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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Raman spectroscopy: A tool to investigate alpha decay damage in a PuO 2 crystal lattice and determining sample age since calcination

Raman microspectroscopy can be used to measure local physical properties of materials, such as the lattice parameter. Alpha decay induced lattice damage of plutonium dioxide (PuO 2 ) results in the growth of new bands and broadening of the T 2g band. A relationship between the change in the lattice parameter and storage time has been established in the literature using X-ray diffraction (XRD). In this work, our measured time-dependent Raman spectra of PuO 2 particulates matches the XRD results. This new Raman spectroscopic technique can provide dating information on the time elapsed since the last calcination of PuO 2 using a single >5 μm particulate in contrast to 50 mg of 10–50 μm particles required by XRD.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Spectroscopic pressure investigation of a novel high energy system

This work here combines a novel multimodal spectroscopic technique, O–PTIR and Raman spectroscopy, which allows for the simultaneous collection of infrared and Raman spectra, with traditional diamond anvil cell techniques to explore pressure induced phase transitions in a high energy material. Two phase transitions are revealed, with the first transition emerging below 0.23 GPa, to a higher order phase, followed by a broad transition to a lower order phase. Aside from the pressure studies, hyperspectral imaging was performed, confirming the homogeneous nature of the system.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ion‐Conducting, Electron‐Blocking Layer for High‐Performance Solid Electrolytes

Lithium metal batteries bring greater promise for energy density, often relying on solid‐state electrolytes to meet critical benchmarks. However, Li dendrite formation is a prevailing problem that limits the cycle life and Coulombic efficiency of solid‐state Li metal batteries. For the first time, a thin (<100 nm) layer of electronically insulating, ionically conducting lithium phosphorus oxynitride (LiPON) is applied using atomic layer deposition between a Li anode and garnet Li 7 La 3 Zr 2 O 12 (LLZO). The performance of a conformal LiPON layer as an electron barrier in symmetric Li‐LLZO cells is observed through potential step chronoamperometry, galvanostatic cycling, electron microscopy, and various spectroscopic techniques. The LiPON‐coated LLZO achieves 100 times lower electronic conductance than LLZO alone. Cycling carried out at 0.1 mA cm −2 for 100 cycles demonstrates that suppression of electron pathways into the bulk solid electrolyte improves the cycle life of a lithium metal cell. These findings suggest an electronic conductivity effect in solid‐state electrolytes. A strategy is demonstrated to design thin‐film (LiPON)‐modulated bulk solid‐state electrolytes (LLZO) capable of maintaining high ionic conductivity and electrochemical stability while reducing the effective electronic conductivity, which results in significantly decreased dendrite formation, improved cycle life, and greater interfacial integrity between the electrolyte and a Li anode.

Hitz, Emily M.↗
DOE OSTI2023

High-Field Nuclear Magnetic Resonance (NMR) Spectroscopy

Nuclear magnetic resonance (NMR) is a non-destructive spectroscopic technique that provides detailed molecular structural information via the electronic environments of nuclei in materials. Higher magnetic field strengths enhance the resolution of NMR, enabling discernment of unique chemical environments that might not be possible at low fields. Herein, the application of high-field NMR to catalyst and electrochemical system characterization are detailed. A brief description of NMR and quadrupolar nuclei are presented where the effects of magnetic field are described. Examples of high-field NMR are provided with particular focus on employing NMR to elucidate the structure of oxides of aluminum and vanadium for catalyst applications. The role of high-field NMR to conduct challenging experiments for energy storage materials is also explored and numerous other nuclei which require high-field measurement are briefly summarized.

