Designing Ultra-incompressible, Superhard Materials Richard B. Kaner, UCLA, DMR-0453121

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Designing Ultra-incompressible, Superhard
MaterialsRichard B. Kaner, UCLA, DMR-0453121

• Interest in the mechanical properties of
  materials is spurred by opportunities for
  industrial applications. These applications
  require highly robust materials for use as
  abrasives, cutting tools and coatings. Therefore,
  the development of a new class of
  ultra-incompressible, superhard materials is of
  great practical interest as we discuss in
  Science, 308, 1268, 2005.
• Incorporation of the small main group
  element boron into the structure of one of the
  densest elements - osmium - via solid state
  synthesis yields osmium diboride, OsB2. This
  compound maintains the high valence electron
  density of osmium that provides remarkable
  incompressibility (resistance to elastic
  deformation) while also enabling short,
  directional covalent bonds to form. These
  covalent bonds limit the mobility of
  dislocationsin other words, the degree to which
  the planes of osmium atoms can slide past each
  other, thereby increasing the hardness
  (resistance to plastic deformation) of the
  material.
• The bulk modulus (incompressibility) of OsB2
  (365-395 GPa) rivals diamond (442 GPa) as
  measured in collaboration with Prof. Sarah
  Tolbert as we report in the J. Amer. Chem. Soc.,
  127, 7264, 2005. Qualitative hardness testing
  indicates that OsB2 scratches a sapphire window,
  placing it between 9 (sapphire) and 10 (diamond)
  on the Mohs hardness scale. Quantitative
  hardness testing using a nanoindentation
  technique is now in progress.

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Designing Ultra-incompressible, Superhard
MaterialsRichard B. Kaner, UCLA, DMR-0453121