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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Noncollinear ferromagnetic easy axes in Py/Ru/FeCo/IrMn spin valves induced by oblique deposition

We present an investigation on the magnetic properties of Py/Ru/FeCo/IrMn spin valves grown by dc magnetron sputtering. The sample fabrication setup has two important features, (i) the five magnetron sputtering sources are placed in a cluster flange 72° from each other, and (ii) each source is tilted with respect to the sample normal. In-plane angular dependence of the ferromagnetic resonance (FMR) was used to obtain the relevant magnetic anisotropies, such as uniaxial and exchange bias fields. The oblique deposition geometry employed has induced non-collinear easy axes of the two ferromagnetic (FM) layers, with high uniaxial field strengths. The symmetry shift of the angular dependence of the FMR resonances of the two FM layers gives us directly the angle between the easy axes of FM{sub 1} (Py) and FM{sub 2} (FeCo), which turned out to be the angle between two adjacent sputtering sources. The observations of the present study suggest that, by combining oblique deposition and appropriate angles of incidence of the deposition flux, the uniaxial (and unidirectional) axes of individual FM layers can be precisely engineered in spin valve fabrication.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Dual function armchair graphene nanoribbon-based spin-photodetector: Optical spin-valve and light helicity detector

We show an armchair graphene nanoribbon channel connected between asymmetric ferromagnetic source-drain structure—i.e., p-type Co/Au/graphene source and n-type Co/Cu/graphene drain—can operate as dual function spin-photodetector, under zero external biases at room temperature. It can function as an optical spin-valve with magnetoresistance of greater than 60% and responsivity as high as 25.12 A/mW, when irradiated by an un-polarized light of energy ∼3.03 eV. Under a circularly polarized illumination, this optical spin-valve can also operate as a light helicity detector. The calculated magnetoresistances for right and left circularly polarized lights are both greater than 60%.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Spin valve effect of the interfacial spin accumulation in yttrium iron garnet/platinum bilayers

We report the spin valve effect in yttrium iron garnet/platinum (YIG/Pt) bilayers. The spin Hall effect (SHE) generates spin accumulation at the YIG/Pt interface and can be opened/closed by magnetization switching in the electrical insulator YIG. The interfacial spin accumulation was measured in both YIG/Pt and YIG/Cu/Pt structures using a planar Hall configuration. The spin valve effect remained, even after a 2 nm thick Cu layer was inserted between the YIG and Pt layers, which aimed to exclude the induced magnetization at the YIG/Pt interface. The transverse Hall voltage and switching field were dependent on the applied charge current density. The origin of this behavior can be explained by the SHE induced torque exerted on the domain wall, caused by the transfer of the spin angular momentum from the spin-polarized current to the YIG magnetic moment.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Magneto-Seebeck effect in spin-valve with in-plane thermal gradient

We present measurements of magneto-Seebeck effect on a spin valve with in-plane thermal gradient. We measured open circuit voltage and short circuit current by applying a temperature gradient across a spin valve stack, where one of the ferromagnetic layers is pinned. We found a clear hysteresis in these two quantities as a function of magnetic field. From these measurements, the magneto-Seebeck effect was found to be same as magneto-resistance effect.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Double-pinned magnetic tunnel junction sensors with spin-valve-like sensing layers

MgO magnetic tunnel junction (MTJ) sensors with spin-valve-like sensing layers of Ir{sub 22}Mn{sub 78} (6)/Ni{sub 80}Fe{sub 20} (t{sub NiFe} = 20–70)/Ru (0.9)/Co{sub 40}Fe{sub 40}B{sub 20} (3) (unit: nm) have been fabricated. A linear field dependence of magnetoresistance for these MTJ sensors was obtained by carrying out a two-step field annealing process. The sensitivity and linear field range can be tuned by varying the thickness of NiFe layer and annealing temperature, and a high sensitivity of 37%/mT has been achieved in the MTJ sensors with 70 nm NiFe at the optimum annealing temperature of 230 °C. Combining the spin-valve-like sensing structure and a soft magnetic NiFe layer, MTJ sensors with relatively wide field sensing range have been achieved and could be promising for showing high sensitivity magnetic field sensing applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Magnetoresistance effect in Fe{sub 20}Ni{sub 80}/graphene/Fe{sub 20}Ni{sub 80} vertical spin valves

