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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Deuteron-induced reactions on natural Zr from threshold to 50 MeV: production of 86g Y

Two stacks of thin Zr foils were irradiated with 30 and 50 MeV deuterons, respectively, using the Lawrence Berkeley National Laboratory 88-Inch Cyclotron, and 19 excitation functions for nat Zr(d,x) reactions were measured over a beam energy range of 6.3–47.64 MeV, where the independent cross sections for nat Zr(d,x) 88 Nb and nat Zr(d,x) 86m,g Y were measured for the first time. The well-characterized nat Fe(d,x) 56 Co, nat Ni(d,x) 56 Co, nat Ni(d,x) 58 Co, nat Ni(d,x) 61 Cu, nat Ti(d,x) 46 Sc and nat Ti(d,x) 48 V monitor reactions were used to determine the deuteron beam current throughout the stacks. All cross sections were determined using High Purity Germanium (HPGe) detector γ-ray spectroscopy. A variance minimization technique was employed to simultaneously constrain the deuteron beam currents with multiple monitor reactions, thus reducing systematic uncertainties. An additional 16 channels are reported for reactions on the nickel, titanium, and iron monitor foils, leading to a total of 35 excitation functions, with seven reaction channels reported for the first time in this work. The measured excitation functions are compared to calculations provided by the reaction modeling codes TALYS – 2.0, ALICE – 2020, CoH – 3.5.3 and EMPIRE – 3.2.3, as well as the TENDL – 2023 data library. The degree of agreement between theory and experiments is discussed. The possible production of the important PET radionuclide 86g Y via the nat Zr(d,x) route was critically examined. The physical yields for nat Zr(d,x) 86 Y and other yttrium isotopes produced were calculated and compared to other production pathways. Due to high-level of associated radionuclide impurities, this route cannot deliver 86g Y suitable for medical applications.

86gY↗
NASA NTRS1981

Annealing and anomalous high-energy electron irradiation effects in low-cost silicon N+P solar cells

Silicon solar cells of N(+)P type were subjected to 1 MeV electron irradiation (up to 10 to the 16th electrons/sq cm) and then annealed at 450 C for 20 min or annealed with no electron irradiation. Electron irradiation resulted in a degradation of longer wavelength cell response, but produced a marked enhancement of response at shorter wavelengths with a peak change of 40% at 0.44 microns. Subsequent thermal anneal at 450 C reduced the long-wavelength degradation, but enhancement at shorter wavelengths persisted. Excitation at the shorter wavelengths was in the N(+)-diffused layer and in the junction region of the cell. Anneal of unirradiated cells produced shorter-wavelength enhancement with a similar peaking at 0.44 microns, but with a relative change of only 20%. More enhancement was produced in the longer wavelength region (up to 0.8 microns). These effects in the different cell regions are explained by a decrease in the interstitial oxygen-impurity complexes (deep recombination levels) and the formation of substantial oxygen-silicon vacancy centers (donors).

Garlick, G. F. J.↗
NASA NTRS2004

Domes on Europa: The Role of Thermally Induced Compositional Diapirism

The surface of Europa is peppered by topographic domes, interpreted as sites of intrusion and extrusion. Diapirism is consistent with dome morphology, but thermal buoyancy alone cannot produce sufficient driving pressures to create the observed dome elevations. Instead, we suggest that diapirs may initiate by thermal convection that induces compositional segregation within Europa's ice shell. This double-diffusive convection scenario allows sufficient buoyancy for icy plumes to create the observed surface topography, if the ice shell has a very small effective elastic thickness (approximately 0.1 to 0.5 km) and contains low-eutectic-point impurities at the percent level. Thermal buoyancy, compositional buoyancy and double-diffusive convection are discussed.

Pappalardo, R. T.↗
DOE OSTI2019

An EXAFS and XANES Study of V, Ni, and Fe Speciation in Cokes for Anodes Used in Aluminum Production

Lower-quality petroleum coke with higher levels of sulfur and metal impurities will have to be used for the manufacturing of anodes for aluminum production in the future. The sulfur and metallic impurities affect the anode properties in the aluminum production process, but the chemical identity of the metal species in the coke is not known. In this study, industrial petroleum cokes with high sulfur levels were analyzed by X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) in order to determine the identity of the V, Ni, and Fe impurities. The XANES spectra were compared with pure-phase standards. EXAFS was used to compare the impurity metal structures with known crystal structures. It was found that V is present mainly as hexagonal V{sub 3}S{sub 4}. Ni is present mainly as hexagonal NiS, and Fe is present as hexagonal FeS. This knowledge of the chemical states of the metal elements in coke, which are known to affect anode performance, is the first step in understanding the mechanism of the action of these elements on anode reactivity.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Investigation of new semiinsulating behavior of III-V compounds

