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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Elastomeric load sharing device

An elastomeric load sharing device, interposed in combination between a driven gear and a central drive shaft to facilitate balanced torque distribution in split power transmission systems, includes a cylindrical elastomeric bearing and a plurality of elastomeric bearing pads. The elastomeric bearing and bearing pads comprise one or more layers, each layer including an elastomer having a metal backing strip secured thereto. The elastomeric bearing is configured to have a high radial stiffness and a low torsional stiffness and is operative to radially center the driven gear and to minimize torque transfer through the elastomeric bearing. The bearing pads are configured to have a low radial and torsional stiffness and a high axial stiffness and are operative to compressively transmit torque from the driven gear to the drive shaft. The elastomeric load sharing device has spring rates that compensate for mechanical deviations in the gear train assembly to provide balanced torque distribution between complementary load paths of split power transmission systems.

Isabelle, Charles J.↗
NASA NTRS1987

An analytical study of the effects of transverse shear deformation and anisotropy on buckling loads of laminated cylinders

Buckling loads of thick-walled orthotropic and anisotropic simply supported circular cylinders are predicted using a higher-order transverse-shear deformation theory. A comparison of buckling loads predicted by the conventional first-order transverse-shear deformation theory and the higher-order theory show that the additional allowance for transverse shear deformation has a negligible effect on the predicted buckling loads of medium-thick metallic isotropic cylinders. However, the higher-order theory predicts buckling loads which are significantly lower than those predicted by the first-order transverse-shear deformation theory for certain short, thick-walled cylinders which have low through-the-thickness shear moduli. A parametric study of the effects of ply orientation on the buckling load of axially compressed cylinders indicates that laminates containing 45 degree plies are most sensitive to transverse-shear deformation effects. Interaction curves for buckling loads of cylinders subjected to axial compressive and external pressure loadings indicate that buckling loads due to external pressure loadings are as sensitive to transverse-shear deformation effects as buckling loads due to axial compressive loadings. The effects of anisotropy are important over a much wider range of cylinder geometries than the effects of transverse shear deformation.

Jegley, Dawn C.↗
DOE OSTI2023

Role of Transition Metals in Metal–Organic Frameworks as Nanoporous Ion Emitters for Thermal Ionization Mass Spectrometry

Thermal ionization mass spectroscopy (TIMS) is a powerful analytical technique that allows for precise determination of isotopic ratios. Analysis on low abundance samples, however, can be limited by the ionization efficiency. Following an investigation into a new type of metal-organic hybrid material devised to promote the emission of analyte ions (nano-PIES) and reduce traditional sample loading problems, this work probes the impact that changing the metal in the material has on the ionization of Uranium-238. Being derived from metal-organic frameworks (MOFs), nano-PIEs inherit the tunability of the parent MOFs; the MOF-74 series has been well studied for probing the impact various framework metals (i.e., Mg, Mn, Co, Ni, Cu, Zn, and Cd) have on material properties, and thus, a series of nano-PIEs with different metals were derived from an isoreticular MOF-74 series. In conclusion, trends in ionization efficiency were studied as a function of ionization potential, volatility, and work function of the framework metals as well as the mechanism of ionization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1998

