Electroless Ni-B alloys composed of from 7 to 25at% B were prepared using a nickel-chloride plating bath containing dimethylamine borane (DMAB) as a reducing agent. The influence of conditions of preparation such as bath temperature (50-80°C), pH (5-8) and nickel-ion complexing agents (Na-succinate, Na-malonate and Na·K-tartrate) on the deposition rate and the boron content of the deposits was examined. Heat-induced structural changes in the deposited Ni-B alloys were also investigated by means of differential scanning calorimetry, evolved gas analysis, X-ray diffraction and transmission electron microscopy. The results are summarized as follows: (1) Boron content in the deposits was influenced by the species of complexing agent, with deposits from Na-succinate baths containing about 7 to 17at% B, those from Na-malonate baths containing about 16 to 21at% B and those from Na·K-tartrate baths containing about 21 to 25at% B. (2) Deposited alloys with about 7 to 10at% B were supersaturated solid solutions of fccNi with boron occluded, and those with about 15 to 25at% B were amorphous solids. (3) The process of crystallization of electroless Ni-B alloys can be classified into two types depending on boron content. In alloys with about 7 to 18at %B (region I), fine fccNi particle precipitated from an amorphous (or supersaturated solid solution) matrix at about 200°C and upon further heating the remained matrix was transformed into a stable phase of (Ni+Ni₃B) by eutectic crystallization at 300-400°C. In alloys with about 20 to 25at% B (region II), the amorphous solid converted directly into stable crystal phases of Ni₃B and Ni at 300-350°C.

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Measurements of pH near the cathode were performed using a composite antimony micro-electrode, consisting of an antimony electrode, an Ag/AgCl reference electrode and Luggin capilally tube, under galvanostatic conditions in baths of zinc chloride-potassium chloride (0-0.3M ZnCl₂+0-2.7M KCl+0-0.5M H₃BO₃; pH5.5) and zinc chloride-ammonium chloride (0.3M ZnCl₂+0-3.8M NH₄Cl; pH5.5). Electrode potentials were also measured against the same reference electrode simultaneously.
The change in pH was found to be correlated with the polarization curve, and in baths without organic additives, pH rose rapidly to 10 when the applied current density exceeded the limiting current. The addition of benzalacetone caused a considerable increase in both pH and polarization even at far less than the limiting current density, while the addition of nicotinic acid caused a decrease in pH and polarization. In the presence of excess ammonium ion, none of the precipitate occurred, due to the high stability of the zinc-ammine complex ion, even if bath pH was raised a-bove 11 by the addition of base, whereas in zinc chloride-potassium chloride baths zinc hydroxide began to precipitate at about pH5.8.
The fact that the range of current densities in which bright deposits were obtained from zinc chloride-potassium chloride baths was not so wide as in the case of zinc chloride-ammonium chloride baths is thought to be caused by the rapid rise in pH, which brought about the formation of zinc hydroxide on and near the cathode.

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The mechanical properties of copper films deposited from electroless plating baths containing glycine were studied by means of the tension test. The addition of glycine to the baths resulted in an increase in the elongation and ultimate tensile strength of the copper films. Under suitable conditions, the films obtained were shown to have nearly identical elongation and higher ultimate tensile strength, compared with electrodeposits from additive-free copper sulfate baths. The concentration of free formaldehyde that was not involved in the formation of a condensed compound from glycine and formaldehyde in the electroless plating baths was measured by the polarographic method. Good correlations were found between the concentration of free formaldehyde, the mechanical properties and the deposition rate.

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Effects of ultrasonic radiation on the deposition rate of chemical nickel plating and on the properties of the nickel deposit have been studied. The deposition rate of nickel was increased remarkably by ultrasonic radiation in citrate baths, but no such large increment was obtained in succinate baths. The enhancement of the deposition rate might be attributable to the diffusion controlled process in chemical nickel plating.
Ultrasonic radiation also influenced the crystallographic structure and hardness of the nickel deposits, and reduced the P content of the nickel deposits owing to the increased co-deposition of Tl. However, heat-treatment of the nickel deposits resulted in precipitation hardening due to Ni₃P formation.
The hardness of the deposits decreased with the ultrasonic radiation depending on the P content of the deposits. Changes in the properties of the nickel deposits with ultrasonic radiation was interpreted as a function of the P content of the nickel deposits.

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The effects of pH and the addition of Quadrol on the electrodeposition of Cu-Zn alloys from pyrophosphate baths were studied. Copper was preferentially deposited from the baths without Quadrol. Addition of Quadrol up to 0.3M and KOH caused a decrease in the Cu content of the deposits and a less noble shift in deposition potential. Consequently, deposits containing 70-80% Cu were obtained over a wide range of bath composition at pH of 11.0. The relation between the composition of deposits and deposition potentials was discussed on the basis of a potential-pH diagram for Zn in Cu 70%-Zn 30% alloy. Preferential deposition of Cu was suppressed when the deposition potential was sufficiently less noble for Zn to exist in the metallic form.

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