Use of Niobium Oxide as a Binder in the Production of Diamond Nanostructured Composites

Abstract

The sintering of nanodiamond powders is of interest for both applied engineering of tool materials and fundamental materials science of nanodisperse covalent-type ceramic materials. It is a accept as a general notion that the driving force for sintering of monophase particles is determined by the level of the surface energy. In the case of diamond nanopowder, this level must be significantly higher which makes sintering a difficult process. This difficulty of sintering is connected with the low diffusive mobility of carbon causing the formation of a graphite structure onto surface of the diamond crystals. From this point of view the use of niobium oxide as a binder could be a solution. In an attempt to inhibit the diamonds graphitization process, Nb2O5 and small amounts of amorphous carbon were introduced in the reaction zone. Sintering process was conducted at 6.0 GPa of pressure and 1100-1400oC for a processing time of 30 seconds. At the end of the process, the samples were cleaned, and prepared to be characterized by X-ray diffraction, scanning electron microscopy, density and porosity. From these results it was proposed a densification mechanism based on the consolidation of the particle by diffusion and coalescence of clusters.