Abstract:  Alumina fiber products with 72%γAl₂O₃+28%SiO₂ were selected as insulating fiber materials of Bi-2212 superconducting magnet, and air heat treatment was carried out for carbon removal. The thermal weight loss, fiber surface morphology, and fiber strength of the three kinds of fiber materials, i.e. alumina fiber ribbon A with 25mm width and 0.2mm thickness, alumina fiber ribbon B with 25mm width and 0.35mm thickness and alumina fiber bundle C with 200tex, 3 strands and 80 twist, were analyzed and characterized by means of strength tests, SEM and TG-DSC. The results show that they have good temperature resistance, and no heat absorption or exothermic peak of crystal phase transformation is found during the thermogravimetric process. After air heat treatment, the surface sizing agent is oxidized and volatilized, the fiber is exposed without defects, the diameter change is not obvious, the strength drop is not more than 25%, and the insulation performance is improved. The analysis results show that the insulation performance of alumina fiber can be effectively improved by air heat treatment at 600℃ lasting 2 hours.

Key words: Bi-2212 superconducting magnet insulation, Alumina fiber, Air heat treatment, Carbon removal 

摘要： 选择成分均为 72%γAl₂O₃+28%SiO₂ 的氧化铝纤维制品作为 Bi-2212 超导磁体绝缘纤维材料并进行空气热处理除碳。采用强度测试、SEM、TG-DSC 等测试手段，对三种氧化铝纤维制品(宽 25mm/厚 0.2mm 氧化铝纤维带 A、宽 25mm/厚 0.35mm 氧化铝纤维带 B 和 200tex/3 股/捻度 80 氧化铝纤维束 C)的热失重、纤维表面形貌、纤维强度进行分析表征。结果表明，其耐温性好，热失重过程并未发现晶相转变的吸放热峰。纤维经过空气热处理后，表面浸润剂氧化挥发，纤维裸露，无缺陷暴露，直径变化不明显，强度下降不超过 25%，绝缘性能提高。分析结果表明，通过 600℃、2h 空气热处理可以有效提高氧化铝纤维绝缘性能。

关键词: Bi-2212 超导磁体绝缘, 氧化铝纤维, 空气热处理, 除碳