Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “device”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Growth Optimization and Device Integration of Narrow‐Bandgap Graphene Nanoribbons

Abstract The electronic, optical, and magnetic properties of graphene nanoribbons (GNRs) can be engineered by controlling their edge structure and width with atomic precision through bottom‐up fabrication based on molecular precursors. This approach offers a unique platform for all‐carbon electronic devices but requires careful optimization of the growth conditions to match structural requirements for successful device integration, with GNR length being the most critical parameter. In this work, the growth, characterization, and device integration of 5‐atom wide armchair GNRs (5‐AGNRs) are studied, which are expected to have an optimal bandgap as active material in switching devices. 5‐AGNRs are obtained via on‐surface synthesis under ultrahigh vacuum conditions from Br‐ and I‐substituted precursors. It is shown that the use of I‐substituted precursors and the optimization of the initial precursor coverage quintupled the average 5‐AGNR length. This significant length increase allowed the integration of 5‐AGNRs into devices and the realization of the first field‐effect transistor based on narrow bandgap AGNRs that shows switching behavior at room temperature. The study highlights that the optimized growth protocols can successfully bridge between the sub‐nanometer scale, where atomic precision is needed to control the electronic properties, and the scale of tens of nanometers relevant for successful device integration of GNRs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Performance Assessment of Several Low-Cost Consumer-Grade Analog-to-Digital Conversion Devices

The Oak Ridge National Laboratory (ORNL) has pioneered an approach where low-cost consumer-grade electronics can be used as the basis of a highly reliable data acquisition architecture. One twenty-channel system based on this approach has been operating almost 4 years at ORNL. The architecture allows a mix-and-match level of configurability so the designer can select devices that best match the desired performance trade-offs. The most important device to be selected is the analog-to-digital converter. This paper explores the performance of several candidate audio recording devices that can be used as high-speed analog-to-digital converters for such measurement systems. Various performance metrics are explored including frequency response, noise floor, and synchronous sampling. Sample rates as high as 192 KHz are supported with 16 and 24-bit resolution. While most of the devices are dual-channel, there are multi-channel devices now available that will allow modal type of synchronous sampling. One such device was tested and is discussed is this paper.

Wetherington Jr, G↗
DOE OSTI2018

MR Imaging of Patients with Cardiac Implantable Electronic Devices (CIEDs): Implementing a Program and Optimizing CMR

Purpose of review: How to implement a program for MRI in patients with conditional and non-conditional (“legacy”) CIED. How to optimize safety and image quality in CMR? What the radiologists need to know: device programming, pre- and post-MRI CIED parameters. Recent findings: New Center for Medicare and Medicaid Services (CMS) guidelines have opened MRI to many patients with nonconditional devices. Newer pulse sequences for cardiac MRI (CMR) in device patients, including modified cine, late gadolinium enhancement and T1 mapping sequences, have resulted in improved image quality in device patients. We present several cases of CMR in device patients, including imaging of leadless pacemakers subcutaneous ICDs. Imaging pitfalls/artifacts in CMR interpretation are also presented. Summary: An organized institutional workflow with an established protocol involving proper patient screening, device programming, scan monitoring, and pre- and post-ICD interrogation minimizes risk in patients with conditional and non-conditional CIEDs. Although rare, significant changes in lead performance, power-on/reset, inappropriate pacing or ICD discharges and battery voltage depletion should be documented. High-quality scans with accurate scar characterization in CIED patients require the use of wideband sequences. CMS has recently acknowledged MRI as a reasonable test necessary for the diagnosis and treatment of beneficiaries with implanted CIEDs, improving the financial prospects and encouraging future developments.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Persistent energy harvesting in the harsh desert environment using a thermal resonance device: Design, testing, and analysis

Thermal fluctuations in the environment are a ubiquitous, yet untapped energy source for harvesting. Our laboratory has introduced the concept of a thermal resonance device for this purpose, with potential to power wireless sensor networks (WSNs), devices embedded into structural elements, and electronics deployed in relatively inaccessible areas. This approach has particular advantages for the desert environment, where conventional energy harvesting devices are severely confounded by frequent sandstorms, extreme temperature and high solar fluence. Herein, we design, fabricate, and test a thermal resonator for the conversion of diurnal temperature fluctuations to electrical power in a harsh desert environment using a thermally conductive phase change composite as a high thermal effusivity material, specifically tuned to the temperature fluctuating environment of Thuwal, Saudi Arabia (22.3095°N, 39.1047°E). The composite consists of a highly porous and thermally conductive nickel foam impregnated with eicosane as a phase change material for enhanced thermal capacity. The high thermal effusivity material is incorporated into a rationally-designed thermal resonance device, which is tested for a period of two weeks in Saudi Arabia, extracting as high as 2 mW from approximately 10 °C diurnal temperature fluctuations. These experimental data provide a test of the theoretical model for the design and operation of the device. Overall, these results highlight the opportunity of employing thermal resonance devices for energy harvesting, particularly in the desert environment.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Device-level plug load disaggregation in a zero energy office building and opportunities for energy savings

