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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Dynamics of Polymerization and Gelation in Epoxy Nanocomposites via X-ray Photon Correlation Spectroscopy

The details of the curing process of epoxy resins are notoriously difficult to ascertain, hampering polymer matrix composite manufacturing. Here, the curing of a series of six epoxy resins containing dilute spherical nanoparticles was investigated via X-ray photon correlation spectroscopy (XPCS). The resin formulation was varied to achieve a range of crosslink densities and topologies. Prior to gelation, the viscosities obtained from XPCS agreed with bulk rheology. A clear dynamic transition was detected in all samples, where the q-scaling changes from approximately q2 .2 to q 1 , indicating a transition from sub-diffusive to ballistic-like nanoparticle motion. For the samples with a high crosslink density, this change was abrupt and coincided with gelation, and there was no evidence of crosslink heterogeneity. Chain entanglement played a role in the transition for samples with lower crosslink density. Finally, this work reveals the potential of XPCS to deliver new quantitative insights into the curing process of thermosetting resins.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Evidence for C ii diffuse line emission at redshift z ∼ 2.6

ABSTRACT C ii is one of the brightest emission lines from star-forming galaxies and is an excellent tracer for star formation. Recent work measured the C ii emission line amplitude for redshifts 2 < z < 3.2 by cross-correlating Planck High Frequency Instrument emission maps with tracers of overdensity from the Baryon Oscillation Spectroscopic Sky Survey, finding ${I}_{{\text C}\,\rm {\small II}}=6.6^{+5.0}_{-4.8}\times {10}^{4}$ Jy sr−1 at $95\,{\text{per cent}}$ confidence level. In this paper, we present a refinement of this earlier work by improving the mask weighting in each of the Planck bands and the precision in the covariance matrix. We report a detection of excess emission in the 545 GHz Planck band separate from the cosmic infrared background (CIB) present in the 353–857 GHz Planck bands. This excess is consistent with redshifted C ii emission, in which case we report $b_{{\text C} \,\rm {\small II}}I_{{\text C} \,\rm {\small II}} =2.0^{+1.2}_{-1.1}\times 10^5$ Jy sr−1 at $95\ {\text {per cent}}$ confidence level, which strongly favours many collisional excitation models of C ii emission. Our detection shows strong evidence for a model with a non-zero C ii parameter, though line intensity mapping observations at high spectral resolution will be needed to confirm this result.

Yang, Shengqi↗
DOE OSTI2025

Hygrothermal Aging and Thermomechanical Characterization of As-Manufactured Tidal Turbine Blade Composites

This study investigates the hygrothermal aging behavior and thermomechanical properties of as-manufactured glass fiber-reinforced epoxy and thermoplastic composite tidal turbine blades. The blades were previously deployed in a marine environment and subsequently analyzed through a comprehensive suite of material characterization techniques, including hygrothermal aging, dynamic mechanical analysis (DMA), tensile testing and X-ray computed tomography (XCT). Hygrothermal aging experiments revealed that while thermoplastic composites exhibited lower overall water absorption (0.78% vs. 0.47%), they had significantly higher diffusion coefficients than epoxy (2.1 vs. 12.1 × 10 −13 m 2 s −1 ), suggesting faster saturation in operational environments. DMA results demonstrated that water ingress caused plasticization in epoxy matrices, reducing the glass transition temperature and increasing damping (112 °C to 104 °C), while thermoplastic composites showed more stable thermal behavior (87 °C glass transition temperature). Tensile testing revealed substantial reductions in ultimate strength (>40%) for both materials after prolonged water exposure, with minimal change in elastic modulus, highlighting the role of matrix degradation over fiber reinforcement. XCT image analysis showed that both composites were manufactured with high quality: no large voids or cracks were present, and the degree of misalignment was low. These findings inform future marine renewable energy composite designs by emphasizing the critical influence of moisture on long-term structural integrity and the need for optimized material systems in harsh marine environments. This work provides a rare real-world comparison of epoxy and recyclable thermoplastic tidal turbine blades, showing how laboratory aging tests and advanced imaging reveal the influence of material and manufacturing choices on long-term marine durability.

16 TIDAL AND WAVE POWER↗
DOE OSTI2018

Probing long-range ordering in nickel-base alloys with proton irradiation

In this paper, twelve commercial-grade austenitic alloys based on the Ni-Cr-Mo-Fe quaternary system were irradiated using 2 MeV protons at 360 °C to a damage level of 2.5 displacements per atom (dpa). Long-range ordered (Pt 2 Mo-type) precipitation under proton irradiation was observed, for the first time, in alloys C22, 625, 625P, 625D, 725, and 690. No relevant short-range ordering was observed. These irradiation-enhanced long-range ordered precipitates are coherent with the matrix despite their irregular shape. Of the potential influences on long-range ordering (Ni:Cr, and Ni:(Cr + Mo) ratios, Mo, and iron concentration), Fe content was the strongest by far. The volume fraction of LRO decreases with increasing Fe content by virtue of its role as a stabilizer of the disordered FCC phase, thus reducing the energy savings from ordering. The observed effects of Fe on long-range ordering show qualitative agreement with predictions from thermodynamic modeling. Although solid state diffusion kinetics dominate long-range ordering under purely thermal conditions, ordering under irradiation here (~ 2.5dpa) is controlled by the thermodynamic driving force. Finally, proton irradiation thus offers a unique approach for studying the low temperature phase transformation in a thermodynamically favored, but kinetically constrained condition.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hydrogen Uptake Kinetics of 1,4-Bis(phenylethynyl)benzene Rubberized O-Rings: Measurements, Modeling, and Comparison with Additional Forms of Organic Getters

A class of molecules called “hydrogen getters” can react with, or scavenge, H 2 in applications where the hydrogen presence and/or buildup are not desirable. One such “getter”, 1,4-bis(phenylethynyl)benzene or DEB, can be incorporated into a silicone matrix in the form of an O-ring for added flexibility, environmental resiliency, and convenient use as a gasket in sealed applications. However, the performance and kinetics of this DEB-loaded rubberized O-ring have not yet been characterized. Here in this work, the hydrogen uptake kinetics of the rubberized DEB O-ring were extracted by the isoconversional analysis from isothermal isobaric data under conditions of 13,332 Pa H 2 and 305–325 K. The isoconversional and cylindrical diffusion approximations were then used to predict and model the hydrogen uptake of rubberized DEB O-rings under any arbitrary condition, as illustrated in this work for the simple case of a constant rate of hydrogen generation/input. In comparison with other Pd/carbon-based/organic getter systems, these rubberized DEB O-rings provide a type of hydrogen getter material with enhanced flexibility and catalyst protection in applications where an O-ring seal is needed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

NXREFINE

NXRefine implements a complete workflow for both data acquisition and reduction of single crystal diffuse x-ray scattering collected as a series of area detector frames during continuous sample rotation. The data are stored in HDF5 files, which conform to the NeXus data format standard. These files contain a comprehensive set of metadata, including the incident wavelength, powder calibration scans used to define detector distances, beam centers, and yaw, pitch, and roll corrections. Automated peak searches of the three-dimensional data arrays define a set of Bragg peaks that are used to define an orientation matrix, defined according to Busing and Levy, which is then used to transform the data from angular coordinates to reciprocal space coordinates using the CCTW program. Multiple rotations at different detector translations and offset rotation axes are combined to ensure that there are no gaps in the reconstructed data, and allow the construction of masks to eliminate detector artifacts due to Compton scattering within the sensor layers. Finally, the data can be transformed into 3D-ΔPDF maps using the punch-and-fill method after symmetrization.

