Preparation of nano-size ZrB2 powder by self-propagating high-temperature synthesis

Preparation of nano-size ZrB2 powder by SHS has been investigated. Zr and B elemental powders were mixed with 10-50 wt.% NaCl, and prepared pellets were reacted under argon. Adiabatic temperatures were calculated by HSC software. Increasing NaCl content led to a continuous decrease in adiabatic temperatures and reaction wave velocity. Products were subjected to XRD, SEM and FESEM analyses. Average crystallite size of ZrB2, which was 303 nm without NaCl, decreased to 32 nm with 40% NaCl addition. Distinct decrease in ZrB2 particle size was also observed from SEM analyses. 30% NaCl addition was found to be optimum for ensuring a stable SHS reaction and providing the formation of nano-size ZrB2 particles. It was revealed from particle size distribution measurements that ZrB2 powder obtained by 30 wt.% NaCl addition contained particles mostly finer than 200 nm. A mechanism, similar to solution-precipitation was proposed for the particle size refining effect of NaCl.