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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A Superconducting Praseodymium Nickelate with Infinite Layer Structure

A variety of nickel oxide compounds have long been studied for their manifestation of various correlated electron phenomena. Recently, superconductivity was observed in nanoscale infinite layer nickelate thin films of Nd 0.8 Sr 0.2 NiO 2 , epitaxially stabilized on SrTiO 3 substrates via topotactic reduction from the perovskite precursor phase. In this paper, we present the synthesis and properties of PrNiO 2 thin films on SrTiO 3 . Upon doping in Pr 0.8 Sr 0.2 NiO 2 , we observe superconductivity with a transition temperature of 7–12 K and robust critical current density at 2 K of 334 kA/cm 2 . These findings indicate that superconductivity in the infinite layer nickelates is relatively insensitive to the details of the rare earth 4 f configuration. Furthermore, they motivate the exploration of a broader family of compounds based on two-dimensional NiO 2 planes, which will enable systematic investigation of the superconducting and normal state properties and their underlying mechanisms.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Ternary arsenides ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) with layered structures

The four ternary arsenides ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) were obtained by reaction of the elements at 600–650 °C. They adopt an orthorhombic structure (space group Pnma, Z=4, with cell parameters ranging from a=9.9931(11) Å, b=3.7664(4) Å, c=18.607(2) Å for KGe{sub 3}As{sub 3} to a=10.3211(11) Å, b=4.0917(4) Å, c=19.570(2) Å for RbSn{sub 3}As{sub 3}) containing corrugated [Tt{sub 3}As{sub 3}] layers built from Tt-centred trigonal pyramids and tetrahedra forming five-membered rings decorated with As handles. They can be considered to be Zintl phases with Tt atoms in +4, +3, and +1 oxidation states. Band structure calculations predict that these compounds are semiconductors with narrow band gaps (0.71 eV in KGe{sub 3}As{sub 3}, 0.50 eV in KSn{sub 3}As{sub 3}). - Graphical abstract: Ternary arsenides ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) contain corrugated layers with Tt atoms in three different oxidation states and are narrow band gap semiconductors. Display Omitted - Highlights: • ATt{sub 3}As{sub 3} (A=K, Rb; Tt=Ge, Sn) contains Tt atoms in three oxidation states. • The structure differs from NaGe{sub 3}P{sub 3} in terms of layer stacking arrangement. • The compounds are predicted to be narrow band gap semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal–insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment and theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Evolution of photoresist layer structure and surface morphology under fluorocarbon‐based plasma exposure

Abstract Ion bombardment of photoresist materials during plasma etching results in the formation of a surface dense amorphous carbon (DAC) layer that contributes to both etch resistance and the development of surface roughness. Real‐time ellipsometric measurements/analysis reveals that a C 4 F 8 ‐containing plasma interacts with an Ar‐plasma‐formed DAC layer to produce a modified DAC/fluorocarbon (FC) layer by FC deposition/diffusion of fluorine into the surface. The depletion of the DAC layer via modification and ion bombardment causes the etch rate of the bulk layer to increase. As the modified surface layer is formed, a noticeable decrease in surface roughness decrease is observed. These findings provide an understanding of the mechanisms of atomic layer etching processes in photoresist materials.

Pranda, Adam↗
DOE OSTI2021

Study of the Atmospheric Boundary Layer Structure during AWAKEN (Final Report)

The American Wake Experiment (AWAKEN, https://openei.org/wiki/AWAKEN) is a collaborative, international field campaign funded by the Department of Energy (DOE) to study the dynamic and turbulent properties of wind farm wakes. The scope of the project ranges from studying individual turbine wakes, wake interactions within wind farms, to downstream wake effects of wind farms on the atmospheric boundary layer (ABL) and mesoscale environment. The latter effects influence the performance of wind farms deployed downwind and modify the weather and climate in the region. The focus of our project is on studying the mesoscale and boundary-layer effects of wind farms in more detail using advanced boundary-layer profiling facilities.

17 WIND ENERGY↗
DOE OSTI2017

X-ray fluorescence at nanoscale resolution for multicomponent layered structures: A solar cell case study

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer–Lambert's law, formulae are presented in a general integral form and numerically applicable framework. Here, the procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se 2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically.

14 SOLAR ENERGY↗
DOE OSTI2016

AFM investigation of effect of absorbed water layer structure on growth mechanism of octadecyltrichlorosilane self-assembled monolayer on oxidized silicon

The growth mechanism of an octadecyltrichlorosilane (OTS) self-assembled monolayer on a silicon oxide surface at various relative humidities has been investigated. Atomic force microscopy images show that excess water may actually hinder the nucleation and growth of OTS islands. A moderate amount of water is favorable for the nucleation and growth of OTS islands in the initial stage; however, the completion of the monolayer is very slow in the final stage. The growth of OTS islands on a low-water-content surface maintains a relatively constant speed and requires the least amount of time. The mobility of water molecules is thought to play an important role in the OTS monolayers, and a low-mobility water layer provides a steady condition for OTS monolayer growth.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Effects of Vegetation and Topography on the Boundary Layer Structure above the Amazon Forest

