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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 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Hole Production in High-Strength Steels by Plasma Incision and Reaming

Hole production in high-strength steels (in particular, manganese steels) by plasma incision and reaming is considered. Thermal conditions are identified for preliminary plasma incision of holes with subsequent reaming. Phase and structural transformations in the surface layer after plasma treatment greatly improve the efficiency of subsequent cutting. Additional plasma heating of the machined hole surface after plasma incision is proposed.

42 ENGINEERING↗
NASA NTRS1984

On orbit surfacing of thermal control surfaces

Substrates to be contaminated and contamination source were prepared. Additional information on paint spray method apparatus was obtained. Silver teflon second surface mirror samples and S 13 GLO paint samples were mounted, photographed under the microscope and measured to establish baseline data. Atomic oxygen cleaning and spray painting are being considered. Electrostatic powder and plasma spray coating systems appear to have serious drawbacks.

Racette, G. W.↗
NASA NTRS1988

Computed potential energy surfaces for chemical reactions

The minimum energy path for the addition of a hydrogen atom to N2 is characterized in CASSCF/CCI calculations using the (4s3p2d1f/3s2p1d) basis set, with additional single point calculations at the stationary points of the potential energy surface using the (5s4p3d2f/4s3p2d) basis set. These calculations represent the most extensive set of ab initio calculations completed to date, yielding a zero point corrected barrier for HN2 dissociation of approx. 8.5 kcal mol/1. The lifetime of the HN2 species is estimated from the calculated geometries and energetics using both conventional Transition State Theory and a method which utilizes an Eckart barrier to compute one dimensional quantum mechanical tunneling effects. It is concluded that the lifetime of the HN2 species is very short, greatly limiting its role in both termolecular recombination reactions and combustion processes.

Walch, Stephen P.↗
NASA NTRS1993

From minerals to rocks: Toward modeling lithologies with remote sensing

High spectral resolution imaging spectroscopy will play an important role in future planetary missions. Sophisticated approaches will be needed to unravel subtle, super-imposed spectral features typically of natural systems, and to maximize the science return of these instruments. Carefully controlled laboratory investigations using homogeneous mineral separates have demonstrated that variations due to solid solution, changes in modal abundances, and the effects of particle size are well understood from a physical basis. In many cases, these variations can be modeled quantitatively using photometric models, mixing approaches, and deconvolution procedures. However, relative to the spectra of individual mineral components, reflectance spectra of rocks and natural surfaces exhibit a reduced spectral contrast. In addition, soils or regolith, which are likely to dominate any natural planetary surface, exhibit spectral properties that have some similarities to the parent materials, but due to weathering and alteration, differences remain that cannot yet be fully recreated in the laboratory or through mixture modeling. A significant challenge is therefore to integrate modeling approaches to derive both lithologic determinations and include the effects of alteration. We are currently conducting laboratory investigations in lithologic modeling to expand upon the basic results of previous analyses with our initial goal to more closely match physical state of natural systems. The effects of alteration are to be considered separately.

Mustard, John F.↗
NASA NTRS1998

The cytoskeleton of Drosophila-derived Schneider line-1 and Kc23 cells undergoes significant changes during long-term culture

Insect cell cultures derived from Drosophila melanogaster are increasingly being used as an alternative system to mammalian cell cultures, as they are amenable to genetic manipulation. Although Drosophila cells are an excellent tool for the study of genes and expression of proteins, culture conditions have to be considered in the interpretation of biochemical results. Our studies indicate that significant differences occur in cytoskeletal structure during the long-term culture of the Drosophila-derived cell lines Schneider Line-1 (S1) and Kc23. Scanning, transmission-electron, and immunofluorescence microscopy studies reveal that microfilaments, microtubules, and centrosomes become increasingly different during the culture of these cells from 24 h to 7-14 days. Significant cytoskeletal changes are observed at the cell surface where actin polymerizes into microfilaments, during the elongation of long microvilli. Additionally, long protrusions develop from the cell surface; these protrusions are microtubule-based and establish contact with neighboring cells. In contrast, the microtubule network in the interior of the cells becomes disrupted after four days of culture, resulting in altered transport of mitochondria. Microtubules and centrosomes are also affected in a small percent of cells during cell division, indicating an instability of centrosomes. Thus, the cytoskeletal network of microfilaments, microtubules, and centrosomes is affected in Drosophila cells during long-term culture. This implies that gene regulation and post-translational modifications are probably different under different culture conditions.

