Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session G3: Invited Session: Progress in the New Energy Frontier |
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Sponsoring Units: GERA Chair: George Crabtree, Argonne National Laboratory Room: Ballroom III |
Tuesday, March 19, 2013 11:15AM - 11:51AM |
G3.00001: Nanoscience by the megaton: Scalable technologies for a sustainable future Invited Speaker: Peter Littlewood The US uses on average 3 TW of power, which is the average solar insolation on 10,000 km2 of desert. To harvest the solar spectrum, or its energy converted into wind, wave, and rain, we will have to develop a range of linked energy technologies for efficient generation, storage, transmission, and use. These provide many research targets for new materials and processes, where physics dictates we must control electrons on the nanoscale so as to reach acceptable performance levels, and cost requires manufacturing by the square mile. Perhaps with the exception of metal wires, we have no experience in developing functional materials technologies on the scale needed. With an eye on the pairing of photovoltaics and electrical storage, I will outline some of the challenges and the long-term efforts that will be needed to resolve them. [Preview Abstract] |
Tuesday, March 19, 2013 11:51AM - 12:27PM |
G3.00002: Thermoelectric Phenomena, Materials, Devices, and Applications Invited Speaker: Eric Toberer Thermoelectric materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, could play an important role in a global sustainable energy solution. However, advanced materials with improved conversion efficiency are required for widespread implementation. Improving thermoelectric efficiency requires reconciling competing electronic and thermal transport properties - a material must have both a large carrier effective mass and mobility and low lattice thermal conductivity. Historically, this has been achieved through engineering carrier scattering rates. This talk will focus on new approaches that achieve these conflicting properties through modifications of the electron and phonon band structures. Example materials such as Yb$_{14}$MnSb$_{11}$ and Ba$_{8}$Ga$_{16}$Ge$_{30}$ will be discussed and pathways towards further material improvements will be highlighted. Such tailored control of transport properties will be vital to realize the next generation of energy materials. [Preview Abstract] |
Tuesday, March 19, 2013 12:27PM - 1:03PM |
G3.00003: When is a polymer conjugated? Invited Speaker: John Lupton When considering the nanoscale structure of an electronic material, one typically focuses on the arrangement in space and the interactions between different molecules. The molecule itself is thought of more in terms of a black box. Yet extrapolating from the chemical structure of a macromolecule, such as a conjugated polymer, to its physical function is by no means trivial. How can one be sure that all pi-bonds really are of the type insinuated by quantum chemistry? Time and frequency-domain spectroscopy - most notably pump-probe, upconversion and photon-echo techniques; and the single-molecule approach - have uncovered surprising heterogeneity in intramolecular couplings within nominally homogeneous pi-conjugated systems. The problem with any spectroscopic approach, however, lies in the fact that one and the same experiment is employed to extract both electronic and conformational information, which are intrinsically interrelated. We reverse this conventional approach of adopting the spectroscopy to a particular material and instead focus on a unique set of model systems with predefined physical shape in order to reveal the intricacies of electronic structure. Shape-persistent conjugated macrocycles can be synthesized with molecular weights comparable to those of short polymers, yet with unparalleled physical control over the actual pi-electron system. Such rings reveal, using single-molecule techniques, the effect of dynamic conjugation: spontaneous symmetry breaking of the pi-system due to interactions with the environment. Chromophores, the electronically-active subunits of pi-conjugated macromolecules, are found to form dynamically, leading to rapid jumps in the polarization of light emitted from such symmetric molecules. This insight reveals that nanoscale structure fundamentally begins at the level of individual carbon bonds, which can exhibit pronounced fluctuations. [Preview Abstract] |
Tuesday, March 19, 2013 1:03PM - 1:39PM |
G3.00004: Materials for Electrochemical Energy Storage Invited Speaker: Michelle Johannes Electrochemical energy storage is a primary concern of both the consumer and public energy sectors. Energy, once generated, must be stored, transported and retrieved efficiently. This is commonly done through the use of various kinds of batteries and recently through the use of capacitors. Optimal energy storage involves the complete electrochemical system, but many of the performance properties can be understood in terms of the constituent materials that make up the anode, cathode and electrolyte. In this talk will give a brief overview of electrochemical energy storage systems and the role of materials in improving them. Using computational methods as a framework, I will discuss how discuss how macroscopic properties, such as capacity, conductivity, voltage, and stability are determined by fundamental materials properties at the quantum mechanical level. Using the knowledge gained from understanding the underlying processes, I will discuss some common battery materials, such as LiFePO$_4$, layered transition metal oxides, and oxide electrolyte materials. I will show how predictions for better materials can be made using computational tools to save time and money by circumventing expensive screening in the laboratory. I will also discuss how tailoring the morphology of materials, for example by synthesizing at the nanoscale, can have extreme benefits for battery materials performance. [Preview Abstract] |
Tuesday, March 19, 2013 1:39PM - 2:15PM |
G3.00005: Interfacial Effects in Polymer Membranes for Clean Energy Invited Speaker: Christopher Soles Polymeric membranes are critical components in several emerging clean energy technologies. Examples include proton exchange membranes for hydrogen fuel cells, anion exchange membranes for alkaline fuel cells, flow batteries, and even block copolymer membranes for solid electrolytes/separators in lithium ion and other battery technologies. In all of these examples the function of the membrane is to physically separate two reactive electrodes or reactants, but allow the transport or exchange of specific ions through the membrane between the active electrodes. The flow of the charged ionic species between the electrodes can be used to balance the flow of electrons through an external electrical circuit that connects the electrodes, thereby storing or delivering charge electrochemically. In this presentation I will review the use of polymeric membranes in electrochemical energy storage technologies and discuss the critical issues related to the membranes that hinder these technologies. In particular I will also focus on the role the polymer membrane interface on device performance. At some point the polymer membrane must be interfaced with an active electrode or catalyst and the nature of this interface can significantly impact performance. Simulations of device performance based on bulk membrane transport properties often fail to predict the actual performance and empirical interfacial impedance terms usually added to capture the device performance. In this presentation I will explore the origins of this interfacial impedance in the different types of fuel cell membranes (proton and alkaline) by creating model thin film membranes where all of the membrane can be considered interfacial. We then use these thin films as a surrogate for the interfacial regions of a bulk membrane and then quantify the structure, dynamics, and transport properties of water and ions in the confined interfacial films. Using neutron reflectivity, grazing incidence X-ray diffraction, and positron annihilation lifetime spectrocopy, we demonstrate that there can be substantial differences in the structure of the ion transport domains in these interfacial region. However, in-situ measurements including dynamic swelling with X-ray and neutron reflectivity, dynamic quartz crystal microbalance of mass uptake/loss, and dynamic phase modulated infrared absorption measurements and generally support both a reduced solubility and diffusivity of the ionic species in the interfacial region, consistent with enhanced interfacial impedance. [Preview Abstract] |
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