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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Trace metal contents of autotrophic flagellates from contrasting open‐ocean ecosystems

Abstract Nano‐ and picophytoplankton are a major component of open‐ocean ecosystems and one of the main plankton functional types in biogeochemical models, yet little is known about their trace metal contents. In cultures of the picoeukaryote Ostreococcus lucimarinus , iron limitation reduced iron quotas by 68%, a fraction of the plasticity known in diatoms. In contrast, a commonly co‐occurring cyanobacterium, Prochlorococcus , showed variable iron contents with iron availability in culture. Synchrotron X‐ray fluorescence was used to measure single‐cell metal (Mn, Fe, Co, Ni, Zn) quotas of autotrophic flagellates (1.4–16.8‐ μ m diameter) collected from four ocean regions. Iron quotas were tightly constrained and showed little response to iron availability, similar to cultured Ostreococcus . Zinc quotas also did not vary with zinc availability but appeared to vary with phosphorus availability. These results suggest that macronutrient and metal availability may be equally important for controlling metal contents of small eukaryotic open‐ocean phytoplankton.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Effect of Oregano Essential Oil Content on Properties of Green Biocomposites Based on Cassava Starch and Sugarcane Bagasse for Bioactive Packaging

In this study, 10 wt% sugarcane bagasse fiber-reinforced starch foam composites were prepared with different oregano essential oil (OEO) contents in the range of 2–8 wt% to improve the antimicrobial effectiveness of bioactive packaging. FT-IR analysis confirms that OEO penetrates into starch foam composite. From the result of antimicrobial activity, the incorporation of 8 wt% OEO in starch foam composite achieves the minimum inhibitory concentration against Escherichia-coli (E. coli) and Staphylococcus-aureus (S. aureus). OEO is more effective against S. aureus (Gram-positive bacteria) than E. coli (Gram-negative bacteria). The water absorption capacity and hygroscopicity of foam composite decrease with increasing OEO content. The lowest monolayer value is observed in starch foam composite containing 8 wt% OEO. The soil biodegradation rate and flexural strength of samples slightly decrease with increasing OEO content. As a result, starch foam composite containing OEO can be applied as bioactive packaging to preserve foods.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Effect of the Boron Content on the Amorphization Process and Magnetic Properties of the Mechanically Alloyed Fe{sub 92−x}Nb{sub 8}B{sub x} Powders

The effect of the B content on the microstructural, structural, and magnetic properties of partially amorphous Fe{sub 92−x}Nb{sub 8}B{sub x} (x = 5, 10, 15, and 20) alloys has been investigated by means of scanning electron microscopy, X-ray diffraction, high and low-temperature extraction-type magnetometers. The XRD results reveal the formation of a nanocomposite structure where nanocrystalline bcc α-Fe and Fe{sub 2}B phases are embedded into an amorphous matrix. The FeB boride is observed for higher boron contents (x = 15 and 20), and the crystallite sizes are in the range of 7–24 nm. As the B content increases, the amorphous phase-relative proportion and coercivity increase, whereas the saturation magnetization decreases. An important magnetic hardening occurs by lowering the temperature from 400 to 5 K for x = 20% B. The variation of the Curie temperature can be attributed to the heterogeneity of the amorphous matrix.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Effect of MoSi{sub 2} Content on Dry Sliding Tribological Properties of Zr-Based Bulk Metallic Glass Composites

Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} bulk metallic glass and its composites were prepared by suction casting into a copper mold. The effect of MoSi{sub 2} content on the tribological behavior of Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} BMG was studied by using a high-speed reciprocating friction and wear tester. The results indicate that the friction coefficient and wear resistance of the BMGs can be improved by a certain amount of crystalline phase induced by MoSi{sub 2} content from 1 to 3% and deteriorated with MoSi{sub 2} content of 4%. The wear mechanism of both the metallic glass and its composite is abrasive wear. The mechanism of crystalline phase-dependent tribological properties of the composite was discussed based on the wear track and mechanical properties in the present work. The wear behavior of Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} BMG and its composite indicates that a good combination of the toughness and the hardness can make the composite be well wear resistant.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Control of Carbon Content in Ultrafine Cemented Carbide by Heat Treatment in Reducing Atmospheres Containing Carbon Oxides

