Nickel electroplated deposition

Nickel may also be prepared by electrolysis of ammoniacal, acidified, or neutral solutions of its salts, a process that is used commercially for electroplating.5 It is precipitated by zinc from ammoniacal solutions of its salts, and is left as a residue on igniting either the oxalate or the double nickel ammonium oxalate. Solutions of nickel salts are reduced by hydrogen when heated under pressure, metallic nickel being precipitated out of solution.7 Thus a N/5 solution of nickel sulphate deposits metallic nickel at 186° C. in the presence of hydrogen at 100 atmospheres pressure, whilst a similar concentration of nickel acetate deposits a pure nickel under like conditions at 168° C. 

To investigate the effect of the nanostructure on the electrochromic performance of NiO, transparent devices were assembled from nontemplated and DG-structured films with a FTO counter electrode and a 1M KOH(aq) electrolyte, see Fig. 6.9a. The active electrode material used was limited in area to 0.95mm. During the nickel electroplating process limiting the deposition area improve the control and quality of the deposit. 

As already mentioned, electroless coatings arc harder than conventional electroplated articles and as a result the wear resistance is increased. This property restricts the ductility of the deposit, with elongation values of 1-3% being found for electroless nickel. The residual stress is far higher than that of a selphamate nickel electroplate and is generally tensile, which can be a serious hazard in certain industrial situations where crack propagation has to be avoided at all costs. 

The bath model is prepared (as described above), made electrically conductive, and put into a sulphamate nickel bath for an electroplated deposition. Depending on the size, geometry and required wall thickness, the model stays between three to seven weeks inside the electroplated hath including disruptions (to renew auxiliary anodes and insert covers). When reaching the required wall thickness, the process is ended and the mold shell is ground to the outer contour. If necessary, the flange surfaces have to be milled, and fixed bore holes have to be drilled. After thermal or chemical demolding of the bath models, the inner contour is cleaned, the mold is measured, values are compared to the CAD data, and a defined surface treatment is applied. 

In electroless deposition, the substrate, prepared in the same manner as in electroplating (qv), is immersed in a solution containing the desired film components (see Electroless plating). The solutions generally used contain soluble nickel salts, hypophosphite, and organic compounds, and plating occurs by a spontaneous reduction of the metal ions by the hypophosphite at the substrate surface, which is presumed to catalyze the oxidation—reduction reaction. 

Nickel [7440-02-0] Ni, recognized as an element as early as 1754 (1), was not isolated until 1820 (2). It was mined from arsenic sulfide mineral deposits (3) and first used in an alloy called German Silver (4). Soon after, nickel was used as an anode in solutions of nickel sulfate [7786-81 A] NiSO, and nickel chloride [7718-54-9] NiCl, to electroplate jewelry. Nickel carbonyl [13463-39-3] Ni(C02)4, was discovered in 1890 (see Carbonyls). This material, distilled as a hquid, decomposes into carbon monoxide and pure nickel powder, a method used in nickel refining (5) (see Nickel and nickel alloys). 

Aqueous Electrodeposition. The theory of electro deposition is well known (see Electroplating). Of the numerous metals used in electro deposition, only 10 have been reduced to large-scale commercial practice. The most commonly plated metals are chromium, nickel, copper, zinc, rhodium, silver, cadmium, tin, and gold, followed by the less frequendy plated metals iron, cesium, platinum, and palladium, and the infrequendy plated metals indium, mthenium, and rhenium. Of these, only platinum, rhodium, iddium, and rhenium are refractory. 

Cadmium, cobalt, copper, and nickel sulfamates react with lower aHphatic aldehydes. These stable compositions are suitable for use ia electroplating solutions for deposition of the respective metal (see Electroplating). 

Electrodeposition of Metals. Citric acid and its salts are used as sequestrants to control deposition rates in both electroplating and electroless plating of metals (153—171). The addition of citric acid to an electroless nickel plating bath results in a smooth, hard, nonporous metal finish. 

The ideal electroless solution deposits metal only on an immersed article, never as a film on the sides of the tank or as a fine powder. Room temperature electroless nickel baths closely approach this ideal electroless copper plating is beginning to approach this stabiHty when carefully controUed. Any metal that can be electroplated can theoretically also be deposited by electroless plating. Only a few metals, ie, nickel, copper, gold, palladium, and silver, are used on any significant commercial scale. 

Nickel. Worldwide, nickel used in electroplating has averaged about 63,500 t annually from 1980—1990 (9). The United States uses about 18,000 t/yr, and Europe about the same quantity Japan consumes about 9,000 t, and another 9,000 t is used by the other Pacific rim countries. Canada and South America are reported to use about 4500 t aimuaHy. Electroforming apphcations consume another 4500 t of nickel worldwide. About half of this electroforming is done in the United States and Canada. Nickel deposited from autocatalytic solutions was estimated to account for 1600 t of nickel on a worldwide basis (10) in 1990. Nickel averaged 3.65/kg ia early 1993 (see Nickel and nickel alloys). 

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