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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Structural and double magnetic transitions in the frustrated spin- 1 2 capped-kagome antiferromagnet ( RbCl ) Cu 5 P 2 O 10

The structural and magnetic properties of the geometrically frustrated spin- 1 2 capped-kagome antiferromagnet (RbCl) Cu 5 P 2 O 10 are investigated via temperature-dependent x-ray diffraction, magnetization, heat capacity, and 31 P NMR experiments on a polycrystalline sample. It undergoes a structural transition at around T t ≃ 310 K from a high-temperature trigonal (P ¯3m1) to a low-temperature monoclinic (C2/c) unit cell, where the low-temperature structure features the capped-kagome geometry of Cu 2+ ions. Interestingly, it shows the onset of two successive magnetic transitions at T N1 ≃ 20 K and T N2 ≃ 7 K. The shape of the 31 P NMR spectra unfolds the possible nature of the transitions below T N1 and T N2 to be of incommensurate and commensurate antiferromagnetic type, respectively. A large value of the Curie-Weiss temperature as compared to T N1 sets the frustration parameter f ≃ 8, ensuring strong magnetic frustration in the compound. From the 31 P NMR spin-lattice relaxation rate, the leading antiferromagnetic exchange coupling is estimated to be J/k B ≃ 117 K. Furthermore, these unusual double magnetic transitions make this compound beguiling for further investigations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Localized Control of Curie Temperature in Perovskite Oxide Film by Capping-Layer-Induced Octahedral Distortion

With reduced dimensionality, it is often easier to modify the properties of ultrathin films than their bulk counterparts. Strain engineering, usually achieved by choosing appropriate substrates, has been proven effective in controlling the properties of perovskite oxide films. An emerging alternative route for developing new multifunctional perovskite is by modification of the oxygen octahedral structure. Here we report the control of structural oxygen octahedral rotation in ultrathin perovskite SrRuO 3 films by the deposition of a SrTiO 3 capping layer, which can be lithographically patterned to achieve local control. Here, using a scanning Sagnac magnetic microscope, we show an increase in the Curie temperature of SrRuO 3 due to the suppression octahedral rotations revealed by the synchrotron x-ray diffraction. Lastly, this capping-layer-based technique may open new possibilities for developing functional oxide materials.

36 MATERIALS SCIENCE↗
DOE OSTI2019

E-Area LLWF Final Closure Cap Design – Constructability Evaluation Criteria for the Plot 8 and NR07E Disposal Areas

SRNS Design Engineering has been asked to complete a constructability evaluation of the proposed final closure cap designs for the Plot 8 (Engineered Trenches ET07, ET08, and ET09) and 643-7E NRCDA (NR07E) disposal areas located outside the original E-Area Low-Level Waste Facility (ELLWF) footprint. This memorandum presents the guidelines and criteria for the constructability evaluation. A new conceptual design for the ELLWF closure cap is not requested at this time.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Thermal Instability in the Manufacturing of Wind Turbine Blade Spar Caps

As wind turbine blades continue to scale in length and total mass, the acceptability of traditional approaches for the engineering of processes to build these products has reached a limit. The continued need to reduce the levelized cost of energy (LCOE) drives manufacturing cycle times lower and the net mass of critical components challenges even the most experienced fabricators to meet the quality requirements for safe operating performance over the 25-year design life of the blade. In trying to reduce cycle time for key components of wind turbines, manufacturers discovered occasional buckling of fibers in wind turbine blade spar caps. The cause of the buckling was unknown. The goal of this project was to show that a comprehensive simulation, which considered all of the physics of the VARTM process, could identify the cause of the fiber buckling in spar caps that has been observed during the manufacturing process. Ultimately, the simulation determined the manufacturing process and parameters could lead to significant compressive stresses in the fibers eventually causing buckling. Simulation results suggest that the stress introduced from friction is the largest source of compressive stress in the fibers, the stress from the weight of gravity is significant but secondary, and the compressive stress from cure shrinkage does not play a significant role in the buckling of fibers. This report provides details of the testing and simulation methodology used to identify the cause of the fiber buckling.

