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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Carbon aerogels with integrated engineered macroporous architectures for improved mass transport

Carbon aerogels (CAs) combine unique properties including ultra-high surface area, high electrical conductivity, corrosion resistance, and robust mechanical properties making them ideal materials for electrochemical applications. Traditional CA synthesis results in isotropic, random nanoporous networks that work well for applications relying on diffusional mass transport. However, many applications would benefit from integration of engineered macroporous network structures that enable directed pressure-gradient-driven mass transport. In this study, we report on using 3D-printed sacrificial polymeric templates to generate templated CAs (t-CAs) with integrated engineered nonrandom macroporous network structures. Specifically, we used projection micro-stereo-lithography (PμSL) and two-photon polymerization direct laser writing (2PP-DLW) to fabricate millimeter-to-centimeter-sized 3D sacrificial polymeric templates with features ranging from tens of microns (PμSL) to 100s of nanometers (2PP-DLW). T-CAs were fabricated by infiltrating the templates with resorcinol-formaldehyde (RF) precursor solution, followed by carbonization at 1050 °C to simultaneously convert the RF gel to a CA and decompose the 3D-printed template, leaving an embedded templated macroporous network structure behind. X-ray computer tomography confirms integration of the macroporous architecture defined by the template. The templated macroporous architecture improves mass transport in t-CAs compared to traditional bulk CA as demonstrated by more uniform activation and their response in electrochemical cyclic voltammetry and galvanostatic charge-discharge tests.

36 MATERIALS SCIENCE↗
NASA NTRS1973

Numerical analysis of stiffened shells of revolution. Volume 4: Engineer's program manual for STARS-2S shell theory automated for rotational structures - 2 (statics) digital computer program

The engineering programming information for the digital computer program for analyzing shell structures is presented. The program is designed to permit small changes such as altering the geometry or a table size to fit the specific requirements. Each major subroutine is discussed and the following subjects are included: (1) subroutine description, (2) pertinent engineering symbols and the FORTRAN coded counterparts, (3) subroutine flow chart, and (4) subroutine FORTRAN listing.

Svalbonas, V.↗
DOE OSTI2020

Enabling high rate capability, low internal resistance, and excellent cyclability for vanadium redox flow batteries utilizing ultrafast laser-structured graphite felt

The electrochemical performance of vanadium redox flow batteries (VRFBs) was enhanced via laser-patterned graphite felt (GF) electrodes. The laser-structured GF electrodes engineered via preparing a series of well-ordered microscopic channel structures with an average width of 200 μm, creating a three-dimensional carbon framework. The ultrafast laser patterning increased the porosity by 10%, as compared to pristine electrode. The analysis of the overpotential distribution using electrochemical impedance spectroscopy revealed that the electrode polarization involving charge transfer and diffusion resistance is strongly alleviated with the aid of carbon micro-perforation. The advanced design of laser-structured GF electrode also exhibits high rate capability, low internal resistance, and excellent cyclability. The improved performance was attributed to the synergistic effect involving (i) high electrochemically active surface area for rapid electrochemical reactions (i.e., V(II)/V(III) and V(IV)/V(V) redox couples) and (ii) excellent transport properties for facile electron/ion/species transport. The micro-scale channels created with the laser-ablation technique act as capillary structures and enabled homogeneous and rapid wetting of GF electrodes as formulated with the classical Washburn equation. The VRFB equipped with the laser-structured GF electrodes delivered a high discharge capacity with exceptional capacity retention upon extended cycling (>84.9%). In conclusion, accordingly, the design of laser-structured electrode paves the pathway towards finely tuning the electrode internal microstructure for improved cyclability, durability, and capacity retention in various electrochemical energy storage/conversion devices (e.g. all-vanadium redox flow batteries).

