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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Handling Procedures of Vegetable Crops

The National Aeronautics and Space Administration (NASA) is working towards future long duration manned space flights beyond low earth orbit. The duration of these missions may be as long as 2.5 years and will likely include a stay on a lunar or planetary surface. The primary goal of the Advanced Food System in these long duration exploratory missions is to provide the crew with a palatable, nutritious, and safe food system while minimizing volume, mass, and waste. Vegetable crops can provide the crew with added nutrition and variety. These crops do not require any cooking or food processing prior to consumption. The vegetable crops, unlike prepackaged foods, will provide bright colors, textures (crispy), and fresh aromas. Ten vegetable crops have been identified for possible use in long duration missions. They are lettuce, spinach, carrot, tomato, green onion, radish, bell pepper, strawberries, fresh herbs, and cabbage. Whether these crops are grown on a transit vehicle (e.g., International Space Station) or on the lunar or planetary surface, it will be necessary to determine how to safely handle the vegetables while maintaining acceptability. Since hydrogen peroxide degrades into water and oxygen and is generally recognized as safe (GRAS), hydrogen peroxide has been recommended as the sanitizer. The objective of th is research is to determine the required effective concentration of hydrogen peroxide. In addition, it will be determined whether the use of hydrogen peroxide, although a viable sanitizer, adversely affects the quality of the vegetables. Vegetables will be dipped in 1 % hydrogen peroxide, 3% hydrogen peroxide, or 5% hydrogen peroxide. Treated produce and controls will be stored in plastic bags at 5 C for up to 14 days. Sensory, color, texture, and total plate count will be measured. The effect on several vegetables including lettuce, radish, tomato and strawberries has been completed. Although each vegetable reacts to hydrogen peroxide differently, the data suggest that 5% hydrogen peroxide reduces the shelf life of the vegetable. A dip of either 1 % or 3% hydrogen peroxide helps reduce the microbial total count while not adversely affecting the quality of the vegetable.

Perchonok, Michele↗
NASA NTRS1991

Energy degradation of fast electrons in hydrogen gas

An equation is derived for calculating the energy distribution of fast electrons in a partially ionized gas and a method is provided to solve for the electron degradation spectrum and the energy deposition in different forms (ionization, excitation, or heating). As an example, the energy degradation of fast electrons in a gas of pure hydrogen is calculated, considering excitations to the lowest 10 atomic levels. The Bethe approximation and the continuous slowing-down approximation are discussed and it is concluded that these approximations are accurate to the order of 20 percent for electrons with initial energy of greater than about keV. The method and results can be used to determine heating, excitations, and ionizations by high-energy photoelectrons or cosmic-ray particles in various astrophysical circumstances, such as the interstellar medium, supernova envelopes, and QSO emission-line clouds.

Xu, Yueming↗
DOE OSTI2022

High energy X-ray diffraction and small-angle scattering measurements of hydrogen fatigue damage in AISI 4130 steel

Accurate lifetime predictions are critical for repurposing existing pipelines for hydrogen transmission as well as for developing novel steels which are minimally susceptible to lifetime degradation by hydrogen. Ultimately, lifetime prediction models assess the amount of damage a material undergoes during a typical service cycle and the cumulative damage a material can withstand prior to failure. However, not all damage processes are equal, and neither is the manner in which mechanical loading translates to damage the same when materials are in inert environments compared to in hydrogen environments. For example, in the three leading proposed mechanisms of hydrogen embrittlement (Hydrogen-Enhanced Decohesion (HEDE), the Hydrogen-Enhanced Localized Plasticity (HELP), and the Nano-Void Coalescence (NVC)), hydrogen is proposed to enhance the manifestation of grain separation, dislocation generation/movement, and void coalescence, respectively. A full understanding of the damage modes requires a measurement capable of probing all three mechanisms at once. Here we present simultaneous High Energy X-ray Diffraction (HEXRD) and Small-Angle X-ray Scattering (SAXS) during fatiguing of steel in hydrogen. HEXRD measurements probe strain and dislocation density; SAXS measurements probe nano-pore generation and coalescence. We will discuss the differences in damage modes between steels fatigued in air and in hydrogen and the role these difference play in lifetime predictions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electrochemical pumping: An alternative solution for hydrogen embrittlement

Hydrogen embrittlement is a form of chemo-mechanical damage that is special in that it can be partially reversible. Here, in this paper, we propose a method for recovering structural alloys from hydrogen embrittlement at room temperature by electrochemically biased desorption of hydrogen. We demonstrate that the method can enable the reversion of hydrogen-induced degradation of mechanical properties, by comparing the mechanical behavior of commercial stainless steel specimens at different hydrogen charging and desorption states. These case studies also reveal the influence of electrochemical potential, H content and the characteristics of H trapping sites, on the effectiveness of this recovery approach. The limitations arising from the presence of unhealable forms of hydrogen damage, and the generic applicability of this electrochemically-assisted recovery method are also discussed.

