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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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Using mid-infrared spectroscopy to estimate soil microbial properties at the continental scale

Understanding microbial community properties is critical to improving the predictions of biogeochemical processes for enhancing soil carbon sequestration. Here, in this observational study, mid-infrared (MIR) spectroscopy and partial least squares regression was used to predict soil microbial and chemical properties from diverse ecosystems across the continental USA. Random calibration and validation demonstrated the prediction potential for soil properties using MIR spectra, with the strongest predictions for microbial respiration, followed by microbial biomass carbon and nitrogen, ß-glucosidase activity, as well as soil chemical properties including organic carbon and total nitrogen. Microbial properties were mainly positively correlated to spectral regions associated with aliphatic C-H groups and C=O stretches of polysaccharides and negatively correlated to quartz and silicate-associated regions. We conclude that MIR spectroscopy can characterize soil microbial functions and be useful for the improvement of continental-scale soil carbon modeling and prediction programs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Inorganic polymers from laterite using activation with phosphoric acid and alkaline sodium silicate solution: Mechanical and microstructural properties

Geopolymers from laterite, an iron-rich soil available in developing countries, have great potential as building materials. In this work, laterite from Togo (Africa) was used to prepare geopolymers using both phosphoric acid and alkaline sodium silicate solution. Microstructural properties were investigated by scanning electron microscopy, X-ray powder diffraction and mercury porosimetry, whereas thermal properties were evaluated by thermal analyses. The local environment of iron was studied by X-ray Absorption Spectroscopy (XANES region). The mechanical properties were determined. Modulus of Rupture and Young's modulus fell in the ranges 3.3–4.5 MPa and 12–33 GPa, respectively, rendering the materials good candidates for construction purposes. Heating above 900 °C results in weight-gain, presumably due to iron redox reactions. X-ray Absorption Spectroscopy data evidence changes in the chemical and structural environments of iron following thermal treatment of geopolymers. These changes indicate interaction between the geopolymer structure and iron during heating, possibly leading to redox properties. -- Highlights: •Geopolymerization of laterite is promising for fabrication of building materials. •Both phosphoric acid and alkaline sodium silicate solution can be used for activation. •Thermally activated redox properties of the inorganic polymers were observed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Fracture properties and microstructure formation of hardened alkali-activated slag/fly ash pastes

This study presents a comprehensive experimental investigation on the fracture properties of hardened alkali-activated slag/fly ash (AASF) pastes in relation to the microstructure formation and reaction product composition. The main reaction product in AASF is C-(N-)A-S-H gel along with minor hydrotalcite phase, with the polymerization of C-(N-)A-S-H gel substantially governed by its Ca/Si ratio. Strong positive correlations are identified between the Ca/Si ratios of C-(N-)A-S-H gel and the fracture properties K{sub Ic} (J{sub tip}), whereas, the compressive strength of AASF pastes is primarily determined by its capillary porosity (>0.01 μm). The disagreements between the Ca/Si ratios and corresponding intrinsic mechanical properties of C-(N-)A-S-H gel as proof by contradiction indicate that the fracture properties K{sub Ic} (J{sub tip}) of AASF pastes could be dominated by a cohesion/adhesion-based mechanism. These findings provide promising guidance for fine-tuning the fracture properties of AASF and also advise on the tailoring strategies for high-performance composite such as strain-hardening geopolymer composite.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Denoising diffusion algorithm for inverse design of microstructures with fine-tuned nonlinear material properties

Here we introduce a denoising diffusion algorithm to discover microstructures with nonlinear fine-tuned properties. Denoising diffusion probabilistic models are generative models that use diffusion-based dynamics to gradually denoise images and generate realistic synthetic samples. By learning the reverse of a Markov diffusion process, we design an artificial intelligence to efficiently manipulate the topology of microstructures to generate a massive number of prototypes that exhibit constitutive responses sufficiently close to designated nonlinear constitutive behaviors. To identify the subset of microcstructures with sufficiently precise fine-tuned properties, a convolutional neural network surrogate is trained to replace high-fidelity finite element simulations to filter out prototypes outside the admissible range. Results of this study indicate that the denoising diffusion process is capable of creating microstructures of fine-tuned nonlinear material properties within the latent space of the training data. More importantly, this denoising diffusion algorithm can be easily extended to incorporate additional topological and geometric modifications by introducing high-dimensional structures embedded in the latent space. Numerical experiments are conducted on the open-source mechanical MNIST data set (Lejeune, 2020). Consequently, this algorithm is not only capable of performing inverse design of nonlinear effective media, but also learns the nonlinear structure–property map to quantitatively understand the multiscale interplay among the geometry, topology, and their effective macroscopic properties.

