ENHANCED SOLID-STATE REACTION-KINETICS OF SHOCK-COMPRESSED TITANIUM AND CARBON POWDER MIXTURES

The effect of shock compression on the solid-state chemical reactivity of titanium and carbon powder mixtures was investigated with the obje ctive of forming net-shaped TiC ceramics with a fine-grain microstruct ure. The combination of defect states and intimate interparticle conta cts introduced during shock compression results in significant enhance ment of the otherwise sluggish solid-state diffusion of Ti and C throu gh the TiCx boundary layer. The apparent activation energy for TiCx fo rmation was determined using solid-state reaction kinetics models, and was found to be reduced by four-to-six times that of diffusion of Ti into TiCx and two-to-three times that of diffusion of C in TiCx. As a result, net-shaped sections of shock-densified compacts (similar to 85 % dense) were reaction synthesized via solid-state diffusion, producin g microstructures with grain size <6 mu m and microhardness of similar to 2000 kg/mm(2), in contrast to statically pressed powder compacts w hich reacted by a combustion process resulting in a highly porous prod uct.