Along with heating, cooling, ventilation, and lighting, plug loads are one of the principal consumers of energy in commercial buildings. Managing ever-changing plug loads is a great challenge given the quantity and variety of devices in commercial buildings and the cost of monitoring equipment. To address this issue, we propose a method for developing a disaggregated model of an office building's plug loads that utilizes power data from a small portion of monitored devices and a device inventory. Using data from metering and control devices in the Research Support Facility at the National Renewable Energy Laboratory, we compared our model to the building's plug load submeters. We found that the model was effective in predicting the shape of the building's average plug loads; however, it did not account for the entire magnitude of the load. With the disaggregated breakdown, we identified devices that contributed significantly to the building's unoccupied load, such as the audio visual equipment as well as devices that contributed significantly at specific times of the day, such as the microwaves at noon. This disaggregated information enables building owners to make more informed decisions with respect to plug load controls and energy efficiency upgrades. Furthermore, we highlight how the plug loads in the Research Support Facility have changed over time and offer recommendations for implementing this disaggregation method in other buildings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Measuring the maximum capacity and thermal resistances in phase-change thermal storage devices

Thermal energy storage can increase the efficiency of the electric grid by adding flexibility to thermal systems. The value of thermal storage is a function of its energy and power density, which are driven by the capacity and thermal resistances in the storage device. Measuring these properties in-situ at the device level is an important step to understanding the performance and improving the design of thermal storage systems. Here, we present methods to measure the total capacity and thermal resistances in heat exchangers with integrated phase change materials. These methods are demonstrated on two thermal storage devices - a 570-kWh ice-based storage tank and a 0.35-kWh graphite-tetradecane composite device. The results show how thermal resistances evolve with the state of charge and discharge rate in these devices and quantify the impact of applied pressure on the contact resistance in composite phase change material heat exchangers. The proposed method allows for easy comparison between different systems and provides information on the thermal bottlenecks limiting performance. Ultimately, these measurements will allow designers to make robust, high-performance thermal storage devices for next-generation thermal systems.

25 ENERGY STORAGE↗
DOE OSTI2014

A light-modified ferroelectric resistive switching behavior in Ag/BaMoO{sub 4}/FTO device at ambient temperature

BaMoO{sub 4} powder was prepared by a facile hydrothermal synthesis. And the BaMoO{sub 4}/FTO device was fabricated by a spin-coated method, in which the thickness of BaMoO{sub 4} layer is about 20 µm. The bipolar resistive switching effect has been observed in Ag/BaMoO{sub 4}/FTO device. Moreover, the resistive switching effect of the device is greatly improved by white light irradiation. The resistive switching behavior is explained by the polarization reversal that changes the charge distribution and modulates the Schottky barriers. - Graphical abstract: We fabricate a resistive switching device based on Ag/BaMoO{sub 4}/FTO, the device shows superior white-light controlled bipolar resistive switching memristive characteristics. - Highlights: • The BaMoO{sub 4} nanosquares powder was prepared by a hydrothermal synthesis. • The resistive switching of the Ag/BaMoO{sub 4}/FTO device was observed for the first time. • It is shown that the resistive switching is greatly improved under the white light irradiation. • The mechanism of resistive switching is attributed to the ferroelectric polarization reversal.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Quantum filter of spin polarized states: Metal–dielectric–ferromagnetic/semiconductor device

Highlights: • Development of a new spintronics device. • Development of quantum spin polarized filters. • Development of theory of quantum spin polarized filter. - Abstract: Recently we proposed a model for the Quantum Spin-Polarized State Filter (QSPSF). The magnetic moments are transported selectively in this model, detached from the electric charge carriers. Thus, transfer of a spin-polarized state between two conductors was predicted in a system of two levels coupled by exchange interaction. The strength of the exchange interaction between the two conductive layers depends on the thickness of the dielectric layer separating them. External magnetic fields modulate spin-polarized state transfer, due to Zeeman level shift. Therefore, a linearly growing magnetic field generates a series of current peaks in a nearby coil. Thus, our spin-state filter should contain as least three nanolayers: (1) conductive or ferromagnetic; (2) dielectric; and (3) conductive or semiconductive. The spectrum of spin-polarized states generated by the filter device consists of a series of resonance peaks. In a simple case the number of lines equals S, the total spin angular momentum of discrete states in one of the coupled nanolayers. Presently we report spin-polarized state transport in metal–dielectric–ferromagnetic (MDF) and metal–dielectric–semiconductor (MDS) three-layer sandwich devices. The exchange-resonance spectra in such devices are quite specific, differing also from spectra observed earlier in other three-layer devices. The theoretical model is used to interpret the available experimental results. A detailed ab initio analysis of the magnetic-field dependence of the output magnetic moment averaged over the surface of the device was carried out. The model predicts the resonance structure of the signal, although at its present accuracy it cannot predict the positions of the spectral peaks.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Enabling bifacial thin film devices by developing a back surface field using Cu x AlO y