Vertical spin valve devices with junctions of single- and bi-layer graphene interlayers sandwiched with Fe{sub 20}Ni{sub 80} (Permalloy) electrodes were fabricated by exploiting the direct growth of graphene on the Permalloy. The linear current-voltage characteristics indicated that ohmic contacts were realized at the interfaces. The systematic characterization revealed the significant modification of the electronic state of the interfacial graphene layer on the Permalloy surface, which indicates the strong interactions at the interface. The ohmic transport was attributable to the strong interface-interaction. The vertical resistivity of the graphene interlayer and the spin asymmetry coefficient at the graphene/Permalloy interface were obtained to be 0.13 Ω cm and 0.06, respectively. It was found that the strong interface interaction modifies the electronic structure and metallic properties in the vertical spin valve devices with bi-layer graphene as well as single-layer graphene.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Transport in ferromagnet/superconductor spin valves

We consider charge transport properties in realistic, fabricable, ferromagnet/superconductor spin valves having a layered structure F 1 /N/F 2 /S, where F 1 and F 2 denote the ferromagnets, S the superconductor, and N the normal-metal spacer usually inserted in actual devices. Our calculation is fully self-consistent, as required to ensure that conservation laws are satisfied. We include the effects of scattering at all the interfaces. We obtain results for the device conductance G, as a function of bias voltage, for all values of the angle Φ between the magnetizations of the F 1 and F 2 layers and a range of realistic values for the material and geometrical parameters in the sample. We discuss, in the context of our results for G, the relative influence of all parameters on the spin valve properties. We also study the spin current and the corresponding spin-transfer torque in F 1 /F 2 /S structures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Proximity Effect in a Superconducting Triplet Spin Valve S1/F1/S2/F2

Сritical temperatures of multilayer structures of the superconductor/ferromagnet/ferromagnet (S/F/F) type are obtained using the matrix method for solving the linearized Usadel equations. The influence of an additional superconductor layer on the effects of a three-layer spin valve is considered. The possibility of increasing the efficiency of the spin valve modes with an additional superconducting layer S in the place of the layer N is discussed in comparison with an additional normal layer in the S/F/N/F structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Additively Manufactured, Net Shape Powder Metallurgy Cans for Valves Used in Energy Production

Additive manufacturing (AM) has the potential to enable a paradigm shift in fabricating complex net shape components with yields over 90%, significantly increasing productivity, decreasing energy consumption during manufacturing and improving downstream energy efficiency. ORNL has developed a technology for producing large-scale additively manufactured polymer matrix composite components at deposition rates on the order of 100 lbs. per hour. This project utilized tools, dies and molds made from this technology to enable the net shape forming of cans for the powder metallurgy (PM) manufacturing of valves used in energy production plants. This approach has the potential to develop affordable valves with superior performance to castings. It will also lead to increased strength values, decreased wall thickness size, and the potential for higher yields (less machining). This project is critical for evaluating new methodologies for the fabrication of additively manufactured tooling, molds and dies that could be used across multiple industries. In the first phase of this project, a new methodology of creating a Powder Metallurgy and Hot Isostatic Pressing (PM-HIP) container by hydroforming sheet metal over additively manufactured (AM) dies was evaluated. The goal in this stage of development was to evaluate some of the new polymer matrix composite materials designed for deposition on large scale additive manufacturing systems as candidates for hydroforming steel and aluminum sheet to make thin gauge net shape components. In order to meet this objective, most research was performed on subscale tools in order to evaluate the processing pressures, material options, and gauge thicknesses most relevant to this approach. In addition, full scale AM tools (30% over final component geometry) were produced to demonstrate scalability, but were not used in testing. The first phase of this project has proven this concept has merit, but future studies are required to address minor tool failures that occurred in phase one due to geometry, cost of the process over other techniques, and demonstration of a full-scale tool that could then be used in (HIP). Lastly, this project provides the PM community a new approach in using hydroforming for the manufacturing of cans, a process that was not highly utilized for this purpose previously.

