The electrodeposition behavior of Zn-Fe alloy has been investigated by the partial polarization curves for alloy electrodeposition. The deposition of Fe was revealed to be suppressed under conditions such as a high concentration of Zn ions or a high electrolyte flow. Both of the conditions accelerate Zn electrodeposition. These results can be explained by the hydroxide (of Zn) suppression mechanism. In the case of solution pH, the change of pH to a lower value proved to suppress the deposition of both metals. This indicates the suppression of Fe is possible without an acceleration of Zn deposition. In addition to this, the suppression of Fe deposition under conditions with high electrolyte flow or lower pH was also observed in Fe single deposition. From these results, in addition to the hydroxide suppression mechanism, the mechanism of Fe single deposition was also proven to affect the deposition behavior of Fe when in a Zn-Fe alloy.
The electrodeposition behaviors of copper and tin from acid sulfate solution have been studied by electrochemical methods. The deposition potential of tin in the presence of copper (II) ion was more positive by 0.25V compared with that in the absence of copper (II) ion. The multilayers have been electrodeposited from acid sulfate baths containing copper (II) and tin (II) ions using potential pulse electrodeposition techniques. The positive potential of the pulse was-0.1V (vs. SCE) and the negative one was-0.35 V, and the retention times at each potential changed from 2 to 8s. The microstructure of the multilayers was examined by scanning electron microscopy and X-ray diffractometry. The multilayers consisting of sublayers with a thickness of 10nm order were obtained depending on the retention times. The sublayers deposited at-0.1V were pure copper and those deposited at-0.35V consisted of Cu, Cu3Sn and Cu6Sn5.
Micro-sputtering technique was applied to advanced etching method instead of conventional chemical methods for microscopic examination of metallic materials. It was necessary to produce precise microstructures by suitable etching, and the surfaces to be chemically etched were prepared after a 3-step coarse polishing process, that is, grinding using the polishing paper of 100, 60 and 30μm particles, followed by a further 3-step fine polishing process, that is, buffing using the diamond of 6 and 1μm particles and the alumina of 0.05μm particles. This paper describes the attempt to reduce the number of steps required during the polishing stage. Polishing with diamond of 6μm particles without use of diamond of 1μm particles and alumina of 0.05μm particles was performed. Consequently, when performing micro-sputtering for 10 minutes, shallow scratches left during polishing have disappeared completely, and a clear microstructure was shown. Moreover, by micro-sputtering for 20 minutes, although some scratches remained, there was no trouble in microstructual observation with the coarse polishing up to 30μm which means an appreciable reduction in polishing processes.
Direct electroless silver plating on copper metal from a succinimide complex bath using imidazole as the reducing agent was examined. Though the electroless silver plating from this bath is essentially an autocatalytic deposition, there is a problem in the properties and adhesion of the plated film because of the substitution deposition of silver due to the dissolution of the base copper metal that occurs during the first stage of plating. By adding glyoxylic acid, which is catalytically reacted on the copper surface to emit electrons, as the second reducing agent, the substitution deposition of silver was suppressed, the surface condition became dense and the adhesion was improved. It has been determined that the mixed potential theory can be applied to this reaction based on the result of the local polarization curve measurement.
A highly sensitive humidity sensor was prepared by the coating of epoxy resin on a quartz crystal sensor surface. The probe was adapted to a ventilated chamber-type apparatus for the measurement of water evaporation from human surfaces. In the range from 0 to 50% relative humidity (RH), the relationship between RH and resonant frequency showed good linearity with high resolution, ≤0.1% RH. By alternation between standard air (10% RH) and humidified air (12.5, 22.5, 32.5% RH), the time to reach steady state was determined to be less than 120 sec for both absorption and desorption processes. The frequency at the steady state was very stable. This newly developed humidity sensor was used to measure water evaporation rates from human forearm, cheek, palm of hand and ocular surface. The observed rates were 10.7±0.5, 35.0±1.3, 40.2±1.6 and 298.9±4.0g/m2·hr (mean±standard deviation) respectively. These values and regional differences were consistent with those previously reported. The sensitivity and responsiveness of the new probe was best seen when measuring evaporation from the ocular surface. After achieving steady state, oscillations of the resonant frequency coincided with blinks of the eye at 5 sec intervals. Therefore, this new system that utilizes an epoxy-coated quartz crystal sensor will very useful to evaluate dynamic changes of water evaporation rate. It may have both clinical and industrial uses.