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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes

Propylene carbonate (PC) is seldom used in lithium-ion batteries (LIBs) due to its sustained co-intercalation into graphene structure and the eventual graphite exfoliation, despite potential advantages it brings, such as wider liquid range and lower cost. Here we discover that cesium cation (Cs+), originally used to suppress dendrite growth of Li metal anode, directs the formation of solid electrolyte interphase (SEI) on graphitic anode in PC-rich electrolytes through preferential solvation. Effective suppression of PC-decomposition and graphite-exfoliation was achieved when the ratio of ethylene carbonate (EC)/PC in electrolytes was so adjusted that the reductive decomposition of Cs+-(EC)m (1≤m≤2) complex precedes that of Li+-(PC)n (3≤n≤5). The interphase directed by Cs+ is stable, ultrathin and compact, leading to significant improvements in LIB performances. In a broader context, the accurate tailoring of SEI chemical composition by introducing a new solvation center represents a fundamental breakthrough in manipulating interfacial reactions processes that once were elusive.

cesium cation↗
DOE OSTI2021

Molecular Engineering to Enable High-Voltage Lithium-Ion Battery: From Propylene Carbonate to Trifluoropropylene Carbonate

Molecular engineering of electrolyte structures has led to the successful application of trifluoropropylene carbonate (TFPC), a fluorinated derivative of propylene carbonate (PC), in next-generation high-voltage high-energy lithium-ion cell. Additionally, in contrast to a PC-based electrolyte which cointercalates in the form of Li + -solvated species into the graphene layer and exfoliates a graphite anode, a TFPC-based electrolyte is highly compatible with a graphite anode at low potential. Additionally, it shows exceptional oxidation stability on the charged cathode surface owing to the presence of the -CF 3 group. An all-fluorinated electrolyte, that is, 1.0 M LiPF 6 TFPC/2,2,2-trifluoroethyl carbonate (FEMC) (1/1 volume ratio) + FEC additive, was formulated and demonstrated excellent cycling stability in a high-voltage LiNi 0.5 Mn 0.3 Co 0.2 O 2 /graphite cell cycled between 3.0 and 4.6 V.

25 ENERGY STORAGE↗
DOE OSTI2011

Wide-Angle X-ray Scattering Study on Shear-Induced Crystallization of Propylene-1-Butylene Random Copolymer: Experiment and Diffraction Pattern Simulation

Shear-induced crystallization of a propylene-1-butylene random copolymer with low butylene content (5.7 mol %) was studied using time-resolved wide-angle X-ray scattering (WAXS) techniques. Polymorphism, preferred crystal orientation, crystallization kinetics, and disorder effect were investigated based on WAXS 2D whole pattern analysis. It was found that at 100 C, the crystallite of P-B copolymer was a mixture of 80% {gamma}-form and 20% {alpha}-form of isotactic polypropylene (iPP) crystals. The application of a step shear (shear rate = 100 s{sup -1}, shear duration =3s) induced {gamma}-form crystals with c-axis oriented perpendicular to the shear direction. In contrast, the c-axis of {alpha}-form crystals was normally in parallel to the shear direction. Both crystallization kinetics and crystallinity were greatly enhanced by shear. The disorder effect was found to play an important role in the crystallization behavior of P-B copolymer. In the early stage crystallization, the chosen copolymer contained a large amount of structure defects, where crystals became more ordered upon annealing. The degree of crystal orientation was also found to decrease during crystallization due to the relaxation after shear.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Homopolymer self-assembly of poly(propylene sulfone) hydrogels via dynamic noncovalent sulfone-sulfone bonding

Natural biomolecules such as peptides and DNA can dynamically self-organize into diverse hierarchical structures. Mimicry of this homopolymer self-assembly using synthetic systems has remained limited but would be advantageous for the design of adaptive bio/nanomaterials. Here, we report both experiments and simulations on the dynamic network self-assembly and subsequent collapse of the synthetic homopolymer poly(propylene sulfone). The assembly is directed by dynamic noncovalent sulfone–sulfone bonds that are susceptible to solvent polarity. The hydration history, specified by the stepwise increase in water ratio within lower polarity water-miscible solvents like dimethylsulfoxide, controls the homopolymer assembly into crystalline frameworks or uniform nanostructured hydrogels of spherical, vesicular, or cylindrical morphologies. These electrostatic hydrogels have a high affinity for a wide range of organic solutes, achieving >95% encapsulation efficiency for hydrophilic small molecules and biologics. This system validates sulfone–sulfone bonding for dynamic self-assembly, presenting a robust platform for controllable gelation, nanofabrication, and molecular encapsulation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

X-ray absorption spectroscopy of LiBF 4 in propylene carbonate. A model lithium ion battery electrolyte

Since their introduction into the commercial marketplace in 1991, lithium ion batteries have become increasingly ubiquitous in portable technology. Nevertheless, improvements to existing battery technology are necessary to expand their utility for larger-scale applications, such as electric vehicles. Advances may be realized from improvements to the liquid electrolyte; however, current understanding of the liquid structure and properties remains incomplete. X-ray absorption spectroscopy of solutions of LiBF 4 in propylene carbonate (PC), interpreted using first-principles electronic structure calculations within the eXcited electