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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 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Bimolecular reaction of CH{sub 3} + CO in solid p-H{sub 2}: Infrared absorption of acetyl radical (CH{sub 3}CO) and CH{sub 3}-CO complex

We have recorded infrared spectra of acetyl radical (CH{sub 3}CO) and CH{sub 3}-CO complex in solid para-hydrogen (p-H{sub 2}). Upon irradiation at 248 nm of CH{sub 3}C(O)Cl/p-H{sub 2} matrices, CH{sub 3}CO was identified as the major product; characteristic intense IR absorption features at 2990.3 (ν{sub 9}), 2989.1 (ν{sub 1}), 2915.6 (ν{sub 2}), 1880.5 (ν{sub 3}), 1419.9 (ν{sub 10}), 1323.2 (ν{sub 5}), 836.6 (ν{sub 7}), and 468.1 (ν{sub 8}) cm{sup −1} were observed. When CD{sub 3}C(O)Cl was used, lines of CD{sub 3}CO at 2246.2 (ν{sub 9}), 2244.0 (ν{sub 1}), 1866.1 (ν{sub 3}), 1046.7 (ν{sub 5}), 1029.7 (ν{sub 4}), 1027.5 (ν{sub 10}), 889.1 (ν{sub 6}), and 723.8 (ν{sub 7}) cm{sup −1} appeared. Previous studies characterized only three vibrational modes of CH{sub 3}CO and one mode of CD{sub 3}CO in solid Ar. In contrast, upon photolysis of a CH{sub 3}I/CO/p-H{sub 2} matrix with light at 248 nm and subsequent annealing at 5.1 K before re-cooling to 3.2 K, the CH{sub 3}-CO complex was observed with characteristic IR features at 3165.7, 3164.5, 2150.1, 1397.6, 1396.4, and 613.0 cm{sup −1}. The assignments are based on photolytic behavior, observed deuterium isotopic shifts, and a comparison of observed vibrational wavenumbers and relative IR intensities with those predicted with quantum-chemical calculations. This work clearly indicates that CH{sub 3}CO can be readily produced from photolysis of CH{sub 3}C(O)Cl because of the diminished cage effect in solid p-H{sub 2} but not from the reaction of CH{sub 3} + CO because of the reaction barrier. Even though CH{sub 3} has nascent kinetic energy greater than 87 kJ mol{sup −1} and internal energy ∼42 kJ mol{sup −1} upon photodissociation of CH{sub 3}I at 248 nm, its energy was rapidly quenched so that it was unable to overcome the barrier height of ∼27 kJ mol{sup −1} for the formation of CH{sub 3}CO from the CH{sub 3} + CO reaction; a barrierless channel for formation of a CH{sub 3}-CO complex was observed instead. This rapid quenching poses a limitation in production of free radicals via bimolecular reactions in p-H{sub 2}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Design of interferometer system for Keda Torus eXperiment using terahertz solid-state diode sources

A solid-state source based terahertz (THz) interferometer diagnostic system has been designed and characterized for the Keda Torus eXperiment (KTX). The THz interferometer utilizes the planar diodes based frequency multiplier (X48) to provide the probing beam at fixed frequency 0.650 THz, and local oscillator is provided by an independent solid-state diode source with tunable frequency (0.650 THz +/− 10 MHz). Both solid-state sources have approximately 1 mW power. The planar-diode mixers optimized for high sensitivity, ∼750 mV/mW, are used in the heterodyne detection system, which permits multichannel interferometer on KTX with a low phase noise. A sensitivity of {sub min} = 4.5 × 10{sup 16} m{sup −2} and a temporal resolution of 0.2 μs have been achieved during the initial bench test.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Simultaneous probing of bulk liquid phase and catalytic gas-liquid-solid interface under working conditions using attenuated total reflection infrared spectroscopy

Design and performance of a reactor set-up for attenuated total reflection infrared (ATR-IR) spectroscopy suitable for simultaneous reaction monitoring of bulk liquid and catalytic solid-liquid-gas interfaces under working conditions are presented. As advancement of in situ spectroscopy an operando methodology for gas-liquid-solid reaction monitoring was developed that simultaneously combines catalytic activity and molecular level detection at the catalytically active site of the same sample. Semi-batch reactor conditions are achieved with the analytical set-up by implementing the ATR-IR flow-through cell in a recycle reactor system and integrating a specifically designed gas feeding system coupled with a bubble trap. By the use of only one spectrometer the design of the new ATR-IR reactor cell allows for simultaneous detection of the bulk liquid and the catalytic interface during the working reaction. Holding two internal reflection elements (IRE) the sample compartments of the horizontally movable cell are consecutively flushed with reaction solution and pneumatically actuated, rapid switching of the cell (<1 s) enables to quasi simultaneously follow the heterogeneously catalysed reaction at the catalytic interface on a catalyst-coated IRE and in the bulk liquid on a blank IRE. For a complex heterogeneous reaction, the asymmetric hydrogenation of 2,2,2-trifluoroacetophenone on chirally modified Pt catalyst the elucidation of catalytic activity/enantioselectivity coupled with simultaneous monitoring of the catalytic solid-liquid-gas interface is shown. Both catalytic activity and enantioselectivity are strongly dependent on the experimental conditions. The opportunity to gain improved understanding by coupling measurements of catalytic performance and spectroscopic detection is presented. In addition, the applicability of modulation excitation spectroscopy and phase-sensitive detection are demonstrated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Local polar structure and multiferroic properties of (1−x)Bi{sub 0.9}Dy{sub 0.1}FeO{sub 3}−xPbTiO{sub 3} solid solution

The multiferroic (1–x)[0.9BiFeO{sub 3}–0.1DyFeO{sub 3}]–xPbTiO{sub 3} (BDF–xPT) solid solution with compositions around the morphotropic phase boundary (x = 0.25, 0.28, 0.31, 0.34, and 0.37) has been synthesized in the form of ceramics. The phase symmetry, microstructure, ferroelectricity, piezoresponse, and ferromagnetic properties have been characterized by various techniques. It is found that, with increasing content of lead titanate from x = 0.25 to x = 0.37, the grain size increases and the ferroelectric property is improved. The ferroelectric performance is further enhanced by the introduction of an excess amount (2%) of TiO{sub 2} or by sintering in oxygen atmosphere, which reduces the leakage. The local polar structure is imaged by piezoresponse force microscopy. Both the out-of-plane and in-plane images reveal distinct ferroelectric domain structures, with the amplitude and the average domain size decreasing with the increase of lead titanate amount. Compared with the (1–x)BiFeO{sub 3}–xPbTiO{sub 3} binary solid solution of about the same concentration of PT, the magnetic properties are enhanced in BDF–xPT due to the presence of dysprosium, as demonstrated by the ferromagnetic hysteresis loops displayed at room temperature and at 10 K, but the remnant magnetization decreases with increasing PT content. The simultaneous presence of ferroelectricity and ferromagnetism entitles the BDF–xPT solid solution a room-temperature multiferroic material.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method

The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Influence of the electron-phonon interaction on the temperature dependence of the phonon mode frequency in the II-VI compound solid solutions

We present an experimental investigation of the temperature dependence of the TO-phonon mode frequencies for the HgTe-based II-VI semiconductor solid solutions. In the case of the ternary Hg{sub 0.9}Zn{sub 0.1}Te solid solution was shown a discontinuity in the temperature dependence of the HgTe-like T{sub 0}-mode and of the ZnTe-like T{sub 1}-mode, similar to the Hg{sub 0.85}Cd{sub 0.15}Te system [Sheregii et al., Phys. Rev. Lett. 102, 045504 (2009)]. A generalization of the theoretical temperature shift of the phonon mode frequency as analytic equation is derived that includes both the anharmonic contribution and the electron-phonon e-p interaction which in this case is returnable—the electron subsystem effect on the phonon one. Data show that our equation satisfactorily describes the temperature shift of both Hg{sub 0.85}Cd{sub 0.15}Te and Hg{sub 0.90}Zn{sub 0.10}Te containing Dirac point (E{sub g} ≡ Γ{sub 6} – Γ{sub 8} = 0) although one of the two constants describing the anharmonic shift of the HgTe-like mode should be positive what is abnormal too. In the case of the Hg{sub 0.80}Cd{sub 0.20}Te and Hg{sub 0.763}Zn{sub 0.237}Te solid solution, the role of the returnable e-p contribution is negligible but a positive temperature shift for the HgTe-like modes occurs. This result does not allow to explain the positive temperature shift of these modes merely by the contribution of the (e-p) interaction. Indeed, the relativistic contribution to the chemical bonds induces an abnormal temperature shift of the electron states in Hg-based semiconductors—the effect is expected since the Hg d spin-orbit split contribution to chemical bonds may lead to an abnormal temperature shift of the HgTe-like modes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Phenomena of solid state grain boundaries phase transition in technology

The results of study the phenomenon, discovered by author (1971), of the phase transition of grain boundary by the formation of two-dimensional liquid or quasi-liquid films have been done. The described phenomena of the first order phase transition (two-dimensional melting) at temperatures 0.6 – 0.9 T{sub S0} (of the solid state melting point) is a fundamental property of solid crystalline materials, which has allowed to revise radically scientific representations about a solid state of substance. Using the mathematical tools of the film thermodynamics it has been obtained the generalized equation of Clausius - Clapeyron type for two-dimensional phase transition. The generalized equation has been used for calculating grain boundary phase transition temperature T{sub Sf} of any metal, which value lies in the range of (0.55…0.86) T{sub S0}. Based on these works conclusions the develop strategies for effective forming of coatings (by thermo-chemical processing) on surface layers of functional alloys and hard metals have been made. The short overview of the results of some graded alloys characterization has been done.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

A scheme for a single molecule phase-shift gate in a solid matrix

We propose a feasible scheme to implement a phase-shift gate ( (table) ) based on a two-state single molecule in a solid matrix, where γ is a geometric phase controlled through a fast on-resonant laser field and a slow off-resonant radio-frequency field. In our scheme, a non-Hermitian quantum model is employed to characterize the single molecule in a solid matrix including the spontaneous decay effect. By the coupling between the radio-frequency field and the two-state permanent dipole difference resulting from the solid matrix, the spontaneous decay fatal to the preservation of geometric phase can be effectively suppressed for a considerably long waiting time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Dense electron-positron plasmas and gamma-ray bursts generation by counter-propagating quantum electrodynamics-strong laser interaction with solid targets

We use quantum electrodynamics (QED) particle-in-cell simulations to investigate and compare the generation of dense electron-positron plasmas and intense γ-ray bursts in the case of counter-propagating laser solid interaction (two-side irradiation) and single laser solid interaction (one-side irradiation). In the case of counter-propagating linearly polarized laser pulses irradiating a thin aluminum foil with each pulse peak power of 12.5 PW (I = 4 × 10{sup 23 }W/cm{sup 2}), we calculate that about 20% of the laser energy is converted into a burst of γ-rays with flux exceeding 10{sup 14 }s.{sup −1} This would be one of the most intense γ-ray sources among those currently available in laboratories. The γ-ray conversion efficiency in the case of two-side irradiation is three times higher than in the case of one-side irradiation using a single 12.5 PW laser. Dense electron-positron plasma with a maximum density of 6 × 10{sup 27 }m{sup −3} are generated simultaneously during the two-side irradiation which is eightfold denser compared to the one-side irradiation. The enhancement of the effects in the case of counter-propagating lasers are the results of the symmetrical compression of the foil target and the formation of electric potential and standing wave around the target. Realizing experimentally the proposed counter-propagating QED-strong laser-solid interaction to produce dense electron-positron pairs and prolific γ-rays will be made possible by the Extreme Light Infrastructure-Nuclear Physics facility under construction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Coupling an electrospray source and a solids probe/chemical ionization source to a selected ion flow tube apparatus

