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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Contributions to the mechanistic understanding of the microstructural evolution in irradiated U-Mo dispersion fuel

Here, advanced microstructural characterization techniques, such as scanning electron microscopy (SEM) and scanning transmission electron microscopy - energy dispersive x-ray spectroscopy (STEM-EDS), were used to interpret the fuel microstructure evolution and fission products behavior in U-Mo dispersion fuel irradiated in the Advanced Test Reactor (ATR) as part of the European Mini-Plate Irradiation Experiment (EMPIrE) test. The larger as-fabricated fuel grain size achieved by heat-treating the U-Mo powder resulted in slower high burnup structure (HBS) development and reduced fission gas porosity. Slower HBS kinetics was observed at the fuel kernels’ periphery, which contained smaller and less fission gas bubbles at all fission densities (FDs) investigated and was attributed to a locally reduced damage density and fission products concentration, as corroborated with Monte Carlo simulations. The non-refined grains at the fuel kernel periphery hosted a perfectly ordered fission Gas Bubble Superlattice (GBS) up to 6.3 × 10 21 fissions/cm 3 . Nano-scale STEM-EDS analysis presented in this study provided useful information on the GBS characteristic morphology and evolution in U-Mo fuel. The concentration of fission gas in the GBS progressively increased with FD, pointing to an evolution of the nanobubble pressure status with irradiation. A possible connection between the GBS collapse and HBS onset is proposed for which there exists a threshold in the misorientation of the refined sub-grains above which the GBS stability during irradiation is no longer preserved, resulting in the GBS collapse.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Optimizing Geothermal Drilling: Oil and Gas Technology Transfer

There is a significant amount of financial risk associated with geothermal drilling. This study of drilling operations seeks opportunities to improve upon current practices and technologies. The scope of this study included analyzing 21 geothermal wells and 21 oil and gas wells. The goal was to determine a 'Perfect Well' using historical data to compare the best oil and gas well to the best geothermal well. Unfortunately, limitations encountered in the study included missing data (bit records, mud information, etc.) and poor data collection practices An online software database was used to format drilling data to IADC coded daily drilling reports and generate figures for analysis. Six major issues have been found in geothermal drilling operations. These problems include lost circulation, rig/ equipment selection, cementing, penetration rate, drilling program, and time management. As a result of these issues, geothermal drilling averaged 56.4 days longer than drilling comparable oil and gas wells in the wells in this study. Roughly $13.9 million was spent on non-productive time in the 21 geothermal wells, compared with only $1.3 million in the oil and gas wells, assuming a cost of $50,000 per day. Comparable events such as drilling the same sized hole, tripping in/out, cementing, and running the same size casing took substantially less time in the oil and gas wells. Geothermal wells were drilled using older and/or less advanced technology to depths less than 10,000 feet, while oil and gas wells reached 12,500 feet faster with purpose built rigs. A new approach is now underway that will optimize drilling programs throughout the drilling industry using Mechanical Specific Energy (MSE) as a tool to realize efficient drilling processes. Potential improvements for current geothermal operations are: the use of electronic records, real time services, and official glossary terms to describe rig operations, and advanced drilling rigs/technology.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Uncovering dark matter density profiles in dwarf galaxies with graph neural networks

Dwarf galaxies are small, dark-matter-dominated galaxies, some of which are embedded within the Milky Way. Their lack of baryonic matter (e.g., stars and gas) makes them perfect test beds for probing the properties of dark matter—understanding the spatial dark matter distribution in these systems can be used to constrain microphysical dark matter interactions that influence the formation and evolution of structures in our Universe. Here, we introduce a new method that leverages simulation-based inference and graph-based machine learning in order to infer the dark matter density profiles of dwarf galaxies from observable kinematics of stars gravitationally bound to these systems. Our approach aims to address some of the limitations of established methods based on dynamical Jeans modeling. We show that this novel method can place stronger constraints on dark matter profiles and, consequently, has the potential to weigh in on some of the ongoing puzzles associated with the small-scale structure of dark matter halos, such as the core-cusp discrepancy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

