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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

In Situ Infrared Spectroscopy of a Plasma Jet and Data-Driven Solution of Multi-Scale Plasma Chemistry Problems

Multi-scale problems are commonly known in many scientific and engineering fields where microscopic behaviors are coupled with macroscopic processes. This is also an unsolved problem in low-temperature plasma chemistry where hundreds of chemical species are involved in thousands of chemical reactions. To address this problem, a physics-informed data-driven modeling is developed to solve such a multi-scale problem using the experimental Fourier-transform infrared spectroscopy (FTIR) measurements of several species’ concentrations. The modeling based on modern machine learning techniques provides concentrations of other relevant species along with the electron temperature and gas temperature at the location of FTIR measurements. For example, the concentrations O, OH, and H 2 O 2 play key roles in plasma-based cancer therapy. This approach overcomes the multi-scale difficulties of microscopic low-temperature plasma chemistry coupling with macroscopic gas flow and allows the acquisition of a full picture of output species concentrations. Presented here for the helium-air jet at atmospheric pressure, the ML-based modeling can be used to describe and possibly control multiscale systems using partial experimental data sets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Hydrogen Transport from Dielectrics to poly-Si/SiOx Passivating Contacts Measured by Mass Spectrometry and Vibrational Spectroscopy

We demonstrate the relationship between Si solar cell passivation and hydrogen content of various passivating films, including hydrogenated amorphous silicon (a-Si:H), aluminum oxide (Al2O3), silicon nitride (SiNx) and combinations thereof. Through isotopic studies using quadrupole mass spectrometry (QMS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, we determine how hydrogen content and stability within each type of film relates to final passivation quality of solar cell test structures. Si solar cells using polycrystalline silicon on silicon oxide (poly-Si/SiOx) passivating contacts are at the forefront of Si solar cell research and emerging as top performers within industrial production. Performance of passivating contact Si solar cells is largely determined by a parameter known as the open-circuit voltage Voc, which directly relates to material quality within the bulk of the device and at surfaces. High Voc is achieved when defects within the bulk crystalline silicon (c-Si) and at interfaces are passivated, preventing them from acting as charge carrier recombination centers. One of the most important means of passivating defects within Si solar cells is via hydrogenation, injecting the cells with large amounts of H to satisfy dangling bonds in the bulk and at interfaces. Hydrogen is especially important in deactivating a prevalent defect in industrial p-type devices which leads to decreased device performance over long-term exposure to light, called light-induced degradation (LID). Some of the most common materials used to supply H to devices are a-Si:H, Al2O3, and SiNx, which can contain very large amounts of H. Upon annealing at elevated temperatures, the hydrogen becomes mobile enough to find and disable defect sites. However, too much hydrogen can also be problematic, sometimes leading to an effect called light and elevated temperature induced degradation (LeTID). It has been shown that these films passivate the interfaces of poly-Si passivating contacts differently, leading to differing performance. Though Al2O3 is a well-defined dielectric material, SiNx can have many different values of x depending on precursor gases and deposition conditions. We observe different FTIR and Raman spectra from different SiNx over a range of x values films to determine the bonding environments within them and further correlate the relative concentrations of Si, N, and H to the stability of H within SiNx and the passivation performance of each film. Because deuterium is chemically identical to hydrogen within these systems, but gives different signals in FTIR and Raman spectroscopy as well as in QMS, isotopic substitution can be used as an excellent tool to probe the H within films. In addition to measuring the H and D bonding within films using FTIR and Raman spectroscopy, we will use such isotopic experiments to observe H and D movement out of these hydrogenating films at elevated temperatures using QMS to determine the stability of H bonding within such systems. With these films characterized based on elemental composition, we will relate such measurements to passivation quality of these films and combinations thereof on poly-Si/SiOx contact structures using quasi-steady state photoconductance decay measurements to obtain implied open-circuit voltage (iVoc) and saturation current density J0 values. Such investigations into the performance of different passivating films and film stacks will lead to greater understanding of dielectrics in semiconductor devices, further improvements in passivated contact design, and eventually, greater proliferation of renewable solar energy worldwide.