A new ion source region has been constructed and attached to a variable temperature selected ion flow tube. The source features the capabilities of electron impact, chemical ionization, a solids probe, and electrospray ionization. The performance of the instrument is demonstrated through a series of reactions from ions created in each of the new source regions. The chemical ionization source is able to create H{sub 3}O{sup +}, but not as efficiently as similar sources with larger apertures. The ability of this source to support a solids probe, however, greatly expands our capabilities. A variety of rhenium cations and dications are created from the solids probe in sufficient abundance to study in the flow tube. The reaction of Re{sup +} with O{sub 2} proceeds with a rate constant that agrees with the literature measurements, while the reaction of Re{sub 2}{sup 2+} is found to charge transfer with O{sub 2} at about 60% of the collision rate; we have also performed calculations that support the charge transfer pathway. The electrospray source is used to create Ba{sup +}, which is reacted with N{sub 2}O to create BaO{sup +}, and we find a rate constant that agrees with the literature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Hydrogen diffusion and segregation during solid phase epitaxial regrowth of preamorphized Si

The redistribution of hydrogen during solid phase epitaxial regrowth (SPER) of preamorphized silicon has been experimentally investigated, modeled, and simulated for different H concentrations and temperatures. H was introduced by H implantation and/or infiltration from the sample surface during partial thermal anneals in air in the 520–620 °C temperature range. We characterized the time evolution of the H redistribution by secondary ion mass spectrometry and time resolved reflectivity. The good agreement between all experimental data and the simulations by means of full rate equation numerical calculations allows the quantitative assessment of all the phenomena involved: in-diffusion from annealing atmosphere and the H effect on the SPER rate. We describe the temperature dependence of microscopic segregation of H at the amorphous/crystal (a-c) interface. Only a fraction of H atoms pushed by the a-c interface can be incorporated into the crystal bulk. We propose an energetic scheme of H redistribution in amorphous Si. The segregation of H at the a-c interface is also considered for (110) and (111) orientated substrates. Our description can also be applied to other material systems in which redistribution of impurities during a solid-solid phase transition occurs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Ion beam irradiation as a tool to improve the ionic conductivity in solid polymer electrolyte systems

Solid polymer electrolytes (SPEs) have potential applications in solid state electronic and energy devices. The optimum conductivity of SPEs required for such applications is about 10{sup −1} – 10{sup −3} Scm{sup −1}, which is hard to achieve in these systems. It is observed that ionic conductivity of SPEs continuously increase with increasing concentration of inorganic salt in the host polymer. However, there is a critical concentration of the salt beyond which the conductivity of SPEs decreases due to the formation of ion pairs. In the present study, solid polymer thin films based on poly (ethylene oxide) (PEO) complexed with NaBr salt with different concentrations have been prepared and the concentration at which ion pair formation occurs in PEO{sub x}NaBr is identified. The microstructure of the SPE with highest ionic conductivity is modified by irradiating it with low energy O{sup +1} ion (100 keV) of different fluencies. It is observed that the ionic conductivity of irradiated SPEs increases by one order in magnitude. The increase in ionic conductivity may be attributed to the enhanced segmental motion of the polymer chains due to radiation induced micro structural modification.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Synthesis and photoluminescence properties of LiSrPO{sub 4}:Eu{sup 2+} phosphor for solid state lighting

A novel method to prepare orthophosphate LiSrPO{sub 4}: Eu{sup 2+} phosphor for white light-emitting diodes (w-LEDs) is given in this paper. Phosphor was successfully synthesized by Pechini (citrate gel) method which is efficient than conventional high temperature solid state reaction. X-ray powder diffraction (XRD) analysis confirmed the single phase formation of LiSrPO{sub 4}:Eu{sup 2+} with monoclinic crystal structure. Luminescence results showed that the phosphor could be efficiently excited by near UV and exhibited bright blue emission at λ{sub em} = 420 nm corresponding to 5d– 4f transition of Eu{sup 2+}. The phosphor exhibits blue emission bands under 350 nm excitation. This mercury-free excitation is useful for solid state lighting and light-emitting diode (LED). Hence it could be useful for solid state lighting and light-emitting diode (LED) application.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Lithium substitution in strontium chlorapatite studied by solid state NMR spectroscopy

