Abstract
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Reactive ball milling, using the magneto-mechanochemical method, was performed on silicon in an ammonia atmosphere. X-ray analysis and transmission electron microscopy revealed a nanostructural product, confirmed by energy dispersive spectroscopy to comprise predominantly Si and N. Various combinations of powder/binder (Y2O3 binder, MgO binder) were pressed and rapidly sintered under Argon in an induction heated graphite crucible. Sintered pellets, which were examined using XRD, SEM-EDS, and DTA, were found to comprise Si3N4 with minor amounts of FeSi and binder phases. The densities of the products were high in comparison to those of conventionally prepared Si3N4, and the hardnesses, obtained using ultra-micro indentation, were found to be in the highest possible range for Si3N4. Preliminary studies of the production of Si3N4 from nanostructural powder using no binder also gave promising results, with sintered pellets of density and hardness equivalent to that currently achieved using conventional production techniques with binders. The exceptional sintering properties were attributed to the particular nanostructural form of the milled powder.