Catalyst, Spectroscopy, NMR, High-field, Quadrupol↗
DOE OSTI2018

Fluorescence and Raman Spectroscopy of Doped Nanodiamonds

Raman and fluorescence spectroscopic techniques were used to study doped nanodiamonds synthesized at high pressure and high temperature (HPHT technique) and by chemical vapor deposition from the gas phase (CVD technique). For the CVD diamonds, a hundred-fold increase in fluorescence intensity of the silicon-vacancy centers normalized to the volume of the probe material was observed with an increase in synthesized diamond particle diameter from 150 to 300 nm. Graphitization temperature upon heating in the air significantly lower than for detonation nanodiamonds was found for the boron-doped HPHT nanodiamonds.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Highly Selective Detection of Cr{sup 3+} Ion with Colorimetric & Fluorescent Response Via Chemodosimetric Approach in Aqueous Medium

So far, very few numbers of chemosensors for Cr{sup 3+} ion have been reported. However, the main drawback of reported receptors are the lack of selectivity and other trivalent cations such as Fe{sup 3+}, Al{sup 3+} and anions like F{sup −} and {sup −}OAc frequently interfere with such assays. This paper present the synthesis, characterization & sensor studies of Schiff base containing naphthalene moiety which selectively detect Cr{sup 3+} ion by chemodosimetric approach. Using FT-IR, {sup 1}H NMR, {sup 13}C NMR and ESI mass spectroscopic techniques the probe was characterized. This receptor exhibit more selectivity and sensitivity towards Cr{sup 3+} than other divalent and trivalent cations like Mn{sup 2+}, Zn{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cd{sup 2+}, Cu{sup 2+}, Hg{sup 2+}, Fe{sup 3+}, and Al{sup 3+} ions. After the addition of chromium ion the receptor get change from yellow to colorless in aqueous medium. But no color change was observed on the addition of other metal ions. Using UV-Vis and PL studies, it was confirmed that the selective hydrolysis of imine group of receptor by Cr{sup 3+} ions takes place with high fluorescence enhancement that is corresponding to 1-naphthylamine. Receptor acts as selective chemodosimeter for Cr{sup 3+} ions with 2:1 stoichiometry and micro molar detection limit. This chemodosimetric approach was applied successfully for bio-imaging of HeLa cells.

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

Two-step Conversion of Crude Glycerol Generated by Biodiesel Production into Biopolyols: Synthesis, Structural and Physical Chemical Characterization

In this work biopolyols were synthesized via two-step process from crude glycerol and castor oil. For better evaluation of analyzed process, the impact of its time and temperature on the structure and properties of biopolyols was determined. Obtained results fully justified conducting of synthesis in two steps. Prepared materials were characterized by hydroxyl value and water content comparable to polyols industrially applied in manufacturing of polyurethane materials. Synthesized biopolyols were characterized in terms of their chemical structure using spectroscopic techniques: Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance spectroscopy. Obtained data confirmed the influence of synthesis’ parameters on the chemical structure of prepared biopolyols and correlated with their other parameters. On both stages of reaction, collected by-products were also analyzed with FTIR spectroscopy.

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

Waste Eggshells for the Decoration of Carbon Nanotubes and Graphene Nanosheets with Hydroxyapatite for Preparation of LLDPE Nanocomposites

Waste eggshells were used to decorate functionalized carbon nanotubes (CNT) and graphene oxide (GO) by hydroxyapatite (HAP) using in situ synthesis. The HAP decorated CNT and GO were characterized by X-ray diffraction, SEM, and IR spectroscopic techniques. CNT-HAP and GO-HAP were further used to prepare polymer nanocomposites by addition of different percentages of synthesized CNT-HAP and GO-HAP as fillers into linear low density polyethylene (LLDPE). The prepared nanocomposites specimens were utilized for physical and thermo-mechanical analysis. Mechanical properties of the LLDPE nanocomposites were improved with increasing the percentage of CNT-HAP and GO-HAP fillers compared to the pristine LLDPE. Hardness of hybrid-CNT-HAP/LLDPE composite was increased as compared to the GO-HAP/LLDPE, where as tensile strength of the GO-HAP/LLDPE was higher than that of the CNT-HAP/LLDPE composite. Flammability of CNT-HAP and GO-HAP composites was decreased by 32% as compared to the pristine LLDPE. Graphic Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2018

Impedance Spectroscopy, Magnetic and Optical Analysis of Cadmium Tungstate Nanoparticles from Influence of Capping Agent Additives

