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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Effects of alpha-zirconium phosphate on thermal degradation and flame retardancy of transparent intumescent fire protective coating

Graphical abstract: - Highlights: • A transparent intumescent fire protective coating was obtained by UV-cured technology. • OZrP could enhance the thermal stability and anti-oxidation of the coating. • OZrP could reduce the combustion properties of the coatings. - Abstract: Organophilic alpha-zirconium phosphate (OZrP) was used to improve the thermal and fire retardant behaviors of the phenyl di(acryloyloxyethyl)phosphate (PDHA)-triglycidyl isocyanurate acrylate (TGICA)-2-phenoxyethyl acrylate (PHEA) (PDHA-TGICA-PHEA) coating. The morphology of nanocomposite coating was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of OZrP on the flame retardancy, thermal stability, fireproofing time and char formation of the coatings was investigated by microscale combustion calorimeter (MCC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS) and scanning electric microscope (SEM). The results showed that by adding OZrP, the peak heat release rate and total heat of combustion were significantly reduced. The highest improvement was achieved with 0.5 wt% OZrP. XPS analysis indicated that the performance of anti-oxidation of the coating was improved with the addition of OZrP, and SEM images showed that a good synergistic effect was obtained through a ceramic-like layer produced by OZrP covered on the surface of char.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Poly(methyl methacrylate)/layered zinc sulfide nanocomposites: Preparation, characterization and the improvements in thermal stability, flame retardant and optical properties

Highlights: • Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method. • We prepare PMMA/LZnS nanocomposites by in situ bulk polymerization of MMA. • PMMA/LZnS nanocomposites were investigated by TGA, DSC, MCC, UV–vis and PL test. • The thermal stability, flame retardant and optical properties of PMMA are improved. - Abstract: Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method and poly(methyl methacrylate) (PMMA)/layered zinc sulfide nanocomposites were obtained by in situ bulk polymerization of methyl methacrylate (MMA). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-synthesized layered zinc sulfide and PMMA/layered zinc sulfide nanocomposites. Microscale combustion calorimeter (MCC), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) were used to test the thermal properties of the composites. Ultraviolet visible (UV–vis) transmittance spectra and photoluminence (PL) spectra were obtained to investigate the optical properties of the composites. From the results, the thermal degradation temperature is increased by 20–50 °C, the peak of heat release rate (pHRR) and total heat release (THR) are both decreased by above 30%, and the photoluminence intensity is enhanced with the increasing loading of layered zinc sulfide.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Human dermal absorption of chlorinated organophosphate flame retardants; implications for human exposure

Tris-2-chloroethyl phosphate (TCEP), tris (1-chloro-2-propyl) phosphate (TCIPP) and tris-1,3-dichloropropyl phosphate (TDCIPP) are organophosphate flame retardants (PFRs) widely applied in a plethora of consumer products despite their carcinogenic potential. Human dermal absorption of these PFRs is investigated for the first time using human ex vivo skin and EPISKIN™ models. Results of human ex vivo skin experiments revealed 28%, 25% and 13% absorption of the applied dose (500 ng/cm{sup 2}, finite dose) of TCEP, TCIPP and TDCIPP, respectively after 24 h exposure. The EPISKIN™ model showed enhanced permeability values (i.e. weaker barrier), that were respectively 16%, 11% and 9% for TCEP, TCIPP and TDCIPP compared to human ex vivo skin. However, this difference was not significant (P > 0.05). Estimated permeability constants (K{sub p}, cm/h) showed a significant negative correlation with log K{sub ow} for the studied contaminants. The effect of hand-washing on dermal absorption of PFRs was investigated. Washing reduced overall dermal absorption, albeit to varying degrees depending on the physicochemical properties of the target PFRs. Moreover, slight variations of the absorbed dose were observed upon changing the dosing solution from acetone to 20% Tween 80 in water, indicating the potential influence of the dose vehicle on the dermal absorption of PFRs. Finally, estimated dermal uptake of the studied PFRs via contact with indoor dust was higher in UK toddlers (median ΣPFRs = 36 ng/kg bw day) than adults (median ΣPFRs = 4 ng/kg bw day). More research is required to fully elucidate the toxicological implications of such exposure. - Highlights: • Human dermal absorption of PFRs was studied using human ex vivo skin and EPISKIN™. • Absorbed fractions of TCEP, TCIPP and TDCIPP were 28%, 25% and 13% of applied dose. • Permeability constants showed significant negative correlation to log K{sub ow} of PFRs. • Skin washing reduced the overall dermal absorption of target PFRs to varying degrees. • Toddlers are more exposed to PFRs via dermal contact with indoor dust than adults.

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

Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF

Highlights: • Specification of an empirical factor for conversion from bromine to PBB and PBDE. • The handheld XRF device was validated for this particular application. • A very large number of over 4600 pieces of monitor housings was analysed. • The recyclable fraction mounts up to 85% for TV but only 53% of PC waste plastics. • A high percentage of pieces with bromine contents of over 50,000 ppm was obtained. - Abstract: This contribution is focused on the on-site determination of the bromine content in waste electrical and electronic equipment (WEEE), in particular waste plastics from television sets (TV) and personal computer monitors (PC) using a handheld X-ray fluorescence (XRF) device. The described approach allows the examination of samples in regards to the compliance with legal specifications for polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) directly after disassembling and facilitates the sorting out of plastics with high contents of brominated flame retardants (BFRs). In all, over 3000 pieces of black (TV) and 1600 pieces of grey (PC) plastic waste were analysed with handheld XRF technique for this study. Especially noticeable was the high percentage of pieces with a bromine content of over 50,000 ppm for TV (7%) and PC (39%) waste plastics. The applied method was validated by comparing the data of handheld XRF with results obtained by GC–MS. The results showed the expected and sufficiently accurate correlation between these two methods. It is shown that handheld XRF technique is an effective tool for fast monitoring of large volumes of WEEE plastics in regards to BFRs for on-site measurements.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Formation Mechanisms of Naphthalene and Indene: From the Interstellar Medium to Combustion Flames

The article addresses the formation mechanisms of naphthalene and indene, which represent prototype polycyclic aromatic hydrocarbons (PAH) carrying two six-membered and one five- plus a six-membered ring. Theoretical studies of the relevant chemical reactions are overviewed in terms of their potential energy surfaces, rate constants, and product branching ratios; these data are compared with experimental measurements in crossed molecular beams and the pyrolytic chemical reactor emulating the extreme conditions in the interstellar medium (ISM) and the combustion-like environment, respectively. The outcome of the reactions potentially producing naphthalene and indene is shown to critically depend on temperature and pressure or collision energy and hence the reaction mechanisms and their contributions to the PAH growth can be rather different in the ISM, planetary atmospheres, and in combustion flames at different temperatures and pressures. Specifically, this paradigm is illustrated with new theoretical results for rate constants and product branching ratios for the reaction of phenyl radical with vinylacetylene. The analysis of the formation mechanisms of naphthalene and its derivatives shows that in combustion they can be produced via hydrogen-abstraction-acetylene-addition (HACA) routes, recombination of cyclopentadienyl radical with itself and with cyclopentadiene, the reaction of benzyl radical with propargyl, methylation of indenyl radical, and the reactions of phenyl radical with vinylacetylene and 1,3-butadiene. In extreme astrochemical conditions, naphthalene and dihydronaphthalene can be formed in the C 6 H 5 + vinylacetylene and C 6 H 5 + 1,3-butadiene reactions, respectively. Ethynyl-substituted naphthalenes can be produced via the ethynyl addition mechanism beginning with benzene (in dehydrogenated forms) or with styrene. The formation mechanisms of indene in combustion include the reactions of the phenyl radical with C 3 H 4 isomers allene and propyne, reaction of the benzyl radical with acetylene, and unimolecular decomposition of the 1-phenylallyl radical originating from 3-phenylpropene, a product of the C 6 H 5 + propene reaction, or from C 6 H 5 + C 3 H 5 .

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

LiAlO 2 /LiAl 5 O 8 Membranes Derived from Flame-Synthesized Nanopowders as a Potential Electrolyte and Coating Material for All-Solid-State Batteries

Recently, γ-LiAlO 2 has attracted considerable attention as a coating in Li-ion battery electrodes. However, its potential as a Li + ceramic electrolyte is limited due to its poor ionic conductivity (<10 –10 S cm –1 ). Here, we demonstrate an effective method of processing LiAlO 2 membranes (<50 μm) using nanopowders (NPs) produced via liquid-feed flame spray pyrolysis (LF-FSP). Here, membranes consisting of selected mixtures of lithium aluminate polymorphs and Li contents were processed by conventional tape casting of NPs followed by thermocompression of the green films (100 °C/10 kpsi/10 min). The sintered green films (1100 °C/2 h/air) present a mixture of LiAlO 2 (~72 wt %) and LiAl 5 O 8 (~27 wt %) phases, offering ionic conductivities (>10 –6 S cm –1 ) at ambient with an activation energy of 0.5 eV. This greatly increases their potential utility as ceramic electrolytes for all-solid-state batteries, which could simplify battery designs, significantly reduce costs, and increase their safety. Furthermore, a solid-state Li/Li 3.1 AlO 2 /Li symmetric cell was assembled and galvanostatically cycled at 0.375 mA cm –2 current density, exhibiting a transference number ≈ 1.

25 ENERGY STORAGE↗
DOE OSTI2026

Non-equilibrium reducing flame aerosol process to create supported high-entropy alloy nanoparticles

High-entropy alloy (HEA) nanomaterials provide opportunities and property combinations for energy and electronic applications, but their practical synthesis faces challenges of elemental immiscibility, metal reducibility, and particle aggregation during their synthesis. Herein, we report a broadly applicable non-equilibrium, scalable, and in-situ reducing flame aerosol process for synthesis of supported HEA nanoparticles. This versatile process can directly load a high concentration of 2 ~ 4 nm HEA nanoparticles on various 1- to 3-dimensional supports. Notably, simultaneous formation of HEA nanoparticles and a mesoporous silica support was successfully realized in a single step. Exploration of this process demonstrates the role of kinetics and entropy on decreasing alloy particle size and altering the reducibility of elements. We propose an entropy-induced reduction mechanism to incorporate oxidizable elements into HEAs, which extends the compositional space of HEA nanoparticles. As a representative catalytic application, we present a RuPdOsIrPt/graphene electrocatalyst with high activity and stability for hydrogen oxidation reaction. Our findings open horizons for high-performance HEA design and applications in diverse fields such as catalysis, electrochemistry, and sensing.

organic↗
DOE OSTI2018

Influences of the molecular fuel structure on combustion reactions towards soot precursors in selected alkane and alkene flames

In this paper, we experimentally investigate the high-temperature oxidation kinetics of n-pentane, 1-pentene and 2-methyl-2-butene (2M2B) in a combustion environment using flame-sampling molecular beam mass spectrometry. The selected C 5 fuels are prototypes for linear and branched, saturated and unsaturated fuel components, featuring different C–C and C–H bond structures. It is shown that the formation tendency of species, such as polycyclic aromatic hydrocarbons (PAHs), yielded through mass growth reactions increases drastically in the sequence n-pentane < 1-pentene < 2M2B. This comparative study enables valuable insights into fuel-dependent reaction sequences of the gas-phase combustion mechanism that provide explanations for the observed difference in the PAH formation tendency. First, we investigate the fuel-structure-dependent formation of small hydrocarbon species that are yielded as intermediate species during the fuel decomposition, because these species are at the origin of the subsequent mass growth reaction pathways. Second, we review typical PAH formation reactions inspecting repetitive growth sequences in dependence of the molecular fuel structure. Third, we discuss how differences in the intermediate species pool influence the formation reactions of key aromatic ring species that are important for the PAH growth process underlying soot formation. Finally, as a main result it was found that for the fuels featuring a C=C double bond, the chemistry of their allylic fuel radicals and their decomposition products strongly influences the combination reactions to the initially formed aromatic ring species and as a consequence, the PAH formation tendency.

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

Phenalenyl growth reactions and implications for prenucleation chemistry of aromatics in flames

The energetics and kinetics of phenalene and phenalenyl growth reactions were studied theoretically. Rate constants of phenalene and phenalenyl H-abstraction and C 2 H 2 addition to the formed radicals were evaluated through quantum-chemical and rate-theory calculations. The obtained values, assigned to all π radicals, were tested in deterministic and kinetic Monte Carlo simulations of aromatics growth under conditions of laminar premixed flames. Kekulé and non-Kekulé structures of the polycyclic aromatic hydrocarbons (PAHs) evolving in the stochastic simulations were identified by on-the-fly constrained optimization. The numerical results demonstrated an increased PAH growth and qualitatively reproduced experimental observations of Homann and co-workers of non-decaying PAH concentrations with nearly equal abundances of even and odd carbon-atom PAHs. The analysis revealed that the PAH growth proceeds via alternating and sterically diverse acetylene and methyl HACA additions. Furthermore, the rapid and diverse spreading in the PAH population supports a nucleation model as PAH dimerization, assisted by the non-equilibrium phenomena, forming planar aromatics first and then transitioning to the PAH–PAH stacking with size.

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

FLAMES AND XSHOOTER SPECTROSCOPY ALONG THE TWO BLUE STRAGGLER STAR SEQUENCES OF M30

We present spectroscopic observations acquired with FLAMES and XSHOOTER at the Very Large Telescope for a sample of 15 blue straggler stars (BSSs) in the globular cluster (GC) M30. The targets have been selected to sample the two BSS sequences discovered, with seven BSSs along the blue sequence and eight along the red one. No difference in the kinematical properties of the two groups of BSSs has been found. In particular, almost all the observed BSSs have projected rotational velocities lower than {approx}30 km s{sup -1}, with only one (blue) fast rotating BSS (>90 km s{sup -1}), identified as a W UMa binary. This rotational velocity distribution is similar to those obtained in 47 Tucanae and NGC 6397, while M4 remains the only GC studied so far that harbors a large fraction of fast rotating BSSs. All stars hotter than {approx}7800 K (regardless of the parent BSS sequence) show iron abundances larger than those measured from normal cluster stars, with a clear-cut trend with the effective temperature. This behavior suggests that particle transport mechanisms driven by radiative levitation occur in the photosphere of these stars, as already observed for the BSSs in NGC 6397. Finally, four BSSs belonging to the red sequence (not affected by radiative levitation) show a strong depletion of [O/Fe], with respect to the abundance measured in red giant branch and horizontal branch stars. This O-depletion is compatible with the chemical signature expected in BSSs formed by mass-transfer processes in binary systems, in agreement with the mechanism proposed for the formation of BSSs in the red sequence.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

BROAD BALMER WINGS IN BA HYPER/SUPERGIANTS DISTORTED BY DIFFUSE INTERSTELLAR BANDS: FIVE EXAMPLES IN THE 30 DORADUS REGION FROM THE VLT-FLAMES TARANTULA SURVEY

Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

In situ temperature measurements in sooting methane/air flames using synchrotron x-ray fluorescence of seeded krypton atoms

Synchrotron x-ray fluorescence has been used to measure temperatures in optically dense gases where traditional methods would fail. These data provide a benchmark for stringent tests of computational fluid dynamics models for complex systems where physical and chemical processes are intimately linked. The experiments measured krypton number densities in a sooting, atmospheric pressure, nonpremixed coflow flame that is widely used in combustion research. The experiments not only form targets for the models, but the simulations also identify potential sources of uncertainties in the measurements, allowing for future improvements.

