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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Anodization Compatibility of Eutectic Aluminum–Cerium Alloys

Anodizing is the most common method for producing corrosion resistant layer coatings for aluminum alloys. It is possible to use anodizing with most commercial aluminum alloys to increase material corrosion resistance, but often the brittle, passive oxide layer formed during anodization does not adhere well to the material, reducing effectiveness, and overall compatibility. Therefore, it is important for the compatibility and effect of anodization to be studied for any newly developed alloys. Recently developed eutectic Al–Ce alloys offer advantages like high castability, limited or no heat treatment requirements, and high-temperature strength retention. In this work, Al–Ce alloys are shown to have good compatibility with current processes and may exhibit improved adhesion of passivated layer because intermetallic phases anchor the anodized product to unconverted bulk. The source of these phenomena and their effect on material corrosion and layer adhesion properties of Al–Ce alloys will be discussed and compared with results from common commercial aluminum alloys.

Sims, Zachary↗
DOE OSTI2019

La2USe3S2: A Serendipitously Grown Lanthanide/Actinide Chalcogenide from a Eutectic Halide Flux

La 2 USe 3 S 2 , exact composition La 2 USe 2.96 S 2.04 , crystallized from a reaction between USe2 and La 2 S 3 in a molten CsCl/KCl eutectic flux and was characterized by single crystal X-ray diffraction. La 2 USe 3 S 2 crystallizes in the orthorhombic space group Pnma in the U 3 S 5 structure type with lattice parameters a = 12.3284(3) Å, b = 8.4028(2) Å, and c = 7.3452(2) Å. In La 2 USe 3 S 2 all the anion sites have mixed S and Se occupancy and, henceforth, will be simply referred to as Q sites. The compound exhibits sigmoidal sheets built from LaQ 8 (Q= S, Se) bicapped trigonal prisms that edge-share down the a-axis forming rectangular-shaped channels or tunnels. Lastly, these tunnels are occupied by UQ 6 (Q = S, Se) octahedra that edge-share to form infinite, one-dimensional chains running down the b-axis.

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

A study of deformation and strain induced in bulk by the oxide layers formation on a Fe-Cr-Al alloy in high-temperature liquid Pb-Bi eutectic

At elevated temperatures, heavy liquid metals and their alloys are known to create a highly corrosive environment that causes irreversible degradation of most iron-based materials. In this paper, it has been found that an appropriate concentration of oxygen in the liquid alloy can significantly reduce this issue by creating a passivating oxide scale that controls diffusion, especially if Al is present in Fe-based materials (by Al-oxide formation). However, the increase of the temperature and of oxygen content in liquid phase leads to the increase of oxygen diffusion into bulk, and to promotion of the internal Al oxidation. This can cause a strain in bulk near the oxide layer, due either to mismatch between the thermal expansion coefficients of the oxides and bulk material, or to misfit of the crystal lattices (bulk vs. oxides). This work investigates the strain induced into proximal bulk of a Fe-Cr-Al alloy by oxide layers formation in liquid lead-bismuth eutectic utilizing synchrotron X-ray Laue microdiffraction. Finally, it is found that internal oxidation is the most likely cause for the strain in the metal rather than thermal expansion mismatch as a two-layer problem.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Interface velocity dependent solute trapping and phase selection during rapid solidification of laser melted hypo-eutectic Al-11at.%Cu alloy

Microstructure formation of a hypo-eutectic Al-11Cu (atom percent) alloy during solidification after laser melting has been studied by transmission electron microscopy (TEM). The evolution of the solid-liquid-interface velocity, V SL , during the solidification process has been determined from direct observation by in-situ TEM. This enabled correlating V SL with development of four distinct microstructure zones. Crystal growth mode transitions from planar to cellular, cellular to dendritic, dendritic to cellular, and cellular to planar, have been observed for the accelerating solid-liquid-interface. The transition from coupled two-phase growth to the single-phase growth occurred for V SL = V a = (0.80±0.05) m/s, where V a is the velocity of absolute stability, at the onset of banded morphology grain formation. The in-situ and post-mortem TEM uniquely permitted determination of the non-equilibrium solidus for the rapidly solidifying Al-11Cu alloy. Experimental evidence for solute clustering and chemical ordering tendencies at length scales on the order of ≤ 5nm has been detected in the single-phase regions of the banded grains. The structural features of the single-phase bands have been interpreted as signatures of ‘frozen in’ configurations present in the liquid boundary layer adjacent to the growing crystal, which has a width of about 3nm. Finally, the nano-scale spatiotemporal resolution experimental TEM studies performed here provided quantitative metrics, e.g. the solidification interface velocity dependent solute concentration of the α-Al phase and the near-atomic scale structure in the single-phase bands, that are uniquely suitable for comparison with theory and model predictions for solidification microstructure development in multicomponent alloys after laser melting.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Atomistic modeling of interface strengthening in Al-Si eutectic alloys

Al-Si cast alloys are usually composed of α-Al and Al-Si eutectic. Si flakes and Al matrix generally hold cube-on-cube orientation relationship with the primary interface (111) Al ∥(111) Si . Extensive experimental studies demonstrated that Si flakes cannot significantly improve mechanical properties of Al-Si cast alloys. We hypothesize that the weak strengthening effect associated with Si flakes might be attributed to thermomechanical properties of Al-Si interfaces besides their morphologies. To characterize Al-Si interfaces with a large lattice mismatch (> 30%), we proposed the quasi-coincident site lattice (Q-CSL) as reference lattice, and demonstrated that the Q-CSL Al-Si coherent interface has three characteristic coherent structures, one stable and low energy structure and two metastable and high energy structures. The translation vectors for the same type of coherent Q-CSL structures are consistent with three displacement shift complete (DSC) vectors. The two metastable structures can be obtained by shifting the low energy structure with three partial DSC vectors. Semi-coherent interface is composed of the low energy Q-CSL patches and three sets of interface misfit dislocations with Burgers vectors same as the DSC vectors. Atomistic simulations revealed that Al-Si interface exhibits low shear resistance. Ideal shear strength of the Q-CSL coherent interface is 110 MPa and semi-coherent interface is 20 MPa. The low shear resistance is attributed to the glide of interface misfit dislocations. Al-Si interface also exhibits low formation and migration energies of point defects. Owing to low shear strength and low formation and migration energies of point defects, interface sliding or shear readily happen under mechanical loading or during dislocation-interface interactions. Lattice dislocations can cross slip onto or climb along Al-Si interfaces. These reactions decrease the number of accumulated dislocation loops around Si flakes and promote nucleation and emission of lattice dislocations from Al-Si interfaces to matrix, consequently reduce the repulsive force on approaching dislocations and weaken Si flakes strengthening effect. In situ tension and compression tests in a scanning electron microscope reveal relatively weak strengthening effect due to Si flakes, consistent with the computed dislocation interaction with interfaces and shear behavior of interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Deformation mechanisms in an additively manufactured dual-phase eutectic high-entropy alloy

Nanostructured metals and alloys often exhibit high strengths but at the expense of reduced ductility. Through harnessing the far-from-equilibrium processing conditions of laser powder-bed fusion (L-PBF) additive manufacturing, we develop a dual-phase nanolamellar structure comprised of FCC/L1 2 and BCC/B2 phases in a Ni 40 Co 20 Fe 10 Cr 10 Al 18 W 2 eutectic high-entropy alloy (EHEA), which exhibits a combination of ultrahigh yield strength (>1.4 GPa) and large tensile ductility (~17%). The deformation mechanisms of the additively manufactured EHEA are studied via in-situ synchrotron X-ray diffraction and high-resolution transmission electron microscopy. The high yield strength mainly results from effective blockage of dislocation motion by the high density of lamellar interfaces. The refined nanolamellar structures and low stacking fault energy (SFE) promote stacking fault (SF)-mediated deformation in FCC/L1 2 nanolamellae. The accumulation of abundant dislocations and SFs at lamellar interfaces can effectively elevate local stresses to promote dislocation multiplication and martensitic transformation in BCC/B2 nanolamellae. The cooperative deformation of the dual phases, assisted by the semi-coherent lamellar interfaces, gives rise to the large ductility of the as-printed EHEA. In addition, here we also demonstrate that post-printing heat treatment allows us to tune the non-equilibrium microstructures and deformation mechanisms. After annealing, the significantly reduced SFE and thicknesses of the FCC nanolamellae facilitate the formation of massive SFs. The dissolution of nano-precipitates in the BCC/B2 nanolamellae reduces spatial confinement and further promotes martensitic transformation to enhance work hardening. Our work provides fundamental insights into the rich variety of deformation mechanisms underlying the exceptional mechanical properties of the additively manufactured dual-phase nanolamellar EHEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A combination of deep eutectic solvent and ethanol pretreatment for synergistic delignification and enhanced enzymatic hydrolysis for biorefinary process

