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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

2012 Joint Research Target (JRT) Final Report

The report summarizes: [1] Diagnostic upgrades and analysis improvements that support the JRT; [2] Descriptions of new experiments and a brief summary of findings; [3] New analysis of previous experiments; [4] Plans for further data analysis and recommendations for further work; [5] Scientific publications that are derived from or contributed directly to the JRT. The report is organized as follows: Section 1: Describes inter-machine comparisons that were facilitated by the JRT focus. Similarities and differences found on the different facilities are outlined, and plans for additional analysis of data and supporting simulations are described.Section 2: Reviews diagnostic development, experiments and results from C-Mod. C-Mod dedicated 13.1 run days to the JRT divided among 10 experimental proposals. These were organized into three general thrust areas that represent distinct experimental approaches to realizing the regimes called for in the JRT description. Initial comparisons with linear and nonlinear simulation have been carried out for these experiments, and plans for an extensive campaign of analysis have been outlined. Section 3: Reviews results from DIII-D including new experiments, detailed comparisons of simulations to previously collected data and connections between the new work and past research. Four experimental days were dedicated to the JRT in 2012. These included studies of L-modes, H-modes and QH-modes. Section 4: Summarizes new analysis of data collected before the NSTX shutdown. The work focuses on the roles of low and high-k turbulence; collisionality scans and impurity particle transport.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Hydrothermal synthesis of nanostructured zinc oxide and study of their optical properties

Highlights: Black-Right-Pointing-Pointer Nanostructured ZnO were successfully obtained by a hydrothermal route. Black-Right-Pointing-Pointer Inorganic precursor and molar ratio are key factors for morphology and particle size. Black-Right-Pointing-Pointer Optical properties were also studied. -- Abstract: Nanostructured ZnO (nanorods, nanoshuttles) have been synthesized by hydrothermal approach using ZnCl{sub 2} or Zn(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O as zinc sources and cetyltrimethylammonium bromide as structure-directing agent. Techniques X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible absorption, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy have been used to characterize the structure, morphology and composition of the nanostructured zinc oxide. The optical properties of the as-obtained materials were also studied and showing that it is possible to apply the ZnO nanoshuttles and nanorods on the UV filter, photocatalysis, and special optical devices.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural, thermal and electrical characterizations of multiwalled carbon nanotubes and polyaniline composite

The undoped and doped composite of MWNTs (Multiwalled Carbon Nanotubes) with PANI (/Polyaniline) was prepared by chemical oxidative polymerization. The MWNTs/PANI composites have been characterized by using various techniques like Thermogravometric Analysis (TGA), Fourier transform infrared (FT-IR) spectrometer and Field emission scanning electron microscope (FE-SEM) and conductivity measurement by using two probe method. TGA results has shown that thermal stability followed the pattern undoped MWNTs/PANI composite < doped MWNTs/PANI composite. FE-SEM micrographs demonstrated the morphological changes on the surface of MWNTs as a result of composite formation. Fourier transformed infrared (FT-IR) spectra ascertained the formation of the composite. Study of electrical characteristics demonstrated that the doped MWNTs/PANI composite (1.2 × 10{sup 1} Scm{sup −1}) have better conductivity than the undoped MWNTs/PANI composite (10{sup −4} Scm{sup −1}). These CNTs based polymeric composites are of great importance in developing new nano-scale devices for future chemical, mechanical and electronic applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

High-Speed Composite Microactuator Based on Ti{sub 2}NiCu Alloy with Shape Memory Effect

Samples of microactuators are made of a bimorph composite of Ti{sub 2}NiCu alloy with a thermoelastic martensitic transition and the shape memory effect, and their response rate is investigated. The active layer of the composite actuator is a layer of the rapidly quenched Ti{sub 2}NiCu alloy, pseudoplastically prestretched, and an amorphous layer of the same alloy is used as an elastic layer. Typical sizes of the microactuator are 30 × 2 × 2 μm. The controlled amplitude of the displacement of the microactuator tip is approximately 1 μm. The response rate of the microactuator was investigated by scanning electron microscopy. Activation of the microactuator was achieved by heating when electric pulses were passed through it. Full activation of the microactuator at frequencies up to 1 kHz was demonstrated; partial activation was observed at frequencies up to 8 kHz. The possibility of operating the device in a self-oscillating mode at frequencies of the order of 100 kHz is demonstrated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Correlation of film morphology and defect content with the charge-carrier transport in thin-film transistors based on ZnO nanoparticles