36 MATERIALS SCIENCE↗
NASA NTRS1986

A new high strength alloy for hydrogen fueled propulsion systems

This paper describes the development of a high-strength alloy (1241 MPa ultimate and 1103 MPa yield, with little or no degradation in hydrogen) for application in advanced hydrogen-fueled rocket engines. Various compositions of the Fe-Ni-Co-Cr system with elemental additions of Cb, Ti and Al are discussed. After processing, notched tensile specimens were tested in 34.5-MPa hydrogen at room temperature, as the main screening test. The H2/air notch tensile ratio was used as the selection/rejection criterion. The most promising alloys are discussed.

Mcpherson, W. B.↗
DOE OSTI2024

Polystyrene Hydrogenolysis to High-Quality Lubricants Using Ni/SiO 2

Pyrolytic and light-activated oxidation processes are leading technologies for utilizing polystyrene (PS) wastes. These approaches exhibit poor selectivities, use complex reactors, and require solvents. Hydrogenolysis is effective for deconstructing polyolefins, but its application to PS feedstocks has been limited. Herein, we demonstrate Ni/SiO 2 catalysts to facilitate PS (M w ≈ 97 kDa) hydrogenolysis to produce lubricant base oils possessing group IV properties, achieving maximum yields of 70% within 6 h at 300 °C and 70 bar of H 2 . Gas, liquid, and oil product yields are stable across reaction conditions, whereas hydrogenation of the PS aromaticity and reduction of the molecular weight benefit from higher temperatures and H 2 pressures. Time-dependent experiments underscore the importance of elevated H 2 pressure, revealing that PS hydrogenolysis occurs sequentially, with aromatic ring hydrogenation preceding degradation of the C–C backbone. Kinetic measurements with 1,2-diphenylethane as a probe molecule demonstrate that ring hydrogenation pis 3 orders of magnitude faster than internal C–C bond cleavage over Ni/SiO 2 . Ni/SiO 2 proves to be effective in the hydrogenolysis of heavier PS polymers and rigid commercial PS products. Conversely, flexibility and foam PS feeds result in Ni/SiO 2 deactivation, attributed to performance additives. Unlike polyolefins, the process produces very little methane and other light hydrocarbons. Furthermore, these findings expand the applicability of hydrogenolysis to PS feedstocks, offering a versatile solution and broadening the range of high-value products from PS to include lubricant base oils.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1975

Hydrogen environment embrittlement of astroloy and Udimet 700 (nickel-base) and V-57 (iron-base) superalloys

The sensitivity to hydrogen environment embrittlement of three superalloys was determined. Astroloy forgings were resistant to embrittlement during smooth tensile, notched tensile, and creep testing in 3.5-MN/sq m hydrogen over the range 23 to 760 C. The notched tensile strength of Udimet 700 bar stock in hydrogen at 23 C was only 50 percent of the baseline value in helium. Forgings of V-57 were not significantly embrittled by hydrogen during smooth tensile testing over the range 23 to 675 C; creep and rupture lives of V-57 were degraded by hydrogen. Postcreep tensile ductility of V-57 was reduced by 40 percent after creep exposure in hydrogen.

Gray, H. R.↗
NASA NTRS1991

The effect of porosity and gamma-gamma-prime eutectic content on the fatigue behavior of hydrogen charged PWA 1480

The study addresses the effect of systematically varying gamma-gamma-prime eutectic content and porosity level on the fatigue life of a hydrogen-charged single crystal PWA 1480 superalloy. Four microstructural variants are produced, and differences in gamma-gamma-prime eutectic morphology among the four processing variants are analyzed. Single valued tensile test data indicate that the tensile and yield strength of the PWA 1480 are degraded by hydrogen charging, with the exception of the material given a eutectic solution treatment. It is shown that the reduction of the fatigue life can be minimized by a duplex thermomechanical treatment consisting of a eutectic solution followed by hot isostatic pressing.

