Zone refining of 99.99999 % aluminum and the enlargement

利用低温泵（CRYO-U6）和辐射温度计（IR-AQITG I型）构建了半自动区域精炼装置。可在稳定状态下长期使用。该装置的极限压力为2.7 × 10 ~（-1）<-8>Pa。在高温下，由于石墨释放出大量气体，装置的真空变得更差。然而，可以在1 × 10 - 4Pa的真空下，<-7>通过在操作之前烘烤舟皿来进行铝的区域精炼。使用该装置，进行了标称纯度为99.999%的铝的区域精炼。熔融区的长度和移动速度分别为3cm和5.5cm/h。重复10次区域通过。与油扩散泵区熔法相比，该方法获得的铝表面覆盖有一层薄的氧化膜，具有金属光泽，并通过测量残余电阻率比值（R_<300K>/R_<4.2K>）来检验区熔法的效果。在精制块的顶端，该比率约为2 × 10^4，但在尾端，该比率突然下降。原因可能是石墨舟或石英管的污染，因为铝表面上的氧化膜很薄。用四极质谱仪对区域精炼过程中的气氛进行了分析，识别出H_2、H_2O、CO、CO_2和碳氢化合物。由本装置精炼的铝释放的氢的量变为使用油扩散泵精炼的铝释放的氢的量的一半，因此使用低温泵对于除去气体杂质是有效的。目前还没有成功地获得99.99999%的铝，但通过对铝原材料、石墨舟、石英管等的选择，相信可以达到纯度。

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.