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Paper: Nucleation, Growth, Annealing and Coagulation of Refractory Oxides and Metals: Recent Experimental Progress and Applications to Astrophysical Systems
Volume: 196, Thermal Emission Spectroscopy and Analysis of Dust, Disks, and Regoliths
Page: 313
Authors: Nuth, Joseph A.; Rietmeijer, Frans J. M.; Hallenbeck, Susan L.; Withey, Paul A.; Ferguson, Frank
Abstract: Starting with cooling, refractory vapors diluted in significant quantities of hydrogen and helium there are four processes that most natural systems will undergo: nucleation, growth, annealing and coagulation. Although the nucleation of refractory grains remains something of an enigma, there has been considerable progress in our understanding of grain growth, annealing and coagulation over the past few years. Grain growth has been shown to produce amorphous solids of predictable composition. The rate and activation energy for the annealing of at least one type of amorphous condensate has been measured and has been applied to model the conditions leading to the observation of crystalline magnesium silicate grains by ISO. Finally, there is experimental evidence that magnetically induced grain coagulation could be an important and very widespread process in protostellar systems that might have a number of observable signatures both in meteoritic materials and via astronomical observations. We are far from quantitative understandings of any of the above processes, but are poised for considerable progress in the near future given a continuation and extension of the recent trend of successful laboratory experiments described herein.
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