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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Assessing the potential of ToF-SIMS as a complementary approach to investigate cement-based materials — Applications related to alkali–silica reaction

In this study, the potential of time-of-flight secondary ion mass spectrometry (ToF-SIMS) for the application in cement-based materials is assessed in combination and comparison with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Mortar, concrete and samples from model systems providing products formed by the alkali–silica reaction (ASR) were studied. ToF-SIMS provides qualitative data on alkalis in cases where EDX reaches its limits in regard to detectable concentration, lateral resolution and atomic number of the elements. Due to its high in-depth resolution of a few atomic monolayers, thin layers of reaction products can be detected on the surfaces and chemically analyzed with ToF-SIMS. Additionally, it delivers information on the molecular conformation within the ASR product, its hydrogen content and its isotope ratios, information not provided by EDX. Provided the samples are carefully prepared, ToF-SIMS opens up new possibilities in the analysis of cement-based materials.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Simulated impedance of diffusion in porous media

This paper describes the use of a frequency domain, finite-difference scheme to simulate the impedance spectra of diffusion in porous microstructures. We investigate both open and closed systems for a range of ideal geometries, as well as some randomly generated synthetic volumes and tomographically derived microstructural data. In many cases, the spectra deviate significantly from the conventional Warburg-type elements typically used to represent diffusion in equivalent circuit analysis. Furthermore, a key finding is that certain microstructures show multiple peaks in the complex plane, which may be misinterpreted as separate electrochemical processes in real impedance data. This is relevant to battery electrode design as the techniques for nano-scale fabrication become more widespread. This simulation tool is provided as an open-source MatLab application and is freely available online as part of the TauFactor platform.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Improved statistical models for limited datasets in uncertainty quantification using stochastic collocation

This paper presents a data-driven framework for performing uncertainty quantification (UQ) by choosing a stochastic model that accurately describes the sources of uncertainty in a system. This model is propagated through an appropriate response surface function that approximates the behavior of this system using stochastic collocation. Given a sample of data describing the uncertainty in the inputs, our goal is to estimate a probability density function (PDF) using the kernel moment matching (KMM) method so that this PDF can be used to accurately reproduce statistics like mean and variance of the response surface function. Instead of constraining the PDF to be optimal for a particular response function, we show that we can use the properties of stochastic collocation to make the estimated PDF optimal for a wide variety of response functions. We contrast this method with other traditional procedures that rely on the Maximum Likelihood approach, like kernel density estimation (KDE) and its adaptive modification (AKDE). We argue that this modified KMM method tries to preserve what is known from the given data and is the better approach when the available data is limited in quantity. We test the performance of these methods for both univariate and multivariate density estimation by sampling random datasets from known PDFs and then measuring the accuracy of the estimated PDFs, using the known PDF as a reference. Comparing the output mean and variance estimated with the empirical moments using the raw data sample as well as the actual moments using the known PDF, we show that the KMM method performs better than KDE and AKDE in predicting these moments with greater accuracy. This improvement in accuracy is also demonstrated for the case of UQ in electrostatic and electrothermomechanical microactuators. We show how our framework results in the accurate computation of statistics in micromechanical systems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

High temperature steam oxidation dynamics of U 3 Si 2 with alloying additions: Al, Cr, and Y

Uranium silicides are considered for advanced technology reactor fuels due to their enhanced thermal conductivity and high uranium density (U 3 Si and U 3 Si 2 ) compared to traditional UO 2 . Susceptibility to oxidation and wash out, in the event of a cladding breech, could limit the potential for deployment of silicides as accident tolerant fuels. Mitigating the water reaction for U 3 Si 2 could enable its use as an accident tolerant, high uranium density fuel or as a composite fuel constituent. Reported here is the impact of alloying additions of Al, Cr and Y on the high temperature, steam oxidation response of U 3 Si 2 . In addition to the thermogravimetric response, as melted microstructures, phase compositions and post oxidation analysis are also presented. Here, the investigation shows steam oxidation dynamics are altered, from non-alloyed U 3 Si 2 , under thermally ramped conditions. However, additional alloy development of these fuel forms is necessary for further consideration as candidate accident tolerant fuels in water-cooled reactor designs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Characterization of PyC/SiC interfaces with FIB-SEM tomography

