EFFECT OF THERMAL TREATMENTS ON THE SUPERCONDUCTIVITY OF UNDOPED AND WO3 DOPED Y-Ba-Cu-O SYSTEM

Undoped and WO₃-doped Y-Ba-Cu-O ceramics have been slowly cooled in flowing oxygen or quenched in air from 900℃ to room temperature, after sintering at 900℃ for 3Oh in flowing oxygen. The ac susceptibility measurements show that the T_c of the quenched WO₃-doped Y-Ba-Gu-O superconductor can reach 88K, while the undoped Y-Ba-Cu-O ceramic quenched in air is a non-superconductor. X-ray diffraction data show that WO₃ does not enter into the YBa₂Cu₃O_7-x lattice but forms all impurity phase. The WO₃-doped YBCO specimens quenched in air consist of orthorhombic YBa₂Cu₃O_7-x phase and an impurity phase which increases with increasing WO₃ content. Raman spectra chow that oxygen contents are different for undoped and WO₃-doped samples. It la suggested that suitable doping with WO₃ can change the oxygen content and reduce the effect of thermal treatments on the superconductivity of Y-Ba-Cu-O system.     

铌钛超导体的非合金化制备

本文研究了Nb片和Ti片在不同温度下的扩散行为,并利用Nb片和Ti片交替组配加工,经过扩散反应制备出了NbTi超导线.运用扫描电镜(SEM)观察了Nb/Ti界面的扩散形态及微结构,并对热处理工艺的合理选择进行了讨论.结果表明:经800℃,5小时扩散可得到厚度最大,Ti含量最高的NbTi超导相.该工艺制备出的NbTi超导线材的临界电流密度Jc可达到2800A/mm2(5T、4.2K)和4200A/mm2(3T、4.2K),与传统工艺制备出的超导体的性能相当.     

Nb/Ti的扩散行为研究

为了简化NbTi超导线材的制备工艺,本文利用叠压的Nb/Ti复合片对600～900℃处理3～9小时的扩散样品进行了研究.扫描电镜观察和分析结果表明,800℃扩散5小时可以得到厚度较大,Ti含量较高的单β相扩散层;过高的扩散温度或过长的扩散时间仅会增加αβ双相区的厚度,反而会降低NbTi材料的性能.     

“三测量点”确定NbTi/Cu复合超导线材分流温度

分流温度(Tcs)是指超导磁体在特定的工作磁场与电流下,当温度升高,超导体中的电流开始流向基体材料时的温度.本文测量了在不同磁场,不同温度时多个测量条件下ITER用NbTi/Cu复合超导线材样品临界电流密度的值,Jc=F(B,T);根据线材不同的使用条件,总结出"三测量点"确定NbTi/Cu线材分流温度的简便方法,对比导体短样分流温度的测量结果,进一步验证了"三测量点"测量线材分流温度并预测导体分流温度的可行性.它为线材制造商及时了解工艺改进效果提供了有力依据.     

铌钛超导体的非合金化制备

本文研究了Nb片和Ti片在不同温度下的扩散行为，并利用Nb片和Ti片交替组配加工，经过扩散反应制备出了NbTi超导线．运用扫描电镜（SEM）观察了Nb／Ti界面的扩散形态及微结构，并对热处理工艺的合理选择进行了讨论．结果表明：经800℃，5小时扩散可得到厚度最大，Ti含量最高的NbTi超导相．该工艺制备出的NbTi超导线材的临界电流密度Jc可达到2800A／mm^2（5T、4．2K）和4200A／mm^2（3T、4．2K），与传统工艺制备出的超导体的性能相当．     

多芯NbTi/Cu复合棒的制造工艺改进和完善

本文是对传统制造工艺改进和完善,制造多芯NbTi/Cu复合棒研究实验.通过自设计制作一套组装工装成功两次组装8000芯NbTi/Cu复合大包套(φ220 mm×560 mm);利用非真空焊封工艺成功焊封多芯大包套;在挤压拉伸过程中增加了热等静压和扒皮工艺,提高了铜材洁净度及复合包套的填充系数;分析挤压过程中芯棒的变形行为规律:当包套填充系数＞93%时,挤压芯棒排列紧密,均匀变形;填充系数＜93%时,挤压芯棒出现不规则变形.     

EFFECT OF THERMAL TREATMENTS ON THE SUPERCONDUCTIVITY OF UNDOPED AND WO3 DOPED Y-Ba-Cu-O SYSTEM

Undoped and WO₃-doped Y-Ba-Cu-O ceramics have been slowly cooled in flowing oxygen or quenched in air from 900℃ to room temperature, after sintering at 900℃ for 3Oh in flowing oxygen. The ac susceptibility measurements show that the T_c of the quenched WO₃-doped Y-Ba-Gu-O superconductor can reach 88K, while the undoped Y-Ba-Cu-O ceramic quenched in air is a non-superconductor. X-ray diffraction data show that WO₃ does not enter into the YBa₂Cu₃O_7-x lattice but forms all impurity phase. The WO₃-doped YBCO specimens quenched in air consist of orthorhombic YBa₂Cu₃O_7-x phase and an impurity phase which increases with increasing WO₃ content. Raman spectra chow that oxygen contents are different for undoped and WO₃-doped samples. It la suggested that suitable doping with WO₃ can change the oxygen content and reduce the effect of thermal treatments on the superconductivity of Y-Ba-Cu-O system.