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Results for “transport stabilization”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

CO 2 -selective membranes containing amino acid salts for CO 2 /N 2 separation

In this paper, facilitated transport membranes comprising polyvinylamine (PVAm) as fixed carrier and different amino acid salts (AAS) as mobile carriers were synthesized for post-combustion capture. The AAS carriers were prepared by deprotonating alanine (Ala), lysine (Lys), and proline (Pro) with 2-(1-piperazinyl)ethylamine (PZEA). CO 2 separation performances of the membranes with these AAS carriers were compared, and the AAS effectiveness to facilitate transport of CO 2 was in the order of PZEA-Pro > PZEA-Lys > PZEA-Ala. Here, the membrane comprising 35 wt.% PVAm and 65 wt.% PZEA-Pro at 57 °C rendered a promising CO 2 permeance of 936 GPU and a CO 2 /N 2 mixed gas selectivity of 193. When the PVAm was reduced to 15 wt.%, i.e., its 20 wt.% was replaced by the mobile carrier of PZEA-Sar (sarcosinate), the permeance further improved to 947 GPU with a remarkable CO 2 /N 2 selectivity of 210. Moreover, thermal gravimetric analysis showed a good thermal stability of the membrane, and membrane stability testing also gave stable transport performance. Furthermore, spectroscopic ellipsometry analysis exhibited a uniform membrane selective layer and an excellent agreement on the membrane thickness of ca. 170 nm measured independently by SEM. In addition, the membranes presented in this paper surpassed both the Robeson upper bound and the modified upper bound, indicating a great potential for CO 2 capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Amine-Containing Membranes with Functionalized Multi-Walled Carbon Nanotubes for CO2/H2 Separation

Amine-containing mixed-matrix membranes incorporated with amino-functionalized multi-walled carbon nanotubes (AF-MWNTs) were synthesized for CO2/H2 separation based on the facilitated transport mechanism. AF-MWNTs were chosen primarily as the mechanical reinforcing filler to enhance the membrane stability. At 107 °C and 0.2-MPa feed pressure, the membrane incorporated with 10 wt.% AF-MWNTs showed a CO2 permeability of 3196 Barrers and a CO2/H2 selectivity of 205. At the higher feed pressure of 1.5 MPa, owing to the carrier saturation phenomenon, the same membrane exhibited reduced transport performance with a CO2 permeability of 776 Barrers and a CO2/H2 selectivity of 31. These separation performances at both the low and high feed pressures were well above the theoretical upper bound. Furthermore, the incorporation of 10 wt.% AF-MWNTs led to a significant improvement on membrane stability. The transport performance and selective layer thickness of this membrane maintained for 100 h, which suggested that the incorporation of AF-MWNTs improved the resistance to membrane compaction upon a high feed pressure. Therefore, this work is considered as one of the crucial steps to enable the application of facilitated transport membranes to high-pressure gas processing such as syngas purification.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

High-throughput and data-driven search for stable optoelectronic AMSe 3 materials

The rapid advancement in emerging optoelectronic technologies demands highly efficient, affordable, and ecofriendly materials. In this context, ternary chalcogenides, especially ternary selenides, show early promise as a material class due to their stability and remarkable electronic, optical, and transport properties. In this work, we integrate first-principles-based high-throughput computations with machine learning (ML) techniques to predict the thermodynamic stability and optoelectronic properties of 920 valency-satisfied selenide compounds. Through investigating polymorphism, our study reveals the edge-sharing orthorhombic Pnma phase (NH 4 CdCl 3 -type) as the most stable structure for most ternary selenides. High-fidelity supervised ML models are trained and tested to accelerate stability and band gap predictions. These data-driven models pin down the most influential features that dominantly control key material characteristics. The multistep high-throughput computations identify the ternary selenides with optimal direct band gaps, light carrier masses, and strong optical absorption edges. The extensive materials screening considering phase stability, toxicity, and defect tolerance, finally identifies the seven most suitable candidates for photovoltaic applications. Two of these final compounds, SrZrSe 3 and SrHfSe 3 , have already been synthesized in a single-phase form, with the latter showing an optically suitable band gap, aligning well with our findings. The non-adiabatic molecular dynamics reveal sufficiently long photoexcited charge carrier lifetimes (on the order of nanoseconds) in some of these selected selenide materials, indicating their exciting characteristics. Overall, our study suggests a robust in silico framework that can be extended to screen large datasets of various material classes for identifying promising photoactive candidates.