Tristructural-isotropic (TRISO) fuel is being considered for multiple reactor designs due to its exceptional performance. This work studies pyrocarbon (PyC) and silicon carbide (SiC) substrates that are near-representative of the inner pyrocarbon (IPyC) and SiC in TRISO fuel. Focused ion beam (FIB)-scanning electron microscopy (SEM) tomography was used to understand the influence of different processing routes on the PyC/SiC interface structure. Additionally, this work outlines a methodology for characterizing the IPyC/SiC interface when considering fission product accommodation and retention in TRISO fuel design. The high-fidelity images collected with FIB-SEM tomography can be used to achieve a more in-depth interpretation of microstructural parameters and pore-shape analysis that can inform simulations and processing.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Formation of uranium nitride nanoparticles via mechanical alloying of uranium-molybdenum alloy fuels in gaseous nitrogen

Uranium-molybdenum (U-Mo) alloys show promise as a nuclear fuel system due to their high thermal conductivity and fuel loading capability. However, U-Mo systems are susceptible to irradiation induced swelling ultimately affecting the cladding via mechanical and chemical interactions. To address these shortcomings, this research investigated the formation of uranium mononitride (UN) nanoparticles within a 90 wt% U/10 wt% Mo (U-10Mo) matrix to act as a prospective defect sink for fission products at nanometric hetero-interfaces. To promote the formation of UN, U-10Mo powders were mechanically alloyed under a high purity nitrogen atmosphere. Variations of the milling process investigated included media size, duration of milling, and number of times the milling jar was re-aerated with nitrogen gas. Characterization of the fuel microstructure was completed using light element analysis, X-ray diffraction, scanning and transmission-electron microscopy, electron energy loss spectroscopy, and atom probe tomography. UN nanoparticles measuring 1–5 nm in radius were observed in the U-Mo matrix as early as 1 h into the mechanical alloying process. Milling time in excess of 10 h was found to lead to deleterious effects induced by the stainless-steel milling media.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Atomic force microscopy applied to the quantification of nano-precipitates in thermo-mechanically treated microalloyed steels

Quantification of nanometer-size precipitates in microalloyed steels has been traditionally performed using transmission electron microscopy (TEM), in spite of its complicated sample preparation procedures, prone to preparation errors and sample perturbation. In contrast to TEM procedures, atomic force microscopy (AFM) is performed on the as-prepared specimen, with sample preparation requirements similar to those for optical microscopy (OM), rendering three-dimensional representations of the sample surface with vertical resolution of a fraction of a nanometer. In AFM, contrast mechanisms are directly related to surface properties such as topography, adhesion, and stiffness, among others. Chemical etching was performed using 0.5% nital, at time intervals between 4 and 20 s, in 4 s steps, until reaching the desired surface finish. For the present application, an average surface-roughness peak-height below 200 nm was sought. Quantification results of nanometric precipitates were obtained from the statistical analysis of AFM images of the microstructure developed by microalloyed Nb and V-Mo steels. Topography and phase contrast AFM images were used for quantification. The results obtained using AFM are consistent with similar TEM reports. - Highlights: Black-Right-Pointing-Pointer We quantified nanometric precipitates in Nb and V-Mo microalloyed steels using AFM. Black-Right-Pointing-Pointer Microstructures of the thermo-mechanically treated microalloyed steels were used. Black-Right-Pointing-Pointer Topography and phase contrast AFM images were used for quantification. Black-Right-Pointing-Pointer AFM results are comparable with traditionally obtained TEM measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Study on glass-forming ability and hydrogen storage properties of amorphous Mg{sub 60}Ni{sub 30}La{sub 10−x}Co{sub x} (x = 0, 4) alloys

Mg{sub 60}Ni{sub 30}La{sub 10−x}Co{sub x} (x = 0, 4) amorphous alloys were prepared by rapid solidification, using a melt-spinning technique. X-ray diffraction and differential scanning calorimetry analysis were employed to measure their microstructure, thermal stability and glass-forming ability, and hydrogen storage properties were studied by means of PCTPro2000. Based on differential scanning calorimetry results, their glass-forming ability and thermal stability were investigated by Kissinger method, Lasocka curves and atomic cluster model, respectively. The results indicate that glass-forming ability, thermal properties and hydrogen storage properties in the Mg-rich corner of Mg–Ni–La–Co system alloys were enhanced by Co substitution for La. It can be found that the smaller activation energy (ΔΕ) and frequency factor (υ{sub 0}), the bigger value of B (glass transition point in Lasocka curves), and higher glass-forming ability of Mg–Ni–La–Co alloys would be followed. In addition, atomic structure parameter (λ), deduced from atomic cluster model is valuable in the design of Mg–Ni–La–Co system alloys with good glass-forming ability. With an increase of Co content from 0 to 4, the hydrogen desorption capacity within 4000 s rises from 2.25 to 2.85 wt.% at 573 K. - Highlights: • Amorphous Mg{sub 60}Ni{sub 30}La{sub 10−x}Co{sub x} (x = 0 and 4) alloys were produced by melt spinning. • The GFA and hydrogen storage properties were enhanced by Co substitution for La. • With an increase of Co content, the hydrogen desorption capacity rises at 573 K.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Characterization of ultrafine-grained aluminum tubes processed by Tube Cyclic Extrusion–Compression (TCEC)