OSBORN, RAYMOND↗
DOE OSTI2014

Electronic couplings for molecular charge transfer: Benchmarking CDFT, FODFT, and FODFTB against high-level ab initio calculations

We introduce a database (HAB11) of electronic coupling matrix elements (H{sub ab}) for electron transfer in 11 π-conjugated organic homo-dimer cations. High-level ab inito calculations at the multireference configuration interaction MRCI+Q level of theory, n-electron valence state perturbation theory NEVPT2, and (spin-component scaled) approximate coupled cluster model (SCS)-CC2 are reported for this database to assess the performance of three DFT methods of decreasing computational cost, including constrained density functional theory (CDFT), fragment-orbital DFT (FODFT), and self-consistent charge density functional tight-binding (FODFTB). We find that the CDFT approach in combination with a modified PBE functional containing 50% Hartree-Fock exchange gives best results for absolute H{sub ab} values (mean relative unsigned error = 5.3%) and exponential distance decay constants β (4.3%). CDFT in combination with pure PBE overestimates couplings by 38.7% due to a too diffuse excess charge distribution, whereas the economic FODFT and highly cost-effective FODFTB methods underestimate couplings by 37.6% and 42.4%, respectively, due to neglect of interaction between donor and acceptor. The errors are systematic, however, and can be significantly reduced by applying a uniform scaling factor for each method. Applications to dimers outside the database, specifically rotated thiophene dimers and larger acenes up to pentacene, suggests that the same scaling procedure significantly improves the FODFT and FODFTB results for larger π-conjugated systems relevant to organic semiconductors and DNA.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

A multi-physics constitutive model to predict hydrolytic aging in quasi-static behaviour of thin cross-linked polymers

The effect of hydrolytic aging on mechanical quasi-static responses of rubber-like materials, in particular, the idealized Mullins effect and permanent set have been modeled. The effect of hydrolytic damage on the mechanical integrity of the polymer matrix is modeled as the direct competition of two micro-structural phenomena (i) chain scission and (ii) reduction of cross-links. Both phenomena and their correlation were modeled and thus, the strain energy of the polymer matrix is written with respect to three independent mechanisms; i) the shrinking original matrix that has not been attacked by water, ii) conversion of the first network to a new network due to the reduction of the cross-links, and iii) energy loss from network degradation due to water attacks to polymer active agents. The proposed model satisfies the Clausius-Duhem inequality and is thus physically feasible. The model is validated with respect to sets of our experimental data and other sets available in the literature. The proposed model is based on the assumption of homogeneous diffusion and mainly relevant for thin samples. In view of its accuracy, interpret-ability, and deep insight it provides into the nature of damage accumulation, the model is a good choice for further implementation in FE applications.

42 ENGINEERING↗
DOE OSTI2015

Search for 0ν2β of {sup 100}Mo by NEMO-3 and status of SuperNEMO

The NEMO-3 experiment was devoted to the research of the neutrinoless double beta decay and the precise measurement of the two-neutrino double beta decay of seven isotopes. The detector took data in the Laboratoire Souterrain de Modane (LSM) from 2003 to 2011. The unique combination of a 3D-tracker and a calorimeter allowed to fully reconstruct the double beta decay events topology and strongly reduces the backgrounds. This feature also permitted to characterize the remaining backgrounds in independent analysis channels. With an exposure of 34.7 kg·y of {sup 100}Mo no evidence for the 0ν2β signal has been found, yielding a limit for the light Majorana neutrino mass mechanism of T{sub 1/2}(0ν2β) > 1.1 10{sup 24} years (90 % C.L.) once both statistical and systematic uncertainties are taken into account. Depending on the Nuclear Matrix Elements this corresponds to an upper limit on the Majorana effective neutrino mass of |m{sub ββ}| < 0.3 − 0.9 eV (90 % C.L.). Constraints on other lepton number violating mechanisms of 0ν2β decays are also given. Searching for high-energy double electron events in all suitable sources of the detector, no event in the energy region [3.2-10] MeV is observed for an exposure of 47 kg·y. The next generation experiment, SuperNEMO, will use the same experimental technique to extend the sensitivity on the neutrinoless double beta decay search. Several aspects have been improved compared to NEMO-3: choice of the isotope, energy resolution, energy losses… but the main challenge is the background reduction. All the detector materials have been selected for their low natural radioactivity contaminations through High Purity Germanium (HPGe) gamma spectroscopy. The double beta sources after enrichment are being prepared with extreme care and the ultimate contaminations will be characterized by the most sensitive BiPo detector. External radon tightness and internal radon emanation have been studied to ensure a very low level in the tracker with very sensitive complementary detectors: diffusion apparatus, concentration line and emanation tanks. The construction of the first detector, called the demonstrator, has started in 2012. Studying 7 kg of {sup 82}Se, the demonstrator will reach the NEMO-3 sensitivity in only 5 months and improve it by at least a factor 6 in 2.5 years. Underground installation will start fall 2014 and physics data taking should start by summer 2015.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Dissimilar Joining of Pure Aluminum to SiC{sub p}/Al-MMCs Using an AlMgGaLi Active Interlayer Foil

