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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Treatment of Visceral Aneurysm Using Multilayer Stent: Two-Year Follow-Up Results in Five Consecutive Patients

Purpose: The present study was performed to analyze the midterm results (five consecutive patients, 2-year follow-up) of the endovascular management of visceral artery aneurysms using the Cardiatis Multilayer Flow Modulator (CMFM) (Cardiatis, Isnes, Belgium), a self-expandable stent. Materials and Methods: From August 2009 to January 2011, we implanted five CMFMs in five patients (all men; mean age 73 years) to treat two common hepatic artery aneurysms, one celiac trunk aneurysm, one splenic artery aneurysm, and one superior mesenteric artery aneurysm (diameter 25-81 mm). The primary end point was technical success. The secondary end point was stent patency, absence of aneurysm rupture or reperfusion, and shrinking of the sac at 6-, 12-, and 24-month follow-up using computed tomography angiography. Follow-up ranged from 24 to 48 months (mean 31.2). Results: Technical success was achieved in all patients. Complete exclusion of the aneurysm with sac shrinking was achieved in two patients. Two stents became occluded at 6- and 24-month follow-up, respectively; both patients were asymptomatic and were not retreated. One patient developed sac reperfusion due to incomplete aneurysm exclusion. Conclusion: Long-term results in a wider population are needed to validate the effectiveness of the CMFM.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

A General Strategy to Achieve Colossal Permittivity and Low Dielectric Loss Through Constructing Insulator/Semiconductor/Insulator Multilayer Structures

In this work, we propose a route to realize high-performance colossal permittivity (CP) by creating multilayer structures of insulator/semiconductor/insulator. To prove the new concept, we made heavily reduced rutile TiO{sub 2} via annealing route in Ar/H{sub 2} atmosphere. Dielectric studies show that the maximum dielectric permittivity (~ 3.0 × 10{sup 4}) of our prepared samples is about 100 times higher than that (~ 300) of conventional TiO{sub 2}. The minimum dielectric loss is 0.03 (at 10{sup 4}–10{sup 5} Hz). Furthermore, CP is almost independent of the frequency (100–10{sup 6} Hz) and the temperature (20–350 K). We suggest that the colossal permittivity is attributed to the high carrier concentration of the inner TiO{sub 2} semiconductor, while the low dielectric loss is due to the presentation of the insulator layer on the surface of TiO{sub 2}. The method proposed here can be expanded to other material systems, such as semiconductor Si sandwiched by top and bottom insulator layers of Ga{sub 2}O{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electron–Phonon Coupling in Ti/TiN MKIDs Multilayer Microresonator

Over the last few years, there has been a growing interest toward the use of superconducting microwave microresonators operated in quasi-thermal equilibrium mode, especially applied to single particle detection. Indeed, previous devices designed and tested by our group with X-ray sources in the keV range evidenced that several issues arise from the attempt of detection through athermal quasiparticles produced within direct strikes of X-rays in the superconductor material of the resonator. In order to prevent issues related to quasiparticles self-recombination and to avoid exchange of athermal phonons with the substrate, our group focused on the development of thermal superconducting microresonators. In this configuration, resonators composed of multilayer films of Ti/TiN sense the temperature of an absorbing material. To maximize the thermal response, low-critical-temperature films are preferable. By lowering the critical temperature, though, the maximum probing power bearable by the resonators decreases abruptly because of the weakening of the electron–phonon coupling. A proper compromise between the value of critical temperature (and hence sensitivity to energy deposition) and readout power bearable by the device has to be found in order to avoid signal-to-noise ratio degradation. In this contribution, we report the latest measurement of the electron–phonon coupling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Development of Multilayer Films Obtained From Epoxidized Methyl Esters, Polyhydroxyalkanoates and Their Combinations

The aim of this work was the production and characterization of films prepared from starch, gelatin and methyl esters of epoxidized macauba (Acrocomia aculeata), corn (Zea mays), pacu (Piaractus mesopotamicus), pintado (Pseudoplatystoma corruscans) and soybean (Glycine max) and also multilayer films of polyhydroxyalkanoates (PHA) conjugated with two of the epoxides that presented the best results in characterizations. The two types of films EEF (Epoxidized esters films) and EEFPHA (Epoxidized esters and PHA conjugated films) were both characterized for their visual aspects, solubility in water and acid, width, color, opacity, water vapor permeability, tensile strength and elongation. EEFPHA were also characterized by differential scanning calorimetry, scanning electron microscopy and X-ray diffraction analyses. The epoxidation reaction was successfully carried out; with the GC-MS analysis indicating the formation of epoxidized esters derived from linoleic and oleic acids. The addition of the epoxidized esters to the EEF films caused an increase in film thickness, opacity, solubility in water, tensile strength and elongation, while the solubility in acid presented the same value as compared to the blank sample. In the EEFPHA samples, addition of filmogenic solution of epoxidized esters from corn and macauba presented a value exceeding the standard in the thickness, opacity, water solubility, water vapor permeability and tensile strength analyses. In the analysis of solubility in acid these samples showed results below the standard, and the elongation test showed values very close. DSC, SEM and XRD results showed that there was a polymeric incorporation between the starch and the PHA.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of Natural and Accelerated Aging on the Mechanical Performance of a Composite Based on Recycled Multilayer Carton

