Photoelectrochemical technique was applied to characterize the dispersion state of TiO2 particles in Ni-TiO2 composite films. Ni-TiO2 composite films were prepared by dispersion plating under various conditions, and when they were used as the photoelectrode in sulfuric acid solution, the differences in the dispersion of the TiO2 particles in the films modified the photocurrent-potential curve. The photocurrent obtained showed one peak (A) in the region of less noble potential and an ordinal increase (B) in the noble potential region. The increased exposure of TiO2 particles on the surface as a result of chemical etching caused an increase in photocurrent (B), and the thicker the film grew, the smaller its photocurrent (B) became. This is due to the fact that the TiO2 particles in the film acted as an electrical resistance. When composite films were formed under high plating current density, codeposition of TiO2 particles was suppressed and the corresponding photocurrent (A) was relatively small. The condensation of TiO2 particles in the film reduced the photocurrent park (A), but increased photocurrent (B). This behavior suggests that the first photocurrent peak (A) located in the less noble potential region corresponds to the photoelectrochemical dissolution of the nickel matrix, and that the second increase (B) located in the noble potential region corresponds to the photoelectrochemical oxidation (probably O2 evolution) on the TiO2 particles.
RF plasma nitriding of titanium was carried out at different temperatures and electric potentials of the samples, at 1.0-1.3 Torr in mixtures of nitrogen and hydrogen gases. The addition of hydrogen to nitrogen increased the nitriding rate and the hardness of the nitrogen diffusion layer. Kinetic study indicated that nitriding behavior changed in the temperature range between 1000°C and 1100°C. It is considered that the ε phase, which has the effect of suppressing nitrogen diffusion, is not present in samples nitrided at 1100°C. The nitriding rate decreased in samples with a positively biased potential. It is therefore inescapable nitrogen ions exerted some effect on the nitriding rate in these experiments. The nitrogen diffusion layer formed by plasma nitriding was harder than that formed by thermal nitriding. Hence, the nitrogen concentration in the nitrided layer in the plasma nitriding must be higher than that in the thermal nitriding.
An isotachophoretic method for determination of metal cyanide ions such as [Au(CN)2]-, [Ag(CN)2]-, and [Cu(CN)3]2- in gold, silver and copper plating solutions was proposed. Determination was carried out within 20 minutes by diluting the solution with water without any pretreatment. Inorganic ions such as cyanide ions, carbonate ions and hypophosphite, phosphite, phosphate and pyrophosphate ions, and organic compounds such as organic acids and chelates were determined simultaneously. Other than those for carbonate ions, the concentration values obtained by isotachophoresis were the same as those obtained by gravimetric and volumetric methods. These results suggest that impurities dragged in from pretreatment processes may also be determinable. The isotachophoretic method has been found to be of value for the control of plating solutions.
ZrC films were prepared on stainless steels by activated reactive evaporation, and their composition, crystal structure, surface and cross sectional morphology, intrinsic stress and hardness were investigated. The C/Zr ratio determined by EPMA was 0.85 at the C2H2 pressure of 1×10-4 Torr, and increased with the C2H2 pressure up to 4×10-4 Torr, where it reached 1.02. As C2H2 pressure incresased, the preferred orientation of the deposited films changed from (100) to random and the lattice constant gradually increased. The cross section of ruptured films exhibited a columnar structure and column thickness decreased at higher C2H2 pressures. Intrinsic stress was compressive at the substrate bias voltage of -2kV, and tensile at 0kV. The micro Vickers hardness of the films gradually decreased with increasing C2H2 pressure. The maximum value was 3300kgf/mm2, much higher than that of bulk ZrC.
Ti films were electrodeposited on SUS 304 stainless substrates by a pulse current method in an equimolar KCl-NaCl molten salt bath with K2TiF6. The influence of electrodeposition condition on the crystal orientation and morphology of the films was investigated by X-ray diffraction and scanning electron microscopy respectively. The orientation index of the Ti films varied with the temperature, electrolytic time, current density and pulse shape during electrodeposition. The morphology of Ti films consisted of well-crystallized grains, which changed rapidly above 1073K. The surface of the films became smooth in the presence of an anodic reverse current. Measurement of anodic polarization curves in 3% NaCl solution showed that the corrosion resistance of the films was almost the same as that of pure Ti sheets. It was found that films with Ti (011) preffered orientation had higher corrosion resistance than films with Ti (110) orientation.