In this work, the method of control of carbon content in the ultrafine-grained cemented carbide alloy was proposed. The treating of the WC-8Co-0.4VC-0.4Cr{sub 3}C{sub 2} compacts was made in a CO + CO{sub 2} gas mixture at CO concentrations from 0 to 80 vol.% during 50 min at the initial stage of the conventional sintering at a temperature of 700 °C. Conditions for increasing and decreasing the carbon content are CO concentrations of CO in gas mix more than 65 vol.% and less than 35 vol.%, respectively. It is shown that even a small deviation from the stoichiometric carbon content (0.3 wt.%) leads to an increase in porosity and a multiple decrease in the strength of the ultrafine-grained cemented carbide. A comparative analysis with literature data showed that the obtained ultrafine-grained solid alloy WC-8Co-0.4VC-0.4Cr{sub 3}C{sub 2} with stoichiometric composition is not inferior in hardness and toughness to the analogs obtained by hot pressing and electrospark sintering.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Mg Content on the Fatigue Strength and Fracture Behavior of Al-Si-Mg Casting Alloys

In order to investigate the influence of Mg content on the fatigue properties in Al-Si-Mg alloy, uniaxial tensile tests and rotating bending fatigue tests were conducted on two Al-7Si-Mg casting alloys, with different Mg contents of 0.3 and 0.6 wt.%. The fracture surfaces of the specimens were observed by scanning electron microscopy, and the fatigue crack growth process was obtained by the replica method. The results indicate that the increase in Mg content enhances the yield strength and tensile strength of the alloy, whereas it reduces its elongation. There is an obvious knee point in the S–N curves of Al-7Si-0.6Mg alloy while that of Al-7Si-0.3Mg alloy shows continuous decrease. The fatigue strength at 5 × 10{sup 5} cycles is 60 MPa for Al-7Si-0.3Mg alloy and 80 MPa for Al-7Si-0.6Mg alloy. For the two types of specimens, the fatigue failure can initiate from crystal slip and casting defects. The replica results suggest that cracks in Al-7Si-0.6Mg alloy grow more slowly than that in Al-7Si-0.3Mg alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structure and Tribological Properties of CrTiAlCN Coatings with Various Carbon Contents

Multi-component CrTiAlCN coatings with different carbon contents were deposited on AISI M2 high-speed steels using unbalanced magnetron sputtering via adjusting the C{sub 2}H{sub 2} flow rates, and their microstructures and mechanical properties were characterized by using SEM, EDS, XRD, Vickers hardness tester and scratch tester, respectively. The tribological properties of CrTiAlCN coatings sliding against SUS440C high carbon martensitic balls were performed using ball-on-disk tribo-tester. The results showed that CrTiAlCN coatings were mainly comprised of (111) and (200) crystal orientation. The maximum hardness of coatings was 29.4 ± 1.5 GPa as the carbon content was 22.5 at.%. With an increase in the carbon content of coatings, the friction coefficients and wear rates of CrTiAlCN/SUS440C tribo-pairs were significantly reduced, and the wear mechanism of coatings changed from adhesive wear to abrasive wear.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Behavior of Annealed Steels with Different Carbon Contents (0.002, 0.17, 0.43 and 0.7% C) in Freely Aerated 3.5% NaCl Solution

Four annealed carbon steels with different carbon contents (0.002, 0.17, 0.43, and 0.7% C), consisting of ferrite, ferrite-pearlite and fully pearlite microstructures, were selected to understand the corrosion behavior of carbon steel as a function of carbon content in freely aerated 3.5% NaCl solution. Dynamic polarization, electrochemical impedance and linear polarization methods were used. The corrosion rate obtained from the different carbon steels was found to increase greatly from ultra-low carbon steel (0.002%) to low carbon steel (0.17%) due to the presence of pearlite in the low carbon steel. However, the increase in corrosion rate was marginal with the increase in carbon content from low carbon (0.17%) to medium (0.43% C) and high carbon steels (0.7% C). The mirostrucural evolution of the steels before and after polarization test without etching as observed by scanning electron microscopy could show that the corrosion behavior of the steels with the presence of pearlite was due to the combined effect from % pearlite, interlamellar spacing and cementite/ferrite area ratio in pearlite. Pearlite morphology also led to the differential corrosion within the pearlite colony in all the steels except the steel with 0.002% C. Catalytic activity of cementite on enhancing oxygen reduction reaction attributes to the higher corrosion rates in case of the steels with the presence of pearlite.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Chromium Content on Microstructure, Hardness, and Wear Resistance of As-Cast Fe-Cr-B Alloy

