Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session A33: Focus Session: Dielectric and Ferroelectric Polymers for Electrical Applications: Dielectrics |
Hide Abstracts |
Sponsoring Units: DPOLY DMP Chair: Lei Zhu, Case Western Reserve University Room: 341 |
Monday, March 18, 2013 8:00AM - 8:36AM |
A33.00001: Imaging the Effect of Electrical Breakdown in Multilayer Polymer Capacitor Films Invited Speaker: Mason Wolak Multilayer polymer films show great promise as the dielectric material in high energy density capacitors. Such films show enhancement in both dielectric strength ($E_{\mathrm{B}})$ and energy density ($U_{\mathrm{d}})$ relative to monolithic films of either source polymer. Composites are typically comprised of alternating layers of a high $E_{\mathrm{B}}$ polymer and a high permittivity polymer. Here, we discuss a multilayer system based on polycarbonate (PC) interleaved with polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The dielectric properties of the PC/PVDF-HFP films are influenced by both composition and individual layer thickness. Optimized films show $E_{\mathrm{B}}=$750 kV/mm and $U_{\mathrm{d}}=$13 J/cm$^{3}$. Further enhancements in $E_{\mathrm{B}}$ and $U_{\mathrm{d}}$ are expected through optimization of the component polymers, composition, and layer structure. To guide next generation design, it is important to understand the breakdown mechanism, as it directly influences $E_{\mathrm{B}}$. To elucidate the role of the layer structure during electrical breakdown, we use a tandem focused ion beam (FIB) / scanning electron microscope (SEM) imaging technique. The technique allows us to image the internal layer structure of both `as fabricated' control films, and those subjected to high electric fields. It is therefore a powerful tool to assess film quality and analyze failure mechanisms. Specifically, the FIB is used to mill site-specific holes in a film and the resulting cross-sections are imaged via SEM. Individual layers are easily resolved down to 50 nm. For films subjected to electrical breakdown, the location and propagation of damage is tracked with sequential FIB milling and SEM imaging. Spatially resolved FIB/SEM imaging allows preparation of quasi-3D maps displaying the evolution of internal voids in areas adjacent to the breakdown location (pinhole of d $=$ 30-80 microns). A majority of the voids are localized at the interfaces between layers and may propagate as far as 30-50 microns from the pinhole. The data suggest that the enhancement in dielectric strength arises from a barrier effect, whereby the propagation of an electrical breakdown in the direction of the applied field is impeded by the layer interfaces. We will also discuss recent TEM imaging results that are used to characterize the interfacial length scale and chemical makeup, factors that may influence breakdown. [Preview Abstract] |
Monday, March 18, 2013 8:36AM - 9:12AM |
A33.00002: Accelerating Dielectrics Design Using Thinking Machines Invited Speaker: R. Ramprasad High energy density capacitors are required for several pulsed power and energy storage applications, including food preservation, nuclear test simulations, electric propulsion of ships and hybrid electric vehicles. The maximum electrostatic energy that can be stored in a capacitor dielectric is proportional to its dielectric constant and the square of its breakdown field. The current standard material for capacitive energy storage is polypropylene which has a large breakdown field but low dielectric constant. We are involved in a search for new classes of polymers superior to polypropylene using first principles computations combined with statistical and machine learning methods. Essential to this search are schemes to efficiently compute the dielectric constant of polymers and the intrinsic dielectric breakdown field, as well as methods to determine the stable structures of new classes of polymers and strategies to efficiently navigate through the polymer chemical space offered by the periodic table. These methodologies have been combined with statistical learning paradigms in order to make property predictions rapidly, and promising classes of polymeric systems for energy storage applications have been identified. [Preview Abstract] |
Monday, March 18, 2013 9:12AM - 9:24AM |
A33.00003: Dielectric Properties of Poly(carbonate) Containing Oxide Nanoparticles Steve Greenbaum, John Fontanella, John Bendler, Charles Edmondson, Mary Wintersgill, David Boyles, Tsvetanka Filipova, Mark Westgate, Armando Rua, Xavier Bogle Nanocomposite of poly(carbonate) (PC) and nanoscopic BaTiO$_{3}$ have been studied. The complex relative permittivity, $\varepsilon $*$= \varepsilon $'-j$\varepsilon $'', at audio frequencies from 5K to about 500K and the room temperature breakdown strength have been determined. In addition, SEM, DSC and TGA studies have been carried out as well as variable temperature and pressure proton NMR relaxation measurements. $\varepsilon '$ is 11 for PC containing 59 wt{\%} of 50-70 nm diameter BaTiO$_{3}$ and $\varepsilon '$ vs. nanoparticle content