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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Lithiation Induced Phases in 1T'-MoTe 2 Nanoflakes

Multiple polytypes of MoTe 2 with distinct structures and intriguing electronic properties can be accessed by various physical and chemical approaches. Here, in this study, we report electrochemical lithium (Li) intercalation into 1T'-MoTe 2 nanoflakes, leading to the discovery of two previously unreported lithiated phases. Distinguished by their structural differences from the pristine 1T' phase, these distinct phases were characterized using in situ polarization Raman spectroscopy and in situ single-crystal X-ray diffraction. The lithiated phases exhibit increasing resistivity with decreasing temperature, and their carrier densities are two to 4 orders of magnitude smaller than the metallic 1T' phase, as probed through in situ Hall measurements. The discovery of these gapped phases in initially metallic 1T'-MoTe 2 underscores electrochemical intercalation as a potent tool for tuning the phase stability and electron density in two-dimensional (2D) materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Benchmarking large language models for materials synthesis: The case of atomic layer deposition

In this work, we introduce an open-ended question benchmark, ALDbench, to evaluate the performance of large language models (LLMs) in materials synthesis, and, in particular, in the field of atomic layer deposition, a thin film growth technique used in energy applications and microelectronics. Our benchmark comprises questions with a level of difficulty ranging from the graduate level to domain expert current with the state of the art in the field. Human experts reviewed the questions along the criteria of difficulty and specificity, and the model responses along four different criteria: overall quality, specificity, relevance, and accuracy. We ran this benchmark on an instance of OpenAI’s GPT-4o. The responses from the model received a composite quality score of 3.7 on a 1–5 scale, consistent with a passing grade. However, 36% of the questions received at least one below average score. An in-depth analysis of the responses identified at least five instances of suspected hallucination. Finally, we observed statistically significant correlations between the difficulty of the question and the quality of the response, the difficulty of the question and the relevance of the response, the specificity of the question, and the accuracy of the response as graded by the human experts. Furthermore, this emphasizes the need to evaluate LLMs across multiple criteria beyond difficulty or accuracy.

Artificial intelligence↗
DOE OSTI2024

Synthesis of Three Isoelemental MXenes and Their Structure–Property Relationships

The MXene family has rapidly expanded since its discovery in 2011 to include nearly 50 unique MXenes, not accounting for solid solutions and diverse surface terminations. However, a question raised since their discovery has been: What is the effect of n? In other words, how does the number of layers affect the MXene properties? To date, no direct study of the impact of n has been conducted due to the lack of isoelemental MXene compositions spanning more than two n values. Herein, we report on a system of three MXenes with identical M-site chemistries, (Mo 2/3 V 1/3 ) n+1 C n T x (n = 1, 2, and 3), allowing for the study of MXene structure–property relationships across n, for the first time. Chemical analysis of the samples shows complete and partial ordering of the M-elements in the n = 2 and 3 samples, respectively. We show that sample stability gradually evolves as n is increased from 1 to 3, while electronic and electrochemical properties exhibit more significant changes in going from n = 1 to 2 than from n = 2 to 3.

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

Understanding and tuning magnetism in van der Waals-type metal thiophosphates

Over the past two decades, significant progress in two-dimensional (2D) materials has invigorated research in condensed matter and material physics in low dimensions. While traditionally studied in three-dimensional systems, magnetism has now been extended to the 2D realm. Recent breakthroughs in 2D magnetism have attracted substantial interest from the scientific community, owing to the stable magnetic order achievable in atomically thin layers of the van der Waals (vdW)-type layered magnetic materials. These advances offer an exciting platform for investigating related phenomena in low dimensions and hold promise for spintronic applications. Consequently, vdW magnetic materials with tunable magnetism have attracted significant attention. Specifically, antiferromagnetic metal thiophosphates MPX 3 (M = transition metal, P = phosphorus, X = chalcogen) have been investigated extensively. These materials exhibit long-range magnetic order spanning from bulk to the 2D limit. The magnetism in MPX 3 arises from localized moments associated with transition metal ions, making it tunable via substitutions and intercalations. In this review, we focus on such tuning by providing a comprehensive summary of various metal- and chalcogen-substitution and intercalation studies, along with the mechanism of magnetism modulation, and a perspective on the development of this emergent material family.

