An Electron-Microscope Study of Shock-Synthesized Diamond

The microstructure of diamonds formed from the graphite in cast iron by an explosive shock process was investigated by means of transmission electron microscopy electron, diffraction, and selected beam microscopy. Morphologically, the material consists of a mixture of two different forms: compact aggregates of of usually acicular crystallites with a strong preferred orientation, and single crystals. The latter partly consist of hexagonal diamond, the recently discovered modification of carbon, and contain many stacking faults. Hexagonal diamond is also randomly distributed in the polycrystalline fraction.