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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Subscale Water Based Phase Change Material Heat Exchanger Development

Supplemental heat rejection devices are required in many spacecraft as the radiators are not sized to meet the full heat rejection demand. One means of obtaining additional heat rejection is through the use of phase change material heat exchangers (PCM HX's). PCM HX's utilize phase change to store energy in unfavorable thermal environments (melting) and reject the energy in favorable environments (freezing). Traditionally, wax has been used as a PCM on spacecraft. However, water is an attractive alternative because it is capable of storing about 40% more energy per unit mass due to its higher latent heat of fusion. The significant problem in using water as a PCM is its expansion while freezing, leading to structural integrity concerns when housed in an enclosed heat exchanger volume. Significant investigation and development has taken place over the past five years to understand and overcome the problems associated with water PCM HX's. This paper reports on the final efforts by Johnson Space Center's Thermal Systems Branch to develop a water based PCM HX. The test article developed and reported on is a subscale version of the full-scale water-based PCM HX's constructed by Mezzo Technologies. The subscale unit was designed by applying prior research on freeze front propagation and previous full-scale water PCM HX development. Design modifications to the subscale unit included use of urethane bladder, decreased aspect ratio, perforated protection sheet, and use of additional mid-plates. Testing of the subscale unit was successful and 150 cycles were completed without fail.

Sheth, Rubik↗
NASA NTRS2001

Active Control Technology at NASA Langley Research Center

NASA Langley has a long history of attacking important technical opportunities from a broad base of supporting disciplines. The research and development at Langley in this subject area range from the test tube to the test flight. The information covered here will range from the development of innovative new materials, sensors and actuators, to the incorporation of smart sensors and actuators in practical devices, to the optimization of the location of these devices, to, finally, a wide variety of applications of these devices utilizing Langley's facilities and expertise. Advanced materials are being developed for sensors and actuators, as well as polymers for integrating smart devices into composite structures. Contributions reside in three key areas: (1) computational materials; (2) advanced piezoelectric materials; and (3) integrated composite structures.

Antcliff, Richard R.↗
NASA NTRS2000

Method of Controlling Lasing Wavelength(s)

A method is provided to control the lasing wavelength of a laser material without changing or adjusting the mechanical components of a laser device, The rate at which the laser material is pumped with the pumping energy is controlled so that lasing occurs at one or more lasing wavelengths based on the rate. The lasing wavelengths are determined by transition lifetimes and/or energy transfer rates.

Norman P Barnes↗
NASA NTRS2006

Temperature-dependent Refractive Index of Silicon and Germanium

Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

Frey, Bradley J.↗
DOE OSTI2023

Optically Excited Lasing in a Cavity‐Based, High‐Current‐Density Quantum Dot Electroluminescent Device

Abstract Laser diodes based on solution‐processable materials can benefit numerous technologies including integrated electronics and photonics, telecommunications, and medical diagnostics. An attractive system for implementing these devices is colloidal semiconductor quantum dots (QDs). The progress towards a QD laser diode has been hampered by rapid nonradiative Auger decay of optical‐gain‐active multicarrier states, fast device degradation at high current densities required for laser action, and unfavorable competition between optical gain and optical losses in a multicomponent device stack. Here we resolve some of these challenges and demonstrate optically excited lasing from fully functional high‐current density electroluminescent (EL) devices with an integrated optical resonator. This advance has become possible due to excellent optical gain properties of continuously graded QDs and a refined device architecture, which allows for highly efficient light amplification in a thin, EL‐active QD layer.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Manipulating topological properties in Bi 2 Se 3 / BiSe /transition metal dichalcogenide heterostructures with interface charge transfer

