Hiroyuki Nezu

Effects of saccharin and aliphatic alcohols on the electrocrystallization of nickel

The effects of saccharin and three kinds of aliphatic alcohols (n-propyl alcohol, allyl alcohol, propargyl alcohol) on the surface morphology and crystal orientation of electrodeposited nickel from a Watts bath (1 M NiSO4 + 0.21 M NiCl2 + 0.51 M H3 BO3 have been studied by means of electrochemical methods, scanning electron microscopy, energy-dispersive X-ray analysis and measurements of X-ray diffraction patterns. Saccharin and three kinds of aliphatic alcohols were adsorbed on the electrode and inhibited the reduction of nickel ion. The inhibitory effect on the reduction of nickel ion increased in the order n-propyl alcohol, allyl alcohol and propargyl alcohol. Large granular electrodeposits were obtained from the Watts bath in the absence of organic additives. When saccharin was added, fine-grained crystals were observed and the surface roughness was relatively small. When aliphatic alcohols were added, the size of surface morphological features became smaller in the order n-propyl alcohol, allyl alcohol and propargyl alcohol. Fine-grained, compact and smooth nickel electrodeposits, which had a preferred orientation with a (111) plane parallel to the surface, were obtained from the Watts bath containing both saccharin and propargyl alcohol.

Surface morphology and crystal orientation of electrodeposited tin from acid stannous sulphate solutions containing various additives

The changes in surface morphology and crystal orientation of electrodeposited tin from acid stannous sulphate solutions containing 1 mm N,N-bis(tetraoxyethylene)octadecylamine (TOGA) and various concentration (0.2–2 mm) of benzalacetone (BA) have been studied as functions of electrolysis time or BA concentration by electrochemical methods, scanning electron microscopy and X-ray diffractometry. The inhibitory effect on the reduction of the tin (II) ion became stronger with increasing concentration of BA. In the presence of both TOOA and BA, when electrolyses were carried out at the more negative potentials than the reduction potential of BA, the reduction product of BA induced reticular crystals (network structure) of tin over the whole surface. This structure appeared in the early stage of electrolysis and exhibited an intense (200) diffraction peak. On the other hand, the crystal grain size and the surface roughness of electrodeposited tin became smaller with increasing concentration of BA from 0.2 to 2 mm. Further, fine-grained and smooth electrodeposits of tin were obtained from acid stannous sulphate solutions containing TOOA and high concentration of BA due to the synergistic effect of these adsorbed species.

Potential oscillations during the electrocrystallization of cadmium from alkaline cyanide solutions under galvanostatic conditions

Abstract The potential oscillations during the electrocrystallization of cadmium from alkaline cyanide solutions have been studied under galvanostatic conditions. The current-potential curve under potentiostatic conditions showed a limiting current which was caused by the diffusion control of the cadmium complex ion with natural convection. Potential oscillations were observed when the electrolyses were carried out at current densities which were above the limiting current on the current-potential curve. In these cases, hydrogen bubbles were evolved periodically from the cathode surface. The potential oscillation during the electrocrystallization of cadmium results from the following processes: (i) The surface concentration of cadmium ion is decreased after the beginning of galvanostatic electrolysis. (ii) When its concentration becomes nearly zero, the potential shifts rapidly from a positive value to a negative one, which is the potential of hydrogen evolution on cadmium metal. (iii) Hydrogen bubbles are evolved from the cathode surface. (iv) The surface concentration of cadmium ion is restored close to the bulk concentration by forced convection due to the evolution of hydrogen bubbles. (v) The potential shifts from a negative value to a positive one. Thus, the potential oscillation repeats with constant amplitude and period.

Effects of aromatic carbonyl compounds on the surface morphology and crystal orientation of electrodeposited tin from acid stannous sulfate solutions

The effects of three kinds of aromatic carbonyl compounds [cinnamaldehyde(CA), benzalacetone(BA), 2-acetonaphthone(AN)] and N,N-bis(tetraoxyethylene)octadecylamine(TOOA) on the surface morphology as well as crystal orientation of electrodeposited tin from acid stannous sulfate solutions have been studied by means of electrochemical methods, scanning electron microscopic observation and measurements of X-ray diffraction patterns. The inhibitory effects of the reduction of tin(II) ion became stronger in the order BA, CA and AN in the case of oxidant, and in the order CA, AN and BA in the case of reductant. The differences in the inhibitory effects between the oxidant and reductant became greater in the order of AN, CA and BA. Block-like crystals were observed on the whole surface by adding TOOA. Plate-like, needle-like or dendritic crystals were observed but compact electrodeposits could not be obtained by adding carbonyl compounds alone. On the other hand, compact and smooth electrodesposits of tin which had a preferred orientation with the (100) plane parallel to the surface were obtained from acid stannous sulfate solutions containing TOOA and BA.