The effects of chromium content on microstructure, hardness and wear resistance of as-cast Fe-xCr-1.0B (x = 0, 4, 8, 12, 16, 20) alloys were investigated by means of optical microscope (OM), scanning electron microscope (SEM), x-ray diffractometer (XRD), hardness tester and ring block wear tester. The results showed that the microstructures of chromium-free alloy were mainly composed of pearlite, ferrite, and eutectic borocarbides, and the hardness was very low, only 18.8 HRC. With the increase in chromium content, the matrix of as-cast Fe-Cr-B alloy gradually began to transform from pearlite and ferrite to lath martensite, and the type of borocarbides changed from Fe{sub 2}(B, C) to M{sub 2}(B, C), M{sub 7}(C, B){sub 3} and M{sub 23}(C, B){sub 6} (M = Fe, Cr). When the chromium content was 12 wt.%, the hardness of alloy reached the highest value of 61.1 HRC, and the wear resistance of alloy was the best. The results of worn surface analysis showed that the wear failure of as-cast Fe-Cr-B alloy was mainly caused by multiple plastic deformation and micro-cutting.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effect of High Si Content on U 3 Si 2 Fuel Microstructure

The development of U 3 Si 2 as an accident tolerant nuclear fuel has gained research interest due to its promising high uranium density and improved thermal properties. In the present study, three samples of U 3 Si 2 fuel with varying silicon content have been fabricated by a conventional powder metallurgical route. Microstructural characterization via scanning and transmission electron microscopy reveals the presence of other stoichiometry of uranium silicide such as USi and UO 2 in both samples. The detailed phase analysis by x-ray diffraction shows the presence of secondary phases, such as USi, U 3 Si, and UO 2 . The samples with higher concentrations of silicon content of 7.5 wt.% displays additional elemental Si. Furthermore, these samples also possess an increased amount of the USi phase as compared to that in the conventional sample with 7.3 wt.% silicon. The optimization of U 3 Si 2 fuel performance through the understanding of the role of Si content on its microstructure has been discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Seed-specific overexpression of AtFAX1 increases seed oil content in Arabidopsis

Highlights: • Seed-specific overexpression of AtFAX1 increased seed oil and protein content in Arabidopsis. • Fatty acid and triacylglycerol biosynthesis activity were enhanced in AtFAX1 transgenic plants. • Genes involved in seed sugar importation were induced in AtFAX1 transgenic plants. • Seed-specific overexpression of AtFAX1 increased seed mass and seed size. Biosynthesis of plant seed oil is accomplished through the coordinate action of multiple enzymes in multiple subcellular compartments. Fatty acid (FA) has to be transported from plastid to endoplasmic reticulum (ER) for TAG synthesis. However, the role of plastid FA transportation during seed oil accumulation has not been evaluated. AtFAX1 (Arabidopsis fatty acid export1) mediated the FA export from plastid. In this study, we overexpressed AtFAX1 under the control of a seed specific promoter in Arabidopsis. The resultant overexpression lines (OEs) produced seeds which contained 21–33% more oil and 24–30% more protein per seed than those of the wild type (WT). The increased oil content was probably because of the enhanced FA and TAG synthetic activity. The seed size and weight were both increased accordingly. In addition, the seed number per silique and silique number per plant had no changes in transgenic plants. Taken together, our results demonstrated that seed specific overexpression of AtFAX1 could promote oil accumulation in Arabidopsis seeds and manipulating FA transportation is a feasible strategy for increasing the seed oil content.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Portlandite content and ionic transport properties of hydrated C{sub 3}S pastes

This paper presents the results of a C{sub 3}S paste characterization study. The objective was to determine the parameters needed to model the process of degradation. The experimental study focused on determining the portlandite content and the ionic diffusion coefficients of C{sub 3}S paste. The molar C/S ratio of C-S-H in hydrated C{sub 3}S pastes was also investigated. The portlandite content was determined with an experimental method based on an electron microprobe analysis. This method leads to a portlandite mass content of 24.4 {+-} 2.3%. The diffusion coefficient of each ionic species was determined by inverse analysis of diffusion test data performed on hydrated C{sub 3}S samples using a multiionic transport model.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Quantitative assessment of alkali-reactive aggregate mineral content through XRD using polished sections as a supplementary tool to RILEM AAR-1 (petrographic method)

