free web permotion

here you can find new and old information of diamond


free counters

Wednesday, June 17, 2009

Material properties of diamond

Diamond is the allotrope of carbon where the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is an optically isotropic crystal that is transparent to opaque. It is the hardest naturally occurring material known, due to its strong covalent bonding, yet its toughness is only fair to good due to important structural weaknesses. The precise tensile strength of diamond is unknown, however strength up to 60 GPa has been observed, and it could be as high as 90-225 GPa depending on crystal direction.[1] The anisotropy of diamond hardness is carefully considered during diamond cutting. Diamond has a high refractive index (2.417) and moderate dispersion (0.044) properties which give cut diamonds their brilliance. Scientists classify diamonds into two main types, I and II, and four subtypes (Ia, Ib, IIa and IIb), depending on the nature of crystallographic defects present. Trace impurities substitutionally replacing carbon atoms in a diamond's crystal lattice, and in some cases structural defects, are responsible for the wide range of colors seen in diamond. Most diamonds are electrical insulators but extremely efficient thermal conductors. The specific gravity of single-crystal diamond (3.52) is fairly constant. Contrary to a common misconception,[by whom?] diamond is not the most stable form of solid carbon; graphite has that distinction.


DIAMOND © 2007 Template feito por Áurea R.C.