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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Technology Maturation Plan for Catalytic Membrane Reactors Based on Carbon Molecular Sieve Hollow Fiber Membranes for Sustainable and Modular H 2 Production

The overarching objective of the proposed project was to demonstrate a process-intensified approach to economically viable, modular H 2 production from waste biomass using catalytic membrane reactors (CMRs) based on carbon molecular sieve (CMS) hollow-fiber membranes. Specifically, the CMRs were developed to selectively remove H 2 during the high-temperature water-gas shift (WGS) reaction to circumvent thermodynamic limitations on converting CO to CO 2 and H 2 . To this end, our core technical activities were to (1) develop high-performance CMRs based on thermally stable, processible polymer-derived CMS membranes and (2) design and prepare new multicomponent CO 2 -tolerant nano-catalysts using a unique flame-based aerosol process for WGS reaction.

08 HYDROGEN↗
DOE OSTI2021

A surface acoustic wave hydrogen sensor with tin doped indium oxide layers for intermediate temperatures

We report high temperature surface acoustic wave (SAW) gas sensors with conducting sensing layers require tuning of the sheet conductivity for optimal response. Conducting metal oxides are attractive sensing materials for their tunable electronic properties and high thermal stability, amongst others. Here, we have investigated the application of indium oxide (IO) and indium tin oxide (ITO) films on langasite (LGS)-based SAW reflective delay line sensor devices for monitoring hydrogen at 350 °C. Specifically, we modeled the effect of the IO and ITO sensing layer thickness on the wave velocity, attenuation, and effective electromechanical coefficient. This was followed by an experimental demonstration of tuning of the ITO film sheet conductivity by controlling the dopant concentration and yielding an improvement in the sensor sensitivity. The current study provides a pathway towards the development of conductivity-based sensing layers for high temperature SAW gas sensors with improved sensitivity.

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

Initial decomposition mechanisms of 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) and their kinetic isotope effect

2,4,6-triamino-1,3,5-trinitrobenzene (TATB) is an insensitive High Explosive (HE) that is widely studied to better understand the physical properties of safety and sensitivity of HE. A dominant initial decomposition mechanism of TATB is believed to be a dehydration reaction that forms mono- and di-furazans, although other mechanisms have been reported. In this work, seven initial decomposition mechanisms were modeled with ab initio simulations to calculate its free energy barriers, decomposition rates, and kinetic isotope effects. The energy barrier for mono-benzofurazan mechanisms was found to be high, >61 kcal/mol in the gas phase; however, the reaction energy can decrease significantly in a disordered condensed state. The predicted kinetic isotope effect ratio of the furazan mechanism was found to be k h /k d ≈ 1.41 at 60K, in agreement with the experiment. The NO 2 scission mechanism was found to be an entropy-driven mechanism because the free energy barrier decreased significantly with temperature, making it the most energetically favorable mechanism at high temperatures in the gas phase. So the results provide a better understanding of the atomistic decomposition mechanisms of TATB and may be useful for improving models of safety and sensitivity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Development of mesopores in superfine grain graphite neutron-irradiated at high fluence

Microstructural changes induced by neutron irradiation of superfine grain graphite G347A (Tokai Carbon, Japan) were examined by nitrogen adsorption at 77K and by three microscopy techniques (SEM, TEM and FIB-SEM tomography). The specimens were irradiated at doses of up to 30 dpa, covering stages before and after the turnaround fluence at three temperatures (300, 450, 750 °C) of their irradiation envelope. The initial graphite densification at low fluences did not produce any detectable effect in the pore size range (<350 nm) measured by gas adsorption. However, graphite irradiated at high fluences, after turnaround, showed severe structural changes. At all three temperatures and high irradiation fluences, gas adsorption revealed significant increase of the volume of narrow mesopores (<5–20nm) and up to five times increase of BET surface area, both in linear relationship with the relative volume expansion. Analysis of microscopy images showed multiplication of fine macropores (>50 nm) at high irradiation fluences and more structural changes on multiple scales, from nanometers to microns. This work demonstrates the unique ability of gas adsorption techniques to analyze open pores with sizes between sub-nanometer and sub-micron in bulk nuclear graphite, with supporting microscopy results.

