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Fri, 24 Feb 2012, 10:36am Mechanism behind capacitor's high-speed energy storage discovered »
sydd
EExpert
Cell
Registered: Aug, 2008
Last visit: Tue, 15 Apr 2014
Posts: 211

I think this is the interesting part of the lurid written article:

From the source web site
http://news.ncsu.edu/releases/ranjanprl/

Abstract:
Using first-principles simulations, we identify the microscopic origin of the non-linear dielectric response and high energy density of PVDF-based polymers as a cooperative transition path that connects non-polar and polar phases of the system. This path explores a complex torsional and rotational manifold and is thermodynamically and kinetically accessible at relatively low temperatures. Furthermore, the introduction of suitable copolymers significantly alters the energy barriers between phases providing tunability of both the energy density and the critical fields.

From Physical Review Letters
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.108.087802

a much better report...

Synopsis: Plastic Capacitors

One of the biggest speed bumps hindering widespread adoption of electric vehicles is energy storage: conventional liquid fuels offer a stored energy per unit weight that is hard to beat. The two current approaches to overcoming this limitation are batteries, which use a chemical reaction to generate electricity, or capacitors, which directly store electricity then discharge it when needed. Capacitors take the lead in applications requiring quick delivery of energy. In essence, capacitors are made from two metal surfaces separated by a dielectric; the capacitance can be improved by bringing the surfaces closer together and by using a separator with high dielectric permittivity.

Computer simulations reported in Physical Review Letters by Vivek Ranjan of North Carolina State University, Raleigh, and colleagues predict that mixing a ferroelectric polymer with a pinch of another polymer could yield a sevenfold increase in stored energy compared to the pure dielectric. The calculations offer insights at the molecular level about how this occurs, showing the polymer atoms collectively rearrange from a nonpolar to polar state. Transition paths uncovered by the work have low activation energies and are accessible at technologically reasonable temperatures. The results point the way toward research into creating such optimized polymer dielectrics, which would make capacitive systems roadworthy for powering electric vehicles. – David Voss

can someone with access please at the following paper:
http://prl.aps.org/abstract/PRL/v108/i8/e087802

Phys. Rev. Lett. 108, 087802 (2012) [5 pages]
Electric Field Induced Phase Transitions in Polymers: A Novel Mechanism for High Speed Energy Storage

cheers sydd


Chat from 5 pm Mon, 9 Jan 2012:
"I WANT MY DAMN LONG DIPOLE, FOR CRIMINEY SAKES ! :)" - nekote
"But there are no farking long or short dipoles to speak of. Just some residual short dipoles relative to the plate" - Prof Bombay

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