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Results for “Application characterization”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Long-life LiNi 0.5 Mn 1.5 O 4 /graphite lithium-ion cells with an artificial graphite-electrolyte interface

The high operating voltage of a spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode leads to electrolyte decomposition and accelerated deterioration of the electrode/electrolyte interface in lithium-ion cells. Aggressive side reactions prevent long-term cycling and hinder its practical application. Advanced characterization shows that the high-voltage operation makes the graphite anode react with the electrolyte, particularly with the lithium salt in the electrolyte, resulting in massive active lithium inventory loss and capacity fade. The side reactions at the graphite are identified as the main culprit for the LNMO/graphite full cell decay. Here, we demonstrate that an artificial solid-electrolyte interface layer consisting of an ultra-thin Al 2 O 3 film, generated via atomic layer deposition (ALD) at the graphite surface, can successfully isolate the graphite from the electrolyte and inhibit the undesired reactions. Consequently, the capacity and cycling stability of the LNMO/graphite cell are drastically improved. After 300 cycles, the capacity retention of LNMO/graphite cell increases from 57.7% to 98.6% with the ALD-coated graphite. Furthermore, our findings provide valuable insights into the LNMO/graphite cell degradation and suggest a simple and robust, yet highly effective, approach for the practical viability of high-voltage lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Experimental investigation of Multi-Mode heat transfer to a Free-Falling dilute particle cloud in a heated vertical tube

The development of dilute particle heat exchangers and reactors for advanced energy systems requires an understanding of the multi-mode heat transfer from a heated wall to falling particles. This study presents experimental results of the overall heat transfer coefficient for a free-falling, dilute flow of particles with solid volume fraction from 0.0005 to 0.006 corresponding to feed rates from 3.7 kg s -1 m -2 to 44 kg s -1 m -2 in a vertical, heated tube containing quiescent air at atmospheric pressure. Tube wall temperatures are varied between 300°C to 900°C while keeping the particle inlet temperature constant. The experimental results show that the overall heat transfer coefficient is a strong function of particle feed rate and surface temperature. Good agreement was obtained with prior studies conducted at comparable temperatures but lower particle feed rates (< 4 kg m -2 s -1 ). The established correlations for particle-to-wall radiation and particle-to-gas convection were used to estimate the wall-to-gas convective contribution from the measured overall heat transfer coefficient. The experimental results indicated a 4 to 6 times improvement in the wall convection in the solid-gas mixture compared to that expected from natural convection in a single-phase gas. Furthermore, the data presented here are applicable to characterize heat transfer in dilute particle heat exchangers, furnaces, and solar receivers.

14 SOLAR ENERGY↗
DOE OSTI2018

A novel application of terrestrial LIDAR to characterize elevation change at human grave surfaces in support of narrowing down possible unmarked grave locations

Unmarked graves are difficult to locate once the ground surface no longer shows visible evidence of disturbance, posing significant challenges to missing person investigations. This research evaluates the use of terrestrial LIDAR point data for measuring localized elevation change at human grave surfaces. Three differently sized human graves, one control-pit, and surrounding undisturbed ground, were scanned four times between February 2013 and November 2014 using a tripod-mounted terrestrial laser scanner. All the disturbed surfaces exhibited measurable and localized elevation change, allowing for separation of disturbed and undisturbed ground. In conclusion, this study is the first to quantify elevation changes to human graves over time and demonstrates that terrestrial LIDAR may contribute to multi-modal data collection approach to improve unmarked grave detection.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Electrochemical detection of chlorate on a novel nano-Au/TiO{sub 2}NT electrode

Highlights: • Highly stable gold nanoparticles were synthesized by a simple photochemical process. • TiO{sub 2} nanotubes were used as substrate for preparation of a novel 3D modified electrode. • This electrode was capable of chlorate ion reduction and detection. - Abstract: The present work describes the synthesis, characterization and application of Au nanoparticles modified titanium nanotube electrode (Nano-Au/TiO{sub 2}NT) as a novel and sensitive electrode material for electrochemical sensing of chlorate. For this purpose, highly ordered TiO{sub 2} nanotube (TiO{sub 2}NT) electrode was synthesized by anodization of metallic titanium foil in ethylene glycol-water solution. Nano-Au/TiO{sub 2}NT was obtained by drop casting a solution of homogeneous and fine structures of gold nanoparticles, which were prepared from HAuCl{sub 4} using a new simple photochemical process. Structural and elemental analysis characteristics of the resulting Nano-Au/TiO{sub 2}NT electrode were investigated by scanning electron microscopy and X-ray diffraction analysis. The electrocchemical activity of resulted Nano-Au/TiO{sub 2}NT electrode towards chlorate reduction in acidic solution was confirmed by cyclic voltammetry and chronoamperometry methods An enhancement of amperometric current in the presence of chlorate was afforded to chlorate detection with a low detection limit of 12 μM and linear range of 50 μM to 4.8 mM.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A new magnesium sheet alloy and its multi-stage homogenization for simultaneously improved ductility and strength at room temperature

