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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Effect of Diel Cycling Temperature, Relative Humidity, and Synthetic Route on the Surface Morphology and Hydrolysis of α -U 3 O 8

The speciation and morphological changes of α-U 3 O 8 following aging under diel cycling temperature and relative humidity (RH) have been examined. This work advances the knowledge of U-oxide hydration as a result of synthetic route and environmental conditions, ultimately giving novel insight into nuclear material provenance. α-U 3 O 8 was synthesized via the washed uranyl peroxide (UO 4 ) and ammonium uranyl carbonate (AUC) synthetic routes to produce unaged starting materials with different morphologies. α-U 3 O 8 from UO 4 is comprised of subrounded particles, while α-U 3 O 8 from AUC contains blocky, porous particles approximately an order of magnitude larger than particles from UO 4 . For aging, a humidity chamber was programmed for continuous daily cycles of 12 “high” hours of 45 °C and 90% RH, and 12 “low” hours of 25 °C and 20% RH. Samples were analyzed at varying intervals of 14, 24, 36, 43, and 54 days. At each aging interval, crystallographic changes were measured via powder X-ray diffraction coupled with whole pattern fitting for quantitative analysis. Morphologic effects were studied via scanning electron microscopy and 12-way classification via machine learning. While all samples were found to have distinguishing morphologic characteristics (93.2% classification accuracy), α-U 3 O 8 from UO 4 had more apparent change with increasing aging time. Nonetheless, α-U 3 O 8 from AUC was found to hydrate more quickly than α-U 3 O 8 from UO 4 , which can likely be attributed to its larger surface area and porous starting material morphology.

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

A Hybrid Catalyst-Bonded Membrane Device for Electrochemical Carbon Monoxide Reduction at Different Relative Humidities

A hybrid catalyst-bonded membrane device using gaseous reactants for a carbon monoxide reduction (COR) reaction in the cathode chamber, an aqueous electrolyte for an oxygen evolution reaction (OER) in the anode chamber, and an anion exchange membrane (AEM) for product separation as modeled, constructed, and tested. The Cu electrocatalyst was electrodeposited onto gas diffusion layers (GDLs) and was directly bonded to AEM by mechanical pressing in the hybrid device. The impacts of relative humidity at the cathode inlet on the selectivity and activity of COR were investigated by computational modeling and experimental methods. At a relative humidity of 30%, the Cu-based catalyst in the hybrid device exhibited a total operating current density of 87 mA cm -2 with a -2.0 V vs Ag/AgCl reference electrode, a Faradaic efficiency (FE) for C 2 H 4 generation of 32.6%, and an FE for a liquid-based carbon product of 42.6%. Significant improvements in the partial current densities for COR were observed in relation to planar electrodes or flooded gas diffusion electrodes (GDEs). Finally in addition, a custom test bed was constructed to characterize the oxidation states of the Cu catalysts in real time along with product analysis though the backside of the GDLs via operando X-ray absorption (XAS) measurements.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Intensified Humid Heat Events Under Global Warming

Based on the CMIP5 multi-model simulations, this paper investigates the future changes in extreme wet-bulb temperatures (TWs) and extreme dry-bulb temperatures (Ts) globally under both low and high emission scenarios (RCP4.5 and RCP8.5). Under a warming climate, T and TW exhibit a higher absolute increase in their mean values over the mid-high latitudes while they show higher relative increases in their mean values and variability over tropics. Here, humid and dry heat events which consist of consecutive extreme TWs and Ts show higher occurrences over tropics, governed by the joint increases in mean values and variability of TW and T therein. Humid heat events show intensifications to dry heat events with higher frequency, duration, and intensity, driven by the lower variability of TW than T. In the mid-high latitudes, heat events will start earlier and last longer in warm season under RCP8.5 than RCP4.5, motivating the need for global warming mitigation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Proton conductivity of perfluorosulfonate ionomers at high temperature and high relative humidity

The proton transport properties of Nafion membranes were studied in a wide range of temperature by using an air-tight sample holder able to maintain the sample hydrated at high relative humidity. The proton conductivity of hydrated Nafion membranes continuously increased in the temperature range of 40–180 °C with relative humidity kept at RH = 100%. In the temperature range of 40–90 °C, the proton conductivity followed the Arrhenius-like thermal dependence. The calculated apparent activation energy E{sub a} values are in good agreement with proton transport via the structural diffusion in absorbed water. However, at higher measuring temperatures an upturn of the electrical conductivity was observed to be dependent on the thermal history of the sample.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Enhancement of humidity sensitivity of graphene through functionalization with polyethylenimine