Gayda, J.↗
DOE OSTI2022

UV‐induced degradation of high‐efficiency silicon PV modules with different cell architectures

Abstract Degradation from ultraviolet (UV) radiation has become prevalent in the front of solar cells due to the introduction of UV‐transmitting encapsulants in photovoltaic (PV) module construction. Here, we examine UV‐induced degradation (UVID) in various commercial, unencapsulated crystalline silicon cell technologies, including bifacial silicon heterojunction (HJ), interdigitated back contact (IBC), passivated emitter and rear contact (PERC), and passivated emitter rear totally diffused (PERT) solar cells. We performed UV exposure tests using UVA‐340 fluorescent lamps at 1.24 W·m −2 (at 340 nm) and 45°C through 4.02 MJ·m −2 (2000 h). Our results showed that modern cell architectures are more vulnerable to UVID, leading to a significant power decrease (−3.6% on average; −11.8% maximum) compared with the conventional aluminum back surface field (Al‐BSF) cells (<−1% on average). The power degradation is largely caused by the decrease in short‐circuit current and open‐circuit voltage. A greater power decrease is observed in bifacial cells with rear‐side exposure compared with those with front‐side exposure, indicating that the rear side is more susceptible to UV damage. Secondary ion mass spectroscopy (SIMS) confirmed an increase in hydrogen concentration near the Si/passivation interface in HJ and IBC cells after UV exposure; the excess of hydrogen could result in hydrogen‐induced degradation and subsequently cause higher recombination losses. Additionally, surface oxidation and hot‐carrier damage were identified in PERT cells. Using a spectral‐based analysis, we obtained an acceleration factor of 5× between unpackaged cells (containing a silicon nitride antireflective coating on the front) in the UV test and an encapsulated module (with the front glass and encapsulant blocking 90% of the UV at 294 nm and 353 nm, respectively) in outdoor conditions. From the analytical calculations, we show that a UV‐blocking encapsulant can reduce UV transmission in the module by an additional factor of ~50.

14 SOLAR ENERGY↗
DOE OSTI2024

A Multifunctional Isostructural Bilayer Oxygen Evolution Electrode for Durable Intermediate-Temperature Electrochemical Water Splitting

The overarching goal of the proposed research is to address SOEC’s degradation problem by advancing a new isostructural highly electrocatalytically active bilayer oxygen evolution reaction (OER) electrode, consisting of a LSCF (La 1-x Sr x Co 1-y Fe y O 3-δ ) core and a SCT (SrCo 0.9 Ta 0.1 O 3-δ ) shell, to achieve high and sustainable rate of oxygen evolution matching operating current densities without encountering delamination. To realize this goal, the project has adopted a combined experimental and theoretical approach to conduct research in the following six areas closely associated with SOPO tasks: 1) Development of electrocatalytically active bilayer oxygen electrodes (SOPO task-1) 2) Development of new symmetric three electrode cell (STEC) methodology to extract electrokinetic data of oxygen electrodes (SOPO task-2) 3) Quantification of electrokinetics of bilayer oxygen electrodes and correlation with degradation and delamination (SOPO task-2) 4) Performances of bilayer oxygen electrodes under fuel cells and electrolyzers modes (SOPO task-3) 5) Microscale modeling of oxygen electrode/electrolyte interface in solid oxide electrolysis cells (SOPO task-4) 6) Prediction of crack growth rate at oxygen electrode/electrolyte interface in solid oxide electrolysis cells (SOPO task-4)

08 HYDROGEN↗
DOE OSTI2021

Effect of Nanoscale Ce 0.8 Gd 0.2 O 2–δ Infiltrant and Steam Content on Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 Fuel Electrode Degradation during High-Temperature Electrolysis

Studies of Ni–yttria-stabilized zirconia (YSZ) fuel electrode degradation mechanisms in solid oxide electrolysis cells (SOECs) are complicated by the different possible Ni–YSZ microstructures and compositions, and the variations in the H 2 /H 2 O ratio encountered in an electrolysis stack. Here, in this study, we describe a life testing scheme aimed at providing survey results on degradation as a function of the H 2 O–H 2 composition, with life tests carried out at five different steam contents from 90% to 10%. A Ni–YSZ-supported symmetric cell geometry is employed both with and without infiltrated nanoscale gadolinia-doped ceria (GDC). Impedance spectroscopy is utilized to observe changes in electrochemical characteristics during the life test, and a transmission-line-based equivalent circuit is used to model the data. Post-test electrode microstructures were observed. The results suggest that the GDC infiltrant reduces the electrode polarization resistance and provides more stable electrode polarization over a range of conditions.

