From: Paul Doherty (pauld@exploratorium.edu)
Date: Sat Apr 13 2002 - 15:09:36 PDT
Message-Id: <l03110729b8de5d135256@[192.174.3.125]> Date: Sat, 13 Apr 2002 15:09:36 -0700 From: Paul Doherty <pauld@exploratorium.edu> Subject: Osmium Resists the Squeeze
>
>
>http://sciencenow.sciencemag.org/cgi/content/full/2002/408/1
>
> 8 April 2002
>
> Osmium Resists the Squeeze
>
>Look to the tip of your fountain pen, not your jewelry, for the most
>incompressible material known. The exotic metal osmium, used in alloy form
>in some pen nibs and surgical needles, is even harder to squash than
>diamond, says a team of high-pressure physicists. The finding could open up
>a new path in the hunt for superhard materials, the researchers say.
>
> Osmium's résumé already singles it out as something special. One of the
>platinum metals, osmium is the densest naturally occurring element, almost
>twice as dense as lead, and has a stratospheric melting point in the same
>league as that of the tungsten used for lightbulb filaments. It's also very
>hard. But Hyunchae Cynn and his colleagues at Lawrence Livermore National
>Laboratory in California noticed that theoretical estimates of osmium's
>compressibility were unaccountably low. Because no one had ever bothered to
>actually measure osmium's compressibility, Cynn and his team decided to
>take things into their own hands.
>
> The team crushed a sample containing tiny crystals of osmium and liquid
>argon between the jeweled jaws of a diamond anvil, which exerts several
>hundred tons per square centimeter of pressure. As the researchers racked
>up the pressure, they used x-ray diffraction to watch how the spacing
>between osmium atoms narrowed. "We were quite surprised," says Cynn. Osmium
>turned out to be less compressible than diamond, the existing record
>holder, the team reports in the 1 April issue of Physical Review Letters.
>
> "It's stunning that such an incompressible element is only now
>recognized," says Raymond Jeanloz of the University of California,
>Berkeley. "The additional surprise is that a metal could be so
>incompressible." Diamond had always been assumed to be a special case
>because of its particular bonding pattern, which is much more rigid than
>the way atoms of a metal are held together, Jeanloz explains. Although
>diamond retains its title as hardest substance because of its additional
>ability to resist any attempt to slide, or shear, one face parallel to
>another, Cynn says osmium's low compressibility hints at a new class of
>superhard materials.
>
> --ANDREW WATSON
>
> Related site
>
><http://www-phys.llnl.gov/Organization/HDivision/HighPressureGroup.html>Lawrenc
>>e Livermore High-Pressure Physics Group
>
>
>
>ScienceNOW -- Watson 2002 (408): 1
>Copyright © 2002 by the American Association for the Advancement of Science.
>
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