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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
NASA NTRS1974

X-ray diffraction identification of minerals in lunar regolith returned by Luna 16 automatic station

The methods of powder and monocrystal X-ray diffraction served in identifying the mineral composition of gross samples of regolith from different levels of the drill core and about 80 individual regolith particles returned by the Luna 16 station. It was established that the Sea of Fertility regolith includes pyroxenes of the augite-pigeonite series, anorthites, ilmenite, olivines, spinels, alpha cristobalite, iron particles, glass, and several as yet unidentified particles. Crystallographic and roentgenometric data are given for all the lunar minerals found.

Makarov, Y. S.↗
NASA NTRS1977

Germanium-silicon solid solutions

An experiment on melting and directional crystallization of an antimony (Sb) doped germanium silicon (GeSi) solid solution was designed for the Apollo-Soyuz Test Project (ASTP) to study the possibility of using zero-g conditions for obtaining solid-solution monocrystals with uniformly distributed components. Crystallization in the zero-g environment did not occur under ideal stationary growth and segregation conditions. Crystallization under zero-g conditions revealed the heterogeneous nature of Si and Sb distribution in the cross sections of crystals. The presence of the radial thermal gradient in the multipurpose furnace could be one of the reasons for such Si and Sb distribution. The structure of space-grown crystals correlates with the nature of heterogeneities of Si and Sb distribution in crystals. The type of surface morphology and the contour observed in space-grown crystals were never observed in ground-based crystals and indicate the absence of wetting of the graphitized walls of the ampoule by the melt during melting and crystallization.

Zemskov, V. S.↗
NASA NTRS1982

Materials for advanced turbine engines. Volume 1: Advanced blade tip seal system

Project 3, the subject of this technical report, was structured toward the successful engine demonstration of an improved-efficiency, long-life, tip-seal system for turbine blades. The advanced tip-seal system was designed to maintain close operating clearances between turbine blade tips and turbine shrouds and, at the same time, be resistant to environmental effects including high-temperature oxidation, hot corrosion, and thermal cycling. The turbine blade tip comprised an environmentally resistant, activated-diffussion-bonded, monocrystal superalloy combined with a thin layer of aluminium oxide abrasive particles entrapped in an electroplated NiCr matrix. The project established the tip design and joint location, characterized the single-crystal tip alloy and abrasive tip treatment, and established the manufacturing and quality-control plans required to fully process the blades. A total of 171 blades were fully manufactured, and 100 were endurance and performance engine-tested.

Zelahy, J. W.↗
NASA NTRS1986

Multifrequency dial sensing of the atmospheric gaseous constituents using the first and second harmonics of a tunable CO2 laser radiation

The results of field measurements of concentration of some gaseous components of the atmosphere along the paths, in Sofia, Bulgaria, using a gas analyzer based on the use of a CO2 laser radiation frequency-doubled with ZnGeP2 monocrystals are presented. The gas analyzer is a traditional long path absorption meter. Radiation from the tunable CO2 laser of low pressure and from an additional He-Ne laser is directed to a colliminating hundredfold Gregori telescope with a 300 mm diameter of the principal mirror. The dimensions of the mirrors of a retroreflector 500 x 500 mm and a receiving telescope allow one to totally intercept the beam passed through the atmospheric layer under study and back.

Zuev, V. E.↗
NASA NTRS1987

Heat's on to develop high-temperature materials

An evaluation is made of the state-of-the-art and foreseeable development prospects in high temperature engineering materials applicable to advanced heat engines and other aerothermodynamically affected structures. Attention is given to monocrystal- and microcrystal-producing metal solidification processes, soft oxide and chemically stable fluoride high temperature solid lubricants, polyimide and other high temperature polymers for propulsion system applications, high strength/toughness ceramics for heat engine structural components, thermal barrier coatings, and metal-matrix composites employing refractory matrices as well as reinforcing fibers.

