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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

TU-FG-BRB-06: A Prompt Gamma-Ray Spectroscopy System for Clinical Studies of in Vivo Proton Range Verification

Purpose: We present a new system to perform prompt gamma-ray spectroscopy during proton pencil-beam scanning treatments, which enables in vivo verification of the proton range. This system will be used for the first clinical studies of this technology. Methods: After successful pre-clinical testing of prompt gamma-ray spectroscopy, a full scale system for clinical studies is now being assembled. Prompt gamma-rays will be detected during patient treatment using an array of 8 detector modules arranged behind a tungsten collimator. Each detector module consists of a lanthanum(III) bromide scintillator, a photomultiplier tube, and custom electronics for stable high voltage supply and signal amplification. A new real-time data acquisition and control system samples the signals from the detectors with analog-to-digital converters, analyses events of interest, and communicates with the beam delivery systems. The timing of the detected events was synchronized to the cyclotron radiofrequency and the pencil-beam delivery. Range verification is performed by matching measured energy- and timeresolved gamma-ray spectra to nuclear reaction models based on the clinical treatment plan. Experiments in phantoms were performed using clinical beams in order to assess the performance of the systems. Results: The experiments showed reliable real-time analysis of more than 10 million detector events per second. The individual detector modules acquired accurate energy- and time-resolved gamma-ray measurements at a rate of 1 million events per second, which is typical for beams delivered with a clinical dose rate. The data acquisition system successfully tracked the delivery of the scanned pencil-beams to determine the location of range deviations within the treatment field. Conclusion: A clinical system for proton range verification using prompt gamma-ray spectroscopy has been designed and is being prepared for use during patient treatments. We anticipate to start a first clinical study in the near future. This work was supported by the Federal Share of program income earned by Massachusetts; General Hospital on C06-CA059267, Proton Therapy Research and Treatment Center.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Vertically Aligned Carbon Nanotubes Grown on Copper Foil as Electrodes for Electrochemical Double Layer Capacitors

This study reports a binder-free, catalyst-free method for fabricating vertically aligned carbon nanotubes (VACNTs) directly on copper (Cu) foil using plasma-enhanced chemical vapor deposition (PECVD) for electrochemical double-layer capacitor (EDLC) applications. This approach eliminates the need for catalyst layers, polymeric binders, or substrate pre-treatments, simplifying electrode design and enhancing electrical integration. The resulting VACNTs form a dense, uniform, and porous array with strong adhesion to the Cu substrate, minimizing contact resistance and improving conductivity. Electrochemical analysis shows gravimetric specific capacitance (C grav ) and areal specific capacitance (C areal ) of 8 F g −1 and 3.5 mF cm −2 at a scan rate of 5 mV/s, with low equivalent series resistance (3.70 Ω) and charge transfer resistance (0.48 Ω), enabling efficient electron transport and rapid ion diffusion. The electrode demonstrates excellent rate capability and retains 92% of its initial specific capacitance after 3000 charge–discharge cycles, indicating strong cycling stability. These results demonstrate the potential of directly grown VACNT-based electrodes for high-performance EDLCs, particularly in applications requiring rapid charge–discharge cycles and sustained energy delivery.

25 ENERGY STORAGE↗
DOE OSTI2018

Study on Corrosion Behavior of 7075 Aluminum Alloy with Retrogression and Reaging Using Taguchi Method

The corrosion resistance and mechanical properties of 7075 aluminum alloy are improved by retrogression and reaging (RRA) heat treatment. Due to the complex process of RRA heat treatment, a Taguchi L25 orthogonal array is designed to optimize the process parameters of RRA heat treatment. In this work, analysis of variance was performed to find out the significant heat treatment parameters. Microstructure, mechanical properties, intergranular corrosion, exfoliation corrosion and stress corrosion cracking behaviors of 7075 aluminum alloy after RRA heat treatment were investigated by tensile test, slow strain rate test, transmission electron microscope and scanning electron microscope. Results showed that the RRA treatment involving preaging at 120 °C for 16 h, retrogression at 200 °C for 8 min and reaging at 120 °C for 24 h resulted in a desired combination of corrosion resistance and mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Mitigating challenges in aberration-corrected electron-beam lithography on electron-opaque substrates

