Thermal Transformation of Diamond

From the detonation of carbon-rich explosives, diamonds with primary particles measuring about 5 nm can be obtained. Electron microscopic examination also reveals graphitic portions of the material that partly exist as onion-hke structures or as multilayered graphitic shells on the diamond particles (Section 5.2.2). Hence, it seems reasonable to assume that a complete graphitization of detonation diamond leads to onion-like particles. 

Altogether the thermal transformation of nanodiamond turned out a suitable method to prepare macroscopic amounts of onion-like carbon. It is true that the products obtained are inhomogeneous to some extent and that the resulting onions show various deficiencies (defects, deviations from spherical shape), but still the heating of diamond in vacuo constitutes the best method to date to generate larger amounts of carbon onions and study in principle their physical and chemical properties. 

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