No abstract

Gold coatings are widely used in many fields for their shining color, excellent corrosion resistance, and electrical conductivity. However, they are not mechanically strong with low wear resistance. In this paper, we have prepared nano-composite Au-Ni-TiO 2 coatings by our newly developed sol-enhanced electroplating method. In order to obtain the optimal mechanical properties, a systematic study of Au-Ni-x TiO 2 coatings with different sol concentrations (x is the sol doping concentration from 0 to 25 mmol/L) has been conducted. It was found that nano-particles (3-12 nm) of TiO 2 were highly dispersed in the coating matrix. The mechanical properties of sol-enhanced nano-composite coating were significantly increased. The nano-hardness of the coatings was improved from 2.55 ± 0.13 GPa to 3.20 ± 0.15 GPa. Consequently, the scratch resistance and wear resistance of the sol-enhanced coating were also improved significantly. Meanwhile, the electrical resistivity of the sol-enhanced coatings keeps a same level as the pure Au-Ni coatings. Gold (Au) and gold alloy have been widely used in various applications for their unique properties such as beautiful/shining color, high chemical stability, good ductility, excellent conductivity, and good weldability.1-5 Au, Au alloy and Au based composite coatings have been synthesized by various technologies, such as E-Beam Evaporation, Magnetron Sputtering, Sol-gel deposition, Chemical Vapour Deposition (CVD), Electrochemical Over-potential Deposition (OPD), and Electroplating.6-9 Among these fabrication methods, electroplating method is a simple way to fabricate gold coatings because of its energy effectiveness, time efficiency, without using vacuum technology and the controllability of coating thickness and grain size. 10In order to improve the hardness of pure Au, alloy elements such as Co and Ni were co-deposited with Au, which is known as hard Au. Hard Au can be used on decoration surface and electrical components where shining color, chemical inertness and good wear resistance are combined. As expected, however, the electrical conductivity decreased with increasing mechanical strength. 11,12For the requirements mentioned above, the mechanical properties such as wear resistance and hardness of coatings are the most important factors which dominate the durability and service life of coated parts. In the past decades, many attempts were devoted to improve the mechanical properties of Au coatings. One of the popular methods is using hard particles to form composite coatings. [13][14][15] It is widely accepted that the highly dispersive nano-particles in composites can realize good strengthening effect. In order to achieve good dispersion of nano-particles, the electrolyte has be to maintained by special techniques, such as vigorous agitation, air injection, and/or adding surfactants. However, it is difficult to achieve good suspension because of the small particle size and large surface energy, which caused agglomeration of the nano-particles. The surface appearance of Au based ...

No abstract

( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 amorphous ribbons, a type of Co doped Finemet alloy, were prepared by melt-spinning and annealed at 440–560°C for 30 min. Influences of heat treatment and Co content on the crystallization were analyzed through differential scanning calorimetric (DSC) and X-ray diffractometry (XRD). The microstructure was analyzed by atomic force microscopy (AFM). The magnetic properties of ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 and Finemet ribbons were tested by an alternating current soft magnetic properties measurement system. A comparative study of frequency dispersion properties between ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 and Finemet was conducted. Results indicate that the optimal magnetic property has been achieved when ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 ribbons were annealed at the temperature range of 480°C–520°C, after which the grain size became between 10 nm and 20 nm. Although the permeability of ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 is not as high as that of Finemet, this Co -doped Finemet amorphous alloy presents better high frequency properties, and therefore is a promising candidate for the high frequency field applications.

A sol-enhanced gold ( Au ) — nickel ( Ni ) — titanium dioxide ( TiO 2) composite coating technique has been developed at the University of Auckland. The aim of the present study is to achieve quality control and thickness homogeneity of the coatings in order to scale up this process to the workshop level. Multi-coating samples were prepared in the same electroplating unit with same processing parameters. The thickness variation and influence of titanium dioxide ( TiO 2) sol content on the thickness have been studied. The consumption of Au and Ti ions in the electrolytes during the electroplating process was measured by inductively coupled plasma-mass spectrometry (ICP–MS) method. The cross-section microstructures of coatings were studied by field emission scanning electron microscope (FESEM) with an energy dispersive spectroscopy (EDS) system. An optimized processing method has been put forward for the industry process to produce coatings with uniform thickness and good quality.