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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

CREATING TOOLPATHS WITHOUT STARTS AND STOPS FOR EXTRUSION-BASED SYSTEMS

Toolpath generation for extrusion-based additive manufacturing systems, called slicing, involves operations on polygonal contours that are derived from an STL file. Slicing generates multiple paths per layer (both closed-loop and open-loop) that are designed to optimally fill the space outlined by the polygon(s). In the course of printing a layer, the extruder must start and stop, the tip must be wiped, and the extruder must travel between paths without printing. Any amount of time the printer spends moving without printing is considered wasted time because the part isn’t being constructed. In addition, the start/stop point, known as the seam, is often a blemish on the surface of the part that contributes to weaker material properties. Therefore, a single path for creating multi-bead walled structures is desirable because it would save machine time and create parts with better surface finish. This paper will cover one method of modifying the CAD file and slicing engine to allow for parts to be printed without starting and stopping the extruder.

Roschli, Alex↗
DOE OSTI2020

Illuminated outdoor luminescence imaging of photovoltaic modules

The present disclosure relates to a method that includes applying a first condition to a photovoltaic (PV) device, and applying a second condition to the PV device, where the first condition results in a first luminescing of a surface of the PV device at a first intensity, the second condition results in a second luminescing of the surface at a second intensity, measuring the first intensity using a detector to create a first representation of the surface, measuring the second intensity using the detector to create a second representation of the surface, and comparing the first representation with the second representation to create a third representation of the surface that identifies a defect in the surface, if present.

42 ENGINEERING↗
DOE OSTI2015

The fourth decade of underground research at the Grimsel Test Site - what we have learned and where we go from here - 15075

At the Grimsel Test Site, NAGRA and its partners have celebrated thirty years' worth of essential contributions to the characterization of crystalline host rock, and the development and confirmation of safe geological disposal concepts. In operation since 1984, the underground research laboratory in the Swiss Alps shall not accept radioactive waste but can host experiments with radiotracers/radionuclides under strictly controlled conditions. The strong drive for international cooperation at the Grimsel Test Site is reflected in the more than two dozen organizations and research institutes from twelve countries and the European Union which have participated in the research program to date. The program has been designed dynamically to always mirror the current requirements of national programs for the long-term management of radioactive waste, as well as attempt to anticipate the next steps. Early work featured the development of methodologies for formation characterization. Then followed a period concentrating on performance assessment issues, before radionuclide migration and barriers were investigated intensely. The past 15 years have been dominated by engineering demonstration experiments. The research conducted at the Grimsel Test Site has complemented laboratory experiments, surface investigations and numerical modelling studies through the bridging of different scales and drawing off links between laboratory setups and natural analogues. The crystalline rock formations of the Aar Massif have provided an opportunity to do experiments in environments similar to those of future repositories. The facility also serves as a platform for continual knowledge transfer between generations of scientists and fosters synergies among disciplines. However, considering the ambitious schedule for repository implementation in several continuous, one may ask whether the era of generic underground rock laboratories is approaching its end. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Disposal of Greater Than Class C Low-Level Radioactive Waste in Andrews County, Texas - 16408

