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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
DOE OSTI2022

Interferometric bunch length measurements of 3 MeV picocoulomb electron beams

We report picosecond bunch length measurements using an interferometric method for a 3 MeV electron beam having bunch charge ranging from 1 to 14 pC. The method senses the single-cycle sub-terahertz (THz) pulse emitted by each electron bunch as coherent transition radiation which, in turn, is analyzed using a Michelson-type interferometer, forming an interferogram that is then processed to yield the nominal electron bunch length. This sub-THz coherent radiation intensity was measured using a quasi-optical detector (QOD) operated at room temperature. This experiment was quite challenging since the divergence angle of the sub-THz pulse emitted by the low-energy electron bunch exceeds ±10°, and its pulse energy at the entrance to the detector was as low as 100 pJ. When compared to a conventional helium-cooled silicon composite bolometer designed for frequencies above 0.5 THz, the QOD provided much better signal-to-noise ratio in the ~80 GHz frequency range, which was critical for the successful measurement of the bunch length.

36 MATERIALS SCIENCE↗
NASA NTRS2014

Obtaining Stokes Parameters from the SUMI Experiment

A sounding rocket experiment designed at the Marshall Space Flight Center, named the Solar Ultraviolet Magnetograph Investigation, had its second launch in July of 2012 to test the feasibility of measuring polarization signals of the ionized magnesium resonance doublet near 280 nm, originating from the transition region. The rocket housed a telescope at the front end and an imaging system at the rear end. Placed at the focal point of the self‐filtering telescope, a wave plate rotated through 12 predefined angular orientations to restrict the measurements to specific combinations of circular and linear polarization. Coupled with a double Wollaston analyzer, the linearly polarized ordinary and extraordinary beams were measured for the 12 combinations, each containing different fractions of the Stokes parameters (I, Q, U, V). A thorough analysis of the data has allowed us to come to several conclusions regarding the design of the experiment. 1) We are confident that polarization can be measured. A sunspot region was determined to exhibit similar results over multiple pixels. 2) Measurements are limited by resolution, i.e. regions smaller than the angular resolution per pixel cannot be resolved with any certainty. 3) Temporal evolution of magnetic features must be considered in future experimental designs. Measurements need to be taken in repeated cycles as opposed to a single cycle over the duration of the experiment. In our presentation, we will provide a summary of the observations along with the methods of our analysis, including the limitations that we've encountered.

Fayock, Brian↗
DOE OSTI2023

Effect of initial water saturation on the performance of fracturing fluids with and without polyallylamine under simulated EGS conditions

Objectives/Scope: StimuFrac (US Patents 9,873,828 B2 and 9,447,315 B2), a CO 2 - reactive polymer aqueous solution [polyallylamine (PAA) 1wt% in water] combined with CO 2 , can be used as a potentially less water-intensive fracturing fluid for enhanced geothermal systems (EGS). Our previous results show that in hot dry rock (HDR), PAA/CO 2 fracturing fluids outperformed other fluids such as water, CO 2 , and CO 2 /water in generating large fractures with less fluid consumed. The objective of this work is to investigate the effect of initial water saturation on the performance of StimuFrac by conducting hydraulic fracturing tests with ½ foot cubic rock samples held under representative EGS stress/temperature conditions and by using cyclic injection strategies (under constant injection rate). The resulting fracture hydraulic conductivities, breakdown pressures, and volumes of fluids required are compared. Methods/Procedures/Process: To simulate geothermal reservoir conditions, in all tests, the rock sample was held under triaxial confinement and at 200 °C, and different volumes of water were initially injected into the rock sample before any fracturing processes were initiated. For the single-cycle PAA (or water) alternating CO 2 (PAG or WAG) injection fracturing experiments, one complete cycle consisted of two steps: (1) injecting a PAA slug (or water slug) followed by (2) injecting CO 2 to initiate and propagate the fracture. For experiments involving multiple injection cycles, the CO 2 injection pressure is increased until it peaks and begins to decline (indicating fracture initiation at this moment), and then continued being injected for another 30 seconds to propagate the fracture. Then, these two-step cycles [injection of PAA (or water) followed by CO 2 injection (up to 2-4 mL/min)] are repeated. Applications/Significance/Novelty: The results of this study suggest that water saturation significantly affects the fracturing fluid transmission into the rock pore space, thus affecting the fracture initiation and propagation. In this study, fracturing tests via a single injection cycle or multiple injection cycles were performed. Splitting the rock samples in half after testing reveals that fracture propagation is significantly limited under high water saturation conditions (three-day initial water injection) compared to stimulation experiments performed in hot dry rock. The fractures propagate less than 1/3 of the distance from the wellbore to the outer rock surface, and in some cases, no fracture is generated. This may be caused by leak-off dominating the fracturing process and the fluid injection rate is insufficient to overcome leak-off, even under high injection rate conditions. Additionally, CO 2 could be leaking off into the wellbore annulus and this may be making it more difficult to generate sufficiently high-pressure gradients away from the near-wellbore region. Under low water saturation conditions (dry rock or after 1-day initial water injection), PAA/CO 2 consistently generated significantly larger fractures compared with the other fluids. CO 2 generated large fractures only in the hot dry rock and only when using high injection rates, though data variability is high.

