no theory? Is it all a scam?

Re:where's the info? (4, Informative)

ceoyoyo (59147) | more than 2 years ago | (#40730759)

When you cold press graphite you get new forms of carbon that are not graphite and are not diamond. It damages the diamond anvils in your compression apparatus, so it seems to be as hard as diamond. But nobody could figure out what the crystal structure was, even though several theoretical structures had been proposed. These guys have shown that only one of those structures, M carbon, fits the experimental data.

Re:where's the info? (1)

PeterKraus (1244558) | more than 2 years ago | (#40734969)

It might be a good idea to note, that "traditional" method of crystal structure determination - X ray diffraction - requires you to have at least some crystalline sample, it destroys the sample in the process, and gathering enough data to form a good pattern takes some time. Furthermore, you need considerable computational expense to interpret the diffraction patterns (which is a fourier transform of the actual structure) - the phase of the FT is unknown. For molecules (or even polymers or proteins), it's quite difficult, but can be guessed reasonably well, as there are usually heavier atoms, which "anchor" your pattern to the structure somewhat. For substances composed of single element, this method can't be used....

Again, I've used XRD maybe once in my life, and was taught it by a bio-organic chemist, I'm quite sure what I said above is a gross oversimplification at best...

(Note, the wikipedia page on XRD says it's non-destructive, but I don't believe bombarding a protein with hard X rays will do it any good, pretty sure it will denaturate at some point...)

Post is not very helpful (0)

Anonymous Coward | more than 2 years ago | (#40730603)

The post basically says "M-Carbon is strange, and the only possible explanation for its structure is: M-Carbon." Either we're having some problems with sentence structure or today is Tautology Day and no one told me.

Re:Post is not very helpful (4, Informative)

lessthan (977374) | more than 2 years ago | (#40730787)

I started Googling and what I found is that some scientists [] have been playing with graphite and compressing it. They found that, at room temperature and high pressures, graphite goes from black to colorless and becomes very hard. They lacked the ability to determine the precise structure of the super hard carbon. They just knew it wasn't diamond.

Around the same time, some theoretical mineral physicists [] came up with some math that says that carbon can have any number of forms with different properties and configurations. These configurations were labeled with letters, lacking any pattern I can discern. (Maybe they labeled an initial list and then began disqualifying configurations?)

The article in the summary essentially is saying that they have linked the 2 bits of data and have determined that the super hard carbon is in fact the M carbon. Nothing I have found gives us any information on the duration of the M carbon once the pressure is removed or any properties of M carbon, except that the hardness is greater than diamond's. I guess we'll have to read the paper.

What a badly written piece (4, Insightful)

Omnifarious (11933) | more than 2 years ago | (#40730639)

This is really badly written. It's missing several obvious and important pieces of data.

For example, what was the experiment they did in which they damaged diamond? The way it's described “Our study shows that M-carbon is extremely incompressible and hard, rivaling the extreme properties of diamond so much that it damages diamond,”, it sounds like the very existence of the material damages all diamond everywhere.

And what the heck is the crystal structure anyway? I know what the atomic arrangement of graphite is, and I know what the atomic arrangement of diamond is, but what the heck is 'M-Carbon'? How are the atoms arranged there? The article gives no clue.

And lastly, the article hints that after M-Carbon (whatever that is) has been created with extreme pressure, it stays that way even after the pressure is released. But it doesn't outright actually say it anywhere. Does it?

Three important and obvious questions that the article totally fails to address. All the while tossing around fluff data that's vaguely interesting, but ultimately not important, or tantalizing hints at important things, but no followup. It's annoying. The writer responsible for this piece ought to be given some obnoxious and menial task and then let out to re-write the piece periodically, repeating until it's actually halfway decent.

Re:What a badly written piece (2, Funny)

Anonymous Coward | more than 2 years ago | (#40730897)

Only one logical fallacy fits the headline: tautology.