The U.S. Nuclear Regulatory Commission (NRC) staff has recommended approval of an initiative to permit the Texas Commission on Environmental Quality (TCEQ) to license the disposal of commercial and co-mingled Greater Than Class C Low-Level Radioactive Waste (GTCC LLW) in Andrews County, Texas. Such a framework is clearly articulated in the Section 274 of the Atomic Energy Act of 1954, as amended. The NRC staff also recommended approval to proceed with a rulemaking to align the Waste Classification Tables in Title 10 of the Code of Federal Regulations (CFR), Part 61.55 with the paragraph 61.2 definition of 'waste' to provide a disposal pathway for waste containing certain alpha-emitting transuranic elements with concentrations exceeding 100 nanocuries per gram (nCi/g). A pathway for the disposal of commercial and co-mingled GTCC LLW, including waste with certain alpha emitting transuranic elements exceeding 100 nCi/g (TRU waste), might emerge if the initiative described in the Commissions' July 22, 2015 document, SECY-15-0094, Historical and Current Issues Related to Disposal of GTCC LLW, is approved. The NRC staff recommendations envisioned the NRC and TCEQ working together to review a site-specific performance assessment that would be submitted by Waste Control Specialists LLC (WCS) as part of an amendment to its existing Radioactive Materials License No. R04100. The TCEQ's recommendations were prompted by a petition for rulemaking filed by WCS to allow the disposal of GTCC waste in Texas. On September 10, 2014, the TCEQ Commissioners directed their staff to engage stakeholders and request input from the NRC and the U.S. Department of Energy (DOE) regarding actions needed to proceed with any future rulemaking. On January 30, 2015, the TCEQ requested clarification from the NRC regarding their legal authority and jurisdiction to regulate GTCC, GTCC-like, and TRU waste. The deliberations that have transpired over the past year have raised important legal, policy, and technical matters. This initiative could provide a safe disposal pathway for certain waste streams that have been orphaned over the past 30 years. One important realization that has emerged is the conservative assumptions used to establish the upper limits for Class C LLW when Part 61 was promulgated in 1981 would be much too restrictive when applied to a modern, highly engineered disposal facility located in arid west Texas. Waste that was not suitable for near surface disposal in 1981 could certainly be demonstrated to be safely disposed at the WCS Federal Waste Disposal Facility in Andrews County, Texas. This paper will address the legal, policy, and technical matters supporting this important topic currently under consideration both nationally and within the State of Texas. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

High density and taper-free boron doped Si{sub 1−x}Ge{sub x} nanowire via two-step growth process

The authors study Au catalyzed chemical vapor growth of Si{sub 1−x}Ge{sub x} alloyed nanowires in the presence of diborane, serving as a dopant precursor. Our experiments reveal that introduction of diborane has a significant effect on doping and morphology. Boron exposure poisons the Au catalyst surface, suppresses catalyst activity, and causes significantly tapered wires, as a result of conformal growth. The authors develop here a two-step method to obtain high density and taper-free boron doped Si{sub 1−x}Ge{sub x} alloy nanowires. The two-step process consists of: (1) growth of a small undoped Si{sub 1−x}Ge{sub x} section and (2) introduction of diborane to form a boron doped Si{sub 1−x}Ge{sub x} section. The catalyst preparation step remarkably influences wire yield, quality and morphology. The authors show that dopant-ratio influences wire resistivity and morphology. Resistivity for high boron doped Si{sub 1−x}Ge{sub x} nanowire is 6 mΩ-cm. Four probe measurements show that it is possible to dope Si{sub 1−x}Ge{sub x} alloy nanowires with diborane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Deposit geometry and oxygen concentration spatial variations due to composition change in printed functionally graded components

Functionally graded materials (FGMs) with site specific chemical composition are commonly manufactured by directed energy deposition (DED). Although previous work fabricated an FGM with a compositional variation between a ferritic and austenitic alloy, difficulties arose due to variations in deposit shape with composition change. This problem also occurs for FGMs in literature; however, unlike other cases, the thermophysical properties of these two alloys were similar throughout the build. Here, we investigate the role of chemical composition and surface-active elements on deposit geometry during the manufacture of FGMs by laser DED. Single-track experiments for the relevant FGM compositions are analyzed with results from a well-tested, three-dimensional, transient numerical heat transfer and fluid flow model and thermodynamic calculations. Experiments showed deposit shape varied as a function of composition for constant laser power and scan speed. Thermodynamic analysis indicated that the oxygen solubility in the fusion zone varied significantly for each composition used for the FGM. Numerical modeling revealed that the change in fluid flow caused by Marangoni convection due to dissolved oxygen in the fusion zone were mainly responsible for the changes in deposit shape observed in experiments. Finally, because oxygen can be introduced into the fusion zone through the feedstock as well as the surrounding atmosphere, these findings elucidate a previously unconsidered aspect of process control during DED fabrication of FGMs.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Surface temperature: A key parameter to control the propanethiol plasma polymer chemistry

In this work, the influence of the substrate temperature (T{sub s}) on the chemical composition of propanethiol plasma polymers was investigated for a given set of plasma conditions. In a first study, a decrease in the atomic sulfur content (at. %S) with the deposition time (t{sub d}) was observed. This behavior is explained by the heating of the growing film during deposition process, limiting the incorporation of stable sulfur-based molecules produced in the plasma. Experiments carried out by controlling the substrate temperature support this hypothesis. On the other hand, an empirical law relating the T{sub s} and the at. %S was established. This allows for the formation of gradient layer presenting a heterogeneous chemical composition along the thickness, as determined by depth profile analysis combining X-ray photoelectron spectroscopy and C{sub 60} ion gun sputtering. The experimental data fit with the one predicted from our empiric description. The whole set of our results provide new insights in the relationship between the substrate temperature and the sulfur content in sulfur-based plasma polymers, essential for future developments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electrolytic Plasma Surface Polishing of Complex Components Produced by Selective Laser Melting

