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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Electrical behavior of atomic layer deposited high quality SiO{sub 2} gate dielectric

Comprehensive and systematic electrical studies were performed on fabrication of high quality SiO{sub 2} thin films MOS capacitor using the robust, novel, and simple atomic layer deposition (ALD) technique using highly reactive ozone and tris (dimethylamino) silane (TDMAS) precursors. Ideal capacitance–voltage curve exhibits a very small frequency dispersion and hysteresis behavior of the SiO{sub 2} MOS capacitor grown at 1 s TDMAS pulse, suggesting excellent interfacial quality and purity of the film as probed using x-ray photoelectron studies. The flat-band voltage of the device shifted from negative toward positive voltage axis with increase of TDMAS pulses from 0.2 to 2 s. Based on an equivalent oxide thickness point of view, all SiO{sub 2} films have gate leakage current density of (5.18 × 10{sup −8} A/cm{sup 2}) as well as high dielectric break down fields of more than (∼10 MV/cm), which is better and comparable to that of thermally grown SiO{sub 2} at temperatures above 800 °C. These appealing electrical properties of ALD grown SiO{sub 2} thin films enable its potential applications such as high-quality gate insulators for thin film MOS transistors, as well as insulators for sensor and nanostructures on nonsilicon substrates.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Bias-Modulated ALD of ZnO: Insights into Precursor-Surface Interactions for ZnO Films

Atomic layer deposition (ALD) is widely used to deposit conformal thin films but is often limited in the tunability of the resulting material’s properties. Substrate bias and electric fields alter precursor-surface interactions and provide means to tune material properties. To explore this, we performed zinc oxide (ZnO) ALD using diethylzinc (DEZ) and water on silicon native oxide substrates at 150 °C in a sample holder designed to create a static electrical field by biasing one plate of a parallel plate capacitor-style sample holder during deposition. ZnO films prepared in an electric field/on a biased sample holder were thinner, changed relative crystalline composition, and contained more carbon compared to samples grown in identical sample holders without bias. The thickness was independent of the magnitude of the eletric field between plates, indicating that the primary driver for the change was substrate biasing not the electric field between plates of the parallel plate capacitor-style sample holder. Density functional theory calculations showed enhanced electron migration between dissociatively adsorbed DEZ molecules and the ZnO (002) facet with increasing force from an electric field at the substrate surface, which strengthens the electronic interactions between the surface and the adsorbate. These models offer a compelling explanation for the inhibited growth, changes in the crystallinity, and increase in carbon content of films grown in an electric field/on biased plates.

Jones, Jessica C. (ORCID:0000000174754620)↗
DOE OSTI2022

Harvesting Wave Energy to Power Acoustic Transmitters Using Triboelectric Nanogenerator

Wave energy has the largest reserves and widest distribution among blue energy sources. However, the conversion and utilization of ocean wave energy are challenging. In this work, we developed a contact-separation mode triboelectric nanogenerator (TENG) with a simple structure for harvesting wave energy and powering marine sensors and transmitters and performed detailed electrical characterization under controlled laboratory conditions. A prototype power management circuit (PMC) was implemented to improve the output performance of the TENG. The output from the PMC could charge up a storage capacitor for powering sensors and electronics. Eventually, the TENG was integrated within a water-proof enclosure and tested using a custom-built wave simulator to evaluate the device performance in a more representative scenario. The device sustainably powered up an array of 27 LEDs and was able to charge up a capacitor up to 1.8 V for driving an acoustic transmitter. The results demonstrate that TENG technology shows great promise in harvesting low-frequency ocean wave energy.