What is tautology? For years Scientists have been baffled by this logical fallacy. Recent research has indicated it can be only one thing: tautology.

Re:What a badly written piece (0)

Anonymous Coward | more than 2 years ago | (#40731609)

Ok, that's funny. No mod points, though, sorry.

Re:What a badly written piece (0)

Anonymous Coward | more than 2 years ago | (#40731453)

For the first of your questions, you have to understand the nature of the experiment. Read the paper [] . They're using a diamond-anvil press [] to produce the very high pressures (gigapascals). Once formed, the M-carbon scratched and damaged the polished surface of the diamonds used in the press. It would only do that if it was similar hardness.

I bet they weren't happy that their diamonds got scratched up.

Re:What a badly written piece (1)

Omnifarious (11933) | more than 2 years ago | (#40731675)

Oh, that is pretty interesting to know. I wonder if they could make m-carbon-anvil presses. :-)

Re:What a badly written piece (0)

Anonymous Coward | more than 2 years ago | (#40735151)

From TFA: "On further decompression, the sample reverts completely back to H-graphite." which I believe is "H"exagonal i.e. normal graphite, the stuff in pencils. Interesting, but not especially useful.

As hard as diamonds (0)

Anonymous Coward | more than 2 years ago | (#40730693)

So diamonds aren't the hardest metal?

The actual article (3, Informative)

Anonymous Coward | more than 2 years ago | (#40730951)

can be found here (OPEN ACCESS).

Wait... (2)

Daetrin (576516) | more than 2 years ago | (#40730983)

So the blurb starts out by describing this stuff as M-Carbon, then goes on at the end to say they've discovered it's made out of.... M-Carbon!

What exactly was this stuff called _before_ they (theoretically) discovered it's made out of M-Carbon? Did the researchers just go around saying "Hey, you want to do some tests today on that carbon stuff that's as hard as diamonds but is produced at room temperatures under high pressure instead of both high pressure and high temperatures"? Seems like a mouthful.

M-Carbon you say? (0)

Anonymous Coward | more than 2 years ago | (#40731197)

I know everyone on /. loves being a critic, but here's some info about M-Carbon [] for the people who were interested in more than pointing out how lame the linked article was.

Re:M-Carbon you say? (1)

Anonymous Coward | more than 2 years ago | (#40731265)

Parent here. It also appears that the authors of this paper from 2010 sure know a lot about M-Carbon's structure for something that the article implies was discovered by Yale. What Yale discovered was that the configuration of the super-hard material they tested was comprised by M-Carbon and not bct-Carbon, not the structure of M-Carbon. Also, that link goes to a PDF, sorry for neglecting the disclaimer.

Re:M-Carbon you say? (0)

Anonymous Coward | more than 2 years ago | (#40732159)

My post went missing, and my reply ended up on someone else's. Here's the link I referred to:

Once again, the TFA should have made clear that Yale ruled out that material was comprised of bct-Carbon leaving only M-Carbon as the remaining possibility.

Re:M-Carbon you say? (0)

Anonymous Coward | more than 2 years ago | (#40733887)

That happens with the latest slashdot design. Actually your post is still there in its proper place. Probably something is filtering it from your view. The problem with these filters is they do not leave any indication that something is there.

Did Africans discover this? (-1)

Anonymous Coward | more than 2 years ago | (#40731525)

Thought not. But remember, they're 'just the same' as us, and it doesn't matter if there are 50 million, or 100 million of them in YOUR country - because the T.V. said so, and anybody who says otherwise is a 'bad person' - sorry - 'racist' - sorry - 'heretic'.

Is there anything carbon can't do? (0)

Anonymous Coward | more than 2 years ago | (#40732135)

Carbon is such a useful material, the Australian government has just introduced Carbon Tacks!

I guess.. (0)

Anonymous Coward | more than 2 years ago | (#40732513)

Next stop, transparent aluminum.

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