Field Electron Emission from Surface of Plasma Sprayed and Laser Engraved AI₂O₃+13TiO₂ and Al₂O₃+40TiO₂ Coatings

The powders of alloys Al₂O₃+13wt.%TiO₂ and Al₂O₃+40wt.% TiO₂ were plasma sprayed onto aluminum rolls coated initially with Ni20Cr bond deposits. The coatings were subsequently ground, polished and submitted to laser engraving. The engraving, similar to that applied for anilox rolls manufacturing, enabled production of three different patterns with the line densities of 60, 100 and 200 1/cm and depths of about 80, 50 and 10 µm correspondingly. The patterns were engraved under angle of 60° that corresponds to a honeycomb geometry of cells. Emission current, for the electric fields up to 150 V/µm, was in the range of 10-7-10-4A for coatings containing 13 wt.% of titania and, in the range 10-11–10-9 A for that of 40 wt.% of titania. The SEM observations of engraved coating morphology was made in order to find the electron emission spots.