Papers by Keyword: Sol-Gel Coating

Abstract: Industrial waste is primarily handled using landfills in both developed and developing countries. While there has been a significant rise in solid waste reduction, reuse, and recycling, landfill disposal will inevitably remain the most commonly used form of waste management. Although landfilling provides an economic means of waste disposal, it can lead to environmental degradation by releasing various contaminants if not managed properly. In this work, industrial waste from electrostatic precipitators (ESP) will be beneficial for the production of coatings on metal substrates. The sol-gel coating method have been attempted for deposition on pure Mg samples. Using the potentiodynamic polarization (PDP) method and hydrogen evolution analysis, the effectiveness of the coating, which is the corrosion resistance was analyzed. A minimal application of Tetraethyl orthosilicate (TEOS) in the ESP dust solution has been shown to substantially reduce the corrosion rate of Mg. This is likely due to the impact of its concentrations through the sol-gel process that could increase the size of the particle shape or growth.

Abstract: The paper considers the dependence of the continuity of the sol-gel coating of carbon fiber on the preliminary anodic oxidation of the surface in a sodium hydroxide solution. The effect of the treatment time, the voltage between the cathode and the anode, NaOH concentration in the electrolyte, and the temperature of the electrolyte was investigated. It is shown that with an increase in NaOH concentration in the electrolyte, the area of uncoated fiber surface sections increases, the continuity of the coating decreases, while the coating obtained without preliminary surface treatment has sufficient continuity of at least 93%. Changes in other parameters (temperature, time, voltage) of preliminary electrochemical surface treatment in the ranges under study did not allow us to fix regularities other than the given one.

Abstract: 2xxx Al alloys are particularly sensitive to localized corrosion in chloride environments and in order to maintain their integrity, minimize maintenance needs and repairs, and to maximize component life, protective treatments are required.Anodizing is an electrochemical process based on the growth of the Al oxide layer by applying anodic potentials. One of the alternatives is tartaric/sulphuric acid (TSA) anodizing, which is environmentally compliant and provides corrosion resistance properties, compatible with the requirements of the aerospace industry with appropriate paint adhesion.In this study, AA2524-T3 specimens were anodized in a tartaric-sulfuric acid bath (TSA) and subsequently protected by application of a hybrid sol–gel coating. The sol–gel coating was prepared using a solution with high water content (58 %v/v) and obtained by the hydrolysis and condensation of tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The corrosion resistance evaluation of both unsealed and coated samples was carried out in a sodium chloride solution by EIS as a function of immersion time. The results were also fitted using electrical equivalent circuits.

Abstract: Corrosion inhibitor-inorganic clay composite including 2-mercaptobenzimidazole (MBI) anions intercalating Zn-Al layered double hydroxides (LDHs) assembled via anion-exchange reaction. Powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectrum analysing and scanning electron microscopy (SEM) indicate that the MBI anion are successfully intercalated into the LDHs interlayer. The benzene plane is horizontal arrangement rather than vertical orientation in the interlayer spacing. The active anticorrosive property of AA2024 alloy with the active anticorrosion coating is evaluated by electrochemical impedance spectroscopy (EIS). The sol-gel coating doped with the LDHs clearly demonstrates long-term anticorrosive performances compared to the undoped sol-gel coating, due to the release of corrosion inhibitor from the LDHs.

Abstract: Strengthening of glass sheets through the process of ion exchange have been widely used in thinner cover glass for smart phone. The compressive stress improves the ability of the glass surface to withstand damage from mechanical impact. However, the presence of the damage resistant layer makes conventional mechanical and laser cutting of the ion-exchanged glass difficult. Normally, the cutting process will lead to spontaneous glass sheet breakage or shattering. Even successful in some samples, the underlying central tension is exposed on the edge, and the mechanical strength and durability of this edge is degraded. The repair of edge cracks becomes an extremely important issue for the development of single glass based smart phone. The ion exchanged glass plates (Corning IOX-FS) with a thickness of 0.7 mm were selected as the substrate materials. After cutting ion exchanged glass by high penetration diamond scribing wheels, the edge of glass plates can be protected or strengthened with silica sol using roll coating process. It was observed that the strength could be improved achieving 210 % compared to the strength of uncoated glass sheets. The sol-gel coating could improve the strength of the glass mainly by the mechanisms of filling in edge flaws or blunting crack tips. The effects of silica sol and processing parameters of roll coating process on the cracks filling effects were investigated.