I. Contescu, Cristian↗
DOE OSTI2023

Informing and Engaging the Future Workforce on Generation IV International Forum Reactor Systems

Generation IV reactors are six nuclear reactor designs, Sodium Fast reactor (SFR), Very High Temperature Reactor (VHTR), Gas cooled Fast Reactor (GFR), Molten Salt Reactor (MSR), Lead Fast Reactor (LFR), and Supercritical Water Reactor (SCWR), that are considered to be the most promising in light of various criteria based on the following objectives: • continuation of the progress made by Generation III water reactors in terms of competitiveness and safety; • more effective use of uranium resources; • less radioactive waste, especially high-level, long-lived waste; • greater protection against malicious acts and the diversion or theft of nuclear materials. The GIF Education and Training Working Group (ETWG) launched two major initiatives in 2016 and in 2021 to not only inform and educate but also to engage the future workforce in support of these reactor systems. This paper will present an overview of the GIF EWTG webinar series as well as the 2021 Pitch your Gen IV Research Competition which is followed by the 2023 Pitch your Gen IV Research. Competition

Paviet, Patricia D.↗
DOE OSTI2020

Effects of Void Morphology on Detonation Initiation of PBX 9502

Accurate predictive modeling of high explosives in abnormal conditions, such as a fire, is critical to personnel safety. Modeling depends heavily on precise physical characterization of the high explosive in question. The aim of this thesis was to characterize the detonation response to shock and the microstructure at high-temperature (250°C) of PBX 9502 and use these data to attempt to model these results using a new reactive burn model called SURF (Scaled Uniform Reactive Front). In order to characterize the shock response of PBX 9502 at high-temperature a 1D gas gun experiment was designed and executed that provided shock to detonation transition data. These data were then used to do a preliminary calibration of SURF for PBX 9502 at 250°C. Small-angle neutron scattering (SANS) was employed to characterize the void morphology of PBX 9502 as a function of temperature. This was done in order to feed a modified version of SURF called physically informed - SURF (π-SURF) which uses the void size and quantity distribution data as measured by SANS along with the deflagration and detonation characteristics of a high explosive to inform the SURF model. The π-SURF model was then used to model both ambient and high-temperature PBX 9502 SDT response and the results were compared to the physically measured results. It was found that π-SURF works in ambient cases. At high-temperature, however, it was determined that not enough information is known about hot spot formation to use the π-SURF model for high-temperature scenarios.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2026

Sliding friction and wear behavior of nuclear graphite in high temperature inert environment: Influence of contact load, speed and temperature

Repeated dynamic interactions of graphitic components in pebble-bed gas-cooled nuclear reactors can cause abrasive wear-induced pebble surface damage, generate hazardous fine graphite debris, and alter fuel circulation dynamics due to changes in friction behavior. Comprehensive tribological characterization of nuclear graphitic materials in conditions relevant to reactor operation is needed to assess reactor long-term safety and performance. This work reports sliding friction and wear behavior of self-mated nuclear graphite ET-10 at various elevated temperatures (650 °C and 750 °C), sliding speeds (1 and 10 mm/s) and contact loads (20 and 40 N) in a controlled argon environment. The results revealed nonmonotonic frictional behavior with a higher running-in coefficient of friction (COF) followed by a lower steady-state COF, as a result of transition from two-body abrasion to three-body abrasion along with formation of a tribofilm. A key finding of this work is the sensitivity of the running-in COF to experimental conditions; maximum running-in values were lower at either elevated temperature (0.52–0.54) or reduced sliding speed (0.51–0.54). Conversely, the steady-state COF remained invariant at approximately 0.3 across all tested parameters. Transmission electron microscopy revealed a 0.5–2.0 μm thick nanocrystalline tribofilm that was thought to be formed by the compaction of the graphitic wear debris on the contact surface during the sliding process. The nanocrystalline nature of the tribofilm was further confirmed by Raman spectroscopy. As a result, the combination of tribological testing and morphological characterization provided a mechanistic understanding of the frictional behavior of nuclear graphite upon sliding.

