5,032 research outputs found
Development of the dry tape battery concept Quarterly report no. 4, 9 Mar. - 9 Jun. 1966
Aqueous and nonqueous electrolytic actions, and energy density measurements for dry tape batter
Development of the dry tape battery concept Quarterly report no. 3, 9 Dec. 1965 - 8 Mar. 1966
Material electrical and chemical properties tested for use in dry tape batterie
Strong Pinning Enhancement in MgB2 Using Very Small Dy2O3 Additions
0.5 to 5.0 wt.% Dy2O3 was in-situ reacted with Mg + B to form pinned MgB2.
While Tc remained largely unchanged, Jc was strongly enhanced. The best sample
(only 0.5 wt.% Dy2O3) had a Jc of 6.5 x 10^5 A/cm^2 at 6K, 1T and 3.5 x 10^5
A/cm^2 at 20K, 1T, around a factor of 4 higher compared to the pure sample, and
equivalent to hot-pressed or nano-Si added MgB2 at below 1T. Even distributions
of nano-scale precipitates of DyB4 and MgO were observed within the grains. The
room temperature resistivity decreased with Dy2O3 indicative of improved grain
connectivity.Comment: 13 pages, 4 figures and 1 tabl
Raising Bi-O bands above the Fermi energy level of hole-doped BiSrCaCuO and other cuprate superconductors
The Fermi surface (FS) of BiSrCaCuO
(Bi2212) predicted by band theory displays Bi-related pockets around the
point, which have never been observed experimentally. We show that
when the effects of hole doping either by substituting Pb for Bi or by adding
excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi
energy () and the resulting first-principles FS is in remarkable accord
with measurements. With decreasing hole-doping the Bi-O bands drop below
and the system self-dopes below a critical hole concentration. Computations on
other Bi- as well as Tl- and Hg-based compounds indicate that lifting of the
cation-derived band with hole doping is a general property of the electronic
structures of the cuprates.Comment: 4 pages, 4 figures; PRL (2006, in press
Improved Current Densities in MgB2 By Liquid-Assisted Sintering
Polycrystalline MgB2 samples with GaN additions were prepared by reaction of
Mg, B, and GaN powders. The presence of Ga leads to a low melting eutectic
phase which allowed liquid phase sintering and produces plate-like grains. For
low-level GaN additions (5% at. % or less), the critical transition
temperature, Tc, remained unchanged and in 1T magnetic field, the critical
current density, Jc was enhanced by a factor of 2 and 10, for temperatures of
\~5K and 20K, respectively. The values obtained are approaching those of hot
isostatically pressed samples.Comment: 12 pages, 1 table, 4 figures, accepted in Applied Physics Letter
Thin-Film Trilayer Manganate Junctions
Spin-dependent conductance across a manganate-barrier-manganate junction has
recently been demonstrated. The junction is a LaSrMnO%
-SrTiO-La SrMnO trilayer device supporting
current-perpendicular transport. Large magnetoresistance of up to a factor of
five change was observed in these junctions at 4.2K in a relatively low field
of the order of 100 Oe. Temperature and bias dependent studies revealed a
complex junction interface structure whose materials physics has yet to be
understood.Comment: 20 pages, 14 figures. To appear in Phil. Trans. R. Soc. Lond. A
vol.356 (1998
Quantum Hall conductance of two-terminal graphene devices
Measurement and theory of the two-terminal conductance of monolayer and
bilayer graphene in the quantum Hall regime are compared. We examine features
of conductance as a function of gate voltage that allow monolayer, bilayer, and
gapped samples to be distinguished, including N-shaped distortions of quantum
Hall plateaus and conductance peaks and dips at the charge neutrality point.
Generally good agreement is found between measurement and theory. Possible
origins of discrepancies are discussed
Normal state properties of high angle grain boundaries in (Y,Ca)Ba2Cu3O7-delta
By lithographically fabricating an optimised Wheatstone bridge geometry, we
have been able to make accurate measurements of the resistance of grain
boundaries in Y1-xCaxBa2Cu3O7-d between the superconducting transition
temperature, Tc, and room temperature. Below Tc the normal state properties
were assessed by applying sufficiently high currents. The behaviour of the
grain boundary resistance versus temperature and of the conductance versus
voltage are discussed in the framework charge transport through a tunnel
barrier. The influence of misorientation angle, oxygen content, and calcium
doping on the normal state properties is related to changes of the height and
shape of the grain boundary potential barrier.Comment: 17 pages, 1 table, 5 figures, submitted to PR
Research and development of the dry tape battery concept Quarterly report, 9 Jun. - 9 Sep. 1966
Dry tape battery concept - cathode and anode research, energy densities, tape cell preparation, and supporting researc
- …