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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Application of IR Thermography with Thermal Diffusivity Analysis for Detection of Plies Displacement in CFRP Composites

This paper presents an efficient nondestructive testing (NDT) method for detection of plies displacement in carbon fiber reinforced plastic (CFRP) composites using the active thermography technique. To assess the capability of the proposed technique for detection of plies displacement, the CFRP composite specimens with simulated fault were designed and manufactured. The IR thermography measurements were conducted using two-sided experimental arrangement. From recorded sequences of thermal images, the temperature variations versus time plots were extracted to obtain the maximum thermal contrasts. For quantitative interpretation of the results, the thermal diffusivity values for each composite material were determined and related to the fiber volume fraction. The experimental results showed that the thermal diffusivity increases with an increase of fiber volume fraction; further, the values of thermal diffusivity are specimen thickness dependent. The obtained values of thermal diffusivity varied from 1.5 × 10{sup −7} m{sup 2}/s (for 3.2 mm composite with 8.5 vol.% carbon fiber) to 2.6 × 10{sup −7} m{sup 2}/s (for 7.7 mm composite with 34.1 vol.% carbon fiber). On the basis of these results, it was concluded that the active thermography combined with thermal diffusivity analysis can be considered as a reliable NDT technique for detection of plies displacement in CFRP composites.

36 MATERIALS SCIENCE↗
DOE OSTI2017

IR-MALDESI Mass Spectrometry Imaging at 50 Micron Spatial Resolution

High spatial resolution in mass spectrometry imaging (MSI) is crucial to understanding the biology dictated by molecular distributions in complex tissue systems. Here, we present MSI using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) at 50 μm resolution. An adjustable iris, beam expander, and an aspherical focusing lens were used to reduce tissue ablation diameters for MSI at high resolution. The laser beam caustic was modeled using laser ablation paper to calculate relevant laser beam characteristics. The minimum laser spot diameter on the tissue was determined using tissue staining and microscopy. Finally, the newly constructed optical system was used to image hen ovarian tissue with and without oversampling, detailing tissue features at 50 μm resolution. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Experimental study of single-electron detachment for Cu{sup −}, Ag{sup −}, Au{sup −}, Co{sup −}, and Ir{sup −} in collisions with Kr and Xe

The single electron detachment (SED) cross sections for Cu{sup −}, Ag{sup −}, Au{sup −}, Co{sup −}, and Ir{sup −} in collisions with Kr and Xe in the energy range of 10keV≤E≤30keV are measured by using the growth rate method in our experiments. The SED cross sections increase as the incident velocity increases. These data are compared with other available experimental data for the corresponding negative ions colliding with Ar. The affinities of the negative ions and the mass relation between the projectile and the target seem important in the electron detachment process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

The fourth spectrum of iridium (Ir IV)

The spectrum of three times ionized iridium, Ir IV, was investigated in the 650–2045 Å wavelength region. The analysis has led to the determination of the 5d{sup 6}, 5d{sup 5}6s and 5d{sup 5}6p configurations. Twenty-nine of 34 theoretically possible 5d{sup 6} levels, 44 of 74 possible 5d{sup 5}6s levels and 150 of 214 possible 5d{sup 5}6p levels have been established. The levels are based on 1348 classified spectral lines. The level structure and transition probabilities were calculated using the orthogonal operators technique. The energy parameters have been determined by the least squares fit to the observed levels. Calculated energy values and LS-compositions obtained from the fitted parameter values are given. The level optimization procedure and the determination of uncertainties of the obtained energy level values are discussed.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Double layer effects in electrocatalysis: The oxygen reduction reaction and ethanol oxidation reaction on Au(111), Pt(111) and Ir(111) in alkaline media containing Na and Li cations

Oxygen reduction and ethanol oxidation reactions were studied on Au(111), Pt(111) and Ir(111) in alkaline solutions containing sodium and/or lithium cations. By keeping the same (111) surface orientation and exploring oxophilicity trends and non-covalent interactions between OH ad and alkali metal cations (AMC n+ ), we were able to gain deep insights into the multiple roles that OH ad plays in these important electrocatalytic reactions. Cyclic voltammetry experiments revealed that OH ad formation initiates at distinct electrode potentials, governed by the oxophilicity of the specific metal surface, with further OH ad adlayer stabilization by non-covalent alkali-cation interactions and affecting the formation of a “true oxide” layer at higher electrode potentials. Although OH ad is a simple spectator for the ORR, it promotes the ethanol oxidation reaction (EOR) at lower potentials and act as spectator at high OHad coverages. By changing the alkali metal cation at the interface (Li + ) on more oxophilic surfaces, it was possible to promote the EOR even more, relative to Na + , without changing the product distribution for the reaction. This cation effect suggests that OH ad —Li + (H 2 O) x clusters can stabilize the ethoxide adlayer, thus improving the EOR activity. Finally, our results indicate the importance of the entire electrochemical interface in determining the electrocatalytic activity during reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Surface intermediates identified using IR spectroscopy during the catalytic oxidation of C 2 H 6 on IrO 2 (1 1 0) at near-ambient pressures