17 WIND ENERGY↗
DOE OSTI2022

Thermal Instability in the Manufacturing of Wind Turbine Blade Spar Caps – Phase 2

As the wind turbine industry continues to develop, the technology surrounding the design, development, and manufacturing of blades requires advancement as well. Wind turbine blades continue to increase in size, increasing the cost and time associated with manufacturing. Simulation driven manufacturing cycle design is required for the industry to maintain manufacturing schedules and optimize the manufacturing process. A recent effort to reduce the cycle time of wind blade spar caps encountered a recurring manufacturing defect during the exotherm and curing of the resin system after filling in the vacuum-assisted resin transfer molding (VARTM) process. Thermal waves developed in sections of the spar cap resulting in unacceptable part tolerances, requiring the parts to be thrown out. The first phase of this IACMI project focused on characterizing the fabric and epoxy system used in manufacturing and simulating the manufacturing process to determine the root cause of the thermal waves. The second phase of this project refined and validated the manufacturing simulations. The simulation workflow was then used to analyze multiple cure cycle options to determine if the thermal waves would appear. The estimated filling time from the filling simulation was shown to match well to experiment, and the temperature history from the curing simulation lined up well with experiment. This indicates that these simulations could be used to evaluate future curing cycles to be used with manufacturing. It is recommended that the distortion simulation work be completed for this project, as it would allow for further manufacturing cycle evaluation through the prediction of stresses and strains in the part. This could provide indicators of defects like the thermal waves seen in manufacturing earlier.

17 WIND ENERGY↗
DOE OSTI2021

Chalcogenide Glass-Capped Fiber-Optic Sensor for Real-Time Temperature Monitoring in Extreme Environments

We demonstrate a novel chalcogenide glass (ChG)-capped optical fiber temperature sensor capable of operating within harsh environment. The sensor architecture utilizes the heat-induced phase change (amorphous-to-crystalline) property of ChGs, which rapidly (80–100 ns) changes the optical properties of the material. The sensor response to temperature variation around the phase change of the ChG cap at the tip of the fiber provides abrupt changes in the reflected power intensity. This temperature is indicative of the temperature at the sensing node. We present the sensing performance of six different compositions of ChGs and a method to interpret the temperature profile between 440 °C and 600 °C in real-time using an array structure. The unique radiation-hardness property of ChGs makes the devices compatible with high-temperature and high-radiation environments, such as monitoring the cladding temperature of Light Water (LWR) or Sodium-cooled Fast (SFR) reactors.

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

CAPS PMssa Aerosol Extinction and SSA Data

We collected rapid (1 second time response) measurements of aerosol extinction and scattering (Mm-1) using an Aerodyne CAPS PMssa deployed during LASIC (as part of the LASIC SSA-constraint study) to measure ambient SSA at 530 nm wavelength to compare with other optical measurement methods. Measured from August 4 to September 22, 2017. Sampled from both PM1 and PM10 inlets. CAPS PMssa monitors have been tested extensively for PM2.5 and smaller particle sizes, but not for particles greater than 2,500 nm in diameter (i.e., PM10). The data were collected in order to provide an independent measurement of aerosol single scattering albedo at 530 nm wavelength to compare with ARM standard methods.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1972

Effects of interplanetary magnetic field azimuth on auroral zone and polar cap magnetic activity

During relatively quiet times in the period 1964-1968, AE is found to be greater when the interplanetary magnetic field (b sub IMF) is directed toward the sun in Jan., Feb., and Apr., and when B sub IMF is directed away from the sun in Oct. to Dec. Using Murmansk hourly H values and the AE components, AU and AL, it is shown that this sector dependence is present only in the negative H deviations. This observation supports the idea that negative bay magnitudes are determined chiefly by particle-produced ionization, while positive bay magnitudes are rather insensitive to increases in particle precipitation. The ratio of DP2-type magnetic activity in the southern polar cap to that in the northern polar cap is found to be greater by a factor of about 1.75 for B sub IMF toward the sun.

Burch, J. L.↗
NASA NTRS1972

Observations of oceanic white caps for moderate to highwind speeds

A series of photographs of sea surface whitecap conditions for wind speeds of 10 to 25 m/sec was obtained and analyzed for areal coverage of white water. The results are in good agreement with semiempirical calculations based on the wind speed and the development of the wave spectrum only when the contribution of thin foam streaks oriented in the direction of the wind is neglected. Since both the actively forming whitecaps and the thin foam streaks contribute significantly to the microwave emissivity of the sea surface, it is important that the foam streaks be included in the theory but differentiated from large white caps and foam patches. A simple relationship that accounts for the foam streaks based on the rate of energy transfer, the wind speed, and the wave spectrum is proposed. By means of empirically derived constant terms for the microwave signatures of white caps and foam streaks, this theory was adapted to the prediction of the increase in brightness temperature due to foam, with reasonable results to wind speeds of 20 m/sec.

Ross, D. B.↗
NASA NTRS1971

Midday auroral observations in the oval, cusp region, and polar cap.

