Nickel coatings double-layer

In double-layer nickel coatings however, a flat-based pit is formed in the nickel coating, giving marked resistance to penetration to the basis metal. Figure 13.8 shows a pit in a double-layer nickel plus chromium coating after 58 months service. 

Fig. 13.8 Flat-based pit in double-layer nickel plus chromium coating after 58 months service ...

While the copper film acts primarily as a primer coating, which improves the stability of the following nickel layer or layers by its more noble character as well as the adhesion, the nickel film has direct protective properties. For this purpose, it must be deposited pore free, which demands a thicker film (>10 xm), or a double layer. In this case. 

This use was founded on the fact that KCN possesses the property of dissolving the salts of metals like gold, silver, and nickel, etc., the metal going into solution as a double cyanide. From these solutions the metal can be readily deposited electro-chemically in a coherent layer by making the surface of the object to be coated with the precious metal the negative pole in a solution of the double cyanide. 

Fig. 9.1 Schematic illustrating the preparation of metal-insulator-metal electrostatic nanocapacitors based on the double-gyroid morphology. Firstly, the DG templates are replicated via nickel electroplating. Subsequent to template dissolution the metal nanostructure is coated with a few nanometer thick electrictdly insulating alumina layer by ALD. Lastly, a liquified low-melting point tdloy is drop-cast onto the sample and allowed to infiltrate the mesopoies. The two interdigitated metal networks which ate separated by the electrically isolating metal oxide form the active volume V of the electrostatic capacitor...

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