25 ENERGY STORAGE↗
NASA NTRS2021

A Summary of Normal Incidence Tube Tests of NASA'S Bio-inspired Broadband Acoustic Absorber

Motivated by the need to reduce noise pollution from aircraft engines, NASA has continued to design, manufacture and test recently patented structures that mimic the geometry and the broadband and low frequency acoustic absorption of assemblies of natural reeds. This report documents a screening test, which is a precursor to more controlled modelling experiments. The purpose of this experiment was to identify variables and prototype design features that might play a dominant role in the acoustic performance of these structures. To date, twenty-four prototypes, each with an overall shape of a cube (nominally 50 mm x 50 mm x 50 mm), were designed and additively manufactured from thermoplastics using a Fused Filament Fabrication technique. The prototypes were tested in the NASA Glenn and Langley Normal Incidence Tubes to experimentally determine the acoustic absorption as a function of frequency from 400 Hz to 3000 Hz. Results indicate that a variety of structures exhibit substantial acoustic absorption in that frequency range, with an average absorption coefficient greater than 0.6, especially in the frequency range of 400 Hz to 1000 Hz. Six basic prototype designs were chosen to inform future modeling research. Results of these experiments can be used to evaluate existing physics-based models of the interaction of sound waves with these structures or to develop new models. Validated physics-based models of these structures can help engineers optimize the designs for different commercial noise control applications.

Acoustics↗
NASA NTRS2013

HESTIA Commodities Exchange Pallet and Sounding Rocket Test Stand

During my Spring 2016 internship, my two major contributions were the design of the Commodities Exchange Pallet and the design of a test stand for a 100 pounds-thrust sounding rocket. The Commodities Exchange Pallet is a prototype developed for the Human Exploration Spacecraft Testbed for Integration and Advancement (HESTIA) program. Under the HESTIA initiative the Commodities Exchange Pallet was developed as a method for demonstrating multi-system integration thru the transportation of In-Situ Resource Utilization produced oxygen and water to a human habitat. Ultimately, this prototype's performance will allow for future evaluation of integration, which may lead to the development of a flight capable pallet for future deep-space exploration missions. For HESTIA, my main task was to design the Commodities Exchange Pallet system to be used for completing an integration demonstration. Under the guidance of my mentor, I designed, both, the structural frame and fluid delivery system for the commodities pallet. The fluid delivery system includes a liquid-oxygen to gaseous-oxygen system, a water delivery system, and a carbon-dioxide compressors system. The structural frame is designed to meet safety and transportation requirements, as well as the ability to interface with the ER division's Portable Utility Pallet. The commodities pallet structure also includes independent instrumentation oxygen/water panels for operation and system monitoring. My major accomplishments for the commodities exchange pallet were the completion of the fluid delivery systems and the structural frame designs. In addition, parts selection was completed in order to expedite construction of the prototype, scheduled to begin in May of 2016. Once the commodities pallet is assembled and tested it is expected to complete a fully integrated transfer demonstration with the ISRU unit and the Environmental Control and Life Support System test chamber in September of 2016. In addition to the development of the Commodities Exchange Pallet, I also assisted in preparation for testing the upper stage of a sounding rocket developed as a Center Innovation Fund project. The main objective of this project is to demonstrate the integration between a propulsion system and a solid oxide fuel cell (SOFC). The upper stage and SOFC are scheduled to complete an integrated test in August of 2016. As part of preparation for scheduled testing, I was responsible for designing the upper stage's test stand/support structure and main engine plume deflector to be used during hot-fire testing (fig. 3). The structural components of the test stand need to meet safety requirements for operation of the propulsion system, which consist of a 100 pounds-thrust main engine and two 15 pounds-thrust reaction control thrusters. My main accomplishment for this project was the completion of the design and the parts selection for construction of the structure, scheduled to begin late April of 2016.

Chaparro, Javier↗
NASA NTRS1979

Materials and structural aspects of advanced gas-turbine helicopter engines

The key to improved helicopter gas turbine engine performance lies in the development of advanced materials and advanced structural and design concepts. The modification of the low temperature components of helicopter engines (such as the inlet particle separator), the introduction of composites for use in the engine front frame, the development of advanced materials with increased use-temperature capability for the engine hot section, can result in improved performance and/or decreased engine maintenance cost. A major emphasis in helicopter engine design is the ability to design to meet a required lifetime. This, in turn, requires that the interrelated aspects of higher operating temperatures and pressures, cooling concepts, and environmental protection schemes be integrated into component design. The major material advances, coatings, and design life-prediction techniques pertinent to helicopter engines are reviewed; the current state-of-the-art is identified; and when appropriate, progress, problems, and future directions are assessed.

Freche, J. C.↗
NASA NTRS2012

Integrated Design Engineering Analysis (IDEA) Environment Automated Generation of Structured CFD Grids using Topology Methods

This report documents the work performed from March 2010 to March 2012. The Integrated Design and Engineering Analysis (IDEA) environment is a collaborative environment based on an object-oriented, multidisciplinary, distributed framework using the Adaptive Modeling Language (AML) as a framework and supporting the configuration design and parametric CFD grid generation. This report will focus on describing the work in the area of parametric CFD grid generation using novel concepts for defining the interaction between the mesh topology and the geometry in such a way as to separate the mesh topology from the geometric topology while maintaining the link between the mesh topology and the actual geometry.

