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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Impact of Ionic Liquid on Lithium Ion Battery with a Solid Poly(Ionic Liquid) Pentablock Terpolymer as Electrolyte and Separator

In this work, a ternary blend solid polymer electrolyte (SPE) consisting of a poly(ionic liquid) (PIL) multiblock polymer, lithium salt, and ionic liquid (IL) was investigated with the goal of understanding the influence of IL concentration on ion transport mechanisms and electrochemical stability. The physical, transport, mechanical, morphological, and electrochemical properties of the ternary blend SPE were systematically investigated as a function of IL concentration (r = [IL]/[PIL] mole ratio between 0.1 and 0.7). The results indicate that with increasing IL concentration, the continuous conductive domain increases along with the polymer chain segmental mobility, as well as facilitate ionic conductivity, while the mechanical modulus exhibits a percolation threshold (from 52.17 MPa to 0.55 MPa at r = 0.2 to 0.3). Surprisingly, at higher IL concentrations, there is a reduction in the lithium cation mobility (i.e., 9.3 × 10-12 m2 s-1 versus 3.8 × 10-12 m2 s-1 for r = 0.2 versus r = 0.5, respectively) as evidenced by pulsed-field gradient nuclear magnetic resonance (PFG-NMR), which coincides with an increased overpotential (i.e., 50 mV versus 150 mV for r = 0.2 versus r = 0.5, respectively) evidenced by lithium metal stripping and plating. This work provides valuable insights into the impact of IL on lithium ion conducting PIL block polymers, which may enable the design of new SPEs with both high ionic conductivity and improved stability for the future lithium ion batteries.

Chen, Tzu-Ling↗
DOE OSTI2020

Effect of Extended Aging and Oxidation on Linear Poly(propylenimine)-Mesoporous Silica Composites for CO 2 Capture from Simulated Air and Flue Gas Streams

Physical aging or degradation of amine-containing polymers and supported amine adsorbents is a critical issue that could limit practical application of such materials for CO 2 capture. However, to date, there is a scarcity of studies that evaluate the long-term stability of amine-based sorbents without the exclusive use of accelerated aging tests. Here, we demonstrate that extended aging (~2 years) of linear poly(propylenimine) (LPPI) confined in mesoporous silica (SBA-15) supports does not drastically impact the CO 2 adsorption performance under simulated flue gas (10% CO 2 ) and direct air capture (DAC, 400 ppm CO 2 ) conditions, although the behavior of the aged sorbents and polymers in the two CO 2 concentration regimes differs. Sorbents made with aged LPPI had modestly decreased CO 2 uptake performance (<~20% lower) compared to the fresh polymers, with overall good CO 2 cycling performance. The data indicate that only slow degradation occurs under the deployed ambient storage conditions. Even after extended aging, the LPPI-based sorbents preserved their ability to display stable temperature-swing cycling performance. In parallel, the impact of blending LPPI polymers of different number-average molecular weights, M n , is evaluated, seeking to understand its impact on adsorbent performance. We find that the results demonstrate that blends of two M n aged LPPI give similar CO 2 adsorption performance to adsorbents made from a single M n LPPI, suggesting that molecular weight will not negatively impact adsorbent performance in the studied M n range. After an accelerated oxidation experiment, the aged LPPI sorbents retained a larger portion of the samples’ original performance when cycling under simulated flue gas conditions than under DAC conditions. However, in each case, the oxidized sorbents could be cycled repeatedly with consistent uptake performance. Overall, these first of their kind extended aging tests suggest that LPPI-based amine adsorbents offer promise for long term, stable use in carbon capture applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Miscibility and Cocrystallization in Ethylene–Vinyl Alcohol Copolymer Blends

