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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Optical sensor employing a refractive index engineered metal oxide material

An optical sensor device includes an optical waveguide portion having a core, the core having a first refractive index, and a functional material layer coupled to the optical fiber portion, the functional material layer being made of a metal oxide material, the functional material layer being structured to have a second refractive index, the second refractive index being less than the first refractive index. The functional material layer may be a nanostructure material comprising the metal oxide material with a plurality of holes or voids formed therein such that the functional material layer is caused to have the second refractive index.

Chen, Peng↗
DOE OSTI2019

Quantum material topology via defect engineering

Current approaches of discovering new topological quantum materials, such as (magnetic) Weyl materials, by screening material databases or by rational design suffer from experimental challenges in growing the material in the desired geometry, hampering their potential applications. We take an approach of defect-engineering a topology starting from systems with experimentally well-controlled growth . Using SnTe, an experimentally viable topological crystalline insulator, as our model system, we elucidate the different effects of breaking time-reversal, inversion, and mirror symmetries using magnetic dopant defects, to controllably induce a topological phase transition. To this effect, we compute the thermodynamics, magnetism, and band-structure topology of magnetically doped SnTe using a full ab initio approach. In this process, we have discovered that Cr-doped SnTe is a Weyl semimetal. We have computed its classic Fermi-arc experimental signature on the (001) surface and also showed that it has a large anamolous Hall conductivity (AHC) of ~ 250 Ω - 1 cm - 1 . We predict a large Curie temperature ( T c ) of 62 K even at 3.3 % doping, with both T c and AHC being tunable with Cr concentration, suggesting potential for room-temperature applications. Our study in general paves the way for defect-designing room-temperature topological quantum phases.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Rheinheimera sp . T2C2 Bacterial Biofilm for Bioremediation of Cobalt(II)

Toxic metals, including cobalt, are often the cause of the contamination of rivers and lakes in mining regions. Heavy metal water pollution has been linked to numerous human health problems, prompting the need for environmental remediation. Existing techniques for removing heavy metals from water, such as chemical precipitation and filtration, produce toxic waste, are costly, or require high power consumption for pumping. Biosorption is a potential alternative strategy that is cost-effective and uses readily available and naturally produced biomass and living material to absorb pollutants. Engineering living materials, such as biofilms, which consist of living cells and a secreted polymer matrix, offer the potential to integrate toxin sensing, sequestration, and metabolism capabilities of cells to improve pollution remediation strategies. Alternative biofilm producing candidates need to be explored to implement these material capabilities. Previous biosorption studies have primarily used bacterial biofilms from known pathogens and/or generated toxic waste in the form of the absorbent material combined with the heavy metal. Here, we describe a recently isolated bacterium called Rheinheimera sp. T2C2 that forms biofilms with promising biosorption characteristics. T2C2 is an aquatic bacterium with low nutrient requirements and high biofilm production that is not known to be pathogenic. We demonstrate (1) the efficacy of Rheinheimera sp. T2C2 as a biosorbent for cobalt bioremediation; (2) how biosorption is altered by water conditions to establish the efficacy of this strategy in different environments; and (3) how the metal can be released from the biofilm for metal recycling. Our findings will provide a living materials strategy that overcomes the existing barriers for bioremediation and improves the health of ecosystems and humans through heavy metal removal and recycling.

Rheinheimera↗
NASA NTRS1991

Alkali metal compatibility testing of candidate heater head materials for a Stirling engine heat transport system

The authors describe work performed as part of the 25-kWe advanced Stirling conversion system project. Liquid alkali metal compatibility is being assessed in an ongoing test program to evaluate candidate heater head materials and fabrication processes at the temperatures and operating conditions required for Stirling engines. Specific materials under evaluation are alloy 713LC, alloy 713LC coated with nickel aluminide, and Udimet 720, each in combination with Waspaloy. The tests were run at a constant 700 C. A eutectic alloy of sodium and potassium (NaK) was the working fluid. Titanium sheet in the system was shown to be an effective oxygen getter. Metallographic and microchemical examination of material surfaces, joints, and their interfaces revealed little or no corrosion after 1000 h. Tests are in progress, with up to 10,000 h exposure.

Noble, Jack E.↗
NASA NTRS1977

Cost benefit study of advanced materials technology for aircraft turbine engines

The cost/benefits of eight advanced materials technologies were evaluated for two aircraft missions. The overall study was based on a time frame of commercial engine use of the advanced material technologies by 1985. The material technologies evaluated were eutectic turbine blades, titanium aluminide components, ceramic vanes, shrouds and combustor liners, tungsten composite FeCrAly blades, gamma prime oxide dispersion strengthened (ODS) alloy blades, and no coat ODS alloy combustor liners. They were evaluated in two conventional takeoff and landing missions, one transcontinental and one intercontinental.

Hillery, R. V.↗
NASA NTRS1990

Materials for a Stirling engine heater head

Work done on the 25-kW advanced Stirling conversion system (ASCS) terrestrial solar program in establishing criteria and selecting materials for the engine heater head and heater tubes is described. Various mechanisms contributing to incompatibility between materials are identified and discussed. Large thermal gradients, coupled with requirements for long life (60,000 h at temperature) and a large number of heatup and cooldown cycles (20,000) drive the design from a structural standpoint. The pressurized cylinder is checked for creep rupture, localized yielding, reverse plasticity, creep and fatigue damage, and creep ratcheting, in addition to the basic requirements for bust and proof pressure. In general, creep rupture and creep and fatigue interaction are the dominant factors in the design. A wide range of materials for the heater head and tubes was evaluated. Factors involved in the assessment were strength and effect on engine efficiency, reliability, and cost. A preliminary selection of Inconel 713LC for the heater head is based on acceptable structural properties but driven mainly by low cost. The criteria for failure, the structural analysis, and the material characteristics with basis for selection are discussed.

