KOSUGI Toshio Hiroshima Univ. Lab. Crytal Physics, Fac. Research Associate, 理学部, 助手 (10153545)
NAKAMICHI Isao Hiroshima Univ. Lab. Crytal Physics, Fac. Research Associate, 理学部, 助手 (40142335)
HASHIMOTO Eiji Hiroshima Univ. Lab. Crytal Physics, Fac. Associate Professor, 理学部, 助教授 (50033907)
|Budget Amount *help
¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 1989: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1988: ¥5,000,000 (Direct Cost: ¥5,000,000)
A semi-automatic zone-refining apparatus was constructed with a cyro-pump (CRYO-U6) and a radiation thermometer (IR-AQITG type I). It is available to use under a stable condition for a long time. The ultimate pressure of this apparatus is 2.7x10^<-8> pa. Vacuum of the apparatus becomes to worse at a high temperature by release of a lot of gas from a graphite. However, it is possible to perform zone refining of aluminum under vacuum of 1x10^<-7> Pa, by baking out of the boat before the operation.
Using this apparatus, zone-refining of aluminum with a nominal purity of 99.999 % was performed. Length and the traveling speed of the molten zone were 3 cm and 5.5 cm/h, respectively. Zone passing was repeated 10 times. The surface of aluminum thus obtained was covered with a thin oxide film, and has a metallic brightness, comparing with one zone-refined using an oil diffusion pump.
Residual resistivity ratio (R_<300K> /R_<4.2K> ) was measured to check the effect of zone refining. The ratio was about 2x10^4 at the top end of the refined block, but it decreased suddenly for the tail end. The reason may be a contamination from then graphite boat or the quartz tube, because the oxide film on the surface of aluminum is thin. Atmosphere during then zone refining was analyzed with a quadrupole mass spectrometer, and H_2, H_2O, CO, CO_2, and hydro-carbon were recognized. Amount of hydrogen released from the aluminum refined by the present apparatus becomes a half of that from aluminum refined using an oil diffusion pump, therefore the use of cryo-pump is effective to eliminate gas impurities. It is not succeeded to get 99.99999 % aluminum at the present, but it is believed to attain the purity by the selection of original material of aluminum, graphite boat and quartz tube, etc.