The spherically symmetric gravitational collapse of a clump of solids in a gas

In the subject of planetesimal formation, several mechanisms have been identified that create dense particle clumps in the solar nebula. The present work is concerned with the gravitational collapse of such clumps, idealized as being spherically symmetric. Fully nonlinear simulations using the two-fluid model are carried out (almost) up to the time when a central density singularity forms. We refer to this as the collapse time. The end result of the study is a parametrization of the collapse time, in order that it may be compared with timescales for various disruptive effects to which clumps may be subject in a particular situation. An important effect that determines the collapse time is that as the clump compresses, it also compresses the gas due to drag. This increases gas pressure, which retards particle collapse and can lead to oscillation in the size and density of the clump. In the limit of particles perfectly coupled to the gas, the characteristic ratio of gravitational force to gas pressure becomes relevant and defines a two-phase Jeans parameter, J{sub t}, which is the classical Jeans parameter with the speed of sound replaced by an effective wave speed in the coupled two-fluid medium. The parameter J{sub t} remains useful even away from the perfect coupling limit because it makes the simulation results insensitive to the initial density ratio of particles to gas (Φ{sub 0}) as a separate parameter. A simple ordinary differential equation model is developed. It takes the form of two coupled non-linear oscillators and reproduces key features of the simulations. Finally, a parametric study of the time to collapse is performed and a formula (fit to the simulations) is developed. In the incompressible limit J{sub t}→0, collapse time equals the self-sedimentation time, which is inversely proportional to the Stokes number. As J{sub t} increases, the collapse time decreases with J{sub t} and eventually becomes approximately equal to the dynamical time. Values of collapse time versus clump size are given for a minimum-mass solar nebula. Finally, the timescale of clump erosion due to turbulent strain is estimated.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Fundamental research on gas–solid reaction between CO{sub 2} and Li{sub 2}CuO{sub 2} linking application for solid CO{sub 2} absorbent

We compared reactivity between CO{sub 2} and Li{sub 2}CuO{sub 2} with that between CO{sub 2} and Li{sub 4}SiO{sub 4} by using XRD, SEM observation, and thermogravimetry in order to study fundamentally a potential of Li{sub 2}CuO{sub 2} oxide for application to solid CO{sub 2} absorbents. The CO{sub 2} absorption ability of Li{sub 2}CuO{sub 2} was examined by measuring rate constants for the gas–solid reaction between perfectly single-phase Li{sub 2}CuO{sub 2} and CO{sub 2} at various temperatures in 100 vol% CO{sub 2} atmosphere using the rate theory with thermogravimetry using rapid heating. The measured rate constants were compared with those reported previously for Li{sub 4}SiO{sub 4} at various temperatures. Almost no difference was found between these rate constants of Li{sub 2}CuO{sub 2} and Li{sub 4}SiO{sub 4} at temperatures less than 660 °C, but at temperatures higher than 670 °C, the rate constants of Li{sub 2}CuO{sub 2} were greater than those of Li{sub 4}SiO{sub 4}. These results demonstrate that Li{sub 2}CuO{sub 2} can outstrip the ability of Li{sub 4}SiO{sub 4} to absorb CO{sub 2}. Moreover, different from Li{sub 4}SiO{sub 4}, the CO{sub 2} absorption ability of Li{sub 2}CuO{sub 2} decays only slightly, even if the atmospheric CO{sub 2} concentration decreases. -- Graphical abstract: Surface changes of Li{sub 2}CuO{sub 2} and Li{sub 4}SiO{sub 4} particles by progression of the gas–solid reactions between CO{sub 2} and these oxides. Highlights: • The CO{sub 2} absorption ability of perfect single-phase Li{sub 2}CuO{sub 2} is reported. • Results show that Li{sub 2}CuO{sub 2} can outstrip the Li{sub 4}SiO{sub 4} ability to absorb CO{sub 2}. • The oxide particle CO{sub 2} absorption ability is size- and surface-state-dependent.