Heterostructures of topological insulator Bi 2 Se 3 on transition metal dichalcogenides (TMDCs) offer a new materials platform for studying novel quantum states by exploiting the interplay among topological orders, charge orders and magnetic orders. Here, the diverse interface attributes, such as material combination, charge re-arrangement, defect and strain, can be utilized to manipulate the quantum properties of this class of materials. Recent experiments of Bi 2 Se 3 /NbSe 2 heterostructures show signatures of strong Rashba band splitting due to the presence of a BiSe buffer layer, but the atomic level mechanism is not fully understood. We conduct first-principles studies of the Bi 2 Se3/BiSe/TMDC heterostructures with five different TMDC substrates (1T phase VSe 2 , MoSe 2 , TiSe 2 , and 2H phase NbSe 2 , MoSe 2 ). We find significant charge transfer at both BiSe/TMDC and Bi 2 Se 3 /BiSe interfaces driven by the work function difference, which stabilizes the BiSe layer as an electron donor and creates interface dipole. The electric field of the interface dipole breaks the inversion symmetry in the Bi 2 Se 3 layer, leading to the giant Rashba band splitting in two quintuple layers and the recovery of the Dirac point in three quintuple layers, with the latter otherwise only occurring in thicker samples with at least six Bi 2 Se 3 quintuple layers. Besides, we find that strain can significantly affect the charge transfer at the interfaces. Our study presents a promising avenue for tuning topological properties in heterostructures of two-dimensional materials, with potential applications in quantum devices.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Amorphous Indium Oxide Channel FEFETs With Write Voltage of 0.9 V and Endurance >10 12 for Refresh-Free Embedded Memory

This work presents, for the first time, a back-end-of-the-line (BEOL)-compatible W-doped indium oxide (IWO) ferroelectric field-effect transistor (FEFET) with a record-low operating voltage below 0.9 V and a write speed of 20 ns while achieving a transient read current window (CW) ratio ( I LVT /I HVT ) greater than 10 4 . The device also exhibits exceptional reliability characteristics such as: 1) measured bipolar write endurance up to 10 12 cycles; 2) a fast read speed of 50 ns; 3) read endurance surpassing 10 12 cycles; and 4) retention exceeding 10 4 s at 85 ∘ C. Furthermore, a physics-based numerical model has been developed to investigate the nanoscale characteristics of BEOL FEFET devices, leveraging nucleation-limited switching in HfO 2 ferroelectrics and dc characterization to extract material and channel parameters for accurate device simulation. The simulation uncovers the stochastic switching behavior of BEOL amorphous oxide semiconductor (AOS) FEFETs and demonstrates an intrinsic switching time as low as 1 ps, highlighting the potential of BEOL AOS FEFETs for ultrafast memory applications. These results establish AOS FEFETs as a compelling candidate for high-density embedded memory applications for last-level cache (LLC) (L4) in advanced CMOS technology nodes.

1-V ferroelectric field-effect transistor (FEFET)↗
NASA NTRS2009

Filtering Water by Use of Ultrasonically Vibrated Nanotubes

Devices that could be characterized as acoustically driven molecular sieves have been proposed for filtering water to remove all biological contaminants and all molecules larger than water molecules. Originally intended for purifying wastewater for reuse aboard spacecraft, these devices could also be attractive for use on Earth in numerous settings in which there are requirements to obtain potable, medical-grade, or otherwise pure water from contaminated water supplies. These devices could also serve as efficient means of removing some or all water from chemical products . for example, they might be useful as adjuncts or substitutes for stills in the removal of water from alcohols and alcoholic beverages. These devices may be constructed using various materials, such as ceramics, metallics, or polymers, depending on end-use requirements. A representative device of this type (see figure) would include a polymeric disk, about 1 mm in diameter and between 1 and 40 microns thick, within which would be embedded single-wall carbon nanotubes aligned along the thickness axis. The polymeric disk would be part of a unitary polymeric ring assembly. An acoustic transducer in the form of a piezoelectric-film-and-electrode subassembly - typically 9 microns thick and made of poly(vinylidene fluoride) coated with copper 150 nm thick -. would be affixed to the outside of the outer polymeric ring by means of an electrically nonconductive epoxy. The nanotubes would be chosen to have diameters between about 8 and about 13.5 A because water molecules could fit into the nanotubes, but larger molecules could not. Water to be purified would be placed in contact with one face (typically, the upper face) of the filter disk. The surface tension of water is low enough that water molecules should enter and travel along the nanotubes, and computational simulations of molecular dynamics and experimental measurements have shown that the water molecules inside the nanotubes in this size range can be expected to become aligned into helical columns that exhibit properties of both hexagonal ice crystals and liquid water