42 ENGINEERING↗
DOE OSTI2024

Elemental and layer based analysis of optical properties: A new technique applied to four MAX-phases

Here we present here a novel technique to calculate partial contributions to the optical properties by atoms, elements, and layers. Following the same methodology as the calculation of the partial density of states from the density of states, we have decomposed the optical properties into the partial optical properties. Using this technique the differences of elemental resolved optical properties as well as layer-resolved optical properties are displayed for both the 211 and 312 phases of TiSiC and TiAlC MAX-phase materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A machine learning approach to determine the elastic properties of printed fiber-reinforced polymers

This work focuses on the simultaneous determination of the elastic constants and the fiber orientation state for a short fiber-reinforced polymer composite by performing a minimum of experimental tests. Here we introduce a methodology that enables the inverse determination of fiber orientation state and the in-situ polymer properties by performing tensile tests at the composite coupon level. We demonstrate the approach for the extrusion deposition additive manufacturing (EDAM) process to illustrate one application of the methodology, but the development is such that it can be applied to short fiber-reinforced polymer (SFRP) systems processed via other methods. Currently, developing composites additive manufacturing digital twins require extensive material characterization. In particular, the mechanical characterization of the orthotropic elastic properties of a composite involves extensive sample preparation and testing, therefore the elasticity tensor is generally populated using a micromechanics model. This, however, requires measuring the fiber orientation state in addition to knowing the constituent material properties. Experimentally measuring the fiber orientation state can be tedious and time consuming. Further, optical methods are limited to resolving the orientation of cylindrical fibers or cluster of non-cylindrical fibers, and computed tomography (CT) methods scan regions of volume that are much smaller than a full printed bead. Therefore, we propose a methodology, accelerated by machine learning, to identify the anisotropic mechanical properties and fiber orientation state at the same time. Early results show that inference of the fiber orientation and composite properties is possible with as few as three tensile tests. Our results show that a combination of the choice of the micromechanics model and reliable set of experiments can yield the nine elastic constants, as well as, the fiber orientation state.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The MOOSE fluid properties module

The Fluid Properties module within the Multiphysics Object-Oriented Simulation Environment (MOOSE) is used to compute fluid properties for numerous applications, ranging from nuclear reactor thermal hydraulics to geothermal energy. Those applications drove the development of the module to enable numerous different fluid equations of states, property lookups with primitive and conserved flow variable to cater to pressure and density-driven solvers, and an object-oriented design facilitating expansion and maintenance. Each fluid property is implemented in its own class but inherits capabilities such as automatic differentiation, automated out-of-bounds handling or variable conversion capabilities. Here, this paper presents the module, its design, its user and developer interface, its content in terms of fluids and properties, and several of its applications showing its major role in the MOOSE simulation ecosystem.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2025

Adaptive Interface-PINNs (AdaI-PINNs) for inverse problems: Determining material properties for heterogeneous systems

Here, we determine spatially varying discontinuous material properties using a domain-decomposition based physics-informed neural networks (PINNs) framework named the Adaptive Interface-PINNs or AdaI-PINNs (Roy et al., 2024). We propose the use of distinct neural networks for the field variables and material properties within each material, utilizing adaptive activation functions. While the neural networks across different materials share the same weights and biases, their activation functions are uniquely tailored using a hyperparameter that influences the slope of the activation function. The proposed framework is tested on several one-dimensional and two-dimensional benchmark examples, and its performance is compared with conventional PINNs and existing domain-decomposition PINNs frameworks, namely, the Multi-domain physics-informed neural network (M-PINN), and the eXtended physics-informed neural networks (XPINNs). The results demonstrate that the proposed approach can determine randomly distributed discontinuous material properties with an L 2 error of $\mathscr{O}$ (10 -3 ) for the material property and the root-mean-square error of $\mathscr{O}$ (10 -3 ) for the primary variable while the other approaches yield errors that are approximately two orders of magnitude larger (that is, $\mathscr{O}$ (10 -1 )). Moreover, the spatial distribution of material properties obtained using the proposed framework is in close agreement with the true distribution, whereas the other approaches fare much worse. Additionally, the proposed approach is approximately 40% faster than its competitors, indicating its potential as a robust alternative for solving inverse problems in heterogeneous materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Revealing the relationship between molecular weight of lignin and its color, UV-protecting property

