NANOMETRIC Al₂0₃ - ZrO₂ POWDERS PRODUCTION BY ARC PLASMA TREATMENT

Spherical nanometric Al₂O₃ - ZrO₂ powders have been prepared from commercial micrometric and irregular in shape ceramic oxides. A mixture of Sumitomo AES11SDC spray dried alumina and Magnesium Elektron S-grade zirconia (90/10 % in weight) was introduced during a few hours, with a rate of ~ 100 g/hour, through a lance and a screw feeder (under a flow of oxygen), inside the coupling zone of two plasma jets produced by a twin torch plasma system in a cylindrical furnace (arc current 200 to 400 A, voltage ~ 100 V; plasma forming gas: 20 NL/min of Ar at the anode, 10 NL/min of Ar and 10 NL/min of He at the cathode). Powders collected inside the heat exchanger and on the bag filter have been analysed by TEM, laser granulometry and X-ray diffraction. The aggregates of small particles (from a few nm to ~100 nm) observed contain α and δ Al₂O₃ and monoclinic and tetragonal ZrO₂.