Aggregated diamond nanorods, or ADNRs (also called "hyperdiamond"), are an allotrope of carbon believed to be the hardest and least compressible known material, as measured by its isothermal bulk modulus; aggregated diamond nanorods have a modulus of 491 gigapascals (GPa), while a conventional diamond has a modulus of 442 GPa.^[1]

ADNRs are also 0.3% denser than regular diamond. The ADNR material is also harder than type IIa diamond and ultrahard fullerite.

A process to produce the substance was discovered by physicists in Germany, led by Natalia Dubrovinskaia, at the University of Bayreuth in 2005.^[2] ADNRs are made by compressing allotropic carbon fullerene molecules (generally 60 carbon atoms per molecule) to a pressure of 20 GPa, while at the same time heating to 2500 kelvin, using a unique 5000-metric-ton (50 MN) multi-anvil press. The resulting substance is a series of interconnected diamond nanorods, with diameters of between 5 and 20 nanometres and lengths of around 1 micrometre each.

Artistic rendition of a diamond anvil cell

A diamond anvil cell, located at the European Synchrotron Radiation Facility at Grenoble, France, was used to measure the compressibility of the material.

See also

• Carbon nanotube
• Fullerite
• Diamond
• Rhenium diboride
• Mohs scale of mineral hardness

References

External links

• "Diamonds are not forever" at physicsweb.org.
• University of Bayreuth page on ADNRs (German)
• Photos of Aggregated diamond nanorods

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