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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Shock compression of molybdenum single crystals to 110 GPa: Elastic–plastic deformation and crystal anisotropy

To explore the role of crystal anisotropy on the elastic-plastic deformation of BCC single crystals at high shock stresses, molybdenum (Mo) single crystals were shock compressed along [100], [111], and [110] orientations at elastic impact stresses between 20 and 110 GPa. Laser interferometry was used to measure shock wave velocities and particle velocity histories. Along the [100] and [111] orientations, elastic-plastic waves (two wave structure) were observed up to 110 GPa. Along the [110] orientation, the two wave structure was observed only up to 90 GPa. The measured elastic wave amplitudes were analyzed to determine crystal anisotropy effects, impact stress dependence, and the activated slip systems on the Hugoniot elastic limit. The results from our work have provided insight into the role of crystal anisotropy on the elastic-plastic deformation under shock compression at high stresses.

42 ENGINEERING↗
DOE OSTI2022

Gene-by-environment interactions in plants: Molecular mechanisms, environmental drivers, and adaptive plasticity

Abstract Plants demonstrate a broad range of responses to environmental shifts. One of the most remarkable responses is plasticity, which is the ability of a single plant genotype to produce different phenotypes in response to environmental stimuli. As with all traits, the ability of plasticity to evolve depends on the presence of underlying genetic diversity within a population. A common approach for evaluating the role of genetic variation in driving differences in plasticity has been to study genotype-by-environment interactions (G × E). G × E occurs when genotypes produce different phenotypic trait values in response to different environments. In this review, we highlight progress and promising methods for identifying the key environmental and genetic drivers of G × E. Specifically, methodological advances in using algorithmic and multivariate approaches to understand key environmental drivers combined with new genomic innovations can greatly increase our understanding about molecular responses to environmental stimuli. These developing approaches can be applied to proliferating common garden networks that capture broad natural environmental gradients to unravel the underlying mechanisms of G × E. An increased understanding of G × E can be used to enhance the resilience and productivity of agronomic systems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Gradient nanostructured steel with superior tensile plasticity

Nanostructured metallic materials with abundant high-angle grain boundaries exhibit high strength and good radiation resistance. While the nanoscale grains induce high strength, they also degrade tensile ductility. We show that a gradient nanostructured ferritic steel exhibits simultaneous improvement in yield strength by 36% and uniform elongation by 50% compared to the homogenously structured counterpart. In situ tension studies coupled with electron backscattered diffraction analyses reveal intricate coordinated deformation mechanisms in the gradient structures. The outermost nanolaminate grains sustain a substantial plastic strain via a profound deformation mechanism involving prominent grain reorientation. This synergistic plastic co-deformation process alters the rupture mode in the post-necking regime, thus delaying the onset of fracture. The present discovery highlights the intrinsic plasticity of nanolaminate grains and their significance in simultaneous improvement of strength and tensile ductility of structural metallic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mechanochemically accelerated deconstruction of chemically recyclable plastics

Plastics redesign for circularity has primarily focused on monomer chemistries enabling faster deconstruction rates concomitant with high monomer yields. Yet, during deconstruction, polymer chains interact with their reaction medium, which remains underexplored in polymer reactivity. Here, we show that, when plastics are deconstructed in reaction media that promote swelling, initial rates are accelerated by over sixfold beyond those in small-molecule analogs. This unexpected acceleration is primarily tied to mechanochemical activation of strained polymer chains; however, changes in the activity of water under polymer confinement and bond activation in solvent-separated ion pairs are also important. Together, deconstruction times can be shortened by seven times by codesigning plastics and their deconstruction processes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of Plasticizer Content and Ceramic Addition on Electrochemical Properties of Cross-Linked Polymer Electrolyte

