Electrodeposition nickel-phosphor

The actual reaction is more complicated than equation (12.1) becausephosphorous and protons are also reduced. As a result, a nickel phosphorous alloy rather than pure nickel is obtained. Under appropriate conditions, the reduction reactions only take place at the metal surface, which acts as a catalyst. Electroless plating thus produces a compact coating of uniform thickness all over the substrate surface. In contrast to electrodeposition, electroless plating can also be used with insulating substrates, such as polymers, the surface of which has been previously activated by a suitable catalyst. 

The codeposition of elements, such as phosphorus or boron, by direct interaction of the reducing agent with the catalytic surface was examined by some authors however, the interpretations are not completely satisfying. An indirect mechanism for hypophosphite reduction was proposed by Zeller and Landau.23 In this approach formation of phosphine as an intermediate and a direct interaction with radicals such as hydrogen atom H, hydride H , or NiOH was suggested.5, 12 24 26 However, the possible direct reduction of phosphite to phosphorous must also be considered. In favor of this hypothesis, there is the electrodeposition of NiP alloys from solutions containing Ni2+ and phosphite. The interaction of Ni2+ with the phosphite ions produces, at high pH, nickel phosphate precipitate when nickel ions are not adequately complexed. 

Summary. An STM study has been initiated to investigate the various processes associated with electrodeposition of Cu-Ni multilayers on Cu(100). The substrates were prepared by electropolishing in phosphoric acid followed by immersion in 10 mmol/1 HCl. A (V2 x V2)R45° adlattice of oxidatively adsorbed chlorine is formed under these conditions. The adlayer stabilizes the surface steps in the <100> direction which corresponds to the close packed direction of the chloride adlattice. In dilute (millimolar) solutions of cuprous ion, reduction occurs under mass transport control with the electrocrystallization reaction proceeding by step flow in the <100> direction. At more negative potentials chloride is partially desorbed. Coincidentally, the highly kinked metal steps become Mzzy and move towards adopting the close-packed <110> orientation of the metal lattice. Preliminary experiments on heteroepitaxial nickel deposition reveal regions where electrocrystallization on Cu(100) occurs via step flow in the <110> direction. 

Nickel was electrodeposited on polished brass foil at different temperatures (Ni deposit roughness with temperature). Also, Martis et a/. reported that compact nickel multiwalled carbon nanotube composites eould be electrodeposited on a copper substrate using the eutectic mixture ChCl/EG as solvent. Later, electrodeposition of Ni-P alloys (with tunable phosphorous eontent) at room temperature was reported by You and co-workers. ... 

---