A New Approach to Overcoming Spatial Aliasing in Structural Damage Detection

Aircraft, reusable launch vehicles,unmanned aircraft, and other advanced structures are being built using lightweight composite materials/metals with design safety factors as low as 1.25. These advanced structures operate in uncertain and severe environments and are susceptible to damage such as delamination, fiber/matrix damage, hydrothermal strain in composite materials, and fatigue and cracking in metals. To ensure human safety and load-bearing integrity these structures must be inspected to detect and locate often invisible damage and faults before they become catastrophic. Conventional methods of non-destructive evaluation sometimes miss significant damage and are time consuming and expensive to perform. In contrast, vibrometry or vibration signature techniques are a global method of structural integrity monitoring that potentially can efficiently detect damage on large structures, including damage that is away from sensor locations, and in the interior of structures. However, a barrier problem in damage detection using vibration measurements is the need to measure the vibration response at a large number of points on the structure. Typically, model reduction or expansion procedures such as Guyan reduction or dynamic expansion are attempted to overcome the problem of insufficient measurements or spatial aliasing. These approaches depend on using information from the healthy model, and thus put error into the reduction used to represent the damaged structure. In this paper, a Frequency Response Function technique is used to detect damage to a fixed-free beam. The technique uses measured frequency response functions from the healthy structure as reference data, and then monitors vibration measurements during the life of the structure to detect damage. In an analytical simulation using a finite-element model of a beam, damage was located using only sparse measurements because the technique uses both rotation and translation measurements from the damaged structure.

Schulz, Mark J.↗
NASA NTRS1972

Graphite fiber polyimide composites for spherical bearings to 340 C (650 F)

Journal bearings with self-alining spherical elements of graphite-fiber-reinforced-polyimide composites were tested from 24 to 340 C (75 to 650 F) at unit loads up to 3.5 times 10 to the 7th power N/sq m (5000 psi). The journal oscillated in the cylindrical bore of the composite element + or - 15 deg at 1 hertz. Outer races and journals were metal hardened of Rockwell C-32 and finished to 10 to the minus 7th power m. A 45 wt. percent graphite-fiber composite gave low friction (0.08 to 0.13), low wear, and almost no plastic deformation under any of the test conditions. Composites with 15 and 25 wt. percent graphite fiber failed by plastic deformation at 315 C (600 F) and 3.5 times 10 to the 7th power N/sq m (5000 psi). A composite with 60 wt. percent graphite fiber failed by brittle fracture under the same conditions, but had very low friction coefficients (0.05 to 0.10) and may be a good bearing material at lighter loads.

Sliney, H. E.↗
DOE OSTI2025

DEVELOPMENT OF INEXPENSIVE HIGH TEMPERATURE NITI-BASED SHAPE MEMORY ALLOYS FOR POWDER BED ADDITIVE MANUFACTURING

NiTi and NiTi-based Shape Memory Alloys (SMA) exhibit a reversible solid-state phase transformation from martensite to austenite driven by thermal energy. High temperature (Mf>100°C) SMAs are martensite at room temperature and can be fabricated into solid-state actuators that return to a pre-programmed shape against a designed load after heating to transformation threshold. Reactive as-fabricated additively manufactured parts (4-D printing) is the current state of the art in manufacturing of SMAs but requires compositions compliant to rapid solidification. Existing actuator designs are developed from commercially available, highly investigated material compositions. However, existing high temperature high performance (high actuation strain, low thermal hysteresis) shape memory alloys contain significant (>10% at.) portions of high-cost Platinum Group Metals (PGMs). It is of significant scientific interest to investigate material compositions that are peer performing or superior to PGMs whose constituent elements represent a significant cost savings. Shape memory alloy properties vary significantly with small (0.1% at.) compositional changes making robust investigative sample sets very large. Computational material design can be deployed to shrink the compositional space of possible alloy combinations and reduce the experimental load in material discovery. Investigating shape memory effect (SME) and validating process additive process parameters for a single novel composition is cost intensive in both time and consumed materials. Additionally, sub-optimal processing, oxygen, or solidification rate sensitivity could render additively manufacturing specimens without micro, macro cracks, or significant chemical variance impossible. Unfortunately, such failure susceptibility cannot be simulated. Therefore, a research pathway to validate novel shape memory alloy compositions for powder bed fusion additive manufacturing without the need for powdered feedstock is also proposed. This research investigates novel high temperature shape memory alloys for actuators without platinum group alloying elements to discover one that could be commercially viable as an additive manufacturing feedstock.

