Subject: NSF Press Release
From: Dot Baker <[email-masked]>
To: [email-masked]
Date: Fri, 08 Nov 91 09:14 EST

Hi Paul,
   Please post to the NIH Listserver as:
     Filaments.911108
 ---------------------------- Text of forwarded message -----------------------
Title       : NEW TECHNIQUES PERMIT ANALYSIS OF MICROSCOPIC METAL
              FILAMENTS WITH SUPERCONDUCTING POTENTIAL
NSF Contact : OLPA
Type        : Press Release
Date        : September 18, 1991

 

 
Jeffrey Norris                             FOR IMMEDIATE RELEASE:
(202) 357-9498                                 September 18, 1991
                                                     NSF PR 91-83

       NEW TECHNIQUES PERMIT ANALYSIS OF MICROSCOPIC METAL
            FILAMENTS WITH SUPERCONDUCTING POTENTIAL

      Scientists have determined the crystalline structure of a
microscopic bismuth wire about one-tenth the width of a
bacterium.
     The filament, a single unbroken crystal, is the smallest
sample for which a structural determination has been made using
x-rays, according to National Science Foundation Science and
Technology Center researchers from the Carnegie Institution of
Washington, D.C.
     The scientists collaborated on a Naval Research Laboratory
project to make the structural determination, which is reported
in the September 6 issue of Science.
     "Theoretically," says Carnegie's Larry W. Finger, "a small
enough filament confined at high pressure could be a high
temperature superconductor."  Such superconductors are sought for
their potential to carry electricity without losing current to
electrical resistance.
     Although the structure reported in Science is not
superconducting, more recently the research group has been
studying another wire, about three times thinner.  This wire
 
-                             more-
-                                         2-
 
appears to exhibit a distinct but still undetermined crystalline
structure, Finger says.
 
     The Naval Research Laboratory team, led by Earl F. Skelton,
produces the wires by drawing out molten metal confined within a
glass capillary.  Upon cooling, the metal expands more than the
glass, increasing the pressure across the width of the solidified
filament.
 
     It should be easier to detect and measure conductivity and
other properties in the glass-encased metal than in diamond-anvil
setups, another powerful way to create new structures under high
pressure, Finger says.
 
     The Carnegie researchers are associated with the NSF Science
and Technology Center for High-Pressure Research, whose main
operations are located at the State University of New York, Stony
Brook.
 
     To determine the structure of the bismuth wire the
researchers used a particle accelerator, called a synchrotron,
located at Brookhaven National Laboratory.  High-energy electrons
from the synchrotron emitted x-rays, which were used to bombard
the bismuth.  X-rays diffracting off the microscopic wire formed
a pattern from which the scientists were able to determine
crystalline structure.
 
     The researchers employed a "wiggler," a series of seven
dipole magnets, to bend the electron beam up and down, thereby
causing the electrons to emit x-rays at the high brightness
necessary to resolve the structure of the small sample.
 
-                              end-
 
     National Science Foundation is an independent agency of the
Federal Government established in 1950 to promote and advance
scientific progress in the United States.  NSF accomplishes its
mission primarily by competitively awarding grants to educational
institutions for research and education in the sciences,
mathematics, and engineering.
 
..stis file is pr9183
..expires March 1992
 
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