58 GEOSCIENCES↗
DOE OSTI2025

Nonpyrophoric alternative to trimethylaluminum for the atomic layer deposition of Al 2 O 3

We have examined the atomic layer deposition (ALD) of Al 2 O 3 using a nonpyrophoric precursor, which possesses only Al–N bonds and no Al–C bonds: Al(N(CH 3 ) 2 ) 2 (–N(C 2 H 5 )–C 2 H 4 –N(C 2 H 5 ) 2 ), which we refer to as bis-dimethylamino-diamino-aluminum (BDMADA-Al). We employed a quartz crystal microbalance (QCM) to monitor ALD in situ and in real time, and the deposited thin films have been characterized using x-ray photoelectron spectroscopy, spectroscopic ellipsometry, x-ray reflectivity, and atomic force microscopy. Films deposited with BDMADA-Al result in near-stoichiometric Al2O3 at temperatures ranging from T = 120 to 285 °C using H 2 O as the coreactant and at T = 285 °C using t-BuOH as the coreactant. The properties of the films (density, C incorporation, stoichiometry, growth rates) are comparable using either BDMADA-Al or trimethylaluminum (TMA) as the precursor under similar reaction conditions. The N content in the films deposited with BDMADA-Al as the precursor is <1% at both T = 120 and 285 °C. Additionally, both BDMADA-Al|t-BuOH and TMA|t-BuOH processes deposit near-stoichiometric Al 2 O 3 at T = 285 °C, while neither process chemistry produces a constant growth rate per cycle at T = 120 °C. Close examination of single cycle QCM data from BDMADA-Al ALD indicates unique ligand exchange reaction mechanisms during each of the half-reactions. Experimentally, we have evidence supporting the mechanism in which upon the chemisorption of BDMADA-Al, the species on the surface retains the –N(CH 3 ) 2 ligands, while the diamine ligand is mostly lost on dissociative adsorption, except possibly at the higher temperature (285 °C). As a result, our work demonstrates that BDMADA-Al can be used as an effective alternative precursor to TMA for the ALD of Al 2 O 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Comparison of damage and ablation dynamics of multilayer dielectric films initiated by few-cycle pulses versus longer femtosecond pulses

The importance of high intensity few- to single-cycle laser pulses for applications such as intense isolated attosecond pulse generation is constantly growing, and with the breakdown of the monochromatic approximation in field ionization models, the few-cycle pulse (FCP) interaction with solids near the damage threshold has ushered a new paradigm of nonperturbative light–matter interaction. In this Letter, we systematically study and contrast how femtosecond laser-induced damage and ablation behaviors of SiO 2 /HfO 2 -based reflective multilayer dielectric thin film systems vary between FCP and 110 fs pulses. With time-resolved surface microscopy and ex situ analysis, we show that there are distinct differences in the interaction depending on the pulse duration, specifically in the “blister” morphology formation at lower fluences (damage) as well as in the dynamics of debris formation at higher fluences (ablation).

