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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Two-Photon Laser-Induced Fluorescence O and N Atoms for the Study of Heterogeneous Catalysis in a Diffusion Reactor

Advanced laser-based diagnostics have been developed to examine catalytic effects and atom/surface interactions on thermal protection materials. This study establishes the feasibility of using laser-induced fluorescence for detection of O and N atom loss in a diffusion tube to measure surface catalytic activity. The experimental apparatus is versatile in that it allows fluorescence detection to be used for measuring species selective recombination coefficients as well as diffusion tube and microwave discharge diagnostics. Many of the potential sources of error in measuring atom recombination coefficients by this method have been identified and taken into account. These include scattered light, detector saturation, sample surface cleanliness, reactor design, gas pressure and composition, and selectivity of the laser probe. Recombination coefficients and their associated errors are reported for N and O atoms on a quartz surface at room temperature.

Pallix, Joan B.↗
NASA NTRS1999

Using High Frequency Focused Water-Coupled Ultrasound for 3-D Surface Depression Profiling

Surface topography is an important variable in the performance of many industrial components and is normally measured with diamond-tip profilometry over a small area or using optical scattering methods for larger area measurement. A prior study was performed demonstrating that focused air-coupled ultrasound at 1 MHz was capable of profiling surfaces with 25 micron depth resolution and 400 micron lateral resolution over a 1.4 mm depth range. In this article, the question of whether higher-frequency focused water-coupled ultrasound can improve on these specifications is addressed. 10 and 25 MHz focused ultrasonic transducers were employed in the water-coupled mode. Time-of-flight images of the sample surface were acquired and converted to depth / surface profile images using the simple relation (d = V*t/2) between distance (d), time-of-flight (t), and the velocity of sound in water (V). Results are compared for the two frequencies used and with those from the 1 MHz air-coupled configuration.

Roth, Don J.↗
NASA NTRS2012

Agile Science Operations: A New Approach for Primitive Exploration Bodies

Primitive body exploration missions such as potential Comet Surface Sample Return or Trojan Tour and Rendezvous would challenge traditional operations practices. Earth-based observations would provide only basic understanding before arrival and many science goals would be defined during the initial rendezvous. It could be necessary to revise trajectories and observation plans to quickly characterize the target for safe, effective observations. Detection of outgassing activity and monitoring of comet surface activity are even more time constrained, with events occurring faster than round-trip light time. "Agile science operations" address these challenges with contingency plans that recognize the intrinsic uncertainty in the operating environment and science objectives. Planning for multiple alternatives can significantly improve the time required to repair and validate spacecraft command sequences. When appropriate, time-critical decisions can be automated and shifted to the spacecraft for immediate access to instrument data. Mirrored planning systems on both sides of the light-time gap permit transfer of authority back and forth as needed. We survey relevant science objectives, identifying time bottlenecks and the techniques that could be used to speed missions' reaction to new science data. Finally, we discuss the results of a trade study simulating agile observations during flyby and comet rendezvous scenarios. These experiments quantify instrument coverage of key surface features as a function of planning turnaround time. Careful application of agile operations techniques can play a significant role in realizing the Decadal Survey plan for primitive body exploration

Agile science↗
DOE OSTI2016

Predictable surface ablation of dielectrics with few-cycle laser pulse even beyond air ionization

We study surface ablation of dielectrics with single-shot few-cycle optical pulse (∼10 fs) in air, at intensities below and above the onset of air ionization. We perform 3D analysis and careful calibration of the fluence distribution at the laser focus, spanning from linear– to nonlinear– focusing regimes, enabling to thoroughly characterize the severe limitation of the fluence delivered onto the sample surface upon increase of incident pulse energy. Despite significant beam reshaping taking place at high fluence, we demonstrate that it is nevertheless possible to confidently predict the resulting crater profiles on fused silica surface, even in the regime of filamentation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Weak antilocalization effect due to topological surface states in Bi 2 Se 2.1 Te 0.9

In this work, we have investigated the weak antilocalization (WAL) effect in the p -type Bi 2 Se 2.1 Te 0.9 topological system. The magnetoconductance shows a cusp-like feature at low magnetic fields, indicating the presence of the WAL effect. The WAL curves measured at different tilt angles merge together when they are plotted as a function of the normal field components, showing that surface states dominate the magnetoconductance in the Bi 2 Se 2.1 Te 0.9 crystal. We have calculated magnetoconductance per conduction channel and applied the Hikami-Larkin-Nagaoka formula to determine the physical parameters that characterize the WAL effect. The number of conduction channels and the phase coherence length do not change with temperature up to T = 5 K. In addition, the sample shows a large positive magnetoresistance that reaches 1900% under a magnetic field of 35 T at T = 0.33 K with no sign of saturation. The magnetoresistance value decreases with both increasing temperature and tilt angle of the sample surface with respect to the magnetic field. The large magnetoresistance of topological insulators can be utilized in future technology such as sensors and memory devices.

