Elaboration of SiC, TiC and ZrC nanopowders by laser pyrolysis : from nanoparticles to ceramic nanomaterials

Considerable effort is devoted to the synthesis of refractory carbide ceramics as promising materials for high-temperature applications, such as structural materials for the future generation of nuclear reactors. In this context, nanostructured ceramics are expected to exhibit interesting behavior under irradiation as compared with conventional materials. We report on the synthesis of SiC, TiC, and ZrC nanopowders by laser pyrolysis. The powders were characterized by X-ray diffraction, BET specific surface measurements, scanning electron microscopy, and transmission electron microscopy. SiC nanopowders were obtained from the decomposition of a mixture of silane and acetylene and were composed of grains varying in size from 7.2 to 43.0 nm. Liquid precursors were laser pyrolyzed with ethylene as a sensitizer in order to synthesize Ti-C-O or Zr-C-O powders. Annealing treatments in an argon atmosphere enabled the formation of 45-nm TiC grains or 38-nm ZrC grains through the carburization of the oxide phase by free carbon. Nanocrystalline ceramics were elaborated from SiC or TiC powders by very high pressure (8 GPa) sintering without any sintering additives. The densification reached 94% for SiC and 80% for TiC, without significant grain growth