Experimental laboratory methods have been developed that enable phase-equilibria studies to be carried out on slags in the system Ca-Cu-Fe-O in equilibrium with metallic copper. These techniques involve equilibration at temperature, rapid quenching, and chemical analysis of the phases using electron-probe X-ray microanalysis (EPMA). Equilibration experiments have been carried out in the temperature range of 1150°C to 1250°C (1423 to 1523 K) and in the composition range of 4 to 80 wt pct "Cu 2 O," 0 to 25 wt pct CaO, and 20 to 75 wt pct "Fe 2 O 3 " in equilibrium with metallic copper. Liquidus and solidus data are reported for the primary-phase fields of spinel (magnetite) and dicalcium ferrite. The resulting data have been used to construct liquidus isotherms of the CaO-"Cu 2 O"-"Fe 2 O 3 " system at metallic copper saturation.
The effect of addition of ultra-fine MgO particles, obtained by Mg combustion, in Bi-2212/Ag tapes was investigated. Bi-2212/Ag tapes were prepared by coating and partial melt processing. Four different methods of MgO particles embedment were applied in green tape preparation; settlement of MgO in Bi-2212, pre-mixing of MgO in the solvent, deposition of the MgO into the solvent, and deposition of MgO onto the surface of Bi-2212. Microstructural studies of processed tapes show that uniformity of MgO particles distribution in Bi-2212 matrix depends on the methods of tape preparation.MgO particles, introduced in Bi-2212 matrix by all applied methods, significantly enhanced transport properties of the tapes. The J c degradation with the increase of magnetic field and/or temperature in all doped samples was significantly lower compared to un-doped Bi-2212 samples. The best improvement was achieved when MgO particles were introduced into Bi-2212 matrix by settlement method of the tape coating. The improvement also depends on a magnitude of the magnetic field and operating temperatures.
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