Engines of Our Ingenuity

No. 452:
DIAMONDS

by John H. Lienhard

Click here for audio of Episode 452.

Today, we turn thought into diamonds. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Hard as diamond! Clear as diamond! Diamond is a powerful metaphor for perfection we rarely achieve on this imperfect earth. And it's a material that lives up to its reputation. It's the hardest natural material. It's the best natural conductor of heat -- five times better than copper or silver. Yet it's also an electric insulator.

Diamond is transparent as nothing else is. Glass and water transmit only visible light. Diamond is transparent on both sides of the visible range. It will let ultraviolet and infrared, as well as X-rays, through. Diamond is a material we'd dearly love to use in all sorts of processes.

But a natural diamond, even the size of peanut, is rare and hopelessly expensive. It derives part of its beauty from slight impurities. We have powerful cause to make our own diamonds. Good homemade diamonds would be far more valuable in human terms than anything Amsterdam offers.

In 1954, people at GE learned to make diamonds by heating and compressing graphite. Today, that's done at 2700 degrees Fahrenheit and a million pounds per square inch. We can create a limitless supply of diamonds. But the result has drawbacks. It isn't very pure. It's made from many small crystals, not one big one. It costs a dollar a carat, and it's widely used to make abrasives.

Now the Japanese have created a new process. It's called CVD, for Chemical Vapor Deposition. They condense carbon vapor on a plate in the presence of atomic hydrogen. It's still a grainy material, but it's pretty pure. You can make it into sheets as large as 1-1/2 inches by 12 inches. The problem with the process is its cost -- around $100 a carat. The expense doesn't come from the process itself. It comes from the cost of breaking hydrogen molecules into atoms.

The new process doesn't put the problem of making diamonds to rest. But it opens a window into the imagination. Now we can make diamonds without going to science-fiction pressures. The process gives us hope. Now we call on a new science called epitaxy. Epitaxy means growing single crystals of a material on top of another material. That's one way to make semiconductors. We've begun learning to deposit carbon vapor into pure crystals.

Diamonds have driven the imagination for centuries, but they're doing it today as never before. Now they promise windows that can't be clouded, glasses that can't be scratched, computer chips that won't melt, and much more. But the promise isn't free. It depends on our making full use of our inventive minds.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Pool, R., Diamond Films Sparkle as They Come to Market. Science, Vol. 209, 6 July, 1990, Research News, pp. 27-28.



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The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.


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