19芯Fe/Cu复合包套二硼化镁超导线制备及其超导性能研究

Fabrication of 19-filament Fe/Cu composite sheathed MgB_2 wire and its superconductivity

采用In-Situ PIT方法,以工业级低纯度B粉(92%)和镁粉(99%)为原料制备了19芯Fe/Cu复合包套MgB2超导线。断面扫描电镜观测表明,超导线内部超导芯分布排列均匀,Fe层都能完好包围MgB2芯体,Fe与Cu层结合紧密,填充因子0.17。750℃热处理1h后,样品超导转变温度Tc(onset)=33.5K,转变宽度ΔTc=4.8K。X光衍射检测发现,MgB2超导相中不存在其它Mg-B化合物杂项,但含有少量MgO和FeB2。多芯化后,超导芯中FeB2略有增加。四引线Ic测试发现,19芯样品在4.2K,4T时,临界电流密度为5622A/cm2,比单芯样品14400 A/cm2降低约2/3。

Using low purity of amorphouse B powder （92%） and Mg powder（99% ） as starting materials , 19 - filament Fe/Cu composite sheathed MgB2 wire with outer diameter 1.9mm was fabricated by the in situ powder - in - tube method. The sample was characterized using scanning electron microscope, X -ray diffraction and superconducting quantum interference device magnetometer, transition Jc and its magnetic dependence were evaluated by a standard four - probe technique. It is found that each filament surrounded by Fe chemical barrier is evenly distributed, no any obvious flaw can be detected in the interface between Fe and Cu, the filling factor of the wire reaches 0.17. The critical temperature and transition width are 35.5K and 4.8K, respectively. The sample after heat treatment of 750℃ for lh exhibits high purity of MgB2 with a small amount of MgO and FeB2 , and the content of FeB2 in 19 - filament sample increases compared to in mono - filament one. At 4.2K, 4T , the transport current density value, Jc for 19 - filament sample reaches 5622A/cm^2 , about 2/3 lower than that of mono filament sample （ 14400 A/cm^2 ）. The degradation of Jo for 19 - filament sample is attributed to the introduction of more FeB2.