Effects of intermediate deformation and thermal processing in the OPIT process upon critical current density of Ag/BiSSCO tapes
Critical current density, J/sub c/, of Ag/Bi(Pb)SCCO tapes in as-deformed and as-sintered states were studied at different stages of tape processing. Intermediate pressing and rolling result in significant I/sub c/ degradation. Non-zero I/sub c/ remains after the applications of pressing load up to 11 and 8 GPa following the third and first sintering, respectively. Under rolling conditions I/sub c/ remains non-zero up to maximum tape thickness reduction of 20%. Bending tests show that I/sub c/ reduction is the result of deformation-induced micro-crack formation which are easily healed during the first hour of the next sintering. Intermediate deformation after the first sintering cycle has been shown to accelerate significantly the 2212 to 2223 phase transformation during the first hours of the second sintering step. I/sub c/ growth during the first hour of the second sintering cycle is not connected with that phase transformation and is presumed to be the result of pinning ability and structure connectivity enhancement.
Uranium doping of silver sheathed bismuth-strontium-calcium-copper-oxide superconducting tapes for increased critical current density through enhanced flux pinning
A combination of uranium doping with thermal neutron irradiation has been well demonstrated to be one of the most effective means to introduce pinning centres in (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x /Ag tapes (Bi-2223/Ag). A substantial improvement in flux pinning and reduction of anisotropy in uranium doped Bi-2223/Ag tapes has been achieved due to thermal neutron irradiation. However, the radioactivity of the silver sheath is too high for practical application of this technique. This work aimed at minimising the detrimental effects of doping to allow for later irradiation and fission to create columnar defects for strong flux pinning. A number of uranium containing compounds, U 3 O 8 , U(Ca,Sr) 2 O 5 , and U(Ca,Sr) 3 O 6 have been identified in the U-Bi-Sr-Ca-Cu-O system. These equilibrium compounds have been synthesised and added to Bi-2223/Ag composite tapes in progressively greater amounts. The effects on the transport critical current density of Bi-2223/Ag of doping with a variety of uranium compounds up to 2 at% was determined. The compatibility and interaction between uranium compounds and the Bi-2223 matrix was systematically studied under various thermal processing conditions. Bi-2223/Ag doped with compounds using compositions closer to the equilibrium composition was shown to have superior superconducting properties to that doped with uranium oxide compounds. The effects of chemical degradation by uranium compound dopants via strontium and calcium removal from the Bi-2223 structure have been indirectly determined by critical current density (J c ) measurements. Losses in J c can be minimised by stabilising uranium into appropriate compounds.
Nonobstetric lower genital tract injuries in rural India
To study the impact of nonobstetric genital tract injury (NOGTI) in rural India.