Dynamic synthesis of diamonds

Nanometer-size diamonds were produced by firing of high explosive mixtures in water confinement. This simple method avoids the use of inert gas and is efficient enough to prevent the oxidation and graphitization of recovered diamonds. Studies of thermal and luminous phenomena were performed to examine eventually post-combustion phase. Condensed carbon yields of 30-55% were achieved for different explosive compositions, some of them containing metallic, carbonaceous or organic additives. For all the experiments, the presence of a diamond phase was revealed by X-ray diffraction, SEM, and TEM. To remove materials still unconverted to diamond, various selective oxidation treatments (with KNO3/KOH, H2O2/HNO3 mixtures) were carried out, leading to light gray ultradispersed diamond aggregates with a yield up to 60%. Otherwise, shock wave compression synthesis of diamond has been realized by using a planar impact system at 2 km/s. Compressed carbon products were obtained from several carbon precursors (graphite, carbon black, fullerenes, organic substances, ...) mixed with a diverse metal matrix which acts as a cooling agent and stops the process of retro-graphitization. XRD analysis shows that diamond can be produced from many carbon materials with quenching as well as appropriate pressures and temperatures. (C) 2000 Elsevier Science S.A. All rights reserved.