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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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273 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Interplay between Ion Transport, Applied Bias, and Degradation under Illumination in Hybrid Perovskite p-i-n Devices

In this work, we studied ion transport in hybrid organic–inorganic perovskite p-i-n devices as a function of applied bias under device operating conditions. Using electrochemical impedance spectroscopy (EIS) and equivalent circuit modeling, we elucidated various resistive and capacitive elements in the device. We show that ion migration is predictably influenced by a low applied forward bias, characterized by an increased capacitance at the hole-transporting (HTM) and electron-transporting material (ETM) interfaces, as well as in bulk. However, unlike observations in n-i-p devices, we found that there is a capacitive discharge leading to ion redistribution in the bulk at high forward biases. Furthermore, we show that a chemical double-layer capacitance buildup as a result of ion accumulation impacts the electronic properties of the device, likely by inducing either charge pinning or charge screening, depending on the direction of the ion-induced field. Finally, we extrapolate ion diffusion coefficients (~10 –7 cm 2 s –1 ) and ionic conductivities (~10 –7 S cm –1 ) from the Warburg mass (ion) diffusion response and show that, as the device degrades, there is an overall depletion of capacitive effects coupled with increased ion mobility.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Miniature motorized inspection tool for DOE Hanford site tank bottoms - 15700

Recently, small amounts of waste have been found in the annulus of tank AY-102, prompting the need for developing inspection tools that can identify the cause and location of the leak. Three separate access paths can be used to obtain information regarding the tank bottom condition. The inspection may be conducted via: 1) Refractory air slots through the annulus; 2) 4'' annulus air supply pipe to central air slots; 3) 6'' leak detection pit drain from the central sump. There are various environmental and physical constraints which the tool will have to adhere to. In order for the tool to be successful, it must be capable of the following: Travel through small cooling channels with dimensions as small as 1.5'' x 1.5''; Provide live video feedback; Produce enough torque to overcome the tether drag force; Inverted travel to avoid obstacles such as tank corrosion; Navigate up to 38 feet to the tank center, while maneuvering through four 90 deg. turns. A model of the inspection tool has been designed, assembled and reported. Areas of potential performance improvement were observed; these areas are the basis of the following design, as seen above. The changes include: The addition of an additional 4 wheels; Body modification to house the camera; A loft on the bottom from the tools edge to the magnets lowest edge; Shaving the hubs of the current wheels; Control method changed to a joystick. The tank configuration through which the tool will have to maneuver are the following: 72 outer ring slots (1.5'' x 1.5'' x 17'); 36 ring slots (2'' x 1.5'' x 12'); 18 inner slots (3'' x 1.5'' x 7'). The components used for this design iteration are not radiation hardened nor are they designed to withstand elevated temperatures. However, this prototype has been constructed with the final goal of being radiation hardened and able to withstand elevated temperatures in mind. The components that make up this design iteration are the following: Arduino Uno board with ATMega328 micro-controller; Joystick shield kit for the Arduino Uno; Eggsnow USB Borescope Endoscope 5.5 mm inspection camera; 136:1 Sub-micro Plastic Planetary Gearmotor; 14 x 4.5 mm wheels; 3D-printed body; 3D-printed free rolling shafts; Neodymium magnet - 1 h x 3/8 h x 1/16 h; 4.53 lb pull force. In the time to come, there are a few goals that are to be completed. The first group of tasks is associated with the testing and recording of data of the current prototype. This data will be analyzed and appropriate action will be taken based on the results of the testing. The testing will include simulating the challenges that the tool will face in the AY-102 tank. Working with the Hanford DOE site, a bag of Kaolin 2200 will be acquired to be used for the test bed to simulate tank conditions. Further modification will then be made to enable the tool to be able to maneuver through a 90 deg. turn. Completion of this task will be a major milestone, as this tool will be readily usable in the other tanks containing HLW; as other tanks will be easier to maneuver through.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Evidence of Dirac Quantum Spin Liquid in YbZn 2⁢ GaO 5

The emergence of a quantum spin liquid (QSL), a state of matter that can result when electron spins are highly correlated but do not become ordered, has been the subject of a considerable body of research in condensed matter physics [1,2]. Spin liquid states have been proposed as hosts for high-temperature superconductivity [3] and can host topological properties with potential applications in quantum information science [4]. The excitations of most quantum spin liquids are not conventional spin waves but rather quasiparticles known as spinons, whose existence is well established experimentally only in one-dimensional systems; the unambiguous experimental realization of QSL behavior in higher dimensions remains challenging. Here, in this work, we investigate the novel compound $YbZn_{2}GaO_{5}$, which hosts an ideal triangular lattice of effective spin-1/2 moments with no detectable inherent chemical disorder. Thermodynamic and inelastic neutron scattering measurements performed on high-quality single crystal samples of $YbZn_{2}GaO_{5}$ exclude the possibility of long-range magnetic ordering down to 0.06 K, demonstrate a quadratic power law for the specific heat and reveal a continuum of magnetic excitations in parts of the Brillouin zone. Both low-temperature thermodynamics and inelastic neutron scattering spectra suggest that $YbZn_{2}GaO_{5}$ is a U(1) Dirac QSL with spinon excitations concentrated at certain points in the Brillouin zone. We advanced these results by performing additional specific heat measurements under finite fields, further confirming the theoretical expectations for a Dirac QSL on the triangular lattice of $YbZn_{2}GaO_{5}$.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