Using commercial amorphous B powder (92% in purity) and Mg powder (99% in purity) as starting materials, 19-filament Fe/Cu clad MgB2 wires were fabricated by an in situ powder-in-tube method. Heat treatment was perfor...Using commercial amorphous B powder (92% in purity) and Mg powder (99% in purity) as starting materials, 19-filament Fe/Cu clad MgB2 wires were fabricated by an in situ powder-in-tube method. Heat treatment was performed at 700℃ for 1 h under an argon gas atmosphere. The influence of Mg/B ratio on the microstructure and superconducting properties of the wires was investigated. It was found that the major phases of MgB2 wires were MgB2 accompanied with relatively small amounts of MgO and Fe2B impurities. With 5% excess Mg addition, the onset TC slightly decreased. However, the transport JC at 4.2 K and 4 T reached 1.07×104 A·cm-2, increasing by a factor of 1.4 compared to the stoichiometric sample. Moreover, the Mg1.05B2 sample showed an improved field dependence of JC, suggesting that less voids and smaller grain size of the Mg1.05B2 core lead to better grain connectivity and stronger flux pinning.展开更多
基金the Beijing Municipal Science and Technology Commission (Grant No. Z07000300703)the State Key Development Program for Basic Research of China (Grant No. 2006CB601004)the National High Technology Research and Development Program for Advanced Materials of China (Grant No. 2006AA03Z203)
文摘Using commercial amorphous B powder (92% in purity) and Mg powder (99% in purity) as starting materials, 19-filament Fe/Cu clad MgB2 wires were fabricated by an in situ powder-in-tube method. Heat treatment was performed at 700℃ for 1 h under an argon gas atmosphere. The influence of Mg/B ratio on the microstructure and superconducting properties of the wires was investigated. It was found that the major phases of MgB2 wires were MgB2 accompanied with relatively small amounts of MgO and Fe2B impurities. With 5% excess Mg addition, the onset TC slightly decreased. However, the transport JC at 4.2 K and 4 T reached 1.07×104 A·cm-2, increasing by a factor of 1.4 compared to the stoichiometric sample. Moreover, the Mg1.05B2 sample showed an improved field dependence of JC, suggesting that less voids and smaller grain size of the Mg1.05B2 core lead to better grain connectivity and stronger flux pinning.
