Ryukiti R. Hasiguti

Internal Friction and Related Properties of the TiNi Intermetallic Compound

Internal friction and elastic moduli of the intermetallic compound TiNi were measured as a function of temperature from −170° to 800°C. There appear in the internal friction curve two well‐defined peaks at −70° and 600°C, respectively, a small peak at 350°C, and a group of several sharp peaks in the temperature range from −50° to 40°C. The elastic modulus has a positive temperature coefficient in the temperature range from 40° to 520°C. These results are discussed in terms of the crystal‐structure model of Wang and others.

Annealing of γ-ray irradiated N-type germanium

Abstract Isochronal and isothermal annealing above room temperature has been studied in antimony and arsenic doped γ-irradiated germanium. Three annealing stages are found at 370, 430 and 530°K with activation energies of 0·7–0·8 eV, 1·2–1·3 eV and 2·2 (As-doped)–2·5 (Sb-doped) eV, respectively. Impurity dependence of annealing behavior is found in all these stages. The results are discussed in terms of electronic and elastic interactions of defect centers with impurity atoms.

A Theory of Migration Energies of an Interstitial in Germanium and Silicon

The migration energies of an interstitial in germanium and silicon were calculated using attractive polarization energies and Born-Mayer type repulsive energies. The results are 0.25 eV and 0.22 eV for germanium and silicon, respectively. These values should be considered to be the upper limit values of migration energies.

Investigation of Ti Interstitials in Slightly Reduced Rutile (TiO2) by Means of Channeling Method

To investigate the defect structures of slightly reduced rutile (TiO 2 ) channeling experiments were performed on a slightly reduced specimen and a stoichiometric one with about 6 MeV protons accelerated by a cyclotron. In an angular scan of the backscattering yield of protons from Ti ions with respect to the [001] axial channel, a peak along the [001] direction was observed only in the reduced specimen. By the analysis of the angular scan it was confirmed that main defects in a slightly reduced rutile are Ti interstitial ions. They are located within about 0.4A of the [001] mid-channel axis. This result supports the interpretation of EPR experiments that a so-called C -center is a Ti interstitial ton.

Impurity Trapped Interstitials and the Low Temperature Annealing Stages of Irradiated Copper

A semi-empirical method was developed to evaluate interaction energies of close impurity-atom-interstitial pairs. It was found that an undersize impurity atom provides with a deep trap for an interstitial, while an oversize impurity atom furnishes to an interstitial several shallow traps with different interaction energies. These results were applied to the annealing temperature problem of irradiated copper. Stage II was interpreted as due to the liberations and annihilations of several kinds of shallow trapped interstitials, and stage III was explained as due to the liberations and annihilations of deep trapped interstitials.

Japanese program of materials research for fusion reactors

Abstract The Japanese program of materials research for fusion reactors is described based on the report to the Nuclear Fusion Council, the project research program of the Ministry of Education, Science and Culture, and other official documents. The alloy development for the first wall and its radiation damage are the main topics discussed in this paper. Materials viewpoints for the Japanese Tokamak facilities and the problems of irradiation facilities are also discussed.

Thermally Induced Acceptor Centers in Germanium

In crystals with a very small dislocation density such as in germanium, a long time is necessary to obtain an equilibrium concentration of Schottky-type defects. This is verified by successive-quenching experiments. Analysis of the equilibration process of acceptor centers in n-type germanium at high temperatures gives the activation energy of about 2.0 eV. The formation energy of the thermally induced acceptors is found to be roughly 2 eV from the saturation values of the introduction curves of acceptors. Preliminary results of annealing of thermal acceptors are also described. The results are discussed in terms of vacancies thermally induced into the crystal.

Thin layer VLS growth, its cessation and morphologies of Cd crystals with Bi impurities

Abstract Hexagonal prismatic Cd crystals having a hemispherical tip were grown by means of the thin layer VLS mechanism, in which 30–40 wt% of Bi was localized in an alloy liquid phase in the thin skin layer of the hemispherical tip. As the Bi content in the thin skin layer was decreased to a few tenths of a wt%, the VLS growth ceased, and changed to VS growth, which resulted in a flat basal plane instead of the hemispherical tip. The growth rates were measured during the VLS and VS growth processes in connection with the morphology changes. It was found that the VLS growth rate was higher than the VS growth rate by about one order of magnitude.

Surface morphology of VLS Cd and Zn crystals grown in Helium inert gas atmosphere

Abstract Surface microtopographs were taken from VLS Cd and Zn crystals grown in a helium inert gas atmosphere and were compared with those taken from crystals grown in vacuum. During growth in vacuum, the impurity element caused the {10 1 0} and {10 1 1} fac es to become flat or striated. When these faces are flat during vacuum-growth, they contain a cavity during growth in a helium inert gas atmosphere due to the effect of the diffusion field. However, the striated faces during vacuum-growth exhibited striations also during growth in a helium gas atmosphere but without any cavity. The presence of the cavity is explained by the advancement of the “curved” steps toward the center of the face. A similar movement of the “straight” steps (striations) would not have produced any cavity.

Internal Friction Peaks of Cold Worked Dilute Copper Alloys

The internal friction of cold worked dilute copper alloys (Cu-Ag and Cu-Au) is studied in the temperature range between -150°C and +140°C with an inverted torsion pendulum. The internal friction peaks which appear in cold worked pure copper are suppressed by the addition of solute atoms. In place of them two new peaks P a and P b are found at about -125°C and -60°C, respectively, in silver doped specimens, while no new peak is observed in gold doped ones. Detailed investigations are carried out on the behavior of the peak P b , which is interpreted to be due to thermal unpinning of dislocations from pinning silver atoms. The behavior of the other peaks is also described.