NASA Discipline Developmental Biology↗
DOE OSTI2018

Fluoroethylene Carbonate Induces Ordered Electrolyte Interface on Silicon and Sapphire Surfaces as Revealed by Sum Frequency Generation Vibrational Spectroscopy and X-ray Reflectivity

Here, the cyclability of silicon anodes in lithium ion batteries (LIBs) is affected by the reduction of the electrolyte on the anode surface to produce a coating layer termed the solid electrolyte interphase (SEI). One of the key steps for a major improvement of LIBs is unraveling the SEI’s structure-related diffusion properties as charge and discharge rates of LIBs are diffusion-limited. To this end, we have combined two surface sensitive techniques, sum frequency generation (SFG) vibrational spectroscopy, and X-ray reflectivity (XRR), to explore the first monolayer and to probe the first several layers of electrolyte, respectively, for solutions consisting of 1 M lithium perchlorate (LiClO 4 ) salt dissolved in ethylene carbonate (EC) or fluoroethylene carbonate (FEC) and their mixtures (EC/FEC 7:3 and 1:1 wt %) on silicon and sapphire surfaces. Our results suggest that the addition of FEC to EC solution causes the first monolayer to rearrange itself more perpendicular to the anode surface, while subsequent layers are less affected and tend to maintain their, on average, surface-parallel arrangements. This fundamental understanding of the near-surface orientation of the electrolyte molecules can aid operational strategies for designing high-performance LIBs.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Investigation of intrinsic and extrinsic defects effective role on producing intense red emission in ZnO:Eu nanostructures

Highlights: • Effective role of defects on producing red emission at indirect excitation. • V{sub Zn} and V{sub O} defects have important role on energy transfer. • Mg related defects and Zn{sub i} defects were responsible for blue emission. • Extrinsic and intrinsic defects mediated energy transfer to sensitize Eu{sup 3+} ions. • Decrease of red emission because of diminishing in oxygen vacancy. - Abstract: Europium doped ZnO nanorads and nanosheets were synthesized by hydrothermal method. Effects of Mg doping, morphology and annealing in oxygen ambient on structural and optical properties of ZnO nanostructures were investigated using X-ray diffraction (XRD), particle size analysis (PSA), thermo gravimetric analysis (TGA), differential thermal analysis (DTA), differential thermo gravimetry (DTG), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). This study recommends that both of intrinsic and extrinsic defects facilitate energy transfer (ET) from the ZnO host to Eu{sup 3+} ions and consequently have efficient role on producing intense red emission at indirect excitation. The results also showed that annealing process improved the crystal structure of ZnO nanosheets due to decrease of surface defects; however decreased ET and red emission because of diminishing in oxygen vacancy. In addition in ZnO nanorods sample with more surface area in comparison with ZnO nanosheets sample deep level emissions are enhanced.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Research on photoelectric properties of n-GaN (0001) surface with point defects via first-principles

In order to reveal the influence of n-type doping and point defects on the electronic and optical properties of GaN (0001) surface, the pristine and defective n-GaN (0001) surface models are established. The formation energy, work function, atomic structure, electronic and optical properties of these surfaces are discussed by first-principles calculations. The results show that the defects have the strong tendency to be close to the surface position, and the N interstitial defect (N{sub i}) and the Ga vacancy (V{sub Ga}) are easily formed. The work function of the surface with V{sub Ga} drops the greatest, and the conductivity of n-type increases. In addition, the absorption coefficient of the surface with various defects is smaller than that of the pristine n-type surface. The appropriate amount of Ga vacancies can increase the probability of electron emission, but it is not conducive to the absorption of photons.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

