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 (C₁₂H₂₂O ₁₁). 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.