We report that a new Mg-2Zn-0.3Ca-0.2Ce-0.1Mn (ZXEM2000) alloy and a multi-stage homogenization process have been designed and developed based on CALculation of Phase Diagram (CALPHAD) modeling results and experimental validation. The new sheet alloy offers an excellent combination of ductility (about 29% elongation) and yield strength (157 MPa), promising room-temperature forming applications. Microstructure characterization reveals that the exceptional properties of this alloy are mainly attributed to the weak basal texture, fine average grain size and high density of nano-scale Mn and Mg 6 Zn 3 Ca 2 precipitates achieved through multi-stage heat treatment and thermomechanical processing.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Resistivity distribution and donor properties of antimony-doped n -type Czochralski silicon ingots

We investigate antimony (Sb)-doped Czochralski-grown silicon as an alternative n-type substrate for photovoltaic applications, and characterize their axial resistivity distribution, donor properties, and mechanical strength. We find that Sb-doped ingots can achieve a more uniform resistivity distribution along the axial direction compared to P-doped counterparts. Dopant concentration profiles in P-doped ingots can be accurately modelled using the standard Scheil's equation, accounting only for dopant segregation during solidification. In contrast, modelling Sb-doped ingots requires consideration of both dopant segregation and evaporation effects to fit the dopant distribution accurately. Using electron paramagnetic resonance spectroscopy at 9 K, we observe two hyperfine lines in P-doped samples, and six hyperfine lines for Sb 121 and eight for Sb 123 isotopes, with the number of hyperfine lines governed by the nuclear spins. We further identify two-atom Sb clustering in the Sb-doped wafers, confirmed through simulations of the additional weak electron paramagnetic resonance peaks. Finally, we find that 140 μm as-cut planar Sb-doped wafers exhibit slightly higher mechanical strength compared to P-doped wafers.

14 SOLAR ENERGY↗
DOE OSTI2018

Small scale to extreme: Methods for characterizing energy efficiency in supercomputing applications

Here, power measurement capabilities are becoming commonplace on large scale HPC system deployments. There exist several different approaches to providing power measurements that are used today, primarily in-band and out-of-band measurements. Both of these fundamental techniques can be augmented with application-level profiling and the combination of different techniques is also possible. However, it can be difficult to assess the type and detail of measurement needed to obtain insights and knowledge of the power profile of an application. In addition, the heterogeneity of modern hybrid supercomputing platforms requires that different CPU architectures must be examined as well.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

High throughput crystal structure and composition mapping of crystalline nanoprecipitates in alloys by transmission Kikuchi diffraction and analytical electron microscopy

Statistically significant crystal structure and composition identification of nanocrystalline features such as nanoparticles/nanoprecipitates in materials chemistry and alloy designing using electron microscopy remains a grand challenge. In this paper, we reveal that differing crystallographic phases of nanoprecipitates in alloys can be mapped with unprecedented statistics using transmission Kikuchi diffraction (TKD), on typical carbon-based electron-transparent samples. Using a case of multiphase, multicomponent nanoprecipitates extracted from an improved version of 9% chromium Eurofer-97 reduced-activation ferritic-martensitic steel we show that TKD successfully identified more than thousand M 23 C 6 , MX, M 7 C 3 , and M 2 X ( M =Fe, Cr, W, V, Ta; X = C, N) nanoprecipitates in a single scan, something that is currently unachievable using a transmission electron microscope (TEM) without incorporating a precision electron diffraction (PED) system. Precipitates as small as ~20–25 nm were successfully phase identified by TKD. We verified the TKD phase identification using high-resolution transmission electron microscopy (HRTEM) and convergent beam electron diffraction (CBED) pattern analysis of a few precipitates that were identified by TKD on same sample. TKD study was combined with state-of-art analytical scanning transmission electron microscopy (STEM)-energy dispersive X-ray (EDX) spectroscopy and multivariate statistical analysis (MVSA) which provided the complete crystal structure and distinct chemistries of the precipitates in the steel in a high throughput automated way. This technique should be applicable to characterizing any multiphase crystalline nanoparticles or nanomaterials. Furthermore the results highlight that combining phase identification by TKD with analytical STEM and modern data analytics may open new pathways in big data material characterization at nanoscale that may be highly beneficial for characterizing existing materials and in designing new materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enabling Microscale Processing: Combined Raman and Absorbance Spectroscopy for Microfluidic On-Line Monitoring

