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At least 289 records · Page 16

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NASA NTRSDate not supplied

Wear-Resistance Investigations on Ceramic Coatings for Lunar Dust Mitigation

Lunar dust has posed a major challenge to exploration efforts due to abrasion and impact. This work focuses on fundamental studies on ceramic coatings as candidates for enhanced resistance to impact and wear. As a first step, standard and modified approaches to the method of abrasion testing were explored for options to incorporate lunar regolith as wear media, the effects of which were presented for AL6061-T6 control samples. Following this, wear results for air plasma-sprayed (APS) alumina coatings were investigated due to their superior strength and surface hardness. In addition, APS 8 wt % yttria-stabilized zirconia (8YSZ) coatings were studied for their strength and martensitic transformation toughness. Measurements were made by assessing the mass loss, with a standard scale at various intervals. In addition, surface roughness was measured with a profilometer and features identified with a high-resolution microscope. The findings demonstrated that wear media has a distinct effect on the abrasion. The alumina coatings demonstrated improved wear over 8YSZ. However, the tailorability of 8YSZ makes it an attractive option to continue to modify as a wear-resistant coating to protect against lunar dust abrasion. The results of these measurements provide insight into the wear behavior of future directions in candidate ceramic coatings for the harsh lunar environment.

ceramic coatings↗

NASA NTRSDate not supplied

Wear-Resistance Investigations on Ceramic Coatings for Lunar Dust Mitigation

ceramic coatings↗

DOE OSTI2025

Emerging Per- and Polyfluoroalkyl Substances in Tap Water from the American Healthy Homes Survey II

Humans experience widespread exposure to anthropogenic per- and polyfluoroalkyl substances (PFAS) through various media, which can lead to a wide range of negative health impacts. Tap water is an important source of exposure in communities with any degree of contamination but routine or large-scale PFAS monitoring often depends on targeted analytical methods limited to measuring specific PFAS. We analyzed 680 tap water samples from the American Healthy Homes Survey II for PFAS using non-targeted analysis (NTA) to expand the range of detectable PFAS. Based on detection frequency and relative abundance, about half of the identified PFAS were found only by NTA. We identified (with varying degrees of confidence) 75 distinct PFAS, including 57 exclusively detected by NTA. The identified PFAS are members of seven structural subclasses differentiated by their head groups and degree of fluorination. Clustering analysis categorized the PFAS into four coabundance groups dominated by specific PFAS subclasses. One group uniquely identified by NTA contains zwitterionic PFAS and other PFAS transformation products which are likely associated with aqueous firefighting foam contaminants in a small number of spatially correlated samples. These results help further characterize the scope of exposure to emerging PFAS experienced by the U.S. population via tap water and augment nationwide targeted-PFAS monitoring programs.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗

DOE OSTI2024

Exploring Object Detection and Image Classification Tasks for Niche Use Case in Naturalistic Driving Studies

Naturalistic driving studies consist of drivers using their personal vehicles and provide valuable real-world data, but privacy issues must be handled very carefully. Drivers sign a consent form when they elect to participate, but passengers do not for a variety of practical reasons. However, their privacy must still be protected. One large study includes a blurred image of the entire cabin which allows reviewers to find passengers in the vehicle; this protects the privacy but still allows a means of answering questions regarding the impact of passengers on driver behavior. A method for automatically counting the passengers would have scientific value for transportation researchers. We investigated different image analysis methods for automatically locating and counting the non-drivers including simple face detection and fine-tuned methods for image classification and a published object detection method. We also compared the image classification using convolutional neural network and vision transformer backbones. Our studies show the image classification method appears to work the best in terms of absolute performance, although we note the closed nature of our dataset and nature of the imagery makes the application somewhat niche and object detection methods also have advantages. We perform some analysis to support our conclusion.