To broaden the application of advanced metal matrix composites in the electronic packaging industry, a lead-free AlMgGaLi interlayer was developed for active soldering of aluminum to aluminum metal matrix composites. The effect of joining pressure on the microstructure evolution, interfacial wettability and mechanical properties of the dissimilar joints was investigated. The experimental results indicated that as the joining pressure increased, the mean thickness of the bond seam was 46.02 μm, and solidification of a solid solution occurred (detected by SEM/XRD analysis). The composition of the Al-based solid solution (in atom%) was 86.52% Al, 9.32% Mg, 2.56% O, 1.5% Ga and 0.1% Si. The pressure improved the interfacial wettability by enhancing the atom diffusion between the interlayer and parent materials. The joint shear strength initially increased and then decreased, and a sound joint with a maximum shear strength of ~ 45 MPa was produced at 450 °C and 0.75 MPa. The fracture crack initially occurred at the interfaces of the Al/filler metal and then propagated mainly along the Al{sub 2}O{sub 3} layer on the Al side. A novel model describing the pressure-induced microstructure changes within the joint and the formation of an Al{sub 2}O{sub 3} diffusion barrier layer at the Al/filler metal interface is proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Optical absorptions of oxygenated carbon chain cations in the gas phase

The gas-phase electronic spectra of linear OC{sub 4}O{sup +} and a planar C{sub 6}H{sub 2}O{sup +} isomer were obtained at a rotational temperature of ≈10 K. Absorption measurements in a 6 K neon matrix were followed by gas-phase observations in a cryogenic radiofrequency ion trap. The origin bands of the 1{sup 2}Π{sub u} ← X{sup 2}Π{sub g} transition of OC{sub 4}O{sup +} and the 1{sup 2}A{sub 2} ←X{sup 2}B{sub 1} of HCCC(CO)CCH{sup +} lie at 417.31 ± 0.01 nm and 523.49 ± 0.01 nm, respectively. These constitute the first electronic spectra of oxygenated carbon chain cations studied under conditions that are relevant to the diffuse interstellar bands (DIBs), as both have a visible transition. The recent analysis of the 579.5 nm DIB indicates that small carriers, five to seven heavy atoms, continue to be possible candidates (Huang and Oka 2015). Astronomical implications are discussed regarding this kind of oxygenated molecules.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

A non‐intrusive domain‐decomposition model reduction method for linear steady‐state partial differential equations with random coefficients

Abstract Domain decomposition methods have been proved to be an effective strategy to reduce the dimension of parametric partial differential equations (PDEs). However, existing domain decomposition methods for parametric PDEs are usually intrusive, which means domain decomposition based solvers need to be implemented from scratch for each target parametric PDE. To address this issue, we develop a new non‐intrusive domain‐decomposition model reduction method for linear steady‐state PDEs with random‐field coefficients. As a variant of our previous work by Mu and Zhang, the new method only needs access to the final linear system, that is, the global stiffness matrix and the right hand side, of a deterministic PDE solver, in order to build a domain‐decomposition‐based reduced model without intrusive implementation from scratch. The key idea is to remove the interface condition between sub‐domains and rely on the correlation between columns of the linear system to couple the sub‐domains. The non‐intrusive feature enables the applicability of the proposed method to a broader class of uncertainty quantification problems, where many legacy codes/solvers can be fully reused by our method. Two numerical examples including diffusion equations with random diffusivity and convection‐dominated transport with random velocity, are provided to demonstrate the effectiveness and efficiency of our method.

