RECENT DISCOVERIES IN CARBON BLACK FORMATION AND MORPHOLOGY AND THEIR IMPLICATIONS ON THE STRUCTURE OF INTERSTELLAR CARBON DUST

Abstract

In this review we discuss about the presence of carbon under the form of dust grains and organic molecules in the interstellar and circumstellar medium. The spectral evidences about the presence of these carbon-based dust and molecules in the space is also reviewed. We would like to emphasise that the molecules present in space, namely polyyne chains and rings, polycyclic aromatic hydrocarbons and fullerenes which are the precursors of the formation of interstellar carbon dust have been also detected by in situ mass spectrometry in ordinary flames and in the carbon arc formed between graphite electrodes under special conditions. Thus the mechanism which lead to soot formation in a flame should be similar to that leading to carbon dust in space. In fact, the morphology of the carbon black produced industrially by furnace process or by thermal decomposition appears very close to the morphology of carbon dust produced under conditions which should simulate the circumstellar conditions. In both cases curved graphene sheets can be observed together with onion-like particles and defective structures which we have defined fullerene-like structures. The presence of these structures may affect the surface chemistry of the carbon dust grains by enhancing the electron affinity in comparison to graphite.