Sundermann, Tayler↗
NASA NTRS2001

Superalloy Foams for Aeroshell Applications

Current thermal protection systems for reentry from space, such as that employed on the space shuttle, rely on ceramic tiles with ultra-low conductivity. These materials provide excellent thermal protection but are extremely fragile, easily degraded by environmental attack, and carry no structural loads. Future thermal protection systems being proposed in NASAs MITAS Program will attempt to combine thermal protection with improved durability and structural capability without significant increases in vehicle weight. This may be accomplished by combining several materials in a layered structure to obtain the desired function for aeroshell applications. One class of materials being considered for inclusion in this concept are high temperature metal foam. The objective of this paper was to fabricate low density, superalloy foams and conduct limited testing to evaluate their thermal and structural capabilities. Superalloys were chosen for evaluation as they possesses good strength and excellent environmental endurance over a wide range of temperatures. Utilizing superalloys as low density foams, with porosity contents greater than 90%, minimizes weight and thermal conductivity.

Gayda, John↗
DOE OSTI2020

A chemically stabilized sulfur cathode for lean electrolyte lithium sulfur batteries

Lithium sulfur batteries (LSBs) are promising next-generation rechargeable batteries due to the high gravimetric energy, low cost, abundance, nontoxicity, and high sustainability of sulfur. However, the dissolution of high-order polysulfide in electrolytes and low Coulombic efficiency of Li anode require excess electrolytes and Li metal, which significantly reduce the energy density of LSBs. Quasi-solid-state LSBs, where sulfur is encapsulated in the micropores of carbon matrix and sealed by solid electrolyte interphase, can operate under lean electrolyte conditions, but a low sulfur loading in carbon matrix (<40 wt %) and low sulfur unitization (<70%) still limit the energy density in a cell level. Here, we significantly increase the sulfur loading in carbon to 60 wt % and sulfur utilization to ∼87% by dispersing sulfur in an oxygen-rich dense carbon host at a molecular level through strong chemical interactions of C–S and O–S. In an all-fluorinated organic lean electrolyte, the C/S cathode experiences a solid-state lithiation/delithiation reaction after the formation of solid electrolyte interphase in the first deep lithiation, completely avoiding the shuttle reaction. The chemically stabilized C/S composite retains a high reversible capacity of 541 mAh⋅g −1 (based on the total weight of the C/S composite) for 200 cycles under lean electrolyte conditions, corresponding to a high energy density of 974 Wh⋅kg −1 . The superior electrochemical performance of the chemical bonding-stabilized C/S composite renders it a promising cathode material for high-energy and long-cycle-life LSBs.

25 ENERGY STORAGE↗
NASA NTRS1991

Ductility of a continuous fiber reinforced aluminum matrix composite

The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers have been investigated. The composite is subjected to both mechanical and cyclic thermal loading. The ductility can vary by an order of magnitude according to the operating conditions. For high mechanical and low thermal loading the ductility is small, for low mechanical and high thermal loading the ductility is an order of magnitude higher. Experiments on a beam in bending confirm that the ductility is strongly dependent on the loading conditions. The observations suggest a means of utilizing the inherent ductility of the matrix.

Jansson, S.↗
NASA NTRS1997

The Effect of Gravity on the Combustion of Bulk Metals

In recent years, metal combustion studies at the University of Colorado have focused on the effects of gravity (g) on the ignition and burning behavior of bulk metals. The impetus behind this effort is the understanding of the ignition conditions and flammability properties of structural metals found in oxygen (O2) systems for space applications. Since spacecraft are subjected to higher-than-1g loads during launch and reentry and to a zero-gravity environment while in orbit, the study of ignition and combustion of bulk metals at different gravitational accelerations is of great practical concern. From the scientific standpoint, studies conducted under low gravity conditions provide simplified boundary conditions, since buoyancy is removed, and make possible the identification of fundamental ignition and combustion mechanisms. This investigation is intended to provide experimental verification of the influence of natural convection on the burning behavior of metals. In addition, the study offers the first findings of the influence of gravity on ignition of bulk metals and on the combustion mechanism and structure of metal-oxygen, vapor-phase diffusion flames in a buoyancy-free environment. Titanium (Ti) and magnesium (Mg) metals were chosen because of their importance as elements of structural materials and their simple chemical composition-pure metals instead of multicomponent alloys to simplify chemical and spectroscopic analyses. In addition, these elements present the two different combustion modes observed in metals: heterogeneous or surface burning (for Ti) and homogeneous or gas-phase reaction (for Mg). Finally, Mg, Ti, and their oxides exhibit a wide range of thermophysical and chemical properties. Metal surface temperature profiles, critical and ignition temperatures, propagation rates, burning times, and spectroscopic measurements are obtained under normal and reduced gravity. Visual evidence of all phenomena is provided by high-speed photography.

