Solution Fabrication for Multifilamentary tapes of the Second Generation High-Temperature Superconductor
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Energy loss is generated in 2G-HTS in AC applications. Multifilamentization is proved effective for AC loss reduction. In this dissertation, attempts on developing an etch-free, lower cost and scalable solution fabrication of multifilament of 2G-HTS have been made. Three different approaches are developed with inkjet printing insulator lines, MOD YBCO superconductor filaments, and selective electrodepositing Ag overlayer and Cu stabilizer. Inkjet printing insulator lines of the multifilament tape are studied as the replacement of the more common laser-striation technique of multifilamentizing 2G-HTS. The insulator materials selection, ink preparation, inkjet-printing drop stream and printed line formation control are studied. Buffer tape is divided into 12 filaments by 11 0.17 mm-wide inkjet-printed BTO insulator lines. Selective epitaxial growth of REBCO is achieved on the printed buffer. 17.6 times AC loss reduction is achieved with only 25% reduction of Ic. A 1 m long tape is printed and filamentized successfully. TFA-MOD is used as a substitution of MOCVD, for a bottom-up low-cost YBCO deposition process that utilize the benefit of the printed buffer. Studies on MOD buffer selection, precursor preparation, coating technique, heat treatment condition and their impact on superconducting performance has been done. TFA-MOD YBCO thin film has shown Jc of 0.67 MA/cm2 and Tc of 89.9 K. MOD has been adapted to the inkjet-printed buffer and selective deposition is achieved due to the hydrophobic nature of BTO lines. Selective deposition of Ag overlayer has been achieve on inkjet-printed multifilamentary samples, selective electroplating of Cu stabilizer has been achieved on both inkjet-printed and laser-striated multifilamentary samples. Electroplating condition optimization, electrolyte potential and ion flux distribution simulation, interfacial bonding and superconductivities evaluation have been studied. Electrodeposited Ag and Cu has smooth and dense surfaces, good thickness uniformity and strong interfacial bonding, and has minimal coupling between the superconducting filaments. 3.44 times less AC loss is achieved on a fully-stabilized 12-filament 2G-HTS with the cost of 10% Ic reduction. The electrodeposition process has been scaled up to reel-to-reel fabrication, a 100 m-long bare REBCO tape is electrodeposited with Ag overlayer and a 30 m-long 12-filmant laser-striated 2G-HTS has been electroplated with Cu stabilizer.