Peruski, Ryan↗

NASA NTRS2004

On-Orbit Repair of RCC Structures

On-orbit repair technologies for reinforced carbon-carbon composite (RCC) structures are critically needed for space shuttle return to flight (RTF) efforts. These technologies are also critically needed for the repair and refurbishment of thermal protection system of future Crew Entry Vehicles (CEV) of space exploration programs. GRABER (Glenn Adhesive Refractory for Bonding and Exterior Repair) has shown multiuse capability for in-space repair of both large repairs and small cracks in space shuttle Reinforced Carbon Carbon (RCC) leading edge material. The concept consists of preparing an adhesive paste and then applying the paste tot he damaged/cracked area of the RCC composites with caulking gun. The adhesive paste cures at 100-120 C and transforms into a high temperature ceramic during vehicle re-entry conditions. Further development and testing are underway to optimize the materials properties and extend the application temperature.

Singh, M.↗

DOE OSTI2021

Revealing the etching process of water-soluble Au 25 nanoclusters at the molecular level

Etching (often considered as decomposition) is one of the key considerations in the synthesis, storage, and application of metal nanoparticles. However, the underlying chemistry of their etching process still remains elusive. Here, we use real-time electrospray ionization mass spectrometry to study the reaction dynamics and size/structure evolution of all the stable intermediates during the etching of water-soluble thiolate-protected gold nanoclusters (Au NCs), which reveal an unusual “recombination” process in the oxidative reaction environment after the initial decomposition process. Interestingly, the sizes of NC species grow larger and their ligand-to-metal ratios become higher during this recombination process, which are distinctly different from that observed in the reductive growth of Au NCs (e.g., lower ligand-to-metal ratios with increasing sizes). The etching chemistry revealed in this study provides molecular-level understandings on how metal nanoparticles transform under the oxidative reaction environment, providing efficient synthetic strategies for new NC species through the etching reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2017

It's All Relative: A Validation of Radiation Quality Comparison Metrics

The difference between high-LET and low-LET radiation is quantified by a measure called relative biological effectiveness (RBE). RBE is defined as the ratio of the dose of a reference radiation to that of a test radiation to achieve the same effect level, and thus, is described either as an iso-effector dose-to-dose ratio. A single dose point is not sufficient to calculate an RBE value; therefore, studies with only one dose point usually calculate an effect-to-effect ratio. While not formally used in radiation protection, these iso-dose values may still be informative. Shuryak, et al 2017 investigated the use of an iso-dose metric termed "radiation effects ratio" (RER) and used both RBE and RER to estimate high-LET risks. To apply RBE or RER to risk prediction, the selected metric must be uniquely defined. That is, the calculated value must be consistent within a model given a constant set of constraints and assumptions, regardless of how effects are defined using statistical transformations from raw endpoint data. We first test the RBE and the RER to determine whether they are uniquely defined using transformations applied to raw data. Then, we test whether both metrics can predict heavy ion response data after simulated effect size scaling between human populations or when converting animal to human endpoints.

Chappell, Lori J.↗

NASA NTRSDate not supplied

Integration of Advanced Structures and Materials Technologies for a Robust Lunar Habitat

NASA’s Artemis program plans to have a sustainable lunar base deployed on the Moon by 2028. The base calls for a foundation surface habitat that can support a crew of four members for a minimum mission duration of 28-days. The lack of a magnetic field and significant lunar atmosphere extends the lifetime of secondary radiation emitted from metallic structures, which is a health hazard for exposed astronauts. Integration of non-metallic structural materials into surface habitat design may alleviate some of these concerns. Additionally, it is favorable for the structure to be collapsible for transportation to optimize payload volume, mass efficiency, and monetary constraints. As a result, inflatable structures are being investigated due to their improved packing efficiency at launch, optimal mass-to-volume ratio, and large surface area that can efficiently disperse structural loads and heat. Currently, only two inflatable airlocks have been deployed in space. Thus, there is a significant need to advance technologies associated with inflatable structures to provide greater options for future missions, i.e., Artemis and beyond. This study focused on the inflatable lunar habitat applications of emerging NASA Langley Research Center (LaRC) technologies and their required development steps to become space qualified. The Bowling Habitat architecture was generated from 13 of these NASA LaRC technologies, five of which were deemed critical, five determined as enhancing technologies, and three were classified as transformational technologies for the Artemis program. To address the payload constraints, the study also considered a tentative timeline that aligned with the current Artemis schedule for transporting the Bowling Habitat to the Moon. Ultimately, the Bowling Habitat mainly addressed the structural needs of an inflatable lunar habitat, meaning that major areas pertaining to the life-style aspects of the habitat must be improved. Areas include, but are not limited to, hard connection points, the monitoring of human health, and extra radiation protection for solar proton events.

