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At least 253 records · Page 14

All sources NASA NTRS DOE OSTI

DOE OSTI2022

Stresses within rare-earth doped yttria-stabilized zirconia thermal barrier coatings from in-situ synchrotron X-ray diffraction at high temperatures

There is a growing interest for smart coatings that can be integrated into turbine engines for in-situ temperature measurements or health monitoring. The addition of rare-earth dopants into standard thermal barrier ceramic top coat materials is used to obtain luminescent coatings that enable spectral measurements, for real-time temperature or health monitoring. The thermomechanical performance and durability of such novel coating compositions in extreme environments still remains to be evaluated. Consequently, the ability to manufacture sensor coatings which present suitable thermal properties needs to be demonstrated. For this study, highly luminescent erbium and europium doped yttria-stabilized zirconia and state-of-the-art yttria-stabilized zirconia coatings manufactured by air plasma spray were characterized to determine the effects of the embedded rareearth dopants on coating internal strain and stress and to quantify and compare their high temperature response using synchrotron X-ray diffraction. In-situ depth-resolved strain measurements were performed at 15 μm intervals along the depth of the coatings to evaluate materials response at key locations, specifically at layer interfaces. In-plane stress was calculated for the coatings and a finite element model was implemented to supplement the results and enable further predictions. The results show that the sensor coatings that were manufactured in this work revealed only minor variations in the strain response of sensor coatings under a typical thermal cycle and especially at temperatures closer to that of gas turbine operating conditions, compared to state-of-the-art coatings. This work demonstrates the viability of manufacturing rare-earth doped yttria-stabilized zirconia coatings that provide beneficial spectroscopic monitoring capabilities while having minimal impact on the thermomechanical response of the thermal barrier coatings.

Air plasma spray↗

NASA NTRS2011

Unintended Consequences: How Qualification Constrains Innovation

The development and implementation of new materials and manufacturing processes for aerospace application is often hindered by the high cost and long time span associated with current qualification procedures. The data requirements necessary for material and process qualification are extensive and often require millions of dollars and multiple years to complete. Furthermore, these qualification data can become obsolete for even minor changes to the processing route. This burden is a serious impediment to the pursuit of revolutionary new materials and more affordable processing methods for air vehicle structures. The application of integrated computational materials engineering methods to this problem can help to reduce the barriers to rapid insertion of new materials and processes. By establishing predictive capability for the development of microstructural features in relation to processing and relating this to critical property characteristics, a streamlined approach to qualification is possible. This paper critically examines the advantages and challenges to a modeling-assisted qualification approach for aerospace structural materials. An example of how this approach might apply towards the emerging field of additive manufacturing is discussed in detail.

Brice, Craig A.↗

DOE OSTI2025

Revisiting the Role of Mobile Ion Size for the Activation Barrier of Charge Transport in Single Ion Conducting Polymers

The development of polymer electrolytes for energy storage and conversion technologies requires a fundamental understanding of the material parameters controlling the energy barriers for ion transport. In glassy polymers, these activation barriers are usually extracted by using Arrhenius procedures. However, our recent studies of single ion conducting polymers reveal that this traditional Arrhenius description provides anomalously small prefactors, an issue that is widely disregarded in the literature. Here, to address it, an alternative approach was introduced for extracting the effective activation barrier E by imposing a physically valid limit (∼10 –13 s) for the ion hopping attempt time. Two consequences of this recent approach are that in polymer electrolytes (i) E is significantly (∼30–40%) lower than the barrier estimated using traditional Arrhenius fits and (ii) E displays significant temperature dependence even in the glassy state. Under these circumstances, we are revisiting the role of ion size, glass transition temperature T g , and dielectric and elastic constants of the polymer matrix on the effective activation barriers for ion transport as extracted using the recently proposed approach and highlight the differences from the picture that previously emerged based on simplistic apparent Arrhenius analysis. To this end, we investigate cation transport in three families of single ion conducting trifluoromethane sulfonimide-based polyanions with varied T g . Our results indicate that E decreases with mobile cation size and is highly sensitive to changes in the dielectric permittivity of the matrix, even for large cations. These insights call for revisions of many earlier results based on apparent Arrhenius fits as the proposed approach can provide more accurate guidance for the design of polymer electrolytes with enhanced ionic conductivity.

energy barrier↗

DOE OSTI2025

Development of an atomic layer deposition system for deposition of alumina as a hydrogen permeation barrier