The correlation of defect content and film morphology with the charge-carrier transport in field-effect devices based on zinc oxide nanoparticles was investigated. Changes in the defect content and the morphology were realized by annealing and sintering of the nanoparticle thin films. Temperature-dependent electrical measurements reveal that the carrier transport is thermally activated for both the unsintered and sintered thin films. Reduced energetic barrier heights between the particles have been determined after sintering. Additionally, the energetic barrier heights between the particles can be reduced by increasing the drain-to-source voltage and the gate-to-source voltage. The changes in the barrier height are discussed with respect to information obtained by scanning electron microscopy and photoluminescence measurements. It is found that a reduction of surface states and a lower roughness at the interface between the particle layer and the gate dielectric lead to lower barrier heights. Both surface termination and layer morphology at the interface affect the barrier height and thus are the main criteria for mobility improvement and device optimization.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Structure and magnetic properties of SiO{sub 2}/PCL novel sol–gel organic–inorganic hybrid materials

Organic–inorganic nanocomposite materials have been synthesized via sol–gel. They consist of an inorganic SiO{sub 2} matrix, in which different percentages of poly(ε-caprolactone) (PCL) have been incorporated. The formation of H-bonds among the carbonyl groups of the polymer chains and Si–OH group of the inorganic matrix has been proved by means of Fourier transform infrared spectroscopy (FT-IR) analysis and has been confirmed by solid-state nuclear magnetic resonance (NMR). X-Ray diffraction (XRD) analysis highlighted the amorphous nature of the synthesized materials. Scanning electron microscope (SEM) micrograph and atomic force microscope (AFM) topography showed their homogeneous morphology and nanostructure nature. Considering the opportunity to synthesize these hybrid materials under microgravity conditions by means of magnetic levitation, superconducting quantum interference device (SQUID) magnetometry has been used to quantify their magnetic susceptibility. This measure has shown that the SiO{sub 2}/PCL hybrid materials are diamagnetic and that their diamagnetic susceptibility is independent of temperature and increases with the PCL amount. - Graphical abstract: Characterization and magnetic properties of SiO{sub 2}/PCL organic–inorganic hybrid materials synthesized via sol–gel. FT-IR, Fourier transform infrared spectroscopy; solid-state NMR: solid-state nuclear magnetic resonance; SQUID: superconducting quantum interference device. - Highlights: • Sol–gel synthesis of SiO{sub 2}/PCL amorphous class I organic–inorganic hybrid materials. • FT-IR and NMR analyses show the hydrogen bonds formation between SiO{sub 2} and PCL. • AFM and SEM analyses confirm that the SiO{sub 2}/PCL are homogenous hybrid materials. • The SQUID measures show that the simples are diamagnetic. • Diamagnetic susceptibility of SiO{sub 2}/PCL materials increases with the PCL amount.

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

Influence of surface pattern on the biological properties of Ti grade 2

Highlights: • Laser modification causes changes in chemical composition of the surface. • Laser treatment creates roughness in a range from nano- to micrometers. • The surface modification presented results in a multimodal topography. • A hierarchical topography promotes protein adsorption. - Abstract: This paper presents a detailed characterization of Ti surface geometries as produced by non-contact laser functionalization and its impact on the process of protein adsorption. The proposed surface modification is designed for the local treatment of implantable devices with original roughness. In this work, titanium plates were initially modified by the two most common mechano-chemical treatments, shot peening and acid etching. The material under study was next functionalized DLIL (Direct Laser Interference Lithography) in order to obtained two different surface patterns: grooves and islands. The modified surfaces were characterized in terms of their shape, roughness, wettability, surface energy and chemical composition. For this purpose, the following methods were used: scanning electron microscopy, optical profilometry, atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. Protein adsorption tests were conducted to consider the potential of the proposed methodology in biomedical applications and to compare the influence of the two different surface patterns on the initial state of ossointegration. To this end, XPS and FTIR studies were conducted. The systematic analysis presented will be useful when selecting an appropriate surface geometry for the local surface functionalization of implantable devices.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Electrostatic imaging of encapsulated graphene

Devices made from two-dimensional (2D) materials such as graphene and transition metal dichalcogenides exhibit remarkable electronic properties of interest to many subdisciplines of nanoscience. Owing to their 2D nature, their quality is highly susceptible to contamination and degradation when exposed to the ambient environment. Protecting the 2D layers by encapsulation between hexagonal boron nitride (hBN) layers significantly improves their quality. Locating these samples within the encapsulant and assessing their integrity prior to further processing then becomes challenging. Here we show that conductive scanning probe techniques such as electrostatic force and Kelvin force microscopy make it possible to visualize the encapsulated layers, their charge environment and local defects on the sub-micrometer scale. Our techniques are employed without requiring electrical contact to the embedded layer, providing valuable feedback on the device's local electronic quality prior to any device etching or electrode deposition. We show that these measurement modes, which are simple extensions of atomic force microscopy, are perfectly suited for imaging encapsulated conductors and their local charge environments.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Highly aligned arrays of high aspect ratio barium titanate nanowires via hydrothermal synthesis