36 MATERIALS SCIENCE↗
NASA NTRS1982

Development and flight evaluation of an augmented stability active controls concept: Executive summary

A pitch active control system (PACS) was developed and flight tested on a wide body jet transport (L-1011) with a flying horizontal stabilizer. Two dual channel digital computers and the associated software provide command signals to a dual channel series servo which controls the stabilizer power actuators. Input sensor signals to the computer are pitch rate, column trim position, and dynamic pressure. Control laws are given for the PACS and the system architecture is defined. Discussions are given regarding piloted flight simulation and vehicle system simulation and vehicle system simulation tests that are performed to verify control laws and system operation prior to installation on the aircraft. Modifications to the basic aircraft included installation of the PACS, addition of a c.g. management system to provide a c.g. range from 25 to 39% mac, and downrigging of the geared elevator to provide the required nose down control authority for aft c.g. flight test conditions. Three pilots used the Cooper-Harper Rating Scale to judge flying qualities of the aircraft with PACS on and off. The handling qualities with the c.g. at 39% mac (41% stability margin) and PACS operating were judged to be as good as the handling qualities with the c.g. at 25% mac (+15% stability margin) and PACS off.

Guinn, W. A.↗
DOE OSTI2020

Synthesis, Crystal Growth, and Transport Properties of van der Waals Tetrel Pnictide GeAs 2

Here, bulk GeAs 2 was synthesized utilizing a vapor transport reaction with iodine. Thermal stability tests under dynamic conditions show that GeAs 2 decomposes below 700 K, in contrast to the reported congruent melting at 1029 K measured at saturated As vapor pressure. GeAs 2 is a p-type narrow bandgap (~0.4 eV) semiconductor. From a thermoelectric standpoint, GeAs 2 outperforms previous computational predictions in thermopower and thermal conductivity. Yet, electrical resistivity is significantly higher than predicted values, resulting in the low overall thermoelectric figure of merit. Aliovalent doping strategies for GeAs 2 should be developed to achieve reasonable thermoelectric performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

Stability and control results for advanced turboprop aft-mount installations

An experimental investigation was recently conducted in the NASA-Langley Research Center 4- by 7-Meter Tunnel to explore the effects of aft-mounted advanced turboprop installations on the low-speed stability and control characteristics of a representative transport aircraft configuration. For the conditions investigated, the experimental results indicate that the longitudinal and directional stability of the configuration was not adversely affected by aft-pylon-mounted single-rotation tractor or counter-rotation pusher propeller installations. The results indicate that for the single-rotation tractor configuration the propeller induced aerodynamics are dominated by the interaction of the propeller slipsteam with the pylon, and that the propeller contribution to the stability characteristics for the counter-rotating pusher configuration is dominated by propeller normal forces. The longitudinal and directional control effectiveness, engine-out characteristics, and ground effects are also presented.

Coe, P. L., Jr.↗
NASA NTRS1982

Development and flight evaluation of an augmented stability active controls concept with a small horizontal tail

A limited authority pitch active control system (PACS) was developed for a wide body jet transport (L-1011) with a flying horizontal stabilizer. Two dual channel digital computers and the associated software provide command signals to a dual channel series servo which controls the stabilizer power actuators. Input sensor signals to the computer are pitch rate, column-trim position, and dynamic pressure. Control laws are given for the PACS and the system architecture is defined. The piloted flight simulation and vehicle system simulation tests performed to verify control laws and system operation prior to installation on the aircraft are discussed. Modifications to the basic aircraft are described. Flying qualities of the aircraft with the PACS on and off were evaluated. Handling qualities for cruise and high speed flight conditions with the c.g. at 39% mac ( + 1% stability margin) and PACS operating were judged to be as good as the handling qualities with the c.g. at 25% (+15% stability margin) and PACS off.