Gavalas, Lillian Susan↗
DOE OSTI2023

Revealing the Latent Atomic World Through Data-Driven Microscopy

Many emerging technologies depend on the precise design of materials structure, chemistry, and defects. As devices shrink, manufacturing tolerances tighten, and performance envelopes improve, we must increasingly measure and manipulate materials at or near the single atom level. Here we describe how transmission electron microscopy (TEM) underpins our ability to see and direct the latent atomic world. We review a selection of our recent high-resolution TEM studies of the synthesis of oxide-based nanomaterials and their evolution in extreme environments. We then discuss powerful new artificial intelligence (AI) and machine learning (ML) approaches we have developed for rich, reproducible, and scalable experimentation. Furthermore, we conclude by discussing future developments that will enable new materials for breakthrough technologies.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Systems and methods for additively manufacturing caloric microstructures

A method for additively manufacturing a microstructure from a caloric material includes providing a geometry of the microstructure to a processor of an additive manufacturing device, the geometry defining a plurality of microfeatures of the microstructure. The method also includes generating, via the processor, a three-dimensional (3D) model representative of the geometry of the microstructure, wherein one or more of the plurality of microfeatures are represented in the 3D model by a non-arcuate profile. Further, the method includes printing, via the additive manufacturing device, the microstructure from the caloric material according to the 3D model. As such, the non-arcuate profile reduces a file size of the 3D model as compared to an arcuate profile.

Schroeder, Michael Goodman↗
DOE OSTI2025

Emerging applications: Neuromorphic computing and reservoir computing

The emergence of doped hafnium oxide (HfO 2 )-based ferroelectric films has enabled highly scalable and silicon-compatible ferroelectric devices, opening new frontiers in neuromorphic and reservoir computing. Among these, ferroelectric field-effect transistors (FeFETs) are particularly promising due to their analog memory characteristics and unique polarization dynamics. These properties make FeFETs ideal candidates for artificial synapses in neuromorphic architectures, supporting deep neural networks and spiking neural networks based on leaky-integrate-and-fire (LIF) mechanisms. Beyond neuromorphic computing, FeFETs also play a crucial role in physical reservoir computing, leveraging their intrinsic nonlinear and history-dependent behavior for efficient real-time learning. This approach offers significant advantages for time-series processing and edge artificial intelligence (AI) applications, addressing the growing need for energy-efficient computing. As a result, this article explores the principles, key demonstrations, and future potential of FeFET-based neuromorphic and reservoir computing, highlighting their impact on next-generation AI hardware.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Light sources with bias tunable spectrum based on van der Waals interface transistors

Light-emitting electronic devices are ubiquitous in key areas of current technology, such as data communications, solid-state lighting, displays, and optical interconnects. Controlling the spectrum of the emitted light electrically, by simply acting on the device bias conditions, is an important goal with potential technological repercussions. However, identifying a material platform enabling broad electrical tuning of the spectrum of electroluminescent devices remains challenging. Here, we propose light-emitting field-effect transistors based on van der Waals interfaces of atomically thin semiconductors as a promising class of devices to achieve this goal. We demonstrate that large spectral changes in room-temperature electroluminescence can be controlled both at the device assembly stage –by suitably selecting the material forming the interfaces– and on-chip, by changing the bias to modify the device operation point. Even though the precise relation between device bias and kinetics of the radiative transitions remains to be understood, our experiments show that the physical mechanism responsible for light emission is robust, making these devices compatible with simple large areas device production methods.