Tube Cyclic Extrusion–Compression as a novel severe plastic deformation technique for tubes was utilized for processing ultrafine grained 1050 aluminum alloy for the first time. In this method, aluminum tube is fully constrained and deformed between mandrel and chamber with a small neck zone. The material deformation during Tube Cyclic Extrusion–Compression processing analyzed and the grain refinement mechanism were described. The capability of Tube Cyclic Extrusion–Compression in grain refinement of the aluminum alloy was demonstrated by transmission electron microscopy observations and X-ray diffraction line profile analysis. The micrographs of the evolved microstructure show grain size of 850 nm and 550 nm after the first and second processing cycles of Tube Cyclic Extrusion–Compression, respectively. Mechanical properties of the initial and processed specimens were extracted from ring-hoop tensile tests. The documented results confirm grain refinement by showing remarkable increase in the yield and ultimate strengths. The main increase in strength and decrease in elongation take place after the first cycle. The microhardness assessments illustrate increase from the initial value of 29 Hv to 44 and 49 Hv respectively after the first and second cycles of Tube Cyclic Extrusion–Compression. There is a good homogeneity in peripheral microhardness and microhardness across the tube thickness. - Highlights: • Tubes of AA1050 for the first time were successfully SPD processed by TCEC. • The grain size was refined to 550 nm after two cycles of TCEC. • Notable increase in the strength and decrease in the elongation were documented. • The microhardness increased to 49 Hv from the initial value of 29 Hv. • Good homogeneity in the microhardness distribution was recorded.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Characterization of nanosized Al{sub 2}(WO{sub 4}){sub 3}

Graphical abstract: TEM method allows to detect small quantities of impurities not detectable by other methods. In our case impurities of W{sub 5}O{sub 14} are detected in Al{sub 2}(WO{sub 4}){sub 3} nanopowder. Highlights: {yields} Nanosized Al{sub 2}(WO{sub 4}){sub 3} by simple co-precipitation method. {yields} Spherical particles with mean size of 22 nm distributed between 10 and 40 nm at 630 {sup o}C. {yields} XRD, DTA and TEM confirm well defined products with perfect structure. {yields} TEM locality allows detection of impurities not detectable by XRD and DTA. -- Abstract: Nanosized aluminum tungstate Al{sub 2}(WO{sub 4}){sub 3} was prepared by co-precipitation reaction between Na{sub 2}WO{sub 4} and Al(NO{sub 3}){sub 3} aqueous solutions. The powder size and shape, as well as size distribution are estimated after different conditions of powder preparation. The purity of the final product was investigated by XRD and DTA analyses, using the single crystal powder as reference. Between the specimen and the reference no difference was detected. The crystal structure of Al{sub 2}(WO{sub 4}){sub 3} nanosized powder was confirmed by TEM (SAED, HRTEM). In additional, TEM locality allows to detect some W{sub 5}O{sub 14} impurities, which are not visible by conventional X-ray powder diffraction and thermal analyses.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The effects of CeO{sub 2} addition on crystallization behavior and pore size in microporous calcium titanium phosphate glass ceramics

