Structural peculiarities of carbon onions, formed by four different methods: Onions and diamonds, alternative products of graphite high-pressure treatment

We attempted to find peculiarities or the carbon onion structure specific to onions synthesized by four different methods, three of them using high-pressure techniques, and to explain the lack of diamond particles. Within the framework of the theory of shell deformation. it was shown that the formation of diamond particles from onions requires the application or a much higher external pressure and the production of onions represents a dead-end branch of high-pressure graphite diamond transformations. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.