Gray, Hugh R.↗
NASA NTRS1987

Structure-property relationships in directionally solidified single crystal NiAl

The ordered intermetallic alloy NiAl is being considered as a potential high temperature structural material, but lack of ductility at ambient temperatures, especially in polycrystalline form, is presently a major obstacle in achieving this goal. Even general agreement of the intrinsic ductility that can be achieved in monocrystals is in dispute. In order to understand this problem, two directionally solidified ingots of NiAl which displayed known differences in ductility were characterized in sufficient detail to identify the corresponding microstructural differences. It was found that the type and size of casting defects, i.e., porosity, present in the material were the major factors in controlling ductility of NiAl single crystals and could explain the order of magnitude variance in fracture strains reported in the literature.

Noebe, R. D.↗
NASA NTRS1991

Cryogenic monocrystalline silicon Fabry-Perot cavity for the stabilization of laser frequency

A 1.6 kg silicon monocrystal was used to make a Fabry-Perot optical cavity operated at cryogenic temperatures. High-resolution thermal expansion measurements were made as the silicon cooled to 4.2 K, in order to characterize the cavity as a length reference standard. A helium-neon laser was then locked to a transmission resonance at liquid-helium temperatures, and the laser frequency tracked the cavity resonance with error fluctuations at the level of 10 Hz/sq rt Hz in the bandwidth dc to 1 Hz. Implications of the combined set of data, thermal expansion plus frequency-tracking fluctuations, for using such a system as a frequency standard are discussed.

Richard, J.-P.↗
NASA NTRS2012

Primary Dendrite Array Morphology: Observations from Ground-based and Space Station Processed Samples

Influence of natural convection on primary dendrite array morphology during directional solidification is being investigated under a collaborative European Space Agency-NASA joint research program, "Microstructure Formation in Castings of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MICAST)". Two Aluminum-7 wt pct Silicon alloy samples, MICAST6 and MICAST7, were directionally solidified in microgravity on the International Space Station. Terrestrially grown dendritic monocrystal cylindrical samples were remelted and directionally solidified at 18 K/cm (MICAST6) and 28 K/cm (MICAST7). Directional solidification involved a growth speed step increase (MICAST6-from 5 to 50 micron/s) and a speed decrease (MICAST7-from 20 to 10 micron/s). Distribution and morphology of primary dendrites is currently being characterized in these samples, and also in samples solidified on earth under nominally similar thermal gradients and growth speeds. Primary dendrite spacing and trunk diameter measurements from this investigation will be presented.

Tewari, Surendra↗
NASA NTRS2012

Primary Dendrite Array: Observations from Ground-Based and Space Station Processed Samples

Influence of natural convection on primary dendrite array morphology during directional solidification is being investigated under a collaborative European Space Agency-NASA joint research program, Microstructure Formation in Castings of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MICAST). Two Aluminum-7 wt pct Silicon alloy samples, MICAST6 and MICAST7, were directionally solidified in microgravity on the International Space Station. Terrestrially grown dendritic monocrystal cylindrical samples were remelted and directionally solidified at 18 K per centimeter (MICAST6) and 28 K per centimeter (MICAST7). Directional solidification involved a growth speed step increase (MICAST6-from 5 to 50 millimeters per second) and a speed decrease (MICAST7-from 20 to 10 millimeters per second). Distribution and morphology of primary dendrites is currently being characterized in these samples, and also in samples solidified on earth under nominally similar thermal gradients and growth speeds. Primary dendrite spacing and trunk diameter measurements from this investigation will be presented.

Tewari, Surendra N.↗
DOE OSTI2017

Spectra and Kinetics of YAG:0.5%Er{sup 3+} Radiation Under Pulsed Laser Thermal Excitation

The dependences of single-crystal YAG:0.5%Er{sup 3+} spectra in the range 200–1700 nm and the kinetics of the integrated emission on the excitation-energy density W of a single CO{sub 2}-laser pulse of ~100 ns FWHM duration at λ{sub ex} = 10.6 μm were investigated experimentally. The spectra changed qualitatively when W exceeded the generation threshold W{sub t} of laser plasma near the single-crystal surface. The YAG:0.5%Er{sup 3+} spectra at W < Wt were represented by peaks of selective emission (SE) of Er{sup 3+} multiplets on the continuous spectrum background. New emission peaks and additional background corresponding to emission spectra in a laser-induced air plasma with intensities much higher than the SE peaks appeared due to air ionization near the crystal surface at W > W{sub t}. Oscillograms of the integral emission in the range 600–1700 nm were characterized by a pulse-front duration of τ{sub f} = 1.0–1.6 μs and a decay time τ{sub d} ≈ 2.5 μs if W changed by one order of magnitude. The kinetics of the integrated emission intensity were explained by calculating the single-crystal temperature and the populations of Er{sup 3+} energy levels during conversion of thermal energy into SE during unsteady energy transfer by internal radiation and thermal conductivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