08 HYDROGEN↗
DOE OSTI2022

Multi-scale imaging of high-pressure hydrogen induced damage in EPDM rubber using X-ray microcomputed tomography, helium-ion microscopy and transmission electron microscopy

Ethylene propylene diene (EPDM) rubber has gained increasing interest for use in hydrogen infrastructure due to its excellent sealing performance and low temperature properties. However, severe structural damage has been observed in EPDM O-rings after exposure to high-pressure hydrogen. The origination and propagation mechanisms of this damage are poorly understood. Here, to address this knowledge gap, multi-scale imaging leveraging X-ray micro-computed tomography (micro-CT), helium ion microscopy (HeIM), and transmission electron microscopy (TEM) were used in this work to study a series of sulfur-cured ethylene propylene diene (EPDM) rubber materials with varying additives that were exposed to different hydrogen environments. Micro-CT captured the substantial structural damage due to hydrogen exposure; it revealed an association between zinc oxide (ZnO) particles and damage initiation. Further studies by TEM and scanning TEM with energy dispersive X-ray spectroscopy (EDS) were focused on these particles at the micro-to nano-scale range. TEM indicated that hydrogen causes void formation at the interface between ZnO and the rubber matrix. HeIM enabled imaging of surface morphology of the material at high resolution pre- and post-hydrogen exposure while providing information on chemical composition and that cannot be captured by either micro-CT or TEM.

08 HYDROGEN↗
DOE OSTI2022

Elucidating the Reaction Pathways of Veratrylglycero-β-Guaiacyl Ether Degradation over Metal-Free Solid Acid Catalyst with Hydrogen

Efficient cleavage of β-O-4 bonds in lignin to high-yield aromatic compounds for the potential production of fuels and chemicals is vital for the economics of the modern biorefinery industry. This work is distinct in that a detailed mechanistic analysis of the reaction pathways of veratrylglycero-β-guaiacyl ether (VGE) catalyzed by transition-metal-free solid acid zeolite in aqueous conditions at high hydrogen pressure has been performed. VGE degradation produced high monomers yields (≈87 %), including guaiacol (48.2 %), 1-(3,4-dimethoxyphenyl)ethanol (10.3 %), 1-(3,4-dimethoxyphenyl)-2-propanol (6.1 %), 3,4-dimethoxyphenylpropanol (4.7 %), 3,4-dimethoxycinnamyl alcohol (4.1 %), and 1,2-dimethoxy-4-propylbenzene (2 %). The products were identified and confirmed by the in situ solid-state magic angle spinning (MAS) 13 C NMR spectroscopy in real-time conditions and the two-dimensional gas chromatography (GC×GC). A variety of products reveal the crucial role of hydrogen, water, and acid sites for heterolytic cleavage of the β-O-4 bond in VGE. Decarbonylation, hydrogenolysis, hydrogenation, and dehydration reaction pathways are proposed and further validated using first-principles calculations.

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

Modeling Ni Coarsening and Migration in the Hydrogen Electrode of Solid oxide Cells under Operating Conditions

Ni coarsening and migration is the most important degradation in the hydrogen electrode of solid oxide cells. This presentation reviews our works on Ni coarsening and migration in NETL over the past years. We used simulation techniques including phase-field modeling and density function theory to investigate possible mechanisms of Ni coarsening and migration, including self-diffusion of Ni, diffusion of gaseous Ni(OH)2, surface diffusion of Ni(OH)x and Ni-YSZ wettability change, and examined the effect of operating conditions on these mechanisms. So far, none of the mechanisms can fully explain the experiments. Remaining questions and possible paths forward are summarized and discussed.

Lei, Yinkai↗
DOE OSTI2023

The Impact of Oxidation-Induced Degradation On Materials Used in Hydrogen-Fired Microturbines

Hydrogen-fueled microturbines are being considered as part of the future green microgrid. However, the use of hydrogen as a fuel presents new challenges for selection and development of suitable high temperature materials for hydrogen combustion. The burning of hydrogen is expected to result in higher operating temperatures and higher than typically observed water vapor contents in exhaust gases versus burning natural gas. In the present work, foil specimens of various Fe- and Ni-based alloys were oxidized in air + 10 % H 2 O and air + 60% H 2 O for up to 5,000 h at 700 °C to simulate the exhaust atmosphere of natural gas and hydrogen-fueled microturbines. Here, the impact of alloy composition and water vapor content on the oxidation/ volatilization induced loss of wall thickness was experimentally evaluated. Enhanced external oxidation and volatilization of Cr 2 O 3 and Ti-doped Cr 2 O 3 scales was observed in air + 60% H 2 O compared to air + 10% H 2 O. No significant impact of the higher water vapor content was observed on Al 2 O 3 scales formed on Fe-based alumina forming alloys. Lifetime modeling was employed to predict the combined effects of water vapor content, gas flow rates, temperature and alloy composition on the oxidation-induced lifetime of the investigated materials.

36 MATERIALS SCIENCE↗