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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

MR-guided Neurolytic Celiac Plexus Ablation: An Evaluation of Effect and Injection Spread Pattern in Cancer Patients with Celiac Tumor Infiltration

ObjectiveThe purpose of this study was to evaluate the feasibility, the initial accuracy, and the effects of the MR-guided neurolytic celiac plexus ablation as a method to treat cancer-induced chronic abdominal pain. Thirteen celiac plexus ablations were performed for 12 patients. A 0.23-T open MRI scanner with optical navigation was used for procedural guidance. As an adjunct to the MR-guided needle positioning, the needle location was confirmed with saline injection and consequent MR imaging (STIR sequence). The spread of the ablative injection material (alcohol-lidocaine mix) was observed by repeating this sequence after the therapeutic injection. Pain scores from seven patients (eight ablations) were used to assess the therapy effect. MR guidance allowed adequate needle positioning and visualization of injection material in all cases. The rest pain scores significantly decreased from 4 (median) at baseline to 1 (median) at 2 weeks (p < 0.05). Average and worst pain experienced during the past week were significantly lower at the 2-week time point compared with the baseline (p < 0.05). However, the intervention did not result in reduction of opioid use at 2 weeks.MR guidance is an accurate and safe method for celiac plexus ablation with positive therapeutic effect.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Fog Formation Related to Gravity Currents Interacting with Coastal Topography

An interesting mixing-fog event was identified during IOP7 of the C-FOG project, where a cold front arriving from the north-east collided with the Downs peninsula in Ferryland, Newfoundland, to produce foggy conditions. A comprehensive set of field observations suggests that this collision caused turbulent mixing of nearly saturated ambient air with an almost saturated cold front, creating conditions for mixing fog. Additionally, laboratory experiments were performed to study the interaction of lock-exchange induced gravity currents with a (rectangular) obstacle to delve into physical processes underlying this phenomenon. Instantaneous velocity and density fields were obtained using particle image velocimetry and planar laser-induced fluorescence. The observations suggest that the obstacle starts affecting the approaching gravity-current propagation at an upstream distance of 2 H and, upon collision, the mixing is taking place over a spatial scale of 0.83 H , where H is the depth of the ambient fluid layer. The time for largerscale turbulent stirring to permeate to the smallest scales of turbulence and activate the condensation nuclei was estimated as 3t * , where t* = √H/g' is the intrinsic time scale of the gravity current and g' the reduced gravity. Extrapolation of results to IOP7 showed a good agreement with observations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Fischer–Tropsch Synthesis: Effect of Reducing Agent for Aqueous-Phase Synthesis Over Ru Nanoparticle and Supported Ru Catalysts

The effect of the reducing agent on the performance of a ruthenium nanoparticle catalyst was investigated during aqueous-phase Fischer–Tropsch synthesis using a 1 L stirred tank reactor in the batch mode of operation. For the purpose of comparison, the activity and selectivity of NaY zeolite supported Ru catalyst were also studied. NaBH 4 and hydrogen were used as reducing agents in our study, and hydrogen reduced catalysts exhibited higher activities than the NaBH 4 reduced catalysts, because of higher extent of reduction and a relatively lower tendency toward agglomeration of Ru particles. The Ru nanoparticle catalyst displayed higher activities than the NaY zeolite supported Ru catalyst for both reducing agents. NaBH 4 reduced catalysts are less active and the carbon dioxide selectivity is higher than the hydrogen reduced catalysts. The activity of the supported Ru catalyst (Ru/NaY) was 75 % of that of the Ru nanoparticle catalyst, and has the benefit of easy wax/catalyst slurry separation by filtration. Finally, the hydrogen reduced supported Ru catalyst exhibited superior selectivity towards hydrocarbons (higher C 5+ selectivity and lower selectivity to methane) than all other catalysts tested.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Synthesis of Highly Dispersed and Highly Stable Supported Au–Pt Bimetallic Catalysts by a Two-Step Method

Highly dispersed and highly stable supported bimetallic catalysts were prepared using a two-step process. Pt nanoparticles (NPs) were first deposited on porous γ-Al2O3 particles by atomic layer deposition (ALD). Au NPs were synthesized by using gold(III) chloride as the Au precursor, and then immobilized on ALD Pt/γ-Al2O3 particles. The Au–Pt bimetallic catalysts were highly active and highly stable in a vigorously stirred liquid phase reaction of glucose oxidation.