Nano crystals of cadmium tungstate (CdWO{sub 4}) were obtained by facile precipitation route by using cadmium sulfate octahydrate and sodium tungstate dihydrate. These nanoparticles were then coated using different capping agents such as glucose, polyvinyl alcohol (PVA), and valine and their effects on the particle size, band gap, morphology, and magnetic character were investigated by powder X-ray diffraction, UV-Visible, FESEM, TEM, and VSM analysis. Capping agents are used in the synthesis of nanoparticles since they facilitate the growth and aggregation of particles in a precise manner, by usually acting as a physical barrier which controls the flow of free electron to the catalyst, so that they can be utilized by the catalyst and sensors of nanoparticle. Impedance spectroscopic technique was carried out, which was very useful in separating the grain boundary resistance and grain boundary capacitance contributions. We discuss the utilization of capping agents and their effects, including surface, optical and intergranular potential barriers in this work.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Production of cyclo-hafnium metal–organic thin film using a specific method

Cyclo-hafnium metal–organic thin film was successfully synthesized and deposited on amorphous glass using a specific method, where amorphous substrate was used for synthesis and coating. Then, the film was annealed at 300 °C in an oven (ambient conditions). Optical and structural properties of the films were also investigated within the study. The structure of the film was analyzed using the mid-infrared spectrum. Optical properties were investigated via the UV–Vis spectroscopic technique. Film thickness was measured with AFM (tapping mode). Surface properties and elemental ratio of the films were examined and measured with SEM and EDX analysis. The highest transmittance and lowest reflectance values within the visible range were identified. The characteristic triethanolamine and hafnium-oxide peaks were observed in the infrared spectrum. FIR spectra of the films were found to be in accordance with the literature. SEM images of the films revealed that the surface of the films is fragile. EDX analysis of hafnium, organic parts of the compound and some minerals of amorphous glass were shown.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Biochemical and spectroscopic characterizations of the oligomeric antenna of the coral symbiotic Symbiodiniaceae Fugacium kawagutii

Light-harvesting antennas in photosynthesis capture light energy and transfer it to the reaction centers (RCs) where photochemistry takes place. The sustainable growth of the reef-building corals relies on a constant supply of the photosynthates produced by the endosymbiotic dinoflagellate, belonging to the family of Symbiodiniaceae. The antenna system in this group consists of the water-soluble peridinin-chlorophyll $\textit{a}$-protein (PCP) and the intrinsic membrane chlorophyll $\textit{a}$-chlorophyll $c_2$-peridinin protein complex (acpPC). In this report, a nonameric acpPC is reported in a dinoflagellate, Fugasium kawagutii (formerly Symbiodinium kawagutii sp. CS-156). We found that extensive biochemical purification altered the oligomerization states of the initially isolated nonameric acpPC. The excitation energy transfer pathways in the acpPC nonamer and its variants were studied using time-resolved fluorescence and time-resolved absorption spectroscopic techniques at 77 K. Compared to the well-characterized trimeric acpPC, the nonameric acpPC contains an 11 nm red-shifted terminal energy emitter and substantially altered excited state lifetimes of Chl $\textit{a}$. The observed energetic overlap of the fluorescence terminal energy emitters with the absorption of RCs is hypothesized to enable efficient downhill excitation energy transfer. Additionally, the shortened Chl $\textit{a}$ fluorescence decay lifetime in the oligomeric acpPC indicate a protective self-relaxation strategy. We propose that the highly-oligomerized acpPC nonamer represents an intact functional unit in the Symbiodiniaceae thylakoid membrane. They perform efficient excitation energy transfer (to RCs), and are under manageable regulations in favor of photoprotection.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Recent Advances in X-ray Absorption Near Edge Structure (XANES) Simulation for Catalysis: Theories and Applications

X-ray absorption spectroscopy (XAS) is a powerful spectroscopic technique for characterizing catalytic active sites. In particular, X-ray Absorption Near Edge Structure (XANES) provides insights into the oxidation state and local coordination environment of the absorbing atom, shedding light on the catalytic structure. Computational XANES simulations provide one-on-one correspondence between the molecular structure and their corresponding spectra, making them an effective approach for interpreting experimental XANES features. This work outlines various theories used to simulate XANES spectra and highlights recent advancements in computational XANES applications for homogeneous, heterogeneous, and single-atom catalysts focusing on identifying the active site structures, the site heterogeneity, and the dynamic evolution of catalysts.

