Sintering of ultrafine zirconium diboride powder prepared by modified SHS technique

Pressureless sintering of ultrafine zirconium diboride ZrB2 powder produced by a self-propagating high temperature synthesis (SHS) route was investigated at 1973-2223 K with continuous flow of pure argon gas (20 mL min(-1)). Ultrafine ZrB2 powder produced by the addition of an inert SHS diluent showed excellent sinterability, and a maximum densification of 97.5% was observed at 2223 K. In contrast, the identically sintered diboride powder produced without the addition of SHS diluent showed only 81.2% densification. The apparent activation energy for sintering was found to vary with particle size from around 37 to 43 kJ. Boron diffusion through ZrB2 is likely the rate controlling factor for the sintering reaction.