Al2O3↗
DOE OSTI2021

Mechanism and dynamics of fatty acid photodecarboxylase

Photoenzymes are rare biocatalysts driven by absorption of a photon at each catalytic cycle; they inspire development of artificial photoenzymes with valuable activities. Fatty acid photodecarboxylase (FAP) is a natural photoenzyme that has potential applications in the bio-based production of hydrocarbons, yet its mechanism is far from fully understood. RATIONALE To elucidate the mechanism of FAP, we studied the wild-type (WT) enzyme from Chlorella variabilis (CvFAP) and variants with altered active-site residues using a wealth of techniques, including static and time-resolved crystallography and spectroscopy, as well as biochemical and computational approaches. RESULTS A 1.8-Å-resolution CvFAP x-ray crystal structure revealed a dense hydrogen-bonding network positioning the fatty acid carboxyl group in the vicinity of the flavin adenine dinucleotide (FAD) cofactor. Structures solved from free electron laser and low-dose synchrotron x-ray crystal data further highlighted an unusual bent shape of the oxidized flavin chromophore, and showed that the bending angle (14°) did not change upon photon absorption (step 1) or throughout the photocycle. Calculations showed that bending substantially affected the energy levels of the flavin. Structural and spectroscopic analysis of WT and mutant proteins targeting two conserved active-site residues, R451 and C432, demonstrated that both residues were crucial for proper positioning of the substrate and water molecules and for oxidation of the fatty acid carboxylate by 1 FAD* (~300 ps in WT FAP) to form FAD ∙– (step 2). Time-resolved infrared spectroscopy demonstrated that decarboxylation occured quasi-instantaneously upon this forward electron transfer, consistent with barrierless bond cleavage predicted by quantum chemistry calculations and with snapshots obtained by time-resolved crystallography. Transient absorption spectroscopy in H 2 O and D 2 O buffers indicated that back electron transfer from FAD ∙– was coupled to and limited by transfer of an exchangeable proton or hydrogen atom (step 3). Unexpectedly, concomitant with FAD ∙– reoxidation (to a red-shifted form FAD RS ) in 100 ns, most of the CO 2 product was converted, most likely into bicarbonate (as inferred from FTIR spectra of the cryotrapped FAD RS intermediate). Calculations indicated that this catalytic transformation involved an active-site water molecule. Cryo-Fourier transform infrared spectroscopy studies suggested that bicarbonate formation (step 4) was preceded by deprotonation of an arginine residue (step 3). At room temperature, the remaining CO 2 left the protein in 1.5 μs (step 4'). The observation of residual electron density close to C432 in electron density maps derived from time-resolved and cryocrystallography data suggests that this residue may play a role in stabilizing CO 2 and/or bicarbonate. Three routes for alkane formation were identified by quantum chemistry calculations; the one shown in the figure is favored by the ensemble of experimental data. CONCLUSION Finally, we provide a detailed and comprehensive characterization of light-driven hydrocarbon formation by FAP, which uses a remarkably complex mechanism including unique catalytic steps. We anticipate that our results will help to expand the green chemistry toolkit.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Aged and unaged pine wood pyrogenic organic matter: mineralization, elemental analysis and spectroscopy data (February 2020)

In this study, we used a pyrogenic organic matter (PyOM) degrading Streptomyces isolate – a globally common soil bacterium – to investigate the effects of physical (freeze-thaw and wet-dry), chemical (oxidation), and biological (microbial community incubation) ageing on the chemical properties and mineralizability of 350°C and 550°C pine wood PyOM. We used Fourier Transform Infrared spectroscopy (FTIR) and elemental analysis to characterize the aged and unaged PyOM, and cavity ring-down spectroscopy to trace CO2 emissions. The carbon (C) mineralization data from incubation of aged and unaged PyOM with the isolate are provided in co2cmg_picarro_022020.csv. This dataset contains raw carbon dioxide (CO2) data measured on the cavity ring-down spectroscopy over 1 month of incubation. The dataset also includes processed data such as cumulative CO2 emitted over multiple cycles of measurement and CO2 values normalized by the total carbon content in each PyOM treatment. The carbon, hydrogen and nitrogen elemental content of aged and unaged 350°C and 550°C pine wood PyOM are provided in CHN_pyom.csv. The relative peak heights measured during the FTIR analysis of aged and unaged PyOM are provided in ftir_peaks_rel.csv.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Geophysical Impacts and Spectroscopic Identification of a Hydrous Iron Sulfate on Icy Worlds

