Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session U01: Miscellaneous Energy-related Materials, Concepts and Phenomena |
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Sponsoring Units: GERA Chair: Wade Braunecker, National Renewable Energy Laboratory Room: 103 |
Thursday, March 5, 2020 2:30PM - 2:42PM |
U01.00001: Improved light outcoupling by spontaneously formed nanostructured micro-islands in perovskite films Jitendra Kumar, Ramesh Kumar, Kyle Frohna, Dhanashree Moghe, Dinesh Kabra, Sam Stranks, Monojit Bag Halide perovskites have been the hot topic of research for their unprecedented optoelectronic properties such as high photoluminescence quantum yield (PLQY)1 and ambipolar charge transport. These properties are generally measured at the macroscopic level, but they differ significantly at micro to nano-scale. Here, we have fabricated CH3NH3PbBr3 films containing nanostructured micro-islands (MIs). We have observed that the presence of MIs shows 7 fold increased photoluminescence (PL). This enhancement is due to nanostructured morphology that can also improve the outcoupling. As seen from the fluorescence microscope, PL is mostly coming from MIs. These films were characterized by hyperspectral microscopy. The PL spectrum shows ~10 nm blue shift as compared to that of untreated films. The blue shift is attributed to the increased octahedral tilting, because the MIs consists of 20-40nm sized crystals, whereas the background has ~300 nm feature size. PL spectrum can be fitted with two Gaussian functions centered at 533 nm and 540 nm respectively, which shows the inefficient funneling of excitons. However, we have seen that the MIs show photodegradation whereas background and untreated films show photoactivation. |
Thursday, March 5, 2020 2:42PM - 2:54PM |
U01.00002: Optimized fabrication of nanoporous membranes for osmotic power generation Khadija Yazda, Yuning Zhang, Peter H Grutter, Walter W Reisner Osmotic energy, the energy extracted by mixing two solutions with different salinities, has been receiving significant attention in the scientific community as a potential source of clean and renewable energy (so called “Blue Energy”). A major impediment to exploiting osmotic energy is the poor efficiency of commercially available membranes for osmotic energy conversion. Nanoscale membranes with pores at or below 10 nm in diameter may provide sufficient power generation to make osmotic energy viable. Yet, currently no technology exists that can produce such membranes with sufficient control and scale. Here, leveraging our breakthrough tip-controlled local breakdown (TCLB) pore fabrication approach, we demonstrate high osmotic power density comparable to the density obtained with atomically thin 2D materials, yet with a scalable hybrid hBN/SiN membrane. In particular, the TCLB technique can produce pore arrays with a controlled spacing that yields optimum performance. Our work shows that the optimum membrane selectivity and overall power density is obtained with a pore spacing that balances the need for high pore density while maintaining a large extent of charged surface surrounding each pore. |
Thursday, March 5, 2020 2:54PM - 3:06PM |
U01.00003: Toward understanding of a mechanism for electrical current generation from ionic water flow using metal nanofilms Jeongmin Kim, Davis D. Boamah, Emilie H. Lozier, Catherine E. Walker, Franz M. Geiger, Thomas Miller “Hydrovoltaic” technologies convert energy from flowing water to electricity via a mechanism that primarily relies on ion adsorption and desorption at water-solid interfaces. Recently, we found metal/metal-oxide nanofilms that generate electrical current from aqueous flow of alternating salinity gradients. Atom probe tomography revealed the 10 nm thick nanofilms are composed of a thermal oxide overlayer about 2-4 nm thick and a lower layer of metal about 6-8 nm thick. Experiments suggested the following design rules for the nanofilms: (i) the metal oxide needs to be redox-active, containing several metal-oxidation states, and (ii) there is an optimal thickness for the nanofilms, comparable to electron mean-free path. For example, 10 nm thick Fe:FeOx films with an alternating flow of sea water and de-ionized water produce current-densities of several microA cm-2 at the flow rate of a few cm s-1, where iron oxide (FeOx) has iron in both the Fe2+ and Fe3+ oxidation states. In this poster, we present simulation and theoretical approaches to understand and design the connections between microscopic variables and device-level observables. |
Thursday, March 5, 2020 3:06PM - 3:18PM |
