STRUCTURAL-PROPERTIES OF DIAMOND FINE PARTICLES AND CLUSTERS PREPAREDBY DETONATION AND DECOMPOSITION OF TNT

The thermal parameter B for three different particle sizes of diamond samples (bulk powder 1-4 mu m, fine particle 144-195 A and cluster 55- 61 Angstrom) was determined by the grazing incidence X-ray diffraction method. The values of B were found to be in the ranee 0.50-0.70 Angst rom(2) For particles in the size range 195-55 Angstrom and 0.27 Angstr om(2) for 1-4 mu m. All of them are larger than that of diamond bulk. A clear size dependence of B. increasing with decreasing particle size , was found. By analysing X-ray diffraction data at several temperatur es the magnitude of B was found to be due to B-S (static part) instead of B-T (dynamic part). The average B, values obtained were 0.04 Angst rom(2), 0.19 Angstrom(2) and 0.27 Angstrom(2) for bulk powder, fine pa rticle and cluster samples respectively. Ultrahigh resolution transmis sion electron microscope (TEM) observation confirmed the presence of s train, distortion, roughness and dislocation lines in many particles. TEM images of particles indicate that the clusters were not spherical in shape: they were mostly cubiform and some were truncated prism-like polyhedral. The present study reveals that the B,component is respons ible for the large B value in diamond fine particles and clusters. No clear surface local atomic distortion was found in the particles. (C) 1998 Elsevier Science B.V.