We report on the development of a hydrothermal synthesis procedure that results in the growth of highly aligned arrays of high aspect ratio barium titanate nanowires. Using a multiple step, scalable hydrothermal reaction, a textured titanium dioxide film is deposited on titanium foil upon which highly aligned nanowires are grown via homoepitaxy and converted to barium titanate. Scanning electron microscope images clearly illustrate the effect the textured film has on the degree of orientation of the nanowires. The alignment of nanowires is quantified by calculating the Herman's Orientation Factor, which reveals a 58% improvement in orientation as compared to growth in the absence of the textured film. The ferroelectric properties of barium titanate combined with the development of this scalable growth procedure provide a powerful route towards increasing the efficiency and performance of nanowire-based devices in future real-world applications such as sensing and power harvesting.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Formation of Coherent 1H–1T Heterostructures in Single-Layer MoS 2 on Au(111)

Heterojunctions of semiconductors and metals are the fundamental building blocks of modern electronics. Coherent heterostructures between dissimilar materials can be achieved by composition, doping, or heteroepitaxy of chemically different elements. Here, we report the formation of coherent single-layer 1H–1T MoS 2 heterostructures by mechanical exfoliation on Au(111), which are chemically homogeneous with matched lattices but show electronically distinct semiconducting (1H phase) and metallic (1T phase) character, with the formation of these heterojunctions attributed to a combination of lattice strain and charge transfer. The exfoliation approach employed is free of tape residues usually found in many exfoliation methods and yields single-layer MoS 2 with millimeter (mm) size on the Au surface. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS) have collectively been employed to elucidate the structural and electronic properties of MoS 2 monolayers on Au substrates. Bubbles in the MoS 2 formed by the trapping of ambient adsorbates beneath the single layer during deposition, have also been observed and characterized. Lastly, our work here provides a basis to produce two-dimensional heterostructures which represent potential candidates for future electronic devices.

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

Local Resistance Measurement for Degradation of c-Si Heterojunction with Intrinsic Thin Layer (HIT) Solar Modules

Silicon heterojunction with intrinsic thin layer (or HIT) modules typically degrade at a rate of less than 1% annually in solar fields with dominant degradation in open-circuit voltage and some degradation in series resistance. However, detailed mechanisms can differ from module to module. Here, we study increases in local series resistance that occur over long-term field deployment, indicated by cell areas where the photoluminescence intensity does not degrade but the electroluminescence degrades significantly. To directly measure the local series resistance, we have cored out the local electroluminescence-degraded area, and we measured the sheet resistance by 4-point-probe and local nm-scale resistance using scanning spreading resistance microscopy (SSRM). The results by 4-point-probe show scattered sheet resistance that can be caused, for example, by nonuniform current paths through the transparent conductive oxide layer, the a-Si:H emitter, or the near-junction c-Si inversion layer. In contrast, the SSRM results indicate a relatively uniform and non-degraded resistivity on smaller nanometer spatial scales. SSRM is an atomic force microscopy-based two-terminal resistance mapping technique that measures the local resistance in nm-volume beneath the probe. The consistent resistances measured on the control and degraded samples can exclude the degradation of transparent conductive oxide resistance.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2016

Concept of an upright wearable positron emission tomography imager in humans

Abstract Background Positron Emission Tomography ( PET ) is traditionally used to image patients in restrictive positions, with few devices allowing for upright, brain‐dedicated imaging. Our team has explored the concept of wearable PET imagers which could provide functional brain imaging of freely moving subjects. To test feasibility and determine future considerations for development, we built a rudimentary proof‐of‐concept prototype (Helmet_ PET ) and conducted tests in phantoms and four human volunteers. Methods Twelve Silicon Photomultiplier‐based detectors were assembled in a ring with exterior weight support and an interior mechanism that could be adjustably fitted to the head. We conducted brain phantom tests as well as scanned four patients scheduled for diagnostic F 18‐ FDG PET / CT imaging. For human subjects the imager was angled such that field of view included basal ganglia and visual cortex to test for typical resting‐state pattern. Imaging in two subjects was performed ~4 hr after PET / CT imaging to simulate lower injected F 18‐ FDG dose by taking advantage of the natural radioactive decay of the tracer (F 18 half‐life of 110 min), with an estimated imaging dosage of 25% of the standard. Results We found that imaging with a simple lightweight ring of detectors was feasible using a fraction of the standard radioligand dose. Activity levels in the human participants were quantitatively similar to standard PET in a set of anatomical ROI s. Typical resting‐state brain pattern activation was demonstrated even in a 1 min scan of active head rotation. Conclusion To our knowledge, this is the first demonstration of imaging a human subject with a novel wearable PET imager that moves with robust head movements. We discuss potential research and clinical applications that will drive the design of a fully functional device. Designs will need to consider trade‐offs between a low weight device with high mobility and a heavier device with greater sensitivity and larger field of view.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Accurate Quantification of Si/SiGe Interface Profiles via Atom Probe Tomography