Yang, Yang↗
DOE OSTI2014

A novel electron gun for inline MRI-linac configurations

Purpose: This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Methods: Simple electron gun geometry modifications of a Varian 600C electron gun are considered and solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Results: Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ±15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. Conclusions: In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Nitrogen-doped mesoporous carbon of extraordinary capacitance for electrochemical energy storage

Store more energy with a touch of nitrogen In contrast to batteries, capacitors typically can store less power, but they can capture and release that power much more quickly. Lin et al. fabricated a porous carbon material that was then doped with nitrogen. This raised the energy density of the carbon more than threefold—an increase that was retained in full capacitors, without losing their ability to deliver power quickly. Science , this issue p. 1508

Lin, Tianquan↗
DOE OSTI2022

Reconfigurable perovskite nickelate electronics for artificial intelligence

Reconfigurable devices offer the ability to program electronic circuits on demand. Here, in this work, we demonstrated on-demand creation of artificial neurons, synapses, and memory capacitors in post-fabricated perovskite NdNiO 3 devices that can be simply reconfigured for a specific purpose by single-shot electric pulses. The sensitivity of electronic properties of perovskite nickelates to the local distribution of hydrogen ions enabled these results. With experimental data from our memory capacitors, simulation results of a reservoir computing framework showed excellent performance for tasks such as digit recognition and classification of electrocardiogram heartbeat activity. Using our reconfigurable artificial neurons and synapses, simulated dynamic networks outperformed static networks for incremental learning scenarios. The ability to fashion the building blocks of brain-inspired computers on demand opens up new directions in adaptive networks.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Surface Functionalized Barium Titanate Nanoparticles: A Combined Experimental and Computational Study

Barium titanate (BTO) nanoparticles show great potential for use in electrostatic capacitors with high energy density. This includes both polymer composite and sintered capacitors. However, questions about the nanoparticles' size distribution, amount of agglomeration, and surface ligand effect on performance properties remain. Reducing particle agglomeration is a crucial step to understanding the properties of nanoscale particles, as agglomeration has significant effects on the composite dielectric constant. BTO surface functionalization using phosphonic acids is known reduce BTO nanoparticle agglomeration. We explore solution synthesized 10 nm BTO particles with tert-butylphosphonic acid ligands. Recent methods to quantifying agglomeration using an epoxy matrix before imaging shows that tert-butylphosphonic acid ligands reduce BTO agglomeration by 33%. Thermometric, spectroscopic, and computational methods provide confirmation of ligand binding and provide evidence of multiple ligand binding modes on the BTO particle surface.

36 MATERIALS SCIENCE↗
DOE OSTI2024

2D material platform for overcoming the amplitude–phase tradeoff in ring resonators

Compact and high-speed electro-optic phase modulators play a vital role in various large-scale applications including optical computing, quantum and neural networks, and optical communication links. Conventional electro-refractive phase modulators such as silicon (Si), III-V and graphene on Si suffer from a fundamental tradeoff between device length and optical loss that limits their scaling capabilities. High-finesse ring resonators have been traditionally used as compact intensity modulators, but their use for phase modulation has been limited due to the high insertion loss associated with the phase shift. Here, we show that high-finesse resonators can achieve a strong phase shift with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent, i.e., Δ n Δ k ∼1. To implement this strategy, we demonstrate an active hybrid platform that combines a low-loss SiN ring resonator with 2D materials such as graphene and transition metal dichalcogenide [tungsten disulphide (WSe 2 )], which induces a strong change in the imaginary and real parts of the index. Our platform consisting of a 25 µm long Gr-Al 2 O 3 -WSe 2 capacitor embedded on a SiN ring of 50 µm radius (∼8% ring coverage) achieves a continuous phase shift of (0.46±0.05) π radians with an insertion loss (IL) of 3.18±0.20 dB and a transmission modulation (Δ T Ring ) of 1.72±0.15dB at a probe wavelength ( λ p ) of 1646.18 nm. We find that our Gr-Al 2 O 3 -WSe 2 capacitor exhibits a phase modulation efficiency ( V π 2 ⋅ L ) of 0.530±0.016V⋅cm and can support an electro-optic bandwidth of 14.9±0.1GHz. We further show that our platform can achieve a phase shift of π radians with an IL of 5 dB and a minimum Δ T of 0.046 dB. We demonstrate the broadband nature of the binary phase response, by measuring a phase shift of (1.00±0.10) π radians, with an IL of 5.20±0.31dB and a minimal Δ T Ring of 0.015±0.006dB for resonances spanning from 1564 to 1650 nm. This SiN–2D hybrid platform provides the design for compact and high-speed reconfigurable circuits with graphene and transition metal dichalcogenide (TMD) monolayers that can enable large-scale photonic systems.

