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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

One-Step Radical-Induced Synthesis of Graft Copolymers for Effective Compatibilization of Polyethylene and Polypropylene

The synthesis of copolymers from high-density polyethylene (HDPE) and isotactic polypropylene (iPP) has gained increasing attention due to their ability to improve the recycling of incompatible mixed polyolefin waste feed streams. Herein, we report a new radical grafting process that yields HDPE-g-iPP copolymers from HDPE and iPP by using a commercially available peroxide. Tensile testing of brittle 70/30 HDPE/iPP mixtures with these graft copolymers added showed promising compatibilization, improving the elongation at break of the blends from 20% up to 1080%. Detailed kinetic studies coupled with thermal and rheological characterization revealed optimized conditions for HDPE and iPP macroradical coupling and a deeper understanding of the grafting reaction. This optimization yielded HDPE-g-iPP copolymers that compatibilize HDPE and iPP blends at loadings as low as 2.5 wt %. In conclusion, the versatility of this macroradical grafting reaction was demonstrated by preparing an effective compatibilizer from untreated postconsumer waste plastics.

compatibilization↗
DOE OSTI2026

Ionic-content-driven restructuring of spirobisindane ionene networks: implications for mechanics, self-healing, and gas transport

Polymers of intrinsic microporosity (PIMs) offer exceptional gas permeability but remain brittle and susceptible to physical aging, limiting their durability in separation applications. Here, we introduce a reconfigurable microporous polymer network that uniquely integrates permanent PIM microporosity with autonomous, intrinsic self-healing driven by imidazolium-based ionic motifs. Spirobisindane units generate the intrinsic free-volume architecture, while an imidazolium-containing polyamide ionene supplies dynamic ionic and hydrogen-bonding interactions that reorganize under mild activation. Incorporation of imidazolium-based ionic liquids further tunes cohesion, mobility, and densification, enabling the network to relax, re-associate, and retain microporosity without structural collapse. Through a comprehensive multiscale approach combining spectroscopy, scattering, thermal and mechanical characterization with all-atom molecular dynamics and density functional theory calculations, we elucidate how ionic content, as a single control parameter that reshapes free-volume distributions, modulates local coordination environments, and governs relaxation and healing kinetics. At intermediate ionic loadings, the networks achieve rapid, repeatable self-healing while maintaining CO$_2$ selectivity, demonstrating an optimal balance between segmental mobility and structural integrity. By establishing how hierarchical ionic interactions couple structure, dynamics, and transport in microporous ionene networks, this work provides generalizable design rules for adaptive soft-matter systems that require simultaneous mechanical resilience, reconfigurability, and selective gas transport.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Surface Temperature Effect on Convective Heat Transfer Coefficients for Jet Impingement Cooling of Electric Machines with Automatic Transmission Fluid: Preprint

In this study, the results of NREL's continued work on experimental characterization of the thermal performance of free-surface jets of automatic transmission fluid impinged on a heated target surface are presented. The measured heat transfer coefficients are useful for understanding factors influencing performance of driveline fluid-based cooling systems for electric machines and help designers in developing high-performance, power-dense and reliable machines. Experiments were carried out for different fluid and target surface temperatures (50 degrees C, 70 degrees C, and 90 degrees C for the fluid and 90 degrees C, 100 degrees C, 110 degrees C, and 120 degrees C for the target surface). Impinging jet velocities (0.5 m/s to 7.5 m/s) and the jet position on the target surface (center versus edge) were also varied. The impinging angle was kept at 90 degrees relative to the target surface. It was found that higher target surface temperature increased heat transfer coefficients, namely, increasing surface temperature from 90 degrees C to 120 degrees C enhanced heat transfer coefficient values at higher impinged jet velocities (7.5 m/s) by up to 15%.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2021

Ultrafast visualization of phase transitions in nonequilibrium warm dense matter

Intense ultrafast laser excitation brings materials into highly nonequilibrium states with complex solid–liquid phase transitions. These ultrafast processes yield warm dense matter (WDM) conditions characterized by comparable thermal and Fermi energies, and strong ion–ion coupling. Here, we review recent studies employing mega-electron-volt ultrafast electron diffraction to resolve the structural dynamics of nonequilibrium WDM created by femtosecond laser heating of solids. Furthermore, for the study of warm dense gold, the results showed homogeneous melting that occurs within tens of picoseconds at absorbed energy densities of 0.4–1.4 MJ/kg. These results constrained the electron–ion coupling rate and revealed the melting sensitivity to nucleation seeds. For the study of radiation-damaged tungsten, the results showed a melting transition below the melting temperature. Molecular dynamics simulations suggested that this melting behavior is driven by vacancy defect clusters from radiation damage. These studies provided atomic-level insights into the melting behavior of materials under extreme conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Hydrogen Risk Assessment Models (HyRAM) (Version 3.0 Technical Reference Manual)

