Microstructure and Electronic Emission of Plasma Sprayed TiO2 Functional Coating with Gradient of Crystal Grain Size
Prof. Lech Pawlowski1, R. Tomaszek1, Dr. L. Gengembre2, Dr. J. Laureyns3, Dr. Z. Znamirowski4 and J. Zdanowski4, 1Thermal Spraying, ENSCL, 8, av. Mendeleiev, Villeneuve d'Ascq, 59650, France, 2Laboratory of Catalyse, University of Lille 1, Villeneuve d'Ascq, France, 3Laboratory Lasir, University of Lille 1, Villeneuve d'Ascq, 59650, France, 4Faculty of Microsystems and Photonics, Wroclaw University of Technology, Wroclaw, 50-370, Poland

The paper aims at development of coating having a gradient of crystal grain size. Thick, inner layer was plasma sprayed using coarse TiO2 powder. This layer has the thickness ranging from 30 to 50 µm. Thin, outer layer of thickness smaller than 10 µm, was plasma sprayed using different aqueous suspensions of fine powders of TiO2. The morphology of coarse and fine powders was characterized using scanning electron microscope (SEM) X-ray diffraction (XRD). Electronic emission was tested using home made setup. X-ray diffraction enabled to find out an interesting result which is formation of a mixture of rutile and anatase in suspension sprayed coatings. This original result was also confirmed by Raman spectroscopy investigations and the formation of anatase was tentatively explained by higher cooling rate of small splats. The technology of suspensions plasma spraying was optimized to obtain homogeneous and dense deposits. The sizes were in the range of tenth to one hundred nanometers in initial powders and get clearly smaller in the coatings sprayed using coarse powder but remained quite similar in suspension sprayed films. X-ray photoelectric spectroscopy (XPS) was used to analyze quantitatively TiO2 powders and coatings. Electronic emission was correlated with size of crystal grains.

Session 4: Nanomaterials 1

The Preliminary Program for International Thermal Spray Conference And Exposition (ITSC) (May 15-18, 2006)