Aberration-corrected electron-beam lithography (AC-EBL) using ultra-thin electron transparent membranes has achieved single-digit nanometer resolution in two widely used electron-beam resists: poly (methyl methacrylate) (PMMA) and hydrogen silsesquioxane. On the other hand, AC-EBL implementation on thick, electron-opaque substrates is appealing for conventional top-down fabrication of quantum devices with nanometer-scale features. To investigate the performance of AC-EBL on thick substrates, we measured the lithographic point spread function of a 200 keV aberration-corrected scanning transmission electron microscope by defining both positive and negative patterns in PMMA thin films, spin-cast on thick SiO 2 /Si substrates. We present the problems encountered during pre-exposure beam focusing and discuss methods to overcome them. In addition, applying some of these methods using commercial 50 nm thick SiN X membranes with thick Si support frames, we printed arrays of holes in PMMA with pitches around 26 nm on SiN X /Si substrates with increasing Si thickness. Here, our results show that proximity effects from even 50 nm thick SiN X membranes limit hole arrays to 20 nm pitch; however, down to this limit, the effect of the substrate thickness on the pattern quality is minimal. These results highlight the need for novel resists less susceptible to proximity effects, or resists which can be used directly, after development, as the dielectric material in periodic gates in 2D quantum devices.

2D quantum devices↗
DOE OSTI2016

Synthesis of self-organized TiO{sub 2} nanotube arrays: Microstructural, stereoscopic, and topographic studies

In this work, titanium dioxide nanotubes were prepared by using titanium foils via electrochemical anodization in ethylene glycol solutions containing different amounts of water and fluoride in the ranges of 1%–3% and 0.15%–0.5%, respectively, to determine their effects on morphology, optical, and crystalline structure properties. Annealing processes were performed on all samples in the range between 273 and 723 K. Morphology and structure properties of the samples were studied by scanning electron microscopy, X-ray diffraction (XRD), and transmission electron microscopy. Titanium dioxide (TiO{sub 2}) nanotubes, through anodization method, are strongly influenced by conditions, like fluoride concentration and applied voltages. Tube lengths between 2 and 7 μm were obtained, exhibiting different diameters and wall thicknesses. When alternating voltage was applied, the outer surface of the nanotubes exhibited evenly spaced ring-shaped regions, while smooth tubes were observed when constant voltage was applied. Reflection peaks, corresponding to Brookite, Anatase, and Rutile, of TiO{sub 2} phases, were observed from the XRD pattern. These phases were corroborated via μXRD measurements, and the Ti{sub 3}O{sub 5} phase was also observed in detail. Absorption coefficient (α), optical band gap (Eg), and extinction coefficient (ε) of TiO{sub 2} nanotubes were calculated by transmittance spectra in the UV–Vis range. Strong absorption was noted in the UV region from reflectance and absorbance measurements. A correlation between synthesis parameters and physical properties is presented.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nanofabrication of silicon surfaces for reduced virus adhesion

Nanofabrication is a remarkably effective technique to create desirable nanoscale patterns. Here, the effect of surface nanofabrication on altering virus adhesion to the substrates was examined. Arrays of nanoholes, 50 nm in diameter, 22 nm deep, and 100 nm in pitch distance, were created on silicon (Si) wafers by electron-beam lithography and reactive ion etching. MS2 coliphage, which is 26 ± 2 nm in diameter and is frequently used as a surrogate for human viruses, was applied to investigate the interaction between the virions and smooth or nanostructured Si surfaces. Scanning electron microscopy and atomic force microscopy along with surface wettability analyses revealed that the nanofabrication had the effect of reducing not only the number of viruses attached but also the strength of virus adhesion. These effects were ascribed to the presence of nanoholes, which were inaccessible to the virions due to the unique surface topographical parameters and the surface chemistry, resulting in the decrease of the overall solid contact area for MS2 attachment. The periodic spacing of the nanoholes also limited the unit landing area for MS2 particles, restricting the formation of MS2 aggregates and leading to the reduced amount of MS2 attachment. We anticipate that smart design of a surface’s chemical composition and nanostructure will offer a feasible solution to improve mitigations for controlling viral adhesion and transmission to and from food contact surfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Titania nanotube arrays surface-modified with ZnO for enhanced photocatalytic applications

