This is the first time a superconductor has self-assembled into a porous, three-dimensional gyroidal structure. After years of collaboration with co-author Prof. Sol Gruner, physics, Wiesner developed the idea for the gyroidal structure, employing niobium nitride as the superconducting material brought the idea to fruition.
“The superconductors have this so-called gyroid nanostructure which provides a network of nanopores of around 15 nanometers that percolates the entire superconducting structure,” Wiesner said. “The width of the superconducting struts separating the pores itself is only of order 10 to 20 nanometers.”
Diverging from the typical bulk material used to create superconductors, Wiesner’s team utilized a self-assembling, synthetic block copolymer assembled in Wiesner’s labs.
Wiesner’s achievement also expands possibilities for the future research and creation of superconductors, he said.
“The gyroid structure is only one of many, many spontaneous structures that polymers and other self-assembly systems form,” Wiesner said. “We can now start to test how these structures will change the properties of superconductors.”
Science Advances - Block copolymer self-assembly–directed synthesis of mesoporous gyroidal superconductors
Superconductors with periodically ordered mesoporous structures are expected to have properties very different from those of their bulk counterparts. Systematic studies of such phenomena to date are sparse, however, because of a lack of versatile synthetic approaches to such materials. We demonstrate the formation of three-dimensionally continuous gyroidal mesoporous niobium nitride (NbN) superconductors from chiral ABC triblock terpolymer self-assembly–directed sol-gel–derived niobium oxide with subsequent thermal processing in air and ammonia gas. Superconducting materials exhibit a critical temperature (Tc) of about 7 to 8 K, a flux exclusion of about 5% compared to a dense NbN solid, and an estimated critical current density (Jc) of 440 A cm−2 at 100 Oe and 2.5 K. We expect block copolymer self-assembly–directed mesoporous superconductors to provide interesting subjects for mesostructure-superconductivity correlation studies.
SOURCE - Block copolymer self-assembly–directed synthesis of mesoporous gyroidal superconductors, Spencer W. Robbins, Peter A. Beaucage, Hiroaki Sai1, Kwan Wee Tan1, Jörg G. Werner, James P. Sethna, Francis J. DiSalvo, Sol M. Gruner, Robert B. Van Dover and Ulrich Wiesner, Science Advances 29 Jan 2016: Vol. 2, no. 1, e1501119 DOI: 10.1126/sciadv.1501119