第二代高温超导带材焊接及力学性能研究

第二代高温超导已进入产业化初期, 尽管单根带材长度已达千米量级, 但由于千米级单根带材生产成品率偏低以及大型超导装置对带材长度实际需求远超出单根长度制备能力, 因此, 焊接技术成为高温超导大规模应用的关键技术之一. 接头电阻及其力学性能是评估焊接接头的重要技术指标. 本文提出了改进型接头和“隐形”接头两种制作方法, 并对其接头电阻以及力学性能进行了表征, 同时与常规搭接接头进行了对比分析. 结果发现,(1) 与常规搭接头相比, 改进型和“隐形”接头的厚度分别降低了15 % 和36 % , 有效减小了焊接头处和原带材厚度差异. (2) 超导面-超导面焊接, 获得接头电阻最小; 接头电阻随接头长度的增加而减小, 但幅度降低. (3) 常规搭接头、 改进型和“隐形”焊接头均具有良好的轴向抗拉性能, 通过扭转和8 天液氮浸泡后, 临界电流无衰退, 电阻保持一致. (4) 改进型和“隐形”接头的临界弯曲直径(20 mm) 与原带材(非接头处) 相当, 通过卷对卷传输法测试时接头无损伤, 而常规搭接头的临界弯曲直径(40 mm) 大于原带材, 在通过卷对卷测试时, 接头出现开裂甚至断开现象.根据具体应用场景, 选择合适接头制作方式, 对推动第二代高温超导产业化具有重要意义.     

A convenient synthesis of substituted 3‐alkoxycarbonyl‐β,γ‐unsaturated esters with predominant Z‐selectivity

The consecutive reaction of bis[2,2,2‐trifluoroethyl]phosphite with sodium hydride, dimethyl maleate, and aldehydes gives 3‐alkoxycarbonyl‐β,γ‐unsaturated esters with predominant Z‐selectivity in 62–94% yields (Z/E = 85–60:15–40). The Z‐ and E‐isomer can be separated conveniently by column chromatography. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:276–279, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10142     

Ultra-small PtNi bimetallic encapsulated in silicalite-1 zeolite with fine-tuned surface acidity for selective conversion of levulinic acid

Exploration of levulinic acid (LA) hydrogenation to γ-valerolactone (GVL) contributes to the conversion from carbohydrates to valuable fuels and chemicals. Here, we obtained a series of ultra-small PtNix bimetallic composite catalysts encapsulated in silicalite-1 zeolite (S-1) via a one-pot synthesis strategy protected by tetra(p-carboxyphenyl)porphyrin (TCPP) ligands. The catalytic results showed that PtNi₃@S-1 (TCPP) exhibited the most active catalytic performance (95.7% LA conversion and 93.8% GVL selectivity) under optimized conditions. The characterization results indicate that ligand modification and bimetallic synergy play an important role in enhancing the catalytic activity. The introduction of TCPP provides a guarantee for the homogeneous encapsulation of PtNi₃ in S-1 zeolite at sub-nanometer size. The electronic interaction of PtNi bimetallic, high dispersibility of active components, improved surface acidity and excellent stability co-contribute to the satisfactory hydrogenation activity.