Over geologic time-scales, large volumes of exogenic sulfur ions from Io's plasma torus have been supplied to the surface of Europa and Ganymede, which, combined with recent interpretations of orbiter images, dynamical modeling, and surface-subsurface exchange, suggests further sulfur transport into the interior of the icy worlds. These observations motivate mixed-phase spectral modeling for interpreting orbiter spectroscopy data and determination of hydration states of candidate surface materials including hydrous sulfates. In this work, we present a combined experimental and theoretical study of the low temperature and high pressure vibrational spectral signature of the iron-sulfate monohydrate endmember, szomolnokite (FeSO 4 ·H 2 O). By employing synchrotron Fourier-transform infrared spectroscopy (FTIR) in the diamond anvil cell up to 23 GPa and down to 20 K, we explore the extreme range of pressure-temperature domains relevant to icy environments throughout our solar system and beyond. Combined with our density-functional theory quantum-mechanics molecular dynamics results, we demonstrate that experimentally observed infrared features in the O-H stretching region commonly associated with nH 2 O (n > 1) hydration states can be attributed to a pure monohydrate without the need for pressure-induced exsolved ice, other coexisting hydrous iron sulfates, or strong overtone and combination modes. We further discuss the possibility of lateral variations in density and shear properties on icy worlds associated with temperature variations and the high-pressure phases of kieserite group monohydrated sulfates.

Geosciences↗
DOE OSTI2021

Use of kaolinite clays in development of a low carbon MgO-clay binder system

Magnesium oxide based cements may provide a promising alternative to the conventional Portland cement in many applications. This study investigates the feasibility of using calcined kaolinitic clay to produce an MgO binder. The MgO-based binder were prepared using a low kaolinite content clay and metakaolin and were compared with a silica fume system. Implications of the addition of magnesium carbonate in the binder were also investigated. Isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to study the hydration characteristics of the binder system whereas compressive strength and porosity were measured to determine mechanical and durability attributes. The economic and environmental aspects of the binder system is also discussed. Hydrotalcite like phases were clearly produced on hydration in the clay mixes containing carbonate additions. The compressive strength of clay mixes was at par or better compared to systems containing silica fume, and the clay systems had significantly lower porosity levels. The presence of magnesium carbonate further enhanced the physical properties of the clay mixes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Ultrabroadband THz conductivity of gated graphene in- and out-of-equilibrium

We employ ultrabroadband terahertz (THz) spectroscopy to expose the high-frequency transport properties of Dirac fermions in monolayer graphene. By controlling the carrier concentration via tunable electrical gating, both equilibrium and transient optical conductivities are obtained for a range of Fermi levels. The frequency-dependent equilibrium response is determined through a combination of time-domain THz and Fourier-transform infrared spectroscopy for energies up to the near-infrared, which also provides a measure of the gate-voltage dependent Fermi level. Transient changes in the real and imaginary parts of the graphene conductivity are electro-optically resolved for frequencies up to 15 THz after near-infrared femtosecond excitation, both at the charge-neutral point and for higher electrostatic-doping levels. Modeling of the THz response provides insight into changes of the carrier spectral weights and scattering rates, and reveals an additional broad-frequency ($$\approx$$ 8 THz) component to the photo-induced response, which we attribute to the zero-momentum mode of quantum-critical transport observed here in large-area CVD graphene.

Coslovich, G↗
DOE OSTI2020

Flash Graphene from Plastic Waste

In this work, an approach to upcycling plastic waste (PW) products is presented. The method relies on flash Joule heating (FJH) to convert PW into flash graphene (FG). In addition to FG, the process results in the formation of carbon oligomers, hydrogen, and light hydrocarbons. In order to make high quality graphene, a sequential alternating current (AC) and direct current (DC) flash is used. Here, the FJH process requires no catalyst and works for PW mixtures, which makes the process suitable for handling landfill PW. The energy required to convert PW to FG is ~ 23 kJ/g or ~ $125 in electricity per ton of PW, potentially making this process economically attractive for scale-up. The FG was characterized by Raman spectroscopy and had a I 2D /I G peak ratio up to 6 with a low-intensity D band. Moreover, transmission electron microscopy and X-ray diffraction analysis show that the FG is turbostratic with an interlayer spacing of 3.45 Å. The large interlayer spacing will facilitate its dispersion in liquids and composites. Analysis of FG dispersions in 1% Pluronic aqueous solution shows that concentrations up to 1.2 mg/mL can be achieved. The carbon oligomers that distilled from the process were characterized by Fourier-transform infrared spectroscopy and have chemical structures similar to the starting PW. Initial analysis of gas phase products shows the formation of considerable amounts of hydrogen along with other light hydrocarbons. Since graphene is naturally occurring and it shows a low toxicity profile, this could be an environmentally beneficial method to upcycle PE.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Vapor-phase grafting of functional silanes on atomic layer deposited Al 2 O 3

