Key Engineering Materials Vol. 659

Abstract: Nickel-tungsten alloy were fabricated by electrodeposition on carbon steel. The influences of saccharin sodium on the coatings were analyzed using XRD, SEM, and hardness tester. This study reveals that the presence of saccharine sodium has a profound impact on the morphology of the coatings. Moreover, the addition of saccharine sodium tends to enhance the tungsten content in the coatings along with hardness and the grain size of the deposits.

Abstract: In this work, titaniumoxynitride (TiO_xN_y) thin films were deposited on glass slide substrates by using reactive dc magnetron sputtering technique. The reactive gas ratios between O₂ and N₂ were studied in the range of 15-30% with a constant of Ar gas at 110 sccm and a time of 120 minutes. Microstructure, optical, and electrical properties of TiO_xN_y thin films were analysis by using SEM, AFM, GIXRD, UV-VIS spectrophotometer, and 4-point probe measurements. We found that the thickness of the films decreases from 1.0 to 0.8 μm by increasing of O₂ gas ratios. The TiO_xN_y thin films have smooth surface related to small nanograin size. The roughness of the films slightly decreases when O₂ gas ratios increase. From optical transmission spectra, we observed that the transparent of the films increases with different O₂ gas ratio and shifts the band gap from 2.67 to 3.32 eV. The resistivity of the films obviously increases from 3.04 x 10^-3Ω-cm to 5.45 Ω-cm depending on O₂ gas ratio. These results indicate the phase changes of the TiO_xN_y films from metallic to oxide phases. The XRD spectra show poor crystalline TiN (220) and TiO₂ (021) at 15% of O₂ ratio and then the films become amorphous structure by increasing the O₂ gases. The O₂:N₂ gas ratios also affects to the different concentration of oxygen and nitrogen into the TiO_xN_y thin films that lead to the various structural, optical and electrical properties.

Abstract: The Iron-Tungsten boride based composite was coated on the inner surface of steel pipes by centrifugal-self-propagating high-temperature synthesis (centrifugal-SHS) process. The precursors were prepared by a stoichiometric ratio of wolframite mineral (Fe (Mn)WO₄), aluminum (Al) and boron oxide (B₂O₃). Phase composition and microstructure of composite coating were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). On this study, depending on the rotation speed, the highest rotation speed (2250 rpm) produced highest micro-hardness of the composite (1699 HV).

Abstract: Multi-functional thin films have gained increasing importance in a decorative application. Among the available material, titanium nitride (TiN) thin film is interesting due to its golden color and mechanical resistance. Beside their properties, the corrosion property of TiN films is mainly considered in order to extend the life time. In this work, the TiN thin films were deposited on 3x3 cm² Si(100) substrates by dc reactive magnetron sputtering technique. The effects of N₂ partial pressure (P_N2) on deposited film properties such as microstructure, surface morphology, color, mechanical and corrosion properties were investigated. We found that the crystal structure of the TiN films exhibit the (200) preferred orientation. The color of TiN films change from gold-yellow to gold-red colors by increasing of N₂ partial pressure that could be explained by Drude model. The TiN films have smoother surface when the N₂ partial pressure increases. Standard corrosion tests in artificial sweat solution show the corrosion current density (i_corr) in the range between 0.25 to 4.25 mA/cm² and the polarization resistance increases with increasing of N₂ partial pressure. The highest hardness of the film is approximately 40 GPa with elastic modulus of 340 GPa. We conclude that N₂ partial pressure corelates with color, mechanical property and corrosion resistance of TiN films, which were optimized to use in decorative application.

Abstract: In this study, we investigate a facet of the fabrication process of chromium nitride (CrN) film intended as a protective coating for pineapple blades. CrN thin films were deposited on unpolished stainless steel substrates (AISI304) by DC reactive magnetron sputtering in Ar+N₂ gases. In principle, the proportion of nitrogen partial pressure to the total pressure in the sputtering process should have considerable effects on the CrN film’s chemical composition, its crystal structure, its hardness, and its corrosion resistance. We tested this supposition out by using several different nitrogen partial pressures in the sputtering process and observed the films deposited. The coatings were deposited at five different nitrogen partial pressures of 4.0x10^-4 mbar, 8.0x10^-4 mbar, 1.2x10^-3 mbar, 1.6x10^-3 mbar, and 2.0x10^-3. The deposition times were controlled to achieve 5-µm thick films in each deposition. The films were analyzed by several analytical methods, such as X-ray diffraction (XRD), scanning electron microscope, micro-hardness and potentiostat in pineapple juice. The XRD spectra of the films showed face-centered cubic structure with (200) preferred orientation, positively identifying them as Cr₂N and CrN thin films. The calculated d-spacing and lattice parameter of the CrN films increased with increasing nitrogen partial pressure; the ranges were 0.283–0.287 nm and 0.491-0.497 nm, respectively. The cross-section morphology of the CrN films reveals the columnar grain growth with a high density. The crystal structure and the grain texture correspond with the hardness property. The films corrosion potential, an indicator of their corrosion property, was varied from -0.14 to -0.05 volts with varying nitrogen pressure. The most corrosion resistant and the good hardness were the film fabricated at the nitrogen partial pressure of 1.2x10^-3 mbar.