The applicability of electrolytic plasma surface polishing to complex components produced by selective laser melting (SLM) is analyzed. By electrolytic plasma polishing by electrolyte spraying, the surface quality of components produced by SLM may be improved. This technology is found to decrease the surface roughness from R{sub a} = 5.6 μm to 1.4 μm. The optimal pressure of the electrolyte jet is 0.02–0.05 MPa. At high pressures, the process becomes unstable. By electrolytic plasma polishing on the basis of electrolyte jets, uniform external and internal surface roughness of components produced by SLM may be ensured.

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

Reflective Fiber Temperature Probe Based on Localized Surface Plasmon Resonance towards Low-Cost and Wireless Interrogation

Reflection fiber temperature sensors functionalized with plasmonic nanocomposite material using intensity-based modulation are demonstrated for the first time. Characteristic temperature optical response of the reflective fiber sensor is experimentally tested using Au-incorporated nanocomposite thin films deposited on the fiber tip, and theoretically validated using a thin-film-optic-based optical waveguide model. By optimizing the Au concentration in a dielectric matrix, Au nanoparticles (NP) exhibit a localized surface plasmon resonance (LSPR) absorption band in a visible wavelength that shows a temperature sensitivity ~0.025%/°C as a result of electron–electron and electron–phonon scattering of Au NP and the surrounding matrix. Detailed optical material properties of the on-fiber sensor film are characterized using scanning electron microscopy (SEM) and focused-ion beam (FIB)-assisted transmission electron microscopy (TEM). Airy’s expression of transmission and reflection using complex optical constants of layered media is used to model the reflective optical waveguide. A low-cost wireless interrogator based on a photodiode transimpedance-amplifier (TIA) circuit with a low-pass filter is designed to integrate with the sensor. The converted analog voltage is wirelessly transmitted via 2.4 GHz Serial Peripheral Interface (SPI) protocols. Feasibility is demonstrated for portable, remotely interrogated next-generation fiber optic temperature sensors with future capability for monitoring additional parameters of interest.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Liquified SO 2 induced solid/cathode electrolyte interphase for lithium ion batteries

Formation of robust solid/cathode electrolyte interphases (S/CEI) is vital for long-term stability and high-performance operation of lithium-ion batteries (LIBs), particularly under high voltage regimes. However, engineering electrochemically stable S/CEIs that effectively suppress interfacial side reactions remains a key challenge. Herein, we introduce a liquefied sulfur dioxide (SO 2 )– ionic liquid complex as a fluorine-free multifunctional electrolyte additive for the first time that significantly improves the formation of sulfate/sulfite-rich S/CEI layers at both graphite and NMC811 interfaces. The unique SO 2 -N coordination with a 1,2,4-triazolide-based ionic liquid enables homogeneous SO 2 dissolution, resulting in controlled SO 2 decomposition during the initial electrochemical cycle. This decomposition yields sulfur-rich interphase species that stabilize the electrolyte-electrode interface, reduce impedance growth, and lessen electrolyte decomposition. Electrochemical tests show significantly improved cycle life, reduced polarization, and increased Coulombic efficiency for both anodes and cathodes. XPS confirms the presence of SO 2 -derived surface species that contribute to interfacial stability. In conclusion, this approach highlights a new direction for interphase engineering using liquefied gas additives and opens pathways for sulfur-based S/CEI chemistry in advanced battery systems.

