Structural properties of diamond fine particles and clusters prepared by detonation and decomposition of TNT

The thermal parameter B for three different particle sizes of diamond samples (bulk powder 1–4 μm, fine particle 144–195 Å and cluster 55–61 Å) was determined by the grazing incidence X-ray diffraction method. The values of B were found to be in the range 0.50–0.70 Å² for particles in the size range 195–55 Å and 0.27 Å² for 1–4 μm. 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 temperatures the magnitude of B was found to be due to B_S (static part) instead of B_T (dynamic part). The average B_S values obtained were 0.04 Å², 0.19 Å² and 0.27 Å² for bulk powder, fine particle and cluster samples respectively. Ultrahigh resolution transmission electron microscope (TEM) observation confirmed the presence of strain, 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_S component is responsible for the large B value in diamond fine particles and clusters. No clear surface local atomic distortion was found in the particles.