The mineral content of 5 aggregate samples from 4 different countries, including reactive and non-reactive aggregate types, was assessed quantitatively by X-ray diffraction (XRD) using polished sections. Additionally, electron probe microanalyzer (EPMA) mapping and cathodoluminescence (CL) were used to characterize the opal-CT identified in one of the aggregate samples. Critical review of results from polished sections against traditionally powdered specimen has demonstrated that for fine-grained rocks without preferred orientation the assessment of mineral content by XRD using polished sections may represent an advantage over traditional powder specimens. Comparison of data on mineral content and silica speciation with expansion data from PARTNER project confirmed that the presence of opal-CT plays an important role in the reactivity of one of the studied aggregates. Used as a complementary tool to RILEM AAR-1, the methodology suggested in this paper has the potential to improve the strength of the petrographic method.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Elemental content of the placenta: A comparison between two high-risk obstetrical populations, adult women carrying multiples and adolescents carrying singletons

Background: The placenta is responsible for the exchange of nutrients and for preventing harmful compounds from entering the fetal circulation. With increasing industrialization, exposures to commercial and toxic metals become a concern for both pregnant women and those planning a pregnancy. The understanding of transport mechanisms and pharmacokinetics for most inorganic elements is incomplete and limited to normal term deliveries. Objectives: To obtain novel data on 46 inorganic elements in placentae from two high-risk obstetric populations, women carrying multiples and adolescents carrying singletons, evaluating differences, if present, and identifying predictors of placental content. Methods: Placental tissue was collected from adolescents carrying singletons and adults carrying multiples. Elemental content was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). Multivariate regression and factor analyses were used. Results: With the exception of Au and Pt, almost all placentae contained quantifiable concentrations of each element analyzed. All placentae contained the essential elements Ca, Fe, Mg, Se and Zn, which clustered together onto the same factor. Most elements were higher in placentae from women carrying multiples. Differences in placental content disappeared after adjusting for maternal age. Rare earth elements (REEs) clustered together and remained higher in the multiples even after adjusting for maternal age. Conclusion: Human placentae contain a wide range of elements, including REEs. Ranges differed considerably between cohorts. Elements with similar chemical properties, like REEs or nutritionally essential elements, clustered together. Maternal age, and therefore longer environmental exposure, was significantly associated with elevated element concentrations in the placenta. Placental concentrations of several metals that are known to be nutritionally essential (e.g., Fe, Ca, Mg, and Zn) did not differ significantly between cohorts, suggesting tight regulation, whereas concentrations of environmental contaminants differed significantly between groups, even after adjusting for maternal age. - Highlights: • Levels of 46 elements were measured in placentae from two high-risk cohorts. • Almost all placentae contained traces of the 46 elements, including REEs. • Maternal age was significantly associated with concentrations in the placenta. • Elements with similar properties and roles clustered together.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Demonstration of low-level biogenic fuel content using quench curve and direct liquid scintillation counting (LSC) methods

In this work, an investigation into the direct method for liquid scintillation counting (LSC) quantification of biogenic fuel content in fuel blendstock is presented. This method development intentionally used a colored matrix (~99 wt%), fossil diesel fraction, and low-level biogenic fractions (~1 wt%) to determine the applicability of the LSC technique in colored blend mixtures. LSC procedures for quench correction, including the use of an instrument internal standard (Quantulus SQP values), color quench curves, and an internal 14 C standard spike on samples containing low-level amounts of biogenic gasoline, jet, and diesel mixed with fossil fuel, were compared. Samples were analyzed on both Perkin-Elmer Quantulus and Tri-Carb instruments, and the 14 C contents were compared with those determined by accelerator mass spectrometry (AMS). Results from the Tri-Carb instrument showed that percent differences of <10 % compared to AMS-reported values are achievable at 5-hour count times despite colored samples. A comparison between the impact of chemical and color quenching in the fuel samples showed that color quenching in highly colored samples reduces efficiency significantly more than chemical quenching, indicating that chemical quench curves are not appropriate for highly colored biofuel/fossil-fuel blended samples. Results indicate that both the direct method with internal spike quench correction and the use of a color-quench curve provide accurate results for 1 % biogenic fuel blends. Additionally, we have explored the use of Fourier transform infrared (FTIR) spectroscopy in measuring the biogenic content of the colored blended fuel samples. Preliminary results show the presence of biogenic carbon-derived fingerprints that are absent in fossil-derived sample. However, further work is needed to develop an FTIR-based quantitative method.