Graphite↗
DOE OSTI2025

Rotation of electrothermal-instability-driven overheating structure due to helically oriented surface magnetic field on a high-current-density aluminum rod

Experiments on the 1-MA, 100-ns-rise-time Mykonos Facility demonstrate rotation of electrothermal instability (ETI)-driven overheating structure on 1.00-mm-diameter, 10-nm-surface roughness, 99.999%-pure aluminum rods, which are pulsed with helically polarized surface magnetic field. Rods are machined to include pairs of 10-micron-scale quasi-hemispherical voids or “engineered defects (ED)” which provide the dominant current density perturbation from which ETI grows most rapidly. Experiments include an axial magnetic field component through the addition of a helically wound return-current electrode or “helical return can (HRC).” For a given HRC design, azimuthal field (B ɵ ) and axial field (B z ) components rise at a prescribed and fixed ratio, driving an increasing magnetic field of constant polarization at the rod's surface; most experiments generated surface magnetic field at a 15-degree field polarization angle (from horizontal) defined as ɸ B = arctan(B z /B ɵ ). ETI-driven emission patterns from individual ED are observed to rotate along ɸ B , while emission patterns from dielectric-coated ED pairs are shown to elongate and preferentially merge along ɸ B , in qualitative agreement with 3D-magnetohydrodynamic simulations. These data strongly support that for a randomized distribution of current density perturbations on a high-current density conductor, nearby perturbations will favorably merge about ɸ B , with the degree of merging increasing with current. Such observations offer fundamental new understanding of the seeding mechanisms of the helical magneto-Rayleigh Taylor (MRT) instabilities observed from axially magnetized magnetically driven imploding liners.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Defect engineering in atomically-thin bismuth oxychloride towards photocatalytic oxygen evolution

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds, defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. As a result, this successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Combined wet and dry cleaning of SiGe(001)

Combined wet and dry cleaning via hydrofluoric acid (HF) and atomic hydrogen on Si{sub 0.6}Ge{sub 0.4}(001) surface was studied at the atomic level using ultrahigh vacuum scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy to understand the chemical transformations of the surface. Aqueous HF removes native oxide, but residual carbon and oxygen are still observed on Si{sub 0.6}Ge{sub 0.4}(001) due to hydrocarbon contamination from post HF exposure to ambient. The oxygen contamination can be eliminated by shielding the sample from ambient via covering the sample in the HF cleaning solution until the sample is introduced to the vacuum chamber or by transferring the sample in an inert environment; however, both processes still leave carbon contaminant. Dry in-situ atomic hydrogen cleaning above 330 °C removes the carbon contamination on the surface consistent with a thermally activated atomic hydrogen reaction with surface hydrocarbon. A postdeposition anneal at 550 °C induces formation of an atomically flat and ordered SiGe surface observed by STM. STS verifies that the wet and dry cleaned surface has an unpinned Fermi level with no states between the conduction and valence band edge comparable to sputter cleaned SiGe surfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2017

PPPL ST-FNSF Engineering Design Details

One of the goals of the PPPL Spherical Tokamak (ST) Fusion Nuclear Science Facility (FNSF) study was to generate a self-consistent conceptual design of an STFNSF device with sufficient physics and engineering details to evaluate the advantages and disadvantages of different designs and to assess various ST-FNSF missions. This included striving to achieve tritium self-sufficiency; the ability to provide shielding protection of vital components and to develop maintenance strategies that could be used to maintain the in-vessel components (divertors, breeding blankets, shield modules and services) and characterize design upgrade potentials to expanded mission evolutions. With the conceptual design of a 2.2 m ST pilot plant design already completed emphasis was placed on evaluating a range of ST machine sizes looking at a major radius of 1m and a mid-range device size between 1 m and 2.2 m. This paper will present an engineering summary of the design details developed from this study, expanding on earlier progress reports presented at earlier conferences that focused on a mid-size 1.7 m device. Further development has been made by physics in defining a Super-X divertor arrangement that provides an expanded divertor surface area and places all PF coils outside the TF coil inner bore, in regions that improve the device maintenance characteristics. Physics, engineering design and neutronics analysis for both the 1.7 m and 1 m device have been enhanced. In conclusion, the engineering results of the PPPL ST-FNSF study will be presented along with comments on possible future directions.