Branch, Melvyn C.↗
DOE OSTI2023

Li 3– x Zr x (Ho/Lu) 1– x Cl 6 Solid Electrolytes Enable Ultrahigh-Loading Solid-State Batteries with a Prelithiated Si Anode

We report two new families of lithium metal chloride solid electrolytes Li 3–x Zr x (M) 1–x Cl 6 (0 ≤ x ≤ 0.8; M = Ho or Lu) with ionic conductivities of up to 1.8 mS cm –1 and a low activation energy of 0.34 eV. Structural elucidation via high-resolution neutron diffraction determines the Li ion distribution in trigonal Li 3 HoCl 6 , orthorhombic-I Li 3 LuCl 6 , and orthorhombic-II Li 2.4 Zr 0.6 (Ho/Lu) 0.4 Cl 6 . The last compound exhibits well-connected Li-ion pathways and abundant Li-ion carriers/vacancies to promote diffusion. All-solid-state batteries with Li 2.6 Zr 0.4 (Ho/Lu) 0.6 Cl 6 solid electrolytes and NCM85 cathodes exhibit stable cycling up to 4.6 V vs Li + /Li, which is even preserved up to 4.8 V. Stable cathode interphases are formed for both electrolytes upon cycling to 4.3, 4.6, and 4.8 V cutoff potentials, as identified by a ToF-SIMS analysis. Solid-state cells with a prelithiated Li 0.7 Si anode exhibit a significantly increased initial coulombic efficiency of 94.5% compared to Si and a high areal capacity of up to 16.3 mAh·cm –2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Impact of Stabilizing Cations on Lithium Intercalation in Tunneled Manganese Oxide Cathodes

Stabilizing cations such as K + , Ba 2+ , and Ag + are known to provide charge neutrality and enhance structural stability in low-cost tunneled manganese dioxide (MnO 2 ) cathodes for Li ion batteries. However, a fundamental understanding of the role of these cations in the electrochemical performance of tunneled MnO 2 cathodes remains unclear, especially at low stabilizing cation concentrations. Here, we employ density functional theory (DFT + U) calculations to reveal the impact of stabilizing potassium cation (K + ) concentration on the structural stability, electronic properties, and kinetics of lithium transport in 2 x 2 tunneled manganese oxide (α-K y Mn 8 O 16 , at y = 0, 1, and 2) battery cathodes during lithium intercalation. Specifically, we provide insights into the effect of K + ions on several critical factors governing the electrochemical storage performance of tunneled MnO2 cathodes, including (a) energetically favorable Li+ host sites, (ii) Li + and electron transport capabilities, (iii) optimal intercalation pathways, crystal distortion, microstructural stability, and tunneled-to-layer phase transformation as a function of lithium content, and (iv) cell output voltage profile. Interestingly, we find that low K + concentrations (y ≤ 1) yield partially cation-deficient tunnels in the MnO 2 cathode. Such unique tunnel structures in the cathode enable (a) low kinetic barriers for Li transport, (b) excellent thermodynamic stability of the tunneled structure even at a high Li + loading (up to ~ 0.625 Li/Mn), and (c) good electronic conductivity facilitated by Jahn-Teller distortions; all of which are critical for achieving high capacity batteries with enhanced rate capability. Additionally, these results provide perspectives to design low-cost transition metal oxide cathodes for high-performance Li-ion batteries with excellent cycle life.