The development of a safe electrolyte is the key to improving energy density for next generation lithium batteries. In this work, UV-crosslinked poly(ethylene oxide) (PEO) -based polymer and composite electrolytes are systematically investigated on their ionic conductivity, mechanical and electrochemical properties. The polymer electrolytes are plasticized with non-flammable linear short-chain PEO. In the composite electrolytes, a doped lithium aluminum titanium phosphate (LATP) ceramic, LICGC™, is used as the ceramic filler. It is found that the addition of the plasticizer leads to a tradeoff between ion transport and mechanical properties. In contrast, the addition of ceramic fillers improves both the ionic conductivity and mechanical properties. The sample with 20 wt% of LICGC™ shows a conductivity of ~0.6 mS cm –1 at 50 °C. This sample also demonstrates much longer cycle life than the neat polymer electrolyte in Li platting/stripping test with a capacity of 1 mAh cm –2 . Further, a full cell made with this composite electrolyte against Li metal anode and high voltage LiNi 0.6 Mn 0.2 Co 0.2 O 2 cathode shows 94% capacity retention after 30 cycles, compared to 58% capacity retention with the neat polymer electrolyte. These results demonstrate that a hybrid of polymer/ceramic/non-flammable plasticizer is a promising path to high energy density, high voltage lithium batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Compressive strength of the plastic-bonded explosive surrogate idoxuridine under quasistatic and dynamic compression

Inert simulant materials, or “mocks”, are often used as surrogates for plastic-bonded explosives (PBX) in non-detonative tests in order to mitigate hazards. Mocks should reproduce as many non-detonative properties of the explosive as possible, including structural behavior in a variety of thermal and mechanical environments. Recently, the molecular crystal idoxuridine (IDOX) has been identified as an ideal mock for the main component in the explosive polymer-matrix composite PBX 9501, and has performed favorably under quasistatic loading conditions. Here, in order to assess robustness over a range of mechanical environments, plastic-bonded IDOX was compression tested from 0.001/s to 2000/s strain rates and compared to PBX 9501 historical data. Plastic-bonded IDOX showed good agreement to PBX 9501 across these strain rates, justifying continued development and production as a mock.

Burch, Alexandra C.↗
DOE OSTI2020

Understanding plasticity in irradiated alloys through TEM in situ compression pillar tests

Depth-sensing transmission electron microscopic (TEM) in situ mechanical testing has become widely utilized for understanding deformation in irradiated materials. Until now, compression pillars have primarily been used to study the elastic properties and yield of irradiated materials. In this study, we utilize TEM in situ compression pillars to investigate plastic deformation in two ion-irradiated alloys: Fe–9% Cr oxide dispersion strengthened (ODS) alloy and nanocrystalline Cu–24% Ta. We develop an algorithm to automate the extraction of instantaneous pillar dimensions from TEM videos, which we use to calculate true stress–strain curves and strain hardening exponents. True stress–strain curves reveal intermitted plastic flow in all specimen conditions. In the Fe–9% Cr ODS, intermitted plastic flow is linked to strain bursts observed in TEM videos. Low strain hardening or strain softening is observed in all specimen conditions. TEM videos link the strain softening in irradiated Fe–9% Cr ODS to dislocation cross-slip, and in Cu–24% Ta to grain boundary sliding.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Heterosynaptic plasticity in memristive and memcapacitive lipid bilayers: A snapshot review

Synaptic plasticity refers to activity-dependent synaptic strengthening or weakening between neurons. It is usually associated with homosynaptic plasticity, which refers to a synaptic junction controlled by interactions between specific neurons. Heterosynaptic plasticity, on the other hand, lacks this specificity. It involves much larger populations of synapses and neurons and can be associated with changes in synaptic strength due to nonlocal alterations in the ambient electrochemical environment. Here, this paper presents specific examples demonstrating how variations in the ambient electrochemical environment of lipid membranes can impact the nonlinear dynamical behaviors of memristive and memcapacitive systems in droplet interface bilayers (DIBs). Examples include the use of pH as a modulatory factor that alters the voltage-dependent memristive behavior of alamethicin ion channels in DIB lipid bilayers, and the discovery of long-term potentiation (LTP) in a lipid bilayer-only system after application of electrical stimulation protocols.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Modular Growth and Nucleation Formulations in Modular Plasticity Models