The HyRAM software toolkit provides a basis for conducting quantitative risk assessment and consequence modeling for hydrogen infrastructure and transportation systems. HyRAM is designed to facilitate the use of state-of-the-art science and engineering models to conduct robust, repeatable assessments of hydrogen safety, hazards, and risk. HyRAM includes generic probabilities for hydrogen equipment failures, probabilistic models for the impact of heat flux on humans and structures, and computationally and experimentally validated first-order models of hydrogen release and flame physics. HyRAM integrates deterministic and probabilistic models for quantifying accident scenarios, predicting physical effects, and characterizing hydrogen hazards (thermal effects from jet fires, overpressure effects from deflagrations), and assessing impact on people and structures. HyRAM is developed at Sandia National Laboratories for the U.S. Department of Energy to increase access to technical data about hydrogen safety and to enable the use of that data to support development and revision of national and international codes and standards. HyRAM is a research software in active development and thus the models and data may change. This report will be updated at appropriate developmental intervals. This document provides a description of the methodology and models contained in the HyRAM version 3.0. HyRAM 3.0 includes the new ability to model cryogenic hydrogen releases from liquid hydrogen systems, using a different property calculation method and different equations of state. Other changes include modifications to the ignition probability calculations, component leak frequency calculations, and addition of default impulse data.

08 HYDROGEN↗
DOE OSTI2021

Hydrogen Risk Assessment Models (HyRAM) (V.3.1) (Technical Reference Manual)

The HyRAM software toolkit provides a basis for conducting quantitative risk assessment and consequence modeling for hydrogen infrastructure and transportation systems. HyRAM is designed to facilitate the use of state-of-the-art science and engineering models to conduct robust, repeatable assessments of hydrogen safety, hazards, and risk. HyRAM includes generic probabilities for hydrogen equipment failures, probabilistic models for the impact of heat flux on humans and structures, and experimentally validated first-order models of hydrogen release and flame physics. HyRAM integrates deterministic and probabilistic models for quantifying accident scenarios, predicting physical effects, and characterizing hydrogen hazards (thermal effects from jet res, overpressure effects from deflagrations), and assessing impact on people and structures. HyRAM is developed at Sandia National Laboratories for the U.S. Department of Energy to increase access to technical data about hydrogen safety and to enable the use of that data to support development and revision of national and international codes and standards. HyRAM is a research software in active development and thus the models and data may change. This report will be updated at appropriate developmental intervals. This document provides a description of the methodology and models contained in HyRAM version 3.1. There have been several impactful updates since version 3.0. HyRAM 3.1 contains a correction to use the volume fraction for two-phase speed of sound calculations; this only affects cryogenic releases in which two-phase ow (vapor and liquid) is predicted in the orifice. Other changes include clarifications that inputs for tank pressure should be given in absolute pressure, not gauge pressure. Additionally, the interface now rejects invalid inputs to probability distributions, and the less accurate single-point radiative source model selection was removed from the interface.

08 HYDROGEN↗
DOE OSTI2022

Plasma Assisted Catalytic Conversion of Carbon Dioxide (CO2) and Propane to Propylene and Carbon Monoxide (CO)

Presented at the NETL Project Review Meetings in 2022, the presentation summary includes the following status updates: -Feasibility of the CO2-ODH reaction with plasma demonstrated at much lower temperatures than conventional processes -Presence of CO2 enhances propane conversion in the plasma reactor -Ce doped, 5 wt.%/CexZr1-xO2 catalyst demonstrated enhanced selectivity and stability for propylene production via CO2-ODH process under thermal conditions -Comprehensive characterization coupled with designed catalytic experiments identified Cr3+ as the active site CO2-ODH proceeds via dehydrogenation route -Coke formation, which causes catalyst deactivation, inhibited by both Ce and CO2

Zhou, S. James↗
DOE OSTI2026

Elevating SolTrace's Capabilities for the Next Generation of Concentrating Solar Analysis