Rising, J. J.↗
DOE OSTI2026

How Silica Surface Chemistry Modulates Interfacial Water: Insights from Machine Learning Molecular Dynamics

Controlling water structure and dynamics at silica interfaces are central to a wide range of technologies, including protective oxide layers for solar water splitting and nanoporous membranes. In this work, we develop a machine learning interatomic potential, trained via active learning, to achieve ab initio accuracy for water confined between hydroxylated silica surfaces over a range of silanol coverages and slit widths. We find that partially hydroxylated surfaces (50 and 75% OH) support stronger water−surface hydrogen bonding and more extended interfacial density profiles than fully hydroxylated (100% OH) surfaces, indicating that increasing OH coverage does not necessarily strengthen interfacial hydrogenbond networks. Translational diffusion decreases approximately linearly with slit width and OH coverage, whereas rotational dynamics respond nonlinearly. In particular, at the smallest slit width of 5 Å, 75% OH coverage produces an enhanced local tetrahedral ordered interfacial network that strongly suppresses reorientation, while 100% coverage yields a crowded, disordered interfacial layer that also hinders rotation. In contrast, the 50% OH coverage is sufficiently sparse that it does not markedly alter water structure or dynamics under confinement. These results show that coupled control of pore size and surface chemistry enables nonlinear tuning of interfacial water structure and transport, providing a design strategy for optimizing porous silica for either enhanced interfacial stability and controlled reactivity or rapid and selective transport.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Decoupling mass transport and electron transfer by a double-cathode structure of a Li-O 2 battery with high cyclic stability

Aprotic lithium-oxygen (Li-O 2 ) batteries have attracted extensive attention due to their ultrahigh theoretical energy density. However, slow and undesired electron transfer during cathodic reactions causes low cyclic stability in these batteries. Here, in this paper, we demonstrate that O 2 mass transport and electron transfer for cathodic reactions in Li-O 2 batteries could be decoupled by a double-cathode structure that efficiently enables stable electron transfer between the cathode and Li 2 O 2 /O 2 . This resolves various side reactions and slow Li 2 O 2 reaction kinetics issues in conventional Li-O 2 batteries, leading to stable operation of the cell for nearly 2 months at a capacity of 0.2 and 5 mAh cm -2 , with more than 4- and 10-fold increases in cycle life when compared with single-cathode batteries. These remarkable improvements in the cyclic stability of Li-O 2 batteries with double cathodes provide an interesting concept for improving the operational stability of other metal-rechargeable batteries with conversion-type chemistry.

25 ENERGY STORAGE↗
DOE OSTI2023

Tuned Reactivity at the Lithium Metal–Argyrodite Solid State Electrolyte Interphase

Thin intermetallic Li 2 Te–LiTe 3 bilayer (0.75 µm) derived from 2D tellurene stabilizes the solid electrolyte interphase (SEI) of lithium metal and argyrodite (LPSCl, Li 6 PS 5 Cl) solid-state electrolyte (SSE). Tellurene is loaded onto a standard battery separator and reacted with lithium through single-pass mechanical rolling or transferred directly to SSE surface by pressing. State-of-the-art electrochemical performance is achieved, e.g., symmetric cell stable for 300 cycles (1800 h) at 1 mA cm -2 and 3 mAh cm -2 (25% DOD, 60 µm foil). Cryo-stage focused ion beam (Cryo-FIB) sectioning and Raman mapping demonstrate that the Li 2 Te–LiTe 3 bilayer impedes SSE decomposition. The unmodified Li–LPSCl interphase is electrochemically unstable with a geometrically heterogeneous reduction decomposition reaction front that extends deep into the SSE. Decomposition drives voiding in Li metal due to its high flux to the reaction front, as well as voiding in the SSE due to the associated volume changes. Analysis of cycled SSE found no evidence for pristine (unreacted) lithium metal filaments/dendrites, implying failure driven by decomposition phases with sufficient electrical conductivity that span electrolyte thickness. In conclusion, DFT calculations clarify thermodynamic stability, interfacial adhesion, and electronic transport properties of interphases, while mesoscale modeling examines interrelations between reaction front heterogeneity (SEI heterogeneity), current distribution, and localized chemo-mechanical stresses.