42 ENGINEERING↗
DOE OSTI2023

Neutral Silicon Vacancy Centers in Undoped Diamond via Surface Control

Neutral silicon vacancy centers (SiV 0 ) in diamond are promising candidates for quantum applications; however, stabilizing SiV 0 requires high-purity, boron-doped diamond, which is not a readily available material. Here, we demonstrate an alternative approach via chemical control of the diamond surface. We use low-damage chemical processing and annealing in a hydrogen environment to realize reversible and highly stable charge state tuning in undoped diamond. The resulting SiV 0 centers display optically detected magnetic resonance and bulklike optical properties. Controlling the charge state tuning via surface termination offers a route for scalable technologies based on SiV 0 centers, as well as charge state engineering of other defects.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

Surface Energy Modulated Self‐Assembly of Percolative Gallium Nanodroplet Films for Stretchable Electronics

Advancements in soft robotics and wearable technologies have led to an increased need for flexible and stretchable electronic systems. Liquid metals like Gallium (Ga) and its alloys offer high potential in the field of stretchable electronics and photonics due to their inherent high conductivity and malleability. However, their high surface tension and native oxide formation hinder uniform wetting and continuous film formation to get conducting films. Here, we report a fabrication strategy to realize electrically conductive Ga thin films with effective thicknesses around 100 nm on polymeric and elastomeric substrates. By enhancing the surface energy of the elastomer, we create uniform Ga nanodroplets capable of sustaining stretchability up to 200% strain. Our devices exhibit electronic conduction primarily through tunneling and display strain tunable piezoresistive characteristics, which are explained using Kirchhoff's resistive network and Simmon's analytical tunneling current model. To showcase the device's capability in fields of stretchable electronics, we demonstrate several functional prototypes, including flexible devices integrated with Light Emitting Diodes (LEDs), curvature and pressure sensors, and soft robotic grippers capable of sensing object curvature. The demonstrated devices highlight the potential of this approach for scalable integration of stretchable electronics in soft robotic and wearable platforms.

42 ENGINEERING↗
DOE OSTI2022

Optical Imaging for Understanding of Thermal Barrier Coated Piston Engine Performance

Thermal barrier coatings (TBC) applied to pistons have been a recently renewed research topic in the field of internal combustion engines. Single cylinder testing of a conventional C15™ Tier 4 final pro-duction steel piston and a TBC coated piston showed that the Yttrium stabilized Zirconia (YSZ) TBC did not significantly alter engine performance, with the TBC piston having slower combustion rates and higher criteria emissions. For deeper understanding, research continued by studying 3D-piston sections optically in a constant pressure vessel using photodiodes, four high-speed cameras (natural luminosity, CH*, and OH*), and visualization of the flame from two orthogonal directions. Particle Im-aging Velocimetry (PIV) algorithms were adapted to perform Combustion Imaging Velocimetry (CIV) to aid in quantification of the observed visual combustion flow field differences. The optical work showed that the TBC piston flame development is slower, spatially different, with lower mixing energy for the TBC variant. Geometric profiles of engine pistons and optical vessel 3D-piston sections were measured using a Coordinate Measurement Machine (CMM), and surface roughness was measured with a stylus surface profilometer. CMM results showed that the TBC piston bowl had reasonable macroscopic accuracy, but the rim had a larger radius with less reentrancy. A discussion of the results and analyses in relation to future TBC effort and direction concludes the work.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2026

A machine learning pipeline for identifying infiltration managed aquifer recharge locations from satellite imagery in the San Joaquin Valley, California

This study focuses on an agricultural region in California’s Central Valley, USA, where Managed Aquifer Recharge (MAR) is widely implemented to mitigate groundwater depletion under increasing water demand and climate variability. A deep learning and machine learning framework was developed to identify infiltration-MAR locations using satellite imagery and environmental data. The framework integrates surface water detection from Sentinel-2 imagery, geospatial delineation of water bodies, spatiotemporal tracking of water body dynamics, and supervised classification using meteorological, environmental, and topographic variables. The framework was applied to a 2379 km² study area southwest of Fresno, where 765 water bodies were detected, including 139 identified MAR sites based on publicly available datasets and expert knowledge. The classification model achieved an accuracy of 0.94 and an F1 score of 0.85. Feature importance analysis indicates that cropland, normalized difference vegetation index (NDVI), and evaporation are among the most influential predictors for infiltration-MAR. Notably, the framework suggests that engineered water management in infiltration-MAR systems can disrupt or even reverse the expected positive correlation between surface water extent and precipitation. These findings provide physically interpretable insights into the characteristics of existing infiltration-MAR facilities and demonstrate the potential of the proposed framework as a reproducible, interpretable, and potentially transferable tool for data-driven infiltration-MAR identification and inventory development under growing climatic and hydrological uncertainty.

Classification↗