Flash synthesis of zirconia nanoparticles by microwave forced hydrolysis

Forced hydrolysis preparation of zirconia sots and powders by microwave hea ting of zirconium tetrachloride solutions at temperatures equal to 180 degr eesC leads in a few minutes to monodispersed nanoscale zirconia particles. Synthesis was performed in a microwave reactor called the RAMO system. This microwave reactor was designed by the authors. This flash-synthesis proces s combines the advantages of forced hydrolysis (homogeneous precipitation) and microwave heating (very fast heating rates). The sots and powders were characterized by x-ray diffraction,photon correlation spectroscopy (PCS), s mall-angle x-ray scattering, and transmission electron microscopy. Sots are colloidally stable, which means that after 6 months no sedimentation is ob served and the size distribution given by PCS measurements has not changed. For all synthesis conditions (with or without HCl, zirconium salt concentr ation, and synthesis time), zirconia polycrystalline particles were produce d. According to the different analyses, these zirconia polycrystalline part icles were constituted of aggregates of small primary clusters.