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Champion of strength is forged in mighty anvil

Peter Weiss

A newly created form of carbon has captured the crown of world's strongest known material. A team of researchers in Germany and France made the new material using a specialized, multijawed anvil that simultaneously squeezed and heated a powder of all-carbon molecules known as buckyballs.

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STRONGER THAN DIAMOND. This carbon plug ranks as the strongest substance known.

Dubrovinskaia et al./Applied Physics Letters

At 200,000 times atmospheric pressure and a temperature of 2,500 kelvins, the powder coalesced into an extraordinarily hard, dense, black plug about the size of a poppy seed. Electron microscope images revealed that the new material is composed of randomly arranged diamond needles no more than 20 nanometers wide but up to a micrometer long. Natalia Dubrovinskaia of the University of Bayreuth in Germany and her colleagues describe this material, composed of what they call diamond nanorods, in the Aug. 22 Applied Physics Letters.

When the researchers measured the plug's resistance to compression—a strength-related property called the bulk modulus—they found it to be a whopping 491 gigapascals (GPa).

For years, scientists rated diamond, with a bulk modulus of 442 GPa, as the world's strongest material. Just 3 years ago, measurements of the rarely used element osmium stunned researchers by suggesting that it was stronger than diamond, having a bulk modulus of 462 GPa (SN: 4/6/02, p. 211). Now, it seems that osmium's brief reign has ended.

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References:

Dubrovinskaia, N., L. Dubrovinsky, et al. 2005. Aggregated diamond nanorods, the densest and least compressible form of carbon. Applied Physics Letters 87(Aug. 22):083106. Abstract.

Further Readings:

Weiss, P. 2004. Hard stuff: Cooked diamonds don't dent. Science News 165(Feb. 28):131. Available at Science News.

______. 2002. Better-built diamonds: Fast growth, purity may multiply uses. Science News 162(Sept. 14):165. Available at Science News.

______. 2002. Osmium is forever: Rare metal's strength humbles mighty diamond's. Science News 161(April 6):211. Available at Science News.

Wu, C. 1999. A new route to a superhard material? Science News 155(June 5):367.

______. 1998. As hard as diamond? Science News 154(July 11):28–29. Available at Science News.

______. 1997. Stresses and strains on diamonds. Science News 151(May 31):340.

______. 1996. Carbon onions put on the pressure. Science News 150(Aug. 31):139.

Sources:

Natalia Dubrovinskaia
Bayerisches Geoinstitut
Universität Bayreuth
95440 Bayreuth
Germany

Leonid Dubrovinsky
Bayerisches Geoinstitut
Universität Bayreuth
95440 Bayreuth
Germany


From Science News, Volume 168, No. 12, September 17, 2005, p. 189.