Microfluidics have many potential applications including characterization of chemical processes on a reduced scale, spanning the study of reaction kinetics using on-chip liquid–liquid extractions, sample pretreatment to simplify off-chip analysis, and for portable spectroscopic analyses. The use of in situ characterization of process streams from laboratory-scale and microscale experiments on the same chemical system can provide comprehensive understanding and in-depth analysis of any similarities or differences between process conditions at different scales. A well-characterized extraction of Nd(NO 3 ) 3 from an aqueous phase of varying NO 3– (aq) concentration with tributyl phosphate (TBP) in dodecane was the focus of this microscale study and was compared to an earlier laboratory-scale study utilizing counter current extraction equipment. Here, we verify that this same extraction process can be followed on the microscale using spectroscopic methods adapted for microfluidic measurement. Concentration of Nd (based on UV–vis) and nitrate (based on Raman) was chemometrically measured during the flow experiment, and resulting data were used to determine the distribution ratio for Nd. Extraction distributions measured on the microscale were compared favorably with those determined on the laboratory scale in the earlier study. Both micro-Raman and micro-UV–vis spectroscopy can be used to determine fundamental parameters with significantly reduced sample size as compared to traditional laboratory-scale approaches. This leads naturally to time, cost, and waste reductions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Node Distortions in UiO-66 Inform Negative Thermal Expansion Mechanisms: Kinetic Effects, Frustration, and Lattice Hysteresis

In metal–organic frameworks (MOFs) the interplay between the dynamics of individual components and how these are constrained by the extended lattice can yield unusual emergent phenomena. For the archetypal Zr-MOF, UiO-66, we explore the cooperative dynamics of a Zr-node transformation that gives rise to negative thermal expansion (NTE). Here, using in situ synchrotron X-ray scattering, with powder diffraction and pair distribution function (PDF) analyses, we identify lattice hysteresis and a thermal ramp-rate-dependence of the thermal expansion. Specifically, kinetic trapping of distorted node states formed at high temperature, leads to broad variability in the apparent thermal expansion which ranges from large positive to large negative thermal expansion with coefficients of thermal expansion (CTE) from +45 to –80 × 10 –6 K –1 . Time-resolved relaxation studies at selected temperatures suggest that when equilibrated UiO-66 is intrinsically NTE, with a CTE of –35 × 10 –6 K –1 . Kinetic trapping of the node-distorted state following high temperature activation has broad implications for characterization and applications of these Zr-MOFs; the nonequilibrium node state depends on the thermal history of the sample with quench vs slow cooling likely to impact gas binding, pore volume, and accessible catalytic sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

p-Type BiVO 4 for Solar O 2 Reduction to H 2 O 2

Photoelectrochemical cells (PECs) can directly utilize solar energy to drive chemical reactions to produce fuels and chemicals. Oxide-based photoelectrodes in general exhibit enhanced stability against photocorrosion, which is a critical advantage for building a sustainable PEC. However, most oxide-based semiconductors are n-type, and p-type oxides that can be used as photocathodes are limited. In this study, we report the synthesis, characterization, and application of p-type BiVO 4 with a monoclinic scheelite (ms) structure. ms-BiVO 4 is inherently n-type, and it has been investigated only as a photoanode to date. In this study, we prepared p-type ms-BiVO 4 (bandgap of 2.4 eV) via atomic doping of Ca 2+ at the Bi 3+ site under an O 2 -rich environment and examined its performance as a photocathode. We then demonstrated that the Ca-doped ms-BiVO 4 photocathode can be used for solar O 2 reduction to H 2 O 2 when coupled with appropriate catalysts. Our computational investigation using hybrid density functional theory revealed that holes are stable as polarons in ms-BiVO 4 and have a low self-trapping energy, that may lead to free carriers in the valence band at finite temperature. Our calculations also show that Ca is an effective shallow acceptor dopant with low formation energy and thermal ionization energy leading to p-type conductivity. In conclusion, our joint experimental and computational results provide critical insights into the design of p-type ms-BiVO 4 , enabling its use as a polaronic oxide photocathode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Using an Explainable Machine Learning Approach to Characterize Earth System Model Errors: Application of SHAP Analysis to Modeling Lightning Flash Occurrence