U01.00004: A theoretical upper bound on gas deliverable capacity via pressure-swing adsorption in nanoporous materials Jordan Pommerenck, Cory M Simon, David J Roundy Due to their low volumetric energy density at ambient conditions, both hydrogen and natural gas are challenging to commercially store onboard environmentally sustainable vehicles. One strategy to densify these gases is to pack the fuel tank with a porous material. Metal-organic frameworks are tunable, nanoporous materials with large internal surface areas and show considerable promise for densifying gases. The US Department of Energy (DOE) has set volumetric deliverable capacity targets which, if met, would help to enable commercial adoption of hydrogen/natural gas as transportation fuels. Here, we present a theoretical upper bound on the deliverable capacity via an isothermal pressure-swing storage. The goals set by DOE for natural gas and hydrogen storage are theoretically possible, but sufficiently close to the upper bound as to be impractical for any real porous material. However, this upper bound directly leads to important realizations which should guide future development. Firstly, one could extract the gas at a higher temperature than that used while filling. Secondly, the fundamental physics of our upper bound do not rule out any material that changes its structure due to the presence of gas, suggesting that flexible materials could still satisfy the DOE target. |
Thursday, March 5, 2020 3:18PM - 3:30PM |
U01.00005: Effective electrical conductivity of nanocarbon-metal composites made by the electrocharging assisted process Christopher Klingshirn, Andrew Palughi, Xiaoxiao Ge, Madeline Morales, Jessica Ye, Christopher Shumeyko, Tahir Çağin, Lourdes Salamanca-Riba Robust materials with high conductivity are essential to electronic devices and systems. Novel composites called “covetics” have the potential to improve upon the electrical conductivity of established metals and alloys, including Al and Cu, by incorporating carbon nanostructures known for their superior electrical properties. During fabrication, electric current applied to the melt containing a C precursor is believed to ionize carbon atoms and cause nanoscale graphitic ribbons and chains to form within the metal lattice. This work combines fundamental assumptions about the nature of covetics, specifically a tightly bound metal-carbon interface, with a simple effective-medium model to estimate the bulk conductivity of ideal Al and Cu covetics with randomly distributed graphene nanoribbons. Density-functional theory estimates of charge transfer at the graphene-metal interface, local electrical conductivity measurements, and transmission electron microscopy investigation of the interface region provide inputs to the model. We find potential for improvements on the order of 10% under ideal conditions, but substantial processing challenges remain before these gains may be realized on an industrial scale. |
Thursday, March 5, 2020 3:30PM - 3:42PM |
U01.00006: Optimizing the role of impact ionization in conventional insulators Efstratios Manousakis A mechanism for multiple carrier generation through impact ionization (IA) proposed earlier for bulk systems of strongly correlated insulators is generalized to the case of conventional insulators that contain localized bands a few eV above and below the highest occupied band. Specifically, we study the case of hybridization of localized orbitals with more dispersive bands near the Fermi level, where the generated multiple carriers, which ultimately decay to the edges of the dispersive bands by means of IA processes, acquire lighter mass and this could allow their more efficient separation before recombination. We argue that this may be applicable to the case of halide perovskites and it could be one of the reasons for their observed photovoltaic efficiency. We discuss the criteria one should use to uncover the appropriate material in order to harvest the optimum effect of IA for the spectrum of the solar photon energy distribution. |
Thursday, March 5, 2020 3:42PM - 3:54PM |
