Investigations of electron emission from DLC thin films deposited by means of RF PCVD at various self-bias voltages

The aim of this paper is to report the results of field emission experiments on undoped, flat diamond-like carbon (DLC) thin films deposited at various self-bias voltages using radio frequency plasma chemical vapor deposition (RF PCVD) technique. It has been observed that the emission properties improve when the absolute value of self-bias voltage becomes higher, e.g., the turn-on field value decreases. The correlation between electron field emission and sp2 content in these films showed improvement of electron emission properties of DLC films for higher amount of sp2 phase

-Microstructure and electronic emission of plasma sprayed TiO2 functional coating with gradient of crystal grain size

International audienceThe paper aims at the 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 mm. Thin, outer layer of thickness smaller than 10 mm, was plasma sprayed using different aq. suspensions of fine powders of TiO2. The morphol. 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 mixt. of rutile and anatase in suspension sprayed coatings. This was also confirmed by Raman spectroscopy investigations. The technol. 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 photoelec. spectroscopy (XPS) was used to analyze quant. TiO2 powders and coatings. Electronic emission was correlated with phase compn. of the coating and their grain size

Microstructural characterization of plasma sprayed TiO2 functional coating with gradient of crystal grain size.

The paper aims at development of a coating with a gradient in grain size. A first layer was deposited directly onto stainless steel substrate by plasma spraying of a coarse TiO2 powder. This layer had thickness in the range from 30 to 50 mm. A second layer was deposited on the first one using plasma spraying of different aq. suspensions of two TiO2 pigments. The layer had thickness smaller than 10 mm. Morphologies of TiO2 powder and pigments were characterized using a scanning electron microscope (SEM) and their sizes were tested with a laser sizer. Phase anal. of powder and pigments, made by X-ray diffraction (XRD), enabled only rutile phase to be discovered. A mixt. of rutile and anatase was found in the suspension sprayed coatings. The presence of anatase in sprayed coatings was an interesting and original result, which was also confirmed by Raman spectroscopy. The formation of this phase was tentatively explained by a high cooling rate of small splats. The suspension plasma spraying was optimized in order to obtain homogeneous and dense deposits. The morphol. of sprayed coatings was characterized using SEM. Crystal grain sizes were estd. using XRD. The sizes were in the range of a few tenths to one hundred nanometers in the initial powders. They were clearly smaller in the coatings sprayed using coarse powder but remained quite similar in suspension sprayed layers. Finally, XPS was used to analyze quant. the chem. compn. of powders and coating