Fundamental studies are needed to advance our understanding of selective adsorption in aqueous environments and develop more effective sorbents and filters for water treatment. Vapor-phase grafting of functional silanes is an effective method to prepare well-defined surfaces to study selective adsorption. In this investigation, we perform vapor phase grafting of five different silane compounds on aluminum oxide (Al2O3) surfaces prepared by atomic layer deposition. These silane compounds have the general formula L3Si–C3H6–X where the ligand, L, controls the reactivity with the hydroxylated Al2O3 surface and the functional moiety, X, dictates the surface properties of the grafted layer. We study the grafting process using in situ Fourier transform infrared spectroscopy and ex situ x-ray photoelectron spectroscopy measurements, and we characterize the surfaces using scanning electron microscopy, atomic force microscopy, and water contact angle measurements. Here, we found that the structure and density of grafted aminosilanes are influenced by their chemical reactivity and steric constraints around the silicon atom as well as by the nature of the anchoring functional groups. Methyl substituted aminosilanes yielded more hydrophobic surfaces with a higher surface density at higher grafting temperatures. Thiol and nitrile terminated silanes were also studied and compared to the aminosilane terminated surfaces. Uniform monolayer coatings were observed for ethoxy-based silanes, but chlorosilanes exhibited nonuniform coatings as verified by atomic force microscopy measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Heat accelerates degradation of β -lactoglobulin fibrils at neutral pH

Fibrous aggregates of β-lactoglobulin display superior mechanical and interfacial properties compared to the native protein. These properties directly link to the protein morphology and structure. When incorporated into food matrices, during processing protein fibrils are exposed to pH shifts and high temperature conditions, which accelerate their degradation. In the present study, neutralized β-lactoglobulin fibrils were heated at 100 °C and 121 °C for various times to assess their degradation. Fibril morphology, structure, and viscosity in solution were examined by microscopy, scattering, spectroscopy, and rheology. Atomic force microscopy showed the contour length of the protein fibrils decreased gradually with heating at 100 °C and 121 °C, with greater decreases at 121 °C. Increased fibril diameters (~15–25 nm) were observed at 121 °C for 5–15 min heating and were disrupted upon further heating. Small-angle x-ray scattering indicated an increase in fibril radius with heating at pH 7 followed by a decrease at prolonged heating, whereas fibril length decreased continuously with heating. Thioflavin T fluorescence, circular dichroism and Fourier transform infrared spectroscopy confirmed the conversion of β-sheet to random coils as fibrils were degraded during thermal treatment at pH 7. Surface hydrophobicity of fibrils decreased with increase in heating temperature and time, coinciding with an increase in the content of non-aggregated proteins. Viscosity of fibril solutions increased when fibrils were heated at 100 °C, whereas at 121 °C their viscosity first increased and then decreased. Furthermore, these findings imply heating at 100 °C and 121 °C facilitates degradation and depolymerisation of β-lactoglobulin fibrils with aggregation as an intermediate step.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Analysis of Material Properties of Aged Rigid Polyurethane Foam

Foams are classified as either rigid or flexible and are commonly used in applications such as pipe insulation, carpet fibers, and chair foam cushions. Polyurethane foams are excellent thermal insulators, have excellent mechanical properties, and are chemically inert. With the addition of fire protective additives, polyurethane foams have the ability to intumescence when exposed to high temperatures. For the future storage of the 9977 nuclear shipping packages, the material properties of the General Plastics 3716 rigid polyurethane foam were evaluated for long term performance by comparing aged samples to unaged samples. General Plastics 3716 rigid polyurethane foam was aged from November 2014 to June 2019 at varying temperatures of: 160 deg. F, 160 deg. F + 50% relative humidity (RH), 185 deg. F, 215 deg. F, and 250 deg. F. The foam was then analyzed via Fourier Transform Infrared Spectroscopy (FTIR), 3D Optical Microscope, Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC). FTIR and Optical Microscope: No significant change to chemical or physical structure was evident by FTIR or optical microscope analysis. DSC: Decrease of heat capacity over time for all oven temperatures except a slight increase for the 185 deg. F conditioned foams. Largest decrease evident with foams conditioned at 250 deg. F. A slight increase in heat capacity for humid samples. Similar trends in heat capacities at 71 deg. C and 102 deg. C. TGA: As conditioning temperature increased, a decline was evident in the average percent weight loss, onset temperature, and first derivative peak temperature. No significant effect due to humidity except for a decrease in first derivative peak temperature. Unaged samples exhibited strong intumescence. Foams conditioned at 160 deg. F exhibited slight intumescence. Results suggest fire protective additives decomposed at higher temperatures, which contributed to a lower average percent mass loss in higher temperature conditioning. Further thermal degradation testing would be beneficial to evaluate the ability of the conditioned foams to intumesce. Evaluate irradiation dose rate effects on conditioned foam. Possible conditioning in an environment with a known humidity or analyzing a new aliquot of sample for each trial to achieve a more representative heat capacity calculation.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2009

Synthesis of Submillimeter Radiation for Spectroscopy

The frequency-multiplier submillimeter spectrometer (FMSS) is a laboratory apparatus for far-infrared molecular spectroscopy, embodying several advances over prior such apparatuses. The most innovative part of the FMSS is a source of monochromatic submillimeter- wavelength radiation that can be tuned over a wide frequency range, as needed for trace gas analyses and molecular- structure studies for which such apparatuses are typically used. The radiation source features a modular design and is built mostly from commercially available components. It includes a computer-controlled radio-frequency synthesizer, amplifiers, and frequency multipliers of a type heretofore used in local oscillators for heterodyne far-infrared receivers. In conjunction with the rest of the apparatus, this source makes it possible to perform measurements over large portions of the submillimeter-wavelength spectrum with resolution, accuracy, and sensitivity greater than those achievable in Fourier-transform infrared spectroscopy. In comparison with prior laboratory submillimeter- wavelength radiation sources, this source is much lighter in weight, less cumbersome, less power-hungry, and capable of sustained operation with less intervention by laboratory personnel. Also, unlike some prior submillimeter-wavelength sources, this source does not require a high-voltage power source. As shown in more detail in the figure, the radiation source includes a sweep frequency synthesizer connected to an external waveform generator, the output of which is used as a reference signal. The synthesizer is computer-controlled through a standard general-purpose interface bus (GPIB) and is operated in phase-locked continuous- wave mode for all measurements. The synthesizer output ranges in frequency from 11 to 18 GHz. For suppression of frequency spurs and harmonics, the output of the frequency synthesizer is fed through a tunable yttrium iron garnet (YIG) filter, which is swept in frequency simultaneously with the frequency synthesizer.

Maiwald, Frank↗
DOE OSTI2026

SPRUCE FT-ICR MS, Bulk Chemistry, and Mass Loss from Litter Decomposition Study in Experimental Plots, Marcell Experimental Forest, Minnesota, 2015-2017

This dataset contains molecular, bulk chemical, and mass loss measurements from a litter decomposition study at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experimental site within the Marcell Experimental Forest in northern Minnesota, USA. This site is in a Sphagnum spp. ombrotrophic bog forest. Litterbags were deployed into the peat in September 2015 across three warming levels (+0, +4.5, and +9°C) under ambient and elevated carbon dioxide (CO₂ - +500 ppm) and retrieved after roughly 0.5, 1, and 2 years of field incubation (2015-09-23 to 2017-08-02). Litterbags containing six peatland litter types: black spruce needles (Picea mariana - SPL), spruce fine roots (SPR), Sphagnum angustifolium (ANG), Sphagnum magellanicum (MAG), Labrador tea leaves (Rhododendron groenlandicum - LTL), and Labrador tea roots (LTR). Molecular composition of water-soluble organic matter extracts was characterized using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) at 9.4 Tesla, operated in negative ion mode with electrospray ionization, providing molecular formula assignments and compound-class distributions across the decomposition time series. Bulk chemical characterization included elemental analysis (percent carbon, nitrogen, and phosphorus) and Fourier Transform Infrared Spectroscopy (FTIR) to quantify functional group composition. Litter mass loss was tracked gravimetrically at each retrieval interval, expressed as percent mass remaining relative to initial dry mass for each litter type and treatment combination. These data are valuable for understanding how vegetation shifts driven by increased atmospheric CO2 and temperature in peatlands alter litter inputs and organic matter stabilization trajectories, with implications for projecting and modeling peatland carbon cycling. This dataset contains two data files in comma-separated value (.csv) format. Additional metadata are provided: two data dictionaries and a file-level metadata file in comma separate (.csv) format and a user guide in PDF (*.pdf) format.