42 ENGINEERING↗
DOE OSTI2025

Interlayer pillaring influences the octahedral tilting and electrochemical capacity of tungsten oxides

One strategy to tune the electrochemical properties of layered inorganic materials for energy storage and conversion is to introduce molecular organic pillars. We investigated how pillaring tungsten oxides with alkylammonium cations influences their physical and electrochemical properties relative to the non-pillared host. While the presence of alkylammonium increased the interlayer spacing, we found that the electrochemical capacity of the materials decreased in non-aqueous electrolytes. In aqueous acidic electrolytes, replacement of the interlayer alkylammonium pillars with water molecules led to the recovery of the electrochemical capacity. We rationalize these results based on the influence of interlayer pillars on the degree of octahedral tilting within the inorganic tungsten oxide layers. The presence of alkylammonium in the interlayer leads to an increase in octahedral tilting relative to interlayer water. In turn, this leads to an increase in the band gap and corresponding decrease in the electrochemical capacity. Our findings emphasize the correlation between the chemical nature of the interlayer molecular pillars and the electronic structure, which in turn affects the electrochemical capacity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Role of stacking defects on the magnetic behavior of CrCl 3

Here, in the study of van der Waals–layered magnetic materials, the properties of CrCl 3 continue to attract attention. This compound is reported to undergo antiferromagnetic ordering below ~14 K, with a ferromagneticlike region proposed to exist between 14 and 17 K. Ideally, the crystal structure is rhombohedral (R) below ~235 K, separated from a higher-temperature monoclinic (M) phase by a layer-sliding structural phase transition. However, the structural transition is often inhibited even in bulk single crystals, allowing M-type layer stacking, reported to have a 10-fold greater interlayer magnetic coupling than R-type stacking, to be present at low temperature. To clarify the effect of stacking defects on CrCl 3 , we report magnetization measurements on samples of varying crystalline quality. At low applied magnetic field, some crystals predominantly show the T N = 14 K peak, but other crystals show hysteretic behavior and a magnetization enhancement at a slightly higher temperature (14 < T ≲ 17 K.) Samples with anomalous behavior exhibit a transition around ~2 T in isothermal magnetization-field data, evidence that M-type stacking defects are the source of these anomalies. Ground powder samples are especially likely to show strongly anomalous behavior. We suggest that the anomalous behavior arises from few-layer magnetic domains that form just above T N in an environment of mixed interlayer magnetic coupling strength. We argue that the influence of M-type stacking boundaries on sublattice magnetization is already observable in reported neutron scattering data, and may be responsible for an enhancement near 17 K in reported specific heat data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Three-dimensional dispersion in the type-II Dirac semimetals PtTe 2 and PdTe 2 revealed through circular dichroism in angle-resolved photoemission spectroscopy

PtTe 2 and PdTe 2 are among the first transition metal dichalcogenides that were predicted to host type-II Dirac fermions, exotic particles prohibited in free space. These materials are layered and air stable, which makes them top candidates for technological applications that take advantage of their anisotropic magnetotransport properties. Here, in this work, we provide a detailed characterization of the electronic structure of PtTe 2 and PdTe 2 using angle-resolved photoemission spectroscopy (ARPES) and density functional theory calculations, offering an alternative interpretation for one of the Dirac-like dispersions in these materials. Through the use of circularly polarized light, we report a different behavior of such dispersion in PdTe 2 compared to PtTe 2 , that we relate to a symmetry analysis of the dipole matrix element. Such analysis reveals a link between the observed circular dichroism and the different momentum-dependent terms in the dispersion of these two compounds, despite their close similarity in crystal structure. Additionally, our data show a clear difference in the circular dichroic signal for the type-II Dirac cones characteristic of these materials, compared to their topologically protected surface states. Our paper provides a useful reference for the ARPES characterization of other transition metal dichalcogenides with topological properties and illustrates the use of circular dichroism as a guide to identify the topological character and attributes of two otherwise equivalent band dispersions.