Abstract: Mechanical fasteners such as screws, nuts, bolts, and washers are integral components in a vehicle. Rust or corrosion mechanisms of fasteners in the automotive industry is complex and may probably due to many factors includes temperature, pH, ion concentrations, coatings compositions as well as fastener geometry. Most of underhood fasteners used by PROTON models are Zinc coated fasteners. PROTON requires interior fasteners are coated to a minimum of 5 μm, while exterior fasteners are of 8 μm minimum thickness. There is a need to understand the corrosion performance of such fasteners in order to improve cosmetic and functional performances of these fasteners. The main objective of this study is to evaluate corrosion performance of three different compositions of Zinc-coated underhood fasteners using laboratory test. Samples were subjected to salt spray test with 5% NaCl for specific periods of time, in accordance ASTM B117-90 and JIS Z 2371:2000 conforming to their corrosion resistance requirements based on coating type and thickness. Results of the study revealed that Zn-Ni and Zinc-flake platings exhibit superior corrosion resistance characteristics with rating number (RN) of 10 compared to conventional 8 μm hexavalent-chrome free plated fasteners.

Abstract: This research fabricated hydrophobic surfaces of aluminium alloy via electrochemical anodization and silane coating. The procedures consisted of electrochemical anodization in 1 and 1.5 M sulfuric acid using 12 volts dc. Anodization produced stable porous oxide layer on the surface. Aluminium alloy formed porous oxide structures with thickness in micrometer regime. The thickness of the porous layer was affected by the anodizing conditions such as electrolyte concentration and time. Dichloro methylsilane (5% in ethanol) was applied onto the porous surfaces by submerging the anodized surfaces into it for 10-60 min. After washing the treated surfaces with soap for many times, hydrophobic surfaces were obtained with some surfaces showed wetting angles greater than 100°. Water droplets of any sizes can roll off on these surfaces when tilted at angles above 10°. The treated aluminium surfaces can be applied for self-cleaning and anti-icing applications.

Abstract: UV-curable process is widely used for paints, inks and adhesives due to its rapid curing, low energy consumption, high efficiency and low volatile organic compounds (VOCs). The objective of this research is to prepare poly(lactic acid) (PLA) based UV-curable coating by using glycolyzed PLA. PLA was glycolyzed by ethylene glycol (EG) at 170°C for 90 minutes. The obtained glycolyzed PLA was reacted with methacrylic anhydride (MAAH) to provide PLA acrylate oligomer. The obtained PLA acrylate oligomer was used in coating formulations with various amounts of photoinitiator and cured under UV radiation. Physical properties of cured coating film were investigated such as pencil hardness, gloss and haze. The results showed that poly(lactic acid) (PLA) based UV-curable coating provided good physical properties.

Abstract: This paper reports the analysis of the composition, structure and phase of the re-deposition material that was generated from the reaction from CF₄ plasma etching on the Al₂O₃-TiC substrate. The re-deposition was sputtered from the etching area and deposited on a silicon coupon for analysis. The morphology of the re-deposition was investigated by scanning electron microscope (SEM) and the composite element of the re-deposition was detected by using energy dispersive x-ray spectroscopy (SEM-EDX). X-ray diffraction (XRD) was used to analyse the structure and phase of the re-deposition. The results show that the prepared re-deposition was composed of F and Al atoms, with 51.24 At% and 27.67 At%, respectively. XRD revealed that this was owing to the chemical formula AlF₃, which has a rhombohedral crystal structure in the most stable alpha phase (α-AlF₃).

Abstract: Nanoscale material world attracted researchers because of their outstanding properties and prospective novel applications. Tungsten trioxide semiconductor is one of the fundamental functional materials due to its versatile application as gas sensors, solar cells, and smart windows. Confined growth of the metal oxide nanostructures can tune the electrical and optical properties for modern device application. The management of morphology is a challenge to investigate the ultimate performance. In this paper, self-assembled growth of four different tungsten trioxide nanostructures were carried using a different structure directing agents through either co-precipitation or hydrothermal techniques. The monoclinic spherical and rod-like WO₃ nanostructures were obtained by acid precipitation method. WO₃ nanocuboids and nanofibers were synthesized hydrothermally using HBF₄ and NaCl as structure directing reagents to attain monoclinic and hexagonal crystal phases, respectively. Analytical techniques like XRD, TEM, and FESEM imaging methods were used to confirm the phase and morphology. All the nanopowders were calculated to have similar band gap energy at visible wavelength. A simple dip coated WO₃/ITO fabricated electrode was used as a reference electrode to carry out the electrochemical measurements for all nanopowders. The evaluated properties suggested the plausible use of WO₃ nanofibers for high efficient electrochromic device.