A low energy muon spin rotation and point contact tunneling study of niobium films prepared for superconducting cavities

Point contact tunneling and low energy muon spin rotation are used to probe, on the same samples, the surface superconducting properties of micrometer thick niobium films deposited onto copper substrates using different sputtering techniques: diode, dc magnetron and HIPIMS. The combined results are compared to radio-frequency tests performances of RF cavities made with the same processes. Degraded surface superconducting properties are found to correlate to lower quality factors and stronger Q-slope. In addition, both techniques find evidence for surface paramagnetism on all samples and particularly on Nb films prepared by HIPIMS.

LE-mu SR↗
DOE OSTI2016

SU-F-T-424: Mitigation of Increased Surface Dose When Treating Through A Carbon Fiber Couch Top

Purpose: To study the effect of the Varian carbon fiber couch top on surface dose for patients being treated using single PA beams in the supine position and to identify simple methods for surface dose reduction. Methods: Measurements of surface dose were obtained in Solid Water phantoms using both a parallel plate ionization chamber (PTW Advanced Markus) and EBT2 Radiochromic films for both 6 and 10MV photons. All measurements were referenced to a depth considered a typical for PA Spine fields. Techniques used to reduce the surface dose included introducing an air standoff using Styrofoam sheets to suspend the phantom surface above the couch top and by adding a thin high Z scattering foil on the table surface. Surface doses were evaluated for typical field sizes, standoff heights, and various scattering materials. Comparisons were made to the surface dose obtainable when treating through a Varian Mylar covered tennis racket style couch top. Results: Dependence on typical spine field sizes was relatively minor. Dependence on air gap was much more significant. Surface doses decreased exponentially with increases in air standoff distance. Surface doses were reduced by approximately 50% for an air gap of 10cm and 40% for a 15cm air gap. Surface doses were reduced by an additional 15% by the addition of a 1mm Tin scattering foil. Conclusion: Using simple techniques, it is possible to reduce the surface dose when treating single PA fields through the Varian carbon fiber couch top. Surface doses can be reduced to levels observed when treating though transparent Mylar tops by adding about 15 cm of air gap. Further reductions are possible by adding thin scattering foils, such as Tin or Lead, on the couch surface. This is a low cost approach to reduce surface dose when using the Varian carbon fiber couch top.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS2001

High-Frequency Focused Water-Coupled Ultrasound Used for Three-Dimensional Surface Depression Profiling

To interface with other solids, many surfaces are engineered via methods such as plating, coating, and machining to produce a functional surface ensuring successful end products. In addition, subsurface properties such as hardness, residual stress, deformation, chemical composition, and microstructure are often linked to surface characteristics. Surface topography, therefore, contains the signatures of the surface and possibly links to volumetric properties, and as a result serves as a vital link between surface design, manufacturing, and performance. Hence, surface topography can be used to diagnose, monitor, and control fabrication methods. At the NASA Glenn Research Center, the measurement of surface topography is important in developing high-temperature structural materials and for profiling the surface changes of materials during microgravity combustion experiments. A prior study demonstrated that focused air-coupled ultrasound at 1 MHz could profile surfaces with a 25-m depth resolution and a 400-m lateral resolution over a 1.4-mm depth range. In this work, we address the question of whether higher frequency focused water-coupled ultrasound can improve on these specifications. To this end, we employed 10- and 25-MHz focused ultrasonic transducers in the water-coupled mode. The surface profile results seen in this investigation for 25-MHz water-coupled ultrasound, in comparison to those for 1-MHz air-coupled ultrasound, represent an 8 times improvement in depth resolution (3 vs. 25 m seen in practice), an improvement of at least 2 times in lateral resolution (180 vs. 400 m calculated and observed in practice), and an improvement in vertical depth range of 4 times (calculated).