SolTrace is an open-source Monte Carlo ray tracing software developed at NREL. SolTrace can characterize concentrating solar thermal (CST) collector optical performance and is CST technology agnostic. Shown in Fig. 1, SolTrace is a foundational tool in NREL's CST system and component modeling suite. SolTrace's generic surface elements can flexibly model novel collector and receiver designs to predict spatial and temporal flux distributions - critical to understand for CST component design, performance prediction, and system integration. Since its initial development, SolTrace has over 1,650 references on Google Scholar, over 9,800 downloads since 2017, and has served the CST research and development community as a benchmark of 3rd party verification. SolTrace provides users with many options for defining surface shape and boundaries. However, SolTrace provides limited documentation which can result in a steep learning curve for new users. Additionally, SolTrace lacks the computational performance required to evaluate optical performance of a CST system over the course of a year and/or iteratively over design parameters in a timely manner. To address this, we are working towards a new release of SolTrace that enables increased computational throughput by implementing ray tracing acceleration structures and enabling GPU parallelization. Additionally, we are working to improve SolTrace's usability, accessibility, and maintainability by (1) automating solar position time-dependent simulation processes, (2) creating general CST collector templates of grouped elements, (3) updating the user interface to better visualize model inputs and outputs, and (4) creating a user support network through forums, "how to" videos, and documentation.

14 SOLAR ENERGY↗
DOE OSTI2025

High-Speed and Hysteresis-Free Near-Infrared Optical Hydrogen Sensor Based on Ti/Pd Bilayer Thin Films

Palladium (Pd) and titanium (Ti) exhibit opposite dielectric responses upon hydrogenation, with stronger effects observed in the near-infrared (NIR) region. Leveraging this contrast, we investigated Ti/Pd bilayer thin films as a platform for NIR hydrogen sensing—particularly at telecommunication-relevant wavelengths, where such devices have remained largely unexplored. Ti/Pd bilayers coated with Teflon AF (TAF) and fabricated via sequential electron-beam and thermal evaporation were characterized using optical transmission measurements under repeated hydrogenation cycles. The Ti (5 nm)/Pd (x = 2.5 nm)/TAF (30 nm) architecture showed a 2.7-fold enhancement in the hydrogen-induced optical contrast at 1550 nm compared to Pd/TAF reference films, attributed to the hydrogen ion exchange between the Ti and Pd layers. The optimized structure, with a Pd thickness of x = 1.9 nm, exhibited hysteresis-free sensing behavior, a rapid response time (t90 < 0.35 s at 4% H2), and a detection limit below 10 ppm. It also demonstrated excellent selectivity with negligible cross-sensitivity to CO2, CH4, and CO, as well as high durability, showing less than 6% signal degradation over 135 hydrogenation cycles. These findings establish a scalable, room-temperature NIR hydrogen sensing platform with strong potential for deployment in automotive, environmental, and industrial applications.

Chemistry↗
NASA NTRS1971

Emitted radiation characteristics of plutonium dioxide radioisotope thermoelectric generators

The nuclear and emitted radiation characteristics of the radioisotope elements and impurities in commercial grade plutonium dioxide are presented in detail. The development of the methods of analysis are presented. Radioisotope thermoelectric generators (RTG) of 1575, 3468 and 5679 thermal watts are characterized with respect to neutron and gamma photon source strength as well as spatial and number flux distribution. The results are presented as a function of detector position and light element contamination concentration for fuel age ranging from 'fresh' to 18 years. The data may be used to obtain results for given O-18 and Pu-236 concentrations. The neutron and gamma photon flux and dose calculations compare favorably with reported experimental values for SNAP-27.

Gingo, P. J.↗
NASA NTRS1975

Intracrystalline cation order in a lunar crustal troctolite

Lunar sample 76535 appears to be one of the most slowly cooled bits of silicate material yet studied. It provides, therefore, a unique opportunity for the study of ordering processes in the minerals present. A better understanding of these processes may permit better characterization of the thermal history of this and similar rocks. The cation ordering in the olivine is consistent with terrestrial olivines favoring the interpretation that ordering in olivines increases with increasing temperature. In low bronzite, the deviations from the common orthopyroxene space group appear to be caused by cation order on the basis of four M sites instead of two. The degree of cation order in each of these minerals is consistent with the rock having been excavated from its depth of formation by tectonic or impact processes without being reheated above 300 C.

