Formation of zirconium diboride nanoparticles as a result of reaction between zirconium tetrachloride and sodium borohydride

We have studied reaction between ZrCl4 and NaBH4 at temperatures between 300 and 725°C. The results demonstrate that single-phase zirconium diboride nanoparticles are formed starting at 575°C. According to electron microscopy data, the ZrB2 powder obtained at 575 and 725°C consists of variously shaped particles, some of which are almost spherical, ranging in diameter from ~10 to 20 and from 25 to 35 nm, respectively. These values agree with the equivalent particle diameters evaluated from the measured specific surface area of ZrB2, ~14 and ~32 nm, respectively, and with the crystallite size extracted from X-ray diffraction data: Dhkl ~ 13 and 28 nm.