Tritium permeation into and through materials poses a critical challenge for the development of nuclear fusion reactors. Minimizing tritium permeation is essential for the safe and efficient use of available fuel supplies. In this work, we present the design, construction, and validation of custom atomic layer deposition (ALD) and deuterium permeation measurement systems aimed at developing thin-film hydrogen permeation barriers. Using the ALD system, we deposited conformal $\mathrm{Al}_{2}\mathrm{O}_{3}$ films on copper foil substrates and characterized their growth behavior, morphology, and composition. ALD growth rates of ∼1.1 Å/cycle were achieved for temperatures between 100 ∘ C and 210 ∘ C. Permeation measurements on bare and alumina coated copper foils revealed a significant reduction in deuterium flux with the addition of a ∼10 nm $\mathrm{Al}_{2}\mathrm{O}_{3}$ layer. While bare copper followed diffusion-limited transport consistent with Sievert’s law, the alumina-coated samples exhibited surface-limited, pore-mediated transport with linear pressure dependence. Arrhenius analysis showed distinct differences in activation energy for the two transport regimes, and permeation reduction factors exceeding an order of magnitude were observed. These results demonstrate the potential of ALD-grown $\mathrm{Al}_{2}\mathrm{O}_{3}$ films as effective hydrogen isotope barriers and provide a foundation for future studies on film optimization and integration into fusion-relevant components.

atomic layer deposition↗

DOE OSTI2021

Corrosion of Steel During Long-Term Exposure to Evolving Cementitious Environments

SRS is proceeding with closure of the H-Area Tank Farm (HTF) and F-Area Tank Farm (FTF). Closure consists of removing the bulk waste, heel removal, and filling the tank with tailored grout formulations. The long-term performance of the concrete and steel materials of construction and the closure grout is an important consideration for Performance Assessment (PA) of closed tanks in FTF and HTF. Over PA timeframes of hundreds, thousands, to tens of thousands of years, the chemical and physical properties of the concrete and steel materials will slowly degrade due to environmental exposure and material aging. In the interim these materials will provide a barrier to the leaching of radionuclides into the soil. Savannah River Remediation (SRR) is updating relevant portions of these analysis inputs to support an imminent revision to the HTF PA and a future update to the FTF PA. This analysis provides an update to the previous PA inputs for steel corrosion. The Central Scenario for the PA analysis includes three postulated modeling cases: 1) Realistic Case, 2) Compliance Case, and 3) Pessimistic Case. This analysis also included a Fast Flow Path Case. This latter case considered the circumstance where the initial condition of the concrete was a completely degraded state and that grout shrinkage exposed the steel to the soil environment immediately. In effect, the steel was unprotected by the concrete and grout. The cases have various degrees of conservatism considered. Chemical, physical and tank configuration parameters were investigated to understand their effects on the predicted time to release of the contaminants. The assessment reviewed the initial tank and steel configuration, service life degradation of the steel, and potential corrosion mechanisms associated with degradation of the concrete materials.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

NASA NTRSDate not supplied

Material Compatibility Study of Coated Metals to Maintain Biocidal Silver in a Spacecraft Potable Water System

Ionic silver-based biocide remains an option of choice for microbial control in spacecraft potable water systems. However, depletion of silver ions by wetted materials readily reduces ionic silver to nonbiocidal levels. This phenomenon occurs via various transport mechanisms at the liquid-solid interfaces between the silver-containing water and adjacent surfaces. Consequently, challenges remain in the design and/or selection of materials that can be used for the wetted system components that will help ensure silver is maintained at biocidal levels. Since silver has been baselined, and/or remains, as a potable water biocide option for several future spacecraft potable water systems, a multitiered approach is being investigated, looking at heritage materials, new processes, and/or alterative materials. This study conducted the application of eleven chemically-resistant coatings onto coupons that were cut out from three types of spacecraft-grade metals (Titanium Grade 2, Inconel 718, and 316L Stainless Steel) to investigate the performance of this material strategy as a barrier against silver depletion. In this investigation, the coated metals were immersed in a static 400 parts per billion silver biocide solution at a surface-area-to-volume ratio of 2.0 cm^(-1) and left to soak for predefined time periods. The concentration of the solution in contact with the coated samples was analyzed at various points via inductively coupled plasma mass spectrometry, and the measurements were interpreted as silver retention percentages over time. This paper summarizes the coating selection process, the configuration of the test, and the performance of each coating-metal combination at diminishing silver depletion. The preliminary results demonstrate that some of the selected coatings succeeded at maintaining biocidal silver concentrations far beyond the corresponding base metal in a similar test. The knowledge acquired through this investigation supports the deploying of coatings on plumbing lines for the integration of biocidal silver in the water system architecture of a spacecraft. Nevertheless, further testing must be continued to assess the performance of these coatings on other wetted geometries and any implications of unifying this material strategy with traditional and developmental engineering design processes for spacecraft potable water systems.

water↗

DOE OSTI2019

Modeling of dielectric function in plasmonic quantum dot nanolaser

In this work we present a model of the dielectric function in plasmonic quantum dot (QD) nanolaser. A metal/semiconductor/metal structure was considered to attain plasmonic nanocavity with active region containing: QD, wetting layer and barrier. The dielectric function was calculated for both metal (Ag) and QD structure. The propagation constant of surface plasmon polariton (SPP) at the interface of Ag/InAs-QD structure was calculated and the dispersion relation of the plasmonic QD structure was evaluated. For frequencies far from plasma one, the gap between real and imaginary parts was large and a deviation from linear relation was obvious. The SPP field was strongly localized at the interface due to the effect of zero-dimensional QD structure which has application in the super-resolution and best sensitivity in optical imaging. Results of propagation length of SPP (L{sub spp}) also support this. According to the L{sub spp} results, the damping in the SPP energy was low in the Ag/InAs-QD compared to that in the Ag/air interface. The obtained results are in the range of experimental ones.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS2001

Automated Fiber Placement of PEEK/IM7 Composites with Film Interleaf Layers

The incorporation of thin discrete layers of resin between plies (interleafing) has been shown to improve fatigue and impact properties of structural composite materials. Furthermore, interleafing could be used to increase the barrier properties of composites used as structural materials for cryogenic propellant storage. In this work, robotic heated-head tape placement of PEEK/IM7 composites containing a PEEK polymer film interleaf was investigated. These experiments were carried out at the NASA Langley Research Center automated fiber placement facility. Using the robotic equipment, an optimal fabrication process was developed for the composite without the interleaf. Preliminary interleaf processing trials indicated that a two-stage process was necessary; the film had to be tacked to the partially-placed laminate then fully melted in a separate operation. Screening experiments determined the relative influence of the various robotic process variables on the peel strength of the film-composite interface. Optimization studies were performed in which peel specimens were fabricated at various compaction loads and roller temperatures at each of three film melt processing rates. The resulting data were fitted with quadratic response surfaces. Additional specimens were fabricated at placement parameters predicted by the response surface models to yield high peel strength in an attempt to gage the accuracy of the predicted response and assess the repeatability of the process. The overall results indicate that quality PEEK/lM7 laminates having film interleaves can be successfully and repeatability fabricated by heated head automated fiber placement.

Hulcher, A. Bruce↗

NASA NTRS2017

A Novel Solid State Ultracapacitor

Novel dielectric materials were researched to develop an internal barrier layer capacitor that is fully solid state. These materials included reduced nanoparticles of barium titanate that were coated with various atomic layer deposited oxides. The nanoparticle powders were then densified into pellets and characterized using a dielectric test fixture over a frequency range of 20 Hz to 2 MHz. Densification and sintering were evaluated using scanning electron microscopic techniques. Ultimately, the samples showing the most promising electrical characteristics of permittivity, dissipation factor and equivalent series resistance were chosen to manufacture devices for subsequent testing.

Cortes-Pena, A. Y.↗

DOE OSTI2020

Low Energy Implantation into Transition-Metal Dichalcogenide Monolayers to Form Janus Structures

Atomically-thin two-dimensional (2D) materials face significant energy barriers for synthesis and processing into functional metastable phases such as Janus structures. Here, in this study, the controllable implantation of hyperthermal species from pulsed laser deposition (PLD) plasmas is introduced as a top-down method to compositionally engineer 2D monolayers. The kinetic energies of Se clusters impinging on suspended monolayer WS 2 crystals were controlled in the <10 eV/atom range with in situ plasma diagnostics to determine the thresholds for selective top layer replacement of sulfur by selenium for the formation of high quality WSSe Janus monolayers at low (300 °C) temperatures, and bottom layer replacement for complete conversion to WSe 2 . Atomic-resolution electron microscopy and spectroscopy in tilted geometry confirm the WSSe Janus monolayer. Molecular dynamics simulations reveal that Se clusters implant to form disordered metastable alloy regions, which then recrystallize to form highly ordered structures, opening the door for low-energy implantation by PLD as a novel method to explore the synthesis of 2D Janus layers and alloys of variable composition.