Abstract Computational models of the Earth System are critical tools for modern scientific inquiry. Efforts toward evaluating and improving errors in representations of physical and chemical processes in these large computational systems are commonly stymied by highly nonlinear and complex error behavior. Recent work has shown that these errors can be effectively predicted using modern Artificial Intelligence (A.I.) techniques. In this work, we go beyond these previous studies to apply an explainable A.I. technique to not only predict model errors but also move toward understanding the underlying reasons for successful error prediction. We use XGBoost classification trees and SHapley Additive exPlanations analysis to explore the errors in the prediction of lightning occurrence in the NASA Goddard Earth Observing System model, a widely used Earth System Model. This explainable error prediction system can effectively predict the model error and indicates that the errors are strongly related to convective processes and the characteristics of the land surface.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Synthesis, optical imaging, and absorption spectroscopy data for 179072 metal oxides

Abstract Optical absorption spectroscopy is an important materials characterization for applications such as solar energy generation. This data descriptor describes the to date (Dec 2018) largest publicly available curated materials science dataset for near infrared to near UV (UV-Vis) light absorbance, composition and processing properties of metal oxides. By supplying the complete synthesis and processing history of each of the 179072 samples from 99965 unique compositions we believe the dataset will enable the community to develop predictive models for materials, such as prediction of optical properties based on composition and processing, and ultimately serve as a benchmark dataset for continued integration of machine learning in materials science. The dataset is also a resource for identifying materials composition and synthesis to attain specific optical properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Nanometer Scale Imaging to Develop Quantitative Descriptors of Bipolar Membrane Junction Structure

Swings in pH can be achieved by electrically polarizing a bipolar membrane (BPM) to drive water dissociation at the BPM junction for electrochemical conversion and separation processes. BPM junction design is critical to tailor performance for specific applications; however, characterization techniques capable of resolving the nanometer scale physical structure of the junction are limited. We present sample preparation, imaging, and analysis workflows that are adaptable to a variety of BPM junction architectures. Atomic force microscopy produces BPM junction images with nanometer scale lateral resolution for samples with and without a graphene oxide water dissociation catalyst in the junction. Subsequent image segmentation and analysis quantify line edge roughness and catalyst layer thickness as descriptors of junction structure. Comparison of pre- and post-electrodialysis junctions suggests electric field-induced alignment of catalyst particles during electrodialysis. This characterization workflow can inform manufacturing protocols, computational modeling, and failure mode analysis for next-generation BPMs.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Direct intercalation of MoS 2 and WS 2 thin films by vacuum filtration

In the development of next-generation electronics and energy devices, intercalation compounds of transition metal dichalcogenides (TMDCs) are gaining attention for their unique properties that result from synergistic interactions between guest species and host materials. Nowadays, intercalation compounds of MoS 2 and WS 2 are commonly prepared by a two-step process: (1) exfoliation to form single-layer and/or few-layer nanosheets and (2) restacking the nanosheets with the guest species by vigorously mixing the exfoliated suspension with the solution of guest species. While a wide variety of intercalation compounds have been synthesized using this approach, the intercalation process is often timeconsuming, and the product slurry limits material quality and impedes characterization and applications. Herein, we report a versatile method for preparing intercalated TMDCs in a thin-film morphology. Using this approach, we successfully prepared a range of existing intercalation compounds of MoS 2 and WS 2 (e.g., ferrocene and amine intercalated MoS 2 and WS 2 ). Additionally, by leveraging the versatility of this intercalation method, we report we intercalated phenazine and benzoquinone into MoS 2 and WS 2 for the first time.

36 MATERIALS SCIENCE↗