Synthesis of ZrB2 nanoparticles by sol-gel method

Zirconium diboride (ZrB 2 ) nanoparticles were synthesized by sol-gel method using zirconium n -propoxide (Zr(OPr) 4 ), boric acid (H 3 BO 3 ), and sucrose (C 12 H 22 O 11 ). Additionally, acetylacetone ( acac ) was used as chemical modifier in a neutral condition to stabilize Zr(OPr) 4 which hydrolyzes easily. Here, C 12 H 22 O 11 was used since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. A single phase ZrB 2 without residual ZrO 2 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 ZrB 2 nanoparticles was ca. 50 nm. The photomicrograph revealed a spherical round shape morphology of the ZrB 2 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 -ZrO 2 and t -ZrO 2 phases besides ZrB 2 .