The investigation of defect interactions and properties related to semiinsulating behavior of III-V semiconductors resulted in about twenty original publications, six doctoral thesis, one masters thesis and numerous conference presentations. The studies of new compensation mechanisms involving transition metal impurities have defined direct effects associated with deep donor/acceptor levels acting as compensating centers. Electrical and optical properties of vanadium and titanium levels were determined in GaAs, InP and also in ternary compounds InGaAs. The experimental data provided basis for the verification of chemical trends and the VRBE method. They also defined compositional range for III-V mixed crystals whereby semiinsulating behavior can be achieved using transition elements deep levels and a suitable codoping with shallow donor/acceptor impurities.

Lagowski, Jacek↗
DOE OSTI2024

UEDGE modeling of plasma detachment of CFETR with ITER ‐like divertor geometry by external impurity seeding

Abstract Efficient handling of high heat flux on the plasma‐facing components, particularly the divertor targets, poses a significant challenge for the Chinese Fusion Engineering Testing Reactor (CFETR) with fusion power of Gigawatt. This work investigates the divertor plasma detachment of CFETR with a standard ITER‐like divertor geometry by neon (Ne) or argon (Ar) impurity seeding using UEDGE code. The cross‐field drifts terms are switched off, and fluid neutral models and a “fixed‐fraction” impurity model are applied to enable efficient simulations for the study of CFETR detachment. In order to reduce the heat load on the divertor targets below the acceptable level (<10 MW/m 2 ), the impurity fraction ( f ), pumping speed ( S ), and upstream density are varied to identify the suitable operations window during Ne seeding. The effects of Ne and Ar impurities on the plasma detachment are compared. It is found that with the power across the core‐edge interface P SOL = 200 MW and separatrix density of 2.8 10 19 , Ne impurity fraction ≥1.7%, and Ar impurity fraction ≥0.24% can achieve the partial detachment. Achieving similar total radiation power (˜148 MW), the Ne fraction is 2.3% and the Ar fraction is 0.24%. Moreover, the simulation results indicate that Ar exhibits better power radiation efficiency and core compatibility compared with Ne.

Zhang, M. Z.↗
DOE OSTI2023

Purification of Lithium-Ion Battery Black Mass through Tailored Alkaline Corrosion

Obtaining high-purity material outputs is crucial to the viability of novel process aimed at direct recycling of lithium-ion batteries. Metallic impurities in recycled cathodes have been shown to inhibit performance, thereby threatening mainstream acceptance of recycled battery products. Thus, shredded black mass (BM) must be purified to remove metallic contaminants, and specifically Al and Cu originating from the electrode current collectors. We herein explore a process to ionize solid copper and aluminum to ionic form based on tailored alkaline chemistry, without incurring damage to the target cathode material (Li(NixMnyCo1-x-y)O2; NMC). Al and Cu corrosion may be enhanced through the addition of chloride salt, elevated temperatures, and the use of ultrasonication - all of which disrupt the formation of passivating films on the metallic surface, and thereby increase corrosion rate. We demonstrate optimized parameters for Al and Cu corrosion both from a kinetic and overall process cost perspective. Further, we analyze the impact of these conditions on the structural (XRD, SEM), chemical (EDS, ICP), and electrochemical (impedance, cycling, dQ/dV) properties of NMC, and suggest that the present purification method does not significantly disrupt NMC performance. Finally, we present preliminary results from a promising bench-scale demonstration of this purification process applied to a simulated black mass.