Inflatable Habitat↗

DOE OSTI2024

Online Molten Salt and Gas Monitoring Using Combined Spectroscopic Methods

The nonproliferation of nuclear material and the development of safeguards technologies to sample and analyze fuel salt is a challenge for molten salt reactor (MSR) developers. We seek online monitoring using combined spectroscopic methods of two distinct material phases from MSR’s. Molten salt transformed to aerosol phase allows for Light Induced Breakdown spectroscopy (LIBS) without adverse splashing (ARPA-E). Vaporized used nuclear fuel through chlorine-based volatility (CBV) allows for uranium separation based on boiling point differences

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗

DOE OSTI2022

Chemical compatibility of hollow ceramic cenospheres as thermal insulation for high-temperature thermal energy storage applications with molten nitrate salt

An effective insulation material that is both thermally and chemically stable in molten salts could transform the design of molten-salt-based thermal energy storage (TES) tanks. Most current molten salt TES tanks hold the metallic tank structure in direct contact with hot salt inventory, a design which leads to thermal expansion of the tank and triggers stresses that can lead to thermomechanical failures. With an internal insulation to lower the temperature at the tank structure, the extent of thermal expansion can be reduced, thereby reducing expansion-induced stresses and allowing for consideration of lower-cost tank structure materials. Conventional insulation materials are either 1) too porous and allow molten salts to permeate into the matrix, which significantly increases the thermal conductivity or 2) too dense and have a thermal conductivity that cannot provide sufficient thermal insulation. This paper presents an alternative thermal insulation concept using cenospheres which have an alumino-silicate structure. The cost analysis suggests that the low-density cenospheres can be one of the cheapest materials to provide cost-effective thermal insulation. The chemical compatibility of cenospheres is investigated in molten 60 wt% NaNO3/40 wt% KNO3 salt which is close to industrial-grade Solar Salt. This paper shows that diffusion of the sodium and potassium cations from the salt into the cenospheres occurs based on weight analysis, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The cation diffusion breaks the bridging oxygen bonds and causes volume expansion of the microstructure which is responsible for the failure of the cenosphere particles. The chemical composition of the cenospheres is found to affect their compatibility with molten nitrate salt. A cenosphere product with low iron content showed the best compatibility with an average survival rate of 77.9% +/- 9.8% after 7 days of immersion in the molten nitrate salt. While even the low-iron cenospheres appear to require protection from direct molten salt contact, their slow degradation rate, closed-cell porosity, and low cost hold potential for effective use as internal tank insulation.

14 SOLAR ENERGY↗

NASA NTRS2015

Environmentally-Preferable Launch Coatings

The Ground Systems Development and Operations (GSDO) Program at NASA Kennedy Space Center (KSC), Florida, has the primary objective of modernizing and transforming the launch and range complex at KSC to benefit current and future NASA programs along with other emerging users. Described as the launch support and infrastructure modernization program in the NASA Authorization Act of 2010, the GSDO Program will develop and implement shared infrastructure and process improvements to provide more flexible, affordable, and responsive capabilities to a multi-user community. In support of NASA and the GSDO Program, the objective of this project is to determine the feasibility of environmentally friendly corrosion protecting coatings for launch facilities and ground support equipment (GSE). The focus of the project is corrosion resistance and survivability with the goal to reduce the amount of maintenance required to preserve the performance of launch facilities while reducing mission risk. The project compares coating performance of the selected alternatives to existing coating systems or standards.

