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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Identifying higher oxygenate synthesis sites in Cu catalysts promoted and stabilized by atomic layer deposited Fe 2 O 3

The conversion of syngas to higher oxygenates is an important step in the pathway towards the long-term sustainable production of fuels and chemicals. Mixed Cu/Fe catalysts combine metals with different CO activation characteristics, a property that makes them promising candidates for higher oxygenate production. However, Cu/Fe catalysts suffer from instability due to sintering and phase separation, and the active sites for higher oxygenate formation on these materials are not well understood. In this work, we use atomic layer deposition (ALD) to modify silica-supported Cu nanoparticles with monolayer precise amounts of Fe 2 O 3 and study the effects on catalyst structure, reactivity, and stability. We demonstrate that the Fe 2 O 3 ALD process is inherently selective towards deposition on the SiO 2 surface versus the Cu nanoparticles. As a result, a sufficiently thick Fe 2 O 3 layer surrounding the Cu nanoparticles acts as a barrier against Cu migration, preventing catalyst deactivation through sintering without covering the Cu. In syngas conversion reactions, we find that higher oxygenate selectivity increases with Fe 2 O 3 loading at low and intermediate ALD cycle numbers. Furthermore, using in situ X-ray absorption spectroscopy, we demonstrate that the Fe near the Cu nanoparticles is reduced to a metallic state under reaction conditions. From these measurements, we identify these metallic Cu/Fe interfaces as the active sites for higher oxygenate formation, which are most abundant at intermediate Fe 2 O 3 ALD cycle numbers. As the Fe 2 O 3 loading increases, higher oxygenate selectivity falls, resulting from encapsulation of the Cu nanoparticles by thick Fe 2 O 3 layers. Overall, the results demonstrate how thickness-controlled ALD Fe 2 O 3 can be used as both a promoter and stabilizer of Cu-based higher oxygenate synthesis catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Selective and Stable Ethanol Synthesis via Electrochemical CO 2 Reduction in a Solid Electrolyte Reactor

Electrochemical CO 2 reduction to ethanol faces challenges such as low selectivity, a product mixture with liquid electrolyte, and poor catalyst/reactor stability. Here, we developed a grain-rich zinc-doped Cu 2 O precatalyst that presented a high ethanol Faradaic efficiency of over 40% under a current density of 350 mA·cm –2 . Our density functional theory (DFT) simulation suggested that Zn atoms inside the structure have a greater carbophilicity than the Cu atoms to help facilitate *CHCHO formation, a key reaction intermediate toward ethanol instead of other C 2 products. Here, a high Faradaic efficiency ratio between ethanol and ethylene (FE EtOH /FE C2H4 ) reached 2.34 in the zinc-doped Cu 2 O precatalyst, representing an over 4-fold improvement compared to bare Cu 2 O precatalyst. By integrating this Cu-based catalyst into a porous solid electrolyte (PSE) reactor with a salt-managing design, we achieved stable ethanol production for over 180 h under a current density of 250 mA·cm –2 while maintaining ethanol selectivity at ~30%.

09 BIOMASS FUELS↗
DOE OSTI2026

Selective Reduction of Carbon Dioxide in Water Using [M(bpy2+)(CO)3(I)]2+ (M = Mn, Re) Electrocatalysts with Pendent Cations

Manganese(I) carbonyl complexes are promising electrocatalysts for CO2 reduction, yet their application in homogeneous aqueous media remains limited by poor solubility and selectivity. Here, we report water-soluble Mn(I) and Re(I) complexes fac-[M(bpy2+)(CO)3X]2+ (X = I or Cl), featuring bipyridine ligands functionalized with -Ph-CH2-(NMe3)+ cationic ammonium groups that integrate water solubility with secondary-sphere stabilization. In bicarbonate buffer at pH 6.8, the Mn catalyst is completely selective for CO production at a low overpotential (η = 0.3 V), operating by a protonation-first mechanism with observed rates of ~10 s−1. Pulse radiolysis reveals that the one-electron reduced Mn species undergoes dimerization in the absence of CO2 but uniquely reacts competitively with CO2 through an initial pre-equilibrium followed by fast formation of a dinuclear CO2-bridged species (ΔGo = −12.4 kcal mol−1). At a higher 0.6 V over-potential, a faster reduction-first pathway (~100 s−1) is available upon reduction of the metallo-carboxylic acid intermediate, Mn-CO2H2+; however, this regime is functionally limited by the formation of a resistive, noncatalytic film on the electrode surface. Comparison to the analo-gous water-soluble Re catalyst (kobs = 440 s−1, η = 0.6 V) highlights the distinct mechanistic ad-vantages of earth-abundant Mn in low-potential catalysis. These results demonstrate how cati-onic second-sphere design enables selective, homogeneous CO2 reduction in water while reveal-ing competing radical and electrode-mediated processes that govern catalytic performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis, Electronic Structure, and Reactivity of a Planar Four‐Coordinate, Cobalt–Imido Complex

