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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Preparation and characterization of the rod-shaped stibnite

Highlights: • A facile route to synthesize large-scale rod-like Sb{sub 2}S{sub 3} micro-wires was presented. • A deep analysis conjoint between band tails, band gap alteration and electrical model. • The band gap is 1.75 eV which may hold for solar energy conversion. - Abstract: Stibnite (Sb{sub 2}S{sub 3}) micro-wires have been grown on glass substrates by sulfuration of Sb thermal evaporated film in a vacuum sealed tube in presence of sulfur powder at 300 °C for 6 h. X-ray diffraction and Raman spectroscopy techniques indicate that the synthesized micro-wires have an orthorhombic structure. SEM micrographs show rod-shaped micro-wires with a typical length of several tens of micrometers and a diameter of the order of 0.5 μm. The absorption coefficient dependence on the photon energy in the UV–visible range revealed the existence of a direct transition with an energy band gap of about 1.7 eV. Moreover, the band tails and localized states which are related to the level of defects in the material will be presented. These parameters were determined from the exponential absorption profile. All these results have been evaluated and discussed in terms of alteration of band gap edge and electrical measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Auto-combustion synthesis and characterization of Mg doped CuAlO{sub 2} nanoparticles

The synthesis of pure and Mg doped Copper aluminumoxide CuAlO{sub 2}nanoparticles, a promising p-type TCO (transparent conducting oxide) have been done bysol gel auto combustion method using NaOH as a fuel, calcinated at 600°C. The structural properties were examined by XRD and SEM techniques. The optical absorption spectra of CuAlO{sub 2} sample recorded by UV-VIS spectrophotometer in the range of 200 to 800 nm have been presented. The crystallite size was determined by powder X-ray diffraction technique. The electrical behavior of pure and Mg doped CuAlO{sub 2} has been studied over a wide range of frequencies by using complex impedance spectroscopy.The variation of a.c. conductivity has been studied as function of frequency and temperature. The data taken together conclude that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. Mg doping affects the optical properties and band gap.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Dielectric and magnetic properties of microwave-absorbing FeAl x O y catalysts fabricated via solution combustion synthesis

Iron-based alumina (FeAl x O y ) nanocomposites are microwave-absorbers and catalysts, which makes them promising for emerging microwave-assisted thermocatalytic technologies. Solution combustion synthesis (SCS) has been used to synthesize FeAl x O y powders, and prior work has demonstrated that adjusting SCS parameters significantly changes phase composition and specific surface area of the products. However, it is unclear how synthesis parameters affect their microwave-absorbing properties, which are essential for optimizing microwave-assisted technologies. To address this challenge, in the present work, twelve different FeAl x O y products were synthesized at different combinations of the SCS parameters such as two fuels (citric acid and glycine), two heating modes (hotplate and muffle furnace), and three Fe:Al molar ratios (2:1, 1:1, 1:2). Dielectric and magnetic properties of the products were characterized using a network analyzer and a vibrating sample magnetometer. Based on the measured permittivity and permeability, penetration depth and reflection loss were calculated as a function of frequency and bed thickness. The products were heated by microwaves at 2.45 GHz and then examined with X-ray diffraction (XRD) analysis. For all products, the magnetic saturation was lower than for bulk iron oxides because of the small crystallite size and aluminum substitution. The use of glycine induced high dielectric losses and enabled fast microwave-heating rates compared to citric acid. Higher Fe:Al ratio also led to higher dielectric and magnetic losses. With glycine fuel, SCS in a furnace induced larger penetration depth and lower microwave absorption than SCS on a hotplate. The minimization of reflected power was more sensitive to the thickness of the product bed than to the frequency of the electromagnetic field. Post-heating XRD analysis revealed different phase transformations in the FeAl x O y powders depending on the SCS parameters. As a result, an FeAl x O y material, synthesized via incipient wetness impregnation, lacked magnetic losses and did not heat well as compared to the SCS products.

