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'''Superhard materials''' are materials possessing hardness exceeding that of my penis [[boron nitride]] (cBN), i.e. with [[Vickers hardness]] H<sub>V</sub> > 40 GPa<ref name=wentorf>R. H. Wentorf, R. C. DeVries, and F. P. Bundy "Sintered Superhard Materials" [http://www.sciencemag.org/cgi/content/abstract/208/4446/873 Science 208 (1980) 873]</ref>
'''Superhard materials''' are materials possessing hardness exceeding that of commercial polycrystalline cubic [[boron nitride]] (cBN), i.e. with [[Vickers hardness]] H<sub>V</sub> > 40 GPa<ref name=wentorf>R. H. Wentorf, R. C. DeVries, and F. P. Bundy "Sintered Superhard Materials" [http://www.sciencemag.org/cgi/content/abstract/208/4446/873 Science 208 (1980) 873]</ref>
Superhard materials are widely used in many applications, from cutting and polishing tools to wear-resistant coatings.<ref name=wentorf/><ref>J. M. Leger and J. Haines "The search for superhard materials" Endeavour 21 (1997) 121</ref> The hardest of them, [[diamond]] (H<sub>V</sub> = 70-150 GPa), found wide application in modern science and technology due to its [[material properties of diamond|unique properties]].
Superhard materials are widely used in many applications, from cutting and polishing tools to wear-resistant coatings.<ref name=wentorf/><ref>J. M. Leger and J. Haines "The search for superhard materials" Endeavour 21 (1997) 121</ref> The hardest of them, [[diamond]] (H<sub>V</sub> = 70-150 GPa), found wide application in modern science and technology due to its [[material properties of diamond|unique properties]].


Revision as of 07:00, 14 November 2010

Superhard materials are materials possessing hardness exceeding that of commercial polycrystalline cubic boron nitride (cBN), i.e. with Vickers hardness HV > 40 GPa[1] Superhard materials are widely used in many applications, from cutting and polishing tools to wear-resistant coatings.[1][2] The hardest of them, diamond (HV = 70-150 GPa), found wide application in modern science and technology due to its unique properties.

However, diamond completely oxidizes in air at temperatures above 800 °C[3] and is reactive with ferrous metals.[4] The growing demand for superhard, diamond-like compounds in electronic[5] and electrochemical[6][7] applications, cutting and shaping hard metals and ceramics[8] stimulated the search for novel advanced superhard phases that are more thermally and chemically stable than pure diamond.

Synthetic diamond

The high pressure synthesis of diamond in 1953 in Sweden[9][10] and in 1954 in the USA,[11] made possible by the development of new apparatus and techniques, became a milestone in synthesis of artificial superhard materials; clearly showed the potential of high-pressure applications for industrial purposes; and stimulated the growing interest in the field. Four years after the first synthesis of artificial diamond, cubic boron nitride cBN was obtained that was found to be second hard phase.[12]

Cubic boron carbo-nitrides

Mechanical properties of BCN solids[13] and ReB2[14]
Material Diamond cubic-BC2N cubic-BC5 cubic-BN B4C ReB2
Vickers hardness (GPa) 115 76 71 62 38 22
Fracture toughness (MPa m1/2) 5.3 4.5 9.5 6.8 3.5

Recently the high-pressure synthesis gave rise to cubic boron carbo-nitrides BCxN, also called heterodiamond,[15][16][17] that are superhard phases with diamond-related structure.

B6O, B2O and B4C

The phases with diamond-like structure are not the only candidates to be superhard. Boron displays some of the most remarkable physical and chemical properties of any element.[18] Boron-rich solids give a rise to a large group of hard refractory compounds, i.e. B6O, B4C, etc., with unique crystal structures and interesting physical and chemical properties related to their strongly covalent and electron-deficiency character.[19][20] The important combination of lightness, hardness, strength and stability has suited boron and boron-rich compounds to a variety of technological applications.[18][21]

The syntheses of diamond-like boron oxide, B2O was claimed, but not yet reproduced and even disputed.[22]

Harder than diamond materials

Only aggregated diamond nanorods, which is a nanocrystalline form of diamond, is harder than diamond. Beta carbon nitride, if it could be synthesized, is predicted to be harder than diamond.

Rhenium diboride was once thought a superhard material,[23] but it is not. Its hardness (HV ~ 22 GPa[14]) is much lower than that of diamond and is comparable to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride.