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

Investigation of high-pressure turbulent jets using direct numerical simulation

Direct numerical simulations of free round jets at a Reynolds number (Re D ) of 5000, based on jet diameter (D) and jet-exit bulk velocity (U e ), are performed to study jet turbulence characteristics at supercritical pressures. The jet consists of nitrogen (N 2 ) that is injected into N 2 at the same temperature. To understand turbulent mixing, a passive scalar is transported with the flow at unity Schmidt number. Two sets of inflow conditions that model jets issuing from either a smooth contraction nozzle (laminar inflow) or a long pipe nozzle (turbulent inflow) are considered. By changing one parameter at a time, the simulations examine the jet-flow sensitivity to the thermodynamic condition (characterized in terms of the compressibility factor ($Z$) and the normalized isothermal compressibility), inflow condition and ambient pressure (p ∞ ) spanning perfect- to real-gas conditions. The inflow affects flow statistics in the near field (containing the potential core closure and the transition region) as well as further downstream (containing fully developed flow with self-similar statistics) at both atmospheric and supercritical p ∞ . The sensitivity to inflow is larger in the transition region, where the laminar-inflow jets exhibit dominant coherent structures that produce higher mean strain rates and higher turbulent kinetic energy than in turbulent-inflow jets. Decreasing $Z$ at a fixed supercritical p ∞ enhances pressure and density fluctuations (non-dimensionalized by local mean pressure and density, respectively), but the effect on velocity fluctuations depends also on the local flow dynamics. When $Z$ is reduced, large mean strain rates in the transition region of laminar-inflow jets significantly enhance velocity fluctuations (non-dimensionalized by local mean velocity) and scalar mixing, whereas the effects are minimal in jets from turbulent inflow.

42 ENGINEERING↗
DOE OSTI2014

Linking the spin evolution of massive black holes to galaxy kinematics

We present the results of a semianalytical model that evolves the masses and spins of massive black holes together with the properties of their host galaxies across the cosmic history. As a consistency check, our model broadly reproduces a number of observations, e.g., the cosmic star formation history; the black hole mass, luminosity, and galaxy mass functions at low redshift; the black hole-bulge mass relation; and the morphological distribution at low redshift. For the first time in a semianalytical investigation, we relax the simplifying assumptions of perfect coherency or perfect isotropy of the gas fueling the black holes. The dynamics of gas is instead linked to the morphological properties of the host galaxies, resulting in different spin distributions for black holes hosted in different galaxy types. We compare our results with the observed sample of spin measurements obtained through broad Kα iron line fitting. The observational data disfavor both accretion along a fixed direction and isotropic fueling. Conversely, when the properties of the accretion flow are anchored to the kinematics of the host galaxy, we obtain a good match between theoretical expectations and observations. A mixture of coherent accretion and phases of activity in which the gas dynamics is similar to that of the stars in bulges (i.e., with a significant velocity dispersion superimposed to a net rotation) best describes the data, adding further evidence in support of the coevolution of massive black holes and their hosts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Non-cratonic Diamonds from UHP Metamorphic Terranes, Ophiolites and Volcanic Sources

The discovery of diamonds in metamorphic rocks of continental affinities occurred shortly after the discovery of coesite in similar rocks. These important discoveries led to a revolution in our understanding of the subduction and exhumation of continental materials and the establishment of a new discipline, ultra-high-pressure metamorphism (UHPM). After these discoveries more ultra-high pressure (UHP) minerals were found and dozens of UHPM terranes were established. Diamond is a remarkable material which is chemically inert and stable over geological timescales making it the perfect “geological container” where gas, fluid, and solid inclusions can be preserved. Moreover, its presence is indicative of specific pressure and temperature conditions which implie subduction to a minimum depth of ~120 km. The inclusions trapped inside these diamonds can shed light on the composition, redox state, and evolution of the fluids related to UHPM diamond formation while the carbon isotope ratios of the diamond itself can inform us about the source of carbon. The purpose of this review is to provide a brief history on the discovery of microdiamonds starting with work that began in the mid-1960s in Kokchetav massif, Kazakhstan, through to the present day. Particular attention will be on more recent micro-diamond discoveries in the last decade. The current state of understating of the mechanisms of UPHM diamond formation, the misidentification of microdiamonds due to contamination from sample extraction/preparation, and the future of UHPM diamond research are discussed. The paper also considers the controversial topic of the occurrence of lonsdaleite within the population of microdiamonds from UHPM terranes as well as recently reported ophiolite- and volcanic-hosted diamonds.

