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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

NASA Composite Materials Development: Lessons Learned and Future Challenges

Composite materials have emerged as the materials of choice for increasing the performance and reducing the weight and cost of military, general aviation, and transport aircraft and space launch vehicles. Major advancements have been made in the ability to design, fabricate, and analyze large complex aerospace structures. The recent efforts by Boeing and Airbus to incorporate composite into primary load carrying structures of large commercial transports and to certify the airworthiness of these structures is evidence of the significant advancements made in understanding and use of these materials in real world aircraft. NASA has been engaged in research on composites since the late 1960 s and has worked to address many development issues with these materials in an effort to ensure safety, improve performance, and improve affordability of air travel for the public good. This research has ranged from synthesis of advanced resin chemistries to development of mathematical analyses tools to reliably predict the response of built-up structures under combined load conditions. The lessons learned from this research are highlighted with specific examples to illustrate the problems encountered and solutions to these problems. Examples include specific technologies related to environmental effects, processing science, fabrication technologies, nondestructive inspection, damage tolerance, micromechanics, structural mechanics, and residual life prediction. The current state of the technology is reviewed and key issues requiring additional research identified. Also, grand challenges to be solved for expanded use of composites in aero structures are identified.

Tenney, Darrel R.↗
DOE OSTI2025

HIGH-FIDELITY SIMULATION OF SOOT FORMATION AND THERMAL RADIATION IN A LABORATORY-SCALE RICH-QUENCH-LEAN BURNER

High-fidelity simulations of a swirl-stabilized turbulent spray flame in a laboratory-scale aero-combustor have been performed to evaluate the predictability of state-of-the-art models in capturing soot formation. The simulations employ a complex chemical mechanism developed for Jet-A with PAH chemistry, coupled with the Hybrid Method of Moments (HMOM) soot model, and a Lagrangian dilute spray model for the fuel injection. Two simulations are performed to compare the results when thermal radiation is neglected or included in the solution with a mean spectral model. Modeling closures for the soot differential diffusion effects in mixture fraction space, as well as turbulence-radiation interaction are also evaluated using the data generated by the simulations. Given the degree of complexity of the simulation, the results showed good agreement with experimental measurements of the spatial distribution of the soot volume fraction ensemble average. A closer agreement with the experiment is observed when thermal radiation is included in the solution. Thermal radiation is observed to reduce the flame temperature and increase the flame intermittency, denoted by the increase in the temperature standard deviation in mixture fraction space. The reduction in temperature also leads to a reduction in PAH production and soot volume fraction. Turbulence is observed to have different effects on radiative emission depending on the mixture fraction. Turbulent scalar fluctuations significantly enhance radiative emission in fuel lean mixtures and can also play a role for fuel rich conditions. The statistical description of the turbulence-radiation interaction, previously proposed in the literature, was observed to correctly reproduce the high-fidelity results. Model coefficients were provided for swirl-stabilized flames. The soot differential diffusion model, previously proposed in the literature, based on the residual between the exact term and its model approximation, was also evaluated. The residual correction term further improved the agreement with exact differential diffusion term evaluated with the high-fidelity simulation data in mixture fraction space. The results suggest that the effective turbulent Lewis number can be equal to unity in simulations of turbulent non-premixed recirculating flames.

Soriano, Bruno [Sandia National Laboratories (SNL)↗
DOE OSTI2021

Ternary aromatic and anti-aromatic clusters derived from the hypho species [Sn 2 Sb 5 ] 3-

Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M 2 (CO) 6 Sn 2 Sb 5 ] 3- (M = Cr, Mo), and [(MSn 2 Sb 5 ) 2 ] 4- , (M = Cu, Ag)) in the process of capturing the hypho - [Sn 2 Sb 5 ] 3- in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo 2 (CO) 6 Sn 2 Sb 5 ] 3- stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn 2 Sb 5 ) 2 ] 4- and [(CuSn 2 Sb 5 ) 2 ] 4- render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn 2 Sb 5 ] 3- , thus providing conceptual advances in the field of metal-metal bonding in clusters.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Computational Methods for Modeling Electrospray Microdroplet Chemistry for Improved Quantitative Mass Spectrometry

This project aimed at enhancing the quantitative analysis capabilities of electrospray ionization mass spectrometry (ESI-MS) by developing advanced computational methods. The primary focus was to integrate continuum and molecular dynamics simulations to study the behavior of microdroplets in the ESI process, from formation to evaporation. Through this research, we sought to bridge significant length and time scales to provide a comprehensive understanding of how analyte concentrations evolve from bulk solutions into gas-phase ions. This understanding is crucial for addressing challenges such as ionization efficiency, solvent effects, and ion suppression, which currently limit the accuracy of quantitative ESI-MS.