Characterizing surface intermediates during catalysis is essential for developing mechanistic models of catalytic reactions and for identifying rate-controlling steps. Here, in this work, we used polarization-dependent reflection absorption infrared spectroscopy (PD-RAIRS) to investigate surface intermediates that form on IrO 2 (1 1 0) during the catalytic oxidation of C 2 H 6 at pressures near 0.5 Torr. Our results show that adsorbed CO and HCO 2 are the only intermediates detectable with PD-RAIRS across a wide range of temperatures and reactant compositions during complete C 2 H 6 oxidation, giving rise to dominant peaks at about 2093 and 1310 cm −1 , respectively. These assignments were corroborated by RAIRS measurements following CO and HCOOH adsorption in ultrahigh vacuum, RAIRS with C 2 H 6 – 18 O 2 mixtures during catalysis and vibrational frequencies and IR intensities computed using density functional theory. We find that increasing the C 2 H 6 mole fraction in the reaction mixture raises the CO surface coverage relative to HCO 2 , correlating with increasing catalytic oxidation rates. The formation of CO and HCO 2 surface species at temperatures well below catalytic ignition indicates that the overall rate of C 2 H 6 oxidation on IrO 2 (1 1 0) is governed by steps late in the reaction sequence, such as H 2 O formation, CO oxidation and HCO 2 dehydrogenation. These findings provide key insight into the mechanism of alkane oxidation on IrO 2 (1 1 0) and valuable input for first-principles microkinetic modeling.

Pope, Connor [Univ. of Florida, Gainesville, FL (U↗
DOE OSTI2017

An in-situ electrochemical IR investigation of solution CO electro-oxidation on a polycrystalline Au surface in an alkaline electrolyte: Identification of active reaction intermediates

Here we report an in-situ electrochemical surface enhanced IR reflection absorption spectroscopic (SEIRAS) study of carbon monoxide electro-oxidation reaction (COR) of CO dissolved in alkaline supporting electrolyte (CO sol ). With judiciously chosen concentration of OH - , we were able to observe for the first time the vibrational band of the weakly adsorbed CO w in an alkaline solution and identify it as the active reaction intermediate for the COR of CO sol , as in the acidic media. With the help of deuterium labeling, we were also able to confirm spectroscopically, again for the first time, the previously proposed CO-adsorption-promoted-OH-adsorption hypothesis. We proposed a reaction mechanism accordingly that consists of (1) CO-adsorption-promoted OH adsorption, (2) formation of weakly-bound CO w from CO sol , and (3) the oxidation of CO w by a surface-anchored weakly-hydrogen-bound species. We believe that the synergistic actions of these elemental chemical processes are the reasons for the observed unusually high activity of COR of CO sol in an alkaline solution.

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

A New Simultaneous Membrane Thickness and Catalyst Loading Measurement for Fuel Cell Proton-Exchange Assemblies by $\mathrm{IR}$ Transmission

Here, we present a study of mid-infrared (mid-IR) transmission through typical proton-exchange fuel cell and water electrolyzer catalyst-coated membrane materials, and the determination of membrane layer thickness, and catalyst layer loading, from the power of the transmitted beam. Measured membrane thicknesses lay in the range of 25-125 um, and catalyst areal loadings range from 0.05 to 0.35 mg/cm 2 . We show that the transmission spectrum correlated to membrane thickness and catalyst loading values separately, and also used a mathematical model to calculate both quantities simultaneously, from a single measurement of transmission. Measurements were carried out using a Fourier-transform infrared (FTIR) spectrometer, in specular transmission mode, in the wavelength range of 3-13 um (3333-770 cm -1 ). We discuss the potential application of this method to the development of roll-to-roll manufacturing full-area-scanning quality inspection of catalyst-coated membrane (CCM) materials.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2017