Kamhawi, Hilmi N.↗
DOE OSTI2019

Broadband (0–5 Hz) Fully Deterministic 3D Ground‐Motion Simulations of a Magnitude 7.0 Hayward Fault Earthquake: Comparison with Empirical Ground‐Motion Models and 3D Path and Site Effects from Source Normalized Intensities

We report on high‐performance computing (HPC) fully deterministic simulation of ground motions for a moment magnitude (⁠Mw⁠) 7.0 scenario earthquake on the Hayward fault resolved to 5 Hz using the SW4 finite‐difference code. We computed motions obeying physics‐based 3D wave propagation at a regional scale with an Mw 7.0 kinematic rupture model generated following Graves and Pitarka (2016). Both plane‐layered (1D) and 3D Earth models were considered, with 3D subsurface material properties and topography interpolated from a model of the U.S. Geological Survey (USGS). The resulting ground‐motion intensities cover a broader frequency range than typically considered in regional‐scale simulations, including higher frequencies relevant for engineering analysis of structures. Median intensities for sites across the domain are within the reported between‐event uncertainties (⁠τ⁠) of ground‐motion models (GMMs) across spectral periods 0.2–10 s (frequencies 0.1–5 Hz). The within‐event standard deviation ϕ of ground‐motion intensity measurement residuals range 0.2–0.5 natural log units with values consistently larger for the 3D model. Source‐normalized ratios of intensities (3D/1D) reveal patterns of path and site effects that are correlated with known geologic structure. These results demonstrate that earthquake simulations with fully deterministic wave propagation in 3D Earth models on HPC platforms produce broadband ground motions with median and within‐event aleatory variability consistent with empirical models. Systematic intensity variations for the 3D model caused by path and site effects suggest that these epistemic effects can be estimated and removed to reduce variation in site‐specific hazard estimates. This study motivates future work to evaluate the validity of the USGS 3D model and investigate the development of path and site corrections by running more scenarios.

Rodgers, Arthur J.↗
DOE OSTI2019

Interfacial Engineering for High Efficiency Nanorod Array Structured Perovskite Solar Cells

TiO 2 nanorod (NR) array for perovskite solar cells (PSCs) has attached great importance due to superb power conversion efficiency (PCE) compared to traditional mesoporous TiO 2 film. A TiO 2 compact layer for the growth of TiO 2 NR array via spin-coating cannot meet the requirements for efficient NR based PSCs. Herein we have developed and demonstrated inserting an bifunctional extra-thin TiO 2 interlayer (5 nm) by atomic layer deposition (ALD) at the interface of FTO/TiO 2 compact layer to achieve an alleviated electron exchange and a reduced energetic barrier. Thus, an accelerated extraction of electrons from TiO 2 NR arrays via the compact layer to FTO substrate is ready for improving the PSC efficiency. The thickness of the spin-coated TiO 2 compact layer on the ALD-deposited TiO 2 layer is spontaneously optimized. Finally, an outstanding efficiency of 20.28% has been achieved from a champion PSC with negligible hysteresis and high reliability. To the best of our knowledge, this is the first time to demonstrate the superiority of TiO 2 -NR based PSCs withstanding in dry heat and thermal cycling tests. The results are of great importance for the preparation of efficient and durable PSCs for our real-world applications.

25 ENERGY STORAGE↗
DOE OSTI2024

Porous Polymer Structures with Tunable Mechanical Properties Using a Water Emulsion Ink