U01.00007: A Molecular Dynamics Study of Silicon Nanowire/Silica Aerogel Nanocomposite Thermal Conductivity Mitra Sedeeqi, Bruce Edward White Growing demand for waste heat recycling technology have accelerated research in efficient thermoelectric materials. Because silicon has a large Seebeck coefficient, can be easily doped to be both n-type and p-type and has high Earth abundance, research has focused on methods for reducing the lattice thermal conductivity of this material through nanostructuring techniques. In this work, Reverse Non-Equilibrium Molecular Dynamics (RNEMD) is applied to study the thermal conductivity of silicon-silica aerogel nanocomposites. Embedding the silicon nanowire in an aerogel is found to result in significant reductions to the lattice thermal conductivity of the nanowire when the surface of the nanowire is a major source of phonon scattering. These results can be explained based on the diffuse mismatch model of phonon transport at interfaces and point to a possible path to independently optimize the electronic components of a thermoelectric material from that of its lattice vibration components. |
Thursday, March 5, 2020 3:54PM - 4:06PM |
U01.00008: Brownian Ratchets as Non-Traditional Energy Harvesters Anthony Cho, Arjendu Kishore Pattanayak We seek to harness non-traditional forms of energy such as vibrations and blackbody radiation via Brownian ratchets. We have simulated particle diffusion in a thermal bath subject to an asymmetric (ratchet) potential. The potential has been studied using both white and colored noise to incur net directed transport. We find a minimum temperature for the thermal bath to obtain a maximum transport velocity dependent on the level of asymmetry and the diffusion constant. We also find that the transport velocity was equivalent regardless if the particle traveled in the direction of or against the bias. |
Thursday, March 5, 2020 4:06PM - 4:18PM |
U01.00009: Elemental Additions to Enhance Precipitate Formation in Superalloys Tyler Whitaker, Brayden Bekker, Hayden S Oliver, Gus Hart Recent discoveries of cobalt-based superalloys has sparked interest in finding new ternary alloy systems that exhibit the essential L12 precipitate hardening mechanism. The higher operating temperature of cobalt-based alloys translates to increases in fuel efficiency for energy applications. One recent high-throughput search identified six new potential superalloys, two of which were confirmed to be at least metastable. Using the Moment Tensor Potential (MTP) framework, we explore fourth element additions to these new ternary systems. Several elements lower the formation enthalpy of the L12 phase, possibly enhancing its stability. These elemental additions offer a promising direction in designing new superalloys. |
Thursday, March 5, 2020 4:18PM - 4:30PM |
U01.00010: Proficient quantum energy storage for in-plane microsupercapacitor using hybrid nanocomposite Meenakshi Talukdar, Sushant Kumar Behera, Pritam Deb Planar micro-supercapacitors with innovative characteristics are recognized as one of the most feasible next generation power source for incorporation in electronics devices. Microsupercapacitor (MSCs), in the world of microelectronics have engrossed more and more attention due to its power and energy storage capacity but achieving desired electrode structure design is still an open challenge .Our study has reported a novel concept of achieving synergic effect of both EDLC and pseudocapacitive in 2D architecture with ultra-high energy density and high capacitive retention, catering the need of fast growing energy demands in portable miniaturized storage device. This miniaturized micro-supercapacitor can offer a nano/micro-scale power source apposite to meet the applications which require higher operating currents and voltages in a short time-frame<span style="font-size:10.8333px"> [DOI: </span>10.1039/C9DT02423A]. |
Thursday, March 5, 2020 4:30PM - 4:42PM |
U01.00011: Control of Quantum Energy Transport by Environmental Engineering Chikako Uchiyama The energy transport in the light harvesting mechanisms of photosynthetic bacteria has attracted intensive attentions. Especially, the model proposed to describe the mechanism which shows that environmental noises can assist the energy transport[1] has been intensively studied, since the model has opened a way for biomimetic studies. However, the complexities of biological molecules have been obstacles to reproduce the mechanism of energy transport. To overcome the difficulty, we propose another way to control energy transport by an active control on environment. In this presentation, we show that we can accelerate an energy transport through a linear chain model by applying stochastic noises with spatial-temporal correlations[2]. Especially, we show that anti-spatial correlation and optimum correlation time can accelerate energy transport. We believe that the results show new possibilities to improve energy transport. [1] P. Rebentrost, et al.,New J. Phys. 11, 033003 (2009); M. B. Plenio, and S. F. Huelga, New J. Phys. 10, 113019 (2008).[2] C. Uchiyama, W. J. Munro, and K. Nemoto, npj Quantum Information vol.4, 33 (2018). |