Pulsed laser atom probe tomography (APT) has enabled the investigation of semiconducting materials at sub-nm length scales and 10 ppm chemical sensitivity. This has enabled APT to be the best technique for nanoscale detection of dopant distributions and low levels of chemical segregation at interfaces, which are both important for semiconductor processing; however, the accuracy of measured interfacial profiles is typically compromised by aberrations. Interfacial profiles in APT data will vary with respect to different interfacial combinations, especially when the evaporation field between two materials is drastically different. Here, the ability of APT to measure SiGe/Si/SiGe interfacial profiles is tested with an 8 nm Si well embedded in SiGe. The APT measurements are compared to those measured using scanning transmission electron microscopy (STEM) to evaluate reconstruction and post-reconstruction processing methods to appropriately measure interfacial profiles using APT. Without post-APT reconstruction processing, the measured Si/SiGe interfacial widths between APT and STEM match poorly, but after applying the z-redistribution algorithm, the interfacial profiles are in good agreement. These results indicate that APT can be used to accurately identify SiGe/Si/SiGe interfacial profiles after application of the z-redistribution algorithm, which will greatly impact the synergy between growth and characterization of semiconductor devices using Si/SiGe interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Improved Scanning Geometry to Collect 3D-Geometry Data in Flat Samples

3D integration through silicon technology of integrated circuits challenges non-destructive testing methods. 3D x-ray methods are the techniques of choice to localize defects in interconnects. The development of high-power x-ray sources enabled the use of x-ray microscopy in laboratory tools. Those devices are able to resolve features down to 40 nm in an acceptable measurement time. However, the field of view is very limited to 16 {mu}m in high-resolution mode and to 65 {mu}m in large-field-of-view mode. To record tomography data, the size of the samples must not exceed the field of view to circumvent specific artifacts. Semiconductor samples usually do not fulfill the condition mentioned above since they have the shape of flat sheets. Therefore limited-angle tomography is typically used. The missing angles cause typical capping artifacts and poor signal-to-noise ratio. We present a modified scanning geometry that overcomes some of the artifacts and yields a better image quality. The geometry and potential applications are presented in comparison to the traditional limited-angle tomography.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

Activated carbon and single-walled carbon nanotube based electrochemical capacitor in 1 M LiPF{sub 6} electrolyte

Highlights: • Activated carbon and single-walled CNT based electrochemical capacitor. • Electrochemical analysis by means of CV, charge/discharge and impedance. • 1 M LiPF{sub 6} non-aqueous solution as an electrolyte. • AC/SWCNT electrode exhibits a maximum capacitance of 60.97 F g{sup −1}. - Abstract: Carbon nanotubes have been extensively studied because of their wide range of potential application such as in nanoscale electric circuits, textiles, transportation, health, and the environment. Carbon nanotubes feature extraordinary properties, such as electrical conductivities higher than those of copper, hardness and thermal conductivity higher than those of diamond, and strength surpassing that of steel, among others. This research focuses on the fabrication of an energy storage device, namely, an electrochemical capacitor, by using carbon materials, i.e., activated carbon and single-walled carbon nanotubes, of a specific weight ratio as electrode materials. The electrolyte functioning as an ion carrier is 1 M lithium hexafluorophosphate. Variations in the electrochemical performance of the device, including its capacitance, charge/discharge characteristics, and impedance, are reported in this paper. The electrode proposed in this work exhibits a maximum capacitance of 60.97 F g{sup −1} at a scan rate of 1 mV s{sup −1}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Hetero-epitaxial EuO interfaces studied by analytic electron microscopy

With nearly complete spin polarization, the ferromagnetic semiconductor europium monoxide could enable next-generation spintronic devices by providing efficient ohmic spin injection into silicon. Spin injection is greatly affected by the quality of the interface between the injector and silicon. Here, we use atomic-resolution scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy to directly image and chemically characterize a series of EuO|Si and EuO|YAlO{sub 3} interfaces fabricated using different growth conditions. We identify the presence of europium silicides and regions of disorder at the EuO|Si interfaces, imperfections that could significantly reduce spin injection efficiencies via spin-flip scattering.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find use in the design of integrated surface-wave devices with suppressed crosstalk.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