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采用共沉淀工艺制备Bi-2212前驱体粉末,并结合粉末装管法得到19×(36+1)的Bi-22212多芯线材。在部分熔化热处理过程中分别对最高热处理温度Tmax和冷却速率Rc1进行了优化。使用扫描电子显微镜对线材中第二相的分布和芯丝状态进行观察。同时,通过对线材进行差热和热重等热分析方法,对线材在热处理过程中的气孔和第二相的形成过程进行定量分析。结果发现,最高热处理温度和冷却速率对芯丝中包括Bi-2201和AEC等在内的第二相种类和含量,及气孔密度都有较大影响。最终获得最优化的热处理工艺为Tmax=892℃,并且冷却过程采用Rc1=40℃/h的两步降温法,在77 K自场条件下得到了4400 A·cm-2的临界电流密度,本研究为进一步提高Bi-2212线材熔化热处理过程优化提供了理论依据。
The coprecipitation process was used to prepare Bi-2212 precursor powder, and 19 × (36 + 1) Bi-22212 multi-core wire was obtained by powder tube method. During the partial melting heat treatment, the maximum heat treatment temperature Tmax and the cooling rate Rc1 were respectively optimized. The distribution of the second phase in the wire and the state of the core wire were observed using a scanning electron microscope. At the same time, by means of differential thermal analysis and thermal gravimetric analysis, the stomatal and the formation of the second phase during the heat treatment were quantitatively analyzed. The results showed that the highest heat treatment temperature and cooling rate had a great effect on the type and content of the second phase including Bi-2201 and AEC, and the stomatal density. The final optimal heat treatment process is Tmax = 892 ℃, and the cooling process using Rc1 = 40 ℃ / h two-step cooling method, the critical current density of 4400 A · cm-2 obtained at 77 K from the field conditions, the The research provides a theoretical basis for further improving the melting heat treatment process of Bi-2212 wire.