Noble, J. E.↗
DOE OSTI2023

Enhanced Switching Reliability of Hf 0.5 Zr 0.5 O 2 Ferroelectric Films Induced by Interface Engineering

Ferroelectric materials have been widely researched for applications in memory and energy storage. Among these materials and benefiting from their excellent chemical compatibility with complementary metal–oxide–semiconductor (CMOS) devices, hafnia-based ferroelectric thin films hold great promise for highly scaled semiconductor memories, including nonvolatile ferroelectric capacitors and transistors. However, variation in the switched polarization of this material during field cycling and a limited understanding of the responsible mechanisms have impeded their implementation in technology. Here, we show that ferroelectric Hf 0.5 Zr 0.5 O 2 (HZO) capacitors that are nearly free of polarization “wake-up”─a gradual increase in switched polarization as a function of the number of switching cycles─can be achieved by introducing ultrathin HfO 2 buffer layers at the HZO/electrodes interface. High-resolution transmission electron microscopy (HRTEM) reveals crystallite sizes substantially greater than the film thickness for the buffer layer capacitors, indicating that the presence of the buffer layers influences the crystallization of the film (e.g., a lower ratio of nucleation rate to growth rate) during postdeposition annealing. This evidently promotes the formation of a polar orthorhombic (O) phase in the as-fabricated buffer layer samples. Synchrotron X-ray diffraction (XRD) reveals the conversion of the nonpolar tetragonal (T) phase to the polar orthorhombic (O) phase during electric field cycling in the control (no buffer) devices, consistent with the polarization wake-up observed for these capacitors. The extent of T–O transformation in the nonbuffer samples is directly dependent on the duration over which the field is applied. Here these results provide insight into the role of the HZO/electrodes interface in the performance of hafnia-based ferroelectrics and the mechanisms driving the polarization wake-up effect.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Materials and Fuels Complex West Campus Utility Corridor Preliminary Engineering Report

The current MFC wastewater system provides reliable and adequate disposal to the facilities within MFC; however, in anticipation of immediate and future growth, MFC desires to make upgrades to accommodate increased staffing levels and additional facilities at the complex. BEA has worked with J-U-B to evaluate the current wastewater system and to identify future improvements to the facility to provide wastewater service for future growth. This PER summarizes the improvements in accordance with Idaho Administrative Code IDAPA 58.01.16.411. These improvements are part of the MFC West Campus Utility Corridor project and consist of a new gravity collection system, pressurized forcemains, and a lift station.

42 ENGINEERING↗
DOE OSTI2019

Dissolved organic matter reduces the effectiveness of sorbents for mercury removal

Mercury (Hg) contamination of soils and sediments impacts numerous environments worldwide and constitutes a challenging remediation problem. In this study, we evaluate the impact of dissolved organic matter (DOM) on the effectiveness of eight sorbent materials considered for Hg remediation in soils and sediments. The materials include both engineered and unmodified materials based on carbon, clays, mesoporous silica and a copper alloy. Initially, we investigated the kinetics of Hg(II) complexation with DOM for a series of Hg:DOM ratios. Steady-state Hg-DOM complexation occurred within 48 to 120 h, taking longer time at higher Hg:DOC (dissolved organic carbon) molar ratios. In subsequent equilibrium experiments, Hg(II) was equilibrated with DOM at a defined Hg:DOC molar ratio (2.4 · 10 –6 ) for 170 h and used in batch experiments to determine the effect of DOM on Hg partition coefficients and sorption isotherms by comparing Hg(II) and Hg-DOM. Hg sorption capacities of all sorbents were severely limited in the presence of DOM as a competing ligand. Thiol-SAMMS®, SediMite™ and pine biochar were most effective in reducing Hg concentrations. While pine biochar and lignin-derived carbon processed at high temperatures released negligible amounts of anions into solution, leaching of sulfate and chloride was observed for most engineered sorbent materials. Sulfate may stimulate microbial communities harboring sulfate reducing bacteria, which are considered one of the primary drivers of microbial mercury methylation in the environment. Here, the results highlight potential challenges arising from the application of sorbents for Hg remediation in the field.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Enhancing ferroelectric photovoltaic effect by polar order engineering

Ferroelectric materials for photovoltaics have sparked great interest because of their switchable photoelectric responses and above-bandgap photovoltages that violate conventional photovoltaic theory. However, their relatively low photocurrent and power conversion efficiency limit their potential application in solar cells. To improve performance, conventional strategies focus mainly on narrowing the bandgap to better match the solar spectrum, leaving the fundamental connection between polar order and photovoltaic effect largely overlooked. We report large photovoltaic enhancement by A-site substitutions in a model ferroelectric photovoltaic material, BiFeO 3 . As revealed by optical measurements and supported by theoretical calculations, the enhancement is accompanied by the chemically driven rotational instability of the polarization, which, in turn, affects the charge transfer at the band edges and drives a direct-to-indirect bandgap transition, highlighting the strong coupling between polarization, lattice, and orbital order parameters in ferroelectrics. In conclusion, polar order engineering thus provides an additional degree of freedom to further boost photovoltaic efficiency in ferroelectrics and related materials.

36 MATERIALS SCIENCE↗