42 ENGINEERING↗
NASA NTRS2002

Thermodynamic Cycle and CFD Analyses for Hydrogen Fueled Air-breathing Pulse Detonation Engines

This paper presents the results of a thermodynamic cycle analysis of a pulse detonation engine (PDE) using a hydrogen-air mixture at static conditions. The cycle performance results, namely the specific thrust, fuel consumption and impulse are compared to a single cycle CFD analysis for a detonation tube which considers finite rate chemistry. The differences in the impulse values were indicative of the additional performance potential attainable in a PDE.

Povinelli, Louis A.↗
NASA NTRS1979

The effects of thermal cycling on the thermal deformation of graphite-polyimide

The effects of repetitive thermal cycling on the thermal deformation of graphite-fiber-reinforced polyimide laminates are investigated. Unsymmetric and unidirectional laminate specimens were cycled in an oven between room temperature and 180 or 315 C five times, and temperature and deformation were recorded as a function of time in order to measure thermal deformation. The results of the lower temperature cycling reveal a hysteresis-like effect in the temperature-thermal deformation relation for a single cycle, while no differences are detected from one cycle to the next. The response of an eight-layer curved specimen is found to agree well with predictions based on a piecewise-linear lamination theory, however, four-layer laminate response could not be explained. The results of the high-temperature tests also indicate a dependence of the strain on whether the specimen was being heated or cooled, however quantitative results are considered unreliable, due to strain gage difficulties.

Hyer, M. W.↗
NASA NTRS1978

Advanced manufacturing development of a composite empennage component for L-1011 aircraft

Work continued toward the development of tooling and processing concepts required for a cocured hat/skin cover assembly. A plan was developed and implemented to develop the process for using preimpregnated T300/5208 with a resin content of 34 + or - 2 percent by weight. Use of this material results in a simplified laminating process because removal by bleeding or prebleeding is no longer required. The approach to this task basically consists of fabricating and testing flat laminated panels and simulated structural panels to verify known processing techniques relative to end-laminate quality. The flat panels were used to determine air bleeding arrangement and required cure cycle. Single and multihat-stiffened panels were fabricated using the established air bleeding arrangement and cure cycle with the resulting cured parts yielding excellent correlation of ply thickness with all surfaces clear of porosity and voids.

Source record↗
NASA NTRS1961

A Method for Obtaining the Nonlinear Aerodynamic Stability Characteristics of Bodies of Revolution from Free-Flight Tests

A method is presented for obtaining the nonlinear aerodynamic stability characteristics of bodies of revolution from free-flight test.s The necessary conditions for the application of this method are: (1) that the roll rate and damping encountered in a single cycle of oscillation be small, and (2) that the resulting motion be reasonably planar. Four approximations to the nonlinear restoring moment are considered and solutions are obtained in closed form: 1. A single-term polynomial in an arbitrary power of the angle of attack. 2. A two-term polynomial having linear and cubic terms. 3. A three-term polynomial having linear, quadratic, and cubic terms. 4. A three-term polynomial having linear, quadratic, and cubic terms. An iteration procedure is formulated to allow the use of each of these approximations for obtaining the aerodynamic coefficients of bodies of revolution from free-flight test data. It is found that although the equations that are solved pertain strictly to planar motion, the solutions are applicable to motions that deviate to a fairly large degree from planar motion.