58 GEOSCIENCES↗
DOE OSTI2018

Artificially Structured Semiconductors to Model Novel Quantum Phenomena

Award Period: September 1st, 2013 through February 15th, 2017 Submitted to the USDOE Office of Basic Energy Sciences By Aron Pinczuk and Shalom J. Wind Department of Applied Physics and Applied Mathematics Columbia University New York, NY 10027 January 2017 Award # DE-SC0010695 ABSTRACT Research in this project seeks to design, create and study a class of tunable artificial quantum structures in order to extend the range and scope of new and exciting physical phenomena and to explore the potential for new applications. Advanced nanofabrication was used to create an external potential landscape that acts as a lattice of confinement sites for electrons (and/or holes) in a two-dimensional electron gas in a high perfection semiconductor in such a manner that quantum interactions between different sites dictate the significant physics. Our current focus is on ‘artificial graphene’ (AG) in which a set of quantum dots (or sites) are patterned in a honeycomb lattice. The combination of leading edge nanofabrication with ultra-pure semiconductor materials in this project extends the frontier for small period, low-disorder AG systems, enabling the exploration of graphene physics in a semiconductor platform. TECHNICAL DESCRIPTION Contemporary condensed matter science has entered an era of discovery of new low-dimensional materials, such as graphene and other atomically thin materials, that exhibit exciting new physical phenomena that were previously inaccessible. Concurrent with the discovery and development of these new materials are impressive advancements in nanofabrication, which offer an ever-expanding toolbox for creating a myriad of high quality patterns at nanoscale dimensions. This project started about four years ago. Among its major achievements are the realizations of very small period artificial lattices with honeycomb topology in GaAs quantum wells. In our most recent work the periods of the ‘artificial graphene’ (AG) lattices extend down to 40 nm. These small periods are about three times smaller than previously reported in GaAs quantum wells. This milestone establishes a new state-of-the-art in fields of research and nanofabrication. In experiments using optical scattering methods we uncovered evidence that free electrons in the small period AG lattices display novel features that arise from the symmetry of the honeycomb lattice. These achievements create semiconductor platforms for explorations of novel states and effects that offer opportunities to create quasiparticles with tunable character. The quest for the discovery of novel quantum physics by nanofabrication of ‘artificial structures’ in semiconductor quantum structures overlaps with the development of quantum simulators. Nanopatterns were created at Columbia University by the group of co-PI Shalom Wind using a 100keV e-beam nanolithography instrument (along with associated processing) that is part of the Columbia Nano Initiative. Optical experiments were carried out in the group of PI Aron Pinczuk. GaAs/AlGaAs quantum wells(QWs) of world-class perfection that serve as electron hosts are the starting material grown by molecular beam epitaxy (MBE) by our partners Dr. Loren Pfeiffer (Princeton Univ.) and Prof. Michael Manfra (Purdue Univ.). The inductively coupled plasma reactive ion etching (ICP-RIE) was carried out at the PRISM Micro/Nano Fabrication Laboratory of Princeton University. Dr. Vittorio Pellegrini (Istituto Italiano di Tecnologia, Genoa, Italy) has contributed critical insight on this research. Two graduate students in this project Sheng Wang and Diego Scarabelli, graduated in the summer/fall of 2016. Dr. Yuliya Kuznetsova has been a postdoc in the group. The current work is led by Dr. Lingjie Du, a postdoctoral scientist that joined the group of the PI on October 15th, 2016. Since the start of this project we have focused primarily on developing protocols towards the fabrication of the artificial lattices and in the implementation of characterization methods to identify the new electron states that are created. A major milestone has been the realization of the Dirac cones that emerge in honeycomb lattices. In the next phases of this project, and as we achieve milestones, we wish to expand our experimental platform so that we will be better positioned to access emergent novel quantum behavior and phases of electrons in artificial lattices designed and fabricated with ‘exquisite’ precision. The AG lattices with greatly reduced disorder from nano-processing that we have already created demonstrate that we are poised for the next stage exploration of graphene physics and applications in semiconductor quantum structures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Optimizing Geothermal Drilling: Oil and Gas Technology Transfer

There is a significant amount of financial risk associated with geothermal drilling; however, there are opportunities to improve upon current practices and technologies used. The scope of this drilling operational study included 21 geothermal wells and 21 oil and gas wells. The goal was to determine a 'perfect well' using historical data to compare the best oil and gas well to the best geothermal well. Unfortunately, limitations encountered in the study included missing data (bit records, mud information, etc.), poor data collection, and difficult to ascertain handwriting. An online software database was used to format drilling data to IADC coded daily drilling reports and generate analysis figures. Six major issues have been found in geothermal drilling operations. These problems include lost circulation, rig/equipment selection, cementing, penetration rate, drilling program, and time management. As a result of these issues, geothermal drilling averages 56.4 days longer than drilling comparable oil and gas wells in the wells in this study. Roughly $13.9 million would be lost due to non-productive time in the 21 geothermal wells and only $1.3 million in the oil and gas wells, assuming a cost of $50,000 per day. Comparable events such as drilling the same sized hole, tripping in/out, cementing, and running the same size casing took substantially less time in the oil and gas wells. Geothermal wells were drilled using older and/or less advanced technology to depths less than 10,000 feet, while oil and gas wells reached 12,500 feet faster with purpose built rigs. A new approach is now underway that will optimize drilling programs throughout the drilling industry. It is the use of Mechanical Specific Energy (MSE) as a tool to realize efficient drilling processes. However, a work-flow must also be established in order for there to be an efficient drilling program. Potential improvements for current geothermal operations are: the use of electronic records, real time services, and official glossary terms to describe rig operations, and advanced drilling rigs/technology.