Lignin has great potential as a natural, green, and sustainable broad-spectrum sunscreen active ingredient. However, the coexistence of dark color and sunscreen properties hinders its application in cosmetics. In this study, we focus on the effects of the molecular weight of lignin on tis UV-protecting property and color in order to prepare lignin-based sunscreen with high performance. We report a prepared sunscreen containing low molecular weight lignin (F5, <1000 g/mol) exhibits good UV-protecting property (sun protection factor (SPF) = 7.14) and light color advantages (ΔE = 46.2). Moreover, a strong synergistic effect on UV-protecting property exists between low molecular weight lignin and ethylhexyl methoxycinnamate (EHMC), resulting in high SPF of F5@EHMC-based sunscreen (55.56). Additionally, added TiO 2 can efficiently mitigate the dark color of lignin-based sunscreens due to prominent covering power of TiO 2 . Moreover, lignin-based sunscreens have good biocompatibility with HaCaT cells. This work is useful for understanding the mechanism of the UV-protecting property and dark color of lignin, and for designing an efficient and safe lignin-based sunscreen.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

First-principles calculations of the electronic structure and optical properties of K{sub 1-x}Na{sub x}TaO{sub 3} (x=0, 0.25, 0.5, 0.75, 1)

The first-principles calculations are performed to investigate the cubic phase composite K{sub 1-x}Na{sub x}TaO{sub 3}(x=0, 0.25, 0.5, 0.75, 1), by using density functional theory (DFT) with the full potential linearized augmented plane wave (FP-LAPW) method. The energy band structures, density of states (DOS), electron density and optical properties are obtained. The results show that Na ion plays an important role in K{sub 1-x}Na{sub x}TaO{sub 3}. With the content of Na ion increasing, the changes of lattice parameters, energy gaps, bond lengths and optical properties of K{sub 1-x}Na{sub x}TaO{sub 3} are regular. Moreover, the dependence of ferroelectric photocatalysis on both optical properties and internal electronic structure are analyzed in detail. It is proposed that the doped materials are promising photocatalytic materials. - Graphical abstract: The density of states (DOS) of K{sub 1-x}Na{sub x}TaO{sub 3} (x=0.5). Highlights: Black-Right-Pointing-Pointer The first-principles calculations are performed, by using DFT with FP-LAPW method. Black-Right-Pointing-Pointer The changes of internal electronic structure and optical property of doped materials are regular. Black-Right-Pointing-Pointer The dependence of ferroelectric photocatalysis on optical properties is analyzed. Black-Right-Pointing-Pointer The dependence of ferroelectric photocatalysis on internal electronic structure is analyzed. Black-Right-Pointing-Pointer The doped materials are promising photocatalytic materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Polycrystalline Mg{sub 2}Si thin films: A theoretical investigation of their electronic transport properties

The electronic structures and thermoelectric properties of a polycrystalline Mg{sub 2}Si thin film have been investigated by first-principle density-functional theory (DFT) and Boltzmann transport theory calculations within the constant-relaxation time approximation. The polycrystalline thin film has been simulated by assembling three types of slabs each having the orientation (001), (110) or (111) with a thickness of about 18 Å. The effect of applying the relaxation procedure to the thin film induces disorder in the structure that has been ascertained by calculating radial distribution functions. For the calculations of the thermoelectric properties, the energy gap has been fixed at the experimental value of 0.74 eV. The thermoelectric properties, namely the Seebeck coefficient, the electrical conductivity and the power factor, have been determined at three temperatures of 350 K, 600 K and 900 K with respect to both the energy levels and the p-type and n-type doping levels. The best Seebeck coefficient is obtained at 350 K: the S{sub yy} component of the tensor amounts to about ±1000 μV K{sup −1}, depending on the type of charge carriers. However, the electrical conductivity is much too small which results in low values of the figure of merit ZT. Structure–property relationship correlations based on directional radial distribution functions allow us to tentatively draw some explanations regarding the anisotropy of the electrical conductivity. Finally, the low ZT values obtained for the polycrystalline Mg{sub 2}Si thin film are paralleled with those recently reported in the literature for bulk chalcogenide glasses. - Graphical abstract: Structure of the polycrystalline thin film of Mg{sub 2}Si. - Author-Highlights: • Polycrystalline Mg{sub 2}Si film has been modelled by DFT approach. • Thermoelectric properties have been evaluated by semi-classical Boltzmann theory. • The structure was found to be slightly disordered after relaxation. • The highest value of Seebeck coefficient reaches −1000 μV/K at 350 K. • The ZT value is estimated between 0.0175 at 350 K and 0.2 at 900 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Effect of Na substitution on electronic and optical properties of CuInS{sub 2} chalcopyrite semiconductor