Kirk, Donn B.↗
DOE OSTI2023

Practical Multi-Cycle Refueling Simulation of Stable Salt Reactors Based on REBUS Depletion Calculation

A Python software tool ReloadPy has been developed to assistant in formulating online refueling strategies for a family of stable salt reactors. ReloadPy wraps over the legacy fast reactor analysis codes REBUS, DIF3D, and PERSENT. These codes are used to perform single cycle depletion analysis and calculate reactivity worth and power density. ReloadPy determines a refueling assembly position to achieve the user-specified primary objective while satisfying constraints on various performance parameters such as the maximum power density, the maximum reactivity worth of reloaded assembly, and the minimum cycle length. Various capabilities of prescribing refueling sequence or a range of candidate refueling positions and restarting a previous simulation with altered options are implemented to reduce the required user’s efforts to investigate different refueling strategies. This report presents the computational models and methods and also serves as a user guide. Long-term simulation capabilities with different refueling strategies are demonstrated by a series of sample SSR refueling calculations with two-dimensional surrogate core models.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1978

System-state and operating condition sensitive control method and apparatus for electric power delivery systems

This invention provides a method and apparatus for determining a precise switching sequence for the power switching elements of electric power delivery systems of the on-off switching type and which enables extremely fast transient response, precise regulation and highly stable operation. The control utilizes the values of the power delivery system power handling network components, a desired output characteristic, a system timing parameter, and the externally imposed operating conditions to determine where steady state operations should be in order to yield desired output characteristics for the given system specifications. The actual state of the power delivery system is continuously monitored and compared to a state-space boundary which is derived from the desired equilibrium condition, and from the information obtained from this comparison, the system is moved to the desired equilibrium condition in one cycle of switching control. Since the controller continuously monitors the power delivery system's externally imposed operating conditions, a change in the conditions is immediately sensed and a new equilibrium condition is determined and achieved, again in a single cycle of switching control.

Burns, III, William Wesley↗
NASA NTRS1986

Line plotting program using DI-3000/Grafmaker routines

A line plotting program has been developed using the DI-3000 graphics libraries and incorporates Grafmaker subroutines. The program allows multiple lines on a frame and multiple frames per run. Options such as automatic scaling, linear or single-cycle log graphs, and plot text such as titles, legends and axis labels are incorporated in the program. Greek and other fonts can be used in the plot text as well as upper and lower case text. Plot inputs are specified through a control file. The program also allows display of multiple independent data sets on a single graph.

Poppen, William A., Jr.↗
DOE OSTI2020

Coherent band-edge oscillations and dynamic longitudinal-optical phonon mode splitting as evidence for polarons in perovskites

The coherence of collective modes, such as phonons and polarons, and their modulation of electronic states is long sought in complex systems, which is a crosscutting issue in photovoltaics and quantum electronics. In photovoltaic cells and lasers based on metal halide perovskites, the presence of polarons, i.e., photocarriers dressed by the macroscopic motion of charged lattice, assisted by terahertz (THz) longitudinal-optical (LO) phonons, has been intensely studied yet is still debated. This may be key for explaining the remarkable properties of the perovskite materials, e.g., defect tolerance, long charge lifetimes, and diffusion lengths. In this work we use the intense single-cycle THz pulse with peak electric field up to E THz = 1000 kV/cm to drive coherent polaronic band-edge oscillations at room temperature in CH 3 NH 3 PbI 3 (MAPbI 3 ). We reveal the oscillatory behavior is dominated by a specific quantized lattice vibration mode at $ω$ LO ~ 4 THz, which is both dipole and momentum forbidden. THz-driven coherent polaron dynamics exhibits distinguishing features: room temperature coherent oscillations at ω LO longer than 1 ps in both single crystals and thin films, mode-selective modulation of different band-edge states assisted by electron-phonon interaction, and dynamic mode splitting at low temperature due to entropy and anharmonicity of organic cations. Our results demonstrate intense THz-driven coherent band-edge modulation is a powerful probe of electron-lattice coupling phenomena and polaronic quantum control in perovskites.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Reaction cycle and thermodynamics in bacteriorhodopsin