Synergistic effects of benzalacetone and benzophenone on the electrocrystallization of tin from acid stannous sulphate solutions

The synergistic effects of two kinds of aromatic ketones (benzalacetone (BA), benzophenone(BP)) and N,N-bis(polyoxyethylene)octadecylamines (POOA) on the surface morphology and the crystal orientation of electrodeposited tin from acid stannous sulphate solutions have been studied by electrochemical methods, scanning electron microscopy and X-ray diffractometry. BA itself had no effect on the reduction of tin (II) ions, but the reduction product of BA had a strong inhibitory effect on the reduction of tin (II) ions. However, the inhibitory effect of BP was stronger than that of the reduction product of BP. POOA induced a uniform deposition of tin over the whole surface, but the crystal grain size and the surface roughness of electrodeposited tin were relatively large. On the other hand, fine-grained and smooth electrodeposited tin, which had a preferred orientation with the (10 0) plane parallel to the surface, were obtained from acid stannous sulphate solutions containing POOA, BA and BP due to the synergistic effects of the three kinds of adsorbed species. It was found that BA has a levelling action and BP has a grain refinement action.

Synergistic effects of adsorbed species on the surface morphology and crystal orientation of electrodeposited tin

The synergistic effects of adsorbed species (polyoxyethylenealkylamine (POAA), diphenylamine-crotonaldehyde reaction product (RP) and benzalacetone (BA)) on the surface morphology and crystal orientation of electrodeposited tin from acid stannous sulfate solutions have been studied by means of various electrochemical methods, scanning electron microscopic observation and measurements of X-ray diffraction patterns. Needle-like or columnar electrodeposits of tin were obtained from acid stannous sulfate solution in the absence of adsorbed species. On the other hand, fine-grained, smooth and compact electrodeposits of tin, which had a preferred orientation with the (200) plane parallel to the surface, were obtained from acid stannous sulfate solutions containing POAA, RP and BA due to the synergistic effect of the three kinds of adsorbed species. It was found that POAA acts to produce a uniform tin deposition over the whole surface, RP acts as a grain refiner and BA has a leveling action.

EFFECTS OF N,N-BIS(POLYOXYETHYLENE)OCTADECYLAMINES ON THE ELECTROCRYSTALLIZATION OF TIN FROM ACID STANNOUS SULFATE SOLUTIONS

Abstract The electrochemical characteristrics of three kinds of N,N -bis(polyoxyethylene)octadecylamines (POOA) and the effects of POOA on the surface morpholoy as well as crystal orientation of electrodeposited tin from acid stannous sulfate solutions have been studied by means of various electrochemical methods, scanning electron microscopic observation and measurements of X-ray diffraction patterns. The three kinds of POOA were absorbed on the electrode in the range of potential from 0 to −1.50 V, and POOA adsorbed on the electrode inhibited the electrochemical reduction of tin(II) ion. Needle-like, or columnar, electrodeposits of tin were obtained from acid stannous sulfate solution in the absence of organic additives. On the other hand, block-like or granular crystal which exhibit the (101) plane parallel to the surface were observed on the whole surface by adding POOA. It was found that the three kinds of POOA induce a uniform deposition of tin over the whole surface, and the grain size of crystals as well as the surface roughness of electrodeposited tin become smaller with increasing the chain-number of oxyethylene in POOA.

Effects of aromatic carbonyl compounds on the electrocrystallization of zinc from acid sulfate solutions

Abstract The electrochemical characteristics of N,N-bis(decaoxyethylene)octadecylamine(DOOA) and the three kinds of aromatic carbonyl compounds [cinnamaldehyde(CA), benzalacetone(BA), 2-acetonaphthone(AN)] as well as the effects of such organic additives on the electrocrystallization of zinc from acid sulfate solutions have been studied by means of various electrochemical methods and scanning electron microscope observations. DOOA and three kinds of carbonyl compounds were adsorbed on the electrode. DOOA adsorbed on the electrode as a quaternary ammonium ion strongly inhibited the electrochemical reduction of the zinc ion. BA or AN had a stronger inhibitory effect on the reduction of zinc ions than CA. Large plate-like electrodeposits of zinc (sides 3–10 μm) were obtained from acid sulfate solutions in the absence of organic additives. On the other hand, needle-like or fibrous crystals were observed on the whole surface by adding DOOA alone. Small block-like or granular crystals (sides 1–2 μm) were observed on the whole surface by adding BA or AN alone. Further, fine-grained, smooth and compact electrodeposits of zinc were obtained from acid sulfate solutions containing DOOA and BA or DOOA and AN.