Graphitic Carbon in the Allende Meteorite: A Microstructural Study

Abstract

High-resolution transmission electron microscopy, shows that carbon in the Allende carbonaceous chondrite meteorite is predominantly a poorly crystalline graphite. Such material is of interest as an important carrier of the isotopically anomalous noble gases found in carbonaceous chondrites.

Carbonaceous contaminants on support films for transmission electron microscopy

“…In 1981, Smith and Buseck reported the Oken Shoji grids, and for helpful discussions. TEM studies of carbon extracted from the Allende meteorite [9]. Among the structures they described were carbon nanoparticles with outer diameters of the order of 30-50 References nm, which were very similar in appearance to those shown in Fig.…”

Terrestrial and Extraterrestrial Fullerenes

“…Allende is exceptional because the element is a poorly ordered carbon, characterized from studies by transmission electron microscopy as ''glassy carbon''. [60,61] A more recent TEM study of Allende carbon supports this finding and reports the abundant occurrence of ''carbon black-like particles'' Vis et al [62] Taken together these observations suggest that Allende carbon formed by pyrolysis of hydrocarbons and polymeric hydrocarbons, in part in a gas phase, in part perhaps on hot mineral surfaces. Such a scenario for the formation of fullerenes is not too outlandish when one considers that fullerenes have been synthesized by the pyrolysis of naphtalene [63] and by the consecutive=multiple cyclodehydrogenation of even more complex trimerized PAHs.…”

An attempt to characterize phase Q: Noble gas, Raman spectroscopy and transmission electron microscopy in residues prepared from the Allende meteorite

“…TEM images of original HF-HCl residues of Allende, documented in previous scientific contributions, show curved and tangled graphene sheets, with fringe distances of approximately 0.385 nm (Smith and Buseck, 1981;Harris et al, 2000;Vis et al, 2002;Harris and Vis, 2003). The increase above the 0.337 nm of the pure graphite stacking was attributed to turbostratic stacking.…”

“…This observation indicates that the oxidation affected the underlying carbon structure and did not simply dissolve a specific kind of carbon material out of the HF-HCl residue. The change in sample characteristics resulting from aggressive acid digestion have been described in previous contributions (Smith and Buseck, 1981;Garvie and Buseck, 2004).…”