Recently, the manufacturing of porous polydimethylsiloxane (PDMS) with engineered porosity has gained considerable interest due to its tunable material properties and diverse applications. An innovative approach to control the porosity of PDMS is to use transient liquid phase water to improve its mechanical properties, which has been explored in this work. Adjusting the ratios of deionized water to the PDMS precursor during blending and subsequent curing processes allows for controlled porosity, yielding water emulsion foam with tailored properties. The PDMS-to-water weight ratios were engineered ranging from 100:0 to 10:90, with the 65:35 specimen exhibiting the best mechanical properties with a Young’s Modulus of 1.17 MPa, energy absorption of 0.33 MPa, and compressive strength of 3.50 MPa. This led to a porous sample exhibiting a 31.46% increase in the modulus of elasticity over a bulk PDMS sample. Dowsil SE 1700 was then added, improving the storage capabilities of the precursor. The optimal storage temperature was probed, with -60 °C resulting in great pore stability throughout a three-week duration. The possibility of using these water emulsion foams for paste extrusion additive manufacturing (AM) was also analyzed by implementing a rheological modifier, fumed silica. Fumed silica’s impact on viscosity was examined, revealing that 9 wt% of silica demonstrates optimal rheological behaviors for AM, bearing a viscosity of 10,290 Pa·s while demonstrating shear-thinning and thixotropic behavior. This study suggests that water can be used as pore-formers for PDMS in conjunction with AM to produce engineered materials and structures for aerospace, medical, and defense industries as sensors, microfluidic devices, and lightweight structures.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Network Polymer Properties Engineered Through Polymer Backbone Dispersity and Structure

Abstract Dispersity ( Ð or M w /M n ) is an important parameter in material design and as such can significantly impact the properties of polymers. Here, polymer networks with independent control over the molecular weight and dispersity of the linear chains that form the material are developed. Using a RAFT polymerization approach, a library of polymers with dispersity ranging from 1.2—1.9 for backbone chain‐length (DP) 100, and 1.4—3.1 for backbone chain‐length 200 were developed and transformed to networks through post‐polymerization crosslinking to form disulfide linkers. The tensile, swelling, and adhesive properties were explored, finding that both at DP 100 and DP 200 the swelling ratio, tensile strength, and extensibility were superior at intermediate dispersity (1.3—1.5 for DP 100 and 1.6—2.1 for DP 200) compared to materials with either substantially higher or lower dispersity. Furthermore, adhesive properties for materials with chains of intermediate dispersity at DP 200 revealed enhanced performance compared to the very low or high dispersity chains.

Raji, Ibrahim O.↗
DOE OSTI2024

Network Polymer Properties Engineered Through Polymer Backbone Dispersity and Structure

Abstract Dispersity ( Ð or M w /M n ) is an important parameter in material design and as such can significantly impact the properties of polymers. Here, polymer networks with independent control over the molecular weight and dispersity of the linear chains that form the material are developed. Using a RAFT polymerization approach, a library of polymers with dispersity ranging from 1.2—1.9 for backbone chain‐length (DP) 100, and 1.4—3.1 for backbone chain‐length 200 were developed and transformed to networks through post‐polymerization crosslinking to form disulfide linkers. The tensile, swelling, and adhesive properties were explored, finding that both at DP 100 and DP 200 the swelling ratio, tensile strength, and extensibility were superior at intermediate dispersity (1.3—1.5 for DP 100 and 1.6—2.1 for DP 200) compared to materials with either substantially higher or lower dispersity. Furthermore, adhesive properties for materials with chains of intermediate dispersity at DP 200 revealed enhanced performance compared to the very low or high dispersity chains.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Engineering a highly dispersed core@shell structure for efficient photocatalysis: A case study of ternary novel BiOI@MIL-88A(Fe)@g-C3N4 nanocomposite

Highlights: • Novel ternary BiOI@MIL-88A(Fe)@g-C{sub 3}N{sub 4} core@shell photocatalyst is reported. • Photocatalytic degradation mechanism of organic pollutants is investigated. • It is divulged that the photodegradation is increased by BiOI supporting. • Core@shell structure of MIL-88A(Fe)@g-C{sub 3}N{sub 4} causes high activity. • Strong visible light absorption and electron transfer improve activity. - Abstract: Ternary novel BiOI@MIL-88A(Fe)@g-C{sub 3}N{sub 4} nanocomposite with core@shell structure was successfully synthesized by hydrothermal method. Fabricated photocatalysts were characterized and results confirmed the formation of MIL-88A(Fe)@g-C{sub 3}N{sub 4} core@shell structure and subsequently BiOI decoration on the surface of MIL-88A(Fe)@g-C{sub 3}N{sub 4}. Photocatalytic performances of prepared samples were investigated for degradation of Acid Blue 92 (AB92), Rhodamine B (RhB) and phenol under visible irradiation. It is clearly demonstrated that the as-prepared ternary BiOI@MIL-88A(Fe)@g-C{sub 3}N{sub 4} composites exhibits exceptional visible-light photocatalytic activities for cationic, anionic as well as neutral pollutant molecules compared to the widely accepted outstanding g-C{sub 3}N{sub 4}. It is mainly proved that the exceptional photocatalytic efficiencies are comprehensively ascribed to the porous structure of MIL-88A(Fe)@g-C{sub 3}N{sub 4}, greatly promoted charge separation and introduced catalytic functions to the carrier-related redox reactions by decorating BiOI and coupling g-C{sub 3}N{sub 4}, to modulate holes and electrons. Additionally, studies performed using radical scavengers showed the main reactive species in the photocataytic reaction for all chemical pollutant degradation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Active Site Engineering via Optimizing the Heterogeneous Support Structure for Single-Atom Catalysis

