Morphology evolution of ZrB2 nanoparticles synthesized by sol–gel method

Zirconium diboride (ZrB2) nanoparticles were synthesized by sol–gel method using zirconium n-propoxide (Zr(OPr)4), boric acid (H3BO3), sucrose (C12H22O11), and acetic acid (AcOH). Clearly, it was a non-aqueous solution system at the very beginning of the reactions. Here, AcOH was used as both chemical modifier and solvent to control Zr(OPr)4 hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C12H22O11 was selected, since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. Furthermore, we investigated the influence of the gelation temperature on the morphology of ZrB2 particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 °C to a particle chain at 75 °C, and then form rod-like particles at 85 °C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB2 were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB2 related to the gelation temperature obeyed the “oriented attachment mechanism” of crystallography.

Graphical AbstractIncreasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 °C to a particle chain at 75 °C, and then form rod-like particles at 85 °C.Figure optionsDownload as PowerPoint slideHighlights
► ZrB2 nanoparticles were synthesized by sol–gel method in an non-aqueous solution system.
► AcOH was used as both chemical modifier and solvent to control Zr(OPr)4 hydrolysis.
► C12H22O11 was selected since it can be completely decomposed to carbon.
► Increasing the gelation temperature, the particles changed from sphere-like to rod-like ones.
► Crystalline nature of ZrB2 obeyed the “oriented attachment mechanism” of crystallography.