4. Conclusions
In summary, a convenient method has been successfully applied to prepare nanocrystalline ZrB2 by reacting ZrCl4 with NaBH4 in an autoclave in the temperature range of 500–700 °C. The high temperature and pressure are beneficial to the crystallinity and increased crystallite size of the samples. The prepared ZrB2 at 700 °C for 12 h exhibits 10–20 nm particles. The UV–vis absorption spectrum of the ZrB2 nanocrystallites shows the onset of absorption at about 264 nm. The prepared nanocrystalline ZrB2 at 700 °C begins to be oxidized rapidly from 525 °C.