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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

A high-performance photovoltaic concentrator array - The mini-dome Fresnel lens concentrator with 30 percent efficient GaAs/GaSb tandem cells

A high-efficiency, lightweight space photovoltaic concentrator array is described. Previous work on the minidome Fresnel lens concentrator concept is being integrated with Boeing's 30 percent efficient tandem GaAs/GaSb concentrator cells into a high-performance photovoltaic array. Calculations indicate that, in the near term, such an array can achieve 300 W/sq m at a specific power of 100 W/kg. Emphasis of the program has now shifted to integrating the concentrator lens, tandem cell, and supporting panel structure into a space-qualifiable array. A description is presented of the current status of component and prototype panel testing and the development of a flight panel for the Photovoltaic Array Space Power Plus Diagnostics (PASP PLUS) flight experiment.

Piszczor, M. F.↗
DOE OSTI2015

Novel DDR Processing of Corn Stover Achieves High Monomeric Sugar Concentrations from Enzymatic Hydrolysis (230 g/L) and High Ethanol Concentration (10% v/v) During Fermentation

Distilling and purifying ethanol, butanol, and other products from second and later generation lignocellulosic biorefineries adds significant capital and operating cost for biofuels production. The energy costs associated with distillation affects plant gate and life cycle analysis costs. Lower titers in fermentation due to lower sugar concentrations from pretreatment increase both energy and production costs. In addition, higher titers decrease the volumes required for enzymatic hydrolysis and fermentation vessels. Therefore, increasing biofuels titers has been a research focus in renewable biofuels production for several decades. In this work, we achieved over 200 g/L of monomeric sugars after high solids enzymatic hydrolysis using the novel deacetylation and disc refining (DDR) process on corn stover. The high sugar concentrations and low chemical inhibitor concentrations from the DDR process allowed ethanol titers as high as 82 g/L in 22 hours, which translates into approximately 10 vol% ethanol. To our knowledge, this is the first time that 10 vol% ethanol in fermentation derived from corn stover without any sugar concentration or purification steps has been reported. Techno-economic analysis shows the higher titer ethanol achieved from the DDR process could significantly reduce the minimum ethanol selling price from cellulosic biomass.

09 BIOMASS FUELS↗
DOE OSTI2016

Measurements of structures and concentrations of carbon particle species in premixed flames by the use of in-situ wide angle X-ray scattering

In-situ wide-angle X-ray scattering (WAXS) measurements have been conducted on atmospheric-pressure fuel-rich premixed freely propagating ethylene/oxygen flames with argon and nitrogen dilution. In this work, a novel analysis methodology able to provide quantitative information on soot/carbon particle species and concentrations was tested under heavy sooting conditions. The particle composition and concentrations were retrieved by fitting theoretical calculations of structural components from major molecular and nanometric species to the experimental WAXS data. The results show that argon dilution yields predominantly graphenelike components that are less stacked and amorphous carbon that is less structured than under nitrogen dilution. This finding was later confirmed by electron microscopy analysis on samples extracted from similar flames. In addition, the WAXS showed that most of the carbon present in the flames was bound as particles. These results constitute some of the first in-situ observations on structures and concentrations of carbon species in laboratory burner flames operating without stabilization plates.

Concentrations↗
DOE OSTI2018

Effects of Fe concentration on helium bubble formation in NiFe x single-phase concentrated solid solution alloys

The formation of helium bubbles and the consequential property degradation are critical challenges for materials used in advanced nuclear energy systems. The mechanism of helium bubble formation in a series of NiFe x (x = 0, 20, 35, or 50 at.%) single-phase concentrated solid solution alloys (SP-CSAs) are studied in this work. Transmission electron microscopy analysis shows that with increasing Fe concentration, the average bubble size decreases while the bubble number density increases, indicating the growth of large helium bubbles in NiFe x SP-CSAs is suppressed by increasing the alloy chemical complexity through increased Fe concentration. Mechanisms for the slower bubble growth rate in NiFe x binary SP-CSAs compared Ni are identified. These mechanisms include promotion of Frenkel pair recombination, denser and more homogeneously distributed nucleation sites, and increased helium atom densities inside the bubbles. Here, the results demonstrate that optimizing the chemical complexity in SP-CSAs can be an effective approach to design materials with superior resistance to helium bubble nucleation and growth.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of Particle Size and Concentration of Magnesium Oxide on the Lubricating Performance of a Chloride Molten Salt for Concentrating Solar Power

One engineering challenge for the next-generation concentrating solar power (CSP) is to identify appropriate heat transfer and thermal energy storage media. A chloride salt mixture (20 wt % NaCl + 40 wt % MgCl 2 + 40 wt % KCl) in a molten phase is proposed as a potential fluid for carrying the heat as well as lubricating the CSP pump bearings. Due to the hygroscopic nature of MgCl 2 , the presence of magnesium oxide (MgO) particles is inevitable. In order to understand the impact of MgO particles, this study investigated the tribological behavior of the molten chloride salt mixture containing MgO of various particle sizes and concentrations. Tests were conducted at 750 °C in a dry Ar environment using a zirconia ball sliding against a Haynes 244 alloy disc lubricated by the molten salt. There was a clear trend of the increased friction coefficient and wear loss for a larger particle size and/or a higher concentration of MgO. Distinct wear mechanisms were identified for the ceramic ball and alloy disc. Results provide fundamental insights for this new research avenue of molten salt lubrication for CSP.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Temperature and concentration dependent magnetic properties of epitaxial Fe{sub 1−x}Cr{sub x}-alloy films in the high Cr-concentration regime