Observational data from two field campaigns in the Amazon forest were used to study the vertical structure of turbulence above the forest. The analysis was performed using the reduced turbulent kinetic energy (TKE) budget and its associated two-dimensional phase space. Results revealed the existence of two regions within the roughness sublayer in which the TKE budget cannot be explained by the canonical flat-terrain TKE budgets in the canopy roughness sublayer or in the lower portion of the convective ABL. Data analysis also suggested that deviations from horizontal homogeneity have a large contribution to the TKE budget. Results from LES of a model canopy over idealized topography presented similar features, leading to the conclusion that flow distortions caused by topography are responsible for the observed features in the TKE budget. These results support the conclusion that the boundary layer above the Amazon forest is strongly impacted by the gentle topography underneath.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Lagrangian Evolution of the Northeast Pacific Marine Boundary Layer Structure and Cloud during CSET

Flight data from the Cloud System Evolution over the Trades (CSET) campaign over the Pacific stratocumulus-to-cumulus transition are organized into 18 Lagrangian cases suitable for study and future modeling, made possible by the use of a track-and-resample flight strategy. Analysis of these cases shows that 2-day Lagrangian coherence of long-lived species (CO and O 3 ) is high ($r$ = 0.93 and 0.73, respectively), but that of subcloud aerosol, MBL depth, and cloud properties is limited. Although they span a wide range in meteorological conditions, most sampled air masses show a clear transition when considering 2-day changes in cloudiness (−31% averaged over all cases), MBL depth (+560 m), estimated inversion strength (EIS; −2.2 K), and decoupling, agreeing with previous satellite studies and theory. Changes in precipitation and droplet number were less consistent. The aircraft-based analysis is augmented by geostationary satellite retrievals and reanalysis data along Lagrangian trajectories between aircraft sampling times, documenting the evolution of cloud fraction, cloud droplet number concentration, EIS, and MBL depth. An expanded trajectory set spanning the summer of 2015 is used to show that the CSET-sampled air masses were representative of the season, with respect to EIS and cloud fraction. Two Lagrangian case studies attractive for future modeling are presented with aircraft and satellite data. The first features a clear Sc–Cu transition involving MBL deepening and decoupling with decreasing cloud fraction, and the second undergoes a much slower cloud evolution despite a greater initial depth and decoupling state. Finally, potential causes for the differences in evolution are explored, including free-tropospheric humidity, subsidence, surface fluxes, and microphysics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Layer-structured triple-conducting electrocatalyst for water-splitting in protonic ceramic electrolysis cells: Conductivities vs. activity

Electron, proton and oxygen-triple-conducting materials are becoming the dominant steam electrode candidate to break the rate limit on the water-splitting reaction that throttles the performance of protonic ceramic electrolysis cells (PCECs). In this study, based on Pr 2 NiO 4+δ Ruddlesden-Popper phase, we manipulate these conductivities by Pr-site Ba substitution to probe the correlation of each conductivity with the kinetics of the elementary reaction steps. It is found that the proton conductivity is vital to sustain an extended active surface area for faster adsorption of reactants and desorption of products. The effect of oxygen conductivity is surprisingly found insignificant in the water-splitting reaction. On the contrary, surface oxygen removal is discovered as the most rate-limiting process. The electronic conductivity is not a direct limiting factor. However, an electron transfer process between the current collector and the electrode junction could introduce extra resistance that is perceptible at a high operating temperature range. The best water-splitting activity is obtained on a proton conductivity/oxygen surface desorption capability well-balanced sample after Ba substitution. As a result, a water-splitting reaction resistance of 0.022 Ωcm 2 , a current density of 1.96 A/cm 2 at 700 °C is achieved on Pr 1.7 Ba 0.3 NiO 4+δ , one of the best performances for PCECs.

25 ENERGY STORAGE↗
DOE OSTI2019

Molecular Investigation of Oxidized Graphene: Anatomy of the Double-Layer Structure and Ion Dynamics

We investigated the influence of surface oxidization of planar graphene electrodes on charge storage and ion dynamics of supercapacitors. Our approach compared two distinct ionic liquid (IL) electrolytes: tetraethylammonium tetrafluoroborate solvated in acetonitrile (TEA-BF4/ACN) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide solvated in acetonitrile (EMIm-TFSI/ACN). Both experimental electrochemical tests and molecular dynamics (MD) simulations showed positive, electrolyte-specific influences of hydroxyl-free electrode interfaces on capacitance. In the EMIm-TFSI/ACN system, the hydroxylated surface, because of its strong interaction with anions, impeded surface charge storage. On the other hand, in the case of TEA-BF4/ACN, the distribution and orientation of ACN across the system exerted vital influence on the capacitance, especially on the positive hydroxyl-free electrode. Furthermore, MD simulations of ion mobility with respect to the electrode surface in the lateral and perpendicular directions revealed significantly slower diffusion performance on the oxidized surface. Our efforts enhanced the level of fundamental understanding of the effects of hydroxyl groups on electrode–electrolyte interfaces and resulting supercapacitor performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