Mv. Baidakova et al., Ultradisperse-diamond nanoclusters. Fractal structure and diamond-graphitephase transition, CHAOS SOL F, 10(12), 1999, pp. 2153-2163
A systematic study of the diamond graphite structural phase transition in u
ltradisperse-diamond clusters obtained by the detonation technique is repor
ted. Samples of two types, differing in the kinetics of detonation-product
cooling, were investigated. The phase transition was achieved under heating
in an inert atmosphere in the temperature range 720-1400 K. X-ra character
ization showed the ultradisperse-diamond, irrespective of the cooling rare
used, to be a cluster material possessing a diamond structure with a charac
teristic nanocrystal size of 44 Angstrom. The diamond graphite structural p
hase transition in ultradisperse diamond is shown to start from the cluster
surface inwards at T-pt approximate to 1200 K, i.e., at substantially lowe
r temperatures than is the case with bulk diamond single crystals. Ultradis
perse-diamond clusters are shown to be fractal objects and the character of
variation of the fractal dimension in the course of the diamond-graphite p
hase transition is studied. (C) 1999 Elsevier Science Ltd. All rights reser
ved.