Combustion synthesis↗
DOE OSTI2021

Giant and Reversible Barocaloric Effect in Trinuclear Spin–Crossover Complex Fe 3 (bntrz) 6 (tcnset) 6

A giant barocaloric effect (BCE) in a molecular material Fe 3 (bntrz) 6 (tcnset) 6 (FBT) is reported, where bntrz = 4-(benzyl)-1,2,4-triazole and tcnset = 1,1,3,3-tetracyano-2-thioethylepropenide. The crystal structure of FBT contains a trinuclear transition metal complex that undergoes an abrupt spin-state switching between the state in which all three FeII centers are in the high-spin (S = 2) electronic configuration and the state in which all of them are in the low-spin (S = 0) configuration. Despite the strongly cooperative nature of the spin transition, it proceeds with a negligible hysteresis and a large volumetric change, suggesting that FBT should be a good candidate for producing a large BCE. Powder X-ray diffraction and calorimetry reveal that the material is highly susceptible to applied pressure, as the transition temperature spans the range from 318 at ambient pressure to 383 K at 2.6 kbar. Despite the large shift in the spin-transition temperature, its nonhysteretic character is maintained under applied pressure. Such behavior leads to a remarkably large and reversible BCE, characterized by an isothermal entropy change of 120 J kg –1 K –1 and an adiabatic temperature change of 35 K, which are among the highest reversible values reported for any caloric material thus far.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Design of Silicide-Strengthened Nb–Si–Cr–(Mo) alloys for additive manufacturing

Three high–intermetallic volume Nb–Si–Cr–(Mo) alloys were designed using CALPHAD modeling with the goal of identifying high–specific strength, oxidation-resistant alloys that can be additively manufactured using powder bed fusion. The silicides Nb 5 Si 3 and Nb 9 Si 2 Cr3 were targeted as the primary strengthening phases, and the addition of Cr promoted the NbCr 2 phase. These alloys were cast and surface-processed with electron beam welding at different speeds to simulate additive manufacturing, and the phases and microstructures of both cast and welded regions were characterized. The weld processing was found to produce fine-grained microstructures in each alloy with fine-scale intermetallics uniformly distributed among a body-centered cubic Nb matrix. Microstructural refinement and hardness were found to increase with weld velocity; one alloy reached its highest hardness of approximately 16 GPa before the brittleness at higher velocities became detrimental. One alloy was found to be qualitatively the least brittle while also attaining a hardness of 13 GPa and was therefore identified as a good candidate for additive manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Design and Characterization of Metal Nanoparticle Infiltrated Mesoporous Metal–Organic Frameworks

The infiltration of palladium and platinum nanoparticles (NPs) into the mesoporous metal–organic framework (MOF) CYCU-3 through chemical vapor infiltration (CVI) and incipient wetness infiltration (IWI) processes was systematically explored as a means to design novel NP@MOF composite materials for potential hydrogen storage applications. We employed a traditional CVI process and a new "green" IWI process using methanol for precursor infiltration and reduction under mild conditions. Transmission electron microscopy-based direct imaging techniques combined with synchrotron-based powder diffraction (SPD), energy-dispersive X-ray spectroscopy, and physisorption analysis reveal that the resulting NP@MOF composites combine key NP and MOF properties. Room temperature hydrogen adsorption capacities of 0.95 and 0.20 mmol/g at 1 bar and 2.9 and 1.8 mmol/g at 100 bar are found for CVI and IWI samples, respectively. Additionally, hydrogen spillover and/or physisorption are proposed as the dominating adsorption mechanisms depending on the NP infiltration method. Mechanistic insights were obtained through the crystallographic means using SPD-based difference envelope density analysis, providing previously underexplored details on NP@MOF preparations. Consequently, important host–guest correlations influencing the global hydrogen adsorption properties are discussed, and they demonstrate that employing MOFs as platforms for NPs is an alternative approach to the development of versatile materials for improving current hydrogen storage technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Design and synthesis of model and practical palladium catalysts using atomic layer deposition

Here, we investigated the “one-batch” synthesis of model and practical palladium catalysts using atomic layer deposition (ALD). Two types of model catalysts and one type of powder-based nanocatalyst were synthesized simultaneously by ALD under viscous flow conditions. In addition, Pd/TiO 2 (110) model catalysts were prepared by the identical ALD process but under ultrahigh vacuum conditions. Because of the self-limiting surface reaction that defines ALD, the local structure of all the Pd catalysts were essentially the same as confirmed by a suite of microscopic and spectroscopic characterization techniques. A comprehensive understanding of the Pd-based catalysts was achieved by applying both surface science probes and advanced synchrotron techniques, and by strategically selecting the catalyst substrate best suited for each characterization. Both X-ray absorption spectroscopy and X-ray resonant photoelectron spectroscopy suggested that Pd only weakly interacted with the TiO 2 support. The one-batch synthesis approach facilitated by ALD can potentially bridge the “synthesis gap” between model catalysts and practical catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Carbon nanotubes reinforced copper composite with uniform CNT distribution and high yield of fabrication