In this work, we show that the sensing performance of graphene based humidity sensors can be largely improved through polymer functionalization. Chemical vapor deposited graphene is functionalized with amine rich polymer, leading to electron transfer from amine groups in the polymer to graphene. The functionalized graphene humidity sensor has demonstrated good sensitivity, recovery, and repeatability. Charge transfer between the functionalized graphene and water molecules and the sensing mechanism are studied systemically using field effect transistor geometry and scanning Kelvin probe microscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Examination of humidity effects on measured thickness and interfacial phenomena of exfoliated graphene on silicon dioxide via amplitude modulation atomic force microscopy

The properties of Few-Layer Graphene (FLG) change with the number of layers and Amplitude Modulation (AM) Atomic Force Microscopy (AFM) is commonly used to determine the thickness of FLG. However, AFM measurements have been shown to be sensitive to environmental conditions such as relative humidity (RH). In the present study, AM-AFM is used to measure the thickness and loss tangent of exfoliated graphene on silicon dioxide (SiO{sub 2}) as RH is increased from 10% to 80%. We show that the measured thickness of graphene is dependent on RH. The loss tangent values of the graphene and oxide regions are both affected by humidity, with generally higher loss tangent for graphene than SiO{sub 2}. As RH increases, we observe the loss tangent of both materials approaches the same value. We hypothesize that there is a layer of water trapped between the graphene and SiO{sub 2} substrate to explain this observation. Using this interpretation, the loss tangent images also indicate movement and change in this trapped water layer as RH increases, which impacts the measured thickness of graphene using AM-AFM.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Synthesis of large scale graphene oxide using plasma enhanced chemical vapor deposition method and its application in humidity sensing

Large scale graphene oxide (GO) is directly synthesized on copper (Cu) foil by plasma enhanced chemical vapor deposition method under 500 °C and even lower temperature. Compared to the modified Hummer's method, the obtained GO sheet in this article is large, and it is scalable according to the Cu foil size. The oxygen-contained groups in the GO are introduced through the residual gas of methane (99.9% purity). To prevent the Cu surface from the bombardment of the ions in the plasma, we use low intensity discharge. Our experiment reveals that growth temperature has important influence on the carbon to oxygen ratio (C/O ratio) in the GO; and it also affects the amount of π-π* bonds between carbon atoms. Preliminary experiments on a 6 mm × 12 mm GO based humidity sensor prove that the synthesized GO reacts well to the humidity change. Our GO synthesis method may provide another channel for obtaining large scale GO in gas sensing or other applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

A study on different morphological structures of zinc oxide nanostructures for humidity sensing application

Effects of different morphological structures of ZnO to the performance of the device in the humidity sensing have been studied. Two different kinds of nanostructures were obtained which are nanords and nanoflakes. From the surface morphology image, the ZnO nanoflakes has lower diameter size of 100 nm compared to ZnO nanorods of 250 nm. The ZnO nanoflakes are not aligned and has low porous structure compared to ZnO nanorods. The humidity sensor performance of ZnO nanorods has superior performance compared to ZnO nanoflakes. The sensitivity of the ZnO nanorods sensor is 3.20 which are almost two times higher than the ZnO nanoflakes of 1.65. The structural properties of the samples have been characterized using field emission scanning electron microscopy (FESEM) electrical properties has been characterized using current voltage (I-V) measurement.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Machinable, high‐conductivity NaSICON through mitigation of humidity effects during solid‐state synthesis

The Na + super ion conductor (NaSICON, Na 1+x Zr 2 Si x P 3-x O 12 ) is a solid electrolyte well-known for fast, selective Na + transport at low temperatures, uniquely enabling sodium-based batteries. Producing high-quality NaSICON from solid-state methods, especially when cost-effective, potentially hygroscopic precursors are used, is not trivial. To understand and eliminate the influence of humidity during processing, a scheme was developed to reproducibly yield a high Na + conductivity (3.75 mS/cm at 25°C, 81.7 mS/cm at 150°C), high density (97%), and machinable NaSICON without the use of binders, sintering aids, or dopants. Controlled humidity studies over 20%–50% RH coupled with thermal, structural, and electrical analysis reveal that calcination temperatures < 1000°C leave NaSICON processing susceptible to water absorption at > 20% RH due to the presence of hygroscopic Na 3 PO 4 and Na 2 CO 3 during shaping, pressing, and sintering. Water absorption results in NaSICON with lower densities, machinability, and Na+ conductivity, due to impaired intergranular Na+ transport. At the other extreme, fully converting precursor to the NaSICON phase at 1230°C before pressing and sintering leads to poor conductivity and density. By calcining at 1000°C, excellent quality NaSICON may be produced under a range of laboratory environments, enabling low-cost production of high-conductivity, machinable NaSICON necessary the ever-growing energy storage market.

