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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Experimental Study of the Fundamental Properties of Warm Dense Mixtures

The aim of the proposed research was to provide a multi-scale study of the properties of warm dense hydrocarbons, by studying the thermodynamic properties through the equation of state and the microscopic properties by x-ray scattering. Understanding the fundamental properties of warm dense mixtures is an intellectual challenge due to the complexity of the system. Unlike liquids or gases, where constituent particle interactions occur through collisions or bonding between valence electrons, in these strongly coupled systems the atoms will be partially ionized and compressed so tightly together that interactions between the inner core electrons can play a role in the systems chemistry. Advances in computational capabilities and development of new theoretical models have been used to predict the properties of mixtures but there is currently no experimental data of the fundamental interaction between the particles in mixtures to test these predictions against. The proposed research was to experimentally investigate the interaction of the different species in hydrocarbons by measuring the compressibility of substances with different carbon and hydrogen ratios and the complexity of the microscopic interactions through elastic and inelastic x-ray scattering. To study the bulk properties of warm dense hydrocarbons we established the Warm Dense Matter Research Laboratory (WDMRL) in the Institute for Shock Physics at Washington State University. The goal was for experiments in the WDMRL to determine shock loading conditions of interest in the hydrocarbon mixtures. We planned on using Hugoniot EOS measurements and a range of carbon and hydrogen concentrations to determine conditions when the EOS of the mixture varied significantly from that of the classical mixing model. Even though shock transit measurements through aluminum foils suggested pressures upto 400GPa, the experiments in the WDMRL were unsuccessful in getting usable shockwave compression data above 100GPa in polystyrene which was below the pressure of interest for hydrocarbon mixtures (>200GPa). To complete the project, we tested a technique using x-ray phase contrast imaging to map the location of tracer layers in a test sample of polycarbonate to record the material motion in dynamically compressed samples. A technique that will be useful for future warm dense matter experiments. These experiments used <200nm gold layers in polycarbonate samples to measure the material velocity and shock speed using x-ray phase contrast imaging. These results were compared to continuum surface measurements performed at ISP and show that the tracer layer technique can measure hydrodynamic properties accurately in dynamically compressed materials.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

On the Efficient Evaluation of the Exchange Correlation Potential on Graphics Processing Unit Clusters

The predominance of Kohn–Sham density functional theory (KS-DFT) for the theoretical treatment of large experimentally relevant systems in molecular chemistry and materials science relies primarily on the existence of efficient software implementations which are capable of leveraging the latest advances in modern high-performance computing (HPC). With recent trends in HPC leading toward increasing reliance on heterogeneous accelerator-based architectures such as graphics processing units (GPU), existing code bases must embrace these architectural advances to maintain the high levels of performance that have come to be expected for these methods. In this work, we purpose a three-level parallelism scheme for the distributed numerical integration of the exchange-correlation (XC) potential in the Gaussian basis set discretization of the Kohn–Sham equations on large computing clusters consisting of multiple GPUs per compute node. In addition, we purpose and demonstrate the efficacy of the use of batched kernels, including batched level-3 BLAS operations, in achieving high levels of performance on the GPU. We demonstrate the performance and scalability of the implementation of the purposed method in the NWChemEx software package by comparing to the existing scalable CPU XC integration in NWChem.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1971

Chemical evolution and the origin of life; Proceedings of the Third International Conference, Pont-a-Mousson, France, April 19-25, 1970. Volume 1 - Molecular evolution.

The present state of investigations on the origin of life is surveyed together with the current state of molecular paleontology. General and theoretical subjects discussed include an energetic approach to prebiological chemistry, the recognition of description and function in chemical reaction networks, and the origin and development of optical activity of bio-organic compounds on the primordial earth. Other fields considered are the syntheses of small molecules, oligomers and polymers; photochemical processes; the origin of biological structures; primitive biochemistry and biology; and exobiology. Individual items are abstracted in this issue.

Buvet, R.↗
NASA NTRS1992

Titan

The following topics are discussed with respect to Titan: observations of the atmosphere; laboratory simulations and theoretical models of Titan's atmosphere; endpoints of atmospheric chemistry - aerosols and oceans; exobiology; and the next steps in understanding Titan.

