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Anodized aluminum (Al) and Al alloys have a wide range of applications. However, certain anodized finishings have relatively low hardness, dull appearance and/or poor corrosion resistance, which limited their applications. In this research, Al was first electropolished in a phosphoric acid-based solution, then anodized in a sulfuric acid-based solution under controlled processing parameters. The anodized specimen was then sealed by two-step sealing method. A systematic study including microstructure, surface morphology, hardness and corrosion resistance of these anodized films has been conducted. Results show that the hardness of this new anodized film was increased by a factor of 10 compared with the pure Al metal. Salt spray corrosion testing also demonstrated the greatly improved corrosion resistance. Unlike the traditional hard anodized Al which presents a dull-colored surface, this newly developed anodized Al alloy possesses a very bright and shiny surface with good hardness and corrosion resistance. [ABSTRACT FROM AUTHOR]

Black nickel coatings are widely used in industries due to their shiny black color and other unique properties. However these coatings are normally soft, which limits their applications. In order to increase the mechanical properties of black nickel coatings, sol-enhanced technology has been applied to the plating process. TiO2 sol-enhanced black nickel nanocomposite coatings were electroplated on nickel-coated brass. A systematic study on the microstructure and properties of the black coatings were conducted. The effects of TiO2 concentration (TiO2 sol concentration in 0-20 mL/L) on the surface morphology, nanohardness and wear resistance have been studied. The results indicated that the nanohardness of the sol-enhanced black nickel coating was increased by 20%. The mechanisms of improvement and surface morphology variation were also discussed. [ABSTRACT FROM AUTHOR]

Gold (Au) coatings are widely used for electrical contacts in devices, decoration and jewelry. However, the relatively low hardness and poor wear resistance of pure Au coatings lead to a short service life and limit their application. Ni is frequently used as an alloying element to enhance the hardness but it lowers the conductivity of Au coatings. In this research, Co was co-deposited as an alloying element with Au to improve its mechanical properties while maintaining conductivity. TiO2 sol in different concentrations was added to the Au-Co plating bath to further enhance the coating strength. Systematic studies including surface morphology, hardness, wear resistance and electrical conductivity have been carried out. Key results from nanoindentation tests demonstrated that the hardness of Au-Co-TiO2 composite coating was increased by 30% when compared to a pure Au-Co coating, while the electrical conductivity has been kept at the same level. [ABSTRACT FROM AUTHOR]

Sn coatings were widely used in electronic and device industries due to their unique properties. Sn-TiO2 sol-enhanced nanocomposite coatings were prepared in order to improve the mechanical properties of Sn coatings. The microstructure, mechanical properties and conductivity of sol-enhanced Sn-TiO2 nanocomposite coatings were systematically investigated. The results show that after adding an optimum quantity of TiO2 nanoparticles, the nanohardness of Sn-TiO2 coatings was increased by 75% while the conductivity remained unaltered when compared with a pure Sn coating. The effect of TiO2 sol addition on the properties of coatings was discussed. [ABSTRACT FROM AUTHOR]

Ni-Co-ZrO2 nanocomposite coatings have been electroplated on mild steel by adding ZrO2 nanoparticles into an Ni-Co plating solution. The microstructure and mechanical properties of nanocomposite coatings were systematically investigated. The results show that the microhardness of Ni-Co-ZrO2 nanocomposite coatings varied significantly with the quantity of ZrO2 nanoparticles. Ni-Co-10 g/L ZrO2 nanocomposite coating exhibited the optimum mechanical properties due to the dispersion strengthening effect. Addition of ZrO2 nanoparticles beyond 10 g/L led to particle agglomeration and caused a porous coating structure, resulting in a deterioration of coating mechanical properties. [ABSTRACT FROM AUTHOR]