Abstract A four‐coordinate cobalt–imido complex, ( t Bu mPNP)Co=NMes ( t Bu mPNP=modified PNP pincer ligand) has been synthesized from addition of 2,4,6‐trimethylphenylazide (Mes–N 3 ) to the corresponding dinitrogen complex. The solid‐state structure determined by X‐ray diffraction established a rare, idealized planar geometry with a Co=N bond distance of 1.716(2) Å. Magnetic measurements revealed an S =1 ground state with CAS‐SCF calculations supporting radical character on the imide nitrogen. Thermolysis of the cobalt–imido compound induced selective insertion of the imido group into a Co−P bond and yielded a three‐coordinate cobalt complex with a distorted T‐shaped geometry. Transition state analysis conducted with DFT calculations established the thermodynamic stability of the P–N coupled product and provided insight into the exclusive selectivity.

Park, Yoonsu↗
DOE OSTI2019

Highly Selective Heterogeneous Ethylene Dimerization with a Scalable and Chemically Robust MOF Catalyst

Metal–organic frameworks (MOFs) hold great promise as structurally tunable catalysts capable of high selectivity in the solid state, yet their comparatively high cost and often limited stability remain significant concerns for their commercialization as heterogeneous catalysts. In this paper, we report detailed X-ray absorption spectroscopy studies of Co- and Ni-MFU-4$l$, a class of highly selective MOF catalysts for olefin upgrading, and reveal mechanisms that lead to their deactivation. We further show that Ni-CFA-1, a more scalable and economical alternative to Ni-MFU-4l, reproduces both the local coordination structure and the high selectivity of the latter in ethylene dimerization catalysis. Under optimal conditions, Ni-CFA-1 activated by MMAO-12 achieves a turnover frequency of 37100 per hour and a selectivity of 87.1% for 1-butene, a combination of activity, selectivity, and affordability that is unmatched among heterogeneous ethylene dimerization catalysts. Ni-CFA-1 retains its high activity for at least 12 h in a one-liter semibatch reactor, offering a strategy toward robust and scalable MOFs for industrial catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

Design and pilot evaluation of the RAH-66 Comanche selectable control modes

The RAH-66 Comanche helicopter has been designed to possess superior handling qualities over a wide range of flight conditions. The control laws have been tailored to satisfy the requirements of ADS-33C and the Weapon System Specification (WSS). This paper addresses the design of the Comanche Selectable Mode control laws (Velocity Stabilization/Hover Hold and Altitude Hold), which provide the additional stabilization and control augmentation needed when flying in a Degraded Visual Environment (DVE). An overview of the RAH-66 control laws is presented, including a detailed description of the Selectable Modes design. The primary focus of this paper is the results of piloted evaluation of these control laws in the Boeing motionbase simulator. These tests substantiate the detailed design of the Comanche Selectable Mode control laws. All tested DVE tasks (ADS-33C, sections 4.4 and 4.5) were rated Level 1. Other evaluation tasks confirmed the mission suitability of the control system. These control laws are ready for formal ADS-33C compliance testing in the Sikorsky Full Mission Simulator (FMS).