15 GEOTHERMAL ENERGY↗
DOE OSTI2020

An Uncertainty Management Framework for Integrated Gas-Electric Energy Systems

In many parts of the world, electric power systems have seen a significant shift toward generation from renewable energy and natural gas. Because of their ability to flexibly adjust power generation in real time, gas-fired power plants are frequently seen as the perfect partner for variable renewable generation. However, this reliance on gas generation increases interdependence and propagates uncertainty between power grids and gas pipelines and brings coordination and uncertainty management challenges. To address these issues, we propose an uncertainty management framework for uncertain, but bounded gas consumption by gas-fired power plants. The admissible ranges are computed based on a joint optimization problem for the combined gas and electricity networks, which involves chance-constrained scheduling for the electric grid and a novel robust optimization formulation for the natural-gas network. This formulation ensures feasibility of the integrated system with a high probability, while providing a tractable numerical formulation. A key advance with respect to existing methods is that our method is based on a physically accurate, validated model for transient gas pipeline flows. Our case study benchmarks our proposed formulation against methods that ignore how reserve activation impacts the fuel use of gas power plants and only consider predetermined gas consumption. Here, the results demonstrate the importance of considering uncertainty to avoid operating constraint violations and curtailment of gas to the generators.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Nonequilibrium Entropy in a Shock

In a classic paper, Morduchow and Libby use an analytic solution for the profile of a Navier–Stokes shock to show that the equilibrium thermodynamic entropy has a maximum inside the shock. There is no general nonequilibrium thermodynamic formulation of entropy; the extension of equilibrium theory to nonequililbrium processes is usually made through the assumption of local thermodynamic equilibrium (LTE). However, gas kinetic theory provides a perfectly general formulation of a nonequilibrium entropy in terms of the probability distribution function (PDF) solutions of the Boltzmann equation. In this paper I will evaluate the Boltzmann entropy for the PDF that underlies the Navier–Stokes equations and also for the PDF of the Mott–Smith shock solution. I will show that both monotonically increase in the shock. As a result, I will propose a new nonequilibrium thermodynamic entropy and show that it is also monotone and closely approximates the Boltzmann entropy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

MASS ACCRETION AND ITS EFFECTS ON THE SELF-SIMILARITY OF GAS PROFILES IN THE OUTSKIRTS OF GALAXY CLUSTERS

Galaxy clusters exhibit remarkable self-similar behavior which allows us to establish simple scaling relationships between observable quantities and cluster masses, making galaxy clusters useful cosmological probes. Recent X-ray observations suggested that self-similarity may be broken in the outskirts of galaxy clusters. In this work, we analyze a mass-limited sample of massive galaxy clusters from the Omega500 cosmological hydrodynamic simulation to investigate the self-similarity of the diffuse X-ray emitting intracluster medium (ICM) in the outskirts of galaxy clusters. We find that the self-similarity of the outer ICM profiles is better preserved if they are normalized with respect to the mean density of the universe, while the inner profiles are more self-similar when normalized using the critical density. However, the outer ICM profiles as well as the location of accretion shock around clusters are sensitive to their mass accretion rate, which causes the apparent breaking of self-similarity in cluster outskirts. We also find that the collisional gas does not follow the distribution of collisionless dark matter (DM) perfectly in the infall regions of galaxy clusters, leading to 10% departures in the gas-to-DM density ratio from the cosmic mean value. Our results have a number implications for interpreting observations of galaxy clusters in X-ray and through the Sunyaev–Zel’dovich effect, and their applications to cosmology.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