Highlights: • Heterostructures of TNA/ZnO synthesised through potentiostatic anodisation followed by hydrothermal method. • Evaluation of morphological features of the heterostructure with hydrothermal processing time. • Correlation of photocatalytic activity of the hetrostructure with its morphology and surface texture. - Abstract: Well ordered titanium dioxide nanotube arrays (TNA) of average diameter 129 nm and wall thickness of 25 nm were fabricated through potentiostatic anodisation of titanium (Ti) metal substrates. Such TNA were subsequently surface-modified with various amounts of zinc oxide (ZnO) nanopowders using hydrothermal technique to obtain heterogeneous TNA/ZnO nanostructures. The crystalline phase and surface microstructure of the heterostructures were determined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy respectively. The morphology of the heterostructures strongly depended on the hydrothermal conditions employed. The photocatalytic activity of the heterostructures have also been investigated and correlated with their surface morphology and texture.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Focal Plane Array Low Background Testing (Focal Plane Array Characterization under a Low Background)

Most infra-red (IR) imagers for tactical applications use a direct injection (DI) input amplifier design. Fewer transistors in the unit cell allow the read-out electronic circuit (ROIC) to be minimized. This allows either more room for charge integration capacitors or finer pixel pitches. These ROICs work well at high background irradiance levels. However, at low background irradiance levels photocurrent inject efficiency for a DI unit cell amplifier is reduced. Some models have shown that this efficiency can drastically affect performance under low background conditions. The main benefit for Sandia National Laboratories (SNL) and L-3 Communications Cincinnati Electronics (L-3) was a better understanding of these types of sensors under low background conditions. It also provided the opportunity for an independent analysis of these sensors. The purpose of this project was to measure DI for low light levels under different operating temperatures of the L-3 CE103 a 1280 x 1024 indium antimonide 15 micron pitch detector. Results showed DI efficiency approaches 75% under extremely low light levels. Additionally, measured data didn't conform well to traditional circuit based models indicated that other effects are contributing to DI efficiency. A "spot scanning" PSF measurement was also conducted to measure pixel-to-pixel crosstalk for this array. Spot scanning data showed near ideal performance.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Effect of thermal implying during ageing process of nanorods growth on the properties of zinc oxide nanorod arrays

Undoped and Sn-doped Zinc oxide (ZnO) nanostructures have been fabricated using a simple sol-gel immersion method at 95°C of growth temperature. Thermal sourced by hot plate stirrer was supplied to the solution during ageing process of nanorods growth. The results showed significant decrement in the quality of layer produced after the immersion process where the conductivity and porosity of the samples reduced significantly due to the thermal appliance. The structural properties of the samples have been characterized using field emission scanning electron microscopy (FESEM) electrical properties has been characterized using current voltage (I-V) measurement.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

The EBEX Balloon-borne Experiment—Gondola, Attitude Control, and Control Software

The E and B Experiment (EBEX) was a long-duration balloon-borne instrument created to measure the polarization of the cosmic microwave background (CMB) radiation. EBEX was the first balloon-borne instrument to implement a kilopixel array of transition edge sensor (TES) bolometric detectors and the first CMB experiment to use the digital version of the frequency domain multiplexing system for readout of the TES array. The scan strategy relied on 40 s peak-to-peak constant-velocity azimuthal scans. We report on the unique demands on the design and operation of the payload that resulted from these new technologies and the scan strategy. We describe the solutions implemented, including the development of a power system designed to provide a total of at least 2.3 kW, a cooling system to dissipate 590 W consumed by the detectors' readout system, software to manage and handle the data of the kilopixel array, and specialized attitude reconstruction software. We demonstrate flight performance data reflecting faultless management of the TES array, adequate powering and cooling of the readout electronics, and constraint of attitude reconstruction errors such that the spurious B-modes they induced were less than 10% of the CMB B-mode power spectrum with r = 0.05.

polarization↗
DOE OSTI2019

Highly Uniform Resistive Switching in HfO 2 Films Embedded with Ordered Metal Nanoisland Arrays

