| 摘要 |
1290253 Electro-depositing niobium upon copper by melt electrolysis SIEMENS AG 26 March 1970 [29 March 1969] 15026/70 Heading C7B A Cu substrate e. g. cylinder coated with a Nb layer, for super-conducting resonators of particle accelerators or gate conductors for heavycurrent cryotrons, is produced by the melt electrolysis deposition of a Nb layer upon a Cu substrate which is stress-free, free of lattice defects and has a mean surface grain size of at least 1mm. The electrolyte which may be stirred, is preferably a melt of a niobium fluoride, e. g. 16.2% K 2 Nb F 7 , dissolved in a eutectic mixture of alkali metal fluorides, e.g. 10À5% NaF, 47À0% KF and 26À2% LiF, at 740-750‹C. A concentric cylindrical Ni anode may be used. To give the desired stress relief and recrystallized grain size, a Cu substrate having a relatively small surface grain size may be annealed e. g. at 800- 900‹C. for at least 2 hours under vacuum or protective gas e. g. A or He. If the Cu substrate remains in air after annealing, any oxide layer formed may be removed by anodic electro-polishing in aqueous H 2 PO 4 solution using a Cu cathode. A thick rough Nb layer may be electro-polished (as anode) in an electrolyte of 85% H 2 SO 4 and 15% HF, using a Nb cathode. |
