Transport critical current densities and n-values were measured at 4.2 K in fields up to 15 T on 7, 19, and 37-stack multifilamentary MgB 2 strands made using an in-situ route. Some strands included SiC additions (particle size ? 30 nm), while in others Mgrich compositions were used. Two basic multifilamentary variants were measured, the first had Nb filamentary barriers, the second had Fe filamentary barriers. All samples incorporated stabilizer in the form of Cu 101. Simple, one-step heat treatments were used, with temperatures ranging from 700-800?C, and times from 10-30 minutes. Transport critical current densities of 1.75 x 10 5 A/cm 2 were seen at 4.2 K and 5 T in 37 stack strands.
Highly textured YBCO bulk materials with dense stacking faults were prepared by the powder melting process (PMP). We re-annealed the samples at temperatures between 800°C and 900°C to reduce the stackimg faults inYBa,Cu,O.(123) crystals. The microstructural characteristics of these samples were investigated by SEM and EM, and their critical current densities were estimated from magnetization hysteresis loops. The results indicate that both the density of stacking faults and the J , values decrease considerably after the reheat treatments, The reasons for the elimination of stacking faults by annealing the specimens at high temperature are discussed.
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