Understanding the densification process of Bi2Sr2CaCu2Ox round wires with overpressure processing and its effect on critical current density.
Understanding the densification process of Bi2Sr2CaCu2Ox round wires with overpressure processing and its effect on critical current density.
复制标题
了解过压处理 Bi2Sr2CaCu2Ox 圆线的致密化过程及其对临界电流密度的影响。
DOI：
10.1088/0953-2048/29/10/105005
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发表时间：
2016
影响因子：
3.6
通讯作者：
Hellstrom,EE
中科院分区：
文献类型：
--
作者：
Matras,MR;Jiang,J;Larbalestier,DC;Hellstrom,EE
超压（OP）处理通过收缩2212细丝周围的周围Ag基质来增加Bi2Sr2CaCu2Ox（2212）圆线的临界电流密度（μ JC），使它们接近全密度并大大增加2212晶粒连接性。事实上，致密化是至关重要的，以达到最高的J. C在这里，我们调查的时间和温度的依赖性的线致密化。我们发现，在50 atm和100 atm的OP压力下完全热处理后，丝的直径减小了3.8μm ±0.3%。在50 atm的OP压力下，丝在700 ℃以上开始致密化，并在820 ℃下2h后达到3.30μ m±致密化是均匀的，并且在熔化之前不改变长丝形状。在820 ℃下观察到非超导相的生长，这表明在熔化2212粉末之前在高温下的时间应最小化。对开放端2.2 m长电线样本的研究表明，距离开放端约1 m处达到完全致密化和高OP JC（JC在2.2 m长电线上变化约3.1倍），从而表明线圈长度电线可以通过在每端添加至少1 m的牺牲电线来保护电线免受密封泄漏的影响。
Overpressure (OP) processing increases the critical current density () JC of Bi2Sr2CaCu2Ox (2212) round wires by shrinking the surrounding Ag matrix around the 2212 filaments, driving them close to full density and greatly increasing the 2212 grain connectivity. Indeed densification is vital for attaining the highest J. C Here, we investigate the time and temperature dependence of the wire densification. We find that the wire diameter decreases by 3.8± 0.3% after full heat treatment at 50 atm and 100 atm OP. At 50 atm OP pressure, the filaments start densifying above 700 C and reach a 3.30± 0.07% smaller diameter after 2 h at 820 C, which is below the melting point of 2212 powder. The densification is homogeneous and does not change the filament shape before melting. The growth of non-superconducting phases is observed at 820 C, suggesting that time should be minimized at high temperature prior to melting the 2212 powder. Study of an open-ended 2.2 m long wire sample shows that full densification and the high OP JC (JC varies by about 3.1 times over the 2.2 m long wire) is reached about 1 m from the open ends, thus showing that coil-length wires can be protected from leaky seals by adding at least 1 m of sacrificial wire at each end.