Supported single-atom catalysts show a large range of activities and selectivities that depend on the local environment of the catalytic sites. Here a theory-based optimization strategy is presented that is based on a density functional theory determination of the transition states and intermediates for a low-dimensional coordinate representation of the heterogeneity of the active sites. The approach is applied to a vanadium catalyst on an amorphous SiO 2 support that involves a large kinetic network described using a full chemistry model. Without assuming a priori scaling relations or mechanism reduction, the optimal state of heterogeneity is found to lie at atomic configurations where the activation energies for two distinct key chemical processes are equal. It is found a posteriori that the behavior of the system is consistent with linear free energy scaling relations in the randomness parameters. The energetic span theory proves quite useful in reducing the full chemistry model to a small number of key reactions. The use of a nonlinear optimization algorithm in combination with energetic span theory provides significant simplification in treating disordered systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Experimental investigation of the relationship between thermal barrier coating structured porosity and homogeneous charge compression ignition engine combustion

Heat transfer has a monumental influence on homogeneous charge compression ignition combustion. When a thermal barrier coating is applied to the combustion chamber, the insulating effect magnifies the wall temperature swing, decreasing heat transfer during combustion. This enables improvements in both thermal and combustion efficiency without the detrimental impacts of intake charge heating. Increasing the temperature swing requires coatings with lower thermal conductivity and heat capacity. An enticing avenue for simultaneously decreasing both thermal conductivity and capacity is to increase the porosity fraction. A proprietary solution precursor plasma spray process enables discrete organization of the porosity structure, called inter-pass boundaries, which in turn produces a step-reduction in thermal conductivity for a given porosity level. In this investigation, yttria-stabilized zirconia is used to create four different thermal barrier coatings to study the potential of structured porosity as means of improving the “temperature swing” behavior in a homogeneous charge compression ignition engine. The baseline coating is “dense YSZ,” applied using a standard air-plasma spray process. Furthermore, significant reductions of the thermal conductivity are achieved by utilizing the solution precursor plasma spray process to create inter-pass boundaries with a moderate overall porosity. Performance, efficiency, and emissions are compared against both a baseline configuration with a metal piston and an air-plasma spray “dense YSZ” coating. Experiments are carried out in a single-cylinder gasoline homogeneous charge compression ignition engine with exhaust re-induction. Experiments indicate that incorporating structured porosity into thermal barrier coatings produces tangible gains in combustion and thermal efficiencies. However, there is an upper limit to porosity levels acceptable for homogeneous charge compression ignition engine application because an elevated porosity fraction leads to excessive surface roughness and undesirable fuel interactions. Comparison of the coatings showed the best results with coating thickness of up to 150 µm. Thicker coatings led to slower surface temperature response and attenuated swing temperature magnitude.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS2004

Nonlinear Thermoelastic Model for SMAs and SMA Hybrid Composites

A constitutive mathematical model has been developed that predicts the nonlinear thermomechanical behaviors of shape-memory-alloys (SMAs) and of shape-memory-alloy hybrid composite (SMAHC) structures, which are composite-material structures that contain embedded SMA actuators. SMAHC structures have been investigated for their potential utility in a variety of applications in which there are requirements for static or dynamic control of the shapes of structures, control of the thermoelastic responses of structures, or control of noise and vibrations. The present model overcomes deficiencies of prior, overly simplistic or qualitative models that have proven ineffective or intractable for engineering of SMAHC structures. The model is sophisticated enough to capture the essential features of the mechanics of SMAHC structures yet simple enough to accommodate input from fundamental engineering measurements and is in a form that is amenable to implementation in general-purpose structural analysis environments.

Turner, Travis L.↗