Bifacial solar cells have the potential to increase the energy yield per unit area over traditional monofacial devices without significant added cost, driving $/kWh costs lower and accelerating the adoption of solar photovoltaics. However, the performance of bifacial thin film solar cells significantly lags that achieved by crystalline silicon cells. Here we incorporate wide bandgap Cu x AlO y as a back buffer layer for CdTe devices and achieve a backside illuminated device with high current density and high fill factor. Moreover, these values remain nearly constant even as the absorber layer thickness changes, indicating that a fully-depleted device is not required for efficient charge collection. We show that this response is indicative of a back surface field, albeit with a persistent high back surface recombination velocity. By managing electron reflection, we achieved a backside illumination conversion efficiency of 7.1% and bifaciality of 0.55 for a 3.3 µm CdTe device and 8.0% and 0.62 for a 2 µm device. Future improvements can be made by identifying and incorporating a passivation material that reduces the back surface recombination velocity.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Improved performance of a near-field thermophotovoltaic device by a back gapped reflector

Various spectral control techniques can be applied to improve the performance of a thermophotovoltaic (TPV) device. For example, a back surface reflector (BSR) is a common structure to improve the performance of TPV devices. A conventional metal BSR structure enhances the photogeneration rate by increasing the absorption probability of photons via back surface reflections, affording a second chance for absorption. However, the effects of surface passivation and external luminescence introduced by BSR structures have been previously ignored, which potentially decreases the performance of TPV devices. Recently, a back gapped reflector (BGR) structure was proposed to greatly improve the performance of far-field TPV devices by reducing imperfect reflections at the semiconductor-metal interface. In the present work, the performance improvement on a thin-film, near-field InAs TPV device with a BGR is investigated, comparing its performance to that with a conventional metal BSR. Surface passivation conditions are also investigated to further improve the performance of TPV devices with back reflectors. Further, the output power and efficiency are calculated using an iterative model combining fluctuational electrodynamics and the full drift diffusion model. For the well-passivated condition, when the BSR is replaced by the BGR, the calculated conversion efficiency of the near-field TPV was improved from 16.4% to 21% and the output power was increased by 10%. Finally, the absorption of the back reflectors and external luminescence loss are analyzed to explain the performance improvement.

external luminescence↗
DOE OSTI2018

Nanocellulose toward Advanced Energy Storage Devices: Structure and Electrochemistry

We report that cellulose is the most abundant biopolymer on Earth and has long been used as a sustainable building block of conventional paper. Note that nanocellulose accounts for nearly 40% of wood’s weight and can be extracted using well-developed methods. Due to its appealing mechanical and electrochemical properties, including high specific modulus (~100 GPa/(g/cm 3 )), excellent stability in most solvents, and stability over a wide electrochemical window, nanocellulose has been widely used as a separator, electrolyte, binder, and substrate material for energy storage. Additionally, nanocellulose-derived carbon materials have also drawn increasing scientific interest in sustainable energy storage due to their low-cost and raw-material abundance, high conductivity, and rational electrochemical performance. The inexpensive and environmentally friendly nature of nanocellulose and its derivatives as well as simple fabrication techniques make nanocellulose-based energy storage devices promising candidates for the future of “green” and renewable electronics. For nanocellulose-based energy storage, structure engineering and design play a vital role in achieving desired electrochemical properties and performances. Thus, it is important to identify suitable structure and design engineering strategies and to better understand their relationship. In this Account, we review recent developments in nanocellulose-based energy storage. Due to the limited space, we will mainly focus on structure design and engineering strategies in macrofiber, paper, and three-dimensional (3D) structured electrochemical energy storage (EES) devices and highlight progress made in our group. We first present the structure and properties of nanocellulose, with a particular discussion of nanocellulose from wood materials. We then go on to discuss studies on nanocellulose-based macrofiber, paper, and 3D wood- and other aerogel-based EES devices. Within this discussion, we highlight the use of natural nanocellulose as a flexible substrate for a macrofiber supercapacitor and an excellent electrolyte reservoir for a breathable textile lithium–oxygen battery. Paper batteries and supercapacitors using nanocellulose as a green dispersant, nanocellulose-based paper as a flexible substrate, and nanocellulose as separator and electrolyte are also examined. We highlight recent progress on wood-based batteries and supercapacitors, focusing on the advantages of wood materials for energy storage, the structure design and engineering strategies, and their microstructure and electrochemical properties. We discuss the influence of structure (particularly pores) on the electrochemical performance of the energy storage devices. By taking advantage of the straight, nature-made channels in wood materials, ultrathick, highly loaded, and low-tortuosity energy storage devices are demonstrated. Lastly, we offer concluding remarks on the challenges and directions of future research in the field of nanocellulose-based energy storage devices.