25 ENERGY STORAGE↗
NASA NTRS1972

Evaluation of boron-epoxy-reinforced titanium tubular truss for application to a space shuttle booster thrust structure

Results of a study to demonstrate the applicability of boron-epoxy-composite-reinforced titanium tubular members to a space shuttle booster thrust structure are presented and discussed. The experimental results include local buckling of all-composite and composite-reinforced-metal cylinders with low values of diameter-thickness ratio, static tests on composite-to-metal bonded step joints, and a test to failure of a boron-epoxy-reinforced titanium demonstration truss. The demonstration truss failed at 118 percent of design ultimate load. Test results and analysis for all specimens and the truss are compared. Comparing an all-titanium design and a boron-epoxy-reinforced-titanium (75 percent B-E and 25 percent Ti) design for application to the space shuttle booster thrust structure indicates that the latter would weigh approximately 24 percent less. Experimental data on the local buckling strength of cylinders with a diameter-thickness ratio of approximately 50 are needed to insure that undue conservatism is not used in future designs.

Corvelli, N.↗
DOE OSTI2021

Zn uptake by illite and argillaceous rocks

The uptake of Zn by Illite du Puy (IdP) and two argillaceous rocks, Opalinus Clay (OPA) and Boda Claystone (BODA) was investigated. The uptake of Zn by illite was studied in 0.1 M NaCl at near-neutral pH and Zn loadings varying from 2.1 to 42 mmol/kg. The Zn uptake by the two argillaceous rock systems was carried out in 0.1 M NaCl at pH 7.2 and in their respective porewaters at pH 8.0 to evaluate the influence of porewater composition. The Zn loadings varied from 1.8 to 86 mmol/kg and 1.7 to 60 mmol/kg for OPA and BODA, respectively. The simplified “bottom-up approach” to predict the uptake of Zn to natural rocks with different clay mineral contents and porewater compositions was tested. This approach was found to be applicable in the argillaceous rock systems at low Zn equilibrium ([Zn] eql ) concentrations below 10 -7 M. However, at [Zn]eql above 10 -7 M, the model calculations clearly underpredicted the sorption data. The extended X-ray absorption fine structure (EXAFS) results support findings based on wet chemistry calculations using the 2 site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model. In the IdP system with prolonged reaction times of up to two years, formation of Zn precipitates was not observed. This indicates that the Zn surface complexes are stable over a time period of two years, and dissolution and recrystallization processes might not play a significant role in the Zn-IdP uptake process. In addition, the EXAFS results on illite corroborate previous findings on the existence of weak and strong sites types in dioctahedral clay minerals, as assumed in the 2SPNE SC/CE model. In the OPA and BODA systems, precipitation processes could start to begin at metal loadings of 16 mmol/kg and 24 mmol/kg, respectively. The differences between argillaceous rock samples prepared in NaCl and porewater are modest indicating that in the case of Zn the clay minerals play a predominant role in the uptake process, and that the effects originating from the porewater are minor. Furthermore, despite the differences in mineralogy, both argillaceous rocks show the same uptake behaviour, indicating that the clay minerals are predominantly responsible for the sorption at low and the precipitation processes at higher Zn concentrations. The study demonstrates how results on “pure” systems such as IdP can be transferred to predict the uptake by argillaceous rocks at low sorbate concentrations.