Here, a novel pretreatment system containing deep eutectic solvents and ethanol (DES-E) for synergistic carbohydrate conversion and delignification was reported in this study. The DES-E pretreatment resulted in an enhanced glucose yield compared to individual DES and ethanol pretreatment for the three tested biomass, including Broussonetia papyrifera, corn stover and pine. To further explore the delignification mechanism, the solubilized lignin and residual lignin from Broussonetia papyrifera was recovered and extracted, then thoroughly characterized. The highest total OH content was found in the DES-E solubilized lignin, which could be used as antioxidant. The presence of ethanol in pretreatment liquor could protect the β-O-4 substructure from breakage and reduce lignin condensation, which favors the subsequent enzymatic hydrolysis. Comparable glucose yield and delignification performance was achieved by recycled DES. DES-E pretreatment offers a promising method for lignin isolation and cellulose digestibility improvement simultaneously.

09 BIOMASS FUELS↗
DOE OSTI2022

Utilization of guaiacol-based deep eutectic solvent for achieving a sustainable biorefinery

This study proposed a renewable deep eutectic solvent (DES) pretreatment using lignin-derived guaiacol as the hydrogen bond donor. The DES showed excellent biomass fractionation efficiency after the incorporation of trace AlCl 3 as the reinforcer, which removed 79.1 % lignin while preserving more than 90 % glucan. The pretreated bamboo exhibited 96.2 % glucan enzymatic hydrolysis yield at only 110 °C. The physicochemical properties of the pretreated solids were comprehensively investigated to explain how the DES fractionation overcame the biomass recalcitrance. The regenerated lignin from the DES pretreatment was also analyzed, which revealed that lignin β-O-4 bond was significantly cleaved. In conclusion, this guaiacol-based DES could greatly contribute to establish a closed-loop biorefinery sequence with high lignin fractionation efficiency and great solvent recyclability.

09 BIOMASS FUELS↗
DOE OSTI2023

A novel mineral-acid free biphasic deep eutectic solvent/γ-valerolactone system for furfural production and boosting the enzymatic hydrolysis of lignocellulosic biomass

The failure of hemicellulose valorization in a deep eutectic solvent (DES) pretreatment has become a bottleneck that challenges its further development. Here, to address this issue, this study developed a DES/GVL (γ-valerolactone) biphasic system for effective hemicellulose-furfural conversion, enhanced cellulose saccharification and lignin isolation. The results indicated that the biphasic system could significantly improve the lignin removal (as high as 89.1%), 86.0% higher than the monophasic DES, accompanied by ~100% hemicellulose degradation. Notably, the GVL in the biphasic solvent restricted the condensation of hemicellulose degradation products, which as a result generated large amount of furfural in the pretreatment liquid with a yield of 68.6%. With the removal of hemicellulose and lignin, cellulose enzymatic hydrolysis yield was boosted and reached near 100%. This study highlighted that the novel DES/GVL is capable of fractionating the biomass and benefiting their individual utilization, which could provide a new biorefinery configuration for a DES pretreatment.

09 BIOMASS FUELS↗
DOE OSTI2018

Natural deep eutectic solvents for lignocellulosic biomass pretreatment: Recent developments, challenges and novel opportunities

Conversion of lignocellulosic biomass to fuels and chemicals has attracted immense research and development around the world. Lowering recalcitrance of biomass in a cost-effective manner is a challenge to commercialize biomass-based technologies. Deep eutectic solvents (DESs) are new ‘green' solvents that have a high potential for biomass processing because of their low cost, low toxicity, biodegradability, easy recycling and reuse. This article discusses the properties of DESs and recent advances in their application for lignocellulosic biomass processing. The effectiveness of DESs in hydrolyzing lignin-carbohydrate complexes, removing lignin/hemicellulose from biomass as well as their effect on biomass deconstruction, crystallinity and enzymatic digestibility have been discussed. Moreover, this review presents recent findings on the compatibility of natural DESs with enzymes and microorganisms.