09 BIOMASS FUELS↗
DOE OSTI2012

Structure and Dynamics of Forsterite-scCO2/H2O Interfaces as a Function of Water Content

Molecular dynamics (MD) simulations of forsterite surfaces in contact with supercritical carbon dioxide (scCO2) fluids of varying water content were performed to determine the partition of water between the scCO2 fluid and the mineral surface, the nature of CO2 and H2O bonding at the interface, and the regions of the interface that may be conducive to HxCO3(2-x)- formation. Calculations of the free energy of the associative adsorption of water onto the (010) forsterite surface from the scCO2 phase indicated that the formation of a water film up to three-monolayer thick can be exothermic even for water contents below the water saturation concentration of the scCO2 fluid. In MD simulations of scCO2/H2O mixtures in contact with the (010) forsterite surface, H2O was found to readily displace CO2 at the surface and, therefore, CO2 directly contacted the surface only for water coverages below two monolayers. For thicker water films, a two-monolayer hydration layer formed that CO2 could not penetrate. Simulations of the hydroxylated (010) surface and of the (011) surface suggested that this conclusion can be extended to forsterite surfaces with different surface structures and/or compositions. The density, diffusion, and degree of hydration of CO2 as well as the extent of CO2/H2O mixing at the interface were all predicted to depend strongly on the thickness of the water-rich film, i.e., on the water content of the scCO2 fluid.

58 GEOSCIENCES↗
DOE OSTI2017

Quantification of triglyceride content in oleaginous materials using thermo-gravimetry

Laboratory analytical methods for quantification of triglyceride content in oleaginous biomass samples, especially microalgae, require toxic chemicals and/or organic solvents and involve multiple steps. We describe a simple triglyceride quantification method that uses thermo-gravimetry. This method is based on the observation that triglycerides undergo near-complete volatilization/degradation over a narrow temperature interval with a derivative weight loss peak at 420 °C when heated in an inert atmosphere. Degradation of the other constituents of oleaginous biomass (protein and carbohydrates) is largely complete after prolonged exposure of samples at 320 °C. Based on these observations, the triglyceride content of oleaginous biomass was estimated by using the following two-step process. In Step 1, samples were heated to 320 °C and kept isothermal at this temperature for 15 min. In Step 2, samples were heated from 320 °C to 420 °C and then kept isothermal at 420 °C for 15 min. The results show that mass loss in step 2 correlated well with triglyceride content estimates obtained from conventional techniques for diverse microalgae and oilseed samples.

09 BIOMASS FUELS↗
DOE OSTI2021

Effects of aluminum content on thermoelectric performance of Al x CoCrFeNi high-entropy alloys

Introducing a non-regular distribution in the mass and bonding by including distinctly different elements can reduce the phonon transport even within structurally well-ordered materials. These distributions are a quality of all high-entropy alloys (HEAs), however the inclusion of aluminum in Al x CoCrFeNi is particularly impactful due to the large mismatch in atomic mass with other components. The resultant low phonon conductivity is a requirement for high thermoelectric performance, motivating the investigation of the effects of Al content on phonon transport as well as other thermoelectric properties. This work examines the phonon and electron transport and thermoelectric conversion properties with various Al contents (0 ≤ x Al ≤ 2) in this Cantor alloy using first-principles calculations, molecular dynamics, and semi-classical Boltzmann transport theory. The calculated phonon density of states and thermoelectric properties present reasonable agreements with experiments, including neutron scattering. A large reduction of phonon conductivity (k L ) is observed even with low x Al s, which we attribute to effective phonon scatterings by the large mass mismatch. However, its temperature dependence is not significant, demonstrating a minor contribution of interphonon scattering. In contrast, electrical conductivity (σ) and Seebeck coefficient (S) increase with temperature at higher x Al s with body-centered cubic structures. Therefore, the thermoelectric figure of merit (ZT) of Al x CoCrFeNi HEAs is enhanced by increasing the Al content mainly due to the increase of the thermoelectric power factor (σS 2 ) at high temperatures, while at low temperatures the phonon-scattering enhancement by mass mismatch is also important.

36 MATERIALS SCIENCE↗