64th Annual Meteoritical Society Meeting (2001) 5029.pdf

CARBON ALLOTROPY AND CARBON DUST IN THE CIRCUMSTELLAR AND INTERSTELLAR SPACE. F. Cataldo1 and Y.Keheyan2, 1Soc. Lupi arl, Chemical Research Institute, Via Casilina 1626/A, 00133 Rome, ITALY (e-mail [email protected]), 2Istituto di Chimica Nucleare, CNR, Monterotondo Stazione, 00016, Rome, Italy.

Introduction: In this paper we would like to present a complete review concerning our knowledge about the chemical structure of all the known carbon allotropes. The carbon allotropes [1] known to date include both graphite and diamond but also fullerenes and their polymers [2,3], onion-like carbon and carbon nanotubes [4], carbyne [5-7] as well as disordered structures such as disordered graphite and diamond-like carbon, nanocrystalline carbon commonly known as carbon black. In relation to the carbon dust present in the circumstellar and interstellar space we will discuss about the dust in terms of the chemical structure of the carbon allotropes, and in terms of the formation mechanisms as well as the mechanisms through which each allotropic form can convert into another form under the action of thermal [8] events as well as under the action of high energy radiation [4].

We will enter insight the known chemical structure of thermal and furnace carbon black which are the most likely candidates to be also the main components of the circumstellar and interstellar carbon dust.

We will discuss about the stability of C60 and C70 fullerene in the interstellar and circumstellar space on the basis of the results of very recent studies about their irradiation in the solid state with UV and radiation [9]. We will show how reasonably carbyne, long chain polyynes, cyclopolyynes and derivatives may exist in the interstellar space and can condense into solid grains. Additionally, we would like to introduce the concept of fullerene-like structure in a graphene sheet [1,10-12]; this concept is linked to the recent discovery of these defective structures in common commercially available carbon blacks [11]. The presence of these fullerene-like structures which can be described as pentagonal or heptagonal rings inserted into a series of condensed hexagonal rings, change completely the surface chemistry of the grains containing these defects [10].

References: [1] Cataldo F. (2001) Kautschuk Gummi Kunststoffe, 54, 22–28. [2] Cataldo F. (1999) Polym. Internat., 48, 143-149. [3] Cataldo F. (2000) Eur. Polym. J. , 36, 653-656. [4] Cataldo F. (2000), Carbon, 38, 634-636 [5] Cataldo F. (1999) Carbon, 37, 161-163. [6] Cataldo F. and D.Capitani (1999) Mater. Chem. Phys., 59, 225-231. [7] Cataldo F. (1997) Polym. Internat., 44, 191–200. [8] Cataldo F. and Y. Keheyan (2001) Fullerene Sci. Technol., accepted for publication. [9] Cataldo F. (2000) Fullerene Sci. Technol., 8, 577-593. [10] Cataldo F. (2000) Fullerene Sci. Technol., 8, 105-112. [11] Donnet J.B. editor (2000) Proceedings of the 3rd International Carbon Black Conference, 25-26 October, Mulhouse, France. [12] Cataldo F. (2001) Carbon, accepted for publication.