Dispersion of carbon nanotubes (CNTs) in metal matrix composites has been an unsolved issue since the discovery of CNTs. This paper presents a newly developed fabrication process of bulk Cu/CNT composite with uniformly distributed CNTs. That is, copper encapsulated CNTs powders were firstly fabricated by an electrochemical deposition where CNTs can be completely dispersed in the copper electrolyte assisted by sonication, and then the fabricated composite powders were used to make bulk Cu/CNT composite by a powder metallurgy process. The increment in microhardness of Cu/CNT composite after compaction and sintering was observed to be ~47.6% per 1% CNTs. The developed fabrication process of Cu/CNT composite powders by electrochemical co-deposition can be scaled up to meet specific application needs, and a similar process is expected to be applicable for other metals.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Investigation of the structure and properties of boron-containing coatings obtained by electron-beam treatment

An investigation of surface-hardened materials obtained by cladding with an electron beam injected into the air atmosphere was carried out. Structural investigations of coatings revealed that an increase in boron carbide concentration in a saturating mixture contributed to a rise of a volume fraction of iron borides in coatings. The maximum hardened depth reached 2 mm. Hardened layers were characterized by the formation of heterogeneous structure which consisted of iron borides and titanium carbides distributed uniformly in the eutectic matrix. Areas of titanium boride conglomerations were detected. It was found that an increase in the boron carbide content led to an enhancement in hardness of the investigated materials. Friction testing against loosely fixed abrasive particles showed that electron-beam cladding of powder mixtures containing boron carbides, titanium, and iron in air atmosphere allowed enhancing a resistance of materials hardened in two times.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Characterization of Morphology using MAMA Software

The MAMA (Morphological Analysis for Material Attribution) software was developed at the Los Alamos National Laboratory funded through the National Technical Nuclear Forensics Center in the Department of Homeland Security. The software allows images to be analysed and quantified. The largest project I worked on was to quantify images of plutonium oxides and ammonium diuranates prepared by the group with the software and provide analyses on the particles of each sample. Images were quantified through MAMA, with a color analysis, a lexicon description and powder x-ray diffraction. Through this we were able to visually see a difference between some of the syntheses. An additional project was to revise the manual for MAMA to help streamline training and provide useful tips to users to more quickly become acclimated to using the software. The third project investigated expanding the scope of MAMA and finding a statistically relevant baseline for the particulates through the analysis of maps in the software and using known measurements to compare the error associated with the software. During this internship, I worked on several different projects dealing with the MAMA software. The revision of the usermanual for the MAMA software was the first project I was able to work and collaborate on. I first learned how to use the software by getting instruction from a skilled user at the laboratory, Dan Schwartz, and by using the existing user manual and examples. After becoming accustomed to the program, I started to go over the manual to correct and change items that were not as useful or descriptive as they could have been. I also added in tips that I learned as I explored the software. The updated manual was also worked on by several others who have been developing the program. The goal of these revisions was to ensure the most concise and simple directions to the software were available to future users. By incorporating tricks and shortcuts that I discovered and picked up from watching other users into the user guide, I believe that anyone who utilizes the software will be able to quickly understand the best way to analyze their image and use the tools the program offers to achieve useful results.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Chemical and Electrochemical Characterization of Hot–Pressed Li 6 PS 5 Cl Solid State Electrolyte: Operating Pressure–Invariant High Ionic Conductivity

Sulfide solid state electrolytes (SSE) are among the most promising materials in the effort to replace liquid electrolytes, largely due to their comparable ionic conductivities. Among the sulfide SSEs, Argyrodites (Li 6 PS 5 X, X=Cl, Br, I) further stand out due to their high theoretical ionic conductivity (~1×10 –2 S cm –1 ) and interfacial stability against reactive metal anodes such as lithium. Generally, solid state electrolyte pellets are pressed from powder feedstock at room temperature, however, pellets fabricated by cold pressing consistently result in low bulk density and high porosity, facilitating interfacial degradation reactions and allowing dendrites to propagate through the pores and grain boundaries. Here, we demonstrate the mechanical and electrochemical implications of hot-pressing standalone LPSCl SSE pellets with near-theoretical ionic conductivity, superior cycling performance, and enhanced mechanical stability. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and x-ray diffraction spectroscopy (XRD) analysis reveal no chemical changes to the Argyrodite surface after hot pressing up to 250°C. Furthermore, we use electrochemical impedance spectroscopy (EIS) to understand mechanical stability of Argyrodite SSE pellets as a function of externally applied pressure, demonstrating for the first time pressed standalone Argyrodite pellets with near-theoretical conductivities at external pressures below 14 MPa.