angle-resolved photoemission spectroscopy↗
DOE OSTI2025

Intrinsic Layer-Dependent Surface Energy and Exfoliation Energy of van der Waals Materials

Stacking and twisting 2D van der Waals (vdW) layers have become versatile platforms to tune the electron correlation. These platforms rely on exfoliating vdW materials down to a single vdW layer and a few vdW layers. We calculate the intrinsic layer-dependent surface and exfoliation energies of typical vdW materials such as graphite, h-BN, black P, MX 2 (M = Mo or W; X = S, Se, or Te), MX (M = Ga or In; X = S, Se, or Te), Bi 2 Te 3 , and MnBi 2 Te 4 using density functional theory. For exchange-correlation functionals with explicit vdW interaction, a single vdW layer always has the smallest surface energy, giving a surface energy reduction when compared to that of thicker vdW layers. Furthermore, the magnitude of this surface energy reduction quickly decreases with an increase in the number of atomic layers inside the single vdW layer for different vdW materials. Such atomic-layer dependence in surface energy reduction helps explain the different effectiveness of exfoliation for different vdW materials down to a single vdW layer.

Anode materials↗
DOE OSTI2025

An epitaxial surface heterostructure anchoring approach for high-performance Ni-rich layered cathodes

Nickel-rich (Ni≥90%) layered oxides materials have emerged as a promising candidate for next-generation high-energy-density lithium-ion batteries (LIBs). However, their widespread application is hindered by structural fatigue and lattice oxygen loss. In this work, an epitaxial surface rock-salt nanolayer is successfully developed on the LiNi 0.9 Co 0.1 O 2 sub-surface via heteroatom anchoring utilizing high-valence element molybdenum modification. This in-situ formed conformal buffer phase with a thickness of 1.2nm effectively suppresses the continuous interphase side-reactions, and thus maintains the excellent structure integrity at high voltage. Furthermore, theoretical calculations indicate that the lattice oxygen reversibility in the anion framework of the optimized sample is obviously enhanced due to the higher content of O 2p states near the Fermi level than that of the pristine one. Meanwhile, the stronger Mo–O bond further reduces cell volume alteration, which improves the bulk structure stability of modified materials. Besides, the detailed charge compensation mechanism suggests that the average oxidation state of Ni is reduced, which induces more active Li + participating in the redox reactions, boosting the cell energy density. As a result, the uniquely designed cathode materials exhibit an extraordinary discharge capacity of 245.4 mAh g −1 at 0.1 C, remarkable rate performance of 169.3 mAh g −1 at 10 C at 4.5V, and a high capacity retention of 70.5% after 1000 cycles in full cells at a high cut-off voltage of 4.4V. Further, this strategy provides an valuable insight into constructing distinctive heterostructure on high-performance Ni-rich layered cathodes for LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Absorbing boundary conditions in material point method adopting perfectly matched layer theory

This study focuses on solving the numerical challenges of imposing absorbing boundary conditions for dynamic simulations in the material point method (MPM). To attenuate elastic waves leaving the computational domain, the current work integrates the Perfectly Matched Layer (PML) theory into the implicit MPM framework. The proposed approach introduces absorbing particles surrounding the computational domain that efficiently absorb outgoing waves and reduce reflections, allowing for accurate modeling of wave propagation and its further impact on geotechnical slope stability analysis. The study also includes several benchmark tests to validate the effectiveness of the proposed method, such as several types of impulse loading and symmetric and asymmetric base shaking. The conducted numerical tests also demonstrate the ability to handle large deformation problems, including the failure of elasto-plastic soils under gravity and dynamic excitations. The findings extend the capability of MPM in simulating continuous analysis of earthquake-induced landslides, from shaking to failure.

58 GEOSCIENCES↗
DOE OSTI2024

A Pyrrole Modified 3,4‐Propylenedioxythiophene Conjugated Polymer as Hole Transport Layer for Efficient and Stable Perovskite Solar Cells

Despite the outstanding electric properties and cost-effectiveness of poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives, their performance as hole transport layer (HTL) materials in conventional perovskite solar cells (PSCs) has lagged behind that of widely used spirobifluorene-based molecules or poly(triaryl amine). This gap is mainly from their poor solubility and energy alignment mismatch. In this work, the design and synthesis of a pyrrole-modified HTL (PPr) based on 3,4-propylenedioxythiophene (ProDOT) are presented for efficient and stable PSCs. As a result of the superior defects passivation ability, excellent contact with perovskite, enhanced hole extraction, and high hydrophobicity, the unencapsulated PPr-based PSCs showed the peak PCE of 21.49% and outstanding moisture stability (over 4000 h). This work highlights the potential application of ProDOT-based materials as HTL for PSCs and underscores the importance of the rational design of PEDOT and its derivatives.

14 SOLAR ENERGY↗
DOE OSTI2026

Discovery of a new phase transition and high-valent redox mechanism in Fe-substituted Na 2 Mn 3 O 7

Sodium-ion batteries are a promising lower-cost alternative to lithium-ion batteries, but further improvements in electrochemical performance are required. One strategy to increase capacity is to enable reversible high-valent cationic and anionic redox in layered cathode materials; however, this is typically accompanied by structural degradation. Here, in this study, we elucidate the mechanism by which Fe-doped Na 2 Mn 3 O 7 , featuring ordered transition metal-vacancies, achieves reversible high-valent redox. Using Mössbauer spectroscopy, soft X-ray absorption spectroscopy (XAS), and in-situ hard XAS, we demonstrate reversible high-valent cationic redox involving both Fe and Mn while in-situ Raman confirms the absence of local structural degradation associated with oxygen redox. Combining in-situ X-ray diffraction with theoretical calculations, we further identify a previously unreported global phase transition from the $\bar{P1}$ to the $P2_1/c$ space group during electrochemical cycling and develop a physical model describing this structural evolution. These results provide insights for structurally stable layered sodium transition metal oxide cathodes with reversible high-valent redox.

36 MATERIALS SCIENCE↗
DOE OSTI2025

MXene-Derived Potassium-Preintercalated Bilayered Vanadium Oxide Nanostructures for Cathodes in Nonaqueous K-Ion Batteries

Bilayered vanadium oxides (BVOs) are promising cathode materials for beyond-Li-ion batteries due to their tunable chemistries and high theoretical capacities. However, the large size of beyond-Li + ions limits electrochemical cycling and rate capability of BVO electrodes. Recent reports of MXene-derived BVOs with nanoscale flower-like morphology have shown improved electrochemical stability at high rates up to 5C in nonaqueous lithium-ion batteries. Here, we report how morphological stabilization can lead to improved rate capability in potassium-ion batteries (PIBs) through the synthesis and electrochemical characterization of MXene-derived K-preintercalated BVOs (MD-KVOs), which were derived from two V 2 CT x precursor materials prepared using two different etching protocols. We show that the etching conditions affect the surface chemistry of the MXene, which plays a role in the MXene-to-oxide transformation process. MXene derived from a milder etchant transformed into a nanoflower MD-KVO with two-dimensional (2D) nanosheet petals (KVO-DMAE) while a more aggressive etchant produced a MXene that transformed into a MD-KVO with one-dimensional (1D) nanorod morphology (KVO-CMAE). Electrochemical cycling of the produced MD-KVOs after drying at 200 °C under vacuum (KVO-DMAE-200 and KVO-CMAE-200) in PIBs showed that electrochemical stability of MD-KVO at high rates improved through the morphological stabilization of 2D particles combined with the control of interlayer water and K + ion content. Structure refinement of KVO-DMAE-200 further corroborates the behavior observed during K + ion cycling, connecting structural and compositional characteristics to the improved rate capability. This work demonstrates how proper synthetic methodology can cause downstream effects in the control of structure, chemical composition, and morphology of nanostructured layered oxide materials, which is necessary for development of future materials for beyond-Li-ion battery technologies.