A composite elaborated from waste material was studied for its proposed use as a wood plastic composite. Multilayer food cartons and recycled high density polyethylene were used for the elaboration of laminates, in a proportion of 55% and 45% volume fraction, respectively. The samples were subjected to an aging in an accelerated weathering (AW) chamber for 0, 500, 1000 and 2000 h with UVB radiation, temperature and humidity cycles. Samples exposed to natural weathering (NW) for 0, 1300, 2600 and 5200 h, in a warm sub-humid environment were also studied, the aim being to elucidate a correlation of the useful lifespan of the material. In both cases, after the exposure, three-point bend tests were performed to evaluate the effect on the mechanical properties. The analysis of the degradation process was carried out by infrared spectroscopy, indicating that the AW and NW samples showed deterioration of the material in different proportions. By mean of thermal analysis, it was possible to associate the degradation with the appearance and/or growth of the endothermic peaks, showing a variation in the melting temperature as the time of exposure to AW and NW increased, resulting in a change in the crystallinity percentage. The modulus of rupture (MOR) and the flexural modulus of elasticity decreased by 20% in samples subjected to AW for 2000 h; while in the samples exposed to NW, required of 5200 h to obtain a reduction of 16% in the MOR.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Model Proposed to Calculate the Exchange Interaction in Ni/Pt Multilayers

The behavior of spin waves is mainly influenced by all parameters that characterize the magnetic material such as exchange interactions, surface and volume anisotropy effects, dipole interactions, and phase transitions and imperfections. In this article, we develop a simple calculation model based on a ferromagnetic anisotropic system that has allowed us to obtain numerical estimates for the Pt exchange interaction and the interlayer coupling force at various Ni/Pt multilayers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Resistance Anomalies at Superconducting Transition in Multilayer N/S/F/S/N Heterostructures

We have prepared lateral N/S/F/S/N heterostructures from perovskite bilayer YBa{sub 2}Cu{sub 3}O{sub 7−x} (YBCO (70 nm), as superconductor S) and La{sub 1−x}Sr{sub x}MnO{sub 3} (LSMO (30 nm), as ferromagnet F) covered ex situ by Au layer (normal metal N, 50 nm) and Ti layer (50 nm). Whereas the Ti layer serves as a mask at Ar{sup +} ion beam etching, the gold layer protects the properties of bilayer LSMO/YBCO during the fabrication process mainly during Ga{sup +} focused ion beam etching. In many cases, the resistance vs. temperature (R(T)) dependences of the heterostructures exhibited some peculiarities (resistance peaks and dips) at superconducting transition. To explain these anomalies, we used transport effects emerging between resistances of individual layers and resistances of their interfaces. Our simulations fit very well the experimental R(T) dependences of N/S/F/S/N heterostructures and show that transport effects can play an important role in multilayer structures which can be used in spintronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of Chemical Composition on Volume and Surface Magnon Creation in Multilayer Co{sub x}Pt{sub 1−x}/Pt

The existence of two types of magnon populations created in volume and in the surfaces of the Co{sub x}Pt{sub 1−x}/Pt multilayer was demonstrated. A band structure of these magnons was evidenced by the shape of the calculated excitation spectra. Two bands of energy allowed for a creation of these magnetic excitations are obtained. “Creation gaps” and associated lifetimes are also calculated. The comparison of the calculated relaxation times with experimental results is more than satisfactory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic Properties and Electronic Structure of Co/Zr Multilayers

We investigate the magnetic and electronic properties of Co/Zr multilayers with an emphasis on the interfacial effects. The saturation magnetization, coercivity, and uniaxial anisotropy depend significantly on Co thickness. Spin-wave resonance modes were observed, and the change of resonant field as a function of mode number (n) obeys the so-called n{sup 2} law. The interlayer coupling constant was determined. The electronic properties of the interfacial alloys were studied using the WIEN2k code, employing the density functional theory. Calculations describe satisfactorily the observed magnetic behaviour. The influence of pressure on the magnetic properties of the interfacial Co{sub 1−x}Zr{sub x} alloys was investigated in which we demonstrate that the ferromagnetism is altered by pressure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic Properties and Electronic Structure of Ni/C Multilayer Films