Zhang, Guannan↗
DOE OSTI2021

Gas transport characteristics of supramolecular networks of metal-coordinated highly branched Poly(ethylene oxide)

Model systems are developed and investigated to better understand the effect of polyether-metal ion interactions on gas separation characteristics. These systems help answer current questions raised by the substantial body of research on metal-organic frameworks (MOFs) dispersed in polyethers to improve gas separation performance, where favorable interactions between the metal centers and polyethers are preferred to improve interfacial compatibility. Specifically, we investigate CO 2 /gas transport properties of supramolecular networks comprising cross-linked poly(ethylene oxide) (XLPEO) and dissociable salts, including LiClO 4 , Ni(BF 4 ) 2 , and Cu(BF 4 ) 2 . Increasing the salt content increases the glass transition temperature (T g ) and generally decreases gas diffusivity and permeability, which can be successfully described using a T g -integrated free volume model with an expression similar to the Vogel-Tammann-Fulcher (VTF) equation. Surprisingly, low loadings of LiClO 4 and Cu(BF 4 ) 2 (2 mass% or less) can increase gas permeability by 30%–70% without affecting the CO 2 /gas selectivity. This increase correlates with polyether-metal ion dynamics as measured by dielectric spectroscopy. Understanding how interaction-mediated dynamics affect gas transport will be instrumental to designing MOF-based mixed matrix materials for gas separations.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Chromium-doped uranium dioxide fuels: A review

UO 2 doped with parts per million CR 2 O 3 powder is considered a potential near term accident tolerant fuel candidate. Here, the results of decades of industry and academic research into Cr-doped UO 2 are analyzed and their shortcomings are critiqued. Focusing on the incorporation mechanisms of Cr into the fuel matrix, we explore a mechanistic understanding of the characteristic properties of Cr-doped UO 2 , notably, enhanced fission gas retention attributed to enlarged grain sizes following sintering, along with marginal improvements in the thermophysical properties. The findings of recent X-ray Adsorption Near Edge Spectroscopy studies were compared and put into conversation with historic data regarding the incorporation of Cr in UO 2 . On the basis of defect mechanisms, the case is made for the substitutional incorporation of Cr governing the lattice solubility but not the enhanced U diffusivity. Instead, Cr/CR 2 O 3 redox chemistry in a well-defined oxygen potential explains the differences in the U diffusivity and O/M ratio. The primary mechanism of doping enhanced grain growth is found to be liquid assisted sintering due to a CRO (1) eutectic phase at the grain boundaries. The role of inhomogeneities in Cr concentration in UO 2 at various length scales across the materials microstructure is highlighted and connected to promising experimental and modeling work to fill in the gaps in the current understanding of Cr-doped UO 2 . The review considers both the open scientific questions and engineering applications to illustrate the deep connections between the practice and theory in the design of accident tolerant nuclear fuels. In conclusion, the review ends with an outline of future works that combine meticulous irradiation studies and high resolution experiments with next generation modeling and simulations techniques empowered by machine learning advances to accelerate the fabrication and adoption of Cr-doped UO 2 light water reactors.

