Improved transport critical current properties in glycerin-doped MgB2 wire using milled boron powder and a solid-state reaction of 600 °C
Improved transport critical current properties in glycerin-doped MgB2 wire using milled boron powder and a solid-state reaction of 600 °C
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DOI：
10.1016/j.jallcom.2015.08.034
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发表时间：
2015-11
影响因子：
6.2
通讯作者：
B. Jun;Jung Ho Kim;Chan-Joong Kim;K. Choo
中科院分区：
文献类型：
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作者：
B. Jun;Jung Ho Kim;Chan-Joong Kim;K. Choo
同时采用铣削、碳(C)掺杂和固相反应三种效应来改善mgb2超导线的临界电流性能。采用球磨硼(B)粉和甘油处理硼(B)粉，研究了热处理温度（包括650 ~ 1000℃的常规固液反应和低于熔点（650℃）600℃的固液反应）对管中埋粉（PIT）加工MgB2/Fe线输运超导性能的影响。B粉的机械磨粉和液体甘油处理的目的分别是减小MgB2的晶粒尺寸和实现C均匀掺入MgB2。研究了在650 ~ 1000℃范围内热处理的mgb2丝的超导性能，并研究了即使在600℃低温固相过程中，是否也会发生C掺入，从而获得高晶界密度和C取代效应，从而提高超导性能。对不同热处理温度下制备的掺甘油MgB2/Fe金属丝的MgB2相形成、实际C取代量、半最大全宽（FWHM）、临界温度（Tc）、输运临界电流密度（Jc）的磁场依赖性和上临界场（Hc2）的温度依赖性进行了评价。在600°C的固态条件下，使用研磨B粉进行热处理的甘油掺杂MgB2wire在4.2 K时显示出在整个应用电场范围内最高的转运系数。结果表明，该合金的晶界密度较高，低温热处理过程中也发生了C取代，导致了较高的erjc。另外，与预处理后的B粉发生固-固扩散反应，结晶度较差，从而增强了hc2，改善了djc。
We adopted simultaneously three effects of milling, carbon (C) doping and solid-state reaction to improve critical current properties of MgB2superconducting wire. The influences of heat-treatment temperature, including a conventional solid–liquid reaction of 650–1000 °C and a solid-state reaction of 600 °C below the melting point (650 °C) of Mg powder, were examined on the transport superconducting properties ofin situpowder-in-tube (PIT) processed MgB2/Fe wires using ball-milled and glycerin-treated boron (B) powder. The aims of the mechanical milling and liquid glycerin treatment of the B powder were to reduce the grain size of the MgB2and achieve homogeneous C incorporation into the MgB2, respectively. The superconducting properties of MgB2wires heat-treated in the range of 650–1000 °C were investigated, and it was also investigated as to whether the C incorporation occurred even in a low-temperature solid-state process of 600 °C, thus resulting in an improvement of the superconducting properties by obtaining both high grain boundary density and C substitution effects. The MgB2phase formation, actual C substitution amount, full width at half maximum (FWHM), critical temperature (Tc), magnetic field dependence of transport critical current density (Jc) and temperature dependence of the upper critical field (Hc2) were evaluated for glycerin-doped MgB2/Fe wires fabricated at different heat-treatment temperatures. The glycerin-doped MgB2wire using milled B powder heat-treated at a solid-state of 600 °C showed the highest transportJcvalues at 4.2 K over the entire applied field regime. It was revealed that the grain boundary density was higher and that the C substitution also occurred by a low temperature heat-treatment process, which led to a higherJc. In addition, a solid–solid diffusion reaction with the pre-treated B powder resulted in poor crystallinity, which enhancedHc2and improvedJc.