NaSICON↗
DOE OSTI2013

Reducing Thermal Losses and Gains With Buried and Encapsulated Ducts in Hot-Humid Climates

Thermal losses and gains from ductwork installed in unconditioned spaces—such as attics, crawl spaces, and garages—can contribute significantly to the overall heating and cooling loads of single-family residential buildings, with estimated duct losses ranging from 10%–45 %. The impact is particularly severe in hot climates where air conditioning dominates and extensive duct systems are typically located in hot attics. The duct system inefficiencies are greatest at peak demand conditions when the attic is hottest and run times are the highest. The thermal losses and gains at the three single-story houses in Florida monitored in this study accounted for 15%–35% of the annual pre-retrofit heating and cooling energy use and 6%–25% of the total pre-retrofit annual utility bill. Even though a number of existing methods can effectively move ducts into the conditioned space, they are not currently being widely implemented. Physically locating the ducts within the conditioned space is most often applicable only to new construction projects and requires planning during design. Attics can be insulated at the roof deck with closed-cell polyurethane foam (ccSPF) to reduce duct losses and infiltration rates, but this method has high up-front costs and the potential to increase loads on the building enclosure. In hot-dry climates, attic duct systems can be buried under loose-fill insulation at a significantly lower cost to reduce thermal loads. In hot-humid climates, however, condensation on the duct jacket can occur when the humidity in the attic is high.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Approaches to 30% Energy Savings at the Community Scale in the Hot-Humid Climate

BA-PIRC has worked with several community-scale builders within the hot humid climate zone to improve performance of production, or community scale, housing. Tommy Williams Homes (Gainesville, FL), Lifestyle Homes (Melbourne, FL), and Habitat for Humanity (various locations, FL) have all been continuous partners of the BA Program and are the subjects of this report to document achievement of the Building America goal of 30% whole house energy savings packages adopted at the community scale. The scope of this report is to demonstrate achievement of these goals though the documentation of production-scale homes built cost-effectively at the community scale, and modeled to reduce whole-house energy use by 30% in the Hot Humid climate region. Key aspects of this research include determining how to evolve existing energy efficiency packages to produce replicable target savings, identifying what builders' technical assistance needs are for implementation and working with them to create sustainable quality assurance mechanisms, and documenting the commercial viability through neutral cost analysis and market acceptance. This report documents certain barriers builders overcame and the approaches they implemented in order to accomplish Building America (BA) Program goals that have not already been documented in previous reports.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Expert Meeting: Recommended Approaches to Humidity Control in High Performance Homes

The topic of this Building America expert meeting was 'Recommended Approaches to Humidity Control in High Performance Homes,' which was held on October 16, 2012, in Westford, MA, and brought together experts in the field of residential humidity control to address modeling issues for dehumidification. The presentations and discussions centered on computer simulation and field experience with these systems, with the goal of developing foundational information to support the development of a Building America Measure Guideline on this topic.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

Comfort in High-Performance Homes in a Hot-Humid Climate

"9IBACOS monitored 37 homes during the late summer and early fall of 2014 in a hot and humid climate to better understand indoor comfort conditions. These homes were constructed in the last several years by four home builders that offered a comfort and performance guarantee for the homes. The homes were located in one of four cities: Tampa, Florida; Orlando, Florida; Houston, Texas; and San Antonio, Texas. Temperature and humidity data were collected from the thermostat and each room of the house using small, battery-powered data loggers. To understand system runtime and its impact on comfort, supply air temperature also was measured on a 1-minute interval. Overall, the group of homes only exceeded a room-to-room temperature difference of 6 degrees F for 5% of the time. For 80% of the time, the rooms in each house were within 4 degrees F of each other. Additionally, the impact of system runtime on comfort is discussed. Finally, measurements made at the thermostat were used to better understand the occupant operation of each cooling system's thermostat setpoint. Builders were questioned on their perceived impact of offering a comfort and performance guarantee. Their feedback, which generally indicates a positive perception, has been summarized in the report.

