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Nucleation, Growth, Annealing, and Coagulation of Refractory Oxides and Metals: Recent Experimental Progress and Applications to Astrophysical SystemsStarting with cooling, refractory vapors diluted in significant quantities of H and He there are four processes that most natural systems will undergo: nucleation, growth, annealing, and coagulation. Nucleation is the processes by which the first stable refractory nuclei form in the vapor. These are the seeds onto which the remaining vapors will condense during the growth stage. Solids of any composition will try to arrange themselves into the least energetic configuration, provided that there is sufficient energy available to support such processes as diffusion and the breaking of chemical bonds. There is a significant activation energy associated with the annealing process in refractory solids due to the relatively high energy of the chemical bonds in solids. The grains formed in most cosmochemical systems are extremely small and often tightly coupled to the gas. Because of their small physical cross sections coagulation may be a very slow process unless there is another driving force involved in addition to normal Brownian motion. In what follows we will briefly cover each of these four stages for refractory oxide and metal grains, although in inverse order.
Document ID
19990091980
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Nuth, J. A.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Rietmeijer, F. J. M.
(New Mexico Univ. Albuquerque, NM United States)
Hallenbeck, S. L.
(NASA Headquarters Washington, DC United States)
Withey, P. A.
(West Virginia Wesleyan Coll. Buckhannon, WV United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Workshop on Thermal Emission Spectroscopy and Analysis of Dust, Disk, and Regoliths
Subject Category
Astrophysics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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