36 MATERIALS SCIENCE↗
NASA NTRS2004

The Effect of Salts on Electrospray Ionization of Amino Acids in the Negative Mode

The continued search for organics on Mars will require the development of simplified procedures for handling and processing of soil or rock core samples prior to analysis by onboard instrumentation. Extraction of certain organic molecules such as amino acids from rock and soil samples using a liquid solvent (H2O) has been shown to be more efficient (by approximately an order of magnitude) than heat extraction methods. As such, liquid extraction (using H2O) of amino acid molecules from rock cores or regolith material is a prime candidate for the required processing. In this scenario, electrospray ionization (ESI) of the liquid extract would be a natural choice for ionization of the analyte prior to interrogation by one of a variety of potential analytical separation techniques (mass spectroscopy, ion mobility spectroscopy, etc.). Aside from the obvious compatibility of ESI and liquid samples, ESI offers simplicity and a soft ionization capability. In order to demonstrate that liquid extraction and ESI can work as part of an in situ instrument on Mars, we must better understand and quantify the effect salts have on the ESI process. In the current work, we have endeavored to investigate the feasibility and limitations of negative mode ESI of Martian surface samples in the context of sample salt content using ion mobility spectroscopy (IMS).

H I Kim↗
DOE OSTI2011

Depth-resolved residual stress analysis of thin coatings by a new FIB-DIC method

A new methodology for the measurement of depth sensitive residual stress profiles of thin coatings with sub-micrometer resolution is presented. The two step method consists of incremental focused ion beam (FIB) ring-core milling, combined with high-resolution in situ SEM-FEG imaging of the relaxing surface and a full field strain analysis by digital image correlation (DIC). The through-thickness profile of the residual stress can be obtained by comparison of the experimentally measured surface strain with finite element modeling using Schajer's integral method. In this work, a chromium nitride (CrN) CAE-PVD 3.0 {mu}m coating on steel substrate, and a gold MS-PVD 1.5 {mu}m on silicon were selected for the experimental implementation. Incremental FIB milling was conducted using an optimized milling strategy that produces minimum re-deposition over the sample surface. Results showed an average residual stress of {sigma} = -5.15 GPa in the CrN coating and {sigma} = +194 MPa in the Au coating. These values are in reasonable agreement with estimates obtained by other conventional techniques. The depth profiles revealed an increasing residual stress from surface to the coating/surface interface for both coatings. This observation is likely related to stress relaxation during grain growth, which was observed in microstructural cross sections, as predicted by existing models for structure-stress evolution in PVD coatings. A correlation between the observed stress gradients and the in-service mechanical behavior of the coatings is proposed. Finally, critical aspects of the technique and the influence of microstructure and elastic anisotropy on stress analysis are analyzed and discussed.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Multidimensional Effects on Ignition, Transition, and Flame Spread in Microgravity

Localized ignition is initiated by an external radiant source at the middle of a thermally thin sample under external slow flow, simulating fire initiation in a spacecraft with a slow ventilation flow. Two ignition configurations are simulated, one across the sample surface creating a line shaped flame front (two-dimensional, 2-D, configuration) and the other a small circular ignition (three-dimensional, 3-D, configuration). Ignition, subsequent transition to simultaneously upstream and downstream flame spread, and flame growth behavior are studied experimentally and theoretically. Details of our theoretical models and numerical techniques can be found in previous publications. The effects of the sample width on the transition and subsequent flame spread, and flame spread along open edges of a thermally thin paper sample are determined. Experimental observations of flame spread phenomena were conducted in the 10 s drop tower and also on the space shuttle STS-75 flight to determine the effects of oxygen concentration and external flow velocity on flame spread rate and flame growth pattern. Finally, effects of confinement in a small test chamber on the transition and subsequent flame spread are examined. The results of these studies are briefly reported.