YAG:Er{sup 3+}, CaF{sub 2}:Er{sup 3+}, and Er{sub 2}O{sub 3} Emission Spectra Under Laser and Laser Thermal Excitation

Experimental luminescence and selective-emission (SE) spectra of YAG:Er{sup 3+} (10 at.%) and CaF{sub 2}:Er{sup 3+} (1 at.%) single crystals and Er{sub 2}O{sub 3} polycrystal under laser and laser thermal excitation of the Er3+-ion multiplets are compared. Luminescence spectra under resonant excitation are determined by multiplet population relaxation with the corresponding radiative and nonradiative probabilities. The form of the SE spectra is determined by the thermal population of the multiplets and the probabilities of only radiative transitions. The SE band at 800 nm ({sup 4}I{sub 9/2} → {sup 4}I{sub 15/2}) is an indicator of high-temperature thermal emission of Er{sup 3+} ions. The absence of this band in luminescence spectra is explained by the short lifetime of the τ({sup 4}I{sub 9/2}) level of 53 ns at T = 300 K.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1–1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the influence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm{sup –1} and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm{sup –1}. The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structure and Optical Properties Of LiNbO{sub 3}:В Crystals Grown from Charges of Different Origins

It was shown that, without entering the structure of the crystal, boron can change the structure of the melt and have a significant effect on the fine features of the structure and the physical characteristics of lithium niobate crystals. Crystals grown from a charge doped with boron by the direct solid-phase method have a stronger photorefractive effect and a smaller forbidden band width than crystals grown from the re-extract doped homogeneously with boron at the niobium pentoxide extraction stage.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis, Crystal Structure, Hirshfeld Surface Analysis, and Physicochemical Study of an Anhydrous Organic Acidic Cyclohexaphosphate

The new organic–inorganic hybrid [5-Cl-2-(CH{sub 3})C{sub 6}H{sub 3}NH{sub 3}]{sub 4}H{sub 2}P{sub 6}O{sub 18} has been synthesized by the slow evaporation method. X-ray diffraction on a single crystal shows that this acidic cyclohexaphosphate crystallized in the monoclinic space group C{sub 2/c} with a = 33.89(11) Å, b = 9.16(16) Å, c = 13.68(3) Å, β = 91.35(2)°, V = 4244.9(19) Å{sup 3} and Z = 4. {sup 31}P MAS-NMR and {sup 13}C CP/MAS-NMR results are in accordance with X-ray findings. Fluorescent study shows the blue photoluminescence. Furthermore, FT-IR analysis was studied and the complete vibrational assignments were done. Intermolecular interactions were analyzed using Hirshfeld surface analysis and the associated 2D fingerprint plots.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Boundary Current Response in Ba{sub 0.34}K{sub 0.64}Fe{sub 2}As{sub 2} Single Crystal Probed by Non-resonant Microwave Absorption

Non-resonant microwave absorption (NRMA) in superconducting materials has become a new experimental technique to probe and understand superconducting materials. For example, cuprate superconductors are well studied with this technique. At the same time, the technique is also evolving. This NRMA technique has been used to study magnetic shielding effects/boundary current in Ba{sub 0}.{sub 34}K{sub 0}.{sub 64}Fe{sub 2}As{sub 2} (BaK122) single crystals of iron pnictide superconducting sample measured at 9.4 GHz below T{sub c} (4.2–32 K). It has been observed that a small modulation field used in NRMA experiment yields the boundary current response. We have established that the boundary current response depends on both the modulation amplitude and the temperature. At high modulation field amplitudes and temperatures close to T{sub c}, the boundary current response gets suppressed and the flux-modulated response dominates. At low temperatures far away from T{sub c}, only the boundary current response dominates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Angular-Dependent Vortex Pinning Properties of YBa{sub 2}Cu{sub 3}O{sub 7−δ}/Y{sub 2}O{sub 3} Quasi-Multilayers