for the untreated nanoparticles is larger than would be expected on the basis of a recently proposed modified Hanai equation. In addition, the breakdown strength is low and decreases as nanoparticle content increases. Higher breakdown strength is observed when using surface treated nanoparticles. The gamma relaxation (200K and 1000 Hz) does not change as nanoparticle content increases to 59 wt-{\%}. Also, a low temperature relaxation region (in the vicinity of 20K) is found in the heat-treated nanocomposites, which is associated with the nanoparticles themselves. Next, the breakdown strength increases as BaTiO$_{3}$ nanoparticle size increases from 50 nm to 500 nm. Finally, data for PC containing SrTiO$_{3}$, BaZrO$_{3}$, ZrO$_{2}$, TiO$_{2}$ or SiO$_{2}$ may be presented. [Preview Abstract] |
Monday, March 18, 2013 9:24AM - 9:36AM |
A33.00004: Theoretical considerations in the design of polymer dielectrics Philip Taylor, Gavin Brown, Jiayuan Miao, Elshad Allahyarov An ideal dielectric is one that reversibly stores a large amount of energy when exposed to a modest electric field. We have used theory and molecular dynamics simulation as an aid to the development of polymeric materials with favorable properties for energy storage with low dielectric losses. Because the stored energy in a capacitor resides mostly in the energy of distortion of the molecular bonds within the material, it is necessary to optimize the size of the deformable polar units. We achieve this by modeling some of the copolymers of polyvinylidene fluoride, and identifying the preferred density and nature of the cross-linking that pins certain regions of the polymer chains to prevent their rotation when exposed to fields. We then relate this to the electrostatic interactions within chains and between chains in order to take account of the depolarizing fields. We find the optimal length of chain between pinning points to be a function of the applied field strength, and to vary from about ten monomer units at the highest of fields to over a hundred monomers at very weak fields. [Preview Abstract] |
Monday, March 18, 2013 9:36AM - 9:48AM |
A33.00005: Properties of Poly(carbonate) Containing Oxide Nanoparticles Joseph Lomax, John Bendler, John Fontanella, Charles Edmondson, Mary Wintersgill, Mark Westgate Nanocomposites composed of poly(carbonate) (PC) and oxide nanoparticles have been studied. For BaTiO$_{\mathrm{3}}$ both as-received and surface-treated (3-aminopropyl-trimethoxysilane) nanoparticles were utilized. The complex relative permittivity, $\varepsilon $*$= \varepsilon $'-j$\varepsilon $'', at audio frequencies from 5K to about 500K and the room temperature breakdown strength have been determined. Also, SEM, DSC and TGA studies have been carried out. $\varepsilon '$ is 11 for PC containing 59 wt-{\%} of untreated 50-70 nm diameter BaTiO$_{\mathrm{3}}$ and $\varepsilon '$ vs. nanoparticle content is larger than would be expected on the basis of the modified Hanai equation. Also, the breakdown strength is low and decreases as nanoparticle content increases. However, $\varepsilon '$ is low and the breakdown strength is high for PC containing the surface-treated nanoparticles. The gamma relaxation (200K and 1000 Hz) does not change as nanoparticle content increases to 59 wt-{\%}. Also, a low temperature relaxation region (in the vicinity of 20K) associated with the nanoparticles is found in the nanocomposites. Next, the breakdown strength increases as BaTiO$_{\mathrm{3\thinspace }}$nanoparticle size increases from 50 nm to 500 nm. [Preview Abstract] |
Monday, March 18, 2013 9:48AM - 10:00AM |
A33.00006: Morphology of candidate high dielectric constant polymers Daniel W. Sinkovits, Manish Agarwal, Mayank Misra, Sanat Kumar We perform all-atom molecular dynamics simulations of polymers which have been identified as promising candidates for high dielectric constant capacitor applications by single-chain density functional theory calculations. These include both organic polymers and those with SnF$_2$ substitutions. We determine the large-scale morphology of these polymers using both $NPT$ molecular dynamics simulations and a multistep thermodynamic integration technique. [Preview Abstract] |
Monday, March 18, 2013 10:00AM - 10:12AM |
A33.00007: Aromatic Polythiourea Dielectrics with High Energy Density, High Breakdown Strength, and Low Dielectric Loss Shan Wu, Quinn Burlingame, Minren Lin, Qiming Zhang There is an increasing demand on dielectric materials with high electric energy density and low loss for a broad range of applications in modern electronics and electrical power systems such as hybrid electric vehicles (HEV), medical defibrillators, filters, and switched-mode power supplies. One major challenge in developing dielectric polymers is how to achieve high energy density U$_{\mathrm{e}}$ while maintaining low dielectric loss, even at very high-applied electric fields. Here we show that amorphous polar-polymers with very low impurity concentration can be promising for realizing such a dielectric polymer. Polar-polymer with high dipole moment and weak dipole coupling can provide relatively high dielectric constant for high U$_{\mathrm{e}}$, eliminate polarization and conduction losses due to weak dipolar coupling and strong polar-scattering to charge carriers. Indeed, an aromatic polythiourea thin film can maintain low loss to high fields (\textgreater 1 GV/m) with a high U$_{\mathrm{e}}$ ($\sim$ 24 J/cm$^{\mathrm{3}})$, which is very attractive for energy storage capacitors. [Preview Abstract] |
