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Abstract: The aim of this work was to provide a comprehensive insight concerning coated films which might be used for first mirrors in ITER. The influence of the mirror crystallite size has been addressed as well as the coating techniques to provide nanocrystalline films. Tests of coated mirrors both in laboratories and in tokamaks are reviewed. For the tokamak tests a wide angle camera system has been installed in JET-ILW which is composed of a mirror box with 3 stainless steel mirrors coated with rhodium viewing the torus through a conically shaped aperture. The system delivered the required image quality for plasma monitoring and wall protection. No or insignificant degradation of the optical transmittance has been observed during the experimental campaign in 2014 with about 3000 plasma pulses in different magnetic field configurations. Keywords: First Mirrors, ITER, Mo, Rh coating, JET wide angle viewing system. |
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Abstract: The possibility of preparation of nanocomposite coatings consisting of a solid lubricant matrix (MoSex) and nanocrystalline metal particles (nc-Mo) was demonstrated using pulsed laser deposition from synthesized target MoSe2.The particles had spherical shapes and their sizes were about 5 – 50 nm. The content of the nc-Mo nanoparticles in the MoSex/nc-Mo coatings was varied by changing the laser irradiation regimes and the conditions of expansion of the laser plume from the target to substrate. It was established that the tribological properties of the nanocomposite coatings MoSex/nc-Mo are depended on the concentration of nanoparticles in the bulk of the coatings as well as on the structure of the coating matrix. The MoSex/nc-Mo coating with increased crystalline order of matrix obtained on a steel substrate reduced the friction coefficient to ~0.04 during steel ball sliding in air of laboratory humidity. Probable mechanisms of nanoparticle formation were proposed and a role of these particles in the wear of the nanocomposite MoSex/nc-Mo coatings was discussed.
Keywords: Low friction coatings, Nanostructure, Nanoparticles, Coefficient of friction, Molybdenum diselenide. |
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Abstract: The aim of the optimization of the technological process was to coat the surface of the pigment in a controlled manner and to supress photoactivity in the titanium dioxide (TiO2) pigment. As part of this research, a systematic approach to TiO2 pigment surface treatment with alumina was conducted. Surface treatment with alumina plays a significant role in the improvement of TiO2 properties (e.g. weather resistance and photostability).This research encompasses a raw material analysis and process conditions study. Sodium aluminate and aluminium sulphate were used as a source of alumina hydroxide. The effectiveness of surface treatment was determined using scanning-transmission (STEM) and transmission (TEM) electron microscopy. The photoactivity of pigmentary TiO2 was determined before and after surface treatment. A controlled surface treatment process resulted in pigmentary TiO2 particles with uniform amorphous layers, which supressed the photoactivity of the pigment. Keywords: Titanium dioxide, Surface treatment, Coatings, Alumina, Photo activity. |
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Abstract: This study used cathodic arc deposition technique to coat TiN film on 316L austenitic stainless steel, and then the coated specimens were heat-treated at the different temperatures. Observation of coating morphology and corrosion tests were conducted for exploring the effect of post-heating temperature on composition, microstructure, and corrosion behavior of the coatings. The results showed when the heating temperature was up to the range of 500-600 oC, a Ti-N-O mixed film consisting of the two TiO2 and TiN phases was formed on the outer layer. Particular, the film heated at 500 oC had a dense structure as well as homogeneous chemical composition. Such the result could effectively inhibit pitting corrosion of 316L stainless steel in 3.5 wt% NaCl and 10 vol% HCl solutions.
Keywords: Cathodic arc deposition, TiN film, 316L stainless steel, Post-heating, Pitting corrosion. |
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Abstract: The paper presents the results of survey, dedicated to synthesis of metal oxide coatings on porous materials applied for implant surgery (stainless steel 12X18H9T, titanium alloy and high-purity niobium VT5). This article examines kinetic features of electrochemical formation of anodic oxide coatings on steel, niobium and titanium. It is shown that for steel anodic treatment method does not provide a reliable surface passivation (no current decay, the surface indicates the transition to the passive state). Analysis of polarization dependences obtained on niobium and titanium in electrolytes with an activator (F-), indicates surface passivation (current slump), and at potentials above 2 on the surface of a transition curves in transpassive state (as evidenced by the current increase). Consequently, it can be concluded that presence of F- results surface activation of titanium and niobium electrode (F- oxide reacts to form water-soluble complexes) that promotes nucleation and formation of pores of the porous structure of the oxide coating. SEM results verify the presence of self-organized porous oxide film synthesized on titanium and niobium in solutions containing F-. Keywords: Oxidation, anodic film, coating, implantant. |