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6Carbon nanostructures
CHANGING OF A SYNTHETIC DIAMOND STRUCTURE UNDER THE LONG-PULSE EXPLOSIVE LOADING
A. A. Shtertser1, A. A. Deribas2, P. A. Simonov3, V. N. Filimonenko4
1 MATEM Co. Ltd., Novosibirsk, 630058, fax: (383-2) 33-71-22, e-mail: matem@mail.nsk.ru 2 Lavrent'ev Institute of Hydrodynamics, Novosibirsk, 630090
3Boreskov Institute of Catalysis, Novosibirsk, 630090 4 Novosibirsk State Technical University, Novosibirsk, 630063
A series of experiments on the explosive loading of diamond powders «Mipolex» commercially produced by Du Pont de Nemour Company was performed. The initial powders were of two types characterized by the particle sizes 9 and 30 mm. The particles were polycrystals with a crystallite size of no more then 10 nm.
In order to avoid cracking in compacts and to minimize graphitization of diamond impulsive loading with relatively low pressure (<10 GPa) and with prolonged pulse duration (> 170 msec) was used in the experiments. For this purpose special recovery containers were designed, and two- and three-layered explosive charges with total mass varied from 65 to 760 kg were used.
Characterization of the obtained samples included measuring of their density and porosity, microhardness measurements, optical microscopy, scanning electron microscopy, high-resolution electron microscopy, X-ray analyses and etc.
It was found that the following forms of carbon are present in the obtained compacts: diamond, graphite, closed-curved graphite-like structures, carbon nanotubes, amorphous carbon, and carbon phase with carbide-like atomic bonds. Besides, 40 nm diamond monocrystals were observed in compacts, and this allows us to suggest that initial crystallites of which polycrystal particle consist can grow during impulsive loading.
It is significant that under the dynamic pressure of 10 GPa a sample with hardness 28 GPa was obtained. To get such a result another researches have applied to diamond powder dynamic pressures which exceed 70 Gpa, but with short pulse duration of 1,5 msec. In our opinion the prolonged time of loading provides the favourable conditions for formation of the above mentioned carbon structures as well as for growing of diamond crystallites and increasing of bonds between them, even if the applied pressure is reduced significantly.
ISJAEE Special issue (2003)