The magnetic properties of Ni/C multilayers were investigated using vibrating sample magnetometer and ferromagnetic resonance (FMR). Spin wave resonances were seen in FMR and the spin wave was found to be sustained through whole layers. The interlayer coupling constant was small pointing out a weak exchange coupling between Ni films through C spacers. The FMR linewidth, in parallel geometry, of the uniform mode decreases with the increase in Ni thickness from 30 to 300 Å which can be understood by considering interfacial effects. The magnetization decreases with decreasing Ni thickness due to the structural imperfections associated with the presence of Ni{sub 1−x}C{sub x} alloys at the interface. Density functional theory (DFT) has been performed to shed light on the decrease in magnetic moment at the interfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Origin of Interfacial Magnetic Anisotropy in Ta/CoFeB/MgO and Pt/CoFeB/MgO Multilayer Thin Film Stacks

Interfacial perpendicular magnetic anisotropy (PMA) in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO and Ta/Co{sub 40}Fe{sub 40}B{sub 20}/MgO multilayer structures has been researched at various CoFeB layer thicknesses. Magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer (VSM) measurements show that while strong PMA is achieved in Ta/Co{sub 40}Fe{sub 40}B{sub 20}/MgO structure for the thickness of Co{sub 40}Fe{sub 40}B{sub 20} range from 0.5 to 1.0 nm, a very weak PMA is observed in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO film stack for the same Co{sub 40}Fe{sub 40}B{sub 20} thicknesses. Based on the experimental results, the interfacial anisotropy energy in Ta/Co{sub 40}Fe{sub 40}B{sub 20}/MgO (1.17 erg/cm{sup 2}) was found to be almost 2.5× larger than that in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO (0.43 erg/cm{sup 2}). It is accepted that the PMA comes from the seed/ferromagnetic and ferromagnetic/oxide layer interfaces. Thus, the origin of interfacial magnetic anisotropy can be hybridization and/or crystallinity properties at the interfaces in Ta- and Pt-seeded stacks. While the PMA is strong in Pt/Co/MgO structure, it becomes in-plane in Fe-rich Pt/CoFeB/MgO structure. It is deduced that hybridization between 3d-5d (Co-Pt) orbitals is more dominant in Pt/CoFeB interface than 2p-3d (O-Fe) hybridization at CoFeB/MgO interface in Pt-seeded stacks. In addition, the crystallinity was studied by performing high-resolution x-ray diffraction (HR-XRD) technique. The crystal orientations of Ta and Pt are found as (002) and (111), respectively. The ferromagnetic layer might be induced out-of-plane orientation in Ta-seeded stack due to observing highly crystallized MgO (001). Thus, another reason for in-plane magnetic anisotropy in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO might be the absence of MgO crystallization because Pt is crystallized fcc (111) orientation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

A Problem of Axisymmetric Torsion of a Multilayer Plate with Elastic Links between the Layers

By using the method of compliance functions and the Hankel transformation of the first order, we propose a procedure for the solution of the problem of torsion of a multilayer plate with elastic links between the layers. Two auxiliary functions connected with the transforms of stresses and displacements at the points of the top boundary of the layer are introduced for each layer. The recurrence relations for the auxiliary functions and the compliance functions of neighboring layers of the plate are constructed. For a two-layer plate, we analyze the influence of the coefficients of elastic links and the geometric and mechanical parameters of layers on the distribution of stresses at points of the common boundary of the layers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

The illuminance and temperature distribution degradation of high power GaN LED caused by detachment of multilayer electrode

In this work, the high power GaN-based unpackaged chip was drive with high current of 600 mA and high temperature of 130 °C till failure. A large stain area was found in the main light area of die after degradation and the leakage current increased by tiny range. And the illuminance degraded greatly as shown in distribution map. In the meantime, the temperature rose dramatically. FIB, SEM and TEM characterization demonstrated that the detachment between multilayer metal electrodes was the main cause of the stain area and the degradation of illuminance and temperature, and also the higher junction temperature played a key role in this detachment phenomenon.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Broadband LWIR and MWIR absorber by trapezoid multilayered grating and SiO{sub 2} hybrid structures