High-pressure behavior of α-boron studied on single crystals by X-ray diffraction, Raman and IR spectroscopy

In the present study single crystals of rhombohedral α-B were investigated under pressure to 60 GPa by means of single-crystal X-ray diffraction. The bulk modulus of α-B was found to be K=224(7) GPa (K′=3.0(3)). Measurements of interatomic distances as a function of pressure revealed that the intericosahedral two-center two-electron (2c–2e) bonds are almost as stiff as some of intraicosahedral ones. The three-center two-electron (3c–2e) intericosahedral bonds show much higher compliance compared to other bonds in α-B. The vibrational properties of α-B under pressure were investigated by Raman spectroscopy at pressures up to 160 GPa and IR spectroscopy at pressures up to 53 GPa. - Graphical abstract: The rhombohedral α-B is highly incompressible and extremely stable: it maintains its crystal structure up to 160 GPa and its intericosahedral 2e2c bonds are almost as stiff as some of intraicosahedral ones. - Highlights: • Structural stability of α-B has been investigated up to 160 GPa on single crystals. • Single-crystal x-ray diffraction reveals that α-B is highly incompressible. • Compressibility of B{sub 12} icosahedra is considerably lower than that of the bulk material. • Intericosahedral 2e2c bonds are almost as stiff as some of intraicosahedral ones.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Efficient conversion from UV light to near-IR emission in Yb{sup 3+}-doped triple-layered perovskite CaLaNb{sub 3}O{sub 10}

Graphical abstract: CaRNb{sub 3}O{sub 10} is a self-activated oxide due to charge transfer transition in octahedral NbO{sub 6} groups. CaLaNb{sub 3}O{sub 10}:Yb{sup 3+} presents intense IR emission due to the cooperative energy transfer from host (NbO{sub 6}) to Yb{sup 3+} is responsible. It could be expected to be potentially applicable for enhancing photovoltaic conversion efficiency of Si-based solar cells. - Abstract: Yb{sup 3+}-doped triple-layered perovskite CaLaNb{sub 3}O{sub 10} micro-particles were synthesized via the solid-state reaction method. The crystal structure and morphology of the polycrystalline samples were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurements, respectively. The reflectance spectra, photoluminescence (PL) excitation and emission spectra, the decay curves, and the absolute quantum efficiency (QE) of the near-infrared (NIR) emission (910–1100 nm) were measured. Under excitation of UV light, Yb{sup 3+}-doped perovskite shows an intense NIR emission attributed to the {sup 2}F{sub 5/2} → {sup 2}F{sub 7/2} transitions of Yb{sup 3+} ions, which could match maximum spectral response of a Si-based solar cell. This is beneficial for its possible application in an enhancement of the photovoltaic conversion efficiency of solar energy utilization. The efficient energy transfer in Yb{sup 3+}-doped CaLaNb{sub 3}O{sub 10} from NbO{sub 6} groups into Yb{sup 3+} ions was confirmed by the spectra and fluorescent decay measurements. Cooperative energy transfer (CET) was supposed to be the NIR emission mechanism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Special pure germanium-rich Ga-Ge-As-Se glasses for active mid-IR fiber optics

Highlights: • Special pure Ga{sub x}Ge{sub 25}As{sub 15}Se{sub 60-x} (x = 0; 1; 2; 3; 4; 5) glasses were prepared and investigated. • The glasses have high glass transition temperature (>320 °C) and low tendency to crystallization. • The microstructure, the transmission region and the linear refractive index of glasses were studied. • Dispersion optical parameters of glasses were calculated using the Wemple-DiDomenico model. • For the first time, a single-index Ga{sub 3}Ge{sub 25}As{sub 15}Se{sub 57} glass fiber was fabricated and investigated. - Abstract: Special pure Ga{sub x}Ge{sub 25}As{sub 15}Se{sub 60-x} (x = 0; 1; 2; 3; 4; 5) glasses were prepared using various methods for purification of the glass-forming melt. The glasses are characterized by high transparency in the spectral range 0.8–15 μm, low impurity content, high glass transition temperature (>320 °C), and low tendency to crystallization. The microstructure, the transmission range edges, the optical band-gap energy, and the linear refractive index of the glasses are studied. The refractive index of Ga{sub x}Ge{sub 25}As{sub 15}Se{sub 60-x} (x = 0÷5) glasses measured by ellipsometry increases with the substitution of selenium by gallium. It is for the first time that a single-index Ga{sub 3}Ge{sub 25}As{sub 15}Se{sub 57} glass fiber was fabricated, its minimum optical loss was about 0.6 dB/m at a wavelength of 6.7 μm. High-purity germanium-rich Ga-Ge-As-Se glasses were shown to be a promising material for active mid-IR fiber optics.