Recent investigations like the second and third Sandia Fracture Challenges have characterized and demonstrated the performance of a variety of failure techniques and models. These surveys have considered a wide breadth of models encapsulating both general failure criteria as well as those focusing on pore nucleation and growth. Extensive reviews exist on both topics. The former category generally consists of classic models like the Johnson-Cook or Wilkins criteria. These models were recently added to modular plasticity models in the Library of Advanced Materials for Engineering (LAME) as criteria for use with element death capabilities. The latter category was not treated in that effort. There exists a large class of failure models based on predicting the evolution of pores and failure associated with such microstructures. While the exact mechanisms and corresponding impact on the macroscale behavior remain an active area of research, a large suite of formulations have been proposed combining different features of both pore nucleation and subsequent growth. The most famous of these are based on the popular Gurson model of pore growth derived via micromechanical analysis assuming a plastically incompressible matrix. Numerous other models exist for both growth and nucleation and the Cocks-Ashby growth and Horstemeyer-Gokhale nucleation models have been used successfully in recent Sandia Fracture Challenges. This specific combination is colloquially referred to as the "BCJ-failure model as it has been frequently used with the Bammann-Chisea-Johnson plasticity model.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Enhancing Plastic Recycling Through Nano-Scale Structure Analysis in Custom Block Copolymer Filaments (Rev.1)

As plastic production continues to increase, new methods to combat plastic waste are needed. This paper explores upcycling, a way to increase the utility or value of waste plastic. This can be done using block copolymers as compatibilizers. Block copolymers are made of two immiscible polymer blocks that phase separate on the nanoscale, forming small structures. The orientation of these nano-scale structures influences mechanical properties, and we show that orientation can be controlled by directional 3D (three dimensional) printing. Using small-angle X-ray scattering (SAXS), we analyze block copolymer filaments extruded at varying speeds. The SAXS data provide a baseline understanding of nano-scale structure in these unique filaments for future use in 3D printing experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2024

From Plastic Waste to Fuel: Pyrolysis and Gasification of Polyethylene for Hydrogen Production

Thermochemical conversion processes offer promising solutions to address the plastic pollution crisis by transforming plastic waste into valuable products, notably hydrogen. In this study, thermal pyrolysis and steam gasification of polyethylene (PE), the most abundantly produced plastic waste, are investigated in a drop tube reactor system. Various process parameters, namely temperature, residence time, and feedstock composition, are evaluated to establish their correlations with reaction performance. Coal refuse, obtained from discarded thickener underflow in coal processing, is introduced as a co-feedstock for gasification to enhance PE handling and examine synergistic effects on product distribution, particularly H2 yield and syngas quality. Furthermore, the potential of low-cost, environmentally friendly catalysts (i.e., iron oxides, coal ash) for tar reforming is explored.

Natesakhawat, Sittichai↗
DOE OSTI2024

Demonstrating the Feasibility of Biomass Pyrolysis Liquid, Coal, Plastic Oil Mixtures for Entrained Flow Gasification

There is interest in co-gasifying coal, biomass and plastic. An attractive alternative is to do that in a pressurized entrained-flow gasifier, technology that has been used for coal gasification for decades. The approach taken in this study is to liquefy biomass through fast pyrolysis and to liquefy waste plastic by thermal decomposition. The liquids form the basis of a slurry that also includes coal particles. In this work, several different compositions of coal-bioliquid-plastic oil slurries were prepared and evaluated for viscosity and settling properties. Suitable composition ranges were identified and are highlighted in the presentation.

Hughey, Logan↗
DOE OSTI2024

Development of a Liquid Bridge Model for Particle Agglomeration and Defluidization in Plastic Pyrolysis

Molten plastic that forms during the pyrolysis of plastic or municipal solid waste feedstock can lead to particle agglomeration. A liquid bridge model is developed in MFiX-DEM and validated against a cold flow experiment with glass beads coated with silicone oil. The liquid bridge model is then extended to support an evolving liquid layer thickness for pyrolysis applications. The extended model is used to study the sensitivity of the pyrolysis reactor to solids holdup, flow conditions, and plastic properties.

Banerjee, Subhodeep↗
DOE OSTI2024

Real-Time Observation of Nanoscale Kink Band Mediated Plasticity in Ion-Irradiated Graphite: An In Situ TEM Study

