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X-ray snapshots of 'solid flame' events.



X-ray snapshots of 'solid flame' events

Put a match to the tip of a Fourth of July Fourth of July, Independence Day, or July Fourth, U.S. holiday, commemorating the adoption of the Declaration of Independence. Celebration of it began during the American Revolution.  sparkler spar·kler  
n.
1. One, such as a highly polished metallic surface or a virtuoso performer, that sparkles.

2. Informal A diamond.

3. A firework that burns slowly and gives off a shower of sparks.
. A dazzling display of light immediately begins inching down the shaft as the searing sear 1  
v. seared, sear·ing, sears

v.tr.
1. To char, scorch, or burn the surface of with or as if with a hot instrument. See Synonyms at burn1.

2.
 heat sparks successively lower regions into combustive action. Researchers have now recorded with unpecedented detail the rapid material changes that occur during related "solid flame" reactions lasting mere seconds or minutes.

For more than 20 years, materials scientists -- primarily in the Soviet Union -- have explored the chemistry, physics and technological promise of such reactions, also known as self-propagating, high-temperatur synthesis (SHS SHS Shares (stock)
SHS SAW (Surface Acoustic Wave) Humidity Sensor
SHS Sciences Humaines et Sociales (French: Social Sciences)
SHS Student Health Service
SHS Second Hand Smoke
) reactions. Already, researchers have harnessed these "solid flames" to process solid ingredients directly into metallic alloys, composite materials and even superconducting ceramics.

Using one of the world's most intense synchrotron radiation sources, at Brookhaven National Laboratory Brookhaven National Laboratory, scientific research center, at Upton (town of Brookhaven), Long Island, N.Y. It was founded in 1947 by Associated Universities, a management corporation sponsored by nine eastern U.S. universities.  in Upton, N.Y., a team led by Joe Wong of Lawrence Livermore (Calif.) National Laboratory has assembled crystallographic crys·tal·log·ra·phy  
n.
The science of crystal structure and phenomena.



crystal·log
 SHS snapshots. Scientists routinely compare starting ingredients against products formed after a reaction occurs. "But before synchrotron synchrotron: see particle accelerator.
synchrotron

Cyclic particle accelerator in which the particle is confined to its orbit by a magnetic field. The strength of the magnetic field increases as the particle's momentum increases.
 radiation, we never had the possibility of observing what happens during these [SHS] reactions," Wong says.

The researchers first compress combustible mixes -- say, titanium, carbon and nickel powders -- into blocks the size of ice cubes, which they place inside a crystallography chamber. Then they ignite the reaction as an intense beam of synchrotron X-rays bathes the sample. Detectors record the resulting diffraction patterns at intervals as brief as a tenth of a second. In a synchrotron, highly accelerated electrons copiously emit X-rays as they travel in bending paths.

In the Sept. 21 SCIENCE, the Livermore team displays several series of rapid X-ray diffraction scans taken both while and after the fast-moving reaction fronts of SHS reactions pass through samples. Viewed in sequence, these images indicate exactly when specific components undergo physical and chemical changes such as melting, crystallizing and forming alloys or ceramics.

SHS reactions can yield solid products requiring little postproduction machining and generate less waste material than conventional furnace processes, which take hours or days. Materials scientist James W. McCauley, dean of the New York State College of Ceramics The New York State College of Ceramics (NYSCC) at Alfred University in Alfred is a statutory college of the State University of New York (SUNY). It is divided into: the School of Art and Design, and the Programs of Ceramic engineering, Glass Engineering and Science, Materials  at Alfred University, says he expects the more detailed pictures of these reactions to help researchers design better SHS recipes.
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Author:Amato, I.
Publication:Science News
Date:Sep 22, 1990
Words:366
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