Highlights: ► We prepare a phosphate glass ceramic in the system of CaO–TiO{sub 2}–P{sub 2}O{sub 5} and add 2 to 6 mol% CeO{sub 2} to it. We determine the optimum percentage of CeO{sub 2} addition. ► We study phase separation, suitable time and temperature for crystallization in the microporous Calcium Titanium Phosphate Glass Ceramics utilizing DTA, SEM and XRD. ► We investigate on pore size utilizing BET and SEM techniques before and after CeO{sub 2} addition. ► CeO{sub 2} increases the pore size in the Calcium Titanium Phosphate Glass Ceramics. -- Abstract: In this research the effect of the addition of CeO{sub 2} to microporous Calcium Titanium Phosphate glass ceramics was studied. Different molar percentages of CeO{sub 2} were added to three samples of a base glass whose composition was P{sub 2}O{sub 5} 30, CaO 45, TiO{sub 2} 25 (mol%). The first sample had 2 mol% CeO{sub 2}, the second sample had 4 mol% CeO{sub 2}, and the third sample had 6 mol% CeO{sub 2}. The fourth sample did not contain any CeO{sub 2}. The glass samples were melted and crystallized to bulk glass ceramics by a conventional method. Differential Thermal Analysis (DTA) was utilized to determine the appropriate nucleation and crystallization temperatures. Among the samples, the DTA curve of the sample which had 2 mol% CeO{sub 2} had the sharpest crystallization peak. Therefore, this sample was chosen to prepare the glass ceramics. Using X-ray Diffraction (XRD) it was found that in all samples β-Ca{sub 3}(PO{sub 4}){sub 2} and CaTi{sub 4}(PO{sub 4}){sub 6} were the major phases. The β-Ca{sub 3}(PO{sub 4}){sub 2} phase was dissolved away by soaking the glass ceramics in HCl, leaving a porous skeleton of CaTi{sub 4}(PO{sub 4}){sub 6}. CeO{sub 2} addition increased the glass transition temperature and decreased the crystallization time and temperature. It was shown that CeO{sub 2} addition resulted in an increase in the mean pore diameter while the specific surface area decreased. The median pore diameter and specific surface area were determined as 27 nm and 14 m{sup 2}/g, respectively, for the sample containing 2 mol% CeO{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Investigating the Role of Silver Oxidation State on the Thermodynamic Interactions between Xenon and Silver-Functionalized Zeolites

The molecular level understanding of the strong adsorption of Xe to silver-modified zeolites remains elusive. Here, we probe the effect of silver oxidation state on the thermodynamics of Xe sorption in silver-functionalized zeolites by measuring the enthalpies of adsorption after various treatments using inverse gas chromatography (IGC). The enthalpy of adsorption was measured for silver-functionalized chabazites (AgCHA) before and after hydrogen reduction and subsequent reoxidation. The sorption enthalpy (ΔH) for AgCHA was 35.2 kJ/mol, which decreased to 25.8 kJ/mol with hydrogen reduction. After reoxidation (O 2 -AgCHA), 95% of the binding strength was restored. Hydrogen reduction of the base chabazite (CHA) did not influence Xe adsorption. Henry’s law constant for Xe adsorption increased in the order AgCHA > O 2 -AgCHA > H 2 -AgCHA > CHA. A decrease in enthalpy and Henry’s constant with silver reduction and increase with reoxidation suggest that ionic silver is playing a role in Xe binding. The effect of reduction and reoxidation on the zeolite microstructure was analyzed using surface area analysis, powder X-ray diffraction (p-XRD), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), and X-ray photoelectron spectroscopy (XPS). Finally, these results lay the groundwork for better material design of strong noble gas adsorbents.

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

Design rules for the broad application of fast (<1 s) methylamine vapor based, hybrid perovskite post deposition treatments

While organo-metal halide perovskite photovoltaics have seen rapid development, growth of high quality material remains a challenge. Herein, we report a facile post deposition treatment utilizing coordination between methylamine (CH 3 NH 2 ) vapor and CH 3 NH 3 PbI 3 perovskite that rapidly improves film quality, enhancing power conversion efficiency (PCE) by ~9%. We further comprehensively analyze the physical impact of this process with regard to the material's optoelectronic properties and its detailed microstructural changes. Connecting this with an analysis of the source of organo-metal halide perovskite reactivity toward the vapor as well as phase behavior as a function of CH 3 NH 2 vapor pressure and time, we provide design rules for the broad, rational extension of this process to new systems and scales.

