Reduction of trace oxygen by hydrogen leaking during selective vaporization to produce ultra-pure cadmium for electronic applications |
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Authors: | S.T. Ali N.R. Munirathnam C. Sudheer R.C. Reddy M.R.P. Reddy T.L. Prakash |
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Affiliation: | Ultrapure Materials Division, Centre for Materials for Electronics Technology (C-MET), IDA, Phase-II, Cherlapally, HCL Post, Hyderabad, 500 051, India |
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Abstract: | A viable method utilizing leaking of high pure hydrogen gas into the distillation retort ambience maintained at 8.0 × 10− 3 Torr was devised to minimize the incorporation of trace oxygen in cadmium and the possibility of forming cadmium oxides during purification using selective vaporization. Hydrogen leaking at the rate of 5 standard cubic centi-metre per minute (sccm) during distillation at soaking temperature of 450 °C reduced trace oxygen from 230-350 ppm for raw cadmium of 3N8 (99.98%) purity and from 5-10 ppm for distilled cadmium of 6N purity. This can be compared to the presence of 30-38 ppm oxygen in cadmium distilled under simple-vacuum of 2.1 × 10− 3 Torr achievable in the system. A detailed comparison between distillation under simple-vacuum and hydrogen leaking is presented with reference to purity, distillation rate, soaking temperature, and mean free path of distillate vapors. |
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Keywords: | Electronic materials 6N (99.9999%) cadmium Selective vaporization Impurities and trace oxygen H2 reduction ICP-OES and O-N analysis |
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