Hiroto Osono

Orientation Dependence of Flaking of Ion Irradiated Aluminum Single Crystals

Surface erosion on mono- and poly-crystalline aluminum, irradiated with 300-500 keV He+ or Ne+ ions at room temperature along the axial or off-axial directions, has been examined by SEM and TEM. The critical fluence at which flaking appears on the surface increased according to the order of the poly-crystalline sample, mono-crystals with surface normals of [111], [100] and [110]. On the contrary, flaking over multiple layers first appeared on a (110) surface. Results of skin-thickness measurements and microstructure observations suggest that flaking is basically caused by the coalescence of small bubbles which are created in a layer close to the projected ion range. The orientation dependence of the flaking was interpreted in terms of a difference in the depth profile of the bubble distribution associated with channelled ions. Some discussions are made concerning blisterling.

Effects of an external magnetic field on the flock size and sedimentation of activated sludge

Effects of an external magnetic field on sedimentation enhancement were investigated using three kinds of practical activated sludge. An indoor experiment was setup (3.5l aeration vessel) equipped with a broth circulation system and 800 G of external magnetic field. The application of an external magnetic field to the activated sludge enhanced the sedimentation irrespective of the nature of the activated sludge. At the same time, the flock size of the sludge was enlarged by the external magnetic field. However, the surface zeta potentials of the sludge were not changed by the external magnetic field. Addition of FeCl3 to the sludge enhanced the effects of the external magnetic field. Based on these results, the following mechanism for the enhancement of sedimentation by the external magnetic field is suggested: activated sludge containing iron was magnetized during entry to the magnetic field and coagulated with the magnetic force. As a consequence, the flock size was enlarged. Almost the same sedimentation enhancement by external magnetization was confirmed by a pilot scale magnetization system (2.0 m3 of aeration vessel) when the airlift type of mild broth circulation system was equipped with a 5000 G magnetic field.

Preparation of p-Type CdS Thin Film by Laser Ablation

A new method to prepare p-type CdS thin film was investigated, in which the laser ablation was applied to a mixed target of CdS and Cu. The p-type CdS film was obtained from a target containing more than 5 at% Cu. Composition analysis showed that Cu content in the film was about one-fifth of that in target. The formation of p-type CdS film was also confirmed by the photovoltaic effect of the p-n junction which was constructed by laminating n-type CdS film and p-type CdS film.

Thermal generation of vacancies in high-quality aluminium crystals

Abstract The dislocation density in high-purity (99.9999%) aluminium has been decreased to 105–107 m−2 by cyclic annealing. In such a crystal, there are only a few sources for vacancy generation, so that it is expected to take a long time to attain the thermal equilibrium concentration of vacancies. In order to study the generation rate of vacancies, the electrical resistance has been measured accurately at high temperatures. It is found that it takes at least several hours to attain the thermal equilibrium concentration. For comparison, generation profiles from pre-existing dislocations and interstitial-type dislocation loops are estimated with a diffusion-limited model. It is concluded that, even in a high-quality aluminium crystal, most vacancies are generated from pre-existing dislocations, and only a small fraction is generated by the growth of interstitial-type dislocation loops. The surface oxidizes at a rate of about an atom layer per an hour and is not effective for the generation of vacancies.

Stress-Induced Raman Frequency Shift in CuInSe2 Thin Films Prepared by Laser Ablation.

Thin films of CuInSe2 have been prepared by laser ablation using a Nd:YAG laser at substrate temperatures up to 450° C. Raman scattering experiments have shown that the frequency of the A1 phonon mode for these films shifts markedly to higher frequencies similarly with CuInSe2 single crystals under compression. The existence of compressive stress in the films has been confirmed by observing the bending of a cover glass used as substrate. The magnitude and temperature dependence of the stress estimated from the frequency shifts agree with those determined from the degree of bending.

Purification of 6N Aluminum by Ultrahigh Vacuum Melting

In order to improve the purity of 6N aluminum, it was melted in a vacuum of 3-6×10−6 Pa for 30 min and solidified gradually. The melted samples were cut into several pieces and the residual impurities of each part were analyzed by Glow Discharge Mass Spectrometry (GDMS). The Residual Resistivity Ratio (RRR) of each part was measured and the relationship of RRR with residual impurities is discussed. The purity of the melted sample was improved in comparison with that of the raw material, and the measured RRR almost doubled to 40000. GDMS analysis revealed that the amounts of elements of partition coefficient k 1 were not reduced. While each impurity concentration ratio in this study is about one-tenth of that in the previous report, the purification efficiency of each element in this study and that in the previous report matched well. Although the estimated RRR values from composition analyses were larger than the measured RRR values, both showed similar tendencies with regard to specimen position and also corresponded well with regard to impurity distribution.

Measurement of Plasma Flow of Mixture of Metal Vapor and Nitrogen in Shock Wave Deposition

The plasma flow of a mixture of metal vapor and nitrogen in shock wave deposition has been investigated by means of an image converter camera and a Mach-Zehnder interferometer at the shock velocity of υ=4.9~6.0 km/s with the initial pressure of P1=0.1~2.0 Torr. The separation of the shock front between N2 and Mo was observed at P1=0.1 Torr, but not at P11.0 Torr. The density of nitrogen molecules behind the shock front was measured to be 3.47×1017 cm-3 for P1=1.0 Torr and υ=4.9 km/s. The deposited films of MoN and TiN were found to be composed of fine-grained polycrystals with FCC structure, and their lattice constant was estimated to be 0.422 nm and 0.426 nm, respectively.