58 GEOSCIENCES↗
NASA NTRS2005

Improved Anode for a Direct Methanol Fuel Cell

A modified chemical composition has been devised to improve the performance of the anode of a direct methanol fuel cell. The main feature of the modified composition is the incorporation of hydrous ruthenium oxide into the anode structure. This modification can reduce the internal electrical resistance of the cell and increase the degree of utilization of the anode catalyst. As a result, a higher anode current density can be sustained with a smaller amount of anode catalyst. These improvements can translate into a smaller fuel-cell system and higher efficiency of conversion. Some background information is helpful for understanding the benefit afforded by the addition of hydrous ruthenium oxide. The anode of a direct methanol fuel cell sustains the electro-oxidation of methanol to carbon dioxide in the reaction CH3OH + H2O--->CO2 + 6H(+) + 6e(-). An electrocatalyst is needed to enable this reaction to occur. The catalyst that offers the highest activity is an alloy of approximately equal numbers of atoms of the noble metals platinum and ruthenium. The anode is made of a composite material that includes high-surface-area Pt/Ru alloy particles and a proton-conducting ionomeric material. This composite is usually deposited onto a polymer-electrolyte (proton-conducting) membrane and onto an anode gas-diffusion/current-collector sheet that is subsequently bonded to the proton-conducting membrane by hot pressing. Heretofore, the areal density of noble-metal catalyst typically needed for high performance has been about 8 mg/cm2. However, not all of the catalyst has been utilized in the catalyzed electro-oxidation reaction. Increasing the degree of utilization of the catalyst would make it possible to improve the performance of the cell for a given catalyst loading and/or reduce the catalyst loading (thereby reducing the cost of the cell). The use of carbon and possibly other electronic conductors in the catalyst layer has been proposed for increasing the utilization of the catalyst by increasing electrical connectivity between catalyst particles. However, the relatively low density of carbon results in thick catalyst layers that impede the mass transport of methanol to the catalytic sites. Also, the electrical conductivity of carbon is less than 1/300th of typical metals. Furthermore, the polymer-electrolyte membrane material is acidic and most metals are not chemically stable in contact with it. Finally, a material that conducts electrons (but not protons) does not contribute to the needed transport of protons produced in the electro-oxidation reaction.

Valdez, Thomas↗
NASA NTRS1973

Filament-wound composite vessels material technology

Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

Lark, R. F.↗
NASA NTRS2007

Composite Pulse Tube

A modification of the design of the pulse tube in a pulse-tube cryocooler reduces axial thermal conductance while preserving radial thermal conductance. It is desirable to minimize axial thermal conductance in the pulse-tube wall to minimize leakage of heat between the warm and cold ends of the pulse tube. At the same time, it is desirable to maximize radial thermal conductance at the cold end of the pulse tube to ensure adequate thermal contact between (1) a heat exchanger in the form of a stack of copper screens inside the pulse tube at the cold end and (2) the remainder of the cold tip, which is the object to which the heat load is applied and from which heat must be removed. The modified design yields a low-heat-leak pulse tube that can be easily integrated with a cold tip. A typical pulse tube of prior design is either a thin-walled metal tube or a metal tube with a nonmetallic lining. It is desirable that the outer surface of a pulse tube be cylindrical (in contradistinction to tapered) to simplify the design of a regenerator that is also part of the cryocooler. Under some conditions, it is desirable to taper the inner surface of the pulse tube to reduce acoustic streaming. The combination of a cylindrical outer surface and a tapered inner surface can lead to unacceptably large axial conduction if the pulse tube is made entirely of metal. Making the pulse-tube wall of a nonmetallic, lowthermal- conductivity material would not solve the problem because the wall would not afford the needed thermal contact for the stack of screens in the cold end. The modified design calls for fabricating the pulse tube in two parts: a longer, nonmetallic part that is tapered on the inside and cylindrical on the outside and a shorter, metallic part that is cylindrical on both the inside and the outside. The nonmetallic part can be made from G-10 fiberglass-reinforced epoxy or other low-thermal-conductivity, cryogenically compatible material. The metallic part must have high thermal conductivity in the cryogenic temperature range and would typically be made of pure copper to satisfy this requirement. The metallic part is bonded to the nonmetallic part with epoxy. Copper screens are inserted in the metallic part to form the cold-end heat exchanger, then the assembled pulse tube is inserted in the cold tip.

Martin, Jerry L.↗