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

The influence of water, diet, and temperature on 87 Sr/ 86 Sr in fin spines of juvenile Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus

Analysis of microchemistry in fish fin spines offers a non-lethal approach to address key questions relating to spatial patterns and habitat use of fish. Reconstruction of life history is based on chemical changes within calcified structures with an underlying assumption of elemental incorporation relative to environmental concentration. However, information is limited on the relative influence of water and diet concentrations of elements to corresponding concentrations within fin spines. Strontium (Sr) is commonly used in trace element studies because of its predictable changes within watersheds, with recent applications showing utility of 87 Sr/ 86 Sr for greater spatial resolution. Therefore, this study evaluated the influence of water and diet 87 Sr/ 86 Sr on pectoral fin spines of Atlantic Sturgeon A. oxyrinchus oxyrinchus in controlled laboratory experiments. In the first experiment, fish were exposed to a control, water spiked with 0.10 mg/L of 87 Sr or diet spiked with 0.25 µg/g or 0.50 µg/g of 87 Sr in replicated tanks for 12 weeks. In a second experiment, to determine the time duration required to occupy a different environment for fin spine chemistry to change, fish were maintained in water- or diet-spiked treatments for 1, 2, 3, or 6 weeks. Additionally, to determine if temperature has an influence on 87 Sr/ 86 Sr in fin spines, fish were held at 15 and 25°C for 12 weeks. Fin spines were analyzed using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), and water and diet samples were analyzed using solution based ICP-MS. Results from Experiment 1 indicate water is the primary contributor and diet a secondary contributor of 87 Sr/ 86 Sr in pectoral fin spines of Atlantic Sturgeon. Results from Experiment 2 indicate fin spine 87 Sr/ 86 Sr can be influenced by water after 1 week and diet after 12 weeks. Additionally, although sample size was limited (n=3), water temperature did not have an effect on 87 Sr/ 86 Sr fin spine chemistry. In conclusion, these results provide guidance for interpretation of 87 Sr/ 86 Sr in pectoral fin spines of sturgeon and indicate usefulness of the technique for retrospectively estimating movement and habitat use.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Unprecedented lattice volume expansion on doping stereochemically active Pb 2+ into uniaxially strained structure of CaBa 1- x Pb x Zn 2 Ga 2 O 7

Lone pair cations like Pb 2+ are extensively utilized to modify and tune physical properties, such as nonlinear optical property and ferroelectricity, of some specific structures owing to their preference to adopt a local distorted coordination environment. Here we report that the incorporation of Pb 2+ into the polar “114”-type structure of CaBaZn 2 Ga 2 O 7 leads to an unexpected cell volume expansion of CaBa 1- x Pb x Zn 2 Ga 2 O 7 (0 ≤ x ≤ 1), which is a unique structural phenomenon in solid state chemistry. Structure refinements against neutron diffraction and total scattering data and theoretical calculations demonstrate that the unusual evolution of the unit cell for CaBa 1- x Pb x Zn 2 Ga 2 O 7 is due to the combination of the high stereochemical activity of Pb 2+ with the extremely strained [Zn 2 Ga 2 O 7 ] 4- framework along the c -axis. The unprecedented cell volume expansion of the CaBa 1- x Pb x Zn 2 Ga 2 O 7 solid solution in fact is a macroscopic performance of the release of uniaxial strain along c -axis when Ba 2+ is replaced with smaller Pb 2+ .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1994

Measurement of atmospheric OH by titration of near-IR fluorescent dyes

Recent research has shown that certain polymethine dyes can be detected at ultratrace levels (greater than or equal to 6x10(exp -14) M) in solution by fluorimetry. These detection limits are possible because of the inherent sensitivity of fluorescence techniques, because the dyes fluoresce in the near infrared region where background interference is negligible, and because powerful infrared diode lasers are now available to improve the signal to noise ratio. Other work has shown that the hydroxyl radical destroys the ability of polymethine dyes to fluoresce. These observations form the basis for a new hydroxyl radical detector that is essentially a fluorometric titrator. Theoretically, the detector should show an acceptable sensitivity and response time. Assuming that the atmospheric HO concentration is about 10(exp -11) moles m(exp -3) (i.e. 10(exp 6) molecules cm(exp -3)), then 10 L of air 'titrated' with 20 mL of 10(exp -11) M dye solution (an easily detected concentration) should result in a drop in the fluorescent signal of 50 percent - a readily detectable change. At a flow rate of 3 L min(exp -1) the sampling time would be 3 minutes. The biggest potential problem is selectivity: other oxidants may also cause the fluorescence signal to be lost. The chemistry of polymethine dyes has not been studied in detail and so no quantitative data are available. However, a survey of the literature suggests that in general HO should react up to six orders of magnitude faster than HO2 and other radicals such as RO2 and RO. It should also react much more rapidly than H2O2 and O3. Thus it may be possible to discriminate kinetically against potential interfering substances. It was shown in the laboratory that 10(exp -4) M H2O2 has little effect on the absorption spectrum of the dye IR125 over a period of hours but that the band at 780 nm is slowly lost in water over a period of days even under argon in the dark. By contrast, DMSO solutions of IR125 are stable.