25 ENERGY STORAGE↗
DOE OSTI2018

Interplay between Ion Transport, Applied Bias, and Degradation under Illumination in Hybrid Perovskite p-i-n Devices

In this work, we studied ion transport in hybrid organic–inorganic perovskite p-i-n devices as a function of applied bias under device operating conditions. Using electrochemical impedance spectroscopy (EIS) and equivalent circuit modeling, we elucidated various resistive and capacitive elements in the device. We show that ion migration is predictably influenced by a low applied forward bias, characterized by an increased capacitance at the hole-transporting (HTM) and electron-transporting material (ETM) interfaces, as well as in bulk. However, unlike observations in n-i-p devices, we found that there is a capacitive discharge leading to ion redistribution in the bulk at high forward biases. Furthermore, we show that a chemical double-layer capacitance buildup as a result of ion accumulation impacts the electronic properties of the device, likely by inducing either charge pinning or charge screening, depending on the direction of the ion-induced field. Finally, we extrapolate ion diffusion coefficients (~10 –7 cm 2 s –1 ) and ionic conductivities (~10 –7 S cm –1 ) from the Warburg mass (ion) diffusion response and show that, as the device degrades, there is an overall depletion of capacitive effects coupled with increased ion mobility.

36 MATERIALS SCIENCE↗
DOE OSTI2025

High-resolution high-throughput spatiotemporal strain imaging reveals loss mechanisms in a surface acoustic wave device

Surface acoustic wave devices are key components for processing radio frequency signals in wireless communication because these devices offer simultaneously high performance, compact size and low cost. The optimization of the device structure requires a quantitative understanding of energy conversion and loss mechanisms. Here we use stroboscopic full-field diffraction x-ray microscopy to reveal an unanticipated acoustic loss in a prototypical one-port resonator device. A non-uniform acoustic excitation in the active area was responsible for the substantial end and side leakages observed at the design frequency. Quantitative analysis of the strain amplitude using a wave decomposition method allowed the determination of several key device parameters. This high-resolution high-throughput spatiotemporal strain imaging technique is more generally applicable to the study of dynamic strain modulation in nanoscale acoustic, electronic, optical and quantum devices. The high sensitivity allows precise measurement of the strain modulation with picometer-scale amplitude.

Zhou, Tao [ESRF - The European Synchrotron, Grenob↗
DOE OSTI2025

Integration of multiple coinflip devices for high-quality random sampling

Artificial intelligence, scientific computing, and probabilistic computing use random sampling to approximate solutions to various problems, with larger models requiring a substantial quantity of random numbers. To generate the required vast quantity of random numbers at high rates, we explore so-called “coinflip” devices, which are stochastic microelectronic devices ideally capable of independently generating random bits with a tunable weight at a high rate. However, coinflip devices are inherently analog and demonstrate nonidealities, like temperature dependence and drift, that can introduce determinism into the outputs. We present important considerations for building systems of multiple coinflip devices to produce high-quality bitstreams with low error and little dependency on previous bits. Using tunnel diodes as coinflip devices, we implement a control loop to adapt to temperature dependence and generate fair bitstreams with each device. While this can lead to dependencies between bits in a single bitstream, we demonstrate that combining results generated in parallel with individual tunnel diodes can produce fair and unpredictable bitstreams. The suitability of these bitstreams for use in probabilistic computing is then demonstrated through a Monte Carlo approximation of π.

