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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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The Plasticity of Molecular Interactions Governs Bacterial Microcompartment Shell Assembly
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In situ friction and wear behavior of rubber materials incorporating various fillers and/or a plasticizer in high-pressure hydrogen
Polymers are used routinely for equipment and infrastructure in hydrogen vehicle refueling stations, but significant gaps remain in understanding their hydrogen compatibility. The tribological properties of these materials in a high-pressure hydrogen environment is important in preventing component failure and the need for frequent replacement. We present in situ tribological studies on model rubbers, which include common fillers and plasticizer, using an in situ tribometer developed previously. Results suggest a clear, yet complicated, combined effect of the high-pressure hydrogen and the additives on the tribological performance of the chosen materials, as compared to matching experiments performed in ambient air. We find that the additives improved wear resistance in EPDM but deteriorated that in NBR due to disparate additive-polymer interactions.
Rapid atom-efficient polyolefin plastics hydrogenolysis mediated by a well-defined single-site electrophilic/cationic organo-zirconium catalyst
Polyolefins comprise a major fraction of single-use plastics, yet their catalytic deconstruction/recycling has proven challenging due to their inert saturated hydrocarbon connectivities. Here a very electrophilic, formally cationic earth-abundant single-site organozirconium catalyst chemisorbed on a highly Brønsted acidic sulfated alumina support and characterized by a broad array of experimental and theoretical techniques, is shown to mediate the rapid hydrogenolytic cleavage of molecular and macromolecular saturated hydrocarbons under mild conditions, with catalytic onset as low as 90 °C/0.5 atm H 2 with 0.02 mol% catalyst loading. For polyethylene, quantitative hydrogenolysis to light hydrocarbons proceeds within 48 min with an activity of > 4000 mol(CH 2 units)·mol(Zr) –1 ·h –1 at 200 °C/2 atm H 2 pressure. Under similar solventless conditions, polyethylene-co–1-octene, isotactic polypropylene, and a post-consumer food container cap are rapidly hydrogenolyzed to low molecular mass hydrocarbons. Regarding mechanism, theory and experiment identify a turnover-limiting C-C scission pathway involving ß-alkyl transfer rather than the more common σ-bond metathesis.
Average neutron time-of-flight instrument response function inferred from single D-T neutron events within a plastic scintillator
The apparent ion temperature and neutron-reaction history are important characteristics of a fusion plasma. Extracting these quantities from a measured neutron-time-of-flight signal requires accurate knowledge of the instrument response function (IRF). This paper describes a novel method for obtaining the IRF directly for single DT neutron interactions by utilizing n-alpha coincidence. The t(d,α)n nuclear reaction was produced at Sandia National Laboratories’ Ion Beam Laboratory using a 300 keV Cockcroft-Walton generator to accelerate a 2.5 μA beam of 175 keV D + ions into a stationary ErT 2 target. The average neutron IRF was calculated by taking a time-corrected average of individual neutron events within an EJ-228 plastic scintillator. The scintillator was coupled to two independent photo-multiplier tubes operated in the current mode: a Hamamatsu 5946 mod-5 and a Photek PMT240. Finally, the experimental setup and results will be discussed.
Dynamic absorption in optical pyrometry of hot spots in plastic-bonded triaminotrinitrobenzene [Optical Pyrometry of Shock-induced Hot Spots in Plastic-bonded Triaminotrinitrobenzene]
Herein we demonstrate a methodology for measuring optical pyrometry in environments which are disadvantageous for typical pyrometery applications by introducing additional fit parameters to account for absorption or emission which convolutes the thermal spectrum. Emission spectra from a plastic-bonded formulation of triaminotrinitrobenzene (TATB) shocked by 2-4 km s -1 impacts with Al flyer plates show significant deviations from graybody behavior. To extract reliable temperatures via optical pyrometry, we fit the spectra to a combination of a graybody and either a Gaussian absorption or emission spectrum. We found that the absorption needed to fit the data corresponds well with the known pressure-dependent absorption of TATB, and that the absorption model gives temperatures and emissivities in line with other explosives. By contrast, emission gives temperatures too low and emissivities that decrease as more material reacts. We conclude the nonthermal part of the spectrum is dominated by the absorption of unreacted TATB, and accurate pyrometry of TATB must use either our graybody plus absorption model or must limit the spectral range of observation to above 650 nm.
Structural plasticity of the selectivity filter in a nonselective ion channel
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Elastic plastic self-consistent (EPSC) modeling of San Carlos olivine deformed in a D-DIA apparatus
Abstract not provided
Plastics to fuel or plastics: Life cycle assessment-based evaluation of different options for pyrolysis at end-of-life
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A survey of pulse shape options for a revised plastic ablator ignition design
Recent experimental results using the “high foot” pulse shape for inertial confinement fusion ignition experiments on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] have shown encouraging progress compared to earlier “low foot” experiments. These results strongly suggest that controlling ablation front instability growth can significantly improve implosion performance even in the presence of persistent, large, low-mode distortions. Simultaneously, hydrodynamic growth radiography experiments have confirmed that ablation front instability growth is being modeled fairly well in NIF experiments. It is timely then to combine these two results and ask how current ignition pulse shapes could be modified to improve one-dimensional implosion performance while maintaining the stability properties demonstrated with the high foot. This paper presents such a survey of pulse shapes intermediate between the low and high foot extremes in search of an intermediate foot optimum. Of the design space surveyed, it is found that a higher picket version of the low foot pulse shape shows the most promise for improved compression without loss of stability.
Solid Cylindrical Bar Torsion for Characterizing Shear Plastic Deformation and Failure.
Abstract not provided.
Stability and amorphization of Cu–Nb interfaces during severe plastic deformation: Molecular dynamics simulations of simple shear
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Self-organized, size-selection of precipitates during severe plastic deformation of dilute Cu-Nb alloys at low temperatures
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Plasticity of laser-processed nanoscale Al Al2Cu eutectic alloy
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Ultra-high strength and plasticity mediated by partial dislocations and defect networks: Part I: Texture effect
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