Akio Chiba

New composite composed of boron carbide and carbon fiber with high thermal conductivity for first wall

Abstract A new composite was created from B 4 C powder and carbon fiber by hot-pressing at 1700°C or more. The composite sintered at 1700°C with 20–35 vol% B 4 C shows a thermal conductivity of 250 W/m·K at 25°C which is slightly lower than the felt type C/C, but its value becomes higher than the C/C at temperatures above 400°C. The composite with 40 at% B shows more controllable recycling properties than B 4 C. The erosion yield for the composite is about half the yield for graphite at 800 K. After electron beam irradiation in order to test heat resistance no cracks were detected up to 22–23 MW/m 2 leading to a surface temperature of 2500°C.

Electrical properties and microstructure of CuO ceramics containing small amounts of alkaline earth elements

In order to develop suitable materials for ceramic resistors as a final target, basic investigation about electrical properties and microstructure of CuO ceramics doped with some amounts of alkaline earth oxide was performed. The resistivity of CuO ceramics containing additives (MgO, SrO, BaO) with a certain concentration range were lower and showed peculiarly better near linearity in a high applied field of 500 kV/m compared with that of non-doping CuO ceramics. Results of microstructure and crystalline phase analyses of these samples indicated that the additive small grains, whose size was sub-micrometer order, were present dispersively into the CuO grains. Such the change of microstructure of CuO ceramics was thought to induce the peculiar electric properties.