Taylor, Brady Garland [Sandia National Laboratorie↗
DOE OSTI2016

Design, fabrication and test of a pneumatically controlled, renewable, microfluidic bead trapping device for sequential injection analysis applications

This paper describes the design, fabrication, and testing of a pneumatically controlled,renewable, microfluidic device for conducting bead-based assays in an automated sequential injection analysis system. The device used a “brick wall”-like pillar array (pillar size: 20 μm length X 50 μm width X 45 μm height) with 5 μm gaps between the pillars serving as the micro filter. The flow channel where bead trapping occurred is 500 μm wide X 75 μm deep. An elastomeric membrane and an air chamber were located underneath the flow channel. By applying pressure to the air chamber, the membrane is deformed and pushed upward against the filter structure. This effectively traps beads larger than 5 μm and creates a “bed” or micro column of beads that can be perfused and washed with liquid samples and reagents. Upon completion of the assay process, the pressure is released and the beads are flushed out from underneath the filter structure to renew the device. Mouse IgG was used as a model analyte to test the feasibility of using the proposed device for immunoassay applications. Resulting microbeads from an on-chip fluorescent immunoassay were individually examined using flow cytometry. The results show that the fluorescence signal intensity distribution is fairly narrow indicating high chemical reaction uniformity among the beads population. Electrochemical onchip assay was also conducted. A detection limit of 0.1 ng/mL1 ppb was achieved and good device reliability and repeatability were demonstrated. The novel microfluidic-based beadstrapping device thus opens up a new pathway to design micro-bead based biosensor immunoassays for clinical and othervarious applications.

beads trapping↗
DOE OSTI2016

Nano-array integrated monolithic devices: toward rational materials design and multi-functional performance by scalable nanostructures assembly

We report the scalable three-dimensional (3-D) integration of functional nanostructures into applicable platforms represents a promising technology to meet the ever-increasing demands of fabricating high performance devices featuring cost-effectiveness, structural sophistication and multi-functional enabling. Such an integration process generally involves a diverse array of nanostructural entities (nano-entities) consisting of dissimilar nanoscale building blocks such as nanoparticles, nanowires, and nanofilms made of metals, ceramics, or polymers. Various synthetic strategies and integration methods have enabled the successful assembly of both structurally and functionally tailored nano-arrays into a unique class of monolithic devices. The performance of nano-array based monolithic devices is dictated by a few important factors such as materials substrate selection, nanostructure composition and nano-architecture geometry. Therefore, the rational material selection and nano-entity manipulation during the nano-array integration process, aiming to exploit the advantageous characteristics of nanostructures and their ensembles, are critical steps towards bridging the design of nanostructure integrated monolithic devices with various practical applications. In this article, we highlight the latest research progress of the two-dimensional (2-D) and 3-D metal and metal oxide based nanostructural integrations into prototype devices applicable with ultrahigh efficiency, good robustness and improved functionality. Lastly, selective examples of nano-array integration, scalable nanomanufacturing and representative monolithic devices such as catalytic converters, sensors and batteries will be utilized as the connecting dots to display a roadmap from hierarchical nanostructural assembly to practical nanotechnology implications ranging from energy, environmental, to chemical and biotechnology areas.

36 MATERIALS SCIENCE↗
DOE OSTI2014

A novel in situ device based on a bionic piezoelectric actuator to study tensile and fatigue properties of bulk materials

In this work, a miniaturized device based on a bionic piezoelectric actuator was developed to investigate the static tensile and dynamic fatigue properties of bulk materials. The device mainly consists of a bionic stepping piezoelectric actuator based on wedge block clamping, a pair of grippers, and a set of precise signal test system. Tensile and fatigue examinations share a set of driving system and a set of signal test system. In situ tensile and fatigue examinations under scanning electron microscope or metallographic microscope could be carried out due to the miniaturized dimensions of the device. The structure and working principle of the device were discussed and the effects of output difference between two piezoelectric stacks on the device were theoretically analyzed. The tensile and fatigue examinations on ordinary copper were carried out using this device and its feasibility was verified through the comparison tests with a commercial tensile examination instrument.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High performance AlScN thin film based surface acoustic wave devices with large electromechanical coupling coefficient

AlN and AlScN thin films with 27% scandium (Sc) were synthesized by DC magnetron sputtering deposition and used to fabricate surface acoustic wave (SAW) devices. Compared with AlN-based devices, the AlScN SAW devices exhibit much better transmission properties. Scandium doping results in electromechanical coupling coefficient, K{sup 2}, in the range of 2.0% ∼ 2.2% for a wide normalized thickness range, more than a 300% increase compared to that of AlN-based SAW devices, thus demonstrating the potential applications of AlScN in high frequency resonators, sensors, and high efficiency energy harvesting devices. The coupling coefficients of the present AlScN based SAW devices are much higher than that of the theoretical calculation based on some assumptions for AlScN piezoelectric material properties, implying there is a need for in-depth investigations on the material properties of AlScN.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