Roth, Don J.↗
NASA NTRS1992

Development of physical and mathematical models for the Porous Ceramic Tube Plant Nutrification System (PCTPNS)

A physical model of the Porous Ceramic Tube Plant Nutrification System (PCTPNS) was developed through microscopic observations of the tube surface under various operational conditions. In addition, a mathematical model of this system was developed which incorporated the effects of the applied suction pressure, surface tension, and gravitational forces as well as the porosity and physical dimensions of the tubes. The flow of liquid through the PCTPNS was thus characterized for non-biological situations. One of the key factors in the verification of these models is the accurate and rapid measurement of the 'wetness' or holding capacity of the ceramic tubes. This study evaluated a thermistor based moisture sensor device and recommendations for future research on alternative sensing devices are proposed. In addition, extensions of the physical and mathematical models to include the effects of plant physiology and growth are also discussed for future research.

Tsao, D. Teh-Wei↗
DOE OSTI2023

Machine Learning-Enabled Quantitative Analysis of Optically Obscure Scratches on Nickel-Plated Additively Manufactured (AM) Samples

Additively manufactured metal components often have rough and uneven surfaces, necessitating post-processing and surface polishing. Hardness is a critical characteristic that affects overall component properties, including wear. This study employed K-means unsupervised machine learning to explore the relationship between the relative surface hardness and scratch width of electroless nickel plating on additively manufactured composite components. The Taguchi design of experiment (TDOE) L9 orthogonal array facilitated experimentation with various factors and levels. Initially, a digital light microscope was used for 3D surface mapping and scratch width quantification. However, the microscope struggled with the reflections from the shiny Ni-plating and scatter from small scratches. To overcome this, a scanning electron microscope (SEM) generated grayscale images and 3D height maps of the scratched Ni-plating, thus enabling the precise characterization of scratch widths. Optical identification of the scratch regions and quantification were accomplished using Python code with a K-means machine-learning clustering algorithm. The TDOE yielded distinct Ni-plating hardness levels for the nine samples, while an increased scratch force showed a non-linear impact on scratch widths. The enhanced surface quality resulting from Ni coatings will have significant implications in various industrial applications, and it will play a pivotal role in future metal and alloy surface engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Atomistic modeling of energy band alignment in CdTe(1 0 0) and CdTe(1 1 1) surfaces

An atomic-scale perspective of energy band alignment in CdTe surfaces has not been spatially studied despite the major role surfaces play in forming interfaces within CdTe-based thin film photovoltaic devices. Atomistic modeling based on density functional theory coupled with surface Green’s function is used for calculating energy band alignment of CdTe surfaces. The CdTe(1 0 0) ((1×1) and c(2×2) reconstruction) and CdTe(1 1 1) ((1×1) and (2×2) reconstruction) facets without and with surface relaxation provide insightful band bending characteristics that influence charge carrier transport. Results show that unrelaxed (1×1) CdTe(1 0 0) and CdTe(1 1 1) surfaces bend the valence band downward with surface polarity dictating the surface potential magnitude. The reconstructed CdTe(1 0 0) c(2×2) and CdTe(1 1 1) (2×2) surfaces result in favorable surface electronic features in relation to their unreconstructed variants. In addition, the structurally relaxed CdTe(1 1 1) surfaces develop an internal energy cusp potential that may enhance hole charge transport toward the back of CdTe solar cell devices. In conclusion, energy band alignments calculated within the study lead to a detailed understanding of how CdTe surfaces may affect CdTe-based thin film photovoltaic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Complementary Effects of Mg and Cu Incorporation in Stabilizing the Cobalt-Free LiNiO 2 Cathode for Lithium-Ion Batteries