ADVANCED PROPULSION SYSTEMS,ENERGY STORAGE↗
NASA NTRS2007

Sulfur and Moisture Effects on Alumina Scale and TBC Spallation

It has been well established that a few ppmw sulfur impurity may segregate to the interface of thermally grown alumina scales and the underlying substrate, resulting in bond degradation and premature spallation. This has been shown for NiAl and NiCrAl-based alloys, bare single crystal superalloys, or coated superalloys. The role of reactive elements (especially Y) has been to getter the sulfur in the bulk and preclude interfacial segregation. Pt additions are also very beneficial, however a similar thermodynamic explanation does not apply. The purpose of the present discussion is to highlight some observations of these effects on Rene'142, Rene'N5, PWA1480, and PWA1484. For PWA1480, we have mapped cyclic oxidation and spallation in terms of potential sulfur interfacial layers and found that a cumulative amount of about one monolayer is sufficient to degrade long term adhesion. Depending on substrate thickness, optimum performance occurs if sulfur is reduced below about 0.2-0.5 ppmw. This is accomplished in the laboratory by hydrogen annealing or commercially by melt-fluxing. Excellent 1150 C cyclic oxidation is thus demonstrated for desulfurized Rene'142, Rene'N5, and PWA1484. Alternatively, a series of N5 alloys provided by GE-AE have shown that as little as 15 ppmw of Y dopant was effective in providing remarkable scale adhesion. In support of a Y-S gettering mechanism, hydrogen annealing was unable to desulfurize these alloys from their initial level of 5 ppmw S. This impurity and critical doping level corresponds closely to YS or Y2S3 stoichiometry. In many cases, Y-doped alloys or alloys with marginal sulfur levels exhibit an oxidative sensitivity to the ambient humidity called Moisture-Induced Delayed Spallation (MIDS). After substantial scale growth, coupled with damage from repeated cycling, cold samples may spall after a period of time, breathing on them, or immersing them in water. While stress corrosion arguments may apply, we propose that the underlying cause is related to a hydrogen embrittlement reaction: Al alloy + 3 H2O = Al(OH)3 + 3H(+) + 3e(-). This mechanism is derived from an analogous moisture-induced hydrogen embrittlement mechanism originally shown for Ni3Al and FeAl intermetallics. Consequently, a cathodic hydrogen charging technique was used to demonstrate that electrolytic de-scaling occurs for these otherwise adherent alumina scales formed on Y-doped Rene'N5, in support of hydrogen effects. Finally, some TBC observations are discussed in light of all of the above. Plasma sprayed 8YSZ coatings, produced on PWA1484 without a bond coat, were found to survive more than 1000 1-hr cycles at 1100 C when desulfurized to below 0.1 ppmw. At higher sulfur (1.2 ppmw) levels, moisture sensitivity and delayed TBC failure, referred to as Desk Top Spallation, occurred at just 200 hr. Despite a large degree of scatter, a factor of 5 in life improvement is indicated for desulfurized samples in cyclic furnace tests, confirming the beneficial effect of low sulfur alloys on model TBC systems. (DTS and moisture effects are also observed on commercially applied PVD 7YSZ coatings on Rene'N5+Y with Pt-aluminide bond coats). These types of catastrophic failure were subverted on the model system by segmenting the substrate into a network of 0.010 high ribs, spaced in. apart, prior to plasma spraying. No failures occurred after 1000 cycles at 1150 C or after 2000 cycles at 1100 C, even after water immersion. The benefit is described in terms of elasticity models and a critical buckling stress.

Smialek, James L.↗
NASA NTRS1972

A study of beryllium and beryllium-lithium complexes in single crystal silicon

When beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 MeV and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-MeV level is due to a more complex beryllium configuration than the 191-MeV level. When lithium is thermally diffused into a beryllium-doped silicon sample, it produces two acceptor levels at 106 MeV and 81 MeV. Quenching and annealing studies indicate that these levels are due to lithium forming a complex with the defects responsible for the 191-MeV and 145-MeV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-MeV beryllium level is split into two levels, presumably by internal strains. Tentative models are proposed.

Crouch, R. K.↗
DOE OSTI2021

Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe 0.55 Se 0.45

By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe 0.55 Se 0.45 , a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTe 0.55 Se 0.45 , which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1972

Study of beryllium and beryllium-lithium complexes in single-crystal silicon.

When beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-meV level is due to a more complex beryllium configuration than the 191-meV level. When lithium is thermally diffused into a beryllium-doped silicon sample, it produces two new acceptor levels at 106 and 81 meV. Quenching and annealing studies indicate that these new levels are due to lithium forming a complex with the defects responsible for the 191- and 145-meV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-meV beryllium-lithium level is split into two levels, presumably by internal strains. Tentative models are proposed to explain these results.

