The effects of hydrostatic pressure on the BSCCO compound for the OPIT procedure

Abstract

The effects of hydrostatic pressure on precursor core densification, densification of the billets for further processing, deformation at high strains and strain rates and core densities in composite wires and final tapes are demonstrated and discussed. The presence of a state of hydrostatic stresses has been shown to be preferential for ceramic density and not efficient for improving the texturing. The high-pressure effect is enhanced at elevated temperatures or when it is preceded by annealing. The ceramics were studied by XRD, SEM, EDX, ICP, microhardness, light microscopy and pycnometer methods.

Effects of the high-pressure treatment ofex situMgB2superconductors

“…The hydrostatic state of stresses within the workpiece enables us to deform brittle, hard to deform materials and is exceptionally useful for polycrystalline powder deformation sealed within metallic capsules [7,14,15]. Thus, it has shown its perfect applicability in the 'powder-in-tube' (PIT) processing of Bi-2223 [7,16] and in the present work on MgB 2 -type superconductors.…”

“…(ii) the manufacture (hydrostatic extrusion) of MgB 2 /metal jacket superconducting wires for further processing into tapes (especially at the early stages of deformation, where the overall billet sizes and the complex geometry exclude application of, for example, wire drawing) [6,7]; (iii) the high-pressure treatment (cold isostatic pressing (CIP) and hot isostatic pressing (HIP)) of the obtained bulk specimens in the form of pellets, wires or tapes to increase their performance [8].…”

Silver alloys used in composite BSCCO tapes: development of electrical and mechanical properties during manufacture

“…The results obtained on hydrostatically pressed rods [64] are good references for the powder compaction characteristics. Cold isostatically pressed Bi(Pb)-2223 powders with long cylindrical shapes give saturating values exceeding 90% dense for pressures above 300 MPa [64]. Moreover, the associated values of H V and of its gradient have large sample and grain sizes dependences.…”

“…Moreover, the associated values of H V and of its gradient have large sample and grain sizes dependences. For cylinders 2.6 mm in diameter, H V reaches 135 kg mm −2 at the surface and 100 kg mm −2 at the centre, which for larger diameters (4.5 mm) become 115 kg mm −2 and 160 kg mm −2 , respectively [64].…”

“…Monocore PIT Ag/Bi(Pb)-2223 composite billets with very dense powders (about 90%), by cold drawing, show a density drop to 60-65% with a parallel decrease of H V to 60-80 kg mm −2 [64]. Smaller reductions per pass result in larger decreases of density [8].…”