Owen, Tobias↗
NASA NTRS1997

Workshop on Parent-Body and Nebular Modification of Chondritic Materials

Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

Zolensky, M. E.↗
NASA NTRSDate not supplied

Progress of Aluminum/Air Battery Development for SUSAN Electrofan Project

Safe and high-performance battery technologies are demanded by the Subsonic Single Aft eNgine (SUSAN) Electrofan concept design project under National Aeronautics and Space Administration (NASA) electrified aircraft development program. Aluminum (Al)-air battery with very high theoretical specific energy density, is considered as promising battery chemistry which has the potential to meet the targeted specific energy goal of primary battery energy technology for the SUSAN project. In addition to having the exceptional electrochemical properties, aluminum is light weight, rich abundance, low cost, environmentally friendly, and has a good electrical conductivity and recyclability, which is among the key characteristics of SUSAN project on battery energy needs. A non-flammable aqueous electrolyte is used to prevent the fire and thermal runaway hazard for the safety of this battery chemistry. However, there are challenges for Al-air battery in practical application, mainly due to self-corrosion of Al and slow kinetics of oxygen reduction in air-cathode to impact the high-rate performance. Progress on addressing these challenges was made and some of the results were reported in our previous paper. In this paper, the focus is on the investigation of various factors, including electrolyte concentrations, temperature, and air-cathode loadings on ionic transport properties and discharge performance at different current densities. The results are discussed, and the progress is reported.

James J Wu↗
DOE OSTI2022

Exploring Electrosynthesis: Bulk Electrolysis and Cyclic Voltammetry Analysis of the Shono Oxidation

As electrochemistry continues to gain broader acceptance and use within the organic chemistry community, it is important that advanced undergraduate students are exposed to fundamental and practical knowledge of electrochemical applications for chemical synthesis. Herein, we describe the development of an undergraduate laboratory experience that introduces synthetic and analytical electrochemistry concepts to an advanced organic chemistry class. Experiments focus on the electrooxidative α-functionalization of carbamates, more generally known as the Shono oxidation, and include cyclic voltammetry analysis of two cyclic carbamates and a constant current bulk electrolysis reaction. Here, the exercise offers students an authentic experience in organic electrochemistry, lays a practical and theoretical foundation for future engagement with concepts in electrochemistry and redox chemistry, and strengthens fundamental organic chemistry skills.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2016

The Muscles Treasury Survey. I. Motivation and Overview

Ground- and space-based planet searches employing radial velocity techniques and transit photometry have detected thousands of planet-hosting stars in the Milky Way. With so many planets discovered, the next step toward identifying potentially habitable planets is atmospheric characterization. While the Sun-Earth system provides a good framework for understanding the atmospheric chemistry of Earth-like planets around solar-type stars, the observational and theoretical constraints on the atmospheres of rocky planets in the habitable zones (HZs) around low-mass stars (K and M dwarfs) are relatively few. The chemistry of these atmospheres is controlled by the shape and absolute flux of the stellar spectral energy distribution (SED), however, flux distributions of relatively inactive low-mass stars are poorly understood at present. To address this issue, we have executed a panchromatic (X-ray to mid-IR) study of the SEDs of 11 nearby planet-hosting stars, the Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) Treasury Survey. The MUSCLES program consists visible observations from Hubble and ground-based observatories. Infrared and astrophysically inaccessible wavelengths (EUV and Lyalpha) are reconstructed using stellar model spectra to fill in gaps in the observational data. In this overview and the companion papers describing the MUSCLES survey, we show that energetic radiation (X-ray and ultraviolet) is present from magnetically active stellar atmospheres at all times for stars as late as M6. The emission line luminosities of C IV and Mg II are strongly correlated with band-integrated luminosities and we present empirical relations that can be used to estimate broadband FUV and XUV (is equivalent to X-ray + EUV) fluxes from individual stellar emission line measurements. We find that while the slope of the SED, FUV/NUV, increases by approximately two orders of magnitude form early K to late M dwarfs (approximately equal 0.01-1), the absolute FUV and XUV flux levels at their corresponding HZ distances are constant to within factors of a few, spanning the range 10-70 erg per (sq cm) s in the HZ. Despite the lack of strong stellar activity indicators in their optical spectra, several of the M dwarfs in our sample show spectacular UV flare emission in their light curves. We present an example with flare/quiescent ultraviolet flux ratios of the order of 100:1 where the transition region energy output during the flare is comparable to the total quiescent luminosity of the star E(sub flare)(UV) approximately 0.3 L(sub *) delta (t) (delta t = 1 s). Finally, we interpret enhanced L(line)/L(sub Bol) ratios for C IV and N V as tentative observational evidence for the interaction of planets with large planetary mass-to-orbital distance ratios (M(sub plan)/A(sub plan)) with the transition regions of their host stars.

