The structure of noncrystalline electrodeposited Ni–P alloys, 73.8–81.4 at.% Ni, has been investigated by x‐ray scattering and by physical density measurements. The x‐ray interference functions, I(k), are qualitatively inconsistent with those calculated for fcc‐, hcp‐, and Ni3P‐type crystallites. Calculated radial distribution functions RDF(r) indicate that the alloys have a better defined short‐range order than that observed in liquid noble metals above their melting points. The observed I(k) are very similar to the I(k) calculated by Dixmier, Doi, and Guinier [in Physics of Noncrystalline Solids, J. A. Prins, Ed. (North‐Holland Publ. Co., Amsterdam, 1965), p. 67] from their model. However, the parameters needed to fit the experimental results are inconsistent with the atomic sizes expected for nickel and phosphorus. The noncrystalline alloys are between 0.6% and 1.4% less dense than the corresponding mixtures of fcc Ni and Ni3P, both of which are essentially close packed. A grain boundary density defici...

Structural Investigation of Noncrystalline Nickel‐Phosphorus Alloys

Electroless nickel-plating on AZ91D magnesium alloy has been investigated to understand the effect of substrate microstructure and plating parameters. The initial stage of the deposition was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray analysis on substrates plated for a very short interval of time. The early stage of growth was strongly influenced by the substrate microstructure. Plating was initiated on b-phase grains probably due to the galvanic coupling of b and eutectic a-phase. Once the b-phase was covered with the coating, it then spread onto eutectic a and primary a-phase. The coating produced with the optimised bath showed 7 wt.% phosphorus with a hardness of approximately 600–700 VHN. The optimum ligand to metal ion ratio was found to be 1:1.5, while the safe domain for thiourea (TU) was in the range of 0.5–1 mgyl. Fluoride was found to be an essential component of the bath to plate AZ91D alloy with an optimum value of 7.5 gyl. The presence of 0.25–0.5 mgyl mercapto-benzo-thiosole (MBT) found to accelerate the plating process. 2003 Elsevier B.V. All rights reserved.

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Electroless nickel-plating on AZ91D magnesium alloy: effect of substrate microstructure and plating parameters

Crystallisation kinetics and phase transformation behaviour of electroless nickel–phosphorus deposits with high phosphorus content

The formation and stability of amorphous alloys are discussed in terms of the configurational entropy and in connection with the potential barrier, Δμ. The structure analysis of amorphous alloys using Bernal's dense random packing model (D.R.P.) shows quite good agreement with the actual observations. These results indicate that some degree of short range order (∼ 15 A) exists in amorphous metallic alloys, which is slightly different from the arrangement expected in a liquid. The model still shows a continuous structure without the formation of internal boundaries between ordered regions such as is characteristic of polycrystals. Although the D.R.P. does not completely reflect the structure of amorphous alloys, it is still an attractive model in understanding the amorphous state. These subjects are reviewed in this article.

Amorphous structures and their formation and stability

Electrodeposition of nanoporous nickel oxide film for electrochemical capacitors

An analysis was made of the structure of the Ni deposit produced by the catalytic Ni reduction process. X‐ray and electron diffraction revealed that the Ni deposit was an amorphous solid. The structure appeared to be unrelated to and independent of the nature of the substrate and thickness of the deposit.Metallographic examination revealed a dense material, free of voids, and perfect conformity to the substrate surface profile. Etching produced a lamellar structure, the variation in etching intensity being interpreted as variations in dissolved P. In platings, the lamellae lay parallel to the plane of the substrate. Growth faults were observed traversing the thickness dimension from substrate surface irregularities. The amorphous structure reverted to a crystalline phase mixture of Ni and at low temperatures with a large heat evolution.

F. Schossberger

Papers

Structure of Chemically Deposited Nickel