14 SOLAR ENERGY↗
DOE OSTI2014

Nonlinear acoustics experimental characterization of microstructure evolution in Inconel 617

Inconel 617 is a candidate material for the intermediate heat exchanger in a very high temperature reactor for the next generation nuclear power plant. This application will require the material to withstand fatigue-ratcheting interaction at temperatures up to 950°C. Therefore nondestructive evaluation and structural health monitoring are important capabilities. Acoustic nonlinearity (which is quantified in terms of a material parameter, the acoustic nonlinearity parameter, β) has been proven to be sensitive to microstructural changes in material. This research develops a robust experimental procedure to track the evolution of damage precursors in laboratory tested Inconel 617 specimens using ultrasonic bulk waves. The results from the acoustic non-linear tests are compared with stereoscope surface damage results. Therefore, the relationship between acoustic nonlinearity and microstructural evaluation can be clearly demonstrated for the specimens tested.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Meso-scale magnetic signatures for nuclear reactor steel irradiation embrittlement monitoring

Verifying the structural integrity of passive components in light water and advanced reactors will be necessary to ensure safe, long-term operations of the existing U.S. nuclear fleet. This objective can be achieved through nondestructive condition monitoring techniques, which can be integrated with plant operations to quantify the “state of health” of structural materials in real-time. While nondestructive methods for monitoring many classes of degradation (such as fatigue or stress corrosion cracking) are relatively advanced, this is not the case for degradation caused by irradiation. The development of nondestructive evaluation technologies for these types of degradation will require advanced materials characterization techniques and tools that enable comprehensive understanding of nuclear reactor material microstructural and behavioral changes under extreme operating environments. Irradiation-induced degradation of reactor steels causes changes in their microstructure that impacts their micro-magnetic properties. In this paper, we describe preliminary results of integrating advanced material characterization techniques with meso-scale computational models. In the future, this will help to provide an interpretive understanding of the state of degradation in structural materials. Microstructural data are presented from monocrystalline Fe and are correlated with variable-field magnetic force microscopy and micro-magnetic measurements. Ongoing research is focused on extending the measurements and models on thin films to gain insights into the structural state of irradiated materials and the resulting impact on magnetic properties. Preliminary conclusions from these correlations are presented, and next steps described.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Effect of calcination temperature on electrical properties of Nd{sub 0.7}Ba{sub 0.3}MnO{sub 3}

In this work, Nd{sub 0.7}Ba{sub 0.3}MnO{sub 3} was synthesized via cryo-milling method to investigate the effect of calcination temperature on the structure, microstructure, magnetic and electrical properties. XRD analysis revealed all samples can be indexed to orthorhombic structure systems with Imma space group accompany with some minor phases of Mn{sub 2}O{sub 4} and BaMnO{sub 3}. FESEM analysis confirmed that a slight increase in the grain size from 117.4 nm (600°C), 119.5 nm (700°C), 121.0 nm (800°C), 123.1 nm (900°C) to 138.4 nm (1000°C) was observed when different calcination temperature was applied. Four Point Probe measurements showed that all samples are in paramagnetic insulating region and T{sub MIT} is lower than 20K. Resistivity increase when grain size reduces due to increase of effective grain boundary that weakens the electron hopping process via double exchange mechanism. Beside, a drastic increase of resistivity also observed due to present of minor secondary phase (BaMnO{sub 3}) in sample C9.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effect of xenon on the structural phase state of the surface layer of cemented carbide under pulsed electron-beam irradiation

A comparative analysis of the surface-layer microstructure of a tungsten-based cemented carbide modified with pulsed high-energy electron beams generated by gas-discharge plasmas and of the tool life of metal-cutting plates prepared from this alloy is performed. The choice of a plasma-forming gas providing for the emission of electrons out of the plasma-filled cathode is shown to have a profound influence both on the formation process of nano-sized structural-phase states in the surface layer of the cemented carbide and on the tool life of the metal-cutting plates prepared from this alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Final CRADA Report for Small Business Voucher (SBV) Pilot Project with TreadStone Technologies, Inc. – Novel Coating for Fuel Cell Metal Bipolar Plates

Light-weight metal is the preferred material for bipolar plate in the automotive proton exchange membrane (PEM) fuel cell stack. The challenge using metal bipolar plates is the high surface electrical contact resistance and the poor corrosion resistance in PEM fuel cell operation conditions. This SBV project involved specialized capabilities and expertise at Los Alamos National Laboratory (LANL) and Oak Ridge National Laboratory (ORNL) supporting TreadStone Technologies, Inc. and included ex-situ and in-situ drive-cycle tests that incorporated coated metallic bipolar plates (LANL tasks) and analysis of the surface chemistry and microstructure of coatings on stainless steel substrates (ORNL tasks).

30 DIRECT ENERGY CONVERSION↗