Memristors enter a critical developmental stage where emerging large-scale integration methods face major challenges with severe switching instabilities in the oxide layer. In this work, the superior uniformity is achieved within HfO 2 films by embedding highly ordered metal nanoisland (NI) arrays. Embedded films exhibit a significant reduction in both SET and RESET while displaying enhanced uniformity in operating voltages and resistance states. This behavior is attributed to the concentration of electric fields along Pt and Ti NIs and their interactions with the surrounding oxide film matrix environment, which induce separate and distinct filamentary formation mechanisms that affect the stability. A method is reported to further optimize the uniformity of the SET voltage by translating the NI array position down the film-thickness dimension towards the bottom electrode. A comparison of the density and distribution of the oxygen vacancies responsible for the formation/dissolution of conducting filaments is made via combined electrostatic force microscopy and conductive atomic force microscopy (c-AFM) studies. Finally, complete observation of the morphological evolution of conducting filaments produced by Pt and Ti is enabled by 3D c-AFM nanotomography and cross-sectional scanning transmission electron microscopy–energy dispersive spectroscopy to provide direct correlations between NI-oxide interactions and overall switching performance.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Understanding Formation of Irradiation-Induced Defects through 4D-STEM, Electron Tomography, and WBDF-STEM

A major challenge in advancing nuclear materials for next-generation fission and proposed fusion reactors is to comprehensively understand the formation of irradiation-induced defects. Here it is essential to correlate the evolution of irradiation-induced defects and the degradation of mechanical properties, as they collectively dictate the material's lifespan and ensure nuclear safety. Scanning transmission electron microscopy (STEM) based techniques have emerged as indispensable tools for irradiation-induced defect characterization, offering high spatial resolution imaging and chemical analysis, such as electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). These techniques have been effectively used to obtain an atomic-scale view of the defect structure. Recent advances in electron microscopy, particularly in 4D-STEM, offer detailed insight into microstructural evolution by capturing full 2D diffraction patterns at every pixel position. Using high-speed direct electron detectors, this technology generates a four-dimensional dataset, overcoming the limitations of traditional STEM imaging.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Resistive Coatings for High-performance, Low-background MCPs Operating Across Broad Temperature Ranges and at Cryogenic Temperatures

Microchannel plate with improved thermo-electric properties are a high risk, high payoff development undertaken by a consortium of effort that links the Argonne National Lab, the Space-Science Lab at UC Berkeley and the small businesses (Incom Inc.) that will commercialize the advanced technology in open MCPs and LAPPDs. This development will satisfy the needs for new instrumentation for homeland security (non-proliferation) sensors to screen vehicles and cargo for Special Nuclear Materials (SNMs) and scientific detectors for astrophysics, electron microscopy, time-of-flight mass spectrometry, molecular and atomic collision studies, and fluorescence imaging applications in biotechnology and medical imaging products including positron emission tomography (PET scanning).

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2022

Emergence of distinct electronic states in epitaxially-fused PbSe quantum dot superlattices

Abstract Quantum coupling in arrayed nanostructures can produce novel mesoscale properties such as electronic minibands to improve the performance of optoelectronic devices, including ultra-efficient solar cells and infrared photodetectors. Colloidal PbSe quantum dots (QDs) that self-assemble into epitaxially-fused superlattices (epi-SLs) are predicted to exhibit such collective phenomena. Here, we show the emergence of distinct local electronic states induced by crystalline necks that connect individual PbSe QDs and modulate the bandgap energy across the epi-SL. Multi-probe scanning tunneling spectroscopy shows bandgap modulation from 0.7 eV in the QDs to 1.1 eV at their necks. Complementary monochromated electron energy-loss spectroscopy demonstrates bandgap modulation in spectral mapping, confirming the presence of these distinct energy states from necking. The results show the modification of the electronic structure of a precision-made nanoscale superlattice, which may be leveraged in new optoelectronic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Field Emission Properties of Cu-Filled Vertically Aligned Carbon Nanotubes Grown Directly on Thin Cu Foils