25 ENERGY STORAGE↗
DOE OSTI2025

PV backsheets survey protocol: A framework for geo-spatial field surveys for bulk material characterization and reliability analysis applied across 41 PV systems

As widespread adoption of photovoltaic (PV) technologies continues, understanding the lifetime of modules is paramount to the viability of the industry as an environmentally conscious alternative to traditional energy generation. Although power degradation can affect the total energy production of a module over its lifetime, module safety failures necessitate the removal of a module leading to a loss of not only the particular asset, but the earning potential of the device. Therefore, it is critical to ensure that the components that provide essential safety functions for PV module operate for their entire rated lifetime. PV backsheets provide necessary electrical insulation to the completed device and failure of this component is cause for a immediate removal of the module. Degradation of the PV module backsheet has led to module safety failures in large-scale installations, costing millions of dollars in damages and lost potential revenue. The spatio-temporal degradation of fielded PV modules is important to study in order to identify which modules within installations are experiencing the greatest exposure conditions and in turn have the highest chance of failure. This paper describes a comprehensive field survey protocol developed for monitoring PV module backsheet performance using solely non-destructive methods in commercial PV fields. The protocol establishes a field naming convention, sampling method, data handling requirements, and measurement procedures. By ensuring consistent data collection practices, the field survey protocol enables research groups to obtain data of uniform quality on backsheet performance over multiple years and locations. In this study, the developed protocol was implemented at forty-one PV sites. Eight different types of airside layer backsheet materials including poly(vinylidene fluoride) (PVDF), acrylic PVDF, poly(tetrafluoroethylene-co-hexafluoropropylene-co-vinylidene fluoride) (THV), poly(vinyl fluoride) (PVF), poly(ethylene terephthalate) (PET), fluoroethylene vinyl ether (FEVE), polyethylene naphthalate (PEN), and glass were identified using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The field survey results show that the spatial distribution of degradation indicators are non-uniform within a particular module, individual site, and across site locations. The degradation of PV modules increased in severity for modules mounted at the edge of rows (across a field) and near the junction box (within a module). This study demonstrates the sensitivity of material performance to exposure length across different materials and climates.

14 SOLAR ENERGY↗
DOE OSTI2024

Literature Review of Recycling Polypropylene and Polyamide 12 Powders for Selective Laser Sintering

Additive manufacturing (AM) is the creation of three-dimensional parts by adding material layer-by-layer based on two dimensional “slices” of a CAD file, without molds or tooling. AM has broken the relationship between part complexity and manufacturing cost. As a general rule, for conventional manufacturing, the more complex the part produced, the more costly its manufacturing. For example, in the production of a bracket for a satellite, moving from conventional manufacturing to AM allowed the part to be consolidated from 4 parts to just one, as well as reducing the weight of the part by 35%. A further benefit, AM can be more cost effective for small lot sizes. To illustrate, consider a case study of white board marker caps presented by Klahn et al. The cost to produce 1,000 units of a new design using SLS was about an order of magnitude lower than conventional manufacturing, as shown in Figure 1.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Structure, Bonding, and Vibrational Dynamics of a Triamine High Energy Density Material under Pressure

