A method to obtain long lengths of flexible, biaxially oriented substrates with smooth, chemically compatible surfaces for epitaxial growth of high-temperature superconductors is reported. The technique uses well established, industrially scalable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers (metal and/or ceramic) to yield chemically compatible surfaces. Epitaxial YBa2Cu3Ox films grown on such substrates have critical current densities exceeding 105 A/cm2 at 77 K in zero field and have field dependencies similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for the fabrication of long lengths of high-Jc wire capable of carrying high currents in high magnetic fields and at elevated temperatures.

In-plane-aligned, c axis-oriented YBa, Cu, O, (YBCO) films with superconducting critical current densities J, as high as 700,000 amperes per square centimeter at 77 kelvin have been grown on thermomechanically rolled-textured nickel (001) tapes by pulsedlaser deposition. Epitaxial growth of oxide buffer layers directly on biaxially textured nickel, formed by recrystallization of cold-rolled pure nickel, made possible the growth of YBCO films 1.5 micrometers thick with superconducting properties that are comparable to those observed for epitaxial films on single-crystal oxide substrates. This result represents a viable approach for the production of long superconducting tapes for high-current, high-field applications at 77 kelvin.Since the discovery of high-temperature superconductivity (HTS) in cuprate materials, substantial efforts have focused on developing a high-current superconducting wire technology for applications at 77 K (1, 2). Early in these efforts it was observed that randomly oriented polycrystalline HTS materials have critical current densities, J,, (500 A/cm2. In contrast, oriented YBCO thin films grown epitaxially on single-crystal oxide substrates, such as SrTiO, (OOl), exhibit J, values >1 MA/cm2 at 77 K (3). This huge difference between randomly oriented HTS ceramics and single crystal-like epitaxial films is directly related to the misorientation angles at the grain boundaries in polycrystalline materials. Values for J, across a grain boundary decrease significantly as the misorientation angle increases, with weak-link behavior observed for misorientation angles at the grain boundaries greater than -10" (4-12). In order to achieve high J, values (-lo5 to lo6 A/cm2, 77 K), the crystallographic orientation of the HTS superconducting wire or tape must have a high degree of both in-plane and out-of-plane grain alignment over the conductor's entire length. Ideally, this would be achieved with YBCO, because the limits for dissipation-free current at 77 K in an applied magnetic field are most favorable for this material (1 3, 14).One approach to producing a high-J, HTS tape is to deposit a thick epitaxial film on a substrate material that has a high degree of in-plane and out-of-plane crystallographic texture and can be produced in long lengths. Epitaxial HTS films on singlecrystal oxides satisfy the requirements for high J,, but it is not feasible to produce long lengths of these substrates. Recent efforts have focused on the use of ion beam-assisted deposition (IBAD) to achieve inplane alignment of oxide buffer layers on polycrystalline metal substrates for subsequent epitaxial growth of . Indeed, a modest degree of in-plane texture for c axis-oriented YBCO films made by IBAD results in a significant increase in J,, with values ranging from lo5 to lo6 A/cm2 at 77 K. However, IBAD techniques have limitations, including the relatively low de~osition rates associated with the IBAD buffer layers as well as difficulties in consistently producing in-plane crystallographic alignment of less than lo0, tha...

This paper studied and realized a flexible nanogenerator based on P(VDF-TrFE) nanofibers and PDMS/MWCNT thin composite membrane, which worked under triboelectric and piezoelectric hybrid mechanisms. The P(VDF-TrFE) nanofibers as a piezoelectric functional layer and a triboelectric friction layer are formed by electrospinning process. In order to improve the performance of triboelectric nanogenerator, the multiwall carbon nanotubes (MWCNT) is doped into PDMS patterned films as the other flexible friction layer to increase the initial capacitance. The flexible nanogenerator is fabricated by low cost MEMS processes. Its output performance is characterized in detail and structural optimization is performed. The device’s output peak-peak voltage, power and power density under triboelectric mechanism are 25 V, 98.56 μW and 1.98 mW/cm3 under the pressure force of 5 N, respectively. The output peak-peak voltage, power and power density under piezoelectric working principle are 2.5 V, 9.74 μW, and 0.689 mW/cm3 under the same condition, respectively. We believe that the proposed flexible, biocompatible, lightweight, low cost nanogenerator will supply effective power energy sustainably for wearable devices in practical applications.

March 2021Ethics oversight 2020(100)).Note that full information on the approval of the study protocol must also be provided in the manuscript.

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