09 BIOMASS FUELS↗
DOE OSTI2020

Electrical properties of thermal oxide scales on pure iron in liquid lead-bismuth eutectic

Here, the impedance behavior of pre-oxidized iron in liquid lead-bismuth eutectic (LBE) at 200 °C is studied using electrochemical impedance spectroscopy. The structures and resistance of oxide grown on iron oxidized in air at different temperatures and durations are compared. The results show that the resistance of the oxide film increases with increasing oxidizing temperature, due to the formation of a thicker scale and fewer defects. At the same temperature (600 °C), increasing the oxidation time can also reduce the defect concentration in the oxide film and improve the impedance of the oxide scale in LBE.

42 ENGINEERING↗
DOE OSTI2021

Effect of excess Mg to control corrosion in molten MgCl 2 and KCl eutectic salt mixture

Structural alloys may experience corrosion when exposed to molten chloride salts due to selective dissolution of active alloying elements. One way to prevent this is to make the molten salt reducing. For the KCl + MgCl 2 eutectic salt mixture, pure Mg can be added to achieve this. However, Mg can form intermetallic compounds with nickel at high temperatures, which may cause alloy embrittlement. This work shows that an optimum level of excess Mg could be added to the molten salt which will prevent corrosion of alloys like 316 H, while not forming any detectable Ni-Mg intermetallic phases on Ni-rich alloy surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Intergranular precipitation-enhanced wetting and phase transformation in an Al0.4CoCrFeNi high-entropy alloy exposed to lead-bismuth eutectic

We report after exposure to oxygen-poor (10 -13 –10 -14 wt%) liquid lead-bismuth eutectic (LBE) at 500 °C for 500 h, LBE penetrates more than one order of magnitude deeper in an FCC Al 0.4 CoCrFeNi high-entropy alloy (HEA) decorated with a network of BCC (Ni, Al)-rich intergranular (IG) precipitates than in a single-phase, FCC Al 0.3 CoCrFeNi HEA without the IG precipitate network. This deterioration of corrosion resistance is attributed to the energetic nature of the BCC/FCC interphase boundaries (IBs) and resultant IB wetting. The LBE ingress film selectively leaches nickel located at those low-indexed crystalline planes, resulting in phase transformation from FCC to BCC structure.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Lignin extraction and upgrading using deep eutectic solvents

Deep eutectic solvents (DESs) are a class of green solvents exhibiting low vapor pressure, high thermal stability,low toxicity, and biodegradability. These features make them attractive solvents for lignocellulosic biomassprocessing, especially for lignin valorization. DESs not only solubilize lignin from lignocellulose biomass, butalso confer extracted lignin with properties favorable to its further upgrading. This review summarizes recentadvances in biomass fractionation using DESs for lignin extraction. It also covers lignin upgrading in DESs interms of depolymerization and functionalization. The challenges of tailoring lignin properties by DESs for differentvalorization routes are also discussed.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Natural deep eutectic solvents (NADES) assisted deconstruction of oilcane bagasse for high lipid and sugar recovery

In a novel approach, metabolically engineered sugarcane “Oilcane” has been investigated for fractionation of lipid and cellulose-rich pulp, using certain Natural deep eutectic solvents (NADES). The exploration of eco- friendly solvents are at the forefront of harnessing the biofuel potential of modern bioenergy crops. For this, six combinations of NADES were prepared using choline chloride (ChCl) as HBA and lactic acid (LA), oxalic acid (OA) and glycerol (Gly) as HBD and were further explored for pretreatment of oilcane bagasse in a molar ratio of 1:1 and 1:2. The impact of NADES ratio, biomass loading (10–50%), residence time (1–2 h), and temperature (90–140 °C) were evaluated for delignification, lipid content, sugar release after enzymatic hydrolysis. The finding demonstrated that under the optimal condition of ChCl: LA (1:2 molar ratio), 140 °C with 2 h retention time, the lipid content in the pre-treated substrate was increased to 2.5-fold (~8% w/w) and > 80% glucose yield was achieved after 72 h of hydrolysis of pre-treated bagasse. High solid loading (~50%) during pretreatment resulted in a similar glucose yield. Furthermore, recycling studies demonstrated that nearly 95 to 98% NADES could be recycled after each pretreatment for up to five consecutive cycles without any significant loss in chemical structure as confirmed by 1 H NMR and FT IR. FT IR and XRD analyses of native and pre-treated biomass were performed to visualize the morphological changes during NADES pretreatment and their impact on sugar yield. The findings of the study may be used to establish NADES-based biorefinery for the valorization of lipids, and carbohydrates for fuels and chemicals production.

