Taihei Matsumoto

The influence of surface structure on wetting of α-Al2O3 by aluminum in a reduced atmosphere

Abstract An improved sessile-drop wetting experiment was performed in this study to investigate the wettability and adhesion of molten Al on three different oriented α-Al2O3 single crystals, R ( 01 1 2 ), A (11 2 0 ) and C(0001), over a wide temperature range from 800–1500 °C in a reduced Ar-3%H2 atmosphere. It is found that the wettability and adhesion between molten Al and α-Al2O3 are quite sensitive to the crystallographic orientation. The adhesion is much stronger for the molten Al on the R and A surfaces than that on the C surface. On the other hand, the adhesion on the reconstructed C- ( 31 × 31 ) R±9 ∘ surface is weaker than that on the relaxed yet unreconstructed C-(1×1) surface. The results suggest that in the reduced Ar-3%H2 atmosphere, the top layers of the R and A α-Al2O3 surfaces are oxygen-terminated while that of the C surface is aluminum-terminated, and the reconstructed C- ( 31 × 31 ) R±9 o surface is an oxygen-deficient structure based on the results of the work of adhesion.

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:

Development and properties of a Freeman-type hybrid ion source

In order to investigate the fundamentals of the deposition of ions with energies in the range of 10–100 eV, we developed Freeman-type hybrid ion source and a low-energy mass-analyzed ion beam deposition system. Analyzing the energy distributions of ions generated, we estimated the properties of the ion source. Energy distributions of noble gas ions (Ne+, Ar+, Kr+, Xe+), and metal ions (Ti+, Fe+, W+, C+) were measured by a PPM421 plasma process monitor with a cylindrical mirror analyzer and a quadrupole mass spectrometer. For instance, Ar+ ions transported at 25 keV were decelerated to 103 eV with an energy spread of ±3 eV, and Ti+ ions generated by sputtering of a titanium target had an energy distribution of 107±3 eV. The energy of ions generated by this apparatus was well defined, and so it is possible to investigate film formation processes by low-energy ions.

Reactive wetting of molten Al on different oriented α-Al2O3 single crystals at high temperatures

The reactive wetting of molten Al on three different oriented a-Al2O3 single crystals, Rð 01 1 Þ, Að 11 2 Þ and C(0 0 0 1), was investigated by an improved sessile drop method at temperatures between 1350 and 1500 � C in a reduced Ar–3%H2 atmosphere. The wettability is in the order of R > A > C. The spreading is reaction-limited and the rate is dominated by the change in the solid–liquid interfacial free energy per unit time. � 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Synthesis of titanium-chromium nitride composites by millimeter-wave sintering

New composites of Ti-Cr-N system were synthesized using a high power millimeter-wave heating method. Ti-Cr-N composites were synthesized from the powder mixtures containing metallic Ti and Cr2N under nitrogen atmosphere by 28 GHz millimeter-wave radiation. The composites consisted of (Ti,Cr)N, Cr2N with some amount of metallic Cr, and their hardness ranged from 9 GPa to 15 GPa, depending on the nitrogen pressure during sintering. In these composites, quite high oxidation resistance was found from their small weight gains less than 5 g/m2 in oxidation experiment in air at 1000 °C for 60 min. It was also indicated that a high pressure nitrogen environment is advantageous for the millimeter-wave syntheses of nitride composites with high oxidation resistance.

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.

Reactive wetting in liquid Cu alloy – carbon and silicon carbide systems

Wettability of carbon and SiC by liquid Cu – Si alloys was measured by the sessile drop method and was mainly investigated from a thermo-dynamical view point. Penetration phenomena of liquid Cu – Si alloy into porous carbon was also investigated. It was found that it is possible to expect whether wetting system or non-wetting system from thermo-dynamic calculation.