Copper-filled vertically aligned carbon nanotubes (Cu@VACNTs) were grown directly on Cu foil substrates of 0.1 mm thicknesses at different temperatures via plasma-enhanced chemical vapor deposition (PECVD). By circumventing the need for additional catalyst layers or intensive substrate treatments, our in-situ technique offers a simplified and potentially scalable route for fabricating Cu@VACNTs with enhanced electrical and thermal properties on thin Cu foils. Comprehensive analysis using field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) mappings, and X-ray diffraction (XRD) revealed uniform Cu filling within the VACNTs across a range of synthesis temperatures (650 °C, 700 °C, and 760 °C). Field emission (FE) measurements of the sample synthesized at 700 °C (S700) showed low turn-on and threshold fields of 2.33 V/μm and 3.29 V/μm, respectively. The findings demonstrate the viability of thin Cu substrates in creating dense and highly conductive Cu-filled VACNT arrays for advanced electronic and nanoelectronics applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Multi-scale time-resolved electron diffraction: A case study in moiré materials

Ultrafast-optical-pump — structural-probe measurements, including ultrafast electron and x-ray scattering, provide direct experimental access to the fundamental timescales of atomic motion, and are thus foundational techniques for studying matter out of equilibrium. High-performance detectors are needed in scattering experiments to obtain maximum scientific value from every probe particle. Here we deploy a hybrid pixel array direct electron detector to perform ultrafast electron diffraction experiments on a WSe 2 /MoSe 2 2D heterobilayer, resolving the weak features of diffuse scattering and moiré superlattice structure without saturating the zero order peak. Enabled by the detector’s high frame rate, we show that a chopping technique provides diffraction difference images with signal-to-noise at the shot noise limit. Finally, we demonstrate that a fast detector frame rate coupled with a high repetition rate probe can provide continuous time resolution from femtoseconds to seconds, enabling us to perform a scanning ultrafast electron diffraction experiment that maps thermal transport in WSe 2 /MoSe 2 and resolves distinct diffusion mechanisms in space and time.

36 MATERIALS SCIENCE↗
DOE OSTI2016

TH-EF-207A-03: Photon Counting Implementation Challenges Using An Electron Multiplying Charged-Coupled Device Based Micro-CT System

Purpose: To successfully implement and operate a photon counting scheme on an electron multiplying charged-coupled device (EMCCD) based micro-CT system. Methods: We built an EMCCD based micro-CT system and implemented a photon counting scheme. EMCCD detectors use avalanche transfer registries to multiply the input signal far above the readout noise floor. Due to intrinsic differences in the pixel array, using a global threshold for photon counting is not optimal. To address this shortcoming, we generated a threshold array based on sixty dark fields (no x-ray exposure). We calculated an average matrix and a variance matrix of the dark field sequence. The average matrix was used for the offset correction while the variance matrix was used to set individual pixel thresholds for the photon counting scheme. Three hundred photon counting frames were added for each projection and 360 projections were acquired for each object. The system was used to scan various objects followed by reconstruction using an FDK algorithm. Results: Examination of the projection images and reconstructed slices of the objects indicated clear interior detail free of beam hardening artifacts. This suggests successful implementation of the photon counting scheme on our EMCCD based micro-CT system. Conclusion: This work indicates that it is possible to implement and operate a photon counting scheme on an EMCCD based micro-CT system, suggesting that these devices might be able to operate at very low x-ray exposures in a photon counting mode. Such devices could have future implications in clinical CT protocols. NIH Grant R01EB002873; Toshiba Medical Systems Corp.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Magnetocardiography with a 16-channel fiber-coupled single-cell Rb optically pumped magnetometer

We have constructed a low-cost, portable, high-sensitivity 16-channel optically pumped magnetometer (OPM), operating in the spin-exchange relaxation-free regime, and demonstrated its applications in magnetocardiography (MCG). The decrease in the cost of sensors by an order of magnitude is achieved by the 16-channel operation realized in a single module using a single large flat pancake rubidium vapor cell, broad pump and probe laser beams, and a 16-channel photodiode array. The OPM is also based on a fiber-coupled nearly parallel-beam configuration to facilitate multichannel design and make the system portable. For human MCG experiments, the 16-channel OPM which includes optical components is placed inside a wooden enclosure for laser safety. The enclosure is set on a nonmagnetic table inside a magnetically shielded room, while the lasers and electronics are placed outside the shielding room, to avoid magnetic noise. We show that the 16-channel OPM enables simultaneous imaging of human cardiac activity on a large area of the chest in a single scan. The multichannel capability will accelerate clinical MCG imaging to reduce the procedure time and patient fatigue.

59 BASIC BIOLOGICAL SCIENCES↗