Crouch, R. K.↗
DOE OSTI2024

Simultaneous reproduction of experimental profiles, fluxes, transport coefficients, and turbulence characteristics via nonlinear gyrokinetic profile predictions in a DIII-D ITER similar shape plasma

Experimental conditions obtained on the DIII-D tokamak in the ITER Similar Shape (ISS) have been compared extensively with nonlinear gyrokinetic simulation using the CGYRO code [Candy et al., J. Comput. Phys. 324, 73–93 (2016)] with comparisons spanning ion and electron heat fluxes, electron and impurity particle transport, and turbulent fluctuation levels and characteristics. Bayesian optimization techniques [Rodriguez-Fernandez et al., Nucl. Fusion 62(7), 076036 (2022)], combined with nonlinear gyrokinetics, have been used to obtain simultaneously Qi, Qe, and Γe flux-matched profiles that are found to be in good agreement with experimental profile measurements. Synthetic diagnostics were used to compare measured beam emission spectroscopy and correlation electron cyclotron emission turbulent fluctuations with nonlinear simulation. Although some disagreements exist, nonlinear simulations are found to be in generally good agreement with measured fluctuation levels, spectral shapes, and measured radial trends in low-k δne/ne and δTe/Te. Low (Li and C) and mid-Z (Ca) impurity transport was also compared with these flux-matched simulations. Fully stripped, low-Z impurities are well reproduced by the gyrokinetic modeling while clear disagreement exists in comparisons with mid-Z impurities. Nonlinear gyrokinetic investigation into the Z dependence of impurity transport in the ISS conditions is also performed, demonstrating clear trends of impurity diffusion with impurity Z (both D∝Z and D∝1/Z) that vary with the radial location studied. These trends are shown to result from the local dominance of ion temperature gradient or ∇n driven trapped electron mode turbulence and may contribute to the disagreement between simulation and experiment in mid-Z impurity transport. The results of this work represent one of the most complete validation studies of the gyrokinetic model performed to date and provide an example of new capabilities for predicting performance in future fusion devices.

Physics↗
DOE OSTI2020

Insight the process of hydrazine gas adsorption on layered WS 2 : a first principle study

The process of hydrazine gas adsorption on layered WS 2 has been systematically studied from first principle calculations. Our results demonstrate that this adsorption process is exothermic, and hydrazine molecules are physically adsorbed. The layer-dependent adsorption energy and interlayer separation induced by van der Waals interaction exerted by hydrazine molecules lead to the difficulty in desorbing hydrazine molecules from layered WS 2 as the number of layers increases. The most interesting finding is the emergence of localized impurity states below the Fermi level upon the hydrazine adsorption, irrespective of the number of WS 2 layers, resulting in a significant effect on the band structures and subsequently changing its electrical conductivity. Furthermore, a layer-dependent small charge transfer occurs between hydrazine and layered WS 2 , leading to a charge redistribution and considerable polarization in the adsorbed systems. The existence of defects and the humidity, on the other hand, influences the sensitivity of layered WS 2 to the hydrazine adsorption. Here, obtained results show that a perfectly layered WS 2 might be a promising candidate as an efficient nanosensor to detect such toxic gas in dry environment.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Active wall conditioning through boron powder injection compatible $\mathrm{ELM}$ control in $\mathrm{EAST}$

Real-time wall conditioning and edge-localized mode (ELM) suppression through real-time boron powder injection into high-confinement mode discharges of the Experimental Advanced Superconducting Tokamak (EAST) have been investigated. The boron powder injection effectively conditioned the plasma-facing components, as shown by the reductions in low-Z and high-Z impurities and the global recycling level in the whole inner vessel, and suppressed the strong magnetohydrodynamic (MHD) activity in the plasma core. The improved wall conditions also resulted in an earlier transition from L- to H-mode. Boron powder injection also effectively suppressed ELM in the lower single null configuration with BT in the favorable direction while leaving the plasma density and stored energy largely unaffected.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Dissociation of O(2-)2 defects into paramagnetic O(-) in wide band-gap insulators - A magnetic susceptibility study of magnesium oxide

The magnetic susceptibility of single-crystal MgO has been measured in the temperature range 300-1000 K, using a Faraday balance. The high-purity crystal (less than 100 ppm transition metals), grown from the melt in a H2O-containing atmosphere, was found to be paramagnetic due to the presence of defects on the O(2-) sublattice. The defects derive from OH(-) introduced into the MgO matrix by the dissolution of traces of H2O during crystal growth. The OH(-) converts into O(2-)2 and H2. Each O(2-)2 represents two coupled, spin-paired O(-) states. The observed strongly temperature-dependent paramagnetism can be described by three contributions that overlay the intrinsic diamagnetism of MgO and arise from the low level of transition-metal impurities, O(-) generated by 0(2-)2 dissociation, and O(-) states trapped by quenching from high temperatures from previous experiments.