Since the discovery of LiNiO 2 several decades ago, a new era of electric vehicles demanding high-energy-density lithium-ion batteries (LIBs) has recently rebooted the interest in this cathode material to eliminate the dependence on expensive and scarcely available cobalt. However, LiNiO 2 has been plagued by cycle instability, thermal instability, and air instability. We present here an exploration of the mutual interaction of magnesium and copper in stabilizing the cobalt-free LiNiO 2 cathode. Although Mg doping is beneficial for the robustness of the bulk structure of LiNiO 2 , surface characterization results of Mg-doped LiNiO 2 implies the need for further surface protection. To that end, we have incorporated Cu in addition to Mg in that Cu stabilizes the surface of Mg-doped LiNiO 2 by forming a protective stable surface layer without harming the bulk. Notable variations of the surface residual lithium composition (Li Li 2 CO 3 /Li LiOH ) along with the incorporation of stabilizers are also discussed. The harmony between Mg and Cu with as little as 0.5 atom % Mg and 0.3 atom % Cu significantly enhances the specific energy and cycle life of LiNiO 2 . Furthermore, this study demonstrates how the co-incorporation of optimal dopants can help stabilize both the bulk and surface and provides new insights toward developing cobalt-free layered oxide cathodes for high-energy-density LIBs.

25 ENERGY STORAGE↗
DOE OSTI2017

Atom Probe Tomography Unveils Formation Mechanisms of Wear-Protective Tribofilms by ZDDP, Ionic Liquid, and Their Combination

The development of advanced lubricant additives has been a critical component in paving the way for increasing energy efficiency and durability for numerous industry applications. However, the formation mechanisms of additive-induced protective tribofilms are not yet fully understood because of the complex chemomechanical interactions at the contact interface and the limited spatial resolution of many characterizing techniques currently used. In this paper, the tribofilms on a gray cast iron surface formed by three antiwear additives are systematically studied; a phosphonium-phosphate ionic liquid (IL), a zinc dialkyldithiophosphate (ZDDP), and an IL+ZDDP combination. All three additives provide excellent wear protection, with the IL+ZDDP combination exhibiting a synergetic effect, resulting in further reduced friction and wear. Atom probe tomography (APT) and scanning transmission electron microscopy (STEM) imaging and electron energy loss spectroscopy (EELS) were used to interrogate the subnm chemistry and bonding states for each of the tribofilms of interest. The IL tribofilm appeared amorphous and was Fe, P, and O rich. Wear debris particles having an Fe-rich core and an oxide shell were present in this tribofilm and a transitional oxide (Fe 2 O 3 )-containing layer was identified at the interface between the tribofilm and the cast iron substrate. The ZDDP+IL tribofilm shared some of the characteristics found in the IL and ZDDP tribofilms. Finally, tribofilm formation mechanisms are proposed on the basis of the observations made at the atomic level.

36 MATERIALS SCIENCE↗
NASA NTRS2006

A Time Series Approach for Soil Moisture Estimation

Soil moisture is a key parameter in understanding the global water cycle and in predicting natural hazards. Polarimetric radar measurements have been used for estimating soil moisture of bare surfaces. In order to estimate soil moisture accurately, the surface roughness effect must be compensated properly. In addition, these algorithms will not produce accurate results for vegetated surfaces. It is difficult to retrieve soil moisture of a vegetated surface since the radar backscattering cross section is sensitive to the vegetation structure and environmental conditions such as the ground slope. Therefore, it is necessary to develop a method to estimate the effect of the surface roughness and vegetation reliably. One way to remove the roughness effect and the vegetation contamination is to take advantage of the temporal variation of soil moisture. In order to understand the global hydrologic cycle, it is desirable to measure soil moisture with one- to two-days revisit. Using these frequent measurements, a time series approach can be implemented to improve the soil moisture retrieval accuracy.

soil moisture↗