36 MATERIALS SCIENCE↗
NASA NTRS1998

The Effects of Ground and Space Processing on the Properties of Organic, Polymeric, and Colloidal Materials

In recent years, a great deal of interest has been directed toward the use of organic materials in the development of high-efficiency optoelectronic and phototonic devices. There is a myriad of possibilities among organic materials which allow flexibility in the design of unique structures with a variety of functional groups. The use of nonlinear optical (NLO) organic materials as thin film wave-guides allows full exploitation of their desirable qualifies by permitting long interaction lengths and large susceptibilities allowing modest power input. There are several methods in use to prepare thin films such as Langmuir-Blodgett (LB) and self-assembly techniques, vapor deposition, growth from sheared solution or melt, and melt growth between glass plates. Organic-based materials have many features that make them desirable for use in optical devices, such as high second-and third-order nonlinearity, flexibility of molecular design, and damage resistance to optical radiation. However, their use in devices has been hindered by processing difficulties for crystals and thin films. We discuss the potential role of microgravity processing of a few organic and polymeric materials. It is of interest to note how materials with second-and third-order NLO behavior may be improved in a diffusion-limited environment and ways in which convection may be detrimental to these materials. We focus our discussion on third-order materials for all-optical switching, and second-order materials for frequency conversion and electrooptics. The goal of minimizing optical loss obviously depends on processing methods. For solution-based processes, such as solution crystal growth and solution photopolymerization, it is well known that thermal and solutal density gradients can initiate buoyancy-driven convection. Resultant fluid flows can affect transport of material to and from growth interfaces and become manifest in the morphology and homogeneity of the growing film or crystal. Likewise, buoyancy-driven convection can hinder production of defect-free, high-quality crystals or films during crystal and film growth by vapor deposition.

Frazier, Donald O.↗
NASA NTRS2007

Ultra-Lightweight Hybrid Thin-Film Solar Cells: A Survey of Enabling Technologies for Space Power Applications

The development of hybrid inorganic/organic thin-film solar cells on flexible, lightweight, space-qualified, durable substrates provides an attractive solution for fabricating solar arrays with high mass specific power (W/kg). Next generation thin-film technologies may well involve a revolutionary change in materials to organic-based devices. The high-volume, low-cost fabrication potential of organic cells will allow for square miles of solar cell production at one-tenth the cost of conventional inorganic materials. Plastic solar cells take a minimum of storage space and can be inflated or unrolled for deployment. We will explore a cross-section of in-house and sponsored research efforts that aim to provide new hybrid technologies that include both inorganic and polymer materials as active and substrate materials. Research at University of Texas at Arlington focuses on the fabrication and use of poly(isothianaphthene-3,6-diyl) in solar cells. We describe efforts at Norfolk State University to design, synthesize and characterize block copolymers. A collaborative team between EIC Laboratories, Inc. and the University of Florida is investigating multijunction polymer solar cells to more effectively utilize solar radiation. The National Aeronautics and Space Administration (NASA)/Ohio Aerospace Institute (OAI) group has undertaken a thermal analysis of potential metallized substrates as well as production of nanoparticles of CuInS2 and CuInSe2 in good yield at moderate temperatures via decomposition of single-source precursors. Finally, preliminary work at the Rochester Institute of Technology (R.I.T.) to assess the impact on performance of solar cells of temperature and carbon nanotubes is reported. Technologies that must be developed to enable ultra-lightweight solar arrays include: monolithic interconnects, lightweight array structures, and new ultra-light support and deployment mechanisms. For NASA applications, any solar cell or array technology must not only meet weight and AMO efficiency goals, but also must be durable enough to survive launch conditions and space environments.

