Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 62, Number 17
Friday–Saturday, October 20–21, 2017; Fort Collins, CO
Session K5: Condensed Matter and Materials IV |
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Chair: William Rice, University of Wyoming Room: Lory Student Center 376 |
Saturday, October 21, 2017 9:25AM - 9:49AM |
K5.00001: Computational and experimental force multipliers for the discovery of new thermoelectric materials Invited Speaker: Eric Toberer This talk will focus on the development of advanced thermoelectric materials within the Materials Genome Initiative paradigm and the prospects for widespread thermal-to-electric power conversion. These thermoelectric material discovery efforts are driven by a close coupling of theory, computation, and experimental validation. The implementation of a high through-put search of known and hypothetical compounds for thermoelectric performance (NSF-DMREF) has led to the identification of new classes of thermoelectric materials. High throughput experimental measurement of thermoelectric materials serves to complement these computational efforts. Further material development involves demonstrating materials with exceptionally strong phonon-point defect scattering cross-sections and strong lattice anharmonicity. In concert with computation, general design principles for next generation thermoelectric materials emerge. [Preview Abstract] |
Saturday, October 21, 2017 9:49AM - 10:01AM |
K5.00002: Development of Updated Spacecraft Materials Database for Mitigation of Charging Risk Phillip Lundgreen, JR Dennison Spacecraft charging is one of the largest sources of spacecraft anomalies, with over 54{\%} of environment induced anomalies attributed to charging it can also prove to be very costly. The deleterious effects of spacecraft charging are mitigated through two main processes: Risk Informed Decision Making and Continuous Risk Management. There are significant monetary advantages to fixing a problem before it is implemented, for this reason NASA the Air Force and aerospace industries have invested vast resources developing spacecraft charging codes to facilitate the Risk Informed Decision Making process. There is a critical need to understand how the harsh space environment will interact with existing materials and the new materials being developed and incorporated into spacecraft, if scientists and engineers are to select the right material for their designs. Initial efforts by the USU Materials Physics Group established databases with critical material information related to spacecraft charging mitigation This presentation describes the need for an updated spacecraft charging materials database and the efforts to implement this at USU. ~The database will encompass numerous electron emission and transport measurement results including those from groups of scientists around the world. [Preview Abstract] |
Saturday, October 21, 2017 10:01AM - 10:13AM |
K5.00003: Coalescence-induced self-propulsion of viscous droplets on superomniphobic surfaces. Hamed Vahabi, Wei Wang, Seth Davies, Joseph M.Mabry, Arun Kota Coalescence-induced self-propulsion has a key role in releasing the liquid droplets thereby preventing flooding on super-repellent surfaces during the condensation. Prior work has identified different regimes (i.e., inertial-capillary regime and visco-capillary regime) of coalescence-induced self-propulsion via altering the size of the droplets of water on superhydrophobic surfaces. However, there are no reports that have employed liquids with a wide range of surface tensions or wide range of viscosities. This is primarily due to the inability of superhydrophobic surfaces to repel low surface tension liquids. In this work, we fabricated superomniphobic surfaces (i.e., surfaces extremely repellent to both high surface tension liquids like water and low surface tension liquids like oils and alcohols) to overcome this limitation. Our results indicate that our superomniphobic surface can repel liquids with surface tension \textgreater 27 mN/m (e.g., n-hexadecane) and viscosity \textless 220 mPa.s. Utilizing our superomniphobic surfaces, we systematically investigated the coalescence-induced jumping velocity of droplets with various surface tensions and viscosities in the visco-capillary regime and explained the different observations compared to prior work. [Preview Abstract] |
Saturday, October 21, 2017 10:13AM - 10:25AM |
K5.00004: Pulsed Electro-Acoustic Measurements of Charging and Relaxation in Low Density Polyethylene Zachary Gibson, Lee Pearson, Erick Griffiths, Anthony Pearson, JR Dennison A Pulsed Electro-Acoustic (PEA) system was developed and used to study electron charge injection, transport, and relaxation in Low Density Polyethylene (LDPE). Measurements of the time evolution of the charge profiles using the BEI/USU PEA system are compared to predicted models and to previous studies; these are used to verify that the new system is working as expected and to characterize the system's resolution and capabilities. The measurements were made by placing 125 $\mu $m thick LDPE between two electrodes in a parallel plate configuration. Charge was injected via electrode charging for \textasciitilde 30 min with a \textasciitilde 40 MV/m applied field and then allowed to discharge with no applied field for \textasciitilde 30 min. The distribution of charge in the dielectric was measured with PEA by applying a \textasciitilde 100 MHz \textasciitilde 850 V electric pulse to displace the embedded charge, causing an acoustic pulse monitored via time-of-flight with a thin piezoelectric sensor allowing observation of charge accumulation and dissipation. Higher spatial resolution nondestructive PEA measurements of embedded charge in dielectrics offer important information for applications such as spacecraft charging, plasma deposition, accelerator physics, high voltage devices and transmission lines, supercapacitors, microelectronics, and nanodielectric materials. [Preview Abstract] |
Saturday, October 21, 2017 10:25AM - 10:37AM |
K5.00005: Cooling limit of a quantum thermocouple Marco Antonio Jimenez Valencia, Abhay Shankar C. Shastry, Charles A. Stafford A quantum thermocouple is investigated beyond linear response using the method of nonequilibrium Green's functions (NEGF). Insights on the maximum cooling power and coldest temperature achievable are calculated through an effective field theory of the interacting pi-electrons which characterize molecular junctions' transport properties. The limits on cooling are determined by the interplay of the Peltier effect and Joule heating. Different junction couplings (such as sequential exchange and super-exchange) in a quantum thermocouple are tested to determine the possibility of achieving the thermodynamic limit of Carnot efficiency. [Preview Abstract] |
Saturday, October 21, 2017 10:37AM - 10:49AM |
K5.00006: Measuring and Modeling the Conductivity of Highly Insulating Materials David King, Brian Wood, JR Dennison Higher resolution conductivity measurements of very high resistivity polymeric highly disordered insulating materials (HDIM) have been made. Recent modifications of the Constant Voltage Conductivity (CVC) chamber of the Utah State University Materials Physics Group reduce power supply noise and increase the resolution by one to two orders of magnitude, allowing measurements to \textless 10$^{\mathrm{-22}}$ ($\Omega $-cm)$^{\mathrm{-1}}$. A multi-process, physics-based model of the time dependent conductivity is presented to model the conductivity of HDIM. The conductivity of low density polyethylene (LDPE), polyimide (PI), and radiated PI were measured and fit with this model to test its viability, to test the underlying theory of charge transport within HDIM, and to extract properties of the microscopic spatial and energy distribution of trap states inherent in that theory. The conductivity data were also analyzed to investigate subtle variations and trends in the conductivity that were previously not observable due instrumentation limits, including temperature and radiation effects. [Preview Abstract] |
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