25 ENERGY STORAGE↗
DOE OSTI2025

Advancements in nanocomposites for enhancing the performance of rechargeable lithium-ion batteries

The benefits of nanotechnology have been realized in almost every component of lithium-ion batteries. From electrodes to electrolytes, the incorporation of nanoparticles as dopants and coatings has shown marked improvements in cell cycle life, efficiency, mechanical and thermal stabilities, and lithium-ion transport. The improvements realized depends on several factors, from processing methods, nanoparticle type, structure, and concentration, to the material into which the nanoparticulate will be incorporated. Regardless of these many factors, nanotechnology has vastly improved the performance of secondary lithium-ion batteries. Here we will highlight some of the works that demonstrate these improvements and the quantitative benefits of nanotechnology.

25 ENERGY STORAGE↗
DOE OSTI2022

Tracking the environmental impacts of ecological engineering on coastal wetlands with numerical modeling and remote sensing

Coastal wetlands are the most valuable ecosystems on the earth but facing severe degradation and losses owing to climate change and anthropogenic activities. Many ecological engineering projects (EEP) have been conducted to mitigate the degradation of coastal wetlands. However, the geomorphological impacts of EEP on coastal wetlands have not been well documented. In this study, a method employed a process-based hydrodynamic model and remote sensing (RS) was developed to evaluate the impacts of EEP on the geomorphological change of a prototype Ramsar site. Results demonstrated that RS has great potential in improving the quality of bathymetry data for the numerical model with a decrease of RMSE from 0.52 m to 0.3 m. It also showed good capacity in trend detection of geomorphological change spatially. Results showed the Chongming Dongtan wetland experienced erosion with an annual rate of -0.035 m/yr from 2013 to 2016 after the implementation of EEP. The deposition rate changed significantly in the area within 200 m of the EEP. It is found that the EEP modified the composition of vegetation, sediment transportation, as well as substrate stability, affecting the geomorphological change of coastal wetlands. It is suggested that the EEP with moderate anthropogenic disturbance is a direct and effective way to recover the coastal habitats for waterbirds. However, the modification of the coastal wetland ecosystem by EEP will lead to the potential vulnerability to global climate change. Therefore, how to mitigate the advantages and disadvantages of the EEP is needed to be further studied to find a more sustainable way for coastal management.

geomorphological change, coastal wetlands, Ecologi↗
DOE OSTI2026

Impact of Fermentation-Derived Substrates on Hydrogen Production in Zero-Gap Microbial Electrolysis Cells

Zero-gap microbial electrolysis cells (MECs) represent a promising platform for hydrogen production from liquid waste streams due to reduced interelectrode spacing that lowers internal resistance and enhances mass transport. However, the performance and stability of zero-gap MECs treating chemically complex feedstocks remain insufficiently characterized. Here, we operated zero-gap MECs with real, unamended, corn stover dark fermentation effluent containing a wide range of organic substrates. The MECs fed fermentation effluent achieved a maximum current density of 24 A/m2 (15+-6 A/m2 over the cycle) and a hydrogen production rate of 75 L/L-d (42+-19 L/L-d over the cycle). The substrates were consumed at different rates, indicating substrate-selective utilization by the anodic microbial community. Acetate supported high and stable current generation, whereas ethanol, formate, lactate, and amino acids induced varying degrees of inhibition depending on their concentration. Residual sugars caused pronounced current fluctuations, consistent with ongoing fermentation and local pH changes. A diverse microbial community was crucial for efficiently utilizing complex organics and maximizing electrochemical performance. These results demonstrate how and to what extent substrate composition regulates zero-gap MEC performance and that microbial community and operational conditions can be leveraged to enhance performance. These novel findings provide practical guidance for achieving robust hydrogen recovery from chemically heterogeneous real liquid waste streams.

