where x, y, k and m are moles of Zr, B, ZrB2 and B51Zr, respectively. It has been observed that the synthesized powder contains very negligible amount of Mg, which is ignored here. We consider here that MgO content of SHS powder is negligible and the source of oxygen is due to presence of ZrO2 phase only. There is no change of Zr content of leached and unleached powder, which indicates ZrO2 does not form solid solution with MgO during synthesis. The TEM images show the presence of mainly spherical particles and the average particle size of the product seems to decrease from 125 nm to 75 nm upon addition of 20 wt% NaCl to the reaction mixture ( Fig. 2). This indicates particle size decreases due to addition of NaCl. During synthesis, the NaCl partially melts and vaporizes and gives a coating on ZrB2 particle, which reduces the grain growth of particle. The decrease of adiabatic temperature (Tad) due to NaCl addition is responsible for reduction of grain growth. The calculation of adiabatic temperature of Eq. (1) is given below: