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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Revealing the Structural Evolution of Green Rust Synthesized in Ionic Liquids by In Situ Molecular Imaging

Abstract Ionic liquids are green solvents that have wide applications in material synthesis, catalysis, and separation. A model switchable ionic liquid (SWIL) consisting of 1,8‐diazabicycloundec‐7‐ene (DBU) and 1‐hexanol with carbon dioxide (CO 2 ) as the trigger gas is chosen to synthesize nanocrystalline green rust. Under anoxic conditions, by adding iron (II) acetate (Fe(C 2 H 3 O 2 ) 2 ) and methanol to the degassed SWIL, a nanoparticulate green rust with carbonate (nano‐GR) is synthesized. More importantly, the molecular structural change of the ionic liquid resulting in green rust crystallines is first characterized using in situ liquid using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) coupled with the system for analysis at the liquid vacuum interface (SALVI), a vacuum compatible microfluidic reactor in this work. Dimers and ionic clusters consisting ferric and ferrous ions are identified in liquid ToF‐SIMS spectra. Spectral principal component analysis is used to confirm that these ion pairs including dimers and cluster ions are different from nonionic liquids. The results show that liquid ToF‐SIMS can be a useful tool to study complex liquids at the molecular level providing insights into predicative synthesis of nanomaterials using environmentally friendly green solvents and giving unique visualization of the evolving material interface due to nucleation.

Shen, Yanjie↗
DOE OSTI2015

Efficient Cp*Ir Catalysts with Imidazoline Ligands for CO 2 Hydrogenation: Cp*Ir Catalysts with Imidazoline Ligands for CO 2 Hydrogenation

Here, we report newly developed iridium catalysts with electron-donating imidazoline moieties as ligands for the hydrogenation of CO 2 to formate in aqueous solution. Interestingly, these new complexes promote CO 2 hydrogenation much more effectively than their imidazole analogues and exhibit a turnover frequency (TOF) of 1290 h –1 for the bisimidazoline complex compared to that of 20 h –1 for the bisimidazole complex at 1 MPa and 50 °C. Additionally, the hydrogenation proceeds smoothly even under atmospheric pressure at room temperature. The TOF of 43 h –1 for the bisimidazoline complex is comparable to that of a dinuclear complex (70 h –1 , highest TOF reported) [Nat. Chem. 2012, 4, 383], which incorporates proton-responsive ligands with pendent-OH groups in the second coordination sphere. The catalytic activity of the complex with an N-methylated imidazoline moiety is much the same as that of the corresponding pyridylimidazoline analogue. Our result and the UV/Vis titrations of the imidazoline complexes indicate that the high activity is not attributable to the deprotonation of NH on the imidazoline under the reaction conditions.

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

Advances in understanding the surface chemistry of lignocellulosic biomass via time‐of‐flight secondary ion mass spectrometry

Abstract Overcoming the natural recalcitrance of lignocellulosic biomass is necessary in order to efficiently convert biomass into biofuels or biomaterials and many times this requires some type of chemical pretreatment and/or biological treatment. While bulk chemical analysis is the traditional method of determining the impact a treatment has on biomass, the chemistry on the surface of the sample can differ from the bulk chemistry. Specifically, enzymes and microorganisms bind to the surface of the biomass and their efficiency could be greatly impacted by the chemistry of the surface. Therefore, it is important to study and understand the chemistry of the biomass at the surface. Time‐of‐flight secondary ion mass spectrometry (ToF‐ SIMS ) is a powerful tool that can spectrally and spatially analyze the surface chemistry of a sample. This review discusses the advances in understanding lignocellulosic biomass surface chemistry using the ToF‐ SIMS by addressing the instrument parameters, biomass sample preparation, and characteristic lignocellulosic ion fragmentation peaks along with their typical location in the plant cell wall. The use of the ToF‐ SIMS in detecting chemical changes due to chemical pretreatments, microbial treatments, and physical or genetic modifications is discussed along with possible future applications of the instrument in lignocellulosic biomass studies.

09 BIOMASS FUELS↗
DOE OSTI2013

Multi-Instrument Characterization of the Surfaces and Materials in Microfabricated, Carbon Nanotube-Templated Thin Layer Chromatography Plates. An Analogy to ‘The Blind Men and the Elephant’

Herein we apply a suite of surface/materials analytical tools to characterize some of the materials created in the production of microfabricated thin layer chromatography plates. Techniques used include X-ray photoelectron spectroscopy (XPS), valence band spectroscopy, static time-of-flight secondary ion spectrometry (ToF-SIMS) in both positive and negative ion modes, Rutherford backscattering spectroscopy (RBS), and helium ion microscopy (HIM). Materials characterized include: the Si(100) substrate with native oxide: Si/SiO2, alumina (35 nm) deposited as a diffusion barrier on the Si/SiO2: Si/SiO2/Al2O3, iron (6 nm) thermally evaporated on the Al2O3: Si/SiO2/Al2O3/Fe, the iron film annealed in H2 to make Fe catalyst nanoparticles: Si/SiO2/Al2O3/Fe(NP), and carbon nanotubes (CNTs) grown from the Fe nanoparticles: Si/SiO2/Al2O3/Fe(NP)/CNT. The Fe thin films and nanoparticles are found in an oxidized state. Some of the analyses of the CNTs/CNT forests reported appear to be unique: the CNT forest appears to exhibit an interesting ‘channeling’ phenomenon by RBS, we observe an odd-even effect in the ToF-SIMS spectra of Cn- species for n = 1 – 6, with ions at even n showing greater intensity than the neighboring signals, and ions with n ≥ 6 showing a steady decrease in intensity, and valence band characterization of CNTs using X-radiation is reported. The information obtained from the combination of the different analytical tools provides a more complete understanding of our materials than a single technique, which is analogous to the story of ‘The Blind Men and the Elephant’. (Of course there is increasing emphasis on the use of multiple characterization tools in surface and materials analysis.) The raw XPS and ToF-SIMS spectra from this study will be submitted to Surface Science Spectra for archiving.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2014

NanoSIMS Imaging Alternation Layers of a Leached SON68 Glass Via A FIB-made Wedged Crater

Currently, nuclear wastes are commonly immobilized into glasses because of their long-term durability. Exposure to water for long periods of time, however, will eventually corrode the waste form and is the leading potential avenue for radionuclide release into the environment. Because such slow processes cannot be experimentally tested, the prediction of release requires a thorough understanding the mechanisms governing glass corrosion. In addition, due to the exceptional durability of glass, much of the testing must be performed on high-surface-area powders. A technique that can provide accurate compositional profiles with very precise depth resolution for non-flat samples would be a major benefit to the field. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling is an excellent tool that has long been used to examine corrosion layers of glass. The roughness of the buried corrosion layers, however, causes the corresponding SIMS depth profiles to exhibit erroneously wide interfaces. In this study, NanoSIMS was used to image the cross-section of the corrosion layers of a leached SON68 glass sample. A wedged crater was prepared by a focused ion beam (FIB) instrument to obtain a 5× improvement in depth resolution for NanoSIMS measurements. This increase in resolution allowed us to confirm that the breakdown of the silica glass network is further from the pristine glass than a second dissolution front for boron, another glass former. The existence of these two distinct interfaces, separated by only ~20 nm distance in depth, was not apparent by traditional ToF-SIMS depth profiling but has been confirmed also by atom probe tomography. This novel sample geometry will be a major benefit to efficient NanoSIMS sampling of irregular interfaces at the nanometer scale that would otherwise be obscured within ToF-SIMS depth profiles.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

Mass Spectrometry Imaging of Biological Tissue: An Approach for Multicenter Studies

Mass spectrometry imaging has become a popular tool for probing the chemical complexity of biological surfaces. This led to the development of a wide range of instrumentation and preparation protocols. It is thus desirable to evaluate and compare the data output from different methodologies and mass spectrometers. Here, we present an approach for the comparison of mass spectrometry imaging data from different laboratories (often referred to as multicenter studies). This is exemplified by the analysis of mouse brain sections in five laboratories in Europe and the USA. The instrumentation includes matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF), MALDI-QTOF, MALDIFourier transform ion cyclotron resonance (FTICR), atmospheric-pressure (AP)-MALDI-Orbitrap, and cluster TOF-secondary ion mass spectrometry (SIMS). Experimental parameters such as measurement speed, imaging bin width, and mass spectrometric parameters are discussed. All datasets were converted to the standard data format imzML and displayed in a common open-source software with identical parameters for visualization, which facilitates direct comparison of MS images. The imzML conversion also allowed exchange of fully functional MS imaging datasets between the different laboratories. The experiments ranged from overview measurements of the full mouse brain to detailed analysis of smaller features (depending on spatial resolution settings), but common histological features such as the corpus callosum were visible in all measurements. High spatial resolution measurements of AP-MALDI-Orbitrap and TOF-SIMS showed comparable structures in the low-micrometer range. We discuss general considerations for planning and performing multicenter studies in mass spectrometry imaging. This includes details on the selection, distribution, and preparation of tissue samples as well as on data handling. Such multicenter studies in combination with ongoing activities for reporting guidelines, a common data format (imzML) and a public data repository can contribute to more reliability and transparency of MS imaging studies.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry as a Platform for Characterizing Multimeric Membrane Protein Complexes

Membrane protein characterization is consistently hampered by challenges with expression, purification, and solubilization. Among several biophysical techniques employed for their characterization, native-mass spectrometry (MS) has emerged as a powerful tool for the analysis of membrane proteins and complexes. Here, two MS platforms, the FT-ICR and Q-ToF, have been explored to analyze the homotetrameric water channel protein, AquaporinZ (AqpZ), under non-denaturing conditions. This 97 kDa membrane protein complex can be readily liberated from the octylglucoside (OG) detergent micelle under a range of instrument conditions on both MS platforms. Increasing the applied collision energy of the FT-ICR collision cell yielded varying degrees of tetramer (97 kDa) liberation from the OG micelles, as well as dissociation into the trimeric (72 kDa) and monomeric (24 kDa) substituents. Tandem-MS on the Q-ToF yielded higher intensity tetramer signal and, depending on the m/z region selected, the observed monomer signal varied in intensity. Precursor ion selection of an m/z range above the expected protein signal distribution, followed by mild collisional activation, is able to efficiently liberate AqpZ with a high S/N ratio. The tetrameric charge state distribution obtained on both instruments demonstrated superpositioning of multiple proteoforms due to varying degrees of N-terminal formylation. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Electrospray Ionization with High-Resolution Mass Spectrometry as a Tool for Lignomics: Lignin Mass Spectrum Deconvolution

The capability to characterize lignin, lignocellulose, and their degradation products is essential for the development of new renewable feedstocks. Electrospray ionization high-resolution time-of-flight mass spectrometry (ESI-HR TOF-MS) method was developed expanding the lignomics toolkit while targeting the simultaneous detection of low and high molecular weight (MW) lignin species. The effect of a broad range of electrolytes and various ionization conditions on ion formation and ionization effectiveness was studied using a suite of mono-, di-, and triarene lignin model compounds as well as kraft alkali lignin. Contrary to the previous studies, the positive ionization mode was found to be more effective for methoxy-substituted arenes and polyphenols, i.e., species of a broadly varied MW structurally similar to the native lignin. For the first time, we report an effective formation of multiply charged species of lignin with the subsequent mass spectrum deconvolution in the presence of 100 mmol L{sup −1} formic acid in the positive ESI mode. The developed method enabled the detection of lignin species with an MW between 150 and 9000 Da or higher, depending on the mass analyzer. The obtained M{sub n} and M{sub w} values of 1500 and 2500 Da, respectively, were in good agreement with those determined by gel permeation chromatography. Furthermore, the deconvoluted ESI mass spectrum was similar to that obtained with matrix-assisted laser desorption/ionization (MALDI)-HR TOF-MS, yet featuring a higher signal-to-noise ratio. The formation of multiply charged species was confirmed with ion mobility ESI-HR Q-TOF-MS. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

MALDI MS Imaging at Acquisition Rates Exceeding 100 Pixels per Second

The practicality of matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) applied to molecular imaging of biological tissues is limited by the analysis speed. Typically, a relatively low speed of stop-and-go micromotion of XY stages is considered as a factor substantially reducing the rate with which fresh sample material can be supplied to the laser spot. The sample scan rate in our laboratory-built high-throughput imaging TOF mass spectrometer was significantly improved through the use of a galvanometer-based optical scanner performing fast laser spot repositioning on a target plate. The optical system incorporated into the ion source of our MALDI TOF mass spectrometer allowed focusing the laser beam via a modified grid into a 10-μm round spot. This permitted the acquisition of high-resolution MS images with a well-defined pixel size at acquisition rates exceeding 100 pixel/s. The influence of selected parameters on the total MS imaging time is discussed. The new scanning technique was employed to display the distribution of an antitumor agent in 3D colorectal adenocarcinoma cell aggregates; a single MS image comprising 100 × 100 pixels with 10-μm lateral resolution was recorded in approximately 70 s. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Molecular Characterization of High Molecular Weight Polyesters by Matrix-Assisted Laser Desorption/Ionization High-Resolution Time-of-Flight Mass Spectrometry Combined with On-plate Alkaline Degradation and Mass Defect Analysis

Matrix-assisted laser desorption ionization high-resolution time-of-flight mass spectrometry (MALDI HR TOF MS) is a powerful tool for the molecular characterization of industrial polymers. However, accurate mass determination and resolution of isobaric ions are possible for oligomer samples only typically below m/z 3000. To cut long polymer chains into oligomers suitable for high-resolution mass spectrometry, we propose a simple “on-plate” alkaline degradation of polyesters as a sample pretreatment technique prior to the MALDI TOF MS measurement. This pretreatment can be performed on a MALDI target using a small amount of sample (μg or less) and 1 μL of alkaline reagent by simple pipetting. Informative mass spectra in the oligomeric mass range are successfully recorded but complicated by the variation of end-groups and the copolymeric composition of the degradation products. Data processing is assisted by a series of advanced Kendrick mass defect (KMD) analyses recently proposed by the authors to plot visually understandable two-dimensional maps. On-plate degradation pretreatment, high-resolution MALDI TOF MS measurements, and advanced KMD analyses are innovatively combined for the compositional characterization of bacterial poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) and industrial poly(ethylene terephthalate) samples. .

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Low-pressure methanol synthesis from CO 2 over metal-promoted Ni-Ga intermetallic catalysts

Ni-Ga and M-Ni-Ga (M = Au, Co, Cu) catalysts were evaluated for methanol synthesis from CO 2 at 10 bar and 200-270°C. The following trend in turnover frequency (TOF) for CO 2 hydrogenation was observed: AuNiGa > CuNiGa > NiGa > CoNiGa, where TOF increased with decreasing catalyst affinity for CO. The presence of a third metal was found to influence both the formation of the Ni-Ga intermetallic phase as well as the number of available sites for CO chemisorption. Phase formation, catalyst composition and stability were evaluated using therm ogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning transmission electron microscopy and energy dispersive X-ray spectroscopy (STEM-EDX). Au-Ni-Ga, which showed a nearly 4-fold improvement in TOF at 263°C and 10 bar compared to Ni-Ga, consisted of Ni 3 Ga particles decorated with Au, as evidenced by post catalysis characterization.

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

Identification of the mechanism that confers superhydrophobicity on 316L stainless steel

This study develops a rapid method to confer superhydrophobicity on 316L stainless steel surfaces with an amphiphilic reagent such as dodecanoic acid. The highest contact angle (approaching 173°) was obtained after forming hierarchical structures with a non-aqueous electrolyte by an electrolytic process. Our goal was to induce superhydrophobicity directly on 316L stainless steel substrates and to establish which molecules cause the effect. The superhydrophobic behaviour is analysed by contact angle measurements, scanning electron microscopy (SEM), IR spectroscopy and atomic force microscopy (AFM). The growth mechanism is analysed using FE-SEM, TOF-SIMS and XPS in order to determine the molecules involved in the reaction and the growth. The TOF-SIMS analysis revealed that the Ni{sup 2+} ions react with lauric acid to create an ester on the stainless steel surface. - Highlights: • This study develops a rapid and facile approach to impart superhydrophobicity properties to 316L stainless steel surfaces with an amphiphilic reagent such as dodecanoic acid. Surface character changes from superhydrophilicity to superhydrophobicity. • This process changes the surface character from superhydrophilicity to superhydrophobicity. • The process based on electrolysis of a nickel salt in lauric acid provides superhydrophobic behaviour in 316L stainless steel. • The growth mechanism is proposed as a mode island (Volmert- Weber mode). • TOF-SIMS and XPS provided the identification of the molecules involved in the surface modification reaction on AISI 316L inducing superhydrophobicity.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Impurity gas monitoring using ultrasonic sensing and neural networks: forward and inverse problems

Ultrasonic sensing is a non-invasive technique for monitoring impurity gas composition in various industrial applications where safety and regulatory compliance are crucial. In this study, ultrasonic sensing and neural networks were used to analyze impurity gases (i.e., air and argon) in helium. An experimental platform was established to acquire ultrasonic data. In the forward problem, an artificial neural network (ANN) model was used to forecast the response and time-of-flight (TOF) based on the excitation, and argon and air concentrations. The inverse problem was solved using a convolutional neural network (CNN) to predict the argon and air concentrations given the ultrasonic response and excitation. The results showed that the ANN accurately predicted the ultrasonic response and the change in TOF with concentration. As the air concentration was increased from 0 to 9.8%, the TOF sensitivity to detect argon decreased by 39.8% and 16.1% from ANN and sound speed theory, respectively. The CNN demonstrated high accuracy in predicting concentrations for inputs in the testing dataset. The application of the trained CNN indicated that it over-predicts air concentration while under-predicting the argon concentration. To improve accuracy, the predicted air and argon concentrations should be corrected by -0.992% and 1.027% bias, respectively.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Recent developments in deuterated scintillators for neutron measurements at low-energy accelerators