Thursday, March 5, 2020 4:42PM - 4:54PM |
U01.00012: Stability of dynamically disordered materials from ab initio molecular dynamics Sergei Simak, Johan Klarbring Large atomic displacements and atoms vibrating without well-defined equilibrium positions are the signatures of dynamically disordered materials. These materials show immense potential in applications, such as superionic conductors, solid-state batteries, and fuel cells. The biggest obstacle in living up to this potential is the limited stability of the dynamically disordered phases. To predict it the free energies has to be calculated. That has long been a challenge. We have introduced a method that offers a solution [1]. It relies on a density functional theory (DFT), ab initio molecular dynamics (AIMD), and stress-strain thermodynamic integration between the dynamically disordered phase and its metastable ordered variant. The successful application of the method to the stability of notorious cubic bismuth oxide and lithium carbide [2] will be discussed. |
Thursday, March 5, 2020 4:54PM - 5:06PM |
U01.00013: Framework Materials as Porous Liquids Rachel Mow, Wade Braunecker, Thomas Gennett Porous liquids have recently been introduced as a new class of material with great potential for gas storage and purification. The permanent porosity and fluid properties of porous liquids provide an avenue for gas storage and transportation that avoids the processing restrictions of solid porous materials. Despite the promise of porous liquids, only a handful of these materials have been realized to date. This work develops porous liquids from covalent organic frameworks (COFs). Colloidal 3D imine-based COFs are synthesized with particle size control down to 60 nm. The colloidal COFs are suspended in a bulky ionic liquid solvent that is size-excluded from entering the COF pore, demonstrating a Type 3 porous liquid. Gas sorption studies are used to determine the gas uptake and adsorption enthalpy of hydrogen and other gases in the porous liquid. This work presents a new type of tunable organic porous liquid that can be used for gas storage and separation. |
Thursday, March 5, 2020 5:06PM - 5:18PM |
U01.00014: Order in the ground state of a simple cubic dipole lattice in an external field Sahel Ashhab, Marcelo Carignano, Mohamed El-Amine Madjet Motivated by the presence of a lattice of rotating molecular dipoles in the high-temperature phase of methylammonium lead iodide, we investigate the ground state of a simple cubic lattice of dipoles interacting with each other via the dipole-dipole interaction and with an external field via the standard, linear dipole-field interaction. In the absence of an external field, the ground state is infinitely degenerate, and all the configurations in the ground state manifold are periodic along the three lattice axes with a period of two lattice sites. Using a 1000-dipole lattice as a unit cell in numerical simulations of an infinite simple cubic lattice, we determine the ground state dipole configurations in the presence of an external field. We then analyze the polarization, dipole orientation statistics and correlations in these configurations. Our calculations show that for some special directions of the external field the two-site periodicity in the dipole configurations is preserved, while in the general case this periodicity is lost and complex dipole configurations form under the influence of the external field. More specifically, a sudden transition from two-site periodic configurations to irregular configurations occurs at a finite value of the applied field strength. |
Thursday, March 5, 2020 5:18PM - 5:30PM |
U01.00015: Kepler's Laws and Elliptic path might suggest that nature uses the function of TIME to provide needed energy for its accelerated motion Ibrahim Hanna Classical physics correctly calculate planetary positions, and energy conservation as a function of position, however using Kepler's laws as a function of time, may conclude that potential energy available for a planet's motion, is bigger than kinetic energy used at the actual path, and have the path was to be circular, such energy difference would not exist. Keplers equation A^3/T^2 =Constant, as a function of time, may also explain how nature chooses the elliptic path,to gain such energy difference, from time, to maintain and finance its accelerated motion, where Time is a form of energy, and where the expansion of universe, is not measured by coordinates of positions, but by positive coordinates of time while black holes can be identified by negative coordinates of time. |
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