Low macroscopic field electron emission from surface of plasma sprayed and laser engraved TiO 2, Al 2O 3+13TiO 2 and Al 2O 3+40TiO 2 coatings

Abstract

The paper deals with investigation of electron field emission from plasma sprayed and laser engraved TiO 2 and Al 2O 3–TiO 2 coatings of two compositions (13 and 40 wt.% of TiO 2). The coatings were plasma sprayed onto aluminum rolls coated initially with Ni20Cr alloy. Their technology included also grinding and polishing prior to CO 2 laser treatment. The treatment was similar to that applied for anilox rolls manufacturing and allowed a production of three different patterns with the lines densities of 60, 100 and 200 cm −1 and depths of approximately 80, 50 and 10 μm correspondingly. The patterns were engraved under angle of 60° that results in a honeycomb geometry of cells. Measurements of emission current under macroscopic electric field up to 150 V/μm for all the samples were carried out. The SEM observations of engraved coating morphology were made in order to find the electron emission spots and XRD analysis allowed to identify the crystal phases present in the coatings. A tentative explanation of a field emission mechanism basing onto Fowler–Nordheim (FN) model is also presented.