Kunisuke Hosokawa

Photoacoustic spectra of CdS detected from the unilluminated surface

The photoacoustic spectra detected from the reverse side of a CdS single crystal have been studied. Photoacoustic amplitude detected from the unilluminated surface is noticeably influenced by the sample absorption, namely the sample thickness, and there is an optimum value of the sample thickness. The phase variations in this method considerably depend on incident light wavelength, compared to the usual photoacoustic spectroscopy (PAS). The Rosencwaig and Gersho theory for the usual PAS has been extended to the reverse side detection of PAS. These theoretical results agree with experimental values, and predict the importance of the phase study in this method.

Thermal Wave Tomography with Ray-Optic Reconstruction

Thermal wave tomographic imaging of an aluminum sample with a new photopyroelectric detector is reported. The new detector can detect the local ac temperature field when it comes into contact with the back surface of a sample. Compared to the capacitively coupled detector, this detector is easier to handle and has increased sensitivity to the photopyroelectric signal. The effects of the laser beam modulation frequency and subsurface defects in the sample on the tomographic image have also been studied. It is revealed that the resolution of the tomograph increases with increasing modulation frequency and decreasing metal-tip diameter of the detector.

Detection of surface grooves and subsurface inhomogeneities in metals by transmission correlation photoacoustics

Correlation photoacoustics detected from the unilluminated surface of a sample have been studied to detect well‐characterized surface grooves and subsurface inhomogeneities in nickel. The correlation image of a line scan across an opaque sample by transmission technique can present the information on the surface or subsurface characteristics of the sample. This method is especially advantageous to detect subsurface grooves or inhomogeneities which exist anywhere in an optically opaque solid because the photoacoustic signals depend on the thermal and geometrical features in the transmission process of thermal waves. The system developed makes it possible to measure the impulse response of unstable samples because of the short time taken to collect data.

Study on Electroplating of Palladium-Nickel Alloy from Ethylenediamine Bath. I. Study by Potentiostatic Electroplating.

At pH 7, the occlusion of hydrogen in the alloy deposits decreased markedly compared to that in single deposits of palladium. Smooth, bright deposits could be obtained over a potential range of -0.7 to -1.1V vs Ag/AgCl. The palladium content of the alloy deposits increased with [en]/[M] ratio, whereas current efficiency decreased with increases in the potential and the ratio.When the [en]/[M] ratio exceeded 3 at pH 9, current efficiency decreased markedly due to the decrease in the deposition rate of nickel and the acceleration of hydrogen deposition. Palladium content showed its maximum value of 94% at a ratio of 3, and decreased at higher ratios. Smooth deposits could be obtained even at potentials as low as -1.1V from baths having a high [en]/[M] ratio at a pH above 8. This suggests that ethylenediamine acts not only as a complexing agent but also as a leveling agent.

Study on brass electrodeposition by pulse electrolysis from cyanide plating bath.

Pulse plating of Cu-Zn alloy from cyanide brass plating baths was investigated with respect to the effect of pulse electrolysis with galvanostatic square pulses on the potential-current curves, current efficiency and composition of brass deposit. It was found that pulse plating yielded a brass deposit of uniform composition with a brighter appearance and finer crystal grain than that obtained under direct current electrolysis, and that the effect of pulse plating at a high pulsed-current density was mainly influenced by the increased deposition overpotential and the off period in each cycle where there is zero current in the external circuit. It was also noted that the electrodeposition mechanism changed from the regular type to the irregular type with increasing pH in the vicinity of electrode surface, since high pulsed current electrolysis resulted in a greatly increased hydrogen evolution reaction.

Photoacoustic and Photoluminescent Studies on Fe2O3 Semiconductor Electrode

The non-radiative and radiative processes of electrons have been investigated by photoacoustics and photoluminescence to elucidate the photoelectrochemical response of ferric oxide electrodes in 0.1 N NaOH electrolyte.