Xu, Jiayi↗
DOE OSTI2019

Tungstenocene-grafted silica catalysts for the selective epoxidation of alkenes

In this study, tungstenocene(IV) dichloride was successfully deposited and grafted on the surface of a commercially-available non-ordered silica support via either a liquid-phase or a dry impregnation approach. After a high-temperature calcination step, two W(VI)-grafted silica catalysts, with a metal loading around 1.2–1.7 wt.%, were obtained. They were fully characterized by physisorption and spectroscopic techniques, which evidenced well-dispersed tungsten oxide polyoxo cluster sites, for the catalyst prepared via liquid-phase grafting, and evenly dispersed larger monoclinic tungsten(VI) oxide aggregates, for the catalyst prepared via dry impregnation, respectively. Both W/SiO 2 solids showed moderate to good conversion values in the epoxidation of (R)-(+)-limonene and methyl oleate (up to 68%), in the presence of aqueous hydrogen peroxide, with good selectivity to the desired epoxides (63% and 78%, respectively). Lastly, the heterogeneous character of the most interesting W/SiO 2 catalyst prepared via dry impregnation was confirmed by a hot centrifugation test and by an extended recovery and reuse of the solid in six catalytic runs.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tuning the hydrogenation of CO 2 to CH 4 over mechano-chemically prepared palladium supported on ceria

CO 2 methanation reactivity, reaction mechanism, and surface structure were investigated on a mechanochemically prepared Pd/CeO 2 catalyst (PdAcCeO 2 -M), where an oxidative pretreatment (-o) increased methane yield by a factor of two compared to a reductive pretreatment (-h). Methanation rates were maintained for over 48 h and further increased upon oxidative regeneration treatments. The surface species of both PdAcCeO 2 -M-o and PdAcCeO 2 -M-h were explored via in situ CO 2 and CO hydrogenation DRIFTS, where CO hydrogenation effectively models the dissociative CO 2 mechanism (CO 2 → CO → CH 4 ). PdAcCeO 2 -M-o yielded distinct Pd-CO adsorption and the absence of monodentate carbonate at ~ 1400 cm -1 , while AP-XPS showed that PdAcCeO 2 -M-o yielded a unique Pd δ+ contribution at 335.9 eV. By gaining insights from various in situ spectroscopic techniques, and by breaking the CO 2 hydrogenation mechanism into piecewise steps, a deeper understanding of the direct CO 2 reduction towards methane and CO over mechanochemically prepared Pd/CeO 2 catalysts was obtained.

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

The superior hydrothermal stability of Pd/SSZ-39 in low temperature passive NOx adsorption (PNA) and methane combustion

We successfully synthesized uniform SSZ-39 with an average crystal size of about a micron. Pd (0.7 - 3 wt%) was supported on SSZ-39 with Si/Al ratio ~12. The as-synthesized materials were characterized by FTIR, XRD, Helium Ion Microscopy, HAADF-STEM imaging, 27 Al, 29 Si and H solid state NMR spectroscopic techniques. FTIR studies with CO and NO probe molecules reveal that the 0.7 wt% Pd/SSZ-39 material with Si/Al ~12 has the majority of Pd dispersed atomically as isolated Pd(II) and Pd(II)-OH centers, and thus can be used as a low-temperature passive NOx adsorber. Pd(II)-NO, Pd(II)(OH)(NO) and Pd(II)(CO)(NO) complexes form during PNA in this material. We compare this PNA material directly with the Pd/SSZ-13 system (with Si/Al ratio ~12) and show its superior hydrothermal stability. Remarkably, Pd/SSZ-39 with Si/Al ratio ~12 survives hydrothermal aging up to 815 ºC in 10% H 2 O/Air vapor for 16 hours without significant loss in activity. The SSZ-39 crystal structure remains intact during hydrothermal aging up to 1,000 ºC as we elucidate it with XRD and HAADF-STEM imaging/EDS mapping. However, changes to the framework during such harsh hydrothermal treatment significantly change the NOx release profiles during PNA as evidenced by high-field 27 Al NMR on fresh and aged Pd/SSZ-39 samples as well as PNA performance measurements. Besides PNA application, these hydrothermally very stable materials (3 wt% Pd on SSZ-39 with Si/Al ratio ~12) can be used as a robust methane combustion catalyst under industrially relevant conditions (GHSV~600,000hr -1 ). This catalyst shows minimal deactivation after both harsh hydrothermal aging at 750 and 800 ºC, and prolonged time on stream (105 hrs) at 425 °C. In contrast, both 3wt% Pd/alumina and 3wt% SSZ-13 supported samples lose a significant portion of their activity. Our study opens new avenues to prepare the most hydrothermally stable known Pd/zeolite materials with applications for adsorption and catalytic hydrocarbon combustion under industrially relevant conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A survey study on arsenic speciation in coal fly ash and insights into the role of coal combustion conditions