Strontium Chlorapatites with various amounts of Li substitution (Sr{sub 10-x}Li{sub x}(PO{sub 4}){sub 6}Cl{sub 2-δ}) were prepared by solid state reaction method and characterized by powder XRD and solid state NMR spectroscopy. XRD reveals shortening of lattice parameters upon Li incorporation. The linewidth of {sup 31}P solid state Magic Angle Spinning NMR spectra decreases with increase in Li content within the apatite phase. This study confirms Li uptake within the apatite phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Understanding band gaps of solids in generalized Kohn–Sham theory

The fundamental energy gap of a periodic solid distinguishes insulators from metals and characterizes low-energy single-electron excitations. However, the gap in the band structure of the exact multiplicative Kohn–Sham (KS) potential substantially underestimates the fundamental gap, a major limitation of KS density-functional theory. Here, we give a simple proof of a theorem: In generalized KS theory (GKS), the band gap of an extended system equals the fundamental gap for the approximate functional if the GKS potential operator is continuous and the density change is delocalized when an electron or hole is added. Our theorem explains how GKS band gaps from metageneralized gradient approximations (meta-GGAs) and hybrid functionals can be more realistic than those from GGAs or even from the exact KS potential. The theorem also follows from earlier work. The band edges in the GKS one-electron spectrum are also related to measurable energies. Finally, a linear chain of hydrogen molecules, solid aluminum arsenide, and solid argon provide numerical illustrations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

HIGH-TEMPERATURE PROCESSING OF SOLIDS THROUGH SOLAR NEBULAR BOW SHOCKS: 3D RADIATION HYDRODYNAMICS SIMULATIONS WITH PARTICLES

A fundamental, unsolved problem in solar system formation is explaining the melting and crystallization of chondrules found in chondritic meteorites. Theoretical models of chondrule melting in nebular shocks have been shown to be consistent with many aspects of thermal histories inferred for chondrules from laboratory experiments; but, the mechanism driving these shocks is unknown. Planetesimals and planetary embryos on eccentric orbits can produce bow shocks as they move supersonically through the disk gas, and are one possible source of chondrule-melting shocks. We investigate chondrule formation in bow shocks around planetoids through three-dimensional radiation hydrodynamics simulations. A new radiation transport algorithm that combines elements of flux-limited diffusion and Monte Carlo methods is used to capture the complexity of radiative transport around bow shocks. An equation of state that includes the rotational, vibrational, and dissociation modes of H{sub 2} is also used. Solids are followed directly in the simulations and their thermal histories are recorded. Adiabatic expansion creates rapid cooling of the gas, and tail shocks behind the embryo can cause secondary heating events. Radiative transport is efficient, and bow shocks around planetoids can have luminosities ∼few× 10{sup –8} L{sub ☉}. While barred and radial chondrule textures could be produced in the radiative shocks explored here, porphyritic chondrules may only be possible in the adiabatic limit. We present a series of predicted cooling curves that merit investigation in laboratory experiments to determine whether the solids produced by bow shocks are represented in the meteoritic record by chondrules or other solids.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Platonic solids back in the sky: icosahedral inflation

We generalize the model of solid inflation to an anisotropic cosmic solid. Barring fine tunings, the observed isotropy of the cosmological background and of the scalar two-point function isolate the icosahedral group as the only possible symmetry group of such a solid. In such a case, higher-point correlation functions—starting with the three-point one—are naturally maximally anisotropic, which makes the standard detection strategies highly inefficient and calls for a dedicated analysis of CMB data. The tensor two-point function can also be highly anisotropic, but only in the presence of sizable higher-derivative couplings.

79 ASTRONOMY AND ASTROPHYSICS↗