Wang, Xiaofeng↗
DOE OSTI2019

Synthesis and Characterization of Magnetic Halloysite–Alginate Beads for the Removal of Lead(II) Ions from Aqueous Solutions

In this study, alginate (ALG) hybrid spheres supported with magnetic halloysite nanotubes (MHNTs) were synthesized and used effectively in the removal of Pb(II) ions from aqueous solutions. MHNTs were prepared using the “co-precipitation” method. Afterward, magnetic halloysite–alginate (MHNT–ALG) hybrid beads were formed using ALG and MHNTs by the “extrusion dripping” method. The characterization of halloysite nanotubes (HNTs), ALG, MHNTs, and MHNT–ALG hydrogels was performed using FTIR, TGA, particle size analysis, SEM–EDX, TEM, VSM, and BET. According to VSM measurements, the saturation magnetization values of MHNTs and MHNT–ALG hybrid beads at a mass ratio of 1:2 were determined to be 22.7 emu/g and 8.17 emu/g, respectively. The BET surface area of MHNT–ALG hybrid beads was measured to be 81.3 m{sup 2}/g. The adsorption of Pb(II) ions on MHNT–ALG hydrogels was investigated as a function of the pH of the medium, amount of MHNT–ALG, the mass ratio of MHNT to ALG in the composite, and initial Pb(II) concentration in batch stirred vessels. The fit of the adsorption equilibrium of Pb(II) ions on MHNT–ALG hydrogels to the Langmuir type-I and type-II models, Freundlich model, and Redlich–Peterson model was investigated. The fit of the adsorption kinetics to the pseudo-second-order kinetics model was evaluated. Using the Weber and Morris model, the effect of internal and external diffusion limitations was discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Engineering of large-pore lipid-coated mesoporous silica nanoparticles for dual cargo delivery to cancer cells

Lipid-coated mesoporous silica nanoparticles (LC-MSNs) have recently emerged as a next-generation cargo delivery nanosystem combining the unique attributes of both the organic and inorganic components. The high surface area biodegradable inorganic mesoporous silica core can accommodate multiple classes of bio-relevant cargos in large amounts, while the supported lipid bilayer coating retains the cargo and increases the stability of the nanocarrier in bio-relevant media which should promote greater bio-accumulation of LC-MSNs in cancer sites. In this paper, we report on the optimization of various sol–gel synthesis (pH, stirring speed) and post-synthesis (hydrothermal treatment) procedures to enlarge the MSN pore size and tune the surface chemistry so as to enable loading and delivery of large biomolecules. Finally, the proof of concept of the dual cargo-loaded nanocarrier has been demonstrated in immortalized cervical cancer HeLa cells using MSNs of various fine-tuned pore sizes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Fischer-Tropsch Synthesis: Influence of CO Conversion on Selectivities H2/CO Usage Ratios and Catalyst Stability for a 0.27 percent Ru 25 percent Co/Al2O3 using a Slurry Phase Reactor

The effect of CO conversion on hydrocarbon selectivities (i.e., CH{sub 4}, C{sub 5+}, olefin and paraffin), H{sub 2}/CO usage ratios, CO{sub 2} selectivity, and catalyst stability over a wide range of CO conversion (12-94%) on 0.27%Ru-25%Co/Al{sub 2}O{sub 3} catalyst was studied under the conditions of 220 C, 1.5 MPa, H{sub 2}/CO feed ratio of 2.1 and gas space velocities of 0.3-15 NL/g-cat/h in a 1-L continuously stirred tank reactor (CSTR). Catalyst samples were withdrawn from the CSTR at different CO conversion levels, and Co phases (Co, CoO) in the slurry samples were characterized by XANES, and in the case of the fresh catalysts, EXAFS as well. Ru was responsible for increasing the extent of Co reduction, thus boosting the active site density. At 1%Ru loading, EXAFS indicates that coordination of Ru at the atomic level was virtually solely with Co. It was found that the selectivities to CH{sub 4}, C{sub 5+}, and CO{sub 2} on the Co catalyst are functions of CO conversion. At high CO conversions, i.e. above 80%, CH{sub 4} selectivity experienced a change in the trend, and began to increase, and CO{sub 2} selectivity experienced a rapid increase. H{sub 2}/CO usage ratio and olefin content were found to decrease with increasing CO conversion in the range of 12-94%. The observed results are consistent with water reoxidation of Co during FTS at high conversion. XANES spectroscopy of used catalyst samples displayed spectra consistent with the presence of more CoO at higher CO conversion levels.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Numerical and Experimental Modeling of the Recirculating Melt Flow Inside an Induction Crucible Furnace

