Artificial Pinning Center Niobium Titatium Superconductors with Optimal Overall Compositions

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This Small Business Innovation Research Phase I project develops NbTi superconductors with artificial pinning centers with an optimal composition in terms of performance and cost. Supercon has developed a patented and proven process for the manufacture of NbTi superconductors using an artificial pinning center approach (APC), which assembles alternate layers of Nb and Ti metals to form a superconducting filament through partial diffusion of the pure metals. It allows one to have independent control of the filament effective composition as well as both the non-superconducting phase (pinning center) thickness and spacing. Conventional NbTi composite manufacturing uses- Nb-47 wt. % Ti for most applications. In principle, the Supercon APC approach can fabricate composites with filaments of almost any effective overall composition. The proximity effect is thought to limit practical NbTi alloy compositions with industrially useful Tc and Hc2 to within the range of 40 to 65 wt. % Ti. Most APC conductors reported in the literature have an overall composition on the Nb rich side of this range. As a result, the Hc2 is reduced, and the cost of the raw materials is increased over a conventional alloy. This proposed work builds upon existing APC manufacture experience at Supercon to optimize new composites with different filament compositions suitable for specific applied magnetic filed ranges, while minimizing the Nb content and therefore cost in each case. The technical objective of the Phase I effort is to understand how independently varying both the composition (relative Nb and Ti layer thickness) and the second phase volume fraction (thermal processing conditions) effect the microstructural, mechanical, and electrical properties (Jc and Hc2) of APC NbTi superconducting composites.