Light causes the all-trans to 13-cis isomerization of the retinal in bacteriorhodopsin; the thermal relaxation leading back to the initial state drives proton transport first via proton transfer between the retinal Schiff base and D85 and then between the Schiff base and D96. The reaction sequence and thermodynamics of this photocycle are described by measuring time-resolved absorption changes with a gated multichannel analyzer between 100 ns and 100 ms, at six temperatures between 5 degrees C and 30 degrees C. Analysis of the energetics of the chromophore reaction sequence is on the basis of a recently proposed model (Varo & Lanyi, Biochemistry 30, 5016-5022, 1991) which consists of a single cycle and many reversible reactions: BR -hv-->K<==>L<==>M1-->M2<==>N<==>O-->BR. The existence of the M1-->M2 reaction, which functions as the switch in the proton transfer, is confirmed by spectroscopic evidence. The calculated thermodynamic parameters indicate that the exchange of free energy between the protein and the protons is at the switch step. Further, a large entropy decrease at this reaction suggests a protein conformation change which will conserve delta G for driving the completion of the reaction cycle. The results provide insights to mechanism and energy coupling in this system, with possible relevance to the general question of how ion pumps function.

Review↗
DOE OSTI2021

Gamma Radiolysis of Biphasic Acetohydroxamic Acid (AHA) Solvent Systems

Acetohydroxamic acid (AHA) has been proposed as a substitute for uranium(IV) and hydrazine as a plutonium complexant and neptunium reductant for simplified, single-cycle used nuclear fuel reprocessing flowsheets. However, the chemical behavior of AHA in an intense multi-component radiation field is poorly understood, especially under representative biphasic reprocessing solvent system conditions. In response to this critical knowledge gap, this study has investigated the gamma radiolytic integrity of AHA in aqueous nitric solutions in contact with an organic phase, comprising current and future reprocessing ligands (TBP, DEHBA, and DEHiBA) dissolved in n-dodecane diluent. Our data show negligible effect of the organic phase on the radiolytic behavior of AHA compared to complementary single-phase experiments.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Radiolytic evaluation of acetohydroxamic acid (AHA) under biphasic (n-dodecane and TBP/DEHBA/DEHiBA) used nuclear fuel reprocessing conditions

Acetohydroxamic acid (AHA) has been proposed as a substitute for uranium(IV) and hydrazine as a plutonium complexant and neptunium reductant for simplified, single-cycle used nuclear fuel reprocessing flowsheets. However, the chemical behavior of AHA in an intense multi-component radiation field is poorly understood, especially under representative biphasic reprocessing solvent system conditions. In response to this critical knowledge gap, this study has investigated the gamma radiolytic integrity of AHA in aqueous nitric solutions in contact with an organic phase, comprising current and future reprocessing ligands (TBP, DEHBA, and DEHiBA) dissolved in n-dodecane diluent. Our data show negligible effect of the organic phase on the radiolytic behavior of AHA compared to complementary single-phase experiments.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Spontaneous Strain Buffer Enables Superior Cycling Stability in Single-Crystal Nickel-Rich NCM Cathode

The capacity degredation in layered Ni-rich LiNixCoyMnzO2 (x >= 0.8) cathode largely originated from drastic surface reactions and intergranular cracks in polycrystalline particles. Herein, we report a highly stable single- crystal LiNi0.83Co0.12Mn0.05O2 cathode material, which can deliver a high specific capacity (similar to 209 mAh g(-1) at 0.1 C, 2.8-4.3 V) and meanwhile display excellent cycling stability (>96% retention for 100 cycles and >93% for 200 cycles). By a combination of in situ X-ray diffraction and in situ pair distribution function analysis, an intermediate monoclinic distortion and irregular H3 stack are revealed in the single crystals upon charging-discharging processes. These structural changes might be driven by unique Li-intercalation kinetics in single crystals, which enables an additional strain buffer to reduce the cracks and thereby ensure the high cycling stability.

in situ synchrotron characterization↗