In the paper, a new water model of the turbulent recirculating flow in an induction furnace is introduced. The water model was based on the principle of the stirred vessel used in process engineering. The flow field in the water model was measured by means of particle image velocimetry in order to verify the model’s performance. Here, it is indicated that the flow consists of two toroidal vortices similar to the flow in the induction crucible furnace. Furthermore, the turbulent flow in the water model is investigated numerically by adopting eddy-resolving turbulence modeling. The two toroidal vortices occur in the simulations as well. The numerical approaches provide identical time-averaged flow patterns. Moreover, a good qualitative agreement is observed on comparing the experimental and numerical results. In addition, a numerical simulation of the melt flow in a real induction crucible furnace was performed. The turbulent kinetic energy spectrum of the flow in the water model was compared to that of the melt flow in the induction crucible furnace to show the similarity in the nature of turbulence.

36 MATERIALS SCIENCE↗
DOE OSTI2018

CFD Modeling of Boron Removal from Liquid Silicon with Cold Gases and Plasma

The present study focuses on a specific step of the metallurgical path of purification to provide solar-grade silicon: the removal of boron through the injection of H{sub 2}O(g)-H{sub 2}(g)-Ar(g) (cold gas process) or of Ar-H{sub 2}-O{sub 2} plasma (plasma process) on stirred liquid silicon. We propose a way to predict silicon and boron flows from the liquid silicon surface by using a CFD model (©Ansys Fluent) combined with some results on one-dimensional diffusive-reactive models to consider the formation of silica aerosols in a layer above the liquid silicon. The comparison of the model with experimental results on cold gas processes provided satisfying results for cases with low and high concentrations of oxidants. This confirms that the choices of thermodynamic data of HBO(g) and the activity coefficient of boron in liquid silicon are suitable and that the hypotheses regarding similar diffusion mechanisms at the surface for HBO(g) and SiO(g) are appropriate. The reasons for similar diffusion mechanisms need further enquiry. We also studied the effect of pressure and geometric variations in the cold gas process. For some cases with high injection flows, the model slightly overestimates the boron extraction rate, and the overestimation increases with increasing injection flow. A single plasma experiment from SIMaP (France) was modeled, and the model results fit the experimental data on purification if we suppose that aerosols form, but it is not enough to draw conclusions about the formation of aerosols for plasma experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Adiabatic Shear Localization and Microstructure in Ultrafine Grained Aluminum Alloy at Cryogenic Temperature

Adiabatic shear localization plays an important role in the deformation and failure of ultrafine grained 6061 aluminum alloy processed by friction stir processing. To understand the effects of temperature and strain on adiabatic shear localization in the ultrafine grained 6061 aluminum alloy, it has been investigated dynamic mechanical behavior of ultrafine grained 6061 aluminum alloy under the controlled shock loading experiments. Deformation characteristics and microstructures in the shear band were performed by optical microscopy and transmission electron microscopy. The shear band in the ultrafine grained aluminum alloy is a long and straight band distinguished from the matrix. The width of the shear band decreases with increasing nominal strain. The results show that the grains in the boundary of the shear band are highly elongated along the shear direction and form the elongated cell structures (0.2 μ in width), and the core of the shear band consists of a number of recrystallized equiaxed grains 0.2-0.3 μ in diameters and the second phases distribute in both the boundary and the inner of the equiaxed new grains. The calculated temperature in the shear band is about 692 K. Rotational dynamic recrystallization mechanism is responsible for the formation of the microstructure in the shear band.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Aluminum Addition on the Evolution of Microstructure, Crystallographic Texture and Mechanical Properties of Single Phase Hexagonal Close Packed Mg-Li Alloys