ground support equipment↗

NASA NTRSDate not supplied

Three Dimensionally Woven Mid-Density Carbon Phenolic (3MDCP) is a Novel Single Piece Ablative TPS for Extreme Entry Environments

Three Dimensionally Woven Mid-Density Carbon Phenolic (3MDCP) is robust, single piece, carbon phenolic ablative thermal protection system under development at NASA Ames Research Center initially for the Mars Sample Return Earth Entry System (MSR EES). The MSR EES requirements drove the need for TPS with no seams, capable of surviving the highest entry conditions for any NASA Earth return capsule with heat fluxes >2000 W/cm2 and pressures >1.5 atmospheres. To produce 3MDCP required development of new weaving infrastructure to enable weaving of preforms large enough to form into a single piece heatshield. It required development of forming techniques to transform a flat woven panel into a sphere cone shape and enhanced infusion processes to support larger scale infusion of resin into the formed preforms. A rigorous performance testing campaign was conducted to develop and validate the materials thermal response model used to determine the required material thickness and to demonstrate the material can survive the extreme entry conditions. The end of the development effort (end of FY26) will result in a TPS at Technical Readiness Level (TRL) 6 and Manufacturing Readiness Level (MRL) 6+ for the MSR EES mission and a mature system ready to support other missions. This poster will provide a snapshot of where 3MDCP is in its development phase.

Ablator↗

NASA NTRS2009

Ultra-high Temperature Emittance Measurements for Space and Missile Applications

Advanced modeling and design efforts for many aerospace components require high temperature emittance data. Applications requiring emittance data include propulsion systems, radiators, aeroshells, heatshields/thermal protection systems, and leading edge surfaces. The objective of this work is to provide emittance data at ultra-high temperatures. MSFC has a new instrument for the measurement of emittance at ultra-high temperatures, the Ultra-High Temperature Emissometer System (Ultra-HITEMS). AZ Technology Inc. developed the instrument, designed to provide emittance measurements over the temperature range 700-3500K. The Ultra-HITEMS instrument measures the emittance of samples, heated by lasers, in vacuum, using a blackbody source and a Fourier Transform Spectrometer. Detectors in a Nicolet 6700 FT-IR spectrometer measure emittance over the spectral range of 0.4-25 microns. Emitted energy from the specimen and output from a Mikron M390S blackbody source at the same temperature with matched collection geometry are measured. Integrating emittance over the spectral range yields the total emittance. The ratio provides a direct measure of total hemispherical emittance. Samples are heated using lasers. Optical pyrometry provides temperature data. Optical filters prevent interference from the heating lasers. Data for Inconel 718 show excellent agreement with results from literature and ASTM 835. Measurements taken from levitated spherical specimens provide total hemispherical emittance data; measurements taken from flat specimens mounted in the chamber provide near-normal emittance data. Data from selected characterization studies will be presented. The Ultra-HITEMS technique could advance space and missile technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials.