decomposition↗
DOE OSTI2020

Green synthesis and characterization of nontoxic L-methionine capped silver and gold nanoparticles

The simple green method for synthesis of stable L-Methionine (L-Met) capped silver (Ag@LM NPs) and gold (Au@LM NPs) nanoparticles (NPs) without adding any additional reduction agent or stabilizer was developed. Colloidal dispersions were characterized by UV–Vis spectrophotometry. The size and spherical shape of NPs were evaluated by transmission electron microscopy. Their surface covering was confirmed by atomic force microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential measurements. Density functional theory calculations pointed that the preferential adsorption mode of L-Met on both Ag and Au surfaces was a vertical binding geometry via –NH2 group, while horizontal binding mode via [sbnd]S[sbnd] and –NH2 groups is also possible. The genotoxicity (evaluated by the micronucleus assay) of NPs, as well as their effects on some oxidative stress parameters (catalase activity, malondialdehyde level), were assessed in vitro using human peripheral blood cells as a model system. The influence of NPs on the morphology of lymphocyte cells studied using atomic force microscopy revealed that the membrane of cells remained unaffected after the treatment with NPs. When considering the effects of NPs on catalase activity and malondialdehyde level, neither particle type promoted oxidative stress. However, the treatment of lymphocytes with Ag@LM NPs induced a concentration-dependent enhancement of the micronuclei incidence and suppression of the cell proliferation while Au@LM NPs promoted cell proliferation, with no significant effects on micronuclei formation. The Ag@LM NPs were more prone to induce DNA damage than Au@LM NPs, which makes the latter type more suitable for further studies in nano-medicine. © 2019.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Ammonia Permeation Through Inorganic Membranes

Moisture probes are used in the tritium facility to measure the moisture content of the gas stream. When tritium reacts with nitrogen to form ammonia, the ammonia gas damages the sensitive moisture probe. The gas stream tested during this experiment for moisture probe protection is composed of nitrogen and argon gas in conjunction with ammonia and water vapor. The gas stream is filtered through an inorganic membrane due to the high reactivity of tritium and a residual gas analyzer (RGA) is used to measure the ammonia and water vapor in the gas stream, as well as the permeability of nitrogen and argon through the inorganic membranes. The membranes tested were boron nitride and silver. The permeability was compared for each membrane at different pressures and flow rates. Fourier-transformed infrared spectroscopy (FT-IR) was used to compare the membranes before and after ammonia permeation. Ammonia gas is a byproduct formed from tritium gas reacting with nitrogen in the gas stream, similar to the Haber Process which occurs when hydrogen reacts with nitrogen [2]. The corrosive nature of ammonia damages metals and sensitive instruments such as moisture probes. Moisture probes are essential in various gas and liquid processes for measuring the moisture content of a gas. Membrane research has found that graphene oxide membranes successfully uptake ammonia from the gas stream at a humidity of approximately 30% at which point the pores pin closed, preventing gas permeation. Further research is being conducted to find an inorganic membrane that will prevent ammonia permeation thus circumventing damage to the sensitive moisture probe. The permeation measurements for argon and nitrogen gas and water and ammonia vapor were measured at various pressures of 800, 1000, 1200, 1500, 1800, and 2000 torr. The permeability average (PA) was calculated for each filter using a Barrer calculation. The average permeations for each filter were then compared. The gas composition was measured using the RGA Nitrogen was permeated through the membranes after ammonia permeation and a FT-IR spectrum was obtained. Boron Nitride: As the nitrogen pressure increased, the permeability of the membrane decreased from 800-1200 torr and remained relatively unchanged from 1200-2000 torr. The membrane exhibited a slight decrease in argon permeability from 800-1200 torr and a slight increase from 1500-2000 torr. The boron nitride membrane when permeated with ammonia and nitrogen prevented less ammonia permeation compared to the blank filter. The boron nitride filter demonstrated a decrease in permeability after ammonia permeation. Silver Membrane: When permeated with nitrogen alone, the membrane permeability decreased from 800 torr to 1200 torr. The permeability of the membrane showed little difference as pressure increased from 1200 torr. When permeated with argon, the same phenomenon occurred but on a much smaller scale. When compared to the blank and the boron nitride membranes the silver membrane exhibited significantly lower permeability. This may be in part due to the coating on the silver membrane and differences in pore size of the membranes. During permeation with ammonium hydroxide vapor and nitrogen, the partial pressure of the ammonia increased as compared to the blank membrane. The permeability before and after permeation with ammonia and nitrogen were compared. Permeability values suggested that after being permeated with the ammonia that the permeability for lower pressures increased slightly. There was no significant change in the FT-IR spectrums before and after permeation. Future work: Continue testing various inorganic membranes for ammonia permeation. Further research chemical separation of ammonia from the gas stream, which may prove difficult due to the high reactivity of tritium.

