Papers by Author: Hiroyuki Shimizu

Abstract: The purpose of this study is to examine the basic characteristics of the single layer type microwave absorber in X band. Samples were produced from Bi system (2223) superconductor powder and metallic powder and inserted into a wave guide system where the complex reflection intensity was measured (The short circuit method) by using the vector network analyzer[1]. As the result, at the room temperature (300K), the reflection loss is apt to increase with increasing the content of the Bi system superconductor powder. Furthermore, the measured value of the reflection loss agreed with the value calculated from the complex permittivity εr* . At liquid nitrogen temperature (77K) where the superconductor powders are in the superconducting state, some differences occurred between the calculated value and the measured one of the reflection loss. For the metallic powders, copper powder showed good agreement between the calculated and the measured of reflection loss. For the magnetic material, it was concluded that the theoretical formula under consideration of complex permeability μr* should be derivated.

Abstract: In the study of the application of a laser technique on the bulk of press formed Bi system, the authors have reported that a superconductive layer can be obtained underneath the laser melted layer. In a continuing series of this study, this paper deals with the mechanical properties of the bulk laser treated. Superconductive powder of Bi system, 2223 phase was pressed to form a disk specimen of 2 mm thick and 10 mm at 29 MPa to 196 MPa. Then a CO2 laser beam of output power 6 W to 9 W was scanned linearly in air to melt the surface of the specimen to be subjected to the evaluation of hardness and fracture strength. The experimental results showed that the values of microvickers hardness of superconductive layer and melted layer are 135 and 105 respectively while that of the specimen as press formed is as low as 45. The fracture strength of the laser treated specimen was increased to 34 N from 15 N. The mechanical properties obtained deserve non sensitive handling in a practical use of the treated bulk.