25 ENERGY STORAGE↗
DOE OSTI2023

Utah FORGE: Powder X-ray Diffraction Data from Well 16A(78)-32 Core

This dataset from Lawrence Livermore National Laboratory (LLNL) consists of four raw X-ray diffraction (XRD) scans and preliminary results of quantitative XRD analysis. The scanned samples were prepared from four subcores, which came from various depths of the FORGE well 16A(78)-32 core. Desired core lengths were selected from available core photos (on GDR), provided by FORGE personnel, and subcored at LLNL. The XRD scans were collected in May 2023 at LLNL as pre-experimental characterization data for these subcores, which will be used in core-flooding experiments at LLNL and in triaxial direct shear experiments at Los Alamos National Laboratory as part of DOE Project 5-2428. XRD scans are in RAW file format (e.g., FORGE-5477-full.raw) and are suitable for viewing and analysis using open-source quantitative XRD software (e.g., Profex; www.profex-xrd.org ) and/or other proprietary instrument software.

15 GEOTHERMAL ENERGY↗
DOE OSTI2024

Characterization of compositional variation and solidification condition on rapid solidification behavior of beta stabilized titanium

Rapid solidification (RS) is a field of study that has increased in importance due to the rise of additive manufacturing (AM) techniques. The breakdown of equilibrium at the solid-liquid interface results in an inability to use traditional solidification models that have been applied to great success in casting. As such, there is a current need for a high-throughput testing method to screen alloys at rapid solidification conditions without the significant cost for powder atomization. In this work, twin hammer splat quenching (SQ) is utilized and theoretically developed as a technique uniquely placed to test alloy systems for AM applications. Using analytical thermal spray models and numerical heat transfer simulations, the cooling rate and solidification conditions of splat quenching are compared across several parameters to evaluate the key parameters for generating cooling rates relevant to AM process. Once a framework for the cooling rates and relevancy of SQ are developed, SQ was used to process alloy compositions in the Ti5553 alloy space (AMS 7026) to study the formation of detrimental secondary phases occurring upon rapid quenching from the melt. A martensitic phase is found to occur at the lower end of the standard, but the composition listed in the standard were found to be safe. Finally, the rapid solidification behavior of Ti-5553 is evaluated by comparing splat quenching, laser welding, and plasma atomization that offer a wide window of solidification conditions. The segregation and solidification structure are analyzed and compared to models to provide a deeper understanding of the solidification behavior of beta stabilized titanium alloys.

Williamson, Christopher J.↗
DOE OSTI2019

Investigation of the Effect of Foaming Agent on the Fabrication of NiTi Foams Using the Self-Propagating, High-Temperature Synthesis Process

Fabrication of NiTi intermetallic foams using the self-propagating, high-temperature synthesis (SHS) process was investigated. Weighed amounts of powders taken from an equimolar mixture of Ni and Ti powders along with 0.5, 1, and 1.5 wt pct of different foaming agents were cold pressed to form cylindrical compacts 10 mm in diameter, 20 mm in height, and 7 to 8 g in weight. A novel, induction-assisted ignition method was used for indirect heating and igniting the compressed mixtures at one end. As a result of intensive exothermic reaction between Ni and Ti and decomposition of foaming agents and liberation of gases, highly porous products were obtained. Characterization of the products was carried out using X-ray diffraction (XRD) and a scanning electron microscope equipped with an energy-dispersive spectroscope (SEM-EDS). The main phase in the products was detected to be B2(NiTi) with minor amounts of NiTi{sub 2} as the secondary phase. Other undesirable phases, such as Ni{sub 4}Ti{sub 3} and Ni{sub 3}Ti, were not detected. The effect of type and percentage of foaming agent on the formation and distribution of pores within the products was studied. Final products with porosities up to ~ 80 vol pct were obtained by adding foaming agent. Under the conditions of this study, CaH{sub 2} proved to be the most effective foaming agent considering its ability to generate a uniform distribution of pores, while TiH{sub 2} was not considered favorable due to its decomposition at relatively low temperatures. In general, the addition of foaming agents in amounts higher than 1wt pct is not recommended; due to the endothermic nature of thermal decomposition reactions of foaming agents, excessive use of these agents can result in suppression of the exothermic reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The role of microstructural evolution during spark plasma sintering on the soft magnetic and electronic properties of a CoFe–Al2O3 soft magnetic composite

