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Nonwoven nanowire network fabrics of the material class La1−xSrxMnO3 (LSMO) with x = 0.2 were fabricated employing a sol-gel-process via electrospinning and a subsequent thermal treatment process based on thermal gravity analysis results. Investigations by means of scanning electron microscopy revealed an average diameter of the resulting nanowires of around 230 nm and a length of more than 100 μm. The chemical phases of the samples have been confirmed via X-Ray diffraction. The nanowires are polycrystalline with an average grain size of about 25 nm obtained from transmission electron microscopy. Analyses of the electronic transportation properties and of the magnetoresistive (MR) effects of the nanowire samples were carried out by a four probe measurement inside a bath cryostat in fields up to 10 T. Measurements of magnetization in the temperature range 2 K

Flux pinning force scaling $f=F_{p}/F_{p,\max \limits }$ f = F p / F p , max vs. h = Ha/Hirr was performed on a variety of pure MgB2 samples, including a spark plasma sintered (SPS) one and a series of samples sintered at various reaction temperatures ranging between 775 and 950 ∘C. The SPS sample exhibits a well-developed scaling at all temperatures, and also the sintered samples prepared at 950 ∘C; however, the obtained peak positions of the pinning force scalings are distinctly different: The SPS sample reveals dominating pinning at grain boundaries, whereas the dominating pinning for the other one is point-pinning. All other samples studied reveal an apparent non-scaling of the pinning forces. The obtained pinning parameters are discussed in the framework of the Dew–Hughes’ pinning force scaling approach.

Bi2Sr2CaCu2O8+δ (Bi-2212) nanowires were fabricated employing electrospinning. A subsequent thermal treatment based on thermal gravity analysis is required to obtain the final crystal structure and superconductivity; however, if this preparation temperature is too high, the nanowire structure may completely collapse during the treatment, which is even more pronounced when aligning the nanowires. Therefore, Li acetate was added in various amounts to the starting composition, which enabled to produce the desired Bi-2212 phase already at about 750 °C instead of 840 °C. An X-ray and a TEM analysis proved that the resulting nanowires were single-phase Bi-2212. After the electro-spinning process, the resulting samples form fabric-like networks, and in the heat treatment, the nanowire structure was found to survive. The nanowires exhibited a polycrystalline structure with grain sizes of 20–50 nm, an average wire diameter of ∼100 nm, and a length of up to several micrometers. The resulting nanowire network samples were characterized by magnetic measurements and electric transport measurements in fields up to 9 and 4 T, respecitively.

Flux pinning forces were determined on different network samples of superconducting Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) nanowires prepared by the electrospinning technique. We employed magnetization data determined by SQUID magnetometry in a wide temperature range 10 K T 35 K, where a strong superconducting signal prevails. The scaling analysis of the pinning forces was applied to interprete the data obtained. Both pure and Li-doped Bi2212 nanowire networks exhibit a peak position of h 0 ∼ 0.11, which is smaller than the expected value of h 0 = 0.2 indicating flux pinning at grain boundaries or extended defects. For the flowing currents through such a network, the crystallographic anisotropy and the percolation play an important role, resulting in reduced peak positions as compared to bulk samples.

Networks of superconducting ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$ (Bi-2212) nanowires were fabricated by the electrospinning technique. The nanowires have a diameter of the order of 150--200 nm and lengths up to the micrometer range and form a nonwoven, fabric-like network with numerous interconnections enabling a current flow between the nanowires. The porosity of this nanowire network is 0.9928. Therefore, this material represents a novel class of ultraporous high-temperature superconductors. The magnetizations of the nanowire networks $[M(T)$ and $M(H)]$ were recorded by SQUID magnetometry. The magnetic properties were analyzed using the extended critical state model (ECSM). It is supposed that the averaged diameter of the nanowires rules the magnetic field dependence of the critical current density of the nanowire network. Single nanowires have remarkably high values of the critical current density of $1.04\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.28em}{0ex}}\mathrm{A}/{\mathrm{cm}}^{2}$ at 5 K. The macroscopic critical current density less than $\ensuremath{\sim}0.05\phantom{\rule{0.28em}{0ex}}\mathrm{A}/{\mathrm{cm}}^{2}$ at 5 K is fine for this lightweight material. Using ECSM, several important magnetic parameters could be determined including the penetration field ${H}_{p}$, the irreversibility fields ${H}_{\mathrm{irr}}$, the upper critical field ${H}_{c2}$, and the flux pinning forces. Applications for this material class may be found in the direction of sensors, thin shielding layers, or nanoporous bulks.