If I had super strength, could I squeeze coal into diamonds?

July 24, 2009

Dear Cecil:

Superman is able to use his super strength to squeeze coal into diamonds. Theoretically, if someone had unlimited strength in real life, would it be possible to do this?

Cecil replies:

You realize, Marcus, we're talking about what (a) a fictional character of virtually unlimited powers (barring kryptonite-related issues) could, (b) if real, be (c) theoretically but (d) realistically expected to do. Even by Straight Dope standards this takes us into a pretty abstruse realm. That's probably why I got into a big argument on the subject with my assistant Una, who's normally as tranquil as a September morn.

Admittedly I started off behind the eight ball owing to my scandalously inadequate knowledge of artificial diamond making. I submitted that squeezing coal into diamonds was impossible. Somewhere I'd gotten the idea that fake diamonds were all made by a process known as chemical vapor deposition, and that CVD approximated how natural diamonds were made.

CVD involved heat and pressure, but the main thing was you started out with a seed crystal you bathed in carbon-rich vapor and from this the diamond was basically grown. That was a far cry from the scenario in the comic books, where Superman grabbed a chunk of coal, squeezed, and voila, a diamond. For one thing, growing a diamond via CVD could take two or three days. Not to slight this achievement, but it wasn't the kind of dramatic gesture that was going to thrill Lois Lane.

Una conceded you couldn't squeeze an ordinary lump of coal into a diamond — too many impurities. (In gem-grade diamonds, impurities, such as the boron that makes the Hope diamond blue, are on the order of one part per 20,000, while in even the best-quality coal we're talking one part in 10.) However, she contended, it was quite possible to make a diamond by squeezing pure graphite, because in fact there were two ways of making artificial diamonds — CVD, which gets most of the media attention nowadays, and the older high-pressure-high-temperature method.

HPHT was exactly what it sounded like. Generally you needed pressure of at least 130,000 atmospheres and a temperature higher than 3,100 degrees Fahrenheit, but if you could manage that you were in business. Una browsed through the technical articles and found one from 1964 showing a photo of a graphite rod that had gotten the HPHT treatment. The ends were still graphite, but the center had been compressed into what the caption claimed was, and sure looked like, a diamond. Hard to argue with that.

I gave it a shot anyway. I pointed out that HPHT required an elaborate press of intricate geometry to concentrate the compressive forces. It wasn't as if Superman could just grab a lump of graphite and squeeze it like a tomato.

He's Superman, said Una. According to Wikipedia, he can withstand the impact of a nuclear explosion. You're saying diamonds are going to stymie him because he hasn't got the right belt-press jig?

Me: I'm saying if "he's Superman" is the answer to all questions, why are we having this discussion? He can do anything he wants by magic. We're trying to establish what somebody with unlimited strength could do in real life.

Una: Nobody has unlimited strength in real life.

Me: I know that. That's the point. We have to set some reasonable bounds on the question. Let's say you've got enough strength to manage 130,000 atmospheres. Is that alone enough to create a diamond? I say no. Never mind the special press, you still need a temperature of 3,100 degrees.

Una: Heat vision.

Me: How's that supposed to work? Superman presumably is squeezing the graphite rod in his hand. You're telling me he's going to use his super powers to heat his own body to nearly one-third the temperature of the surface of the sun?

Una: He's Superman.

Me: This isn't getting us anywhere.

Una: Let's use something besides HPHT then. Superman could create the diamonds by setting off a super explosion. Diamond crystals five nanometers in diameter can be formed by detonating certain carbon-containing explosives in a metal chamber.

Me: Where are you getting this from?

Una: Wikipedia.

Me: Will you quit with the Wikipedia? From the standpoint of reliability, Wikipedia might as well be written by gorillas. Besides, where, on short notice, is Superman supposed to come up with the carbon-containing explosives and the metal chamber?

Una. He's —

Me: That's OK. Forget I asked.

Hope this clarifies things, Marcus. And thanks. Posing the bold questions is how we advance the frontiers of knowledge. I'm not saying it's fast.

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References

Bundy, F. P. “Direct Conversion of Graphite to Diamond in Static Pressure Apparatus.” Science 137.3535 (1962): 1057-1058.

Delhaes, Pierre. Graphite and Precursors Amsterdam, The Netherlands: Overseas Publishers Association, 2001.

Irifune, Tetsuo et al. “Formation of pure polycrystalline diamond by direct conversion of graphite at high pressure and high temperature.” Physics of the Earth and Planetary Interiors. 143–144 (2004): 593–600.

Nassau, Kurt. “The origins of color in minerals.” American Minerologist 63 (1978): 219-229.

Suits, C.G. “Man-Made Diamonds-A Progress Report.” Proceedings of the American Philosophical Society, 108.5 (1964): 443-449.

Sung, J. “Graphite - diamond transition under high pressure: A kinetics approach.” Journal of Materials Science 35 (2000): 6041 - 6054.

Yarnell, Amanda. “The Many Facets of Man-Made Diamonds.” Chemical and Engineering News (February 2, 2004): 26-31.

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