42 ENGINEERING↗
DOE OSTI2025

Development of Engine Valve Materials for Next Generation Higher Efficiency Engines

The growing demand to increase the performance and efficiency of light-, medium-, and heavy-duty engines continues to drive increases in combustion intensities and cylinder pressures, which result in higher exhaust gas temperatures. Thus, there is a critical need for new materials that can meet the performance and cost targets for components such as exhaust valves which are exposed to these higher exhaust gas temperatures. Oak Ridge National Laboratory (ORNL) has developed several lower-cost, high-strength alloys that have the potential to be adopted into intake and/or exhaust valves in the next generation, high-efficiency engines and other high temperature applications. These alloys are covered by two issued patents.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

The Effect of Spark-Plug Heat Dispersal Range and Exhaust Valve Opening Timing on Cold-Start Emissions and Cycle-to-Cycle Variability

The partnership for advancing combustion engines (PACE) is a US Department of Energy consortium involving multiple national laboratories and includes a goal of addressing key efficiency and emission barriers in light-duty engines fueled with a market-representative E10 gasoline. A major pillar of the initiative is the generation of detailed experimental data and modeling capabilities to understand and predict cold-start behavior. Cold-start, as defined by the time between first engine crank and three-way catalyst light-off, is responsible for a large percentage of NOx, unburned hydrocarbon and particulate matter emissions in light-duty engines. Minimizing emissions during cold-start is a trade-off between achieving faster light-off of the three-way catalyst and engine out emissions during that period. In this study, gaseous and soot emissions were measured at a distance representative of the three-way catalyst position downstream of the engine at a 2 bar net indicated mean effective pressure (NIMEP) steady-state operating condition representative of cold-start. The test matrix included sweeps of ignition timing 15 degrees-before to 10 degrees-after top dead center firing (TDCf) across three different spark-plug heat dispersal ranges (HR). Additionally, the effect of varying exhaust valve opening (EVO) timing on combustion stability and emissions was also studied. Results show that the spark plug HR affects the coefficient of variation (COV) of NIMEP under all cold-start conditions, while the impact on emissions was found to be minimal. At very retarded spark timings, colder spark plugs required higher air and fuel flow to maintain the desired 2bar NIMEP load, but the fraction of fuel energy going into the exhaust was found to be similar for all spark plugs. Finally, retarding exhaust valve timings showed a simultaneous reduction in emissions while increasing the fraction of fuel energy being fed into the exhaust. However, engine COV was also observed to increase with retarded exhaust timings.

42 ENGINEERING↗
NASA NTRS1964

Two-part valve acts as quick coupling

A two-part valve simplifies the problem of filling large tanks from smaller ones. One part acts as a check valve and remains integral to the recipient system, while the other part is integral to the donor system.

Source record↗
NASA NTRS1965

Valve designed with elastic seat

Absolute valve closure is accomplished by a machined valve with an axially annular channel which changes the outlet passage into a thin tubular elastic seat member with a retainer backup ring. The elasticity of the seat provides tight conformity to ball irregularity.

Mac Glashan, W. F., Jr.↗
NASA NTRS1965

Flow control valve is independent of pressure drop

Remote control of fluid flow in a low-power system is established by a flow control valve with a flapper and nozzle flow control. Constant rates are maintained despite fluctuating pressure across the valve.

Source record↗
NASA NTRS1966

Ring valve responds to differential pressure changes

Pressure valve has a moving annular ring seal that automatically reacts to differential pressure changes across the seat. This valve has good potential for the petroleum and chemical industries.

Source record↗
NASA NTRS1966

Cryogenic trap valve has no moving parts

Aluminum-body trap valve with an invar stem keeps cryogenic materials in the liquid state while entering the final component of a system. The valve has no moving parts and is self-actuated and self-monitoring.

Branum, L. W.↗