Papers by Keyword: Passivation

Abstract: The innovative use of surface shot-peering to make a passivation at milling cutting edge of wheel, it shows that passivation has eliminated all microcrack and abrasion trace on the surface of milling cutting edge through microscopical observation, so as to improve adhesive force among the coating and cutter body, to make an uniform wear of cutter with coating during machine work, and further to keep fairly good function of cutting edge. Furthermore, the milling length of wheel cutter is over 8 meters, and such technology has solved the technology problem in production domesticization of wheel cutter.

Abstract: The utilization of zinc anode for zinc-based battery is limited due to low cycling life, shape change and ZnO passivation on the electrode surface. The electrochemical behavior of zinc anode in the presence of the additives added to the electrodes or the electrolytes have been reported. In this work, LaCoO3 was used as an additive to improve the electrochemical properties of the zinc oxide anode. LaCoO3 synthesized by sol gel method (Schiff base complex) was added to zinc oxide powder (99.9%) with the weight ratio of 1:0.001, 1:0.002 and 1:0.003. The relative ZnO/LaCoO3 ratios were confirmed by particle induced x-ray emission (PIXE) technique.The electrochemical behavior of the ZnO/LaCoO3 electrodes in 6M KOH solution were investigated by voltammetry and electrochemical impedance spectroscopy (EIS). The cyclic voltammogram showed that ZnO/LaCoO3 gave higher anodic current and ZnO passivation delayed. The EIS spectra showed that charge transfer resistances of the ZnO/LaCoO3 anodes due to zinc oxidation were higher than that of ZnO electrode

Abstract: In order to reduce the environmental pollution from chromate used in plating factories, one new kind of non-chromium passivation solution containing silicate, hydrogen peroxide and fluoride ion, etc. has been explored to form blue-white conversion film on alkaline electrodeposited zinc coatings. The conversion films on zinc coatings with both glossy blue-white surface and high anti-corrosion performance have been obtained by optimizing the experimental conditions. The results show that silicate-based passivation technique is able to be widely applied to solve the problem of pollution caused by waste from plating industry in the future.

Abstract: Ni-Cu-P coating was synthesized on copper substrate by electroless plating technique. The coating composition and corrosion resistance of Ni-Cu-P coating were characterized using energy-dispersive X-ray (EDX), electron probe micro-analyzer (EPMA), polarization curve (PC) and electrochemical impedance spectrum (EIS). The results show that the chemical nature of anions plays very important roles in the corrosion behavior of Ni-Cu-P coating. At a higher electrolyte concentration, Cl- and SO4 2- ions tend to promote the dissolution rate of Ni by their adsorption, while at lower electrolyte concentrations, NO3 - ions tend to dominate the dissolution rate of Ni-Cu-P coating.

Abstract: The corrosion behavior of the Fe60Co8Zr10Mo5W2B15 bulk amorphous alloy in 2 mol·L-1 HCl solution was investigated using full immersion test. The results indicated that the Fe60Co8Zr10Mo5W2B15 bulk amorphous alloy was at the passivation condition in the 2 mol·L-1 HCl solution, which had the strong anticorrosive ability. X-Ray Photoelectron Spectroscopy (XPS) spectrum of the composition and structural feature of the test sample surface film after passivation indicated finally, that the passivation of the bulk amorphous alloy is primary due to the oxide compounds such as ZrO2 and so on formed on the bulk amorphous alloy surface in the HCl solution.

Abstract: We developed multilayered, purely inorganic coatings for the corrosion protection of AZ magnesium alloys. Polymeric acid-catalyzed sols form relatively dense coatings, but any direct contact to the reactive magnesium substrate has to be avoided. However polymeric sols based on SiO2, B2O3, Al2O3, ZrO2 and up to 5% of lanthanide salts can be used to seal samples with prime coat based on aqueous nanoparticle dispersions. Without organic network modification, these sealings have to be kept thin to avoid cracks. However if the coating process with aqueous dispersions and polymeric sols is alternated, a kind of lamellar sandwich structure can be formed which stays crack-free up to several layers. The performance and the protective properties of these coatings were studied with different methods (EIS, salt spray tests and electron microscopy).

Abstract: The electrochemical corrosion resistance of the passivated Fe-40at.%Al binary alloy has been investigated in sulfuric acid at 25°C. Structural investigations were conducted by XRD method and confirmed a single phase material of the ordered B2 structure. Electrochemical corrosion behavior was determined using potentiodynamic polarization and EIS methods. Anodic polarization measurements revealed a passive behavior of the tested electrode. Detailed characteristics of the Fe-40at.%Al electrode | passive film | solution interface as a function of the electrode potential in the fully passive range of 0.5  E  1.5 V, was investigated. The impedance behavior was determined by a highly doped n-i-n structure (n-type semiconductor – insulator – n-type semiconductor).

Abstract: The electrical characteristics of Au/3C-SiC Schottky diodes were studied and related to crystal defects. A structural analysis performed by transmission electron microscopy (TEM), combined with a current mapping of the surface by conductive atomic force microscopy (C-AFM), indicated that stacking faults (SFs) are the conductive defects having the biggest influence on the electrical properties of the Schottky barrier on 3C-SiC. Further, C-AFM current mapping of the semiconductor surface also showed that an ultraviolet (UV) irradiation process enables the electrical passivation of the SFs, due to their preferential oxidation. From current-voltage (I-V) measurements in diodes of different area (different amount of defects) it was observed that, for the non-irradiated surface, no significant dependence of the Schottky barrier height (ΦB) on the contact area could be observed. On contrast, after the UV-irradiation, ΦB gradually increases with decreasing contact area, ultimately leading to a nearly ideal value of the barrier height for the smallest diodes. The results indicate that even after the passivation of SFs there are still some electrically active defects contributing to deleterious conduction, responsible for a worsening of the electrical properties of the diodes.

Abstract: In this work, the electrical performance in terms of maximum current gain, ON-resistance and blocking capability has been compared for 4H-SiC BJTs passivated with different surface passivation layers. Variation in BJT performance has been correlated to densities of interface traps and fixed oxide charge, as evaluated through MOS capacitors. Six different methods were used to fabricate SiO2 surface passivation on BJT samples from the same wafer. The highest current gain was obtained for PECVD deposited SiO2 which was annealed in N2O ambient at 1100 °C during 3 hours. Variations in breakdown voltage for different surface passivations were also found, and this is attributed to differences in fixed oxide charge that can affect the optimum dose of the high voltage JTE termination.

Abstract: Zn-Ni and Zn-Ni-W coatings were prepared by the electrodeposition under the galvanostatic conditions (jdep. = -0.020 A cm-2) from the zinc bath containing additionally ions of nickel (Zn-Ni) and ions of nickel and tungsten (Zn-Ni-W). The Zn-Ni coating after electrodeposition was subjected to outside passivation and in the Zn-Ni-W coating the passive function performs tungsten (inside passivation). The surface morphology of the coatings was studied using a scanning electron microscope (JEOL JSM - 6480). Chemical composition of obtained coatings was determined by the X-ray fluorescence spectroscopy (XRF). Phase composition investigations were conducted by X-ray diffraction method using a Philips diffractometer. Electrochemical corrosion resistance investigations were carried out in the 3% NaCl, using potentiodynamic and electrochemical impedance spectroscopy (EIS) methods. On the basis of these investigations it was found that Zn-Ni coating is more corrosion resistant than the Zn-Ni-W coating.