Phillip J Gold↗
DOE OSTI2026

Evolution of size-selected Pt cluster catalysts on prototypical oxide supports

The current quest for new pathways into sustainable, efficient and durable energy conversion technologies makes the used for a fundamental understanding of the atomic-scale phenomena underlying catalytic processes ever more pressing. In this context, characterizing catalyst particles in situ provides valuable information about the evolution of their composition, structure, oxidation state and charge state during an ongoing process. To disentangle the influence of individual parameters – temperature, pressure, gas composition, cluster size, as well as support acidity, redox state and defect density – it is crucial to control them precisely and separately in experiments. At the example of size-selected Pt n clusters – i.e. sub-nm particles defined to the exact number of atoms – on flat oxide supports, we follow their rich evolution phenomena via (synchrotron-based) X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM) during temperature ramps and in various gas environments. Here, we present our experience with these highly defined, yet complicated-to-create samples in ultra-high vacuum (UHV) and at mbar pressures. We discuss their stability during transport to synchrotrons and under reaction conditions on three prototypical oxide supports and show the various phenomena that can be disentangled. Ptn clusters on the non-reducible silicon dioxide, SiO 2 , remain size-selected and show remarkable stability. Doping strongly influences the size-dependent binding energy shifts and changes the Pt response to oxidative and reaction conditions, which we attribute to different cluster geometries: p-type doping leads to wetting, enhanced sinter resistance and a diminished response to oxidative environments, compared to clusters on n-type doped samples. We compare the system with our previous findings of a similar change in dimensionality for Pt 20 clusters on the reducible ceria, CeO 2 (111), support, induced by modulation of its O vacancy density. The Pt n /CeO 2 system is particularly interesting for strategies to stabilize and redisperse Pt clusters dynamically. Finally, we study the evolution of Pt n clusters on another reducible oxide support, magnetite, Fe 3 O 4 (001), in 0.1 mbar alternating redox conditions at RT and elevated temperature. In analogy to findings previously reported for Pt/TiO 2 (110), the clusters either become encapsulated by a thin oxide film via strong metal–support interaction (SMSI) or deeply buried in the magnetite. Overall, our approach of following the evolution of size-selected clusters on oxide supports leads to fundamental atomic-scale insights on nano-scale catalyst materials, on our path to sustainable, dynamic and self-repairing catalysts.

Falling, Lorenz J. [Technical Univ. of Munich (Ger↗
NASA NTRS1978

Incompressible fluid ellipsoids in halos. I - The second-harmonic oscillations of the Maclaurin spheroids

The structure and stability of Maclaurin spheroids embedded in rigid uniform-density oblate spheroidal halos are determined by the tensor virial-equation method. These spheroid-halo systems can be thought of as crude fluid analogs of disk galaxies with halos. The halos are assumed to have the same center, the same axis of symmetry, and the same equatorial radius as the Maclaurin spheroids. Only halos with lower eccentricity than the Maclaurin spheroids are considered. The dynamic instability of the toroidal (barlike) modes is suppressed when m, the ratio of the halo mass to Maclaurin spheroid mass, is greater than 3 pi/8 for spherical halos and when m is greater than 1/2 for halos congruent to the Maclaurin spheroids. Intermediate halo flattenings yield intermediate critical m-values. On the other hand, a neutral point of the toroidal modes in the rotating and inertial frames occurs for all m and for all allowed halo flattenings. Growth rates for secular instability beyond the neutral point are calculated, and the eigenfrequencies of all second-harmonic modes are given for select cases. The Ostriker-Peebles (1973) conjecture concerning the stability of disk galaxies against barlike perturbations appears to be incorrect.

Durisen, R. H.↗
DOE OSTI2014

Nuclear structure studies with INGA coupled to a fast DDAQ

Studies of different types of nuclear excitation and isomers remain the main thrust area of the last experimental campaign using INGA at TIFR-BARC Pelletron Linac Facility at Mumbai. A digital data acquisition system has been coupled with the INGA which has improved the data throughput and better gain stability. About forty experiments that have been proposed in this experimental campaign. Selected results from these experiments will be discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2006

Low conductivity and sintering-resistant thermal barrier coatings

A thermal barrier coating composition is provided. The composition has a base oxide, a primary stabilizer, and at least two additional cationic oxide dopants. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. In preferred embodiments, the base oxide is selected from zirconia and hafnia. The group A and group B cluster-promoting oxide dopants preferably are selected such that the group A dopant has a smaller cationic radius than the primary stabilizer oxide, and so that the primary stabilizer oxide has a small cationic radius than that of the group B dopant.