The compatibility among different ethylene−vinyl alcohol (EVOH) copolymer grades plays a crucial role in determining how easily they can be recycled when present together in a mixed waste stream. In this work, melt miscibility and cocrystallization in 50/50 wt/wt binary blends of EVOH copolymers with differing ethylene content were studied. Blends with up to a 21 mol % difference in composition were analyzed. Thin films of miscible blends appeared homogeneous in the melt as observed under an optical microscope, whereas AFM height images showed that immiscible blends underwent surface roughening due to phase separation. For copolymers with modest composition differences, the blend behaved as a single component, showing single, narrow melting and crystallization peaks in DSC thermograms, indicating cocrystallization at the level of crystal stems. Interestingly, even phase-separated blends demonstrated partial cocrystallization due to partial miscibility of the components in the molten phase-separated domains. The extent of cocrystallization is governed by the difference in freezing points of the components; rapid cooling increased cocrystallization in the blends. The maximum compositional difference allowed for miscibility is not constant but depends on the blend’s average comonomer content, in agreement with the “miscibility window” calculated from literature pressure−volume−temperature behavior for the individual EVOH copolymers and regular mixing theory. This study helps illuminate the effect of copolymer composition on miscibility, as well as cocrystallization behavior in blends of random copolymers with cocrystallizable units.

Cocrystallization↗
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 OSTI2022

Two‐Dimensional Polycyclic Photovoltaic Molecule with Low Trap Density for High‐Performance Photocatalytic Hydrogen Evolution

Abstract Typical organic semiconductors show a high trap density of states (10 16 –10 18 cm −3 ), providing a large number of centers for charge‐carrier recombination, thus hindering the development of photocatalytic hydrogen evolution. Here, we design and synthesize a two‐dimensional polycyclic photovoltaic material, named as TPP, to reduce the trap density to as low as 2.3×10 15 cm −3 , which is 1–3 orders of magnitude lower than those of typical organic semiconductors. Moreover, TPP exhibits a broad and strong absorption, ordered molecular packing with a large crystalline coherence length and enhanced electron mobility. Then, the bulk heterojunction nanoparticles (BHJ‐NPs) based on a blend of polymer donor (PM6) and TPP exhibit an average hydrogen evolution rate (HER) of 64.31 mmol h −1 g −1 under AM1.5G sunlight (100 mW cm −2 ), and 72.75 mmol h −1 g −1 under 330–1100 nm illumination (198 mW cm −2 ) higher than that of the control NPs based on typical PM6 : Y6 (62.67 mmol h −1 g −1 ).

Zhang, Zhenzhen↗
DOE OSTI2021

Two-Dimensional Polycyclic Photovoltaic Molecule with Low Trap Density for High-Performance Photocatalytic Hydrogen Evolution

Typical organic semiconductors show a high trap density of states (10 16 –10 18 cm -3 ), providing a large number of centers for charge-carrier recombination, thus hindering the development of photocatalytic hydrogen evolution. In this report we design and synthesize a two-dimensional polycyclic photovoltaic material, named as TPP, to reduce the trap density to as low as 2.3×10 15 cm -3 , which is 1–3 orders of magnitude lower than those of typical organic semiconductors. Moreover, TPP exhibits a broad and strong absorption, ordered molecular packing with a large crystalline coherence length and enhanced electron mobility. Then, the bulk heterojunction nanoparticles (BHJ-NPs) based on a blend of polymer donor (PM6) and TPP exhibit an average hydrogen evolution rate (HER) of 64.31 mmol h -1 g -1 under AM1.5G sunlight (100,mW cm -2 ), and 72.75 mmol h -1 g -1 under 330–1100 nm illumination (198 mW cm -2 ) higher than that of the control NPs based on typical PM6 : Y6 (62.67 mmol h -1 g -1 ).

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

Polymer-Based Thermally Stable Chemiresistive Sensor for Real-Time Monitoring of NO 2 Gas Emission

Here, we present a thermally stable, mechanically compliant, and sensitive polymer-based NO 2 gas sensor design. Interconnected nanoscale morphology driven from spinodal decomposition between conjugated polymers tethered with polar side chains and thermally stable matrix polymers offers judicious design of NO 2 -sensitive and thermally tolerant thin films. The resulting chemiresitive sensors exhibit stable NO 2 sensing even at 170 °C over 6 h. Controlling the density of polar side chains along conjugated polymer backbone enables optimal design for coupling high NO 2 sensitivity, selectivity, and thermal stability of polymer sensors. Lastly, thermally stable films are used to implement chemiresistive sensors onto flexible and heat-resistant substrates and demonstrate a reliable gas sensing response even after 500 bending cycles at 170 °C. Such unprecedented sensor performance as well as environmental stability are promising for real-time monitoring of gas emission from vehicles and industrial chemical processes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