08 HYDROGEN↗
DOE OSTI2024

A comprehensive review on liquid electrolyte design for low-temperature lithium/sodium metal batteries

Lithium/sodium metal batteries (LMBs/SMBs) possess immense potential for various applications due to their high energy density. Nevertheless, LMBs/SMBs are highly susceptible to the detrimental effects of an unstable solid electrolyte interphase (SEI) and dendrites during practical applications, particularly pronounced in low-temperature environments. Furthermore, sluggish ion transportation further compromises the cycling stability of LMBs/SMBs at low temperatures. To achieve stable operation of LMBs/SMBs at low temperatures, researchers have made numerous efforts including electrolyte optimization aimed at creating stable SEIs and suppressing the metal dendrites under low temperature conditions. Despite the significant advancements made recently in the liquid electrolyte design, there remains considerable hurdle in electrolyte engineering for practical low-temperature, high energy density LMBs/SMBs, calling for a profound comprehension of the intricate interplay between the electrochemical reaction kinetics and electrolyte compositions. Here, this review provides a thorough overview of various strategies in optimizing liquid electrolytes covering weakly solvating electrolytes, concentration-designed electrolytes, and solvation structure-designed electrolytes, to address the challenges faced by LMBs/SMBs at low temperatures, including slow reaction kinetics and the difficulties in Li + /Na + solvation/desolvation. Furthermore, this review discusses future prospects for the advancement of this field, intending to provide valuable insights and support for subsequent research undertakings.

25 ENERGY STORAGE↗
DOE OSTI2021

Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST

A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 μm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of Te can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × Te,0; thus, early results are also presented.

Delgado-Aparicio, L. F. (ORCID:0000000167394380)↗
DOE OSTI2020

Robust paths to net greenhouse gas mitigation and negative emissions via advanced biofuels

Biofuel and bioenergy systems are integral to most climate stabilization scenarios for displacement of transport sector fossil fuel use and for producing negative emissions via carbon capture and storage (CCS). However, the net greenhouse gas mitigation benefit of such pathways is controversial due to concerns around ecosystem carbon losses from land use change and foregone sequestration benefits from alternative land uses. Here, we couple bottom-up ecosystem simulation with models of cellulosic biofuel production and CCS in order to track ecosystem and supply chain carbon flows for current and future biofuel systems, with comparison to competing land-based biological mitigation schemes. Analyzing three contrasting US case study sites, we show that on land transitioning out of crops or pasture, switchgrass cultivation for cellulosic ethanol production has per-hectare mitigation potential comparable to reforestation and severalfold greater than grassland restoration. In contrast, harvesting and converting existing secondary forest at those sites incurs large initial carbon debt requiring long payback periods. We also highlight how plausible future improvements in energy crop yields and biorefining technology together with CCS would achieve mitigation potential 4 and 15 times greater than forest and grassland restoration, respectively. Finally, we show that recent estimates of induced land use change are small relative to the opportunities for improving system performance that we quantify here. While climate and other ecosystem service benefits cannot be taken for granted from cellulosic biofuel deployment, our scenarios illustrate how conventional and carbon-negative biofuel systems could make a near-term, robust, and distinctive contribution to the climate challenge.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Monofluorinated acetal electrolyte for high-performance lithium metal batteries

High degree of fluorination for ether electrolytes has resulted in improved cycling stability of lithium metal batteries due to stable solid electrolyte interphase (SEI) formation and good oxidative stability. However, the sluggish ion transport and environmental concerns of high fluorination degree drive the need to develop less fluorinated structures. Here, we depart from the traditional ether backbone and introduce bis(2-fluoroethoxy)methane (F2DEM), featuring monofluorination of the acetal backbone. High coulombic efficiency and stable long-term cycling in Li||Cu half cells can be achieved with F2DEM even under fast Li metal plating conditions. The performance of F2DEM is further compared with diethoxymethane (DEM) and 2-[2-(2,2-difluoroethoxy)ethoxy]-1,1,1-trifluoroethane (F5DEE). A significantly lower overpotential is observed with F2DEM, which improves energy efficiency and enables its application in high-rate conditions. Comparative studies of F2DEM with DEM and F5DEE in anode-free lithium iron phosphate (LiFePO4) LFP pouch cells and high-loading LFP coin cells further show improved capacity retention of F2DEM electrolyte, demonstrating its practical applicability. More importantly, we also extensively investigate the underlying mechanism for the superior performance of F2DEM through various techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, cryogenic electron microscopy, focused ion beam, electrochemical impedance spectroscopy, and titration gas chromatography. Overall, F2DEM facilitates improved Li deposition morphology with reduced amount of dead Li. This enables F2DEM to show superior performance, especially under higher charging and slower discharging rate conditions.

25 ENERGY STORAGE↗