第二代(2G)高溫超導線材在液氮冷卻條件下，於高磁場中具備高電流密度特性(Jc~105A/mm2 at 77K, 3T)，能應用於超導MRI、超導馬達、超導磁浮列車…等，但受超導線材長度之限制，至今仍無法大規模商業化應用。為此本研究嘗試於開發能快速接合且低接合電阻之接合方法。本研究分為三階段逐步推進，於第一階段中實驗多種接合方法(如直接機械接合方法、銦片加壓接合方法、奈米銀漿料管型爐加熱法等)，並比較各接合方法之優劣；於第二階段中改良奈米銀漿料管型爐加熱製程，改以大電流通過奈米銀漿料接合區域，藉由接合區域內的電阻熱作為熱源快速完成線材之接合，提高接合樣品的製作效率；而第三階段中在奈米銀漿料中混入適當比例的超導粉末，並結合外接機械模具和電流加熱製程於蝕刻後之超導線材上，預期可透過機械壓力、電流加熱燒結使超導粉末與超導磊晶層(Sc-Y123-Sc)間緊密連接實現超導接合。
於第一階段實驗中，由各接合實驗成果可知接合介面的不平整是導致高接合比電阻產生的原因，而蝕刻後線材受超導磊晶層的介面上凸起物影響，造成超導直接機械接合(Sc-Sc)的接合比電阻高達580 μΩ•cm2。而於銦片加壓接合實驗(Sc-In-Sc)可知加入適當接合材料能夠有效降低接合比電阻達兩數量級。而續於管型爐實驗部分，以銀漿料取代銦片改善接合強度，並進行一系列奈米銀漿料管型爐加熱實驗(Cu-Ag-Cu)，得到最佳熱處理溫度區間為200~215℃區段，其接合比電阻(200 nΩ•cm2)與同類型文獻(48 nΩ•cm2)僅差距4倍。
於第二階段實驗中，以電流加熱取代管型爐加熱製程，透過調控適當製程參數優化(銅條輔助減少氧化、提高接合壓力、預先乾燥處理…等)，能夠於15分鐘內快速完成接合，其接合成果(接合比電阻約為470 nΩ•cm2)能與管型爐加熱樣品達同一數量級而加熱前後樣品的臨界電流值僅下降<2%。另外於此階段對樣品進行不同方向、大小之外加磁場量測，量測結果顯示無論何種製程之銀漿料接合樣品與純線材趨勢相同(隨著外加磁場增加而減少，下降幅度隨磁場值提高而趨緩)，說明接合前後不影響線材本身的超導性質，此外嘗試透過擄磁實驗分析線材之接合情形，初步可觀察到擄磁之強度變化與線材超導性質相關。
於第三階段實驗中，以混入超導粉末之銀漿料於蝕刻後線材上進行接合(Sc-Ag(50 wt% Y123)-Sc)搭配前述優化過之電流加熱參數進行接合，目前最佳接合比電阻為96 μΩ•cm2，與超導直接機械接合相比約下降半個數量級，於未來仍有提升的空間。

The main limitation preventing superconducting coils from being used on a large scale is the insufficient length of 2G superconducting tapes; therefore, it is necessary to develop suitable jointing techniques to lengthen the tapes. In this study, various solder joints (including solder-free, indium sheet and nano-silver paste) were made and compared with each other. Among them, the nano-silver paste joint has the smallest specific resistance (~0.2 μΩ•cm2) and a higher joining strength. However, the nano-silver paste joint needs to be heated in a tube furnace for 1.5 hours for sintering. In order to reduce the process time, we developed a Joule heating process heated by electric current to sinter nano-silver paste at the junction. The specific resistance value of the Joule-heated sample is about 0.47μΩ•cm2, which is the same order of magnitude as the tube furnace heating sample. Notably, the Ic percentage of the Joule heating sample is about 98% better than the tube furnace heating sample (85%), and the process time is only 15 minutes. Finally, we measured the 2G tape, the tube furnace heating sample, and the Joule heating sample under a magnetic field. The same downward trend was observed in all the samples, indicating that the furnace heating and Joule heating process will not affect the Ic of the 2G HTS tape under a magnetic field.

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