Friction↗
DOE OSTI2023

Low-cost thermal/environmental barrier coatings: A first-principles study

Development of low-cost advanced thermal/environmental barrier coating (T/EBC) materials with acceptable thermal and mechanical properties is essential for safeguarding ceramic composites substrate against thermal and chemical degradation, thereby enhancing the efficiency of components in the high-temperature section of gas turbine engines. To this end, here we employed density functional theory-based approaches to predict the thermodynamic, mechanical, and thermal properties of rare earth disilicates based on abundant rare earth elements, namely La 2 Si 2 O 7 and Ce 2 Si 2 O 7 , as potential alternatives to the current-state-of-the-art ytterbium disilicate EBCs that uses expensive and scarce element Yb. The present study predicts that G-phase Ce 2 Si 2 O 7 has an ultralow thermal conductivity (0.26 W/m/K at 1500 K) and the apparent bulk coefficient of thermal expansion (ABCTE) (≈6.9x10 -6 K -1 ) slightly higher than SiC, demonstrating great potential as low-cost high-performance T/EBC. However, La 2 Si 2 O 7 and Ce 2 Si 2 O 7 undergo an A- to G-phase polymorphic transition at around 1470 K, resulting in significant changes to crystal structure and lattice parameters, and accordingly CTE and lattice thermal conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Limited impact of jet-induced feedback in the multi-phase nuclear interstellar medium of 4C12.50

4C12.50 (IRAS 13451+1232) at z = 0.122 is an ultraluminous infared radio galaxy that has often been proposed as a prime candidate for the link between ultraluminous infared galaxies and young radio galaxies. It is also an interesting target to investigate whether and how radio-induced feedback affects the evolution of galaxies in the early phases of radio activity. We study, in detail for the first time, the hot (≥1500 K) molecular gas in 4C12.50. The potential impact of the radio jet on this gas phase, as well as on the star formation activity, are investigated. We also study the ionised (including coronal) gas as traced by the near-infrared lines. Using near-infrared long slit spectroscopy obtained with EMIR on GTC and X-shooter on VLT, we analyse the emission line spectrum of the ionised, coronal, and, specially, the hot molecular gas in the western nucleus hosting the compact radio jet. Based on high spatial resolution ALMA CO(2–1) data, we also revise the location of 4C12.50 in the Kennicutt-Schmidt diagram in order to investigate whether star formation is suppressed. 4C12.50 hosts (2.1 ± 0.4) × 10 4 M ⊙ of hot molecular gas. An unusually high rotational temperature T rot = 3020 ± 160 K is inferred. The molecular gas mass obeys a power-law temperature distribution, dM H2 /dT ∝ T –5 , from T ~300 K and up to ~3000 K. Both results support the idea that shocks (probably induced by the radio jet) contribute to the heating and excitation of the hot molecular gas. A molecular outflow is not detected. The coupling of the outflowing ionised and neutral outflows with the hot molecular gas is poor. Contrary to other studies, we claim that there is no evidence for star formation suppression in this object. If radio-induced feedback can regulate the star formation activity in galaxies, 4C12.50 is a promising candidate to reveal this phenomenon in action. However, we find no solid evidence for a current or past impact of this mechanism on the evolution of this system, neither by clearing out the dusty central cocoon efficiently, nor by suppressing the star formation activity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

A direct contact cooler design for simultaneously recovering latent heat and capturing SO x and NO x from pressurized flue gas

Integrated SO x and NO x removal technology using a direct contact cooler is a promising alternative for cleaning coal combustion flue gas, especially for pressurized combustion systems. Past investigations of integrated SO x and NO x removal have been limited to low-temperature processes, where the flue gas has been cooled upstream of the removal unit, and the moisture in the flue gas has been condensed out. Here this work presents a novel design that recovers the flue gas heat while simultaneously removing SO x and NO x in a single reactive-absorption column – direct contact cooler. A validated model was used to evaluate different direct contact cooler designs. Modeling results suggested that a counter-current column with a single water inlet can scrub 83% of the NO x and 96.5% of the SO x in 115 s, while an optimized design with multiple water inlets enhances the scrubbing of NO x by 9 percentage points and SO x by 3.5 percentage points, due to a 34% increase in residence time. It is also observed that the liquid-phase reaction between absorbed SO x and NO x plays a significant role in the removal of SO 2 from the flue gas for high-temperature scrubbing compared with low-temperature scrubbing. The design reinforces the potential of high-temperature SO x -NO x removal and heat recovery and suggests a means of reducing capital costs for such columns.