36 MATERIALS SCIENCE↗
DOE OSTI2015

119 Sn-NMR investigations on superconducting Ca 3 Ir 4 Sn 13 : Evidence for multigap superconductivity

In this study, we report bulk superconductivity (SC) in Ca 3 Ir 4 Sn 13 by means of 119 Sn nuclear magnetic resonance (NMR) experiments. Two classical signatures of BCS superconductivity in spin-lattice relaxation rate (1/T 1 ), namely the Hebel–Slichter coherence peak just below the T c , and the exponential decay in the superconducting phase, are evident. The noticeable decrease of 119 Sn Knight shift below T c indicates spin-singlet superconductivity. The temperature dependence of the spin-lattice relaxation rate 119 (1/T 1 ) is convincingly described by the multigap isotropic superconducting gap. NMR experiments do not witness any sign of enhanced spin fluctuations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Near-IR Luminescence Tuning in a Series of Chalcogenophene Carboxylate-Decorated Neodymium Dimers

Here, the solvothermal synthesis of a series of Nd dimers decorated with various chalcogenophene carboxylates and 2,2':6',2"-terpyridine of the general formula, [Nd 2 (µ-XC 5 H 3 O 2 ) 2 (XC 5 H 3 O 2 ) 4 (N 3 C 15 H 11 ) 2 (H 2 O) 2 ] where X = O, S, Se, and Te, is reported. The solid-state structures were characterized using single-crystal X-ray diffraction (scXRD) and all the complexes are isomorphous, despite substitution of the heterocyclic chalcogen; phase purity was confirmed via powder X-ray diffraction (pXRD). Vibrational spectroscopy was collected and correlations between chalcogen identity and the binding strength of the carboxylate groups of the chalcogenophene ligands with each metal center were shown to be independent of chalcogen identity. All four complexes displayed Nd(III)-based near-IR luminescence and exhibited ligand-sensitized emission. Varying the chalcogenophene chromophore enabled tuning of the sensitizing triplet state energy level, as evidenced by an 8-fold increase in the sensitization of the TeCA-decorated dimer relative to the other chalcogenophene congeners. This behavior was rationalized by comparing the Nd(III) acceptor and ligand donor states across the series. The donor triplet state of each ligand was estimated via low-temperature (77 K) phosphorescence measurements from 1:1 mixtures with Gd(III); these were found to be 24,631 cm –1 for furan-2-carboxylic acid (FCA), 23,764 cm –1 for thiophene-2-carboxylic acid (TCA), 22,548 cm –1 for selenophene-2-carboxylic acid (SeCA), and 21,186 cm –1 for tellurophene-2-carboxylic acid (TeCA). The greater sensitization efficiency of TeCA is the result of well-matched ligand donor and metal acceptor levels and thus suppression of nonradiative back-energy transfer. More broadly, triplet energy level information for these ligands serves as a guide for future application to other target metals based on the electronic properties necessary to effect efficient sensitization.

Coordination Chemistry↗
DOE OSTI2017

Gold Corroles as Near-IR Phosphors for Oxygen Sensing

The triplet state of gold(III) corroles is exploited for optical oxygen sensing. We report intense phosphorescence for gold(III) corroles in the near-IR, an optical window that is ideal for tissue transparency. Moreover, the triplet excited-state emission exhibits significant changes in intensity and lifetime over the 0–160 Torr O 2 pressure range. This renders these compounds sensitive at biologically relevant pressures and overcomes the spectral limitations of palladium and platinum porphyrins for oxygen sensing in biology.