"9residential↗
DOE OSTI2016

Comfort in High-Performance Homes in a Hot-Humid Climate

IBACOS monitored 37 homes during the late summer and early fall of 2014 in a hot and humid climate to better understand indoor comfort conditions. These homes were constructed in the last several years by four home builders that offered a comfort and performance guarantee for the homes. The homes were located in one of four cities: Tampa, Florida; Orlando, Florida; Houston, Texas; and San Antonio, Texas. Temperature and humidity data were collected from the thermostat and each room of the house using small, battery-powered data loggers. To understand system runtime and its impact on comfort, supply air temperature also was measured on a 1-minute interval. Overall, the group of homes only exceeded a room-to-room temperature difference of 6 degrees Fahrenheit for 5% of the time.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Phosphoric Acid-Doped Ion-Pair Coordinated PEMs with Broad Relative Humidity Tolerance

Proton exchange membrane (PEM) capable of working over a broad operating condition window is critical for successful adoption of PEM-based electrochemical devices. In this work, phosphoric acid (PA)-doped biphenyl-backbone ion-pair coordinated PEMs were prepared by quaternization of BPBr-100, a precursor polymer, with three different tertiary amines including trimethylamine, 1-methylpiperidine, and 1,2-dimethylimidazole followed by membrane casting, ion exchange reaction to hydroxide ion, and doping with PA. The resulting PA-doped ion-pair PEMs were characterized in terms of PA doping level, proton conductivity, relative humidity (RH) tolerance, thermal stability, and mechanical properties. PA doping levels were between six and eight according to acid-base titration. The size and structure of the cation group of ion-pair polymers were found to affect the PA doping level and water uptake. Proton conductivity was studied as a function of RH over a wide range of 5% to 95% RH. Stable conductivity at 80 °C was observed up to 70% RH for 10 h. Mechanical property characterization indicates that the PA doping process resulted in more ductile membranes with significantly increased elongation at break due to the plasticization effect of PA. A combination of high proton conductivity at low RH conditions, and good humidity tolerance makes this new class of PEMs great potential candidates for use in electrochemical devices such as proton exchange membrane fuel cells and electrochemical hydrogen compressors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2000

Remote query measurement of pressure, fluid-flow velocity, and humidity using magnetoelastic thick-film sensors

Free-standing magnetoelastic thick-film sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted from the sensor in response to a time varying magnetic field. This property allows the sensors to be monitored remotely without the use of direct physical connections, such as wires, enabling measurement of environmental parameters from within sealed, opaque containers. In this work, we report on application of magnetoelastic sensors to measurement of atmospheric pressure, fluid-flow velocity, temperature, and mass load. Mass loading effects are demonstrated by fabrication of a remote query humidity sensor, made by coating the magnetoelastic thick film with a thin layer of solgel deposited Al2O3 that reversibly changes mass in response to humidity. c2000 Elsevier Science S.A. All rights reserved.

NASA Discipline Life Sciences Technologies↗
NASA NTRS2000

Magnetoelastic sensors in combination with nanometer-scale honeycombed thin film ceramic TiO2 for remote query measurement of humidity

Ribbonlike magnetoelastic sensors can be considered the magnetic analog of an acoustic bell; in response to an externally applied magnetic field impulse the sensors emit magnetic flux with a characteristic resonant frequency. The magnetic flux can be detected external to the test area using a pick-up coil, enabling query remote monitoring of the sensor. The characteristic resonant frequency of a magnetoelastic sensor changes in response to mass loads. [L.D. Landau and E. M. Lifshitz, Theory of Elasticity, 3rd ed. (Pergamon, New York, 1986). p. 100].Therefore, remote query chemical sensors can be fabricated by combining the magnetoelastic sensors with a mass changing, chemically responsive layer. In this work magnetoelastic sensors are coated with humidity-sensitive thin films of ceramic, nanodimensionally porous TiO2 to make remote query humidity sensors. c2000 American Institute of Physics.

NASA Discipline Life Sciences Technologies↗
NASA NTRS1997

Temperature and Humidity Dependence of a Polymer-Based Gas Sensor

This paper quantifies the temperature and humidity dependence of a polymer-based gas sensor. The measurement and analysis of three polymers indicates that resistance changes in the polymer films, due to temperature and humidity, can be positive or negative. The temperature sensitivity ranged from +1600 to -320 ppm/nd the relative sensitivity ranged from +1100 to -260 ppm/%.

temperature humidity gas sensor polymers↗