Kashiwagi, T.↗
NASA NTRS2018

Precious Dust Two Mission Converge on Asteroid Sample Returns

Far-flung spacecraft deliver incredible views of distant worlds. But there's nothing like bringing samples back to Earth. Instruments carried by spacecraft have limitations-of power, complexity, size, and number. Their investigations leave many fundamental questions unanswered, questions that we might be able to answer if only we had samples. This summer marks the beginning of an exciting new era in sample-return missions: NASA's OSIRIS-REx spacecraft arrives at asteroid Bennu, and the Japanese Hayabusa2 spacecraft arrives at asteroid Ryugu. Both are primitive asteroids-dark remnants of Solar System formation that carry carbon and water-a type of asteroid that's never been visited before. After thoroughly mapping their respective asteroids for geology and mineralogy, each probe will collect surface samples and return them to Earth. I can't wait to study them in my laboratory. Cosmic-dust pioneer Kazu Tomeoka introduced me to the dream of sample-return missions 20 years ago. In those days, the only returned extraterrestrial samples were from the Moon. He said to his students, "In the near future, we will be able to collect samples from asteroids and comets. There will be no need to wait for meteorites or cosmic dust to come and fall from the sky. And some of you might be the first to look at those samples." This inspired my life's work: laboratory analysis of returned astromaterials.

Nakamura-Messenger, Keiko↗
NASA NTRS2001

Combustion of Metals in Reduced-Gravity and Extraterrestrial Environments

As a result of the ongoing exploration of Mars and the several unmanned and possibly manned missions planned for the near future, increased attention has been given to the use of the natural resources of the planet for rocket propellant production and energy generation. Since the atmosphere of Mars consists of approximately 95% carbon dioxide (CO2), this gas is the resource of choice to be employed for these purposes. Since many metals burn vigorously with CO2, these may be used as an energy source or as propellants for a research vehicle on the surface of Mars. Shafirovich and Goldshleger conducted experiments with spherical particles up to 2.5 mm in diameter and found that the burning process was controlled by diffusion and that the particles exhibited pulsating combustion due to superheating of the Mg vapor trapped inside a protective oxide shell. They also proposed a reaction mechanism based on the gas-phase reaction, Mg + CO2 yields MgO + CO and the heterogeneous reaction Mg + CO yields MgO + C occurring on the sample surface. In all the above studies with large Mg particles, the burning process is invariably influenced by strong convective currents that accelerate the combustion reaction and shorten the burning times. Although these currents are nearly absent in the burning of small particles, the high emissivity of the flames, rapid reaction, and small length scales make the gathering of any useful information on burning rates and flame structure very difficult. The goal of this investigation is to provide a detailed study of flame structure by taking advantage of large, free-floating spherical metal samples and their corresponding long burning times available in a weightless environment. The use of reduced gravity is essential to eliminate the intrusive buoyant flows that plague high temperature metal reactions, to remove the destructive effect of gravity on the shape of molten metal samples, and to study the combustion behavior of metals in the presence of solid oxides undisturbed by natural convection. This work presents the most complete modeling of metal particle burning to date for Mg with CO2 and O2.

Branch, M. C.↗
DOE OSTI2018

A new elliptical-beam method based on time-domain thermoreflectance (TDTR) to measure the in-plane anisotropic thermal conductivity and its comparison with the beam-offset method

Materials lacking in-plane symmetry are ubiquitous in a wide range of applications such as electronics, thermoelectrics, and high-temperature superconductors, in all of which the thermal properties of the materials play a critical part. Yet, very few experimental techniques can be used to measure in-plane anisotropic thermal conductivity. A beam-offset method based on time-domain thermoreflectance (TDTR) was previously proposed to measure in-plane anisotropic thermal conductivity. However, a detailed analysis of the beam-offset method is still lacking. Our analysis shows that uncertainties can be large if the laser spot size or the modulation frequency is not properly chosen. In this report we propose an differing approach based on TDTR to measure in-plane anisotropic thermal conductivity using a highly elliptical pump (heating) beam. The highly elliptical pump beam induces a quasi-one-dimensional temperature profile on the sample surface that has a fast decay along the short axis of the pump beam. The detected TDTR signal is exclusively sensitive to the in-plane thermal conductivity along the short axis of the elliptical beam. By conducting TDTR measurements as a function of delay time with the rotation of the elliptical pump beam to different orientations, the in-plane thermal conductivity tensor of the sample can be determined. In this work, we first conduct detailed signal sensitivity analyses for both techniques and provide guidelines in determining the optimal experimental conditions. We then compare the two techniques under their optimal experimental conditions by measuring the in-plane thermal conductivity tensor of a ZnO [11-20] sample. The accuracy and limitations of both methods are discussed.

