Enhanced solid-state reaction kinetics of shock-compressed titanium and carbon powder mixtures

Abstract

The effect of shock compression on the solid-state chemical reactivity of titanium and carbon powder mixtures was investigated with the objective of forming net-shaped TiC ceramics with a fine-grain microstructure. The combination of defect states and intimate interparticle contacts introduced during shock compression results in significant enhancement of the otherwise sluggish solid-state diffusion of Ti and C through the TiCx boundary layer. The apparent activation energy for TiCx formation 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 (˜85% dense) were reaction synthesized via solid-state diffusion, producing microstructures with grain size <6 μm and microhardness of ˜2000 kg/mm2, in contrast to statically pressed powder compacts which reacted by a combustion process resulting in a highly porous product.