High energy density materials have complex intermolecular interactions which influence their stability and performance. We used a combination of synchrotron X-ray diffraction, synchrotron infrared spectroscopy, and Raman vibrational spectroscopy, supplemented by density functional theory calculations, to probe pressure-induced changes in structure and intermolecular interactions of 1H,4'H-[3,3'-bis(1,2,4-triazole)]-4',5,5'-triamine as a model high energy density material up to 40 GPa. We find that compression of the triamine is accompanied by increased intermolecular interactions that give rise to an interesting evolution of the structure and bonding with pressure. Analysis of the equation of state determined from the X-ray diffraction indicates a change in compression mechanism near 19 GPa consistent with changes in vibrational spectra that provide evidence for a structural rearrangement associated with changes in hydrogen bonding near that pressure. As a result, the overall compressional behavior calculated theoretically agrees with that observed experimentally though differences are found that indicate the need for improved treatment of the intermolecular interactions including hydrogen bonding under pressure.

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

Thermal images collected during large-scale 3D printing with Ingersoll MasterPrint

This data set contains images produced to test the performance of anomaly and fault detection methods in the context of additive manufacturing. Two print jobs were executed using the Ingersoll MasterPrint with the Model 30 Strangpresse extruder. The material used was Techmer compounded polylactic acid (PLA) with wood flour as a filler (80/20 PLA/WF by weight). The first print job consists of the 3D printing of a hexagonal cylinder with a two-bead wall. This print was sliced at a gantry velocity of 3000 millimeter per minute, and an extruder screw speed of 68.14 rotations per minute. This are considered the normal operating conditions. A second hexagonal cylinder was printed using a reduced extruder screw speed, 15% lower than under normal operating conditions. The images were collected with a Teledyne FLIR Lepton 3.5 infra-red camera, a small form factor radiometric long-wave infrared camera with a spectral range of 8 µm to 14 µm. Sensor resolution was 160x120 pixels, with a pixel size of 12 µm, a temperature range of -10 - 450°C, and an accuracy of +/- 10°C in its low gain configuration. Images in this data set were collected with cameras oriented at the printer nozzle. The nozzle camera setup consisted of two cameras located 12.5cm from the nozzle center. These were mounted directly to the print head, so that the camera positions relative to the print direction would remain constant as it rotated around its C-axis to follow the print path. One camera was placed ahead of the nozzle to capture the previous layer immediately before being covered by the new layer of material, while the second camera was placed behind the nozzle and captured the freshly extruded bead. Images are collecting during each phase of the print: (a) idle (i.e., no material deposited), (b) extrusion (i.e., to prime the extruder), and (c) printing (deposition of material to manufacture the hexagonal cylinder).

36 MATERIALS SCIENCE↗
DOE OSTI2025

MechBERT: Language Models for Extracting Chemical and Property Relationships about Mechanical Stress and Strain

Language models are transforming materials-aware naturallanguage processing by enabling the extraction of dynamic, context-rich information from unstructured text, thus, moving beyond the limitations of traditional information-extraction methods. Moreover, small language models are on the rise because some of them can perform better than large language models (LLMs) when given domain-specific questionanswer tasks, especially about an application area that relies on a highly specialized vernacular, such as materials science. We therefore present a new class of MechBERT language models for understanding mechanical stress and strain in materials. These employ Bidirectional Encoder Representations for transformer (BERT) architectures. We showcase four MechBERT models, all of which were pretrained on a corpus of documents that are textually rich in chemicals and their stress–strain properties and were fine-tuned on question-answering tasks. We evaluated the level of performance of our models on domain-specific as well as general English-language question-answer tasks and also explored the influence of the size and type of BERT architectures on model performance. We find that our MechBERT models outperform BERT-based models of the same size and maintain relevancy better than much larger BERT-based models when tasked with domain-specific question-answering tasks within the stress–strain engineering sector. These small language models also enable much faster processing and require a much smaller fraction of data to pretrain them, affording them greater operational efficiency and energy sustainability than LLMs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