In the present investigation, an effort has been made to understand the effect of aluminum addition to α Mg-Li alloys. The corresponding composition Mg-4Li-xAl (x = 0, 2, 4 and 6 wt.%) alloys have been prepared by stir casting route under an argon environment. Extrusion was carried out at 300 °C with the extrusion ratio of 15:1. Significant grain refinement was observed after extrusion. X-ray diffraction-based investigation of the cast and extruded alloys showed the presence of intermetallic compounds such as Mg{sub 17}Al{sub 12} and AlLi in the Al-rich alloys namely, Mg-4Li-xAl (x = 4 and 6 wt.%). These precipitates were also present in the extruded plus annealed samples, indicating the stability of the precipitates at high temperature. The bulk x-ray texture measurement revealed a crystallographic texture where the c-axis of the h.c.p crystals was perpendicular to the extrusion direction (ED) for extruded sample. A texture transition was observed on annealing. The c-axis was oriented parallel to the ED. Mechanical properties of the cast, extruded and extruded plus annealed material illustrate that the addition of Al led to enhancement in hardness, yield strength and ultimate tensile strength.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Exchanging Advancing and Retreating Side Materials on Mechanical Properties and Electrochemical Corrosion Resistance of Dissimilar 6013-T4 and 7003 Aluminum Alloys FSW Joints

Friction stir welding (FSW) was used to weld dissimilar joints between Al 6013-T4 and Al7003 alloys in this work. The effect of exchanging advancing (AS) and retreating (RS) side material on microstructure, mechanical behaviors and electrochemical corrosion resistance was discussed. Results showed that different joint cross sections were obtained when exchanging AS and RS materials. The material on the AS would be more deformed during the welding process. When the Al6013 placed on the AS, the plastic flow of weld is more sufficient. Whether on the AS or RS, the Al6013-T4 side is the weak region for both tensile specimens and hardness samples. The fracture position corresponds to the minimum hardness position. Also, more strengthening phase can be retained in the joint, and the joint of A6R7 has better corrosion resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of In Situ Intermetallics on the Microstructural Array and Saline Corrosion Performance of Cast Al/WCp Composites

Al-matrix composites, ex situ reinforced with WC nanoparticles and in situ reinforced with Al{sub 3}(Ti,W), Al{sub 12}W, Al{sub 5}W and Al{sub 4}W, have been fabricated by casting assisted by K{sub 2}TiF{sub 6} wetting agent addition and mechanical stirring. A satisfactory particle incorporation and distribution accompanied by a high reactivity have been attained. The presence, topography, chemical composition of all included phases and their occurrence as clusters or single particles are clarified and justified. Al{sub 12}W is the predominant aluminide phase at WC ≤ 1.5 vol.%. Al{sub 4}W (primarily) and Al{sub 5}W (secondarily) are the predominant aluminide phases at WC ≥ 2.0 vol.%. WC nanoparticles have acted as heterogeneous nucleation sites to Al{sub 3}Ti particles. Reverse polarization tests in 3.5 wt.% NaCl show that the governing form of corrosion is intergranular corrosion of Al around Al{sub 3}FeSi{sub 2} eutectic, fine plates. The corrosion steps/mechanisms are identified. Clusters of aluminides and carbide nanoparticles, as well as intergranular WC nano-dispersoids and their Al-matrix have remained corrosion-free. The role of the aluminides combined with WC remaining nano-cores as inhibitors of the eutectic Al{sub 3}FeSi{sub 2} cathodic activity is highlighted.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Fabrication of 7075-0.25Sc-0.15Zr Alloy with Excellent Damping and Mechanical Properties by FSP and T6 Treatment

This study investigated the effects of Sc and Zr additions, friction stir processing (FSP), and subsequent solid solution and artificial aging (T6) treatment on the microstructure, damping capacity, and mechanical properties of 7075 Al alloy. The minor Sc and Zr additions promoted the grain refinement of this alloy during FSP and inhibited the growth of fine equiaxed grains in the FSP sample during subsequent T6 treatment. Thus, the fine equiaxed grain structure and high density of the η′ precipitated phase were simultaneously obtained in the 7075 Al alloy containing Sc and Zr after FSP and T6 treatment, and this sample exhibited superior mechanical properties and damping capacity to those of the 7075 Al alloy after T6 treatment. This work provides an effective strategy for preparing Al alloys with excellent damping capacity and mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Process Parameter Optimization in Refill Friction Spot Welding of 6061 Aluminum Alloys Using Response Surface Methodology

