Applications and Devices
•Wire Applications and Superconducting
•Flux Pinning and Issues in High Tc , High Jc
•Electronic Devices Using Josephson
Junctions and SQUIDS
A superconductor displaying the MEISSNER EFFECT
Superconductors have electronic and magnetic properties. That is, they have a
negative susceptibility, and acquire a polarization OPPOSITE to an applied magnetic
field. This is the reason that superconducting materials and magnets repel one
If the temperature increases the sample will lose its superconductivity and the
magnet cannot float on the superconductor.
The track are walls with a continuous series of vertical
coils of wire mounted inside. The wire in these coils is
not a superconductor.
As the train passes each coil, the motion of the
superconducting magnet on the train induces a current
in these coils, making them electromagnets.
The electromagnets on the train and outside produce
forces that levitate the train and keep it centered above
the track. In addition, a wave of electric current sweeps
down these outside coils and propels the train forward.
The Yamanashi MLX01MagLev Train
Superconducting Transmission Cable
From American Superconductor
The cable configuration features a conductor
made from HTS wires wound around a flexible
Liquid nitrogen flows through the core, cooling
the HTS wire to the zero resistance state.
The conductor is surrounded by conventional
dielectric insulation. The efficiency of this
design reduces losses.
The superconducting magnet coils produce a large and
uniform magnetic field inside the patient's body.
MRI (Magnetic Resonance Imaging) scans produce detailed images
of soft tissues.
• Mesoscopic superconducting lead nanowires with high aspect
ratio and diameter ranging from 40 to 270 nm have been
grown by electrodeposition inside nanoporous polycarbonate
membranes. Nanowires with a diameter less than 50 nm were
insulators due to a poor crystal structure. The others are
shown to be type II superconductors because of their small
electronic mean free path, instead of being type I which is
usual for the bulk form of lead. An increase in the
thermodynamic critical field Hc is observed and is attributed
to the small transversal dimension leading to an incomplete
Meissner effect. Finally, it is demonstrated that this
enhancement agrees with numerical simulations based on the
• Single crystalline YBa2Cu3O7−δ nanowires
from a template-directed sol–gel route
• Xu Jian, Liu Xiaohe and Li Yadong, ,
Department of Chemistry, Tsinghua
University, Beijing 100084, PR China
Department of Chemistry, Central South
University, Changsha 410083
• Preparation of anodic aluminum oxide (AAO) template
• Porous AAO membrane was prepared using a two-step anodizing process .
After degreasing in ethanol, high-purity Al foil (99.999%) was electropolished in a
H3PO4–H2SO4–H2O (40:40:20 wt.%) solution for 5 min to reduce the surface
roughness. The resulting Al sheet was washed with ethanol and distilled water,
then mounted on a copper plate to serve as anode for anodization. In the first
step, the anodizing of the Al sheet was carried out under constant voltages of 40 V
in 0.3 M oxalic acid electrolyte for 6 h at 17 °C. Prior to the second anodization,
first disordered porous alumina layer was removed in a mixture of H3PO4 (6 wt.%)
and CrO3 (1.8 wt.%) at 60 °C for 3 h. The second step was following the same
conditions as that of the first, except that the anodizing time was 3 h. A stepwise
voltage reduction technique [28 and 29] was then utilized to thin the barrier layer.
The as-obtained AAO membrane was immersed in 5 wt.% aqueous H3PO4 solution
for pore widening and barrier layer dissolving, followed by washing and drying.
Finally, the through-hole AAO membrane was detached from the Al substrate in a
saturated HgCl2 solution for next use.
• Sol–gel process and fabrication of YBCO nanowires
• YBa2Cu3O7−δ sols used for template synthesis can be obtained as follows. Firstly,
appropriate quantities of ammonia and ethylenediamine tetraacetic acid (EDTA) was added
to copper acetate solutions. Meanwhile the solution of Ba2+ or Y3+ was prepared by
dissolving Ba(OH)2·8H2O or Y2O3 into acetic acid solution, and then both were poured into
the previous solution of Cu2+ to give a mixture with initial molar ratio of Y3+:Ba2+:Cu3+ =
1:2:3. The pH of this mixture solution was adjusted to 6.5 using ammonia and glacial acetic
acid, thus preventing crystallization of copper acetate during gelation. The obtained solution
was hydrolyzed to form a dispersed blue colloidal particles solution (sol) at 70 °C under
• Then a piece of AAO membrane (φ 2 cm) was dipped into this transparent hot sol followed by
ultrasonic treatment 10 min, and kept at ambient temperature overnight (12 h). The sol
containing AAO membrane was gelled to shards by slow evaporation at 90 °C. To form the
superconducting phase, the obtained gel/AAO composite was further heated at 50 °C h−1 to
950 °C and held for 2 h in air at ambient oxygen pressure. Subsequently, the specimen was
cooled at 50 °C h−1 to ambient temperature. Finally, the AAO membrane incorporated with
YBCO nanowires was picked out, and rubbed away YBCO powders covering both faces of the
membrane by polishing alumina.
• Scanning electron microscopy (SEM) confirmed that the
monodisperse cylindrical pores of alumina membrane were
filled with nanowire arrays with a narrow distribution of
diameters. The X-ray diffraction (XRD) pattern of the obtained
nanowires was assessed as orthorhombic YBCO 123 lattice
after heating gels at 950 °C for crystallization. As determined
by transmission electron microscopy (TEM) and electron
diffraction (ED) analysis, the nanowires were essentially single
crystalline in nature. High-resolution transmission electron
microscope (HRTEM) images further revealed the single
crystalline nature of the as-prepared nanowires.
• Representative SEM images of (a) top-view of an empty AAO membrane; (b) cross-sectional view of AAO membrane; (c) top-view of an AAO membrane
filled with YBCO nanowires; (d) cross-sectional view of YBCO nanowires/AAO composite, which revealed the filling of YBCO wires within most of the AAO
pores. The surface of membrane was covered with YBCO powders and could be removed by polishing alumina.