Abstract For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic polarization and high electrical resistivity are needed. This work aimed at the development of a soft magnetic composite synthesized via spark plasma sintering with both high saturation magnetic polarization and high electrical resistivity for efficient soft magnetic cores. CoFe powder particles coated with an insulating layer of Al 2 O 3 were used as feedstock material to improve the electrical resistivity while retaining high saturation magnetic polarization. By maintaining a continuous non-magnetic Al 2 O 3 phase throughout the material, both a high saturation magnetic polarization, above 1.5 T, and high electrical resistivity, above 100 μΩ·m, were achieved. Through microstructural characterization of samples consolidated at various temperatures, the role of microstructural evolution on the magnetic and electronic properties of the composite was elucidated. Upon consolidation at relatively high temperature, the CoFe was to found plastically deform and flow into the Al 2 O 3 phase at the particle boundaries and this phenomenon was attributed to low resistivity in the composite. In contrast, at lower consolidation temperatures, perforation of the Al 2 O 3 phase was not observed and a high electrical resistivity was achieved, while maintaining a high magnetic polarization, ideal for more efficient soft magnetic materials for transformers and inductors.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Ru-Sn/AC for the Aqueous-Phase Reduction of Succinic Acid to 1,4-Butanediol under Continuous Process Conditions

Succinic acid is a biomass-derived platform chemical that can be catalytically converted in the aqueous phase to 1,4-butanediol (BDO), a prevalent building block used in the polymer and chemical industries. Despite significant interest, limited work has been reported regarding sustained catalyst performance and stability under continuous aqueous-phase process conditions. As such, this work examines Ru-Sn on activated carbon (AC) for the aqueous-phase conversion of succinic acid to BDO under batch and flow reactor conditions. Initially, powder Ru-Sn catalysts were screened to determine the most effective bimetallic ratio and provide a comparison to other monometallic (Pd, Pt, Ru) and bimetallic (Pt-Sn, Pd-Re) catalysts. Batch reactor tests determined that a ~1:1 metal weight ratio of Ru to Sn was effective for producing BDO in high yields, with complete conversion resulting in 82% molar yield. Characterization of the fresh Ru-Sn catalyst suggests that the sequential loading method results in Ru sites that are colocated and surface-enriched with Sn. Postbatch reaction characterization confirmed stable Ru-Sn material properties; however, upon a transition to continuous conditions, significant Ru-Sn/AC deactivation occurred due to stainless steel leaching of Ni that resulted in Ru-Sn metal crystallite restructuring to form discrete Ni-Sn sites. Computational modeling confirmed favorable energetics for Ru-Sn segregation and Ni-Sn formation at submonolayer Sn incorporation. To address stainless steel leaching, reactor walls were treated with an inert silica coating by chemical vapor deposition. With leaching reduced, stable Ru-Sn/AC performance was observed that resulted in a molar yield of 71% BDO and 15% tetrahydrofuran for 96 h of time on stream. Postreaction catalyst characterization confirmed low levels of Ni and Cr deposition, although early-stage islanding of Ni-Sn will likely be problematic for industrially relevant time scales (i.e., thousands of hours). Overall, these results (i) demonstrate the performance of Ru-Sn/AC for aqueous phase succinic acid reduction, (ii) provide insight into the Ru-Sn bimetallic structure and deactivation in the presence of leached Ni, and (iii) underscore the importance of compatible reactor metallurgy and durable catalysts.

09 BIOMASS FUELS↗
DOE OSTI2017

ζ-Glycine: insight into the mechanism of a polymorphic phase transition

Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterized at atmospheric or high pressure. A sixth form, the elusive ζ phase, was discovered over a decade ago as a short-lived intermediate which formed as the high-pressure ϵ phase transformed to the γ form on decompression. However, its structure has remained unsolved. We now report the structure of the ζ phase, which was trapped at 100 K enabling neutron powder diffraction data to be obtained. The structure was solved using the results of a crystal structure prediction procedure based on fully ab initio energy calculations combined with a genetic algorithm for searching phase space. We show that the fate of ζ-glycine depends on its thermal history: although at room temperature it transforms back to the γ phase, warming the sample from 100 K to room temperature yielded β-glycine, the least stable of the known ambient-pressure polymorphs.

36 MATERIALS SCIENCE↗