Electronic & optical properties of Na substituted CuNaIn{sub 2}S{sub 4} chalcopyrite semiconductors are significantly modified due to Na substitution in the Cu deficient CuInS{sub 2} semiconductor. These properties are obtained form first principle calculation using density functional theory based tight binding Linear muffin tin orbital method. The presence of Na alters the structural distortion and enhances strengths of Cu d and S p hybridization in CuNaIn{sub 2}S{sub 4}. This effect reduces band gap, in agreement with experimental observations and modify other properties significantly. Calculations of optical matrix elements (OME) and joint density of states (JDOS) show that effects of Na substitution on optical properties come through p–d hybridization and structural distortion. OME contribution is prominent near band edge. Both systems show anisotropic optical properties. - Graphical abstract: The figure shows the band structure and total density of states of CuNaIn{sub 2}S{sub 4}. It illustrates energy bands at various symmetry points, band gap and contribution of various orbitals.

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

Synthesis, crystal structure and electrical properties of the tetrahedral quaternary chalcogenides CuM{sub 2}InTe{sub 4} (M=Zn, Cd)

Quaternary chalcogenides form a large class of materials that continue to be of interest for energy-related applications. Certain compositions have recently been identified as possessing good thermoelectric properties however these materials typically have the kesterite structure type with limited variation in composition. In this study we report on the structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} which crystallize in the modified zinc-blende crystal structure, and compare their properties with that of CuZn{sub 2}InSe{sub 4}. These p-type semiconductors have direct band gaps of about 1 eV resulting in relatively high Seebeck coefficient and resistivity values. This work expands on the research into quaternary chalcogenides with new compositions and structure types in order to further the fundamental investigation of multinary chalcogenides for potential thermoelectrics applications. - Graphical abstract: The structural, optical and electrical properties of the quaternary chalcogenides CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. The unique crystal structure allows for relatively good electrical transports and therefore potential for thermoelectric applications. - Highlights: • The physical properties of CuZn{sub 2}InTe{sub 4} and CuCd{sub 2}InTe{sub 4} are reported for the first time. • These materials have potential for thermoelectric applications. • Their direct band gaps also suggest potential for photovoltaics applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Structural, electronic and magnetic properties of chevron-type graphene, BN and BC{sub 2}N nanoribbons

Graphene nanoribbons are predicted to be essential components in future nanoelectronics. The size, edge type, arrangement of atoms and width of nanoribbons drastically change their properties. Boronnitrogencarbon nanoribbons properties are not fully understood so far. In the present contribution it was investigated the structural, electronic and magnetic properties of chevron-type carbon, boron nitride and BC{sub 2}N nanoribbons, using first-principles calculations. The results indicate that the structural stability is closely related to the discrepancies in the bond lengths, which can induce structural deformations and stress. Such nanoribbons present a wide range of electronic behaviors, depending on their composition and particularities of the atomic arrangement. A net magnetic moment is found for structures that present carbon atoms at the nanoribbon borders. Nevertheless, the calculated magnetic moment depends on the peculiarities of the symmetric arrangement of atoms and imbalance of carbon atoms between different sublattices. It was found that all structures which have a significant energy gap do not present magnetic moment, and vice-versa. Such result indicates the strong correlation between the electronic and magnetic properties of the chevron-type nanoribbons. - Highlights: • Small discrepancies between distinct bond lengths can influence the formation energy of the BC{sub 2}N nanoribbons. • The electronic behavior of the BC{sub 2}N chevron-type nanoribbons depends on the atomic arrangement and structural symmetries. • There is a strong correlation between the electronic and magnetic properties for the BC{sub 2}N structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Impact of microstructure on the thermoelectric properties of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}

We present detailed structural and thermoelectric studies of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}. This material is of interest due to previously reported considerable thermopower above room temperature (∼ 100 μV/K) and low thermal conductivity (2 W/(m K)). Here, we present detailed studies concerning microstructural and thermoelectric data, their variation across the samples and possible explanations for the observed behaviour. We have used X-ray diffraction, scanning electron microscopy (SEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) for microstructural analysis. The thermoelectric properties were examined using a physical property measurement system (PPMS). We analyse the impact of the sample quality on the thermoelectric properties. The most unstable parameter is the material resistivity which varies between 1.5 and 15 mΩ cm at room temperature. The properties variability is mainly due to structural defects caused by stresses during material preparation and also due to formation of foreign phases CeCuSb{sub 2} and CeSb. The figure of merit ZT is also strongly dependent on the quality of the sample. The largest value ZT ≈ 0.15 at 400 K is determined for the almost stoichiometric sample with small amounts of a impurity phases. - Highlights: •The Ce{sub 3}Cu{sub 3}Sb{sub 4} has considerable thermoelectric properties and potential for further chemical and/or structural modification. •The control over foreign phases formation is challenging. •The defects arising during arc melting process highly deteriorate ZT of material.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Microstructure, mechanical properties and in vitro degradation behavior of novel Zn-Cu-Fe alloys