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

Optimal Spectral Resolution for Infrared Studies of Solids and Liquids

Due to a legacy originating in the limited capability of early computers, the spectroscopic resolution used in Fourier transform infrared spectroscopy and other systems has largely been implemented using only powers of two for more than 50 years. In this study, we investigate debunking the spectroscopic lore of, e.g., using only 2, 4, 8, or 16 cm −1 resolution and determine the optimal resolution in terms of both (i) a desired signal-to-noise ratio and (ii) efficient use of acquisition time. The study is facilitated by the availability of solids and liquids reference spectral data recorded at 2.0 cm −1 resolution and is based on an examination in the 4000–400 cm −1 range of 61 liquids and 70 solids spectra, with a total analysis of 4237 peaks, each of which was also examined for being singlet/multiplet in nature. Of the 1765 liquid bands examined, only 27 had widths <5 cm −1 . Of the 2472 solid bands examined, only 39 peaks have widths <5 cm −1 . For both the liquid and solid bands, a skewed distribution of peak widths was observed: For liquids, the mean peak width was 24.7 cm −1 but the median peak width was 13.7 cm −1 , and, similarly, for solids, the mean peak width was 22.2 cm −1 but the median peak width was 11.2 cm −1 . While recognizing other studies may differ in scope and limiting the analysis to only room temperature data, we have found that a resolution to resolve 95% of all bands is 5.7 cm −1 for liquids and 5.3 cm −1 for solids; such a resolution would capture the native linewidth (not accounting for instrumental broadening) for 95% of all the solids and liquid bands, respectively. After decades of measuring liquids and solids at 4, 8, or 16 cm −1 resolution, we suggest that, when accounting only for intrinsic linewidths, an optimized resolution of 6.0 cm −1 will capture 91% of all condensed-phase bands, i.e., broadening of only 9% of the narrowest of bands, but yielding a large gain in signal-to-noise with minimal loss of specificity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Operando Investigation of the Molecular Origins of Dipole Switching in P(VDF‐TrFE‐CFE) Terpolymer for Large Adiabatic Temperature Change

Abstract Relaxor ferroelectric polymers exhibiting a giant electrocaloric effect (ECE) can potentially be used to create next‐generation solid‐state coolers. Under an electric field, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer goes through a large dipolar entropy change producing a high adiabatic temperature change (Δ T ECE ). This work resolves the molecular origins of the large entropy change behind the electric field‐induced dipole switching. A Fourier transform infrared spectroscopy equipped with a high voltage source is used to operandoly observe the characteristic molecular vibrational modes. A short‐range trans (T) conformation of the CF 2 ‐CH 2 dyads interrupted by a gauche (G) conformation, e.g., TTTG in the terpolymer chain, undergoes a dynamic transformation that leads to a corresponding Δ T ECE whenever an electric field is applied. The molecular dynamics simulation also proves that the energy barrier that the transformation from TTTGs into a long T sequence overcomes is smaller than that for all other conformations. A mixed solvent system is used to obtain T3G‐enriched terpolymer films exhibiting a 4.02 K Δ T ECE at 60 MV m −1 and these films are employed to manufacture a 2‐layer‐cascaded cooling device that achieves a 6.7 K temperature lift, the highest reported value for a 2‐layer cascaded device made of fluoropolymers.

Zhu, Yuan↗