Soft magnetic materials with a Curie temperature (T{sub c}) close to room temperature are suitable candidates for device applications and for more fundamental aspects of magnetism. Promising candidates are Fe{sub 1−x}Cr{sub x}-alloys with a Fe concentration of about 25%–35%. We have grown by molecular beam epitaxy methods a number of epitaxial Fe{sub 1−x}Cr{sub x} alloys on MgO[100] and MgO[110] substrates, and we report on their structural and magnetic properties in this concentration range, including the dependence of the Curie temperature (T{sub c}) on the concentration, the magnetocrystalline anisotropy, and the development of the magnetic moment.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Oxidation Behavior of Copper Concentrate, Gold Concentrate, and Their Mixtures Between 1173 K (900 °C) and 1373 K (1100 °C)

Gold is typically extracted from ores using a cyanidation process. However, environmental regulations and low productivity are the main drawbacks of cyanide usage. Alternative technologies for gold extraction are being studied although development of any new technology necessitates additional investments. In South Korea, recovery of gold and silver is performed by the local copper producer by feeding gold concentrate into a smelter. An integrated copper-making process might be an efficient and feasible alternative for the extraction of precious metals without the use of toxic cyanide. Installed exhaust gas cleaning system of copper smelter would minimize the toxic effects of hazardous elements (arsenic, bismuth, antimony, etc.) contained in gold concentrates. A kinetic and thermodynamic understanding of the effects of gold concentrates on copper metallurgy is necessary for the operation. The effects of various parameters on the oxidation kinetics of sulfides were investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. Lastly, this rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Effect of plasma on gas flow and air concentration in the effluent of a pulsed cold atmospheric pressure helium plasma jet

In this work, we report on the flow effects induced by a nanosecond pulsed helium cold atmospheric pressure plasma jet impinging on a glass substrate. Herein, gas temperature measurements have been performed using optical emission spectroscopy including rotational spectra of OH(A-X) (0,0) and N 2 (C-B) (0,0) and resonance broadening of a helium emission line at 667.8 nm. The measured increase in gas temperature was less than 15 K. We have measured the air concentration distribution in the jet effluent by means of Rayleigh scattering exploiting the large difference in Rayleigh cross-section of air and helium. The obtained results show that the plasma causes a broadening of the helium channel suggesting an enhanced gas velocity and mixing with the ambient air. The impact of the plasma on the jet effluent is polarity dependent and is larger in the case of positive applied voltage pulses. Using an estimation of the increased gas velocity required to obtain the observed air concentrations, we have shown that both gas heating and electrohydrodynamic (EHD) forces related to the propagation of an ionization front are not causing the observed phenomena. The surface charge which can exist for a much longer time than the duration of the applied voltage pulse is the primary cause of the EHD forces on the bulk charges which lead to significant different air concentration profiles in the jet effluent for plasma on and off.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Recovery of Rare Earth Oxides from Flotation Concentrates of Bastnaesite Ore by Ultra-Fine Centrifugal Concentration

Historically, the ability to effectively separate carbonate gangue from bastnaesite via flotation has frequently proven to be challenging without sacrificing significant rare earth oxide (REO) grade or recovery. However, in light of the fact that the rare earth bearing minerals often exhibit higher specific gravities than the carbonate gangue, the possibility exists that the use of gravity separation could be used to achieve such a selective separation. This however is complicated by the fact that, in cases such as this study when the liberation size is finer than 50 microns, most traditional gravity separation methods become increasingly challenging. The aim of this study is to determine the applicability of centrifugal concentrators to beneficiate ultra-fine (UF) bastnaesite and calcite bearing flotation concentrates. By using a UF Falcon, it was possible to achieve initial gravity REO recoveries exceeding 90% while rejecting on the order of 25% to 35% of the total calcium from an assortment of rougher and cleaner flotation concentrates. Additionally, when additional stages of cleaner UF Falcon gravity separation were operated in an open circuit configuration, it was possible, from an original fine feed of 35 microns containing 50.5% REO and 5.5% Ca, to upgrade up to approximately 59% REO and 2.0% calcium. While not the goal of this study, these results also support previous limited data to suggest that UF Falcons are potentially capable of treating a wider range of materials than they were originally designed for, including feeds rich in heavy mineral content.

Norgren, Alex↗
NASA NTRS1976

Concentrations of trace elements and compounds in the airborne suspended particulate matter in Cleveland, Ohio, from August 1971 to August 1972 and their dependence on wind direction: Complete data listing and concentration roses

Concentrations of 75 chemical constituents in the airborne particulate matter were measured in Cleveland, Ohio during 1971 and 1972. Daily values, maxima, geometric means and their standard deviations covering a 1-year period (45 to 50 sampling days) at each of 16 sites are presented on microfiche for 60 elements, and for a lesser number of days for 10 polycyclic aromatic hydrocarbon compounds (PAH), the aliphatic hydrocarbon compounds (AH) as a group and carbon. In addition, concentration roses showing directional properties are presented for 39 elements, 10 PAH and the AH as a group. The elements (except carbon) are shown both in terms of concentration and percentage of the suspended particulate matter.

King, R. B.↗