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

Hydrogen-Bonding Network and OH Stretch Vibration of Cellulose: Comparison of Computational Modeling with Polarized IR and SFG Spectra

Hydrogen bonds play critical roles in noncovalent directional interactions determining the crystal structure of cellulose. Although diffraction studies accurately determined the coordinates of carbon and oxygen atoms in crystalline cellulose, the structural information on hydrogen atoms involved in hydrogen-bonding is still elusive. This could be complemented by vibrational spectroscopy; but the assignment of the OH stretch peaks has been controversial. In this study, we performed calculations using density functional theory with dispersion corrections (DFT-D2) for the cellulose Iβ crystal lattices with the experimentally determined carbon and oxygen coordinates. DFT-D2 calculations revealed that the OH stretch vibrations of cellulose are highly coupled and delocalized through intra- and interchain hydrogen bonds involving all OH groups in the crystal. Additionally, molecular dynamics (MD) simulations of a single cellulose microfibril showed that the conformations of OH groups exposed at the microfibril surface are not well-defined. Finally, comparison of the computation results with the experimentally determined IR dichroism of uniaxially aligned cellulose microfibrils and the peak positions of various cellulose crystals allowed unambiguous identification of OH stretch modes observed in the vibrational spectra of cellulose.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Direct Observation of the Photoreduction Products of Mn(NDI-bpy)(CO) 3 XCO 2 Reduction Catalysts Using Femtosecond Transient IR Spectroscopy

The electrochemical reduction of the Mn(bpy)(CO) 3 X CO 2 reduction catalyst is thought to proceed by the initial reduction of Mn I to Mn 0 . Here, we have covalently attached a naphthalenediimide radical anion (NDI •– ) chromophore to the 4-, 5-, or 6-position of the bpy via a phenyl bridge to produce Mn(NDI •– -bpy)(CO) 3 X, where X = Br, CH 3 CN, or DMF, and have used femtosecond and nanosecond transient IR spectroscopy to directly observe the intermediates produced by two electron-transfer reactions following selective photoexcitation of NDI •– to its lowest excited doublet state, 2* NDI •– . In complexes where NDI •– is attached at the 4- or 5-position of bipyridine, only the reaction Mn( 2* NDI •– -bpy)(CO) 3 X → Mn(NDI-bpy•–)(CO) 3 X is observed, whereas in the complex where NDI •– is attached to the 6-position of bipyridine, the reaction sequence Mn( 2* NDI •– -bpy)(CO) 3 X → Mn(NDI-bpy •– )(CO) 3 X → Mn0(NDI-bpy)(CO) 3 is observed. Additionally, in the complexes with an NDI •– bound to the 6-position of bipyridine, Mn0(NDI-bpy)(CO) 3 exhibits a lifetime that is ~10 5 times longer than those in complexes with an NDI •– bound at the four- or five-position of the bipyridine.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Comment on “Microhydration of Biomolecules: Revealing the Native Structures by Cold Ion IR Spectroscopy”

This paper presents a re-examination of the conclusions of a study reported in The Journal of Physical Chemistry Letters (Saparbaev et al., 2021, 12, 907) that compared the structure of microsolvated ions formed by electrospray ionization to those formed in the gas-phase via a previously published cryogenic ion trap approach. We conducted additional experiments that clearly show that most of the observed differences in the IR spectra can be accounted for by considering the different spectroscopic action schemes used to obtain them. In particular, the presence of the D 2 -tag induces shifts in some of the N-H and O-H peaks which need to be carefully considered before comparing spectra. Furthermore, once these spectral effects are taken into account, we show that both clustering approaches yields similar clusters structures for the small GlyH + (H 2 O)n species. Using unimolecular reaction rate theory, we also show that for the small complexes considered here, only the gas-phase equilibrium distribution of conformers should be expected in both experimental approaches. In addition, the barrier heights necessary to kinetically trap high-energy conformers at 298K is explored using a series of model polyalanine chains.

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

Wetting of a Hydrophobic Surface: Far-IR Action Spectroscopy and Dynamics of Microhydrated Naphthalene

The interaction of water and polycyclic aromatic hydrocarbons is of fundamental importance in areas as diverse as materials science and atmospheric and interstellar chemistry. The interplay between hydrogen bonding and dipole–π interactions results in subtle dynamics that are challenging to describe from first principles. Here, we employ far-IR action vibrational spectroscopy with the infrared free-electron laser FELIX to investigate naphthalene with one to three water molecules. We observe diffuse bands associated with intermolecular vibrational modes that serve as direct probes of the loose binding of water to the naphthalene surface. These signatures are poorly reproduced by static DFT or Møller–Plesset computations. Instead, a rationalization is achieved through Born–Oppenheimer Molecular Dynamics simulations, revealing the active mobility of water over the surface, even at low temperatures. Therefore, our work provides direct insights into the wetting interactions associated with shallow potential energy surfaces while simultaneously demonstrating a solid experimental–computational framework for their investigation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