Papers by Author: Faizah Md. Salleh

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Authors: Baktiar Musa, Ahmad K. Yahya, Faizah Md. Salleh, R. Abd-Shukor
Abstract: This paper reports on the effects of Ag addition on physical properties of high temperature superconductors DyBa2Cu3O7-δ (Dy123). A series of the Dy123 - Agx composite was prepared by solid state reaction method with varying amount of metallic silver (x = 0 – 0.3). Resistance versus temperature measurement was done using the four-point-probe method in the temperature range of 79 K to 300 K. Pure DyBa2Cu3O7-δ was found to superconduct with Tc onset of 91 K and Tc zero of 78 K. Addition of Ag at x = 0.05 caused both Tc onset and Tc zero to increase to 93 K and 84 K, respectively. However, Tc onset and Tc zero dropped for higher silver contents. We found that the optimum silver content in DyBa2Cu3O7-δ for best superconducting behavior and hardness is between x = 0.05 and 0.10. Microstructure analysis using SEM and EDAX showed that most of the silver is uniformly distributed along the grain boundaries filling the pores and hence increasing the hardness of the samples.
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Authors: Faizah Md. Salleh, Ahmad K. Yahya, M.H. Ismail, M.H. Jumali
Abstract: In this study, single-core and multi-core Tl1212 tapes were fabricated from Tl-1212 superconducting powder of Tl0.5Pb0.5Sr1.8Yb0.2CaCu2O7 starting composition derived by conventional solid state synthesis. Single core tapes showed maximum Jc and enhanced 1212 phase formation were achieved for tapes annealed at a higher temperature for a longer duration. Multi core tapes showed a general increase in Ic and Jc with the number of tapes core. The highest Jc of 521 A/cm2 was observed for the 4-core tapes annealed at 870 °C for 90 minutes. The initial drastic drop of the tapes Jc in low magnetic fields (≤1T) indicates limitation on tapes performance by weak links. The low Jc of the tapes may be due to the lack of texture in the tapes core as revealed by SEM.
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Authors: Faizah Md. Salleh, Ahmad K. Yahya, Mohammad Hafizuddin Haji Jumali
Abstract: The superconducting Tl0.8Bi0.2Sr2Ca0.8Y0.2Cu2O7 powder prepared from chemical route was mixed with varying amounts of nano-sized MgO powders (x=0 to 0.50 wt. %) to form bulk superconducting composites. XRD results show that the addition of 0.15 wt.% nano-MgO is accompanied by an increase in 1212-phase and the disappearance of SrCO3 impurity. SEM investigations revealed more regular-shaped and smaller grains microstructure for MgO added samples in contrast to MgO-free sample which revealed irregular shaped grains. EDS showed homogenous distribution of Mg for all MgO-added samples with the exception of x=0.50 where agglomeration of MgO particles were observed. However, MgO added samples exhibit lower zero-resistance critical temperature, Tc zero than the MgO-free sample.
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