Electrospinning Synthesis of Bi-2223 Superconducting Nanowires

This paper presents the synthesis and characterization of Bi2Sr2Ca2Cu3O8+x superconducting nanowires. Bi2Sr2Ca2Cu3O8+x nanowires with Tc = 68 K were synthesized using the electrospinning process employing sol–gel precursors. A sol–gel methodology was used to obtain a homogeneous PVP solution containing Bi, Sr, Ca, and Cu oxalates. Samples were heat-treated at 120 °C to remove excess moisture, and then at 850 °C in box furnace. Bulk sample was also prepared using coprecipitation method for comparison. Based on XRD, the nanowire sample showed minimal Bi-2223 phases and apparent Bi-2212 phases. The morphology, microstructure, and crystal structure of these nanowires were examined using field emission scanning electron microscopy (FESEM) to reveal a rectangular morphology having typical wire thickness in the range of 150–1000 nm. Electrospun Bi-2223 were grinded and pressed at 0.9 GPa into pellets. DC measurements were conducted to investigate the critical transition temperature (Tc) of Bi-2223 nanowires and to compare their magnetic properties to those of coprecipitated Bi-2223 pellets. The Tc for the bulk sample is observed at 101 K and electrospun Bi-2223 at 68 K. Coprecipitated Bi-2223 was added with Pb whereas electrospun Bi-2223 does not employ Pb. These results point to the existence of utilizing of the substitution of Pb with Bi; Bi-2223 phases in pressed nanowire are less, and the potential of using electrospinning to synthesis functional Bi-2233 superconductors.

Infrared behavior of aluminum nanostructure sculptured thin films

ABSTRACTWe report on fabrication, structural and infrared optical characterization of nanostructure aluminum sculptured thin films prepared by glancing angle deposition (GLAD) and controlled substrate motion on p-type silicon. We discuss two structures, one with plate-like and one with screw-like (chiral) morphology. While the plate-like sample possesses a metal Drude behavior in the infrared spectral range, the chiral nanowire sample behaves non-metallic and reveals a series of intriguing resonances, which are equally spaced in frequency by ∼7.5 THz. We suggest that formation of 3D nano resonator circuits consisting of inductances and capacitances has occurred within the screw-like conductive aluminum wire sample, which might be responsible for the observed resonances. We suggest conductive GLAD nanostructures in combination with Schottky diodes to facilitate active or passive THz detector and transmitter devices.