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.
Deformation-dominated texturing of superconducting filament in OPIT-fabricated Bi(Pb)SCCO-2223/Ag composite tapes
Texture formation in the ceramic filament of Ag/BiSCCO tapes was studied after cold rolling, uniaxial cold pressing and sintering by XRD /spl theta/-2/spl theta/ and /spl omega/-scan methods. More effective texturing of the outer layers as compared to that of the core interior was observed at the early rolling steps up to about 65% reduction in area. Texture inhomogeneity over the filament cross section is related to the inhomogeneous distribution of plastic deformation. Work hardening due to plastic deformation of non-sintered powder results in the broadening of X-ray peaks and an increase in microhardness. The recovery of these parameters occurs after annealing at the temperatures of 350-600/spl deg/C. The /spl omega/-scan studies revealed an improvement of c-axis texture by intermediate rolling compared to that in the as-sintered and pressed states. Deformation-induced texturing of the 2212-precursor is the main factor responsible for the texture of the final 2223-phase. The influence of Ag during the sintering stage is limited only to the outer layers of the filament; in the case of low preliminary deformation internal layers remained practically non-oriented.
Creating the Virtual Universe
Simulation software is important to our understanding of the universe. The intrinsic multiphysics aspects are spiced with a range of temporal scales and spatial scales, both of which cover more digits than are available in the standard hardware. This, together with the intrinsic chaotic nature of many physical processes, poses quite a challenge. To meet this challenge, researchers developed the Astronomical Multipurpose Environment (AMUSE). Instead of writing a suite of multiphysics solvers from scratch, AMUSE's developers coupled existing solvers for each physical ingredient. The result is a highly inhomogeneous collection of dedicated solvers with a homogeneous protocol that scales to supercomputers.