Investigations were conducted on variations in the pll of solutions in the vicinity of a copper substrate by means of micro-electrode plated with Sb, on the resistance between a copper substrate and a tip of Luggin capillary by means of current interrupter electrolysis, and on the partial current density for nickel deposition by means of atomic absorption analysis of the deposits. The results indicated that with increasing current density the action of boric acid in nickel deposition changed from that of pH buffer in solution to that of inhibitor of the hydrogen evolution reaction. Variation in solution pH near the copper substrate in plating baths containing boric acid was always smaller than that in baths without boric acid, although the current efficiency of the former was lower than that of the latter at current densities below 1.0A/dm2. This effect is attributed to the pH buffering action of a complex formed between boric acid and nickel ion. At higher current densities (3.0 to 12.0A/dm2), on the other hand, the partial current density for hydrogen evolution was depressed more than that for nickel deposition in the presence of boric acid, and the current efficiency for nickel deposition was eventually enhanced to ca. 100% with increasing current density. This effect is attributed to the adsorptive interactions of boric acid at the electrode surface. In the absence of boric acid, however, solution pH near the copper substrate increased to ca. 6.5 in a fluctuating manner, resulting in the deposition of a green-black thin film consisting of a mixture of Ni(OH)2 and Ni metal, the surface of which had many cracks, and the morphology of rock covered with moss.
A study was conducted to elucidata the annealing conditions that will produce thermally stable dual phase alloy film, 54vol% Ni3Al phase of L12 structure and a solid solution of Ni containing 10mol%Al. Composite films of 100μm in thickness were prepared from a Watts-type Ni plating bath suspended Al particles of 9.2μm in diameter. Annealing at 1073K for 10.8ks resulted in the formation of thermally stable Ni-16mol%Al dual phase alloy film. X-ray diffraction showed the formation of Ni3Al phase after annealing for 0.06ks at 1073K. Compositional homogenization of the 10mol%Al solid solution, however, required annealing for 10.8ks. XMA images of Ni, Al and O as well as backscattered electron images showed fast grain boundary diffusion of Al and slow diffusion of Al into Ni grains, followed by compositional homogenization. Composite films of 5-28mol% Al were also prepared, and it was found that compositional homogenization of the solid solution proceeded very slowly when the Al content was below 16mol%.
It is known that oxides of copper, nickel, tin, etc. are reduced in hydrogen atmosphere at soldering temperature. In expectation of this hydrogen reduction effect, dull nickel electrodeposits were formed under excess current density to obtain nickel films containing hydrogen and their solderability was measured by meniscograph. The hydrogen content of the nickel electrodeposits, and their crystal structure, composition and morphology were analyzed and correlations between these parameters and solderability investigated. The results are summarized as follows. (1) Nickel electrodeposits formed under excess current density showed a marked improvement in solderability. (2) The crystal structure of the nickel electrodeposits was fcc and the preferential orientation changed with current density, but no correlation was found between solderability and orientation. (3) There was good correlation between the solderability of the nickel electrodeposits and their hydrogen content.
The mechanism of silver electrodeposition from a potassium iodide bath composed of 9.26×10-2mol/L of CH3SO3Ag, 2.0mol/L of KI, 0.00∼4.12×10-2mol/L of HBPSA (N-(3-Hydroxy-1-buthylidene)-p-sulfanilic acid) was examined by using a rotating disk electrode. The form of silver-iodide complex ion was estimated by the concentration dependence on the rest potential of Ag in an aqueous solution of potassium iodide. The form of the silver-iodide complex ion in the bath was either Ag2I64- or Ag2I75-. It is suggested that electrodeposition of silver from the potassium iodide bath proceeds according to the equations (i) and (ii), with (ii) being the ratedetermining step. Ag2Ix-x+2+e-→Ag+AgIy-y+1+(x-y)I-……(i) AgIy-y+1+e-→Ag+yI-……(ii)
Electroless solder plating by the displacement reaction has been investigated. The addition of free borofluoride and hydroxylamine both improved the stability and extended the life of the plating bath The plating bath reaction was initiated 10s after immersion of the copper substrate into the bath Deposition morphology after 1min of reaction was similar to the final equilibrium stage of the deposit. Wettability was decreased due to diffusion of copper at film thickness of around 0.5μm, but (film thickness of 4μm or more) wettability was excellent with no decrease observed
The effect of magnetic fields on the morphology of an initially electrodeposited nickel surface was investigated by photoacoustic spectroscopy (PAS). Scanning tunneling microscopy (STM) was also used to support the PAS data. Grain structure was found to be finer, and the surface smoother under magnetic fields. This tendency is attributed to the electromagnetic force (Lorent's force) exerted on the nickel ions, and to the fact that nickel is ferromagnetic substance.