Betterton, Eric A.↗
DOE OSTI2021

The Reactivity of Polyethylene Microplastics in Water under Low Oxygen Conditions Using Radiation Chemistry

Polyethylene (PE) is an intensely utilized polymer, which has consequently led to it becoming a common environmental contaminant. PE and other plastic waste are known to be highly persistent in surface waters; however, chemical and physical changes do take place over time, dependent mostly on highly variable natural conditions, such as oxygen (O2) availability. Gamma radiation was used to generate reactive oxygen species, namely hydroxyl radicals, in initially aerated aqueous solutions to simulate the natural weathering of microplastics in waters where there are fluctuations and often depletions in dissolved O2. The headspace of the irradiated PE-containing solutions was probed for the formation of degradation products using solid-phase microextraction (SPME) fibers in combination with gas chromatography mass spectrometry (GCMS). The major species detected were n-dodecane, with trace levels of tridecane, 2-dodecanone, and hexadecane, which were believed to be predominately adsorbed in the PE microplastics in excess of their aqueous solubility limits. Surface characterization by Raman spectroscopy and light and dark field microscopy indicated no change in the chemical composition of the irradiated PE microplastics under low O2 to anaerobic conditions. However, morphological changes were observed, indicating radical combination reactions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Thermodynamic controls on the synthesis, structure and reactivity of materials for energy (Final Report)

The major objectives have been: a) to advance and use unique calorimetric capabilities to determine the energetics of oxide and other materials having possible energy applications, with an emphasis on new materials for batteries, fuel cells and solar energy conversion, b) to understand, in terms of both macroscopic energetics and microscopic structure and bonding, the interplay of defect chemistry, oxidation-reduction, and size effects at the bulk and nanoscale in determining materials properties. This project emphasizes mixed ionic-electronic conduction materials containing transition metals of variable valence, especially perovskites and lithium containing phases, with M = Mn, Fe, Co, Ni. The thermochemistry of new families of complex halide, chalcogenide, nitride and hybrid (organic-inorganic) perovskite materials were explored. The major and unique technique employed is high temperature oxide melt solution calorimetry, with careful attention given to materials synthesis and characterization. The thermochemical studies will be coupled with structural studies, especially to characterize order-disorder phenomena by in situ high temperature diffraction techniques.

14 SOLAR ENERGY↗
DOE OSTI2022

Enriching Cations Using Electric Field Gradients Generated by Bipolar Electrodes in the Absence of Buffer

We discuss that ionic current gradients and corresponding electric field gradients formed at bipolar electrodes are useful for enriching cations up to ~350-fold at specific locations in microfluidic devices. The enrichment mechanism is determined by collecting current data, measuring solution conductivity, and by performing pH indicator experiments. These data reveal the dynamic nature of the enrichment mechanism. Specifically, they show the complex relationship between the ionic current gradients formed at the bipolar electrode and the extent of cation enrichment. Finally, we demonstrate cation enrichment is possible in buffer-free solutions containing up to 50.0 mM KCl. This finding is significant because it broadens the range of solutions in which membrane-free, electrochemical separations using bipolar electrodes can be performed.

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

The channel-source hypothesis: Empirical evidence for in-channel sourcing of dissolved organic carbon to explain hysteresis in a headwater mountain stream

Catchment hydrologists have long puzzled over the question: How can catchments rapidly generate storm flows and pulses of solutes in response to storm events? Conceptual models viewing catchments as composed of discrete source areas generating flow at unique time scales and with unique chemical characteristics have been used to explain the observed changes in flow and water chemistry. Surprisingly, those conceptual models usually do not treat the stream channel as one of the potential source areas. We propose the channel-source hypothesis in which the stream itself should be considered as a potential source with the same rigour as other contributing areas. We pose this in the spirit of the scientific use of the word: a hypothesis is not a proven idea but rather a provisional supposition serving as the basis for further study. We suggest that the channel should be considered as a potential source for dissolved organic carbon (DOC). Channels store substantial amounts of organic matter, and stream ecologists have long studied stream carbon cycling. From those studies, we know that leaching and decomposition can generate DOC from particulate organic carbon (POC). Further, POC is stored in channel ‘dead-zones’—regions of low flow velocity - that can be activated as flow velocity increases, thus releasing accumulated DOC during storms. All catchments are different; there is no reason to assume that channel sources are always important, in every catchment, in every storm. Thus, the channel-source hypothesis does not replace existing conceptual models. Instead, it adds another potential mechanism that may explain DOC dynamics observed in streams. The channel-source hypothesis has substantial implications for catchment studies examining sources of DOC in stream water or using DOC as a tracer to determine the locations of, and proportional contributions of, different source areas for streamflow generation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Extraction of Pm-147 from savannah river site nuclear material management programs

The Savannah River Site (SRS) processes used-nuclear fuel to recover uranium. There are many interesting fission products lost in the raffinate from this separation including 147 Pm. Here, the goal of this work was to recover 147 Pm from SRS waste solutions. A radiochemical separation method typically used for the determination of 147 Pm and 151 Sm was modified to purify significant quantities of 147 Pm from the H Canyon waste solutions. The developed scheme was tested on a small aliquot of waste solution from the processing of used fuel from the High Flux Isotope Reactor at Oak Ridge National Laboratory.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