Graphite IG-110 is a synthetic polycrystalline material used as a neutron moderator in reactors. Graphite is inherently brittle and is known to exhibit a further increase in brittleness due to radiation damage at room temperature. To understand the irradiation effects on pre-existing defects and their overall influence on external load, micropillar compression tests were performed using in situ nanoindentation in the Transmission Electron Microscopy (TEM) for both pristine and ion-irradiated samples. While pristine specimens showed brittle and subsequent catastrophic failure, the 2.8 MeV Au2+ ion (fluence of 4.378 × 1014 cm−2) irradiated specimens sustained extensive plasticity at room temperature without failure. In situ TEM characterization showed nucleation of nanoscale kink band structures at numerous sites, where the localized plasticity appeared to close the defects and cracks while allowing large average strain. We propose that compressive mechanical stress due to dimensional change during ion irradiation transforms buckled basal layers in graphite into kink bands. The externally applied load during the micropillar tests proliferates the nucleation and motion of kink bands to accommodate the large plastic strain. The inherent non-uniformity of graphite microstructure promotes such strain localization, making kink bands the predominant mechanism behind unprecedented toughness in an otherwise brittle material.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A numerical study of reversible plasticity using continuum dislocation mechanics

In this contribution, an elasto-viscoplastic fast Fourier transform-based (EVPFFT) numerical implementation of the Mesoscale Field Dislocation Mechanics (MFDM) formulation, called MFDM-EVPFFT, is applied to study the reversible plastic behavior of periodic two-phase crystalline composites with an elasto-viscoplastic plastic matrix and a purely elastic second phase. Additionally, periodic laminate microstructures of this kind with different periods (i.e. sizes) are considered to examine the size dependence of the Bauschinger effect and hardening during cyclic loading. Comparisons with classic composite effects obtained with conventional crystal plasticity are discussed. Specifically, the MFDM-EVPFFT results shed light on the hardening mechanisms due to piling-up/unpiling-up of geometrically-necessary dislocations (GND) during reverse loading.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Gasification of Waste Plastic to Enable a Circular Economy: Literature Review Focusing on H2/Syngas Production

This report briefly reviews 1) the physicochemical properties of feedstocks; 2) hydrogen/syngas production from plastic gasification and co-gasification of plastic with coal and/or biomass, including the discussions on effects of operating conditions on H2 production; and 3) the mechanism of plastic gasification, including the formation and decomposition of char/tar during gasification process.

Shi, Fan↗
DOE OSTI2023

Defect-resistant plastic scintillators with aliphatic additives

A plastic scintillator includes a polymer matrix, an aliphatic additive present in the polymer matrix in an effective amount to impart fog resistance to the plastic scintillator, and at least one fluorescent dye in the polymer matrix, the dye being effective to provide scintillation upon exposure to radiation. The effective amount of the aliphatic additive is in a range of greater than 0 weight percent up to 5 weight percent relative to the total weight of the plastic scintillator. Moreover, the aliphatic additive has a structure comprising up to 300 repeat units.

Mabe, Andrew Neil↗
DOE OSTI2023

Low-Velocity Impact Performances of Healed Polymer Fiber Reinforced Plastics

Extending the lifecycle of traditional carbon or glass fiber-reinforced plastics is a complicated problem. The lack of sustainability limits the applications of the traditional composite materials in the vehicle industries where recycling and repurposing are critical issues. Alternatives for the low-stressed structural components are polymer fiber-reinforced plastics (PFRPs). In PFRPs, both the fibers and matrix are composed of thermoplastic polymers (e.g. polypropylene or polyethylene). They are lightweight, easy to manufacture, and cost-effective. Additionally, recycling and repurposing thermoplastic polymers are well understood. Therefore, the PFRPs have strong advantages compared to the traditional fiber-reinforced composites in low-stressed structural applications. In this study, we investigated the low-velocity impact (LVI) performances of the PFRPs and compared them with carbon fiber-reinforced plastics (CFRPs). A semi-spherical impactor was dropped to flat, square panels, and the absorbed impact energy was measured. The damage mechanisms were examined using a Xray µCT scan. The PFRPs outperformed the CFRPs in terms of perforation energy normalized by plate thickness and density. After the perforation, we healed the fractured plates by leveraging the recyclability of the thermoplastic polymers. The healing process of the panels was identical to the initial panel manufacturing process. No additional materials were added during the healing process. The healed PFRP panels were impacted again and substantially recovered energy absorption capability. We also conducted the repeated-impact test with several different impact energies. Unlike the CFRPs where the impact peak load decreased as the impacts repeated, the PFRPs showed an increasing trend. Such a unique mechanism was due to the strain-hardening behavior of the polymer fibers and matrix. As a result, the repeated-impact life of the PFRPs was significantly enhanced. These results are particularly interesting in the automotive or aerospace industries where repeated LVI is frequently observed.

Ko, Seunghyun↗