Transmission Electron Microscopy of Non-etched Presolar Silicon Carbide
نویسندگان
چکیده
Rhonda M. Stroud, Larry R. Nittler, Conel M. O’D. Alexander, Thomas J. Bernatowicz and Scott R. Messenger, Naval Research Laboratory, Code 6371, 4555 Overlook Avenue NW, Washington, DC 20375 ([email protected]), Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015, Laboratory for Space Sciences, Washington University, 1 Brookings Drive, St. Louis, MO 63130.
منابع مشابه
Polytype distribution of circumstellar silicon carbide: Microstructural characterization by transmission electron microscopy
Silicon carbide (SiC) is a particularly interesting species of presolar grain because it is known to form on the order of a hundred different polytypes in the laboratory, and the formation of a particular polytype is sensitive to growth conditions. Astronomical evidence for the formation of SiC in expanding circumstellar atmospheres of asymptotic giant branch (AGB) carbon stars is provided by i...
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The inferred crystallographic class of circumstellar silicon carbide based on astronomical infrared spectra is controversial. We have directly determined the polytype distribution of circumstellar SiC from transmission electron microscopy of presolar silicon carbide from the Murchison carbonaceous meteorite. Only two polytypes (of a possible several hundred) were observed: cubic 3C and hexagona...
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Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in ...
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