Nickel layer

Hard plating is noted for its excellent hardness, wear resistance, and low coefficient of friction. Decorative plating retains its brilliance because air exposure immediately forms a thin, invisible protective oxide film. The chromium is not appHed directiy to the surface of the base metal but rather over a nickel (see Nickel and nickel alloys) plate, which in turn is laid over a copper (qv) plate. Because the chromium plate is not free of cracks, pores, and similar imperfections, the intermediate nickel layer must provide the basic protection. Indeed, optimum performance is obtained when a controlled but high density (40—80 microcrack intersections per linear millimeter) of microcracks is achieved in the chromium lea ding to reduced local galvanic current density at the imperfections and increased cathode polarization. A duplex nickel layer containing small amounts of sulfur is generally used. In addition to... 

If a sample of polycrystalline material is rotated during the sputtering process, the individual grains will be sputtered from multiple directions and nonuniform removal of material can be prevented. This technique has been successfully used in AES analysis to characterize several materials, including metal films. Figure 9 indicates the improvement in depth resolution obtained in an AES profile of five cycles of nickel and chromium layers on silicon. Each layer is about 50 nm thick, except for a thinner nickel layer at the surface, and the total structure thickness is about 0.5 pm. There can be a problem if the surface is rough and the analysis area is small (less than 0.1-pm diameter), as is typical for AES. In this case the area of interest can rotate on and off of a specific feature and the profile will be jagged. 

Decorative coatings of nickel plus chromium are cathodic to steel or zinc alloy substrates and with these protective systems deliberate use may be made of discontinuities in the chromium topcoat where corrosion of the underlying nickel will occur. If the number of these discontinuities in the chromium layer is greatly increased the current density at each individual corrosion site is reduced, penetration of corrosion through the thickness of the nickel layer is thus slowed down and the period of protection of the substrate metal is prolonged. 

Fig. 13.9 Triple-layer nickel deposit consisting of semi-bright and bright nickel layers with a thin, highly activated layer of nickel between them (after Reference 23)...

A crack count of 30-80 cracks/mm is desirable to maintain good corrosion resistance. Crack counts of less than 30 cracks/mm should be avoided, since they can penetrate into the nickel layer as a result of mechanical stress, whilst large cracks may also have a notch effect. Measurements made on chromium deposits from baths which produce microcracked coatings indicate that the stress decreases with time from the appearance of the first cracks . It is more difficult to produce the required microcracked pattern on matt or semi-bright nickel than on fully bright deposits. The crack network does not form very well in low-current-density areas, so that the auxiliary anodes may be necessary. 

Distance upstream end of wall to gas port 0.5 mm Nickel layer thickness > 200 nm... 

Our recent our works show that even higher activity and stability can be demonstrated by the three-layer electrodes with nickel layer, active in the oxygen evolution, middle layer with catalyst, active in the oxygen reduction (Mn02, pyropolymer or a perovskite), and a diffusion (waterproof) layer,... 

The nickel layer is removed and used to make pressings of the CD onto plastic discs. The plastic pressings are then coated with aluminum to make the finished CDs. 

In electronic applications, where it is common to deposit copper and/or copper alloy and tin in sequence, with a nickel diffusion barrier layer, 0.5 fim thick, between the layers present, no failure occurs. Without the nickel layers between bronze/-copper/tin layers themselves, for instance, intermetaUic brittle layer(s) and Kirkendall voids are formed, leading eventually to separation of the coated system and substrate. 

Also, when tin-containing solder connections are made to copper, intermetaUic materials are formed. Those continue to grow to render weak surfaces. Again, a nickel layer between the substrate and the solder provides a solution to this problem. 

Core (Earth) A spherical nickel-iron body at the center of the Earth. The core is divided into inner and outer sections. The outer core is a molten iron-nickel layer at about 2900 to 5100 km below the Earth s surface. The inner core is the central shell of the Earth, which is solid and extends from a depth of about 5100 km to the very center of the Earth at a depth of 6370 km. 

Scanning electron microscopy (SEM) images were taken with an AMRAY, 1800 series scanning electron microscope having a resolution of 0.2 pm. All objects in this work, except the silicon wafer microreactor, were first sputtered with a nickel layer a few nanometers thick in order to obtain an SEM image. 

FIGURE 2.7 Etch profiles of microchannels obtained by wet etching (a) and dry reactive ion etching (b). In (a), the more rounded profile was obtained with direct wet etching using a PDMS channel mold (50 im in width), whereas the trapezoidal profile (dotted curve) was made with the deposited nickel layer as the etch mask (150 im in width) [125]. Reprinted with permission from Elsevier Science. 

Deposition of a nickel layer hy fluidized bed CVD can improve sintering in powder metallurgy applications. The process can he used as a premixing step of the composite, for example on W particles. A similar technique can also he used to improve the wettabilty of ceramics like SiC hy the molten A1 during the fabrication of metal matrix composites. ... 

Fig. 10 Schematic drawing of the Ni-terminated octopolar reconstruction of NiO(l 11). Small circles stand for Ni atoms and the large ones for O atoms. The first and second planes are respectively 75% and 25% vacant. The arrows indicate the basis vectors of the p(2x2) surface lattice mesh. The symmetry related radial relaxations 5,5 and 5 are respectively represented around apex atoms labeled 1 and 2 by dashed and dotted arrows and applies to the second oxygen and the third nickel layers that are patterned. (Right) Side view of the octopolar reconstruction and of the two first relaxations and Q perpendicular to the surface plane.

Lustrous adhesive nickel layers can be obtained from baths containing nickel sulfamate, nickel chloride, boric acid, or dimethylformamide (DMF). At 60 °C, current densities of 3 A/dm can be reached [152]. 

It should be noted that the nickel layer formation at the sample surface was found to begin only after the pore filling. Referring to Fig. 1, the decrease of the surface potential corresponds to the beginning of the nickel formation at the sample surface. When a continuous nickel film is formed, further increase in the deposition time results in the increase of the film thickness, and the surface potential becomes stabilized (Fig. 1, deposition time of2500 s and more). 

Third, an electric current is passed through the solution. The current causes nickel to come out of the solution. The nickel is then deposited on the surface of the steel. The longer the current runs, the more nickel is laid down. The thickness of the nickel layer can be controlled by the time the electric current runs through the solution. 

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