Rogers, Jan↗

DOE OSTI2020

Ammonia Permeation Through Inorganic Membranes

Moisture probes are used in the tritium facility to measure the moisture content of the gas stream. When tritium reacts with nitrogen to form ammonia, the ammonia gas damages the sensitive moisture probe. The gas stream tested during this experiment for moisture probe protection is composed of nitrogen and argon gas in conjunction with ammonia and water vapor. The gas stream is filtered through an inorganic membrane due to the high reactivity of tritium and a residual gas analyzer (RGA) is used to measure the ammonia and water vapor in the gas stream, as well as the permeability of nitrogen and argon through the inorganic membranes. The membranes tested were boron nitride and silver. The permeability was compared for each membrane at different pressures and flow rates. Fourier-transformed infrared spectroscopy (FT-IR) was used to compare the membranes before and after ammonia permeation. Ammonia gas is a byproduct formed from tritium gas reacting with nitrogen in the gas stream, similar to the Haber Process which occurs when hydrogen reacts with nitrogen [2]. The corrosive nature of ammonia damages metals and sensitive instruments such as moisture probes. Moisture probes are essential in various gas and liquid processes for measuring the moisture content of a gas. Membrane research has found that graphene oxide membranes successfully uptake ammonia from the gas stream at a humidity of approximately 30% at which point the pores pin closed, preventing gas permeation. Further research is being conducted to find an inorganic membrane that will prevent ammonia permeation thus circumventing damage to the sensitive moisture probe. The permeation measurements for argon and nitrogen gas and water and ammonia vapor were measured at various pressures of 800, 1000, 1200, 1500, 1800, and 2000 torr. The permeability average (PA) was calculated for each filter using a Barrer calculation. The average permeations for each filter were then compared. The gas composition was measured using the RGA Nitrogen was permeated through the membranes after ammonia permeation and a FT-IR spectrum was obtained. Boron Nitride: As the nitrogen pressure increased, the permeability of the membrane decreased from 800-1200 torr and remained relatively unchanged from 1200-2000 torr. The membrane exhibited a slight decrease in argon permeability from 800-1200 torr and a slight increase from 1500-2000 torr. The boron nitride membrane when permeated with ammonia and nitrogen prevented less ammonia permeation compared to the blank filter. The boron nitride filter demonstrated a decrease in permeability after ammonia permeation. Silver Membrane: When permeated with nitrogen alone, the membrane permeability decreased from 800 torr to 1200 torr. The permeability of the membrane showed little difference as pressure increased from 1200 torr. When permeated with argon, the same phenomenon occurred but on a much smaller scale. When compared to the blank and the boron nitride membranes the silver membrane exhibited significantly lower permeability. This may be in part due to the coating on the silver membrane and differences in pore size of the membranes. During permeation with ammonium hydroxide vapor and nitrogen, the partial pressure of the ammonia increased as compared to the blank membrane. The permeability before and after permeation with ammonia and nitrogen were compared. Permeability values suggested that after being permeated with the ammonia that the permeability for lower pressures increased slightly. There was no significant change in the FT-IR spectrums before and after permeation. Future work: Continue testing various inorganic membranes for ammonia permeation. Further research chemical separation of ammonia from the gas stream, which may prove difficult due to the high reactivity of tritium.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2004

Method of Fabricating Protective Coating for a Crucible with the Coating Having Channels Formed Therein

A method is provided for the fabrication of a protective coating for a crucible with channels being formed in the coating. A material is adhered to the outer wall of the crucible to form a pattern thereon. The outer wall of the crucible along with the pattern of material adhered thereto is next coated with another material. The material used to form the pattern should extend through the outer material coating to define at least one port therein. Next, the crucible with its pattern of material and outer coating material is heated to a temperature of transformation at which the pattern of material is transformed to a fluidic state while the crucible and outer coating material maintain their solid integrity. Such transformation could also be accomplished by using a solvent that causes the pattern of material to dissolve. Finally, the material in its fluidic state is removed via the at least one port formed in the outer material coating thereby leaving channels defined in the coating adjacent the outer wall of the crucible.

