Aggregated diamond nanorod

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

Discovery[edit]

Nanodiamond was convincingly demonstrated to be produced by compression of graphite in 2003 and in the same work found 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[edit]

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.[4] However, the test only works properly with a tip made of harder material than the sample being tested. This means that the true value for nanodiamond is likely somewhat lower than 310 GPa.[citation needed]

Synthesis[edit]

Close up image of fullerite powder taken using a Scanning Electron Microscope

ADNRs are produced by compressing fullerite powder — a solid form of allotropic carbon fullerene — with 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 300 to 2,500 K (27 to 2,227 °C).[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.[citation needed]

See also[edit]

References[edit]

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

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