Patent ID: 8304372
Filing Date: 2012-11-06
Classification: H01L

Abstract:
1. A process for joining oxide superconductors tubes with a superconducting joint, said process comprising the steps of: i) preparing separately water-based solutions of nitrates of Bi, Pb, Sr, Ca and Cu and mixing the above solutions together with Ag to obtain a single solution; ii) spray drying the resultant single nitrate solution mixture obtained in step (i) to obtain a spray dried powder; iii) calcining the spray dried powder obtained in step (ii) , followed by subsequent grinding and mixing to obtain a homogenous calcined powder; iv) cold isopressing the calcined powder obtained in step (iii) into large size tubes of length of up to about 500 mm, outer diameter up to about 150 mm and wall thickness in the range of 2 to 10 mm; v) sintering the cold isostatically pressed tubes obtained in step (iv) and grinding the sintered oxide superconductor tubes into powder, followed by mixing to obtain a homogenous partially preformed superconducting phase powder; vi) cold isopressing the partially preformed superconducting oxide powder of step (v) into tubes of different size; vii) grooving both end portions of the tubes of step (vi) and depositing metal silver layer on the grooves, followed by lapping one of the end faces of a pair of the tubes produced in step vi) and arranging them in close contact to each other by inserting a silver bush inside the contacting end portions of the tube pair and further applying a paste of intervening material on the lapped end faces; viii) physically contacting the coated end faces and wrapping the physically joined portion with a perforated silver foil and further depositing a silver layer by a metal spray gun and ix) heating the above combination of the joint portion and the tube pair, at a temperature in the range of 830°-850° C. in air, for a time period of 100-150 hrs to obtain the superconducting joint between a pair of tubes.