Evaluation of combined photographic and photometric measurements made on the 1969 NASA airborne expedition, yielding a description of the midday oval, cusp region, and polar cap auroral precipitation at low magnetic activity (Kp = 0, 1+). The observations delineate three regions through the description of the type of aurora observed and the photometrically inferred change in energy of the particles: (1) the region in and equatorward of the oval where greater than 3-keV electrons are associated with 6300 A/4278 A ratios less than or equal to 1 and with a diffuse glow or structured arcs; (2) the cusp region where electrons of several hundred electron volts and spikes of more energetic electrons are associated with 6300 A/4278 A ratios between 10 and 35 in broken, fragmented, rayed features and patches; (3) the polar cap where discrete earth-sun-aligned arcs have height luminosity profiles in 5577 A, 6300 A (forbidden O I), and 4278 A (N2(+)) that suggest incoming electrons with an energy spectrum of 2-keV characteristic energy above a low-energy (few hundred electron volts) background.

Romick, G. J.↗
NASA NTRS1972

Identification of carbon dioxide frost on the Martian polar caps.

Spectra of the Martian south polar cap produced by the techniques of Fourier spectroscopy show 11 narrow features attributed to the composition of the polar cap. Through comparison with laboratory spectra, all 11 have been identified as solid CO2 absorptions.

Larson, H. P.↗
NASA NTRS1973

Access of solar protons to the earth's polar caps.

Energetic solar proton observations in the interplanetary medium by Explorer 33 and Explorer 35 and over the polar caps by Injun 5 during the period from September 1968 through March 1970 have been examined in detail. The solar proton intensities observed over the polar regions were compared with the interplanetary intensities on an absolute basis. The high polar latitude (HPL) proton intensities tracked the magnetic field aligned interplanetary intensities well (solar-antisolar intensities as determined from the sectored Explorer data). The tracking was in agreement with the open magnetosphere model about 90% of the time - i.e., the intensities observed on the HPL magnetic lines of force, which would be connected to magnetic lines of force from the sun in an interconnected geomagnetic and interplanetary magnetic field, were in agreement with the maximum intensity of the interplanetary proton pitch angle distribution. The intensities observed at the HPL region of the opposite polar cap were in agreement with the minimum intensity of the interplanetary pitch angle distribution. The low polar latitude intensities generally tracked the maximum interplanetary intensity very well.

Fennell, J. F.↗
NASA NTRS1974

Polar cap auroral electron fluxes observed with Isis 1

Three types of auroral particle precipitation have been observed over the polar caps, well inside the auroral oval, by means of the soft particle spectrometer on the Isis 1 satellite. The first type is a uniform, very soft (about 100 eV) electron 'polar rain' over the entire polar cap; this may well be present with very weak intensity at all times, but it is markedly enhanced during worldwide geomagnetic storms. A second type of precipitation is a structured flux of electrons with energies near 1 keV, suggestive of localized 'polar showers'; it seems likely that these are the cause of the sun-aligned auroral arcs that have been observed during moderately quiet conditions. During periods of intense magnetic disturbance this precipitation can become very intense and exhibit a characteristic pattern that we have come to call a 'polar squall'.

Winningham, J. D.↗
NASA NTRS1974

Hot vacuum creep forming of scale shuttle external tank dome caps

The feasibility of forming shuttle external tank dome caps by hot vacuum creep was investigated for a sub-scale configuration. Aluminum 2219-T37 at an elevated temperature equivalent to the artificial aging time and temperature was used to produce the T87 condition while achieving MIL-HBK -5 properties of 2219-T87 aluminum alloy material. A feasibility analysis was conducted in two phases: the design and build of a sub-scale hot vacuum creep forming (HVCF) die and the forming evaluation of various cap configurations. The contour was constant in all evaluations. This configuration was found to be too severe for the limited forming force available by HVCF.

Thomas, A. O.↗
NASA NTRS1975

On the interpretation of low-energy particle access to the polar caps

Neither particle access to the polar caps by motion along magnetospheric field lines connected to the interplanetary field (in the 'open' model) nor particle access to the polar caps by combined diffusive and convective motion across magnetospheric field lines (in the 'closed' model) adequately explains the available data. The fact that data exist that are difficult to interpret with one model does not automatically confirm the other model.

Michel, F. C.↗
NASA NTRS1975

Electromagnetic induction in spherical cap current layers under lunar and terrestrial conditions

Attention is given to electromagnetic induction in infinitesimally thin spherical cap current layers of arbitrary size and arbitrary axisymmetric integrated conductivity, taking into account a location at nonzero but otherwise arbitrary depth beneath the surface of observation. The description of a theoretical model is presented and the induced fields computed from the theoretical formulas for several different spherical cap models are discussed.

Schubert, G.↗