Masayoshi Kamai

Measurement of surface tension of molten copper using the free-fall oscillating drop method

The surface tension of molten copper was measured by the oscillating drop method using a falling droplet. The surface oscillation of the droplet was quite simplified during the falling, and consequently, the surface tension was calculated using Rayleighs equation. The measurements were carried out in a wide temperature range including the undercooling state. The obtained surface tension of copper is expressed as follows:

Characterization of r.f.-sputtered zirconia coatings☆

Abstract R.f.-sputtered zirconia coatings with alumina and yttria were characterized by X-ray photoelectron spectroscopy, electron spin resonance and thin film X-ray diffraction. From the X-ray diffraction results, the as-deposited zirconia coatings were found to be amorphous and they remained amorphous after annealing at 1123 K for 15 min. It was deduced from the X-ray photoelectron spectroscopy results that zirconium ions in the amorphous zirconia coating possess a higher net charge than that of ions in ordinary ZrO2. Further, the formation of electron- trapped centres was indicated by the observation of an electron spin resonance absorption at g = 1.97. Crystallized zirconia coatings seem to be less resistant to corrosion than as-deposited zirconia coatings, as inferred from acoustic emission analysis. It was found that crystallization leads to a marked decrease in the loss tangent of the sputtered zirconia coating.

Inductively-coupled-plasma-assisted planar magnetron discharge for enhanced ionization of sputtered atoms

The effects of combining an RF inductively coupled plasma (ICP) with a conventional planar magnetron sputtering discharge have been investigated. The planar magnetrons discharge is assisted by the ICP, which is sustained by a helical RF coil immersed in the plasma. Use of the technique significantly enhances the plasma density and the sputtering discharge current. Optical emission measurements of Al ions and neutral lines indicate marked enhancement of ionization of the sputtered atoms after they pass through the dense ICP region.

Oscillating drop method using a falling droplet

An improved oscillating drop method was developed to measure the surface tension and viscosity of a liquid without any external forces using a falling droplet. Simple surface oscillation is observed for a falling droplet and the simple basic principles are applicable without any correction. The surface oscillation of a falling droplet was precisely measured using the combination of a laser, cylindrical lens, and line sensors. Measured surface tension and viscosity of water shows good agreement with previously reported values.

Inductively coupled reactive high-density plasmas designed for sputter deposition

Abstract Two types of inductively coupled RF high-density plasmas designed for sputter deposition in an external magnetic field are studied experimentally. One is helicon wave excited plasma in a magnetic field for cylindrical target sputtering. The other is planar magnetron discharge assisted by an inductively coupled plasma. The plasmas are produced using helical antennas with azimuthal mode number of m=0. Plasma characteristics are studied in Ar and reactive gases such as N2, H2 and/or O2. An RF wave field is measured and the excitation of helicon waves in a magnetic field is clarified in the production of high-density plasmas. Spectroscopic measurement of plasma emissions in the planar magnetron discharges indicates remarkable increase of ionization of sputtered particles when it is assisted by an inductively coupled plasma.

Estimation of Intrinsic Contact Angle of Various Liquids on PTFE by Utilizing Ultrasonic Vibration

The contact angle measured using the sessile drop method is typically an advancing contact angle, which is often used for the evaluation of wettability. However, the precise measurement of the contact angle on rough substrates has been required for developing various industrial processes. In this study, a new measuring method by achieving the minimum total free energy by ultrasonic vibration (USV) was developed. The new method has been demonstrated for different rough surfaces, droplet volumes, and wettability conditions. The advancing contact angle significantly decreased when the USV is applied, but it immediately increased after stopping the USV. In order to capture the droplet behavior at the beginning and end of the USV, a high-speed camera was used. The contact angle was apparently a receding contact angle after stopping the ultrasonic vibration. Accordingly, the intrinsic contact angle was estimated using the values of the advancing contact angles obtained before applying the ultrasonic vibration and the receding contact angles obtained after stopping the ultrasonic vibration.

Electromechanical properties and characterization of zirconia-alumina and alumina coatings☆

Abstract Zirconia-alumina and zirconia coatings containing yttria were prepared by magnetron r.f. sputtering and plasma-spraying methods. Electromechanical properties of the coatings were studied using acoustic emission and dielectric loss measurements. Furthermore, the coatings were characterized using scanning electron microscopy, X-ray diffraction method and IR spectroscopy.

Miniaturization of FSW equipment using counterbalanced tool concept

Much attention has been paid to FSW as a useful joining process that provides superior characteristics compared with conventional fusion welding. However, the FSW equipment must have a high stiffness due to the applied load and the tool torque, which increases the size of the equipment. Therefore, it is difficult to use the FSW technique for repairs on site. In this study, the relationship between the FSW parameters and the process loads was investigated for the FSW with a counterbalanced tool to show the possible miniaturization of the equipment. The results revealed that the counterbalanced tool concept was effective for the miniaturization of the equipment because it reduces the applied load and the tool torque during the FSW.