Aggregated diamond nanorod explained

Aggregated diamond nanorods, or ADNRs, are a nanocrystalline form of diamond, also known as nanodiamond or hyperdiamond.

Discovery

Nanodiamond or hyperdiamond was produced by compression of graphite in 2003 by a group of researchers in Japan and in the same work, published in Nature, it was shown to be much harder than bulk diamond.^[1] Later, it was also produced by compression of fullerene and confirmed to be the hardest and least compressible known material, with an isothermal bulk modulus of 491 gigapascals (GPa), while a conventional diamond has a modulus of 442–446 GPa; these results were inferred from X-ray diffraction data, which also indicated that ADNRs are 0.3% denser than regular diamond.^[2] The same group later described ADNRs as "having a hardness and Young's modulus comparable to that of natural diamond, but with 'superior wear resistance'".^[3]

Hardness

A <111> surface (normal to the largest diagonal of a cube) of pure diamond has a hardness value of 167±6 GPa when scratched with a nanodiamond tip, while the nanodiamond sample itself has a value of 310 GPa when tested with a nanodiamond tip. However, the test only works properly with a tip made of harder material than the sample being tested due to cracking. This means that the true value for nanodiamond is likely lower than 310 GPa.^[4] Due to its hardness, a hyperdiamond could possibly exceed 10 on the Mohs scale of mineral hardness.

Synthesis

ADNRs (hyperdiamonds/nanodiamonds) are produced by compressing fullerite powder—a solid form of allotropic carbon fullerene—by either of two somewhat similar methods. One uses a diamond anvil cell and applied pressure ~37 GPa without heating the cell.^[5] In another method, fullerite is compressed to lower pressures (2–20 GPa) and then heated to a temperature in the range of 300K2500K.^{[6] [7] [8] [9]} Extreme hardness of what now appears likely to have been nanodiamonds was reported by researchers in the 1990s.^{[4] [5]} The material is a series of interconnected diamond nanorods, with diameters of between 5 and 20 nanometres and lengths of around 1 micrometre each.

Nanodiamond aggregates ca. 1 mm in size also form in nature, from graphite upon meteoritic impact, such as that of the Popigai impact structure in Siberia, Russia.

External links

• The invention of aggregated diamond nanorods at Physorg.com
• News: Diamonds are not forever . August 26, 2005 . Michelle . Jeandron . Physics World . https://web.archive.org/web/20090304203718/http://physicsworld.com/cws/article/news/22997 . March 4, 2009 . August 7, 2009 . dead .

Notes and References

1. Irifune . Tetsuo . Kurio . Ayako . Sakamoto . Shizue. Inoue . Toru . Sumiya . Hitoshi . Materials: Ultrahard polycrystalline diamond from graphite . Nature . 421 . 599–600 . 2003 . 10.1038/421599b . 12571587 . 6923. 2003Natur.421..599I . 52856300 .
2. Dubrovinskaia . Natalia . Dubrovinsky . Leonid . Crichton . Wilson . Langenhorst . Falko . Richter . Asta . Aggregated diamond nanorods, the densest and least compressible form of carbon . Applied Physics Letters . 87 . 8 . 083106 . 2005 . 10.1063/1.2034101 . 2005ApPhL..87h3106D.
3. Dubrovinskaia . Natalia . Dub . Sergey . Dubrovinsky . Leonid . Superior Wear Resistance of Aggregated Diamond Nanorods . Nano Letters . 6 . 4 . 824–6 . 2006 . 10.1021/nl0602084. 16608291 . 2006NanoL...6..824D .
4. Blank. V. 1998. Ultrahard and superhard phases of fullerite C₆₀: Comparison with diamond on hardness and wear. dead. Diamond and Related Materials. 7. 2–5. 427–431. 1998DRM.....7..427B. 10.1.1.520.7265. 10.1016/S0925-9635(97)00232-X. https://web.archive.org/web/20110721225258/http://nanoscan.info/wp-content/publications/article_03.pdf. 2011-07-21.
5. Blank . V . Popov . M . Buga . S . Davydov . V . Denisov . V . Ivlev . A . Marvin . B . Agafonov . V . Ceolin . R . 8. Is C₆₀ fullerite harder than diamond? . Physics Letters A . 188 . 3 . 281 . 1994 . 10.1016/0375-9601(94)90451-0. 1994PhLA..188..281B .
6. Kozlov . M . Superhard form of carbon obtained from C₆₀ at moderate pressure . Synthetic Metals . 70 . 1–3 . 1411–1412 . 1995 . 10.1016/0379-6779(94)02900-J.
7. Blank . V . Ultrahard and superhard carbon phases produced from C₆₀ by heating at high pressure: structural and Raman studies . Physics Letters A . 205 . 2–3 . 208–216 . 1995. 10.1016/0375-9601(95)00564-J. 1995PhLA..205..208B .
8. Szwarc . H . Davydov . V . Plotianskaya . S . Kashevarova . L . Agafonov . V . Ceolin . R . Chemical modifications of C under the influence of pressure and temperature: from cubic C to diamond . Synthetic Metals . 77 . 1–3 . 265–272 . 1996 . 10.1016/0379-6779(96)80100-7.
9. Blank . V . Phase transformations in solid C₆₀ at high-pressure-high-temperature treatment and the structure of 3D polymerized fullerites . Physics Letters A . 220 . 1–3 . 149–157 . 1996 . 10.1016/0375-9601(96)00483-5. 1996PhLA..220..149B .