Highlights: • Zn-3Cu-xFe (x = 0, 0.5 and 1 wt%) alloys are proposed for the first time as candidate biodegradable materials. • The YS, UTS, and elongation of Zn-3Cu-0.5Fe alloy are 232 MPa, 284 MPa and 33%, respectively. • The in vitro degradation rate in SBF was successfully increased by about 52% by 1 wt% Fe addition for Zn-3Cu. - Abstract: Zn and Zn-based alloys as biodegradable material have drawn more and more attention in recent years due to their good mechanical properties, lower degradation rate than Mg and acceptable biocompatibility. However, too low degradation rate is a challenge for future application of Zn-based alloys. In this study, Zn-3Cu-xFe (x = 0, 0.5 and 1 wt%) alloys were proposed as candidate biodegradable materials. The microstructure, mechanical and in vitro biodegradable properties were investigated systematically. The Zn-3Cu alloy was composed of Zn matrix and CuZn{sub 5} phase, while the FeZn{sub 13} phase was newly formed with the addition of Fe. Due to the micro-galvanic effect produced by FeZn{sub 13} as a cathodic phase to the Zn matrix, in vitro degradation rate in simulated body fluid solution (SBF) was greatly increased by about 52.1%, from 45.3 ± 8.22 for Zn-3Cu alloy to 68.9 ± 7.34 μm/year for Zn-3Cu-1Fe alloy. Although the mechanical properties were decreased slightly due to the introduction of hard and brittle FeZn{sub 13} secondary phase to the Zn matrix, Zn-3Cu-0.5Fe alloy still exhibits good combined mechanical properties and the YS, UTS and elongation are 232 MPa, 284 MPa and 33%, respectively. Taken together, the mechanical properties and in vitro degradation behavior of the Zn-3Cu-xFe alloys are more suitable than Zn-3Cu alloy as candidate biodegradable materials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Modification of microstructure and properties of Ti-47Al-2Cr-4Nb-0.3W alloys fabricated by SPS with trace multilayer graphene addition

Highlights: • The TiAl alloys with different content addition of multilayer graphene were fabricated. • When the graphene content is 0.8 at.%, the mean grain size decreases to 8.2 μm. • The bending and fracture strength increase to 1000 MPa and 2347 MPa, respectively. • The friction coefficient decreased from 0.6 to 0.4, with a decrease by 1/3. - Abstract: In this paper, Ti-47Al-2Cr-4Nb-0.3W alloys with trace multilayer graphene addition were fabricated by spark plasma sintering to enhance both mechanical properties and tribological property simultaneously. With the addition of multilayer graphene, bending strength, compressive strength and tribological property of TiAl alloys are all improved. When graphene content increases from zero to 0.8 at.%, the mean grain size decreases from 14.8 ± 1.4 μm to 8.2 ± 0.8 μm. The bending strength reaches almost 1000 MPa and the fracture strength increases to 2347 ± 12 MPa, an increase of 15% compared with TiAl alloy. The friction coefficient also decreases from about 0.6 to 0.4, a decrease by 1/3 compared with TiAl alloy. The reasons for the improved mechanical properties and tribological property are the in-situ reaction plate-shape Ti{sub 2}AlC phase, fine needle-like Ti{sub 3}AlC phase as well as fine and homogeneous microstructure. The wear mechanism changes from abrasive wear to abrasive wear plus adhesive wear with the increased graphene content.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of aging treatment on microstructures, tensile properties and intergranular corrosion behavior of Al–Cu–Li alloy

Highlights: • T8 duplex aging greatly promoted the precipitation of strengthening phases. • Heavy precipitation of strengthening phases led to enhancing of tensile properties. • Intergranular corrosion sensibility can be reduced by T8 duplex aging greatly. - Abstract: The influence of aging treatment on microstructures, tensile properties and corrosion properties of Al–Cu–Li alloy was investigated. The results show that the T8 duplex aging treatment was more effective than T6 and T8 single aging treatment in enhancing the tensile properties and improving the intergranular corrosion (IGC) resistance. Based on the microstructure observation, tensile test, electrochemical experiment and IGC measurement, the factors which affect the microstructures, tensile properties and IGC behavior changing of Al–Cu–Li alloy during aging treatments were discussed in detail.

36 MATERIALS SCIENCE↗