Cleveland, Mack Wesley [Massachusetts Inst. of Tec↗
DOE OSTI2020

Pinning dislocations in colloidal crystals with active particles that seek stacking faults

There is growing interest in functional, adaptive devices built from colloidal subunits of micron size or smaller. A colloidal material with dynamic mechanical properties could facilitate such microrobotic machines. Here we study via computer simulation how active interstitial particles in small quantities can be used to modify the bulk mechanical properties of a colloidal crystal. Passive interstitial particles are known to pin dislocations in metals, thereby increasing resistance to plastic deformation. We extend this tactic by employing anisotropic active interstitials that travel super-diffusively and bind strongly to stacking faults associated with partial dislocations. We find that: (1) interstitials that are effective at reducing plasticity compromise between strong binding to stacking faults and high mobility in the crystal bulk. (2) Reorientation of active interstitials in the crystal depends upon rotational transitions between high-symmetry crystal directions. (3) The addition of certain active interstitial shapes at concentrations as low as 60 per million host particles (0.006%) can create a shear threshold for dislocation migration. This work demonstrates how active materials in a dense matrix can locally sense their environment and lead to bulk property changes.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Experimental Investigation of Cellulose/Silver Nanocomposites Using In Situ Generation Method

Cellulose gel films were prepared by regeneration process using pre-cooled aq.(8 wt% LiOH + 15 wt% urea) mixture as solvent and ethyl alcohol as non solvent. The Terminus cattapa leaf extract diffused wet cellulose films were then dipped in 1–5 mM aq.AgNO{sub 3} solutions to allow in situ generation of silver nanoparticles (AgNPs). Besides the in situ generation, some AgNPs were also formed outside the wet films in the solution. The AgNPs formed outside the films were observed under transmission electron microscope and scanning electron microscope. The nanocomposite films were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis and tensile test. The thermal stability of the composite films was lower than that of the matrix up to a temperature of ~300 °C and afterwards showed a reverse trend. The tensile strength of the nanocomposite films was found to be higher than the matrix but decreased with increasing concentration of aq.AgNO{sub 3}. The cellulose/AgNPs composite films showed good antibacterial activity against E. coli (gram positive) and Bacillus sp. (gram negative). Based on the aforementioned properties, the cellulose/AgNPs composite films can be considered for antibacterial packaging and medical applications.

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

Chemical compatibility of hollow ceramic cenospheres as thermal insulation for high-temperature thermal energy storage applications with molten nitrate salt

An effective insulation material that is both thermally and chemically stable in molten salts could transform the design of molten-salt-based thermal energy storage (TES) tanks. Most current molten salt TES tanks hold the metallic tank structure in direct contact with hot salt inventory, a design which leads to thermal expansion of the tank and triggers stresses that can lead to thermomechanical failures. With an internal insulation to lower the temperature at the tank structure, the extent of thermal expansion can be reduced, thereby reducing expansion-induced stresses and allowing for consideration of lower-cost tank structure materials. Conventional insulation materials are either 1) too porous and allow molten salts to permeate into the matrix, which significantly increases the thermal conductivity or 2) too dense and have a thermal conductivity that cannot provide sufficient thermal insulation. This paper presents an alternative thermal insulation concept using cenospheres which have an alumino-silicate structure. The cost analysis suggests that the low-density cenospheres can be one of the cheapest materials to provide cost-effective thermal insulation. The chemical compatibility of cenospheres is investigated in molten 60 wt% NaNO3/40 wt% KNO3 salt which is close to industrial-grade Solar Salt. This paper shows that diffusion of the sodium and potassium cations from the salt into the cenospheres occurs based on weight analysis, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The cation diffusion breaks the bridging oxygen bonds and causes volume expansion of the microstructure which is responsible for the failure of the cenosphere particles. The chemical composition of the cenospheres is found to affect their compatibility with molten nitrate salt. A cenosphere product with low iron content showed the best compatibility with an average survival rate of 77.9% +/- 9.8% after 7 days of immersion in the molten nitrate salt. While even the low-iron cenospheres appear to require protection from direct molten salt contact, their slow degradation rate, closed-cell porosity, and low cost hold potential for effective use as internal tank insulation.

14 SOLAR ENERGY↗