Zhu, Dongming↗
NASA NTRS2007

Low conductivity and sintering-resistant thermal barrier coatings

A thermal barrier coating composition is provided. The composition has a base oxide, a primary stabilizer, and at least two additional cationic oxide dopants. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. In preferred embodiments, the base oxide is selected from zirconia and hafnia. The group A and group B cluster-promoting oxide dopants preferably are selected such that the group A dopant has a smaller cationic radius than the primary stabilizer oxide, and so that the primary stabilizer oxide has a small cationic radius than that of the group B dopant.

Zhu, Dongming↗
DOE OSTI2015

Microstructural evolution in NaNbO{sub 3}-based antiferroelectrics

Our recent study found that CaZrO{sub 3} doping can effectively enhance the antiferroelectric P phase in NaNbO{sub 3} ceramics, leading to a double polarization hysteresis loop characteristic of a reversible antiferroelectric ↔ ferroelectric phase transition [Shimizu et al., Dalton Trans. 44, 10763 (2015)]. Here, a thorough transmission electron microscope study was performed to illustrate the CaZrO{sub 3} doping-assisted antiferroelectricity stabilization. In parallel to the bright-field imaging and selected area electron diffraction from multiple zone axes, detailed dark-field imaging was utilized to determine the superlattice structural origins, from either oxygen octahedral tilting or antiparallel cation displacements. By analogy with Pb(Zr{sub 1−x}Ti{sub x})O{sub 3} and rare-earth doped BiFeO{sub 3} systems, the chemical substitutions are such as to an induced polar-to-antipolar transition that is consistent with a tolerance factor reduction. The resultant chemical pressure has a similar effect to the compressive hydrostatic pressure where the antiferroelectric state is favored over the ferroelectric state.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The role of atmospheric stability/turbulence on wakes at the Egmond aan Zee offshore wind farm

Here, the aim of the paper is to present results from the NREL SOWFA project that compares simulations from models of different fidelity to meteorological and turbine data from the Egmond aan Zee wind farm. Initial results illustrate that wake behavior and impacts are strongly impacted by turbulence intensity. This includes both power losses from wakes and loading illustrated by the out of plane bending moment. Here we focus on understanding the relationship between turbulence and atmospheric stability and whether power losses due to wakes can effectively be characterized by measures of turbulence alone or whether atmospheric stability as a whole plays a fundamental role in wake behavior. The study defines atmospheric stability using the Monin-Obukhov length estimated based on the temperature difference between 116 and 70 m. The data subset selected using this method for the calculation of the Monin-Obukhov length indicate little diurnal or directional dependence of the stability classes but a dominance of stable classes in the spring/unstable classes in fall and of near-neutral classes at high wind speeds. The analysis is complicated by the need to define turbulence intensity. We can select the ratio of the standard deviation of wind speed to mean wind speed in each observation period using data from the meteorological mast, in which case a substantial amount of data must be excluded due to the presence of the wind farm. An alternative is to use data from the wind turbines which could provide a larger data set for analysis. These approaches are examined and compared to illustrate their robustness. Finally, power losses from wakes are categorized according to stability and/or turbulence in order to understand their relative importance in determining the behavior of wind turbine wakes.

17 WIND ENERGY↗
DOE OSTI2021

Synthesis, Electronic Structure, and Reactivity of a Planar Four–Coordinate, Cobalt–Imido Complex

A four-coordinate cobalt imido complex, ( tBu mPNP)Co=NMes ( tBu mPNP = modified PNP pincer ligand) has been synthesized from addition of 2,4,6-trimethylphenylazide (Mes–N 3 ) to the corresponding dinitrogen complex. The solid-state structure determined by X-ray diffraction established a rare, idealized planar geometry with a Co=N bond distance of 1.716(2) Å. Magnetic measurements revealed an S = 1 ground state with CAS-SCF calculations supporting radical character on the imide nitrogen. Here, thermolysis of the cobalt-imido compound induced selective insertion of the imido group into a Co–P bond and yielded a three-coordinate cobalt complex with a distorted T-shaped geometry. Transition state analysis conducted with DFT calculations established the thermodynamic stability of the P–N coupled product and provided insight into the exclusive selectivity.