Infrared and astrophysically inaccessible waveleng↗
DOE OSTI2022

Dilute Alloys Based on Au, Ag, or Cu for Efficient Catalysis: From Synthesis to Active Sites

The development of new catalyst materials for energy-efficient chemical synthesis is critical as over 80% of industrial processes rely on catalysts, with many of the most energy-intensive processes specifically using heterogeneous catalysis. Catalytic performance is a complex interplay of phenomena involving temperature, pressure, gas composition, surface composition and structure over multiple length and time scales. In response to this complexity, the integrated approach to heterogeneous dilute-alloy catalysis reviewed here brings together materials synthesis, mechanistic surface chemistry, reaction kinetics, in-situ and operando characterization, and theoretical calculations in a coordinated effort to develop design principles to predict and improve catalytic selectivity. Dilute alloy catalysts—in which isolated atoms or small ensembles of the minority metal on the host metal lead to enhanced reactivity while retaining selectivity—are particularly promising as selective catalysts. Several dilute alloy materials using Au, Ag and Cu as the majority host element, including more recently introduced support-free nanoporous metals and oxide-supported nanoparticle "raspberry colloid templated (RCT)" materials, are reviewed for selective oxidation and hydrogenation reactions. Progress in understanding how such dilute alloy catalysts can be used to enhance selectivity of key synthetic reactions is reviewed, including quantitative scaling from model studies to catalytic conditions. The dynamic evolution of catalyst structure and composition studied in surface science and catalytic conditions and their relationship to catalytic function are also discussed, followed by advanced characterization and theoretical modeling that have been developed to determine the distribution of minority metal atoms at or near the surface. Furthermore, the integrated approach demonstrates the success of bridging the divide between fundamental knowledge and design of catalytic processes in complex catalytic systems, which can accelerate the development of new and efficient catalytic processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Electrochemical Kinetics of Stable Isotopes (Final Report)

Stable isotopes are sensitive indicators to the mass transport and chemical reactions that occur during potentiostat-controlled electroplating of metals from aqueous (and some non-aqueous) metal-salt solutions. The goal of this research program is to measure the stable isotope fractionation during electrochemical processes, how the isotope-dependent rates are sensitive to chemistry, temperature, and electrochemical kinetics, and to use these measurements to develop a theoretical framework for a kinetic isotope effect that is able to predict kinetic isotope fractionation factors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Experimental Constraints on Solid Nitride Phases in Rocky Mantles of Reduced Planets and Implications for Observable Atmosphere Compositions

Abstract Astronomical surveys have discovered thousands of transiting exoplanets, revealing that rocky planets are common in the galaxy. A planet's interior chemistry is frequently inferred by average density, described by mass‐radius (M‐R) relationships. However, M‐R relationships give rise to non‐unique interpretations of a planet's interior composition, an issue that limits our ability to characterize far‐away worlds. We present experimental and density functional theoretical results addressing the influence of an ultra‐reducing (oxygen‐poor) interior chemistry on rocky mantle phases and discuss the possible implications for atmospheric observables. We show that silicon carbide (SiC) and molecular nitrogen (N 2 ) react to form solid silicon nitride (γ‐Si 3 N 4 ) at high pressures and high temperatures in a laser‐heated diamond‐anvil cell, consistent with ab initio computations. Si 3 N 4 remains stable under extreme conditions and when quenched to ambient conditions. As SiC is a common compound found under very reducing conditions, these results indicate that nitrogen may form solid phases in an oxygen‐poor rocky planet. If, by sequestering nitrogen in a planet's mantle, the distribution of nitrogen between a planet's interior and atmosphere is altered (i.e., a nitrogen‐rich mantle and nitrogen‐poor atmosphere), these results indicate that there may be atmospheric observables connected to the mantle‐redox state of a rocky planet besides the oxygen‐containing phases ubiquitous in exoplanet literature.

Daviau, Kierstin↗
DOE OSTI2022

Surface Chemistry and Heterogeneous Processes in Solar-Driven Pyridine-Catalyzed CO 2 Reduction

The objective of our studies was to advance our fundamental understanding of the surface chemistry and heterogeneous processes that occur in solar-driven pyridine-catalyzed CO 2 reduction. Solar-driven CO 2 reduction to produce fuels offers tremendous promise but commercial deployment is impeded by the lack of suitable catalysts that simultaneously provide high efficiency and product selectivity. Pyridine (C 5 H 5 N) has been reported as an effective, selective co-catalyst in the conversion of CO 2 to methanol (CH 3 OH) in photoelectrochemical cells employing gallium phosphide (GaP) photocathodes. However, despite considerable electrochemical characterization and a large number of theoretical considerations, there are still many fundamental questions about the surface chemistry and heterogeneous processes that are involved in the conversion mechanism. Our research was aimed at investigating the role of the electrode surface and heterogeneous processes in this catalysis. Gaining this fundamental understanding of the origin of pyridine’s effectiveness is important to the continued optimization of solar-driven CO 2 reduction.

