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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Petrologic Sub-types, Sub-groups, and Pairing for CV Chondrites in the US Antarctic Meteorite Collection

Carbonaceous chondrites of the Vigarano group (CV) are primitive meteorites that provide a wealth of information about the early solar system, including constraints on chondrule formation, origin of calcium-aluminum inclusions, stability of organic compounds, and redox conditions. The US Antarctic meteorite collection contains 119 CV samples from 15 dense collection areas (DCAs) from the Trans-Antarctic Mountains. These samples have been assigned a preliminary classification as CVs, but have not been assigned to the subgroups Oxidized A, Oxidized B, and Reduced. Additionally, variation in petrologic grade can be determined non-destructively using Raman spectroscopy. In order to update classification of both subgroups and petrologic types in the collection, we have acquired magnetic susceptibility, metal and sulfide compositions, and Raman spectra, for as many samples as possible. We use the recent assessment and delineation of CV sub-groups of as a guide.

solar nebula↗
NASA NTRS2002

WOBBLE: A Proposed Mission to Characterize Past and Present Water on Mars

WOBBLE ("Water Observations from a Balloon Borne Light Explorer") is a mission concept study for a small robotic probe to explore Mars and to accomplish a scientific mission compatible with the goals of the NASA Code S enterprise. The detection of past or present water is a crucial goal for Mars exploration, representing a cross-cutting science theme relevant to past or extant life, climate history, sample return missions and eventual human exploration. The WOBBLE mission concept was developed to study evidence of water using in-situ detection methods. The features on Mars most suited to this investigation are the gullies identified by Malin and Edgett as evidence for recent, near-surface runoff of liquid water. These features are typically located on the inside face of crater rims, where the local slope angle is at or near the angle of repose. This makes the terrain difficult or impossible to access with conventional wheeled rover technology. Combined with the small size of the gullies in relation to a standard landing error ellipse, scientific investigation of these features requires a new approach to surface mobility. WOBBLE uses a low-altitude balloon-borne platform to traverse the surface from the landing site, to the investigation site, and then rise up the slope to investigate the regions of interest at close range. Of the mobility technologies available for near-term Mars exploration, only a balloon platform is capable of a well targeted, detailed sampling of the gully regions over periods of days or more. The science approach embodied in WOBBLE is two-pronged, designed to investigate both the historical evidence of liquid water utilizing high-resolution geomorphology and the characterization of mineral deposits, and present subsurface liquid water using radar sounding techniques. The WOBBLE balloon is a high-pressure hydrogen gas design, 24 meters in diameter and lifting a total payload of 130 kg, including a high-resolution camera/IR imager, Raman spectrometer, and a ground penetrating radar (GPR) sounder. The stowed balloon and payload are designed to fit within the current airbag delivery system being built for the Mars Exploration Rovers. Characterization of local meteorological conditions and wind is made over the initial sols following landing and before balloon inflation. Following balloon inflation and launch, a controlled, targeted approach toward the identified regions of interest is made in a series of several low-altitude "hops," with the balloon tethered to the ground between the hop intervals. A "snake" system is used to control the altitude to a few tens of meters above the local ground level. Enroute to the target gully, GPR soundings and Raman spectroscopy measurements study past or present water, while continued camera bearings and meteorological measurements refine the next "hop" trajectory. Once at the gully/outflow region, GPR and Raman soundings continue while the camera obtains detailed, approx. 0.5 cm images for geomorphology studies. The WOBBLE concept is applicable to Mars Scout, Mars Surveyor, or Discovery class missions.

Udrea, Bogdan↗
DOE OSTI2021

Radiolysis of thermally dehydrated gibbsite

Aluminum hydroxide (gibbsite, Al (OH) 3 ) powders and their thermally dehydrated forms were rehydrated and irradiated with gamma rays to examine the effects of the collapse of the crystalline gibbsite structure as it is converted to alumina on the transport of precursors of molecular hydrogen to the surface. The amount of hydrogen gas, H 2 , production from irradiated gibbsite and its transition phases with adsorbed water increased substantially with increasing temperature for dehydration of the samples, up to a point. Furthermore, the production of H 2 for samples without water was considerably lower than the hydrated samples signifying the importance of surface water and the transport of precursors to the surface. EPR spectroscopy showed that the major radiolytic products are trapped electrons and related O – centers. Thermal gravimetric analysis (TGA) measurements of gibbsite dehydration established the temperatures of phase transitions from gibbsite to alumina. Changes to the surface and structure of gibbsite and its transition phases following irradiation were analyzed using nitrogen adsorption, powder X-ray diffraction (pXRD), Raman spectroscopy, electron paramagnetic resonance (EPR), and scanning electron microscopy (SEM). pXRD and Raman spectra showed amorphorization at about 300 °C, coupled to a substantial increase in specific surface area due to increasing porosity.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2026

Prospects for detecting UF6 hydrolysis intermediates by mass spectrometry, resonance Raman, and NQR spectroscopy

Simulations are performed to consider several spectrometric and spectroscopic candidates for elucidating the mechanism of the hydrolysis of uranium hexafluoride (UF6). This study is among the first to benchmark the def-mTZVP basis sets for actinide-containing molecules, and it is shown to be a suitable basis set for surveying geometrical structures and vibrational spectra when used in conjunction with density functional theory. An experiment is proposed coupling mass spectrometric ion selection with vibrational spectroscopy, and supporting infrared and Raman spectral simulations demonstrate that ionization blue-shifts bands and can change their qualitative features. Ultraviolet resonance Raman is shown to have good prospects for discriminating U–O–U bridged intermediates, evidence for which was observed recently [L. E. McNamara et al., J. Phys. Chem. A 130, 775–786 (2026)]. As a more speculative approach, we also consider the prospect of addressing 233U or 235U nuclei by quadrupole resonance (NQR) spectroscopy for assigning early stage intermediate complexes. In doing so, we provide a first order-of-magnitude estimate for the collision-induced NQR signal for the UF6 dimer, which is of interest for the interpretation of a fast decoherence time observed in liquid-phase nuclear magnetic resonance. Having provided critical insights into the formation and stability of UF6 hydrolysis intermediates in previous studies, this computational spectroscopy survey is expected to help guide and expedite future laboratory campaigns.

Lutz, Jesse J. [Center for Computing Research, San↗
DOE OSTI2020

Mechanistic Studies of the Oxidation of Cyclohexene to 2-Cyclohexen-1-one over ALD Prepared Titania Supported Vanadia

Selective oxidation of cyclohexene to 2-cyclohexen-1-one over titania supported vanadia (VO x /TiO 2 ) has been studied using temperature dependent in-situ FTIR spectroscopy in both the presence and absence of oxygen. The VO x /TiO 2 samples were prepared using one atomic layer deposition (ALD) cycle and characterized by Raman spectroscopy. In-situ FTIR data for the oxidation of cyclohexene and perdeuterocyclohexene allow for the formulation of a molecular level reaction mechanism, which is initiated by the transfer of an allyl hydrogen. Oxidation of perdeuterocyclohexene provides a direct probe of the formation of OD and HDO moieties that support the involvement of specific steps in the proposed mechanism. The presence of gas phase oxygen does not lead to a change in the products versus anaerobic conditions. However, gas phase oxygen is significantly incorporated in the CO 2 over-oxidation product above ~250 °C. Data were also obtained with cyclohexene epoxide as the reactant in an effort to determine whether there is a parallel reaction pathway, which is initiated by C=C activation in cyclohexene, that involves cyclohexene epoxide as an intermediate. Furthermore, though a minor pathway involving a cyclohexene epoxide intermediate cannot be ruled out, these data demonstrate that, under experimental conditions, the dominant pathway from cyclohexene to cyclohexene-1-one is initiated by an allyl-H activation step and does not involve an epoxide intermediate.

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

High Throughput Data-Driven Design of Laser-Crystallized 2D MoS 2 Chemical Sensors: A Demonstration for NO 2 Detection

High throughput characterization and processing techniques are becoming increasingly necessary to navigate multivariable, data-driven design challenges for sensors and electronic devices. For two-dimensional materials, device performance is highly dependent upon a vast array of material properties including the number of layers, lattice strain, carrier concentration, defect density, and grain structure. In this work, laser crystallization was used to locally pattern and transform hundreds of regions of amorphous MoS 2 thin films into 2D 2H-MoS 2 . Here a high throughput Raman spectroscopy approach was subsequently used to assess the process-dependent structural and compositional variations for each illuminated region, yielding over 6000 distinct nonresonant, resonant, and polarized Raman spectra. The rapid generation of a comprehensive library of structural and compositional data elucidated important trends between structure–property processing relationships involving laser-crystallized MoS 2 , including the relationships between grain size, grain orientation, and intrinsic strain. Moreover, extensive analysis of structure/property relationships allowed for intelligent design and evaluation of major contributions to device performance in MoS 2 chemical sensors. In particular, it is found that NO 2 sensor performance is strongly dependent on the orientation of the MoS 2 grains relative to the crystal plane.

36 MATERIALS SCIENCE↗
NASA NTRS2000

Raman Spectrometer for Surface Identification of Minerals and Organic Compounds on Silicate Planets and Small Solar-System Bodies

This summary is the final report of work on two-year grant. Our objectives for this project were (1) to demonstrate that Raman spectroscopy is an excellent method for determining mineralogy on the surface of the Moon, Mars, and other planetary bodies; (2) to construct a prototype of a small Raman spectrometer of the kind we suggest could be used on a lander or rover; and (3) to test the ability of that spectrometer to identify minerals and quantify mineral proportions in lunar materials and complex Martian analog materials, and to identify organic matter in planetary surface materials, all under roughly simulated field conditions. These goals have been met. The principal accomplishments of this PIDDP project have been the following: selection for flight; construction of a breadboard Raman probe; throughput confirmation of the breadboard Raman probe; selection of a laser; a breadboard spectrograph based on our PIDDP design; and overall result.

Haskin, Larry A.↗
NASA NTRS2008

Single Wall Nanotube Type-Specific Functionalization and Separation

Metallic single-wall carbon nanotubes were selectively solubilized in THF and separated from semiconducting nanotubes. Once separated, the functionalized metallic tubes were de-functionalized to restore their metallic band structure. Absorption and Raman spectroscopy of the enriched samples support conclusions of the enrichment of nanotube samples by metallic type. A scalable method for enriching nanotube conductive type has been developed. Raman and UV-Vis data indicate SWCNT reaction with dodecylbenzenediazonium results in metallic enrichment. It is expected that further refinement of this techniques will lead to more dramatic separations of types and diameters.

Boul, Peter↗
DOE OSTI2024

Enhanced Carbon‐Carbon Coupling at Interfaces with Abrupt Coordination Number Changes

Abstract Cu‐catalyzed electrochemical CO 2 reduction reaction (CO 2 RR) produces multi‐carbon (C 2+ ) chemicals with considerable selectivities and activities, yet required high overpotentials impede its practical application. Here, we design interfaces with abrupt coordination number (CN) changes that greatly reduce the applied potential for achieving high C 2+ Faradaic efficiency (FE). Encouraged by the mechanistic finding that the coupling between *CO and *CO(H) is the most probable C−C bond formation path, we use Cu 2 O‐ and Cu‐phthalocyanine‐derived Cu (OD−Cu and PD−Cu) to build the interface. Using operando X‐ray absorption spectroscopy (XAS), we find that the Cu CN of OD−Cu is ~11, favoring CO* adsorption, while the PD−Cu has a COH*‐favorable CN of ~4. Operando Raman spectroscopy revealed that the interfaces with abrupt CN changes promote *OCCOH formation. As a result, the designed catalyst achieves a C 2+ FE of 85±2 % at 220 mA cm −2 in a zero‐gap CO 2 electrolyzer. An improvement of C 2+ FE by 3 times is confirmed at the low potential regime where the current density is 60–140 mA cm −2 , compared to bare OD−Cu. We report a 45‐h stable CO 2 RR operation at 220 mA cm −2 , producing a C 2+ product FE of ~80 %.

Chemistry↗
DOE OSTI2024

An Adsorptive Membrane Platform for Precision Ion Separation: Membrane Design and First‐Principles Studies

One of the key challenges in separation science is the lack of precise ion separation methods and mechanistic understanding crucial for efficiently recovering critical materials from complex aqueous matrices. Herein, first-principles electronic structure calculations and in situ Raman spectroscopy are studied to elucidate the factors governing ion discrimination in an adsorptive membrane specifically designed for transition metal ion separation. Density functional theory calculations and in situ Raman data jointly reveal the thermodynamically favorable binding preferences and detailed adsorption mechanisms for competing ions. How membrane binding preferences correlate with the electronic properties of ligands is explored, such as orbital hybridization and electron localization. The findings underscore the importance of the phenolate group in oxime ligands for achieving high selectivity among competing transition metal ions. In-depth understanding on which specific atomistic site within the microenvironment of metal-ligand binding pockets governs the ion discrimination behaviors of the host will build a solid foundation to guide the rational design of next-generation materials for precision separation essential for energy technologies and environment remediation. In tandem, synthetic controllability is demonstrated to transform 3D micrometer-scale crystals to a 2D crystalline selective layer in membranes, paving the way for more precise and sustainable advances in separation science.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

How Does Bending the Uranyl Unit Influence Its Spectroscopy and Luminescence?

We report bent uranyl complexes can be formed with chloride ligands and 1,10-phenanthroline (phen) ligands bound to the equatorial and axial planes of the uranyl(VI) moiety, as revealed by the crystal structures, IR and Raman spectroscopy, and quantum-chemical calculations. With the goal of probing the influence of chloride and phenanthroline coordination enforcing the bending on the absorption and emission spectra of this complex, spin–orbit time-dependent density functional theory calculations for the bare uranyl complexes as well as for the free UO 2 Cl 2 subunit and the UO 2 Cl 2 (phen) 2 complex were performed. The emission spectra have been fully simulated by ab initio methods and compared to experimental photoluminescence spectra, recorded for the first time for UO 2 Cl 2 (phen) 2 . Notably, the bending of uranyl in UO2Cl2 and UO 2 Cl 2 (phen) 2 triggers excitations of the uranyl bending mode, yielding a denser luminescence spectrum.

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

Radiation-induced alteration of apatite on the surface of Mars: first in situ observations with SuperCam Raman onboard Perseverance

Abstract Planetary exploration relies considerably on mineral characterization to advance our understanding of the solar system, the planets and their evolution. Thus, we must understand past and present processes that can alter materials exposed on the surface, affecting space mission data. Here, we analyze the first dataset monitoring the evolution of a known mineral target in situ on the Martian surface, brought there as a SuperCam calibration target onboard the Perseverance rover. We used Raman spectroscopy to monitor the crystalline state of a synthetic apatite sample over the first 950 Martian days (sols) of the Mars2020 mission. We note significant variations in the Raman spectra acquired on this target, specifically a decrease in the relative contribution of the Raman signal to the total signal. These observations are consistent with the results of a UV-irradiation test performed in the laboratory under conditions mimicking ambient Martian conditions. We conclude that the observed evolution reflects an alteration of the material, specifically the creation of electronic defects, due to its exposure to the Martian environment and, in particular, UV irradiation. This ongoing process of alteration of the Martian surface needs to be taken into account for mineralogical space mission data analysis.

Science & Technology - Other Topics↗
DOE OSTI2024

Iodine speciation in basaltic melts at depth

The speciation of iodine in basalts has been investigated by combining in situ X-ray diffraction at high pressures and temperatures up to 4.9 GPa and 1600 °C, and Raman spectroscopy on recovered high pressure glasses at ambient conditions. Both methods point to iodine being oxidized in basalts, whether molten or quenched as glasses. Observed interatomic distances and Raman vibrational modes are consistent with iodine being dissolved as complex iodate groups alike polyiodates or periodates, not as IO$^-_3$ groups. Iodine speciation in basalts therefore seems to reflect a trend amongst halogens, with lighter chlorine bonding to network modifying cations, and bromine changing affinity from network modifying cations to oxygen anions under pressure. In the absence of a fluid aqueous phase, iodine could thus reach the Earth’s surface in basaltic magmas as an oxide, not as a reduced species.

58 GEOSCIENCES↗
NASA NTRS1992

Ion produced cometary organic crust

For several years many experimental results have been obtained on the chemical and physical changes induced by ion and electron irradiation of materials with a view to their Astrophysical relevance. Among the studied effects, one of particular interest is the formation of an organic refractory residue left over after ion irradiation and warming-up at room temperature. We call this residue IPHAC (ion produced hydrogenated amorphous carbon). Although 'in situ' infrared spectroscopy points out the formation of new molecular species during bombardment at low temperature, it is not clear if IPHAC is already formed or if its formation is triggered by temperature increase during warming-up of the irradiated target. Since Raman Spectroscopy is a technique particularly suitable for the analysis of carbonaceous materials, we have thought and build-up an experimental apparatus to obtain Raman Spectra of frozen hydrocarbons during ion irradiation. The present experimental results point out clearly to the formation of IPHAC already at low T and low energy deposition (approximately equal to a few eV/C-atom).

Baratta, G. Antonio↗
DOE OSTI2023

In-situ Synthesis of PuCl 3 and Corresponding Raman and Density Functional Theory Vibrational Modes

The experimental and calculated Raman spectrum of PuCl 3 has been reported for the first time. PuCl 3 is a primary species found in plutonium metal refinement, specifically in pyrochemical salt processes including multicycle direct oxide reduction, metal chlorination, and electrorefining. As such, Raman signatures of PuCl 3 could serve as potential forensic indicators of material process history. A novel technique for synthesizing PuCl 3 from the in situ chlorination of plutonium metal with HCl was developed to establish these signatures. Cerium metal surrogates were utilized to ensure optimization of the plutonium experiments and to minimize personnel exposure, and all experiments were carried out in a Raman reaction chamber designed for air-tight, high vacuum environments. In situ Raman spectroscopy was employed in conjunction with density functional theory (DFT) to investigate the vibrational modes of PuCl 3 . Associated mixed oxy and hydroxyl phases are also reported. The combined Raman and DFT results have eliminated inconsistencies in Raman mode assignments for the MX 3 family of metal chlorides having P6 3 /m symmetry, and IR modes derived from the DFT calculations are additionally presented. The data observed in this study are of potential interest to nuclear forensic analyses, nuclear sample aging, nuclear energy, plutonium processing, and stockpile stewardship.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In-situ Synthesis of PuCl 3 and Corresponding Raman and Density Functional Theory Vibrational Modes

The experimental and calculated Raman spectrum of PuCl 3 has been reported for the first time. PuCl 3 is a primary species found in plutonium metal refinement, specifically in pyrochemical salt processes including multicycle direct oxide reduction, metal chlorination, and electrorefining. As such, Raman signatures of PuCl 3 could serve as potential forensic indicators of material process history. A novel technique for synthesizing PuCl 3 from the in-situ chlorination of plutonium metal with HCl was developed to establish these signatures. Cerium metal surrogates were utilized to ensure optimization of the plutonium experiments and to minimize personnel exposure, and all experiments were carried out in a Raman reaction chamber designed for air-tight, high vacuum environments. In-situ Raman spectroscopy was employed in conjunction with Density Functional Theory (DFT) to investigate the vibrational modes of PuCl 3 . Associated mixed oxy and hydroxyl phases are also reported. The combined Raman and DFT results have eliminated inconsistencies in Raman mode assignments for the MX 3 family of metal chlorides having P6 3 /m symmetry, and IR modes derived from the DFT calculations are additionally presented. The data observed in this study is of potential interest to nuclear forensic analyses, nuclear sample aging, nuclear energy, plutonium processing, and stockpile stewardship.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Non-intrusive measurements in a rocket engine combustor

In recent years analytical tools to characterize combustor flow have been developed in order to support design. To facilitate anchoring of combustion related physical models and the CFD codes in which they are incorporated, considerable development and application of non-intrusive combustion diagnostic capabilities has occurred. Raman spectroscopy can be used to simultaneously detect all polyatomic molecules present in significant concentrations and to determine gas temperature. This is because all molecules possess a distinct temperature dependent Raman spectrum. A multi-point diagnostic system for non-intrusive temperature and species profiling in rocket engines has been developed at Rocketdyne. In the present effort, the system has been undergoing validation for application to rocket engine component testing. A 4 inch diameter windowed combustor with a coaxial gas-gas injector was chosen for this series of validation experiments. Initially an excimer-pumped tunable dye laser and later a solid state Nd-Yag laser served as excitation sources. The Raman signal was dispersed by a monochromator and detected by a gated, intensified Charged Coupled Device (CCD) array. Experiments were carried out prior to each series of hot fire tests to ensure that the Raman signal detected was due to a spontaneous rather than a stimulated Raman emission process. Over sixty hot fire tests were conducted during the first series of tests with the excimer/dye laser. All hot fire testing was at a mixture ratio of 0.5 and chamber pressures of approximately 100 and approximately 300 psia. The Raman spectra of hydrogen, water vapor and oxygen recorded during single element hot fire tests were reduced and analyzed. A significant achievement was the attainment of single shot Raman spectra in cold flow tests. Unfortunately, the single shot signal-to-noise ratio deteriorated to an unacceptable level during the hot fire testing. Attempts to obtain temperature data from the hydrogen Q1-branch profiles obtained in hot fire tests suggest that potentially complicating factors may render the approach of averaging data on the photodiode array invalid. A second series of hot fire tests was conducted with a 4 element coaxial injector using the Nd-Yag laser. A very compact and portable diagnostics set up was assembled for ease of alignment, relocation and flexibility. Measurements were made at several regions in the chamber in order to map concentration profiles. High spatial resolution and improved signal to noise characteristics were demonstrated.

Farhangi, S.↗
DOE OSTI2020

Hard, transparent, sp3-containing 2D phase formed from few-layer graphene under compression

Despite several theoretically proposed two-dimensional (2D) diamond structures, experimental efforts to obtain such structures are in initial stage. Recent high-pressure experiments provided significant advancements in the field, however, expected properties of a 2D-like diamond such as sp 3 content, transparency and hardness, have not been observed together in a compressed graphene system. Here, we compress few-layer graphene samples on SiO 2 /Si substrate in water and provide experimental evidence for the formation of a quenchable hard, transparent, sp 3 -containing 2D phase. Our Raman spectroscopy data indicates phase transition and a surprisingly similar critical pressure for two-, five-layer graphene and graphite in the 4e6 GPa range, as evidenced by changes in several Raman features, combined with a lack of evidence of significant pressure gradients or local non-hydrostatic stress components of the pressure medium up to ≈ 8 GPa. The new phase is transparent and hard, as evidenced from indentation marks on the SiO 2 substrate, a material considerably harder than graphene systems. Furthermore, we report the lowest critical pressure (≈ 4 GPa) in graphite, which we attribute to the role of water in facilitating the phase transition. Overall, theoretical calculations and experimental data indicate a novel, surface to- bulk phase transition mechanism that gives hint of diamondene formation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