2D materials↗

DOE OSTI2021

Characterization of Materials Used as Face Coverings for Respiratory Protection

Use of masks is a primary tool to prevent the spread of the novel COVID-19 virus resulting from unintentional close contact with infected individuals. However, detailed characterization of the chemical properties and physical structure of common mask materials is lacking in the current literature. In this study, a series of commercial masks and potential mask materials, including 3M Particulate Respirator 8210 N95, a material provided by Oak Ridge National Laboratory Carbon Fiber Technology Facility (ORNL/CFTF), and a Filti Face Mask Material, were characterized by a suite of techniques, including scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Wetting properties of the mask materials were quantified by measurements of contact angle with a saliva substitute. Mask pass-through experiments were performed using a dispersed metal oxide nanoparticle suspension to model the SARS-CoV-2 virus, with quantification via spatially resolved X-ray fluorescence mapping. Notably, all mask materials tested provided a strong barrier against respiratory droplet breakthrough. The comparisons and characterizations provided in this study provide useful information when evaluating mask materials for respiratory protection.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Porous architecture and thermal properties of thermal barrier coatings deposited by suspension plasma spray

Besides the intrinsic low heat transfer capability of material, the thermal insulation property of thermal barrier coatings (TBCs) also relies on their microstructures. For better understanding the relationship between process parameters, porous architecture, and thermal properties of coatings, YSZ coatings were firstly manufactured by suspension plasma spray (SPS). Afterwards their total porosities were characterized by using the technique of X-ray transmission, the nano/submicro pores in those coatings were detected with Ultra-Small Angle X-ray Scattering (USAXS), and the thermal properties of coatings were measured using the laser flash method. The results indicated that: i) the porous architecture of SPS coatings can be tailored by adapting process parameters. ii) increasing total porosity is an effective means for reducing the heat transfer capability of SPS coatings. iii) nano/submicro pores have higher influence sensitivity on thermal properties than that of larger pores. Increasing the content of nano-submicro pores is therefore more effective for improving the thermal insulation property of SPS coatings. The potential of SPS technique for fabricating TBCs was discussed as well.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Breakthrough innovations in carbon dioxide mineralization for a sustainable future

Greenhouse gas emissions and climate change concerns have prompted worldwide initiatives to lower carbon dioxide (CO 2 ) levels and prevent them from rising in the atmosphere, thereby controlling global warming. Effective CO 2 management through carbon capture and storage is essential for safe and permanent storage, as well as synchronically meeting carbon reduction targets. Lowering CO 2 emissions through carbon utilization can develop a wide range of new businesses for energy security, material production, and sustainability. CO 2 mineralization is one of the most promising strategies for producing thermodynamically stable solid calcium or magnesium carbonates for long-term sequestration using simple chemical reactions. Current advancements in CO 2 mineralization technologies, focusing on pathways and mechanisms using different industrial solid wastes, including natural minerals as feedstocks, are briefly discussed. However, the operating costs, energy consumption, reaction rates, and material management are major barriers to the application of these technologies in CO 2 mineralization. Further, the optimization of operating parameters, tailor-made equipment, and smooth supply of waste feedstocks require more attention to make the carbon mineralization process economically and commercially viable. Here, carbonation mechanisms, technological options to expedite mineral carbonation, environmental impacts, and prospects of CO 2 mineralization technologies are critically evaluated to suggest a pathway for mitigating climate change in the future. The integration of industrial wastes and brine with the CO 2 mineralization process can unlock its potential for the development of novel chemical pathways for the synthesis of calcium or magnesium carbonates, valuable metal recovery, and contribution to sustainability goals while reducing the impact of global warming.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Metallographic examinations and hydrogen measurements of high-burnup spent nuclear fuel cladding

In the US, commercial spent nuclear fuel (SNF) is transferred to interim dry storage casks where it will be stored for decades awaiting transport to a consolidated interim storage facility or a geologic repository. Because the fuel rod cladding is the first barrier against any radioactive material release, understanding the behavior of SNF cladding, particularly at high burnup (HBU), in dry storage conditions is crucial to safely store and transport the spent fuel. In this study, a series of metallographic examinations and cladding hydrogen measurements were conducted on HBU SNF cladding at Oak Ridge National Laboratory as a part of the High Burnup Spent Fuel Data Project, which is sponsored by the US Department of Energy (DOE) Office of Nuclear Energy (NE). Here, t o investigate the effect of simulated drying conditions on the cladding, three as-received fuel rods with different cladding materials—M5, ZIRLO, and Zircaloy-4—were heated to 400°C and then slow-cooled to room temperature. The pellet and cladding were then qualitatively and quantitatively analyzed and compared in terms of pellet crack morphology, HBU rim, waterside oxide, cladding H, and cladding hydride morphologies. This paper presents and discusses the results of these analyses in detail.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Effect of Molecular Weight and Layer Thickness on Dielectric Breakdown Strength of Neat and Homopolymer Swollen Lamellar Block Copolymer Films