6061-T6 aluminum alloy joint was fabricated by refill friction stir spot welding (RFSSW) on which three process parameters of tool rotation speed, sleeve moving rate, and plunge depth make an important effect. The response surface methodology (RSM) was applied to establish a mathematical model to study the effect of process parameters on lap shear fracture load (LSFL) of the RFSSWed joints which were performed in Box–Behnken designs with three factors, three levels and 15 runs. Analysis of variance used to check the adequacy of the developed model indicates that the mathematical model is significant. LSFL increases with the increase in tool rotation speed, sleeve plunge depth, and sleeve moving rate to maximum and then decreases. Sleeve plunge depth makes the most effect on LSFL in all process parameters. The RFSSW process parameters were also optimized using RSM to predict maximize LSFL. The joint produced using a tool rotational speed of 1506 rpm, sleeve moving rate of 1.01 mm/s and sleeve plunge depth of 2.46 mm displays higher LSFL.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of Cell Anisotropy and Relative Density on Compressive Deformation Responses of LM13-Cenosphere Hybrid Foam

This article deals with closed-cell aluminum alloy LM13-cenosphere hybrid foams (ACHFs) with cell anisotropy prepared through stir casing technique. The compressive deformation behavior of hybrid foams in both transverse and longitudinal directions was measured at a strain rate of 0.01/s. The hybrid foam loaded in longitudinal direction (LD) shows higher plastic collapse stress than that in transverse direction (TD). The stress drop ratio is also observed to be higher in the LD. The plastic collapse stress and energy absorption capacity of ACHFs follow the power law relationship with relative density in both the directions. The plateau stress is higher in case of LD and densification strains are marginally higher in case of LD than that in TD.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Synthesis and Characterization of Aluminum Matrix Composites Reinforced with (Ni,Cu){sub 3}Al Intermetallic Particles via Mechanical Milling Technique

This study investigates the dispersion of (Ni,Cu){sub 3}Al intermetallic particles in an aluminum matrix via low-energy mechanical milling as an alternative to conventional stir casting. The precursor powders consisted in (Ni,Cu){sub 3}Al and reactive-grade Al particles with an average size of 15 and 3 microns, respectively. The concentrations used were 3, 5, 8 and 10 wt.% of the intermetallic powders. After 4 h of milling, the obtained powders were compacted in a unidirectional press with a pressure of 930 MPa and the obtained green compacts were sintered at 500 °C in a controlled atmosphere oven for 2 h. Result showed that the bulk composites displayed an increase in the Vickers microhardness as well as an increase in compressive strength and stiffness as the percentage of dispersed particles increased. The Al-8 wt.%(Ni,Cu){sub 3}Al sample achieved the best performance and is related to the findings in SEM micrographs that showed that higher reinforcement concentration increased the formation of microporosities that reduce the decohesion of the bulk sample and impact heavily on the mechanical performance of the material.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structure and Properties of Epoxy/Fly Ash System: Influence of Filler Content and Surface Modification

Epoxy resin composites filled with pristine and organomodified fly ash were prepared and examined. The fly ash used is CaO-rich due to the origin of lignite from the northern Greece area and the power plants in Kozani. As matrix, the epoxy system with curing agent triethylenetetramine was used. A combination of mechanical stirring and ultrasonication was used for highly dispersed fly ash composites. SEM, FTIR spectroscopy and XRD measurements were used to study dispersion homogeneity, structure, degree of aggregation/agglomeration and interface formation of the matrix with the fly ash particles. The properties E′, E″ and relaxations α-(T{sub g}) and β-(Τ{sub β}) of the composites were assessed by DMA. Also, DSC and TGA measurements were used to characterize the thermal properties. Interesting results concerning the effect of the surface organomodification of fly ash on the network formation and the thermomechanical properties of the composites were derived. XRD and FTIR measurements reveal that the functional groups present on the surface of fly ash particles play a dominated role to interface formation. DMA results show that the fly ash surface modification affects the thermodynamic properties of the composites. Additionally, there is evidence showing that the short-scale β-relaxation is also affected by the fly ash surface organomodification.

36 MATERIALS SCIENCE↗