Datta, Ipshita (ORCID:0000000318842882)↗
DOE OSTI2022

Investigating the dielectric constant of barium titanate in a polymer-matrix nanocomposite

Barium titanate (BTO) is a ferroelectric material used in capacitors because of its high bulk dielectric constant. However, the impact of the size of BTO on its dielectric constant is not yet fully understood and is highly contested. Here, we present an investigation into the dielectric constant of BTO nanoparticles with diameters ranging between 50 and 500 nm. BTO nanoparticles were incorporated into acrylonitrile butadiene styrene and injection molded into parallel plate capacitors, which were used to determine nanocomposite dielectric constants. The dielectric constants of BTO nanoparticles were obtained by combining experimental measurements with computational results from COMSOL simulations of ABS-matrix nanocomposites containing BTO. The dielectric constant of BTO was observed to be relatively constant at nanoparticle diameters as small as 200 nm but sharply declined at smaller nanoparticle sizes. Overall, these results will be useful in the development of improved energy storage and power conditioning systems utilizing BTO nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Photovoltaic Impact Assessment of Smart Inverter Volt-VAR Control on Distribution System Conservation Voltage Reduction and Power Quality

This report presents an impact assessment study of distributed photovoltaic (PV) with smart inverter Volt-VAR control on conservation voltage reduction (CVR) energy savings and distribution system power quality. CVR is a methodology of flattening and lowering a distribution system voltage profile in order to conserve energy. Traditional CVR relies on operating utility voltage regulators and switched capacitors. However, with the increased penetration of distributed PV systems, smart inverters provide the new opportunity to control local voltage and power factor by regulating the reactive power output, leading to a potential increase in CVR energy savings. This report proposes a methodology to implement CVR scheme by operating voltage regulators, capacitors, and autonomous smart inverter Volt-VAR control in order to achieve increased CVR benefit. Power quality is an important consideration when operating a distribution system, especially when implementing CVR. It is easy to measure the individual components that make up power quality, but a comprehensive method to incorporate all of these values into a single score has yet to be undertaken. As a result, this report proposes a power quality scoring mechanism to measure the relative power quality of distribution systems using a single number, which is aptly named the 'power quality score' (PQS). Both the CVR and PQS methodologies were applied to two distribution system models, one obtained from the Hawaiian Electric Company (HECO) and another obtained from Pacific Gas and Electric (PG&E). These two models were converted to the OpenDSS platform using previous model conversion tools that were developed by NREL. Multiple scenarios including various PV penetration levels and smart inverter densities were simulated to analyze the impact of smart inverter Volt-VAR support on CVR energy savings and feeder power quality. In order to analyze the CVR benefit and PQS, an annual simulation was conducted for each scenario.

14 SOLAR ENERGY↗
DOE OSTI2017

A Disruptive Approach to Electric Vehicle Power Electronics Final Report

This project developed and demonstrated a new power electronics technology for electric vehicle drivetrains, that achieved significant improvements in power density and efficiency over standard drive cycles, relative to the commercial state of the art. In particular, the prototype measured loss and efficiency curves demonstrated a reduction in total loss over the US EPA US06 drive cycle by a factor of four. Similar reductions are observed for urban (UDDS) and highway (HWFET) drive cycles. Further, the project demonstrated a significant reduction in the total film capacitor requirements, by over an order of magnitude; this was achieved through fundamental improvements in converter circuit topologies. These nonincremental technology advances can lead to significant improvements in temperature rise, reliability, cost, and cooling system size and weight. These results were achieved through a new proposed composite converter architecture, and were demonstrated in a boost-type system similar to that employed by Toyota, Ford, and Honda. A 30 kW silicon prototype achieved a US06 average efficiency of 97.5%, which represents a reduction in average loss by a factor of approximately four relative to the 92.5% average efficiency of the commercial state of the art. A silicon carbide prototype achieved similar efficiency, while also achieving power densities of 23 kW/L (volumetric) and 20 kW/kg (gravimetric) in a boost dc-dc system including magnetics and film capacitors. This was achieved with a SiC switching frequency of 240 kHz, which allowed employment of planar magnetics. These power densities are roughly four times better than the commercial state of the art, and significantly exceed the DOE APEEM 2020 goals. In addition to the composite boost system, a SiC inverter was demonstrated at the 800 V 30 kW level. This inverter was demonstrated driving a permanent magnet machine over the US 06 drive cycle. The replacement of 1200 V Si IGBTs with 1200 V SiC MOSFETs led to improvement of CAFE average efficiency from 98.7% to 99.5%, which corresponds to a reduction of average loss by a factor of approximately two. The modular nature of the composite converter architecture opens the possibility of reuse of one or more converter modules during charging operations, providing a path for onboard charging capability at significant power levels while significantly reducing the volume and weight of the added charger module. This project demonstrated an integrated Level II charger whose add-on specific weight was approximately four times better than the DOE PHEV charger 2022 targets.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