On-device lead sequestration for perovskite solar cells

Perovskite solar cells, as an emerging high-efficiency and low-cost photovoltaic technology face challenges on their way towards commercialization. Substantial improvements have been made to device stability but potential issues with lead toxicity and leaching from devices remain relatively unexplored. The potential for lead leakage could be perceived as an environmental and public health risk when using perovskite solar cells in building-integrated photovoltaics. Here we present a chemical approach for on-device sequestration of more than 96 per cent of lead leakage caused by severe device damage. A coating of lead-absorbing material is applied to the front and back sides of the device stack. On the glass side of the front transparent conducting electrode, we use a transparent lead-absorbing molecular film containing phosphonic acid groups that bind strongly to lead. On the back (metal) electrode side, we place a polymer film blended with lead-chelating agents between the metal electrode and a standard photovoltaic packing film. The lead-absorbing films on both sides swell to absorb the lead, rather than dissolve, when subjected to water soaking, thus retaining structural integrity for easy collection of lead after damage.

14 SOLAR ENERGY↗
DOE OSTI2020

Characterization and Analysis of Insulated Metal Substrate-Based SiC Power Module for Traction Application

This paper presents the electrical characterization and drive cycle--based thermal analysis of an insulated metal substrate (IMS)--based silicon carbide power module for high-power traction inverters. The substrate was constructed using a thin layer of polymer--ceramic blend dielectric material with a thick copper core to improve transient thermal performance. The cooling performance of this module has already been validated with promising results. In this paper, an experimental test bed was set up to evaluate the dynamic and static electrical performance of the designed module under a wide range of operating conditions. The characterization results were then used to develop a drive cycle--based thermal model to validate the performance compared to the traditional direct bonded copper--based power module. The results indicate that the IMS-based power module is a suitable solution for high-power traction applications.

Chowdhury, Shajjad↗
DOE OSTI2024

STUDIES ON PIPELINE POLYETHYLENES IN HYDROGEN GAS ENVIRONMENTS USING IN-SITU AND EX-SITU CHARACTERIZATION METHODS

Polymeric materials are commonplace in the natural gas infrastructure as distribution pipes, coatings, seals, and gaskets. Under the auspices of the U.S. Department of Energy HyBlend program, one of the means to reduce greenhouse gas emissions is with replacing natural gas, either partially or completely, with hydrogen. This approach makes it imperative that we conduct near-term and long-term materials compatibility research in these relevant environments. Insights into the effects of hydrogen and hydrogen gas blends on polymer integrity can be gained through both ex-situ and in-situ analytical methods. Our work represented here highlights a study of the behavior of pipeline polyethylene (PE) materials, including HDPE (Dow 2490 and GDB50) and MDPE (Ineos and legacy Dupont Aldyl A), when exposed to hydrogen by means of in-situ X-ray scattering and ex-situ Raman spectroscopy techniques. Samples were tested in ex-situ hydrogen and argon gas environments and in-situ hydrogen environments to identify differences due to permeation and solubility of these gases. These methods complemented each other because Raman spectroscopy could capture permanent effects after materials were removed from gaseous environments, and in-situ X-ray scattering analysis collected real-time data to elucidate the impact of the gas environment on polymer microstructure. Data collected revealed that the aforementioned polymers did not show significant changes in crystallinity and microstructure under the exposure conditions tested. Our findings from these studies will help establish real-time effects caused by hydrogen gas transport through pipeline polyethylenes by way of its influence on polymer structure and chemistry, which is directly related to pipeline mechanical strength and longevity of service.

Hydrogen materials compatibility, Natural gas pipe↗
DOE OSTI2020

Molecular compositions, materials, and methods for efficient multiple exciton generation

Embodiments of the present invention provides compounds, compositions, and methods for their preparation that provide efficient intramolecular fission, such that local order and strong nearest neighbor coupling is no longer a design constraint. Inventive materials include organic oligomers and polymers designed to exhibit strong intrachain donor-acceptor interactions and provide intramolecular singlet fission, whereby triplet populations can be generated in very high yields of, e.g., 170% or more. The inventive disclosure is directed to polymers of the general formula: [SA-SD]n with a strong electron acceptor (SA), a strong electron donor (SD), and n a positive integer equal to or greater than two; methods for their preparation and monomers used therein, blends, mixtures and formulations containing them; the use of the polymers, blends, mixtures and formulations as semiconductors in organic electronic (OE) devices, especially in organic photovoltaic (OPV) devices, and to OE and OPV devices comprising these polymers, blends, mixtures or formulations.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Counterintuitive Compatibilization of Poly(-Valerolactone) and Poly(L-Lactic Acid) by Statistical Copolymers toward Compostable and Recyclable Packaging