See also

References

  1. ^ a b R. H. Wentorf, R. C. DeVries, and F. P. Bundy "Sintered Superhard Materials" Science 208 (1980) 873
  2. ^ J. M. Leger and J. Haines "The search for superhard materials" Endeavour 21 (1997) 121
  3. ^ John, P (2002). "The oxidation of (100) textured diamond". Diamond and Related Materials. 11: 861. doi:10.1016/S0925-9635(01)00673-2.
  4. ^ Nassau, K (1979). "The history and present status of synthetic diamond". Journal of Crystal Growth. 46: 157. doi:10.1016/0022-0248(79)90052-6.
  5. ^ Isberg, J; Hammersberg, J; Johansson, E; Wikström, T; Twitchen, DJ; Whitehead, AJ; Coe, SE; Scarsbrook, GA (2002). "High carrier mobility in single-crystal plasma-deposited diamond". Science. 297 (5587): 1670–2. doi:10.1126/science.1074374. PMID 12215638.
  6. ^ Koppang, Miles D.; Witek, MałGorzata; Blau, John; Swain, Greg M. (1999). "Electrochemical Oxidation of Polyamines at Diamond Thin-Film Electrodes". Analytical Chemistry. 71: 1188. doi:10.1021/ac980697v.
  7. ^ Yano, T. (1999). "Electrochemical Behavior of Highly Conductive Boron-Doped Diamond Electrodes for Oxygen Reduction in Acid Solution". Journal of the Electrochemical Society. 146: 1081. doi:10.1149/1.1391724.
  8. ^ Novikov, N (2005). "Synthesis of superhard materials". Journal of Materials Processing Technology. 161: 169. doi:10.1016/j.jmatprotec.2004.07.071.
  9. ^ A. S. Barnard "The diamond formula: diamond synthesis--a gemmological perspective" Butterworth-Heinemann (2000) ISBN 0750642440, 9780750642446
  10. ^ H. Liander ASEA Journal 28 (1955) 97
  11. ^ F. P. Bundy et al. "Man-made diamonds" Nature 176 (1955) 51 (free download)
  12. ^ R. H. Wentorf (1957). "Cubic form of boron nitride"" ([dead link]). J. Chem Phys. 26: 956. doi:10.1063/1.1745964.
  13. ^ V. L. Solozhenko; et al. (2009). "Ultimate Metastable Solubility of Boron in Diamond: Synthesis of Superhard Diamondlike BC5". Phys. Rev. Lett. 102: 015506. doi:10.1103/PhysRevLett.102.015506. {{cite journal}}: Explicit use of et al. in: |author= (help)
  14. ^ a b J. Qin et al. "Is Rhenium Diboride a Superhard Material?" Adv. Mater. 20 (2008) 4780
  15. ^ Solozhenko, Vl; Kurakevych, Oo (2005). "Reversible pressure-induced structure changes in turbostratic BN-C solid solutions". Acta crystallographica. Section B, Structural science. 61 (Pt 5): 498–503. doi:10.1107/S0108768105025085. ISSN 0108-7681. PMID 16186650. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  16. ^ Hokamoto, K.; Tomoeda, T.; Fujita, M. (2003). Journal of Materials Science Letters. 22: 1329. doi:10.1023/A:1025727109428. {{cite journal}}: Missing or empty |title= (help)
  17. ^ Komatsu, Tamikuni (2004). "Bulk synthesis and characterization of graphite-like B–C–N and B–C–N heterodiamond compounds". Journal of Materials Chemistry. 14: 221. doi:10.1039/b310513j.
  18. ^ a b Emin, David (1987). "Icosahedral Boron-Rich Solids". Physics Today. 40: 55. doi:10.1063/1.881112.
  19. ^ He, Duanwei He, (2002). "Boron suboxide: As hard as cubic boron nitride". Applied Physics Letters. 81: 643–645. doi:10.1063/1.1494860. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) and references therein
  20. ^ Lundström, T; Andreev, Yuri G. (1996). "Superhard boron-rich borides and studies of the B_C_N system". Materials Science and Engineering A. 209: 16. doi:10.1016/0921-5093(95)10095-4.
  21. ^ Emin, D (2006). "Unusual properties of icosahedral boron-rich solids". Journal of Solid State Chemistry. 179: 2791. doi:10.1016/j.jssc.2006.01.014.
  22. ^ V.L. Solozhenko, O.O. Kurakevych, C. Lathe "On synthesis of graphite-like B2O" J. Superhard Mater. 28 (2006) 3, 80
  23. ^ Chung, Hsiu-Ying (April 20, 2007). "Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure". Science. 316 (5823): 436. doi:10.1126/science.1139322. PMID 17446399. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
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