Patents
An improved process for the preparation of oxide superconducting rods. The invention provides a process for the preparation of oxide superconducting rods. The process includes the steps of a cold isopressing process without the addition of binder, particularly thin and those based on Ag-added (Bi,Pb)2 Sr2 Ca2 Cu3 O10+x is disclosed. The main features of the process are the packing of partially preformed oxide superconducting powder obtained from spray drying a nitrate solution of Bi, Pb, Sr, Ca, Cu and Ag in a flexible rubber mould wrapped with a perforated metal sheet and whose inner surface is coated with olive oil, evacuating the packed partially preformed powder to remove trapped air and thereby reduces the defects and improves the subsequent cold isopressing to form rods; immediate cleaning the surface of the said rods so that no trace of olive oil is left; sintering initially the said rod in a silver tube/alumina sager, making silver metal contacts at both ends of the initially sintered rod; finally sintering the assembly of the said rod and both end silver metal contacts. The rods obtained according to these aspects show desired and consistent values of transport current not less than 36 amp, contact resistance not more than 0.015µOhm-cm2 at 77K in self field and fracture strength not less than 140 MPa.