(U) Pre-shot Report: Complex Loading of CeO 2 Powder

A cylindrically converging shock compaction experiment is designed utilizing the Precision High Energy-density Liner Implosion eXperiment (PHELIX) platform to dynamically load CeO 2 powder. Parametric analyses investigating the effect of PHELIX cassette geometry, PHELIX total capacitor charge, and powder compaction model on the predicted shocked density profile of the CeO 2 powder are performed using the LANL codes FLAG and RAVEN. One PHELIX cassette geometry is designed to be used in two compaction experiments using PHELIX capacitor charges of 85 and 90 kV. Predictions of the shocked density profile in the CeO 2 powder are presented for each experimental configuration using both the Ramp and P-α compaction models. The two compaction models predict shocked density profiles in the CeO 2 powder that are significantly different and should be distinguishable using proton radiography as a diagnostic.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Optimization of Isentropic Compression Loads on Current-Adder Pulsed Power Accelerator Architectures

The Thor pulsed power generator is being developed at Sandia National Laboratories. The design consists of up to 288 decoupled and transit time isolated capacitor-switch units, called “bricks”, that can be individually triggered to achieve a high degree of pulse tailoring for magnetically-driven isentropic compression experiments (ICE). The connecting transmission lines are impedance matched to the bricks, allowing the capacitor energy to be efficiently delivered to an ICE strip-line load with peak pressures of over 100 GPa. Thor will drive experiments to explore equation of state, material strength, and phase transition properties of a wide variety of materials. We present an optimization process for producing tailored current pulses, a requirement for many material studies, on the Thor generator. This technique, which is unique to the novel “current-adder” architecture used by Thor, entirely avoids the iterative use of complex circuit models to converge to the desired electrical pulse. We describe the optimization procedure for the Thor design and show results for various materials of interest. Also, we discuss the extension of these concepts to the megajoule-class Neptune machine design. Given this design, we are able to design shockless ramp-driven experiments in the 1 TPa range of material pressure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

DARHT Axis 1 Time-Resolved Injector Energy Measurement

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility provides flash radiography capabilities using electron Linear Induction Accelerators (LIA’s). The strict requirements for flash radiography require a detailed understanding of the LIA’s performance, including precision measurements of the injected electron beam energy. The DARHT Axis 1 injector of produces a 3-4 MeV, 1-2 kA, 80-ns-FWHM electron beam. Injector capacitive monitors (EVACSUM) are summed to give the injector beam energy. Calibration of EVACSUM was last done in 1999 and is needed. In addition, the flatness of the injector drive voltage is controlled by a peaking capacitor in a Blumlien that is charged by the prime power tank. Time resolved measurements are used to optimize the value of this capacitor.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Optimization of DARHT Axis 1 Injector Voltage