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

Development of Additive Manufacturing for Ceramic Matrix Composite Vanes

This report discusses the development of additive manufacturing for polymer-derived ceramic materials to create novel cooled gas turbine airfoils made from ceramics. Gas turbine engines have extremely high temperatures in the hot section of the engine that exceed the melting point of nickel superalloy materials that the engine is made from. Advanced cooling technologies have been developed over decades for metallic parts. Ceramic materials have higher temperature capabilities than superalloys, but are difficult to shape in the complex designs used in modern turbines. Several thrusts were investigated during the project, including development of higher material strength resins, improvement of ultraviolet (UV) photopolymerization and post-processing techniques to increase survivability of ceramic parts, thermomechanical modeling of novel ceramic airfoil designs for higher cooling effectiveness, and experimental validation of the modeling and manufacturing in a turbine vane test facility at nondimensional conditions that are relevant to modern gas turbines. Some major findings of the work include a significant increase in ceramic survivability during pyrolysis (a high temperature process that converts the organic material to a ceramic) by adjusting the composition ratios of the resins, as well as a tolulene soak after printing to remove unreacted polymer material. Thermomechanical optimization of the internal cooling structure indicated that a high density pin fin array would enable an 80% increase in overall cooling effectiveness relative to a baseline geometry, which was later verified during experimental testing in a high speed linear cascade. Ceramic vanes were tested at Mach numbers of up to 0.9 which is relevant to modern gas turbines. High temperature capability of the ceramic vanes was not tested in this work.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Direct Conversion of Methane to Ethylene and Acetylene over an Iron-Based Metal–Organic Framework

Conversion of methane (CH 4 ) to ethylene (C 2 H 4 ) and/or acetylene (C 2 H 2 ) enables routes to a wide range of products directly from natural gas. However, high reaction temperatures and pressures are often required to activate and convert CH 4 controllably, and separating C 2+ products from unreacted CH 4 can be challenging. Here, we report the direct conversion of CH 4 to C 2 H 4 and C 2 H 2 driven by non-thermal plasma under ambient (25 °C and 1 atm) and flow conditions over a metal–organic framework material, MFM-300(Fe). The selectivity for the formation of C 2 H 4 and C 2 H 2 reaches 96% with a high time yield of 334 μmol g cat –1 h –1 . At a conversion of 10%, the selectivity to C 2+ hydrocarbons and time yield exceed 98% and 2056 μmol g cat –1 h –1 , respectively, representing a new benchmark for conversion of CH 4 . In situ neutron powder diffraction, inelastic neutron scattering and solid-state nuclear magnetic resonance, electron paramagnetic resonance (EPR), and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modeling studies, reveal the crucial role of Fe–O(H)–Fe sites in activating CH 4 and stabilizing reaction intermediates via the formation of an Fe–O(CH 3 )–Fe adduct. In addition, a cascade fixed-bed system has been developed to achieve online separation of C 2 H 4 and C 2 H 2 from unreacted CH 4 for direct use. Integrating the processes of CH 4 activation, conversion, and product separation within one system opens a new avenue for natural gas utility, bridging the gap between fundamental studies and practical applications in this area.

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

Identification of Suitable Vacuum Gas Oils as Plasticizers Using HT-GC × GC-HRMS

Vacuum gas oils (VGOs) have long been heralded as effective plasticizers due to their high boiling-points and lubricating properties. One of these VGOs, HyVac Oil 93050, is a paraffinic plasticizer that is currently utilized in polymer–plasticizer explosive formulations, while this oil effectively increases the elasticity and decreases the sensitivity for current formulations. We seek to identify alternative VGOs with similar density, viscosity, molecular composition, and impurities for future formulations. In this study, 18 VGOs, including HyVac Oil 93050, were initially evaluated for their density and viscosity. The oils were then ranked based on physical characteristics and analyzed for molecular composition using high-temperature comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry (HT-GC × GC-HRMS). Further, the HT-GC × GC-HRMS chromatograms of the top 10 most similar VGOs to HyVac Oil 93050, according to density, were compared utilizing the Pearson correlation coefficient. Three of the oils with densities similar to those of HyVac Oil 93050 had a Pearson correlation within the lot-to-lot variation of HyVac Oil 93050. For the top 3 candidates, Pearson correlation was then utilized as a feature selection technique to discover significant chemical differences. Positive chemical ionization (PCI) and negative chemical ionization (NCI) HT-GC × GC-HRMS chromatograms were also evaluated and aided in the discovery and identification of several key compounds including additives that acted as stabilizers for the VGOs. After this further chemical analysis, two of the original 17 potential VGOs were determined to be physically and chemically similar to HyVac Oil 93050.

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

Novel Segregated Solid Propulsion System with Separately Stored Fuel and Oxidizer

Abstract The development and experimentation of a solid propulsion concept consisting of separate hydrogen‐rich solid propellant and solid oxidizer grains is presented. This system consists of an extremely fuel‐rich solid propellant, which, once ignited, undergoes a self‐sustaining decomposition to release fuel‐rich product gases, which are particularly rich in hydrogen gas. These relatively high‐temperature gases subsequently react with a solid oxidizer grain stored downstream. Progress in high‐nitrogen materials has allowed for the synthesis of fuel‐rich compounds that can store significant amounts of hydrogen, with little or no bound oxygen. With these new developments in propellant chemistry, a unique segregated propulsion system has been developed, creating an all‐solid propulsion system that combusts analogously to a reverse hybrid rocket system. Because of the physical separation of fuel and oxidizer, a higher level of safety is achieved which concurrently allows for the utilization of higher energy ingredients without the penalty of higher sensitivity. Theoretical performance calculations and experimental data have shown the potential for this system to compete with existing composite rocket propellants while having significant benefits in terms of safety, toxicity, and mission space. This paper presents a detailed overview of the conception, development, and testing of this propulsion system.

42 ENGINEERING↗
DOE OSTI2024

Reaction Pathways and Energy Consumption in NH 3 Decomposition for H 2 Production by Low Temperature, Atmospheric Pressure Plasma

Pathways for NH 3 decomposition to N 2 and N 2 H 4 by atmospheric pressure nonthermal plasma are analyzed using a combination of molecular beam mass spectrometry measurements and zero-dimensional kinetic modeling. Experimental measurements show that NH 3 conversion and selectivity towards N 2 formation scale monotonically with the specific energy input into the plasma with ~ 100% selectivity to N 2 formation achieved at specific energy inputs above 0.12 J cm −3 (3.1 eV (molecule NH 3 ) −1 ). The kinetic model recovers these trends, although it underpredicts N 2 selectivity at low specific energy input. These discrepancies can be explained by the underestimation of reaction rate coefficients for reactions that consume N 2 H x species in collisions with H radicals and/or radial nonuniformities in power deposition, gas temperature, and species concentrations that are not represented by the plug flow approximation used in the model. The kinetic model shows that N 2 formation proceeds through N 2 H x decomposition pathways rather than NH x decomposition pathways in low temperature, atmospheric pressure plasma. Higher selectivity toward N 2 production can be achieved by operating at higher NH 3 conversion and with a higher gas temperature. Furthermore, the high energy cost of NH 3 decomposition by atmospheric pressure nonthermal plasma found in this work (25–50 eV (molecule NH 3 converted) −1 ; 17–33 eV (molecule H 2 formed) −1 ) is a result of the energy requirement for electron-impact dissociation of NH 3 and the significant re-formation of NH 3 by three-body recombination reactions between NH 2 and H.

Nonthermal plasma↗
DOE OSTI2021

Steep sulfur gradient in CZTSSe solar cells by H 2 S-assisted rapid surface sulfurization

Sulfur/selenium grading is a widely used optimization strategy in kesterite thin-film solar cells to obtain a bandgap-graded absorber material and to optimize optical and electrical properties of the solar-cell device. In this work, we present a novel approach to introduce a [S]/([S] + [Se]) grading for Cu 2 ZnSn(S,Se) 4 solar cells. In contrast to commonly used methods with slow process dynamics, the presented approach aims to create a fast sulfurization reaction on the surface of pure selenide kesterite absorbers by using highly reactive H 2 S gas and high sulfurization temperatures in a rapid flash-type process. With a combination of X-ray photoelectron spectroscopy, X-ray emission spectroscopy, Raman spectroscopy, and Raman-shallow angle cross sections spectroscopy, we gain depth-varied information on the [S]/([S] + [Se]) ratio and discuss the impact of different process parameter variations on the material and device properties. The results demonstrate the potential of the developed process to generate a steep gradient of sulfur that is confined mainly to the surface region of the absorber film.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