09 BIOMASS FUELS↗
DOE OSTI2021

Influence of fine-scale B2 precipitation on dynamic compression and wear properties in hypo-eutectic Al0.5CoCrFeNi high-entropy alloy

The near equiatomic high-entropy alloys based on Al, Co, Cr, Fe, Ni have provided a novel microstructural template for alloy design. The face-centered cubic (FCC) matrix strengthened by body-centered cubic (BCC) based ordered B2 precipitates can be used to develop a new generation of precipitation strengthened alloys. The present study focuses on an Al0.5CoCrFeNi hypo-eutectic alloy consisting of an as-solidified FCC+B2 microstructure. Guided by solution thermodynamic modeling, this alloy has been isothermally aged for solid-state precipitation of a high fraction of fine-scale intragranular B2 particles. The dynamic compressive strength, hardness, and sliding wear response of the alloy as a function of B2 phase fraction is examined. The flow stress at 0.02% true strain increased from ~ 670 MPa to ~1350 (102%) MPa, the ultimate compressive strength increased from ~1160 MPa to 1500 MPa (20%), and the wear resistance increased more than 5 times with progressively increasing phase fraction of B2 precipitates.

Gwalani, Bharat↗
DOE OSTI2023

Effect of Mn on eutectic phase equilibria in Al-rich Al-Ce-Ni alloys

Microstructural analysis of additively manufactured (AM) Al-Ce-Ni-Mn alloys has identified phases not predicted from existing ternary liquidus projections in the Al-Ce-Ni system. Because the rapid cooling rate of AM is orders of magnitude above that of traditional casting, it is unclear if these additional phases arose from the non-equilibrium processing conditions of AM, a drastic shift in phase stability in the system due to the addition of 1 wt% Mn, or some combination of these two influences. The phases and microstructure of cast samples of Al-Ce-Ni and Al-Ce-Ni-Mn alloys were characterized for several annealing conditions which revealed the equilibrium phases at different temperatures. Phase analysis confirmed that minute levels of Mn substituted for Ni in the system drastically shifts the liquidus projection in the Al-rich corner of the ternary phase diagram such that the eutectic Al 3 Ni phase is suppressed in favor of the Al 23 Ni 6 (Ce,Mn) 4 phase. Further addition of Mn promotes the formation of Al 20 Mn 2 Ce and Al 10 Mn 2 Ce phases. The phase analysis data was then used to improve the CALPHAD modeling of the liquidus projection and isothermal sections for the Al-rich Al-Ce-Ni-Mn quaternary system. Thermodynamic modeling and experimental analysis on phases in the AM sample of Al-Ce-Ni with Mn confirmed that the phases present are consistent with Mn-containing Al-Ce-Ni cast samples. Here, this investigation demonstrates the potential for using secondary alloying elements to drastically alter phase stability and microstructure in alloy systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structural evolution of low-temperature liquid GaIn eutectic alloy

Structural changes of liquid Galn eutectic alloy upon cooling from about 373 K to 242 K are studied by using in situ synchrotron radiation X-ray diffraction (XRD) combined with the ab initio molecular dynamics simulations (AIMD). The experimental and theoretical results show that no abnormal structural change is observed in the supercooled liquid region prior to crystallization. The XRD data exhibit that the liquid can crystallize into a mixture of orthorhombic Ga-I and body-centered tetragonal (bct)-In phases. Also, the AIMD calculations simulate the solidification process, forming a bct-like structure locally similar to bct-Ga-III and bct-In phases. The aggregation of In atoms forms In-rich zones, acting as the processor of crystallization. Our results provide an in-depth understanding of liquid Galn alloys and will trigger more interests to other metallic liquids. (C) 2019 Elsevier B.V. All rights reserved.

36 MATERIALS SCIENCE↗