47 OTHER INSTRUMENTATION↗
NASA NTRS1976

Argon content of the Martian atmosphere at the Viking 1 landing site - Analysis by X-ray fluorescence spectroscopy

Spectra provided by the Viking 1 X-ray fluorescence spectrometer operating in the calibration mode (without a soil sample in the analysis chamber) were analyzed to determine the argon content of the Martian atmosphere at the landing site. This was found to be less than or equal to 0.15 millibar, or not more than 2% by volume, consistent with data obtained by the entry mass spectrometer and by the mass spectrometer on the lander. It is anticipated that analysis of the K content of surface samples using X-ray fluorescence data will provide information on the evolution of the atmosphere, since most atmospheric argon is apparently produced by decay of K-40.

Clark, B. C.↗
NASA NTRS1976

The Viking mission search for life on Mars

The scientific payload on the Viking Mars landers is described. Shortly after landing, two facsimile cameras capable of stereoscopic imaging will scan the landing site area in black and white, color, and infrared to reveal gross evidence of past or present living systems. A wide range mass spectrometer will record a complete mass spectrum for soil samples from mass 12 to mass 200 every 10.3 sec. Three experiments based on different assumptions on the nature of life on Mars, if it exists, will be carried out by the bio-lab. A pyrolytic release experiment is designed to measure photosynthetic or dark fixation of carbon dioxide or carbon monoxide into organic compounds. A labelled release experiment will test for metabolic activity during incubation of a surface sample moistened with a solution of radioactively labelled simple organic compounds. A gas exchange experiment will detect changes in the gaseous medium surrounding a soil sample as the result of metabolic activity. The hardware, function, and terrestrial test results of the bio-lab experiments are discussed.

Klein, H. P.↗
DOE OSTI2014

Preparation of anti-adhesion surfaces on aluminium substrates of rubber plastic moulds using a coupling method of liquid plasma and electrochemical machining

Hard anti-adhesion surfaces, with low roughness and wear resistance, on aluminium substrates of rubber plastic moulds were fabricated via a new coupling method of liquid plasma and electrochemical machining. With the aid of liquid plasma thermal polishing and electrochemical anodic dissolution, micro/nano-scale binary structures were prepared as the base of the anti-adhesion surfaces. The anti-adhesion behaviours of the resulting aluminium surfaces were analysed by a surface roughness measuring instrument, a scanning electron microscope (SEM), a Fourier-transform infrared spectrophotometer (FTIR), an X-ray diffractometer (XRD), an optical contact angle meter, a digital Vickers micro-hardness (Hv) tester, and electronic universal testing. The results show that, after the liquid plasma and electrochemical machining, micro/nano-scale binary structures composed of micro-scale pits and nano-scale elongated boss structures were present on the sample surfaces. As a result, the anti-adhesion surfaces fabricated by the above coupling method have good anti-adhesion properties, better wear resistance and lower roughness.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Microcantilevers with embedded accelerometers for dynamic atomic force microscopy

The measurement of the intermittent interaction between an oscillating nanotip and the sample surface is a key challenge in dynamic Atomic Force Microscopy (AFM). Accelerometers integrated onto AFM cantilevers can directly measure this interaction with minimal cantilever modification but have been difficult to realize. Here, we design and fabricate high frequency bandwidth accelerometers on AFM cantilevers to directly measure the tip acceleration in commercial AFM systems. We demonstrate a simple way of calibrating such accelerometers and present experiments using amplitude modulated AFM on freshly cleaved mica samples in water to study the response of the accelerometer.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