Richard N Grugel↗

NASA NTRS2011

The Potential Impact of CO2 and Air Temperature Increases on Krummholz's Transformation into Arborescent Form in the Southern Siberian Mountains

Trees in the southern Siberian Mountains forest-tundra ecotone have considerably increased their radial and apical growth increments during the last few decades. This leads to the widespread vertical transformation of mat and prostrate krummholz forms of larch (Larix sibirica Ledeb) and Siberian pine (Pinus sibirica Du Tour). An analysis of the radial growth increments showed that these transformations began in the mid-1980s. Larch showed a greater resistance to the harsh alpine environment and attained a vertical growth form in areas where Siberian pine is still krummholz. Upper larch treeline is about 10 m higher than Siberian pine treeline. Observed apical and radial growth increment increases were correlated with CO2 concentration (r = 0.83-0.87), summer temperatures (r = 0.55-0.64), and "cold period" (i.e. September-May) air temperatures (r = 0.36-0.37). Positive correlation between growth increments and winter precipitation was attributed to snow cover protection for trees during wintertime.

Kharuk, V. I.↗

DOE OSTI2022

Synthesis of Hf 6 Ta 2 O 17 superstructure via spark plasma sintering for improved oxidation resistance of multi-component ultra-high temperature ceramics

Ultra-high temperature ceramics (UHTCs) have shown aspiration to overcome challenges in the thermal protection system (TPS) by designing new materials referred to as multi-component UHTCs (MC-UHTCs) in the compositional space. MC-UHTCs have shown remarkable improvement in oxidation resistance due to the formation of the Hf6Ta2O17 superstructure during plasma exposure. Herein, the Hf 6 Ta 2 O 17 superstructure is synthesized via a solid-state reaction between HfO 2 and Ta 2 O 5 powder mixtures during spark plasma sintering (SPS). The compositions chosen are 50 vol% of HfO 2 -50 vol% of Ta 2 O 5 (50HO-50TO) and 70 vol% of HfO 2 -30 vol% of Ta 2 O 5 (70HO-30TO). The phase quantification via Rietveld analysis showed Hf 6 Ta 2 O 17 as a principal phase with some residual Ta 2 O 5 phase in both the samples. The high-temperature thermal stability of the samples was evaluated using high-velocity plasma jet exposure for up to 3 min. 50HO-50TO was able to withstand the intense plasma condition, which is attributed to the higher content of the Hf 6 Ta 2 O 17 phase (~84%) and lower strain in the Ta 2 O 5 phase. The augmentation in the Hf 6 Ta 2 O 17 phase to 94.7% (in 50HO-50TO) post plasma exposure has been attributed to the invariant transformation from a liquid state to Hf 6 Ta 2 O 17 at temperatures >2500 °C during testing. The mechanical integrity is elucidated from the insignificant change in the hardness ~13.3 GPa before and 11.2 GPa after plasma exposure of the 50HO-50TO sample. As a result, the Hf 6 Ta 2 O 17 superstructure's thermo-mechanical stability suggests developing novel oxidation-resistant MC-UHTCs in compositional space for reusable space vehicle applications.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Finite Element Modeling of the Phase Change in Thermally-Grown SiO 2 in SiC Systems for Gas Turbines

The operating lifetimes of SiC-based components in combustion environments are directly linked to the adhesion of the protective environmental barrier coating (EBC) layer. One of the major known failure modes for EBCs is the formation of a thick SiO 2 thermally grown oxide (TGO), which decreases coating adhesion and encourages eventual coating spallation. The effect of the TGO thickness under Yb 2 Si 2 O 7 EBCs on silicon carbide was investigated using finite element models (FEMs) with various interfacial architectures and SiO 2 TGO thicknesses. Further, the FEMs incorporated a user-defined material to simulate the volume contraction of the TGO during the silica phase transformation from β-cristobalite to α-cristobalite upon cooling from the stress-free state at 1350°C to room temperature. Systems with and without a silicon bond coating intermediary layer were assessed. It was shown that the TGO phase transformation stress (1.6–1.7 GPa) dominated the increase in stress in the TGO and EBC layers. Furthermore, it was found that stress increase in the TGO was independent of TGO thickness and interface geometry. These results indicate that stabilization of the TGO to mitigate the phase transformation could dramatically improve the performance of SiC-base components with EBCs.

36 MATERIALS SCIENCE↗