STRUCTURAL CHARACTERIZATION OF COMBUSTION SYNTHESIZED MOSI2-SI3N4 COMPOSITE POWDERS AND PLASMA-SPRAYED MOSI2-SI3N4 COMPOSITES

A systematic structural characterization has been conducted on combust ion synthesized MoSi2-Si3N4 powders and plasma sprayed composites by t ransmission electron microscopy (TEM). The powders are cleaner and wit h little surface oxide contamination than most commercial powders. The distribution of the two phases can be tailored by modifying the synth esis conditions, which has resulted in improved retention of Si3N4 aft er plasma spraying. TEM studies performed on deformed composites indic ate a strong link between even dispersion of second phases and enhance d dislocation plasticity in the plasma sprayed composites.