TEM Characterization of U-Mo Irradiated with High-Energy Xe Ions

U-Mo alloys (with 7-10 wt.% Mo) with a low U-235 enrichment (< 20%) have been developed to be used in high-performance research and test reactors, replacing the current highly enriched uranium (HEU) fuels. A number of in-pile irradiation tests of U-Mo fuels show that drastic microstructural changes occurred during reactor irradiation, including the formation of U-Mo-Al interaction products and large gas-filled pores. These microstructural changes might lead to breakaway swelling and deterioration of plate mechanical integrity. Hence, it is critical to understand the underlying mechanisms of these microstructural changes in order to improve the irradiation behavior of UMo fuels. Heavy ion irradiation was employed in this study to investigate separate effects of the irradiation behavior of U-Mo fuels. 1.7 mm diameter disks punched out from UMo/ Al dispersion fuel mini-plates were irradiated with 84 MeV Xe ions at the ATLAS accelerator at Argonne National Laboratory (ANL). This particular ion source was selected for two reasons: (1) to simulate the irradiation response of the fuel to fission fragment bombardments, and (2) to study fission gas behavior, as fission gas bubble formation and growth is the primary cause of U-Mo fuel swelling. The ion-irradiated samples have been characterized with scanning electron microscopy (SEM). This study focuses on the characterization of the samples using transmission electron microscopy (TEM). With the high magnification details, microstructures in U-Mo along the ion penetration depth were revealed. The U-7Mo/Al dispersion fuel sample irradiated with 84 MeV Xe ions to a dose of 2.9 x 10{sup 17} ions/cm{sup 3} was characterized using TEM. The TEM results exhibit that the sample microstructure varies along the ion penetration depth. Near the sample surface (zone A) is a layer of nano-crystalline U-Mo-Al interdiffusion product. After passing through zone A, the Xe ions resided in zone B, where gas bubbles formed in U-Mo. TEM images of this region displayed that large gas bubbles formed on grain boundaries and high-density nano-bubbles lay inside grains. The random distribution of intragranular bubbles indicates that the irradiation conditions of this sample cannot lead to gas bubble superlattice formation. Outside of the Xe penetration depth (zone C), significant amount of α-uranium precipitates were identified. The fact that no α-uranium precipitates were found in zone B suggests that the dose rate in this irradiation is sufficient to facilitate a phase reversal by means of a displacement spike mechanism. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

Deposition of metallic gallium on re-crystallized ceramic material during focused ion beam milling

We report a new kind of artifact observed in the preparation of a TEM sample of zirconia by FIB, which consists in the deposition of metallic gallium nano-dots on the TEM sample surface. High resolution TEM images showed a microstructure of fine equiaxed grains of ∼ 5 nm, with some of them possessing two particular characteristics: high contrast and well-defined fast Fourier transform. These grains could not be identified as any phase of zirconia but it was possible to identify them as gallium crystals in the zone axis [110]. Based on HRTEM simulations, the possible orientations between zirconia substrate and deposited gallium are discussed in terms of lattice mismatch and oxygen affinity. - Highlights: • We show a new type of artifact induced during preparation of TEM samples by FIB. • Deposition of Ga occurs due to its high affinity for oxygen. • Materials with small grain size (∼ 5 nm) could promote Ga deposition. • Small grain size permits the elastic accommodation of deposited Ga.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The performance of additively manufactured Haynes 282 in supercritical CO 2

The use of supercritical carbon dioxide (sCO 2 ) as a working fluid is garnering interest in next generation power production systems due to the possibility of increased operational efficiencies and lower associated costs. Its implementation requires alloys with excellent high temperature strength and corrosion resistance, which makes Haynes 282® (H282) a suitable candidate. With increasing adoption of additive manufacturing (AM) in the energy industry, there is a need to investigate long-term sCO2 exposure on AM produced materials. Additively manufactured H282 (AM-H282) samples built using laser powder bed fusion in two different orientations were analyzed through imaging, gravimetric analysis, and room-temperature tensile testing before and after 1000-h exposure to CO 2 at 750 °C and 20 MPa. Performed imaging included observation of the sample surfaces and of the material bulk (cross sections) through means of Scanning Electron Microscopy (SEM) and optical microscopy. In comparison to wrought H282, it was found that the exposed material exhibited a similar Cr 2 O 3 oxide protective layer about 2 μm in thickness with additional top-surface TiO 2 oxide and carbon-rich precipitates. It was also similarly observed that internal oxidation was present but limited to a depth of 20 μm, and a 1–3 μm γ’ denuded region appeared to surround all internal and surface oxidation. Thermal aging effects were noted with the precipitation of needle-like structures in the γ/γ’ matrix and a coarsening of the γ’ precipitates from 28 nm to 73 nm. Mass measurements analyzing oxide precipitation revealed a larger increase compared to wrought, representing an approximate 20% difference. Tensile testing results showed similar behavior to wrought with a slight increase in yield strength and a large reduction in elongation in the exposed samples.

36 MATERIALS SCIENCE↗