Recent Progress in Application of Internal Oxidation Technique in Nb3Sn Strands
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Citation:Published version: IEEE Transactions on Applied Superconductivity (Volume: 27, Issue: 4, June 2017) Article Sequence Number: 6000105. https://doi.org/10.1109/TASC.2016.2625780
The internal oxidation technique can generate ZrO2 nano particles in Nb3Sn strands, which markedly refine the Nb3Sn grain size and boost the high-field critical current density (Jc). This article summarizes recent efforts on implementing this technique in practical Nb3Sn wires and adding Ti as a dopant. It is demonstrated that this technique can be readily incorporated into the present Nb3Sn conductor manufacturing technology. Powder-in-tube (PIT) strands with fine subelements (~25 μm) based on this technique were successfully fabricated, and proper heat treatments for oxygen transfer were explored. Future work for producing strands ready for applications is proposed.
Experiments for adding Ti show that either oxygen or Ti source must be away from the Sn core to avoid formation of TiO2. It is revealed that oxygen transfer can occur via atmosphere between oxide powder and Nb-1%Zr, while contact between them is not required. Fabrication of PIT strands with fine filaments was successful, and proper heat treatments were proposed for oxygen transfer. However, there are still some problems to be solved in order for present PIT strands to be practically applicable.
This work was supported in part by the U.S. Dept. of Energy, Office of High Energy Physics, SBIR phase I grant DE-SC0013849.