Coal fly ashes (CFAs) are the low-density byproducts of the coal combustion process. Improper or uncontrolled CFA disposal poses significant environmental and health concerns due to the potential leaching of toxic heavy metals such as arsenic (As). Previous studies have investigated the content and speciation of As in different CFA samples, yet systematic information on As speciation in CFA with representative coal source and combustion conditions is still missing. Based on a recent survey study on the typical coal sources and combustion conditions across the U.S., this study selected 19 representative CFA samples to systematically investigate As speciation and potential correlations with these parameters. The composition, morphology, mineralogy, and As speciation of these CFA samples were characterized by complementary analytical, microscopic, and spectroscopic techniques. Synchrotron X-ray spectroscopy and microscopy analyses revealed the dominant As oxidation state to be As(V) and with strong associations to Ca, with the exception of 3 samples that had 19–51% As(III), likely due to the use of selective catalytic reduction (SCR) process. Principal component analysis was conducted to identify potential correlations of As concentration and oxidation state with parameters such as major element content, loss on ignition (LOI), average particle size, coal source, and combustion condition. Al 2 O 3 and FeO content were found to capture a majority of the variability. Further, results from this study provide fundamental basis for understanding the correlations between coal source, combustion conditions, CFA characteristics, and As speciation, and providing insights for downstream beneficial utilization or disposal management.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Isolated oxygen vacancies in strontium titanate shine red: Optical identification of Ti 3+ polarons

Oxide perovskites exhibit fascinating physical properties that identify them as key materials for the next generation of oxide-based functional electronic devices, as well as for catalysis and photochemistry applications. In strontium titanate, substantial efforts have been devoted to elucidate the role of oxygen vacancies and localized electronic states, such as polarons, on those properties. In this paper, a new model is presented that assigns a definitive red luminescence signature at 2.0 eV to Ti 3+ polarons trapped at isolated oxygen vacancies. This emission provides an unequivocal identification for the oxygen vacancies, which allows monitoring their creation and annealing by a variety of physio-chemical treatments. Ionoluminescence with energetic (MeV) ion beams enables such identification by combining the sensitivity and resolution of spectroscopic techniques with their in situ character, as well as controlled incorporation of point defects, such as oxygen vacancies. Alternative models assigning the blue luminescence emission at 2.8 eV to oxygen vacancies are not supported by the experimental results. Finally and therefore, oxygen vacancies shine red and not blue, as previously proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Mechanistic insights into low-temperature oxidation of carbon fibers: Influence of hydrogen defects and crystallite size

Although oxidation mechanisms have been exhaustively studied for graphite, similar analyses of carbon fibers are comparatively sparse. Most prior work has focused on quantifying weight loss or assessing protective surface coatings designed to slow oxidation. The use of optical spectroscopic techniques for oxidation analyses is comparatively unexplored, but such techniques could provide an early indicator of fiber oxidation that would undermine carbon fiber performance. Here, in this work, we applied Raman spectroscopy to study oxidation-induced spectral alterations in 16 carbon fiber types from 7 manufacturers oxidized at 300 °C for 72 h, 400 °C for 8 h, and 500 °C for 1 h. We connect these results with structural properties of the carbon fibers obtained through wide-angle X-ray scattering, identifying a linear dependence between the reactivity of carbon fibers and the crystallite size of the unperturbed fibers. We then demonstrate that substituted hydrogen defects are likely removed from the fiber surface during oxidation and use the relative defect concentration to predict the Raman spectral change as a function of temperature and time, assuming Arrhenius behavior.

Carbon fiber↗