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

LT-LiNi 1/3 Mn 1/3 Co 1/3 O 2 : A Partially-Disordered, Composite Rock Salt Cathode Prepared by Flame Spray Pyrolysis for Li-Ion Batteries

A unique composite cathode structure for Li-ion batteries, designated LT-LiNi 1/3 Mn 1/3 Co 1/3 O 2 (or LT-NMC111), has been prepared by flame spray pyrolysis and subsequent annealing between 400 and 650 °C. It is composed predominantly of structurally-integrated and partially-disordered lithiated-spinel and layered components, both of which can be broadly described as partially-disordered rock salt constituents. The paper describes the evolution of the LT-NMC111 structure as a function of the synthesis method, annealing temperature, and electrochemical properties in the context of other recently reported “low-temperature” (LT) materials, such as LT-LiCo 1−x Al x O 2 and LT-LiMn 0.5 Ni 0.5 O 2 or, in spinel notation, LT-Li 2 Co 2–2x Al 2x O 4 and LT-Li 2 MnNiO 4 , respectively.

25 ENERGY STORAGE↗
DOE OSTI2017

Peering through the flames: imaging techniques for reacting aluminum powders

Combusting metals burn at high temperatures and emit high-intensity radiation in the visible spectrum which can over-saturate regular imaging sensors and obscure the field of view. Filtering the luminescence can result in limited information and hinder thorough combustion characterization. A method for “seeing through the flames” of a highly luminescent aluminum powder reaction is presented using copper vapor laser (CVL) illumination synchronized with a high-speed camera. A statistical comparison of combusting aluminum particle agglomerate between filtered halogen and CVL illumination shows the effectiveness of this diagnostic approach. When ignited by an electrically induced plasma, aluminum particles are entrained as solid agglomerates that rotate about their centers of mass and are surrounded by emitted, burning gases. Furthermore, the average agglomerate diameter appears to be 160 micrometers when viewed with standard illumination and a high-speed camera. But, a significantly lower diameter of 50 micrometers is recorded when imaged with CVL illumination. Our results advocate that alternative imaging techniques are required to resolve the complexities of metal particle combustion.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Recommendations on the Prediction of Thermal Hazard Distances from Large Liquefied Natural Gas Pool Fires on Water for Solid Flame Models

The objective of this work is to provide recommendations on predicting thermal hazard distances resulting from large liquefied natural gas (LNG) pool fires on water. The recommendations pertain to an integral model approach and its pertinent parameters such as burn rate, flame height, surface emissive power (SEP), and transmissivity. These recommendations are based upon knowledge gained from conducting experiments of LNG pool fires on water at Sandia National Laboratories in New Mexico in 2009 in addition to earlier, smaller scale tests. The 83 diameter meter test resulted in a 56 m diameter pool fire which is the largest LNG pool fire test performed on water or land to date.

Luketa, Anay Josephine↗
DOE OSTI2015

Development and Experimental Validation of Large Eddy Simulation Techniques for the Prediction of Combustion-Dynamic Process in Syngas Combustion: Characterization of Autoignition, Flashback, and Flame-Liftoff at Gas-Turbine Relevant Operating Conditions

The objective of this closely coordinated experimental and computational research effort is the development of simulation techniques for the prediction of combustion processes, relevant to the oxidation of syngas and high hydrogen content (HHC) fuels at gas-turbine relevant operating conditions. Specifically, the research goals are (i) the characterization of the sensitivity of syngas ignition processes to hydrodynamic processes and perturbations in temperature and mixture composition in rapid compression machines and ow-reactors and (ii) to conduct comprehensive experimental investigations in a swirl-stabilized gas turbine (GT) combustor under realistic high-pressure operating conditions in order (iii) to obtain fundamental understanding about mechanisms controlling unstable flame regimes in HHC-combustion.

10 SYNTHETIC FUELS↗