Deuterated ( 2 H-based) organic scintillators, unlike conventional 1 H-based scintillators can generate pulse-shape gated neutron energy spectra 1 to 30 MeV without need for time-of-flight (ToF). They are especially appropriate for measurements at high-intensity, low-energy accelerators where a pulsed beam is not available. Even when the latter is available, the loss in effective beam intensity combined with the need for suitable long-path ToF measurements can be very inefficient. In contrast, as we demonstrate, arrays of d- benzene scintillators (NE230, BC537, EJ315) and recently xylene-d10 (EJ301D) together with related digital signal processing (DSP) can provide highly efficient neutron energy measurements w/o n-ToF. Lastly, we also report the recent synthesis and initial testing of crystalline d-stilbene as a neutron detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Proton discrimination in CLYC for fast neutron spectroscopy

The Cs 2 LiYCl 6 :Ce (CLYC) elpasolite scintillator is known for its response to fast and thermal neutrons along with good γ-ray energy resolution. While the 35 Cl(n,p) reaction has been identified as a potential means for CLYC-based fast neutron spectroscopy in the absence of time-of-flight (TOF), previous efforts to functionalize CLYC as a fast neutron spectrometer have been thwarted by the inability to isolate proton interactions from 6 Li(n,α) and 35 Cl(n,α) signals. This work introduces a new approach to particle discrimination in CLYC for fission spectrum neutrons using a multi-gate charge integration algorithm that provides excellent separation between protons and heavier charged particles. Neutron TOF data were collected using a 252 Cf source, an array of EJ-309 organic liquid scintillators, and a 6 Li-enriched CLYC scintillator outfitted with fast electronics. Modal waveforms were constructed corresponding to the different reaction channels, revealing significant differences in the pulse characteristics of protons and heavier charged particles at ultrafast, fast, and intermediate time scales. These findings informed the design of a pulse shape discrimination algorithm, which was validated using the TOF data. This study also proposes an iterative subtraction method to mitigate contributions from confounding reaction channels in proton and heavier charged particle pulse height spectra, opening the door for CLYC-based fast neutron and γ-ray spectroscopy while preserving sensitivity to thermal neutron capture signals.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Machine learning based rate optimization under geologic uncertainty

We propose a novel approach for rate optimization during a waterflood under geologic uncertainty in reservoir properties such as permeability and porosity. The traditional approach typically involves several runs of the forward simulator. This may not scale well when the optimization is to be performed at the full field-level and over multiple geologic realizations. A machine-learning (ML) based approach which is quick and scalable for rate optimization over multiple geologic realizations is proposed instead. The training data for the model is generated by running the forward simulator with randomly assigned well rates using multiple geologic realizations. A reduced order representation of the permeability heterogeneity in each of the realizations is derived using a grid connectivity transformation (GCT). This step involves finding basis functions corresponding to the different modal frequencies of the grid connectivity represented by the grid Laplacian. The projection of the heterogeneous property field along these basis functions gives the basis coefficients that form the reduced order representation. Subsequently, for each training datapoint, streamlines are traced and the minimum time of flight (TOF) representing the tracer breakthrough time at each producer is recorded. The basis coefficients and well rates are fed to a machine learning model as input and the minimum TOF at the producers forms the output of the model. This trained model can then be used along with an optimizer for computing the optimal injection rates to maximize the injection sweep efficiency. This corresponds to minimizing the variance in the minimum TOF within each well group. Different architectures of neural network are tested using 5-fold cross validation to decide the best ML model to compute the streamline time of flight. The trained model is used to perform well rate optimization over multiple realizations of geology by using a risk tolerance penalty. The optimal well rates thus obtained are compared with two cases: a) equal well rates assigned to all injectors and producers and b) well rates obtained by optimizing over a single realization without considering the uncertainty in geology. The optimal well rates are seen to offer better oil recovery and sweep efficiency than both cases.

02 PETROLEUM↗