A series of quasi-multilayers of YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO)/Y{sub 2}O{sub 3} specifically 70 × (m YBCO/n Y{sub 2}O{sub 3}) were prepared on SrTiO{sub 3} single crystal using pulsed-laser deposition (PLD) with a controlled deposition pulses of m = 40 and n = 2, 5, and 10 for YBCO and Y{sub 2}O{sub 3}, respectively. The x-ray diffraction patterns indicate that all the present quasi-multilayers exhibit good c-axis orientation. The angular dependence of critical current density (J{sub c}) on applied magnetic field directions are systemically measured to study the anisotropic vortex pinning performances for those quasi-multilayers. It is revealed that compared with the pure YBCO films, the quasi-multilayers with n = 2, i.e., a proper constituent pulse of Y{sub 2}O{sub 3}, exhibits the enhanced vortex pinning abilities in all angles between c-axis orientation and the applied magnetic field direction. As well, such a quasi-multilayer film (n = 2) shows the higher lift factor J{sub c}(Θ)/ J{sub c}(90°) and much better vortex pinning properties at high fields and high temperatures, showing promising potential for coated conductor application.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Optimization of the Dy Content in Single Crystalline GdBCO Bulk Superconductors Fabricated in Air Via Top-Seeded Infiltration Growth Process

Single-crystalline bulk GdBa{sub 2}Cu{sub 3}O{sub 7−δ} (GdBCO) superconductors were fabricated with top-seeded infiltration-growth technique (TSIG) in air by adding the different amounts of Dy{sub 2}BaCuO{sub 5} (Dy-211) particles (5, 10, 15, 20, 25, 30, 35, and 40 wt%). All the samples show superconducting critical temperature at ∼93 K with sharp transition irrespective of the chemical composition. X-ray diffraction measurements confirmed that all the samples were single domain with high alignment. Microstructural studies through scanning electron microscopy showed that TSIG-processed GdBCO samples contained 211 phase particles of two different sizes, i.e., ∼2–4 and ∼10 μ m. The addition of Dy-211 phase particles led to a significant enhancement of critical current density (J{sub c}) at 77 K. GdBCO superconductor with the addition of 20 wt% of Dy-211 showed the highest J{sub c} of 45.5 kA/cm {sup 2} at 77 K and self field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Dependence of Catalytic Activity of Nanocrystalline Nickel Ferrite on Its Structural, Morphological, Optical, and Magnetic Properties in Aerobic Oxidation of Benzyl Alcohol

Nanocrystalline nickel ferrite spinel, NiFe{sub 2}O{sub 4}, with average crystallite size of 23.98 and 19.76 nm were successfully synthesized under sol–gel method (SGM) and microwave method (MM) conditions without using any surfactant or otherwise structure-directing (oxalic acid as the fuel) agents. Powder x-ray diffraction, high-resolution scanning electron microscopies indicate that single-crystalline nanoparticles are well-dispersed in the nickel ferrite. The elemental investigation of nickel ferrite was attained from energy-dispersive x-ray (EDX) analysis. Their optical properties (diffuse reflectance spectroscopy and photoluminescence) were described in depth in relative with their structural characteristics and the functionalization performance. After the magnetic measurements, samples showed a ferromagnetic behavior and the magnetization (Ms) value of NiFe{sub 2}O{sub 4}-MM is higher, i.e., 59.33 emu/g than NiFe{sub 2}O{sub 4}-SGM (50.12 emu/g). The magnetic properties could be further changed by controlling the shape, size, and crystallinity of the nanocrystals. Determination of concentration NiFe{sub 2}O{sub 4} ions’ average number of atoms per nanoparticle was calculated by the new method as follows. Consequently, the designated procedure improves catalytic activity of nickel ferrite powders in aerobic oxidation of benzyl alcohol and catalytic reactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