The development of biaxially textured, second-generation, high-temperature
superconducting (HTS) wires is expected to enable most large-scale applications
of HTS materials, in particular electric-power applications. For many potential
applications, high critical currents in applied magnetic fields are required. It is
well known that columnar defects generated by irradiating high-temperature
superconducting materials with heavy ions significantly enhance the in-field critical
current density. Hence, for over a decade scientists world-wide have sought means
to produce such columnar defects in HTS materials without the expense and
complexity of ionizing radiation. Using a simple and practically scalable technique,
we have succeeded in producing long, nearly continuous vortex pins along the
c-axis
in YBa2Cu3O7−δ
(YBCO), in the form of self-assembled stacks of
BaZrO3
(BZO) nanodots and nanorods. The nanodots and nanorods have a diameter of
∼2–3 nm and an areal density (‘matching field’) of 8–10 T for 2 vol.% incorporation of
BaZrO3. In addition, four misfit dislocations around each nanodot or nanorod are
aligned and act as extended columnar defects. YBCO films with such defects
exhibit significantly enhanced pinning with less sensitivity to magnetic fields
H. In particular, at intermediate field values, the current density,
Jc, varies
as Jc∼H−α,
with α∼0.3
rather than the usual values 0.5–0.65. Similar results were also obtained for
CaZrO3
(CZO) and YSZ incorporation in the form of nanodots and nanorods within YBCO,
indicating the broad applicability of the developed process. The process could also be used
to incorporate self-assembled nanodots and nanorods within matrices of other materials for
different applications, such as magnetic materials.
Mesoporous TiO2–B microspheres with a favorable material architecture are designed and synthesized for highpower lithium ion batteries. This material, which combines the advantages of fast lithium transport with a pseudocapacitive mechanism, adequate electrode‐electrolyte contact, and compact particle packing in the electrode layer, shows superior high‐rate charge–discharge capability and long‐time cyclability for lithium ion batteries.
We demonstrated short segments of a superconducting wire that meets or exceeds performance requirements for many large-scale applications of high-temperature superconducting materials, especially those requiring a high supercurrent and/or a high engineering critical current density in applied magnetic fields. The performance requirements for these varied applications were met in 3-micrometer-thick YBa2Cu3O(7-delta) films epitaxially grown via pulsed laser ablation on rolling assisted biaxially textured substrates. Enhancements of the critical current in self-field as well as excellent retention of this current in high applied magnetic fields were achieved in the thick films via incorporation of a periodic array of extended columnar defects, composed of self-aligned nanodots of nonsuperconducting material extending through the entire thickness of the film. These columnar defects are highly effective in pinning the superconducting vortices or flux lines, thereby resulting in the substantially enhanced performance of this wire.
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.
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