Hafnia and Hafnia-Zirconia Mixed Oxide Ultra Spherical Microspheres Made by a SOL-GEL-Vibrational Dropping Process

摘要

Trends in ceramics development have recently been moving toward increasingly high quality ceramic materials such as partly stabilized Zirconia. Metal oxides such as CaO, MgO, Y_2O_3, CeO_4, etc. are used as stabilizing additives. The object of the recent development was to find a method for producing stabilized Hafnia, Hafnia containing or Zirconia high density spheres or spheres with tailored pore size and surface area with a uniform spherical geometry and a narrow grain size distribution. Aqueous solutions or sols of Hf or Zr preneutralized with ammonia are the precursors to get microspheres. The liquid is gently pumped through a vibrating nozzle system where upon exiting the fluid stream breaks up into uniform droplets. The surface tension of these droplets molds them into perfect spheres in which gelation is induced during a short period of free fall. Solidification can be induced in an ammonia gaseous and liquid medium through chemical reaction.