10 SYNTHETIC FUELS↗
DOE OSTI2022

The basics of quantum computing for chemists

The rapid and successful strides in quantum chemistry in the past decades can be largely credited to a conspicuous synergy between theoretical and computational advancements. However, the architectural computer archetype that enabled such a progress is approaching a state of more stagnant development. One of the most promising technological avenues for the continuing progress of quantum chemistry is the emerging quantum computing paradigm. This revolutionary proposal comes with several challenges, which span a wide array of disciplines. In chemistry, it implies, among other things, a need to reformulate some of its long established cornerstones in order to adjust to the operational demands and constraints of quantum computers. Due to its relatively recent emergence, much of quantum computing may still seem fairly nebulous and largely unknown to most chemists. It is in this context that here we review and illustrate the basic aspects of quantum information and their relation to quantum computing insofar as enabling simulations of quantum chemistry. As a result, we consider some of the most relevant developments in light of these aspects and discuss the current landscape when of relevance to quantum chemical simulations in quantum computers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

QuDPy: A Python-based tool for computing ultrafast non-linear optical responses

Nonlinear Optical Spectroscopy is a well-developed field with theoretical and experimental advances that have benefited multiple disciplines, including chemistry, biology, and physics. However, for the accurate interpretation of the corresponding multi-dimensional spectra, there is a need for precise quantum dynamical simulations based on model Hamiltonians. In this article, we present the initial release of our code, QuDPy (Quantum Dynamics in Python), which provides a robust numerical platform for performing quantum dynamics simulations based on model systems, including open quantum systems. Furthermore, a distinguishing feature of our approach is the ability to specify various high-order optical response pathways in the form of double-sided Feynman diagrams through a straightforward input syntax. This syntax outlines the time-ordering of ket-sided or bra-sided optical interactions acting on the time-evolving density matrix of the system. We utilize the quantum dynamics capabilities of QuTip to simulate the spectral response of complex systems, allowing us to compute virtually any $n$-th order optical response of the model system. To illustrate the utility of our approach, we provide a series of example calculations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1980

Analysis of NASA JP-4 fire tests data and development of a simple fire model

The temperature, velocity and species concentration data obtained during the NASA fire tests (3m, 7.5m and 15m diameter JP-4 fires) were analyzed. Utilizing the data analysis, a sample theoretical model was formulated to predict the temperature and velocity profiles in JP-4 fires. The theoretical model, which does not take into account the detailed chemistry of combustion, is capable of predicting the extent of necking of the fire near its base.

Raj, P.↗
NASA NTRS1989

Theory and observations: Model simulations of the period 1955-1985

The main objective of the theoretical studies presented here is to apply models of stratospheric chemistry and transport in order to understand the processes that control stratospheric ozone and that are responsible for the observed variations. The model calculations are intended to simulate the observed behavior of atmospheric ozone over the past three decades (1955-1985), for which there exists a substantial record of both ground-based and, more recently, satellite measurements. Ozone concentrations in the atmosphere vary on different time scales and for several different causes. The models described here were designed to simulate the effect on ozone of changes in the concentration of such trace gases as CFC, CH4, N2O, and CO2. Changes from year to year in ultraviolet radiation associated with the solar cycle are also included in the models. A third source of variability explicitly considered is the sporadic introduction of large amounts of NO sub x into the stratosphere during atmospheric nuclear tests.

Isaksen, Ivar S. A.↗
NASA NTRS1994

Electron density changes in the nighttime D region due to heating by very-low-frequency transmitters

Modification of the nighttime D region electron density (N(sub e)) due to heating by very-low-frequency (VLF) transmitters is investigated theoretically using a four-species model of the ion chemistry. The effects of a 100 kW, a 265 kW, and a 1000 kW VLF transmitter are calculated for three ambient N(sub e) profiles. Results indicate that N(sub e) is reduced by up to 26% at approximately 80 km altitude over a 1000 kW transmitter.

Rodriguez, Juan V.↗