Batllo, F.↗
NASA NTRS2004

Non-Newtonian Convection and Compositional Buoyancy: Advances in Modeling Convection and Dome Formation on Europa

Numerical modeling of non-Newtonian convection in ice shows that convection controlled by grain boundary sliding rheology may occur in Europa. This modeling confirms that thermal convection alone cannot produce significant dome elevations. Domes may instead be produced by diapirs initiated by thermal convection that in turn induces compositional segregation. Exclusion of impurities from warm upwellings would allow sufficient buoyancy for icy plumes to account for the observed approximately 100 m topography of domes, provided the ice shell has a small effective elastic thickness (approximately 0.2 to 0.5 km) and contains low eutectic-point impurities at the few percent level.

Pappalardo, R. T.↗
NASA NTRS2004

Sensor for Monitoring Nanodevice-Fabrication Plasmas

The term plasma process diagnostics (PPD) refers to a spectroscopic technique and sensing hardware that have been proposed for monitoring plasma processes used to fabricate electronic devices that feature sizes as small as several nanometers. Nanometer dimensions are characteristic of the quantum level of miniaturization, where single impurity atoms or molecules can drastically change the local properties of the nanostructures. Such changes may be purposely used in nanoscale design but may also be extremely damaging or cause improper operation of the fabricated devices. Determination of temperature and densities of reactants near the developing features is important, since the structural synthesis is affected by characteristics of the local microenvironment. Consequently, sensors capable of nonintrusive monitoring with high sensitivity and high resolution are essential for real-time atomistic control of reaction kinetics and minimizing trace contamination in plasma processes used to fabricate electronic nanodevices. Such process-monitoring sensors are required to be compact, multiparametric, and immune to the harsh environments of processing plasmas. PPD is intended to satisfy these requirements. The specific technique used to implement plasma diagnostics with a PPD sensor would be an advanced version of continuous-wave cavity-ringdown spectroscopy (CW-CRDS) capable of profiling spectral line broadenings in order to derive both Doppler and Stark components. CRDS is based on measurements of the rate of absorption of laser light in an optical resonator. The ultimate sensitivity results from a very long absorption path length within the cavity and immunity to variations in incident laser intensity. The proposed version of this technique would involve the use of multiplexing tunable laser diodes and an actively modulated high-reflectivity optical resonator, thus offering a synergistic combination of simplicity, compactness, high sensitivity, and high resolution. The multiplexing capabilities of diode lasers could be utilized to make the PPD sensor a single, simple, compact, and inexpensive tool for the acquisition of multiparametric data. A PPD sensor would be capable of continuous measurement of such physical parameters as gas temperature, gas velocity, electron number density, and absolute densities of reacting chemical species. A laser beam can be easily adjusted to analyze the immediate vicinity of the growing nanostructures (or features etched down) in real time. The absorption enhancement in an optical cavity would afford the sensitivity needed for measurement of the temperature and densities of species at concentrations significantly lower than measurable by other nonintrusive techniques. It is anticipated that fully developed PPD sensors would enable simultaneous measurement of local temperature and determination of plasma species responsible for the synthesis and functionalization of nanodevices. These sensors would also enable tracking the pathways and origins of damaging contaminants, thereby providing feedback for adjustment of processes to optimize them and reduce contamination. The PPD sensors should also be useful for optimization of conventional microelectronics manufacturing plasma processes. Going beyond plasma processes for fabrication of electronic devices, PPD sensors could be used for monitoring of atoms, molecules, ions, radicals, clusters, and particles in a variety of other settings, including outer space. Because of their high sensitivity, such sensors could also prove useful for detecting traces of illegal drugs and explosives.

Bolshakov, Alexander↗
DOE OSTI2021

Topology and many-body localization

We discuss the problem of localization in two dimensional electron systems in the quantum Hall (single Landau level) regime. After briefly summarizing the well-studied problem of Anderson localization in the non-interacting case, we concentrate on the problem of disorder induced many-body localization (MBL) in the presence of electron–electron interactions using numerical exact diagonalization and eigenvalue spacing statistics as a function of system size. We provide evidence showing that MBL is not attainable in a single Landau level with short range (white noise) disorder in the thermodynamic limit. We then study the interplay of topology and localization, by contrasting the behavior of topological and nontopological subbands arising from a single Landau level in two models — (i) a pair of extremely flat Hofstadter bands with an optimally chosen periodic potential, and (ii) a Landau level with a split-off nontopological impurity band. Both models provide convincing evidence for the strong effect of topology on the feasibility of many-body localization as well as slow dynamics starting from a nonequilibrium state with charge imbalance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