SWIFT - Shaped-Waveform Interrogation of Fluids Technique

Researchers at Los Alamos have developed the Shaped-Waveform Interrogation of Fluids Technique (SWIFT), a technology enabling unprecedented process control capability. This technology provides important composition, flow rate, and pipe thickness measurements in real-time, at an extremely low cost and maintenance cycle. By utilizing a specialized shaped-waveform, as well as state-of-the-art signal processing, this information can be gathered without any frequency-domain signal processing, allowing for simplified electronics compared to nearly any other meter on the market. Since this technology is in expensive and non-invasive, with the capability of measuring liquids in both flow pipes and sealed containers, it is perfect for several industrial applications in the oil and gas, beverage, chemical, and pharmaceutical spaces. We are seeking a commercialization partner to license the technology or fund us through a Cooperative Research and Development Agreement (CRADA) to a further develop a usable product for commercial purposes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Computational Investigation on Hydrodeoxygenation (HDO) of Acetone to Propylene on α-MoO 3 (010) Surface

Density functional theory (DFT) calculations were performed on the multistep hydrodeoxygenation (HDO) of acetone (CH 3 COCH 3 ) to propylene (CH 3 CHCH 2 ) on a molybdenum oxide (α-MoO 3 ) catalyst following an oxygen vacancy-driven pathway. First, a perfect O-terminated α-MoO 3 (010) surface based on a 4 × 2 × 4 supercell is reduced by molecular hydrogen (H 2 ) to generate a terminal oxygen (O t ) defect site. This process occurs via a dissociative chemisorption of H 2 on adjacent surface oxygen atoms, followed by an H transfer to form a water molecule (H 2 O). Next, adsorption of CH 3 COCH 3 on the oxygen-deficient Mo site forms an O–Mo bond and then the chemisorbed CH 3 COCH 3 forms CH 3 COCH 2 by transfer of an H atom to an adjacent O t site. The surface bound hydroxyl (OH) then transfers the H atom to the immobilized O atom to form surface-bound enol, CH 3 CHOCH 2 . The next step releases CH 3 CHCH 2 into the gas phase, while simultaneously oxidizes the surface back to a perfect O-terminated α-MoO 3 (010) surface. The adsorption of H 2 , and the formation of a terminal oxygen (Ot) vacancy, moves the conduction band minimum (CBM) from 1.2 eV to 0 and 0.3 eV, respectively. Climbing image-nudged elastic band (CI-NEB) calculations using a Perdew–Burke–Ernzerhof (PBE) functional in combination with double-ζ valence (DZV) basis sets indicate that the dissociative adsorption of H 2 is the rate-limiting step for the catalytic cycle with a barrier of 1.70 eV. Furthermore, the lower barrier for surface-mediated H transfer from primary-to-secondary carbon atom (0.63 eV) compared to that of a concerted direct H transfer to the secondary C atom with simultaneous desorption (2.02 eV) emphasizes the key role played by the surface in H transfer for effective deoxygenation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

A facile in-situ etching route to hollow C@SnO2 nanocomposites and their gas-sensing properties

Highlights: • Hollow C@SnO{sub 2} nanostructure has been designed via a facile in-situ etching technique.. • The C@SnO{sub 2} products possess a high surface are and a hollow carbon core. • The growth of SnO{sub 2} nanosheets and the removal of silica template can be synchronously performed. • The C@SnO{sub 2} products manifest highly sensitive and selective to n-butanol as gas-sensing sensor. - Abstract: A novel hollow carbon@SnO{sub 2} nanocomposite has been developed via a high cost-effective and facile in-situ etching technique. The as-prepared C@SnO{sub 2} product has a high surface area of about 115 m{sup 2} g{sup −1} and a hollow carbon core, where a lot of SnO{sub 2} nanosheets grow onto the carbon shell. Particularly, the silica core as the sacrificial template can be fully removed by hydrofluoric acid (HF) byproduct during the reaction process. Moreover, the deposition of SnO{sub 2} sheets and the removal of the silica template can be synchronously performed by a simple one-step process. When applied as the gas-sensing material, the C@SnO{sub 2} product manifests highly sensitive and selective to n-butanol. The large surface area, hollow nanostructure and the perfect combination of SnO{sub 2} nanosheets and carbon layer contribute to the enhanced gas-sensing performances. The method described in our work can also be employed to design other hollow metal oxides@carbon hybrids for energy storage and catalysis.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Disformal invariance of continuous media with linear equation of state

We show that the effective theory describing single component continuous media with a linear and constant equation of state of the form p = w ρ is invariant under a 1-parameter family of continuous disformal transformations. In the special case of w =1/3 (ultrarelativistic gas), such a family reduces to conformal transformations. As examples, perfect fluids, irrotational dust (mimetic matter) and homogeneous and isotropic solids are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