A broadband metamaterial absorber with high absorption simultaneously in mid-wave infrared (MWIR) and long-wave infrared (LWIR) was proposed. In the MWIR, the absorption higher than 0.8 is from 4 to 6.3 µm, while the absorption in the LWIR is from 8.7 and 9.6 µm. The absorber is insensitive to the incident angle. The broadband absorption in the MWIR is due to the slow-light effect of the trapezoid multilayered grating structure. And the broadband absorption in the LWIR is due to the phonon polariton resonant of trapezoid SiO{sub 2} layer. In the broadband high absorption region, the atmosphere is transparent, which may greatly promote the practical application of the absorber in double-color IR imaging, detecting, infrared stealth and thermal emitting.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Reflection and transmission of electromagnetic waves by a multilayered solar cell containing organic materials

Light trapping or absorption is a key concept for design and fabricating solar cells. The propagation of electromagnetic waves through a multilayered solar cell containing organic materials has theoretically investigated. In particular, the reflected, transmitted, and absorbed powers are found and defined. The main parameters of the structure and the required equations for TE polarization are presented in detail. The boundary conditions of the electric and magnetic fields of the incident waves are imposed at each interface and Snell’s law is applied. Expressions for the overall reflection and transmission coefficients are provided by a recursive method. The reflected, transmitted, and absorbed powers are determined using these coefficients. In the numerical results, the mentioned powers are computed and illustrated as a function of the angle of incidence, the wavelength, and the thickness of the active layer when the extinction coefficient of the active layer changes.

14 SOLAR ENERGY↗
DOE OSTI2019

Simulation of Gas Production from Multilayered Hydrate-Bearing Media with Fully Coupled Flow, Thermal, Chemical and Geomechanical Processes Using TOUGH+Millstone. Part 3: Production Simulation Results

The TOUGH+Millstone simulator has been developed for the analysis of coupled flow, thermal and geomechanical processes associated with the formation and/or dissociation of CH 4 - /sub>-hydrates in geological media. It is composed of two constituent codes: (a) a significantly enhanced version of the TOUGH+Hydrate simulator, v2.0, that accounts for all known flow, physical, thermodynamic and chemical processes associated with the evolution of hydrate-bearing systems and includes the most recent physical properties relationships, coupled seamlessly with (b) Millstone v1.0, a new code that addresses the conceptual, computational and mathematical shortcomings of earlier codes used to describe the geomechanical response of these systems. The capabilities of the TOUGH+Millstone code are demonstrated in the simulation and analysis of the system flow, thermal, and geomechanical behavior during gas production from a realistic complex offshore hydrate deposit. In the third paper of this series, we apply the simulators described in parts 1 and 2 to a problem of gas production from a complex, multilayered system of hydrate-bearing sediments in an oceanic environment. We perform flow simulations of constant-pressure production via a vertical well and compare those results to a coupled flow-geomechanical simulation of the same process. Finally, the results demonstrate the importance of fully coupled geomechanics when modeling the evolution of reservoir properties during production.

58 GEOSCIENCES↗
DOE OSTI2018

A Multilayer Model for Alumina Inclusion Transformation by Calcium in the Ladle Furnace

Calcium wire injection is widely used for modification of solid alumina inclusions to liquid or partially liquid calcium aluminate. In the present work, a multilayer growth model is proposed for modification of alumina inclusions. Diffusion through a multiphase product layer and mass transfer of solute through the boundary layer to the inclusion are taken into account in this model. It is assumed that the outer surface of the inclusion is thermodynamically in equilibrium with the local steel composition. The results show that the mass transfer of calcium through the boundary layer and within the inclusion is complete in a matter of seconds; furthermore, once the liquid calcium aluminate forms, it quickly consumes the other solid calcium aluminate phases. Because the calcium is so rapidly consumed by the inclusions, the rate of transformation in a calcium treatment process is controlled by the rate that calcium is supplied to the steel by the calcium bubbles.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Synchronous Rolling on Microstructure, Hardness, and Wear Resistance of Laser Multilayer Cladding

A synchronous rolling method was proposed to assist laser multilayer cladding, and the effects of this method on microstructure, microhardness, and wear resistance were studied. Results show that the microstructure and mechanical properties of the traditional cladding layer exhibit periodic inhomogeneity. Synchronous rolling breaks the columnar dendrite crystals to improve the uniformity of the organization, and the residual plastic energy promotes the precipitation of strengthening phases, as CrB, M{sub 7}C{sub 3}, etc. The hardness and wear resistance of the extruded cladding layer increase significantly because of the grain refinement, formation of dislocations, and dispersion strengthening. These positive significances of synchronous rolling provide a new direction for laser cladding technology.

36 MATERIALS SCIENCE↗