105 research outputs found
Moderate temperature rechargeable sodium batteries
Cells utilizing the organic electrolyte, NaI in triglyme, operated at approx. 130 C with Na(+) - intercalating cathodes. However, their rate and stability were inadequate. NaAlCl4 was found to be a highly useful electrolyte for cell operation at 165-190 C. Na(+) intercalating chalcogenides reacted with NaAlCl4 during cycling to form stable phases. Thus, VS2 became essentially VS2Cl, with reversible capacity of approx 2.8 e(-)/V, and a mid-discharge voltage of approx 2.5V and 100 deep discharge cycles were readily achieved. A positive electrode consisting of VCl3 and S plus NaAlCl4 was subjected to deep-discharge cycles 300 times and it demonstrated identity with the in-situ-formed BSxCly cathode. NiS2 and NiS which are not Na(+)-intercalating structures formed highly reversible electrodes in NaAlCl4. The indicated discharge mechanism implies a theoretical capacity 4e(-)/Ni for NiS2 and 2e(-)/Ni for NiS. The mid-discharge potentials are, respectively, 2.4V and 2.1V. A Na/NiS2 cell cycling at a C/5 rate has exceeded 500 deep discharge cycles with 2.5e(-)/Ni average utilization. A 4 A-hr nominal capacity prototype Na/NiS2 cell was tested at 190 C. It was voluntarily terminated after 80 cycles. Further development, particularly of cathode structure and hardware should produce a battery capable of at least 50-W-hr/lb and more than 1000 cycles
The effects of superconductor-stabilizer interfacial resistance on quench of a pancake coil made out of coated conductor
We present the results of numerical analysis of normal zone propagation in a
stack of coated conductors which imitates a pancake coil.
Our main purpose is to determine whether the quench protection quality of such
coils can be substantially improved by increased contact resistance between the
superconducting film and the stabilizer. We show that with increased contact
resistance the speed of normal zone propagation increases, the detection of a
normal zone inside the coil becomes possible earlier, when the peak temperature
inside the normal zone is lower, and stability margins shrink. Thus, increasing
contact resistance may become a viable option for improving the prospects of
coated conductors for high magnets applications.Comment: 9 pages, 4 figure
Phase Evolution of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> films by all-chemical solution deposition route for coated conductors
Self-Assembled Nanoparticle Drumhead Resonators
The self-assembly of nanoscale structures from
functional nanoparticles has provided a powerful path to
developing devices with emergent properties from the bottomup.
Here we demonstrate that freestanding sheets selfassembled
from various nanoparticles form versatile nanomechanical
resonators in the megahertz frequency range.
Using spatially resolved laser-interferometry to measure
thermal vibrational spectra and image vibration modes, we
show that their dynamic behavior is in excellent agreement
with linear elastic response for prestressed drumheads of
negligible bending stiffness. Fabricated in a simple one-step
drying-mediated process, these resonators are highly robust and their inorganic−organic hybrid nature offers an extremely low
mass, low stiffness, and the potential to couple the intrinsic functionality of the nanoparticle building blocks to nanomechanical
motion
Recommended from our members
DEVELOPMENT OF HTS CONDUCTORS FOR ELECTRIC POWER APPLICATIONS
Second generation (2G) technologies to fabricate high-performance superconducting wires developed at the Oak Ridge National Laboratory (ORNL) were transferred to American Superconductor via this CRADA. In addition, co-development of technologies for over a decade was done to enable fabrication of commercial high-temperature superconducting (HTS) wires with high performance. The massive success of this CRADA has allowed American Superconductor Corporation (AMSC) to become a global leader in the fabrication of HTS wire and the technology is fully based on the Rolling Assisted Biaxially Textured Substrates (RABiTS) technology invented and developed at ORNL
- …