Monday, March 18, 2013 10:12AM - 10:24AM |
A33.00008: Exploration of the Chemical Space of Group 4 Polymer Dielectrics Chenchen Wang, Ghanshyam Pilania, Rampi Ramprasad The current standards for capacitive energy storage applications are polypropylene (PP) and polyethylene (PE) which have large band gap and high breakdown strength, but a small dielectric constant. The envisaged next generation dielectric should provide high dielectric constant, while still preserving the insulating characteristics of PP and PE. To meet these growing needs, we use high throughput density functional theory (DFT) calculations in combination with machine learning (ML) methods to identify classes of polymers with large dielectric constant and band gap. In our work, we consider various possible local chemical modifications to polyethylene (PE). To be specific, we allow the -CH$_{2}$- unit in the PE backbone segment to be replaced by -SiF$_{2}$-, -SiCl$_{2}$-, -GeF$_{2}$-, -GeCl$_{2}$-, -SnF$_{2}$-, or -SnCl$_{2}$- units in a systematic manner. High throughput methods were used first to accurately determine the dielectric constant and band gap of the chemically modified PE chains for a set of limited compositions and configurations. ML methods were then used to predict the properties of systems spanning a much larger part of the configurational and compositional space. A set of most promising PE modifications (with simultaneously large dielectric constant and band gap) is identified using this strategy. [Preview Abstract] |
Monday, March 18, 2013 10:24AM - 10:36AM |
A33.00009: General methodology for creating improved polymeric dielectrics Mayank Misra, Manish Agarwal, Daniel Sinkovits, Sanat Kumar We use molecular dynamics and density functional theory to show that the addition of a small number of polar -OH groups to an apolar, hydrocarbon polymer increases the dielectric constant by a factor of 2, but without substantially increasing the dielectric loss. While these results, which are in good agreement with experiments, point to a specific route to creating improved capacitors, more generally, these results suggest that improved polymeric based dielectric materials can be designed by incorporating polar groups on the chain, but only those whose relaxations can be substantially slowed due to cooperative effects, e.g., through long-lived hydrogen bonds. [Preview Abstract] |
Monday, March 18, 2013 10:36AM - 10:48AM |
A33.00010: Large, Uni-directional Actuation In Dielectric Elastomers Achieved By Fiber Stiffening Jiangshui Huang, David Clarke, Zhigang Suo Cylindrical actuators are made with dielectric elastomer sheets stiffened with fibers in the hoop direction. When a voltage is applied through the thickness of the sheets, large actuation strains are achievable in the axial direction, with or without pre-straining and mechanical loading. For example, actuation strains of 35.8{\%} for a cylinder with a prestrain of 40{\%}, and 28.6{\%} for a cylinder without pre-strain have been achieved without any optimization. Furthermore, the actuation strain is independent of the aspect ratio of the cylinder, so that both large strains and large displacements are readily actuated by using long cylinders. [Preview Abstract] |
Monday, March 18, 2013 10:48AM - 11:00AM |
A33.00011: Dielectric Performance of Matrix Free, Hairy Nanoparticle Films Christopher Grabowski, Elizabeth Opsitnick, Hilmar Koerner, Michael Durstock, Richard Vaia Addressing the increasing electrical energy storage and power delivery needs of industry has driven development of novel insulating materials. The voltage breakdown characteristics of two-component polymer nanocomposites (PNCs) -- nanoparticles dispersed in a polymer matrix -- have been previously explored. Control of morphology and dispersion is challenging, however, due to aggregation at high inorganic fractions (\textgreater\ 5{\%} v/v). To fully establish the potential of these nanostructure hybrid materials, we examine the dielectric performance of matrix free, hairy nanoparticle films. These single-component PNCs are comprised of silica nanoparticles with a polystyrene corona such that coronas of adjacent nanoparticles interpenetrate and entangle. Grafting the polymer directly to the nanoparticle provides certain benefits, including more uniform/predictable film morphologies and higher achievable nanoparticle loading. Energy storage capabilities will be assessed from dielectric experimental methods, which include measuring the characteristic dielectric film strength and dielectric permittivity for varying volume fractions of silica. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700