Abstract: Optical, surface and structural properties of ZnO thin films fabricated by reactive radio- frequency (rf) magnetron sputtering and sol-gel coating methods are comparatively investigated. The optical properties of films produced by both techniques have very similar characteristics, however; the surface morphology and degree of crystallinity have different behaviors. The nanostructure columnar zinc oxide thin films can be synthesized by sol-gel coating methods which can have numerous applications requiring larger surface area. Also, the process scalability and large-scale manufacturing of these materials are discussed. It indicated that the nanostructure ZnO thin films can be synthesized with sol-gel methods at wafer levels with nano-grains and improved surface properties compared with reactive rf magnetron sputtering deposition.

Abstract: Glass matrix composites based on NextelTM fibre reinforced borosilicate glass were fabricated. Unidirectional fibres were arranged in two directions with a periodic interspacing sandwiched between two glass slides. XRD analysis and SEM observations proved that the selected process parameters were effective in densifying the composites without significant transparency losses. A geometry based equation was derived to evaluate the expected light transmittance of the composites. ZrO2 coating on Nextel™ fibres, developed by a sol-gel method, was investigated in order to provide a weak bonding at the fibre/matrix interface to promote fibre pull-out during fracture. A developed hybrid sol-gel coating method was employed to form a smooth and crack free coating surface on the Nextel™ fibre bundles. The present composites show potential for applications in architecture and special machinery requiring strong transparent windows.

Abstract: The demand for high precision optical elements as micro lens arrays for displays increases continually. Economic mass production of such optical elements is done by replication with high precision optical molds. A new approach for manufacturing such molds was realized by diamond machinable and wear resistant sol-gel coatings. Crack free silica based hybrid coatings from base catalyzed sols from tetraethylorthosilicate (TEOS: Si(OC2H5)4) and methyltriethoxysilane (MTES: Si(CH3)(OC2H5)3) precursors were deposited onto pre-machined steel molds by spin coating process followed by a heat treatment at temperatures up to 800°C. Crack-free multilayer coatings with a total thickness of up to 18 µm were achieved. Micro-machining of these coatings was accomplished by high precision fly cutting with diamond tools. Molds with micro-structured coatings were successfully tested for injection molding of PMMA optical components. The wear resistance of the coatings was successfully tested by injection molding of 1000 PMMA lenses. Hardness and elastic modulus of the coatings were measured by nano indentation. The chemical composition was measured by X-ray photo electron spectroscopy (XPS) as a function of the sol-gel processing parameters.

Abstract: There are growing varieties of glasses available on the market for the manufacture of molded optical lenses. A glass with a low transition temperature (Tg) has the advantage of extending the service life of molding dies. However, most of the low Tg glasses have a high content of alkali metal oxides and tend to induce severe glass sticking problems. This has made the molding process of these kinds of glasses very difficult indeed. The low Tg glasses normally demonstrate poor chemical durability and scratch resistance. As a result, the yields of fabricating the glass-preforms are frequently rather low. This research tried depositing a very thin layer of aluminum oxide on various glass-preforms by a water based sol-gel process. A high temperature glass wetting experiment was carried out to investigate the high temperature interfacial reaction between the coated glass gobs and stainless steel substrate. It was found that when the uncoated glass-preforms were brought into contact with stainless steel, the contact angle decreased with increasing heating temperature and duration. Owing to the severe interfacial chemical reaction, the originally transparent glass gradually turned translucent. In the case of Al2O3 coated glass-preforms, the variation of the contact angles was very limited, which presented no sticking and no wetting behavior. No reaction products could be detected on the contact area after the wetting test. The optical transmission of those lenses molded from the coated glass-preforms exhibited no or very little changes after the molding process.

Abstract: In order to solve the environment problem caused by the inhibitors that are widely used to improve the corrosion and scaling of the carbon steel pipes and equipment in the transportation of the industrial water, the design of using coatings or films on carbon steel is put forward without adding inhibitor. Based on this design, the Ni3P-TiO2 coatings have been prepared on carbon steel by chemical plating and sol–gel method. The coatings mainly compose of Ni3P and TiO2 analyzed by the XRD patterns. The microstructure and morphology of the Ni3P-TiO2 coatings are full, smooth and no cracks using a scanning electron microscopy. The properties of the Ni3P-TiO2 coatings are determined through the electrochemical experiment, scaling inhibition and antibiosis experiment. The results demonstrate that the coatings have the excellent properties of anticorrosion, scaling inhibition and antibiosis. The mechanism of the efficiency maybe due to the change of the interfacial energy, but it need prove through the farther examination.