Smyth, J. R.↗
NASA NTRS1980

Addition polyimide end cap study

The characterization of addition polyimides with various end caps for adhesive applications at 120-250 C environments is discussed. Oligometric polyimides were prepared from 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 3,3'-methylenedianiline which were end-capped with functionally reactive moities which cause crosslinking when the oligomers are heated to 200-400 C. The syntheses of the oligomers are outlined. The thermolysis of the oligomers was studied by differential scanning calorimetry and the resulting polymers were characterized by differential thermal analysis and adhesive performance. The adhesive data include lap shear strengths on titanium 6-4 adherends both before and after aging for 1000 hours at 121 C and/or 232 C.

St.clair, T. L.↗
NASA NTRS1983

Electrical resistivity of composite superconductors

In addition to its superconducting properties, a superconductor is usually characterized by poor thermal conductivity and relatively high electrical resistivity in the normal state. To remedy this situation a study of superconducting properties of Cu-rich CU-Nb wires prepared by directionally solidified and cold-rolled technique was conducted. Some of the specimens were prepared by melting, directional solidification and diffusing in Tin. A total of 12 wire specimens was tested. Each specimen was analyzed by plotting experimental data into the following curves: the graph of the residual resistivity as a function of the specimen current at 4.3 K; and the graph of the electrical resistivity as a function of the temperature at a constant current.

Davis, J. H.↗
NASA NTRS1983

Improved Oxygen Sources for Breathing Apparatus

Research is described which is directed toward the preparation of chemical oxygen sources which exhibited improved O2 storage and reaction characteristics when compared to potassium superoxide (KO2). The initial focus of the research was the preparation of calcium superoxide (Ca(O2)2) by the disproportionation of calcium peroxide diperoxyhydrate. the Ca(O2)2 was characterized by chemical, thermal, and x ray analyses. Several methods for scaling up the Ca(O2)2 syntheis process were studied. The reactivity of Ca(O2)2 toward humidified carbon dioxide (CO2) was evaluated and was compared to that of KO2 under flow test conditions approximating those existing in portable breathing apparatus. The reactivities of mixtures of KO2 and Ca(O2)2 or lithium peroxide towards humidified CO2 were also studied. Finally, an analysis of two commercial, KO2-based, self contained self rescuers was conducted to determine the potential weight and volume savings which would be possible if Ca(O2)2 or a mixture of KO2 and Ca(O2)2 were used as a replacement for KO2.

Wood, P. C.↗
NASA NTRS1986

Halogen occultation experiment (HALOE) performance verification test procedure

The Performance Verification Test Procedure is given for the Halogen Occultation Experiment (HALOE) instrument, which is being developed in house at the Langley Research Center for the Upper Atmosphere Research Satellite (UARS). This procedure is used for comprehensive performance testing of the HALOE instrument which occurs before, during, and after flight environmental tests. The radiometric performance tests include noise, drift, linearity, instantaneous field-of-view, cal wheel gas cell characterization, and self thermal emissions. Pointer/tracker performance tests include sun sensor performance, gimbal performance, control system performance, and boresight alignment. In addition, the instrument is tested functionally in simulated orbit sequences and all command operating modes are exercised. The data analysis required for each test is specified and pass/fail criteria are given where applicable. This test will fully demonstrate the HALOE instrument's ability to achieve science mission requirements. The HALOE instrument is a gas correlation radiometer that measures vertical distribution of eight upper atmospheric constituents: O3, HCl, HF, NO, CH4, H2O, NO2, and CO2.

Mauldin, L. E., III↗
NASA NTRS1987

Mechanical properties of high gradient and hot isostatically pressed PWA 1480

This program has been designed to evaluate the potential benefits to alloy 1480 material properties due to high thermal gradient casting, hot isostatic pressing, and alternative heat treatment. Alloy 1480 castings have been obtained from vendors representing the extremes of commercial casting thermal gradients. Quantitative characterization of the dendrite arm spacing (DAS) and pore distributions has been conducted. A hot isostatic pressing (HIP) schedule, which avoids the many pitfalls of single crystal HIP has been devised for alloy 1480. In addition, an alternate heat treatment for alloy 1480 has been devised which provides benefits in mechanical properties. The standard gradient cast test material is being evaluated in the standard heat treat condition as a baseline and in the HIP plus alternate heat treated condition. The fhigh gradient cast material is being evaluated in alternate heat treat and HIP plus alternate heat treated conditions. Evaluations focus on demonstration of the benefits due to the applied processes, especially in the area of cyclic life.

Fritzemeier, L. G.↗
NASA NTRS1987

Sol-Gel synthesis of MgO-SiO2 glass compositions having stable liquid-liquid immiscibility

MgO-SiO2 glasses containing up to 15 mol % MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol % MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol % MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol %) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

Bansal, Narottam P.↗