Poly(δ-valerolactone) (PVL) and poly(l-lactic acid) (PLLA) are bioderivable, compostable, and chemically recyclable plastics with synergistic properties for addressing plastic waste accumulation in receiving environments. Though recyclable-by-design polymers often fall short of competing with incumbent materials, blending affords a means to leverage individual component strengths toward ideal tunable properties. Polymer blends are often immiscible, but a range of methodologies are available to promote mixing. Here, we report on the compatibilization of 9 immiscible PVL and PLLA blends with three different compatibilization agents: thermoplastic starch, synthesized PVL-co-PLLA statistical copolymers (SCPs), and synthesized PVL-b-PLLA block-type copolymers. Resulting degrees of compatibilization are observed through scanning electron microscopy, corroborated by thermal and mechanical analyses monitoring performance as a function of microdomain size. Small-angle and wide-angle X-ray scattering experiments are conducted to observe the influence of compatibilizers on individual crystalline phases to further elucidate material behavior. Molecular dynamics simulations provide key insights into the interfacial interactions between homopolymers and compatibilizers. Finally, a suite of end-of-life avenues is established by biodegradation in industrial composting conditions, chemical recycling by deconstruction to hydroxymethyl esters, and direct chemical depolymerization to lactone precursors in mixed feed. Overall, we highlight several promising blends and the counterintuitive SCP compatibilization phenomenon toward high-performance, sustainable materials.

Compatibilization, copolymer compatibilizer, bio-b↗
DOE OSTI2024

Impact of Dilute DIO Additive on Local Microstructure of Fluorinated, pNDI‐Based Polymer Solar Cells

The performance of all‐polymer solar cells is often enhanced by incorporating solvent additives during solution processing. Here, in particular, blends based on the model all‐polymer system PBDBT:N2200 have been shown to have increased short‐circuit current and fill factor when processed with dilute diiodooctane (DIO). However, the morphological mechanism that drives the increase in performance is often not well understood due to limitations in common characterization techniques. In this study, it is shown that a combination of X‐ray techniques with cryogenic high‐resolution transmission electron microscopy (HRTEM) analysis can provide a quantitative and spatially resolved picture of polymer chain orientation and alignment in all‐polymer blends. It is found that DIO induces vertical phase separation in PBDBT‐2F:F‐N2200 and increases donor crystallite thickness in the pi‐stacking direction leading to an acceptor‐rich film surface. However, it is also shown that DIO does not disrupt the formation of face‐on donor–acceptor interfaces. These findings suggest that dilute DIO primarily affects crystalline domain formation in single component regions as opposed to mixed regions; thus, dilute DIO can impact vertical charge transport pathways without sacrificing donor–acceptor interfacial connectivity.

Cheng, Christina↗
DOE OSTI2022

Recycling of Pretreated Polyolefin-Based Ocean-Bound Plastic Waste by Incorporating Clay and Rubber

Plastic waste found in oceans has become a major concern because of its impact on marine organisms and human health. There is significant global interest in recycling these materials, but their reclamation, sorting, cleaning, and reprocessing, along with the degradation that occurs in the natural environment, all make it difficult to achieve high quality recycled resins from ocean plastic waste. To mitigate these limitations, various additives including clay and rubber were explored. In this study, we compounded different types of ocean-bound (o-HDPE and o-PP) and virgin polymers (v-LDPE and v-PS) with various additives including a functionalized clay, styrene-multi-block-copolymer (SMB), and ethylene-propylene-based rubber (EPR). Physical observation showed that all blends containing PS were brittle due to the weak interfaces between the polyolefin regions and the PS domains within the polymer blend matrix. Blends containing clay showed rough surfaces and brittleness because of the non-uniform distribution of clay particles in the polymer matrix. To evaluate the properties and compatibility of the blends, characterizations using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and small-amplitude oscillatory shear (SAOS) rheology were carried out. The polymer blend (v-LDPE, o-HDPE, o-PP) containing EPR showed improved elasticity. Incorporating additives such as rubber could improve the mechanical properties of polymer blends for recycling purposes.

42 ENGINEERING↗