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility provides flash radiography capabilities using two electron Linear Induction Accelerators (LIA’s). Axis-1 of DARHT produces a 20- MeV, 2-kA, 80-ns-FWHM electron beam. The strict requirements for flash radiography require a detailed understanding of the LIA’s performance, including precision measurements of the injector electron beam energy. The technique for time resolved measurement of the electron beam energy using electron Permanent Magnet Spectrometer (ePMSpec) has been developed. The electron energy then is used to infer the voltage produced by the injector pulsed power. The injector pulsed power of DARHT I consists of a 1.5-MV, glycol-insulated Blumlein that is pulsecharged by a step-up transformer and switched by four, laser-triggered spark gaps. A series of increasing impedance transmission lines are used to transform the output voltage of the Blumlein to a maximum of 3.8MV at the diode. Figure 1a shows a graphic of the Axis-1 prime power tank, Blumlein and downstream transmission lines. The injector pulse power is designed to produce voltage on a velvet cathode located in the vacuum vessel. The specifications of the voltage-pulse flat-top over 60ns is +/-1%. A key element in the high-voltage circuit is the ethylene glycol Blumlein. The outer volume, adjacent to the laser triggered switches of the Blumlein, is a peaking capacitor. This is an independent volume that contains a mixture of ethylene glycol and water to make it an adjustable capacitor of 380 to 750 pF.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Measurements of the Dielectric Properties of Thin High-Explosive Samples Using a Parallel Plate Test Fixture

This report presents results of a study of the dielectric properties of several high explosive materials, including Composition B, C-4, Detasheet, Semtex 1A, Semtex 1H, and Semtex 10. The capacitance and dispersion of samples up to ten mm thick were measured at 24 and 65°C using a parallel plate test fixture. In this configuration, capacitance is proportional to the real component of the complex dielectric constant (or permittivity) of the material, while the dispersion is equal to the imaginary component of the dielectric constant divided by the real component. Measurements were performed at two temperatures to determine whether these dielectric properties might be used to monitor moderate temperature changes within these materials using an external fringing field capacitor. It was found that the real dielectric constant of the high explosives generally changed by only about 1% on heating from 24 to 65°C, and that the externally measured capacitance is therefore not a reliable parameter for monitoring temperature changes in these explosives. Temperature- based changes in the dispersion were often 20% or greater, and for several materials (e.g., Composition B, Detasheet) the temperature and dispersion showed good correlation as the temperature of the explosive was cycled up and down. It is thus possible that for some high explosives the externally measured dispersion is a useful parameter for monitoring temperature changes. However, other factors may limit the usefulness of this technique, including the need to have the plates of a fringing field capacitor in direct contact with the high explosive to obtain measurements, and the limited penetration depth of the fringing field into the explosive material.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Component Modeling, Co-Optimization, and Trade-Space Evaluation (FY2021 Annual Progress Report)

This project is intended to support the development of new traction drive systems that meet the targets of 100 kW/L for power electronics and 50 kW/L for electric machines with reliable operation to 300,000 miles. To meet these goals, new designs must be identified that make use of state-of-the-art and next-generation electronic materials and design methods. Designs must exploit synergies between components, for example converters designed for high-frequency switching using wide band gap devices and ceramic capacitors. This project includes: (1) a survey of available technologies; (2) the development of design tools that consider the converter volume and performance; (3) exercising the design software to evaluate performance gaps and predict the impact of certain technologies and design approaches, i.e. GaN semiconductors, ceramic capacitors, and select topologies; and (4) building and testing hardware prototypes to validate models and concepts. Early instantiations of the design tools enable co-optimization of the power module and passive elements and provide some design guidance; later instantiations will enable the co-optimization of inverter and machine. Prototype testing begins with evaluation of simpler conversion topologies (i.e. the half-bridge boost converter) and progresses with fabrication of prototype inverter drives.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2022

K-Modules: Capacitive Energy Modules for Pulsed Power Applications [Slides]

K-Modules are modules containing an assembly of capacitors. The modules are meant to be daisy-chained to form a Marx bank (bank of capacitors). Discharging the bank produces a high voltage, high current pulse, that when coupled to an X-ray or electron beam tube, generates X-rays or an intense electron beam. Number of modules in the stack can be varied to meet different pulsed power applications. The technology addresses the need for an alternate provider with a new, robust design. The technology has the potential to extend the life of the X-ray radiography program in the country.

43 PARTICLE ACCELERATORS↗