Hepp, Aloysius F.↗
DOE OSTI2024

Synthesis of Microscopic 3D Graphene for High‐Performance Supercapacitors with Ultra‐High Areal Capacitance

Abstract Despite graphene being considered an ideal supercapacitor electrode material, its use in commercial devices is limited because few methods exist to produce high‐quality graphene at a large scale and low cost. A simple method is reported to synthesize 3D graphene by graphenization of coal tar pitch with a K 2 CO 3 catalyst. This produces 3D graphenes with high specific surface areas up to 2113 m 2 g −1 and exceptional crystallinity (Raman I D / I G as low as ≈0.15). The material has an outstanding specific capacitance of 182.6 F g −1 at a current density of 1.0 A g −1 . This occurs at a mass loading of 30 mg cm −2 which is 3 times higher than commercial requirements, yielding an ultra‐high areal capacitance of 5.48 F cm −2 . The K 2 CO 3 is recycled and reused over 10 cycles with material quality and electrocapacitive performance of 3D graphene retained and verified after each cycle. The synthesis method and resulting electrocapacitive performance properties create new opportunities for using 3D graphene more broadly in practical supercapacitor devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Gradient synthesis of carbon quantum dots and activated carbon from pulp black liquor for photocatalytic hydrogen evolution and supercapacitor

Black liquor (BL) is a by-product of the chemical pulping industry and is mainly used as a low-value fuel; however, its potential to produce high-value products has not been fully exploited. In this study, a green and simple strategy is reported for the gradient production of Na + -functionalized carbon quantum dots (Na + -CQDs) for the first time, N and S co-doped CQDs (N/S-CQDs), and N and S co-doped KOH-activated carbon (N/S-KAC) from BL by dialysis, hydrothermal carbonization and activation-carbonization, respectively. Due to the good electron trapping ability, photoluminescence and promising up-conversion luminescence of CQDs, the hydrogen evolution efficiency of Na + -CQDs/TiO 2 and N/S-CQDs/TiO 2 photocatalysts was improved by 2.45 and 1.46 times, respectively, compared with pure TiO 2 . N/S-KAC with a high specific surface area of 2294 m 2 g -1 provides an excellent specific capacitance of 253 F g -1 at 0.5 A g -1 and a promising energy density of 26.92 Wh kg -1 under a power density of 566 W kg -1 for the fabricated symmetrical supercapacitor. Moreover, the electrode material has good cycling stability with a capacitance retention of ~ 93.91% after 5000 cycles. In conclusion, this pathway provides a versatile and scalable approach for the construction and co-production of nanostructured materials, photocatalysts and energy storage devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhancing Photocarrier Bulk Lifetime with Defect Engineering of Polycrystalline Passivated-Contact n-Cz Photovoltaic Devices

We study the photocarrier lifetime evolution of n-Cz Si material throughout the processing sequence for polycrystalline passivated contact devices. We show that a high temperature annealing pretreatment (known as Tabula Rasa) has a clear effect on enhancing bulk lifetimes of n-Cz Si. We further this development by integrating such defect engineering into the lower-temperature annealing of passivated contact. By applying oxidizing ambient gases during these anneals we report a photocarrier lifetime enhancement over an N 2 environment. This enhancement is exhibited in a 1-sun iV OC of 735 mV when annealed in O 2 rather than 708 mV in N 2.

14 SOLAR ENERGY↗
NASA NTRS1985

Crystal Growth of Device Quality Gaas in Space

The GaAs research evolves about these key thrust areas. The overall program combines: (1) studies of crystal growth on novel approaches to engineering of semiconductor material (i.e., GaAs and related compounds); (2) investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; and (3) investigation of electronic properties and phenomena controlling device applications and device performance. This effort is aimed at the essential ground-based program which would insure successful experimentation with and eventually processing of GaAs in near zero gravity environment. It is believed that this program addresses in a unique way materials engineering aspects which bear directly on the future exploitation of the potential of GaAs and related materials in device and systems applications.

Gatos, H. C.↗