Synthesis of ZrB2 nanoparticles by sol-gel method

Zirconium diboride (ZrB2) nanoparticles were synthesized by sol-gel method using zirconium n-propoxide (Zr(OPr)4), boric acid (H3BO3), and sucrose (C12H22O11). Additionally, acetylacetone (acac) was used as chemical modifier in a neutral condition to stabilize Zr(OPr)4 which hydrolyzes easily. Here, C12H22O11 was used since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. A single phase ZrB2 without residual ZrO2 was obtained with a molar ratio of B/Zr = 2.3 for the starting materials at 1,550 °C and the average grain size of ZrB2 nanoparticles was ca. 50 nm. The photomicrograph revealed a spherical round shape morphology of the ZrB2 nanoparticles with an uniform size distribution. On the other hand, in the case of either B/Zr (mol.) = 2.0 or pyrolyzing temperature below 1,550 °C for B/Zr (mol.) = 2.3, there existed both m-ZrO2 and t-ZrO2 phases besides ZrB2.