Designing next-generation lightweight pulsed power devices hinges on understanding the factors influencing the energy storage performance of dielectric materials. Polymer dielectric films have a quadratic dependence of energy storage on the voltage breakdown strength and strategies to enhance the breakdown strength are expected to yield a path toward high energy storage densities. Highly stratified lamellar block copolymer (L-BCP) films of model polystyrene-b-polymethylmethacrylate (PS-b-PMMA) exhibited as much as ~50% enhancement in breakdown voltage (E BD ), (225 % increase in stored energy density, U~ E BD 2 ), compared to unordered as-cast L-BCP films. Such an energy density using amorphous polymer is on par with industry-standard semi-crystalline biaxially oriented polypropylene (BOPP), and as such a notable development in the field. This work develops a deeper understanding of the molecular mechanisms of E BD enhancement in L-BCP films, due to combination of interface formation and spatial isolation of the chain ends into segregated zones. We further confirm the role of chain ends in the breakdown process blending a low M n L-BCP with matched M n homopolymers to attain same layer spacing as neat L-BCP of higher M n . E BD shows a significant decrease at low homopolymer fractions due to increased net chain end density within swollen ordered L-BCP domains in wet-brush regime, followed by increased E BD due to layer thickness increase via segregated “interphase layer” formation by excess homopolymers. Notably, E BD of homopolymer swollen L-BCPs is always lower than neat L-BCP of the same domain spacing, due to overall adverse chain ends contribution from homopolymers. These findings provide important selection rules for L-BCPs for designing next-generation flexible electronics with high energy density solid-state BCP film capacitors.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Simulations of three-layer Richtmyer–Meshkov mixing in a shock tube

Here, the Richtmyer–Meshkov instability causes perturbations to grow after a shock traverses a fluid density interface. This increases the mixing rate between fluid from either side of the interface. We use the Flash Eulerian hydrodynamic code to investigate alterations when a thin third layer of intermediate density is placed along the interface, effectively creating two adjacent unstable interfaces. This is a common occurrence in engineering applications where a thin barrier initially separates two materials. We find that the width of the mixing layer is similar or slightly reduced; however, the total mass of mixed material can actually increase. The mixing layer becomes more compact and efficient. However, the normalized mixed mass decreases, meaning that finger entrainment becomes more important than in the simple two-layer case. The effect of adding the central layer appears to decrease when the Atwood number is decreased. The Flash results are also benchmarked against two-layer experimental data from a shock tube at the University of Arizona.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2022

Mixed Plastics Waste Valorization through Tandem Chemical Oxidation and Biological Funneling

Mixed plastics waste represents an abundant and largely untapped feedstock for the production of valuable products. The chemical diversity and complexity of these materials, however, present major barriers to realizing this opportunity. In this work, we show that metal-catalyzed autoxidation depolymerizes comingled polymers into a mixture of oxygenated small molecules that are advantaged substrates for biological conversion. We engineer a robust soil bacterium, Pseudomonas putida, to funnel these oxygenated compounds into a single exemplary chemical product, either ..beta..-ketoadipate or polyhydroxyalkanoates. This hybrid process establishes a strategy for the selective conversion of mixed plastics waste into useful chemical products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Understanding the Challenges of Financing Modular Construction: A Case Study for Prospective Multifamily Units

Compared to traditional site build, modular construction can significantly shorten construction schedules and speed income generation. Modular construction may also reduce construction costs. Yet access to commercial financing remains one of the most significant barriers to modular construction. Materials must be purchased, and production lines reconfigured for each project months ahead of fabrication. Materials alone can be 60% or more of the total cost of production. As a result, manufacturers require large upfront deposits—often 30% or more of the off-site contract. In addition, the capital-intensive nature of modular construction requires frequent progress payments for manufacturers to maintain cash flow. For those lenders willing to fund modular projects, many require the developer to share more of the risk. This may include the developer paying for line reservation fees and material deposits 3–6 months prior to production. Because these are unsecured loans, interest rates may be higher and loan amounts lower. As suppliers, modular manufacturers discourage retainage. Together, these and other factors may contribute to higher equity requirements for the developer—particularly at the beginning of the project.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