Yasuo Otoguro

Gamma Irradiation Effect on a Bi1.5Pb0.5Sr2Ca2Cu3O10 Superconductor

A Bi1.5Pb0.5Sr2Ca2Cu3O10-y ceramic was sequentially irradiated with 60Co γ-rays of 1.5 MRh-1 in dose rate up to a dose of about 50 MR at ambient temperature, and the electrical resistivity was measured as a function of temperature. The critical superconducting transition temperature of 103.4 K increased to 104.1 K at 20.25 MR, and then decreased at a rate of 2.0×10-2 K/MR on further irradiation. Concurrently, the electrical resistivity at 300 K increased almost linearly with a rate of 0.1 µQm/MR in the dose range of about 2 to 20 MR, and the resistivity was little changed by the irradiation to about 37 MR.

Electron Irradiation Effects on the Transport Critical Current Density in a Bi1.5Pb0.5Sr2Ca2Cu3Ox Ceramic

A Bi1.5Pb0.5Sr2Ca2Cu3Ox ceramic was sequentially irradiated with 3 MeV electrons at a dose rate of 2.5×1017 m-2s-1 up to a dose of 2.0×1020 m-2 at ambient temperature, and the transport critical current density was measured as a function of temperature. The critical current density in zero field at temperatures below 65 K was increased by irradiation to 1.0×1020 m-2, and the radiation effect was more prominent at lower temperature. Upon further irradiation to 2.0×1020 m-2, the critical current density was reduced in the low temperature regime to a level less than the preirradiation value.

Oxidation and hot-corrosion resistant high aluminum austenitic stainless steel

A new type of austenitic stainless steel has been developed containing 5 pct Al and forming a protective Al2O3 film. This steel is free from oxide film spoiling and exhibits a greater oxidation and hot corrosion resistance than any other conventional austenitic stainless steels. By adjusting the Ni content and the addition of Ce and/or Ti, its manufacturability, workability and weldability have been improved to the point that this steel is now equal in quality to commercially available stainless steels. Formation of Al2O3 film requires the removal of the internal oxidation zone brought about by hotworking and welding, prior to being subjected to high temperatures. Abnormal oxidation also takes place in this steel, but has a less effect than in conventional ferritic CrAl steels.

Transport Critical Current Density in a Bi1.5Pb0.5Sr2Ca2Cu3O10 Ceramic

The transport critical current density of a Bi1.5Pb0.5Sr2Ca2Cu3O10-y ceramic was measured as a function of temperature in the range from 90 to 20 K under a magnetic field up to 1.0 T. A critical current density of 2.0 MAm-2 at 77 K in zero field increased almost linearly to 8.3 MAm-2 with a decrease in temperature to 50 K, and then to 11.7 MAm-2 at 20 K. When the current density was measured at 20 K in the zero field after applying a magnetic field of 1.0 T at low temperature, the critical current decreased to 8.6 MAm-2. The decrease in the critical current density induced by the magnetic field at 20 K recovered gradually with an increase in temperature to approximately 70 K.

Enhancement of the Transport Critical Current Density by Electron Irradiation in a Bi1.5Pb0.5Sr2Ca2Cu3Ox Ceramic

A Bi1.5Pb0.5Sr2Ca5Cu3Ox ceramic was sequentially irradiated with 3 MeV electrons at a dose rate of 8.9×1015 m-2s-1 up to a dose of 1.8×1020 m-2 at ambient temperature, and the transport critical current density was measured under a magnetic field up to 0.64 T as a function of temperature. The critical current density in zero field was increased by irradiation up to a dose of 1.8×1020 m-2 at temperatures below 45 K. The critical current dcnsity measured under magnetic fields was also enhanced by electron irradiations, which was larger at lower temperature and lower magnetic field up to 0.16 T.

Gamma irradiation effect on the transport critical current density of a Bi1.5Pb0.5Sr2Ca2Cu3Ox ceramic

A Bi1.5Pb0.5Sr2Ca2Cu3Ox ceramic was sequentially irradiated with 60Co γ-rays at a dose rate of 2.0 MRh-1 up to a dose of 24 MR at ambient temperature, and the transport critical current density was measured as a function of temperature. The critical current density in zero field was decreased by 2 MR irradiation at temperatures below 65 K, and the radiation effect was more prominent at lower temperature. The radiation effect was enhanced and extended to higher temperature upon further irradiation; the decrease in the critical current density was apparent at temperatures below 77 K after γ-irradiation to 24 MR.