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

Enhancement of high-temperature selectivity on Cu-SSZ-13 towards NH3-SCR reaction from highly dispersed ZrO2

ZrO2 is introduced as a secondary phase to Cu-SSZ-13 via different approaches and tested for the NH3-SCR reaction. It is shown that the vicinity between the two catalyst phases, i.e., ZrO2 dispersion, influences interaction between copper oxide (CuOx) on Cu-SSZ-13 and ZrO2. A strong interaction is achieved when ZrO2 is formed with high dispersion on Cu-SSZ-13, and leads to the chemical interaction of CuOx and ZrO2 in hydrothermally aged catalysts. The result is formation of a Cu-stabilized t-ZrO2 phase which greatly hinders the non-selective NH3 oxidation due to CuOx. With reduced ZrO2 dispersion and less Cu-SSZ-13 and ZrO2 interaction, the beneficial role of ZrO2 is diminished. This strategy of CuOx passivation is able to significantly enhance the high-temperature selectivity of the state-of-the-art NH3-SCR catalytic system while mitigating the adverse impact of CuOx clusters on the zeolite, potentially enabling higher Cu-content SCR catalysts and improved low-temperature activity.

NH3-SCR, ZrO2, selective catalytic reduction, afte↗
NASA NTRS1978

Alternate working fluids for solar air conditioning applications

An experimental investigation of sixteen different refrigerant-absorbent fluid pairs has been carried out in order to determine their suitability as the working fluid in a solar-powered absorption cycle air conditioner. The criteria used in the initial selection of a refrigerant-absorbent pair included: high affinity (large negative deviation from Raoult's Law), high solubility, low specific heat, low viscosity, stability, corrosive properties, safety, and cost. For practical solar considerations of a fluid pair, refrigerants were selected with low boiling points whereas absorbent fluids were selected with a boiling point considerably above that of the refrigerant. Additional restrictions are determined by the operating temperatures of the absorber and the generator; these temperatures were specified as 100 F (39 C) and 170 F (77 C). Data are presented for a few selected pressures at the specified absorber and generator temperatures.

Evans, R. D.↗
NASA NTRSDate not supplied

Evaluation of Long-Term Storage Stability and Operational Efficiency of Rapid Cycle Amine Adsorbents

With the recent incorporation of Mars Extravehicular Activity (EVA) into the 2025 NASA roadmap, Rapid Cycle Amine (RCA) technology advancement within the Exploration Extravehicular Mobility Unit (xEMU) applies to both the upcoming Lunar Artemis missions and future human exploration of Mars. The incorporation of commercial spacesuit vendors to service NASA’s crewed-space programs since 2021 has increased the demand for regenerable, RCA-based carbon dioxide (CO2) and humidity control adsorbents. The regenerable RCA subunit is the most advanced, long-term solution for CO2 removal and humidity control, enabling both lunar and Martian EVAs. The adsorbent selected for use within the RCA unit must exhibit sufficient storage stability and operational efficiency for prolonged missions. As XploSafe worked to simultaneously develop both a recirculating sub-atmospheric test rig and adsorbents for the RCA system within the xEMU, several novel adsorbents were evaluated for long-term storage stability in support of future extended-duration missions. The chosen materials were periodically evaluated by nuclear magnetic resonance (NMR) spectroscopy, thermal desorption-coupled with gas chromatography/mass spectrometry (TD-GC/MS), and CO2 adsorption to assess long-term storage efficacy across various environmental storage conditions. NMR spectroscopy was utilized by extracting the active CO2 adsorbing chemical from the solid support with deuterated solvent and comparing the spectra over time for degradation and change. The solid adsorbents were also analyzed via TD-GC/MS to reveal any potential off-gassing chemicals over time. Additionally, XploSafe’s breakthrough test rig was utilized to dose the solid adsorbents with a 585 BTU/h metabolic rate flow-equivalent CO2 stream and monitored for 0–99% CO2 breakthrough. The performance metrics from the breakthrough analysis were compared over the storage study duration for CO2 removal and humidity control. Xplo-SA9T was evaluated for 24 months, whereas two additional adsorbent variants, MMPA-Sorbent and LPEI-Sorbent, were each evaluated for 12 months.

John R Tidwell↗