@article{eaca14fd5e744e21b005f2a24a9fa3e5,
title = "Genesis of presolar diamonds: Comparative high-resolution transmission electron microscopy study of meteoritic and terrestrial nano-diamonds",
abstract = "Nano-diamonds isolated from acid dissolution residues of primitive carbonaceous meteorites (Allende and Murchison) were studied using high-resolution transmission electron microscopy. To discriminate among their most likely formation mechanisms, high-pressure shock-induced metamorphism or low-pressure vapor condensation, the microstructures of presolar diamond crystallites were compared to those of (terrestrial) synthesized nano-diamonds. The synthesized diamonds used for comparison in this study were produced by high-pressure shock waves generated in controlled detonations and by direct nucleation and homoepitaxial growth from the vapor phase in low-pressure chemical vapor deposition (CVD)-type processes. Microstructural features were identified that appear unique to shock metamorphism and to nucleation from the vapor phase, respectively. A comparison of these features to the microstructures found in presolar diamonds indicates that the predominant mechanism for presolar diamond formation is a vapor deposition process, suggesting a circumstellar condensation origin. A new presolar grain component has also been identified in the meteoritic residues, the (2H) hexagonal polytype of diamond (lonsdaleite).",
author = "Daulton, {T. L.} and Eisenhour, {D. D.} and Bernatowicz, {T. J.} and Lewis, {R. S.} and Buseck, {P R}",
note = "Funding Information: Acknowledgments--The dynamic shock synthesized nano-diamonds were kindly provided by N. Greiner, Los Alamos National Laboratory, Los Alamos, New Mexico 87545. The substrateless vapor-phase nucleated nano-diamonds were kindly provided by W. Howard and M. Frenklach, Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802. The Murchison X residues were kindly prepared by Xia Gao of the McDonnell Center for the Space Sciences, Washington University in St. Louis. The high-resolution transmission electron microscopy was initially performed at the National Center for High-Resolution Electron Microscopy at Arizona State University, which is supported by the National Science Foundation under grant DMR-9314326. The majority of this research including all of the HRTEM image and data analysis, as well as additional TEM work, were performed at the McDonnell Center for the Space Sciences. TLD thanks Washington University for support and facilities without which this research could not have been completed. The authors thank Robert Walker for his kind support and encouragement. The authors also thank the manuscript referees L. Keller, C. Alexander, and an anonymous reviewer for their comments and criticisms. This research was partially funded by the following sources: private funds of TLD, (TJB) NASA grant NAGW-3371, (TJB) NSF grant EAR 931 6328, (RSL) NASA grant NAGW-3342, and (TLD and PRB) NSF grant EAR 921 9376. PRB would like to acknowledge NASA grant NAGW-3386.",
year = "1996",
month = dec,
doi = "10.1016/S0016-7037(96)00223-2",
language = "English (US)",
volume = "60",
pages = "4853--4872",
journal = "Geochimica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Limited",
number = "23",
}