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.
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.
Marginal lands have received wide attention for their potential to improve food security and support bioenergy production. However, environmental issues, ecosystem services, and sustainability have been widely raised over the use of marginal land. Knowledge of the extent, location, and quality of marginal lands as well as their assessment and management are limited and diverse. There are many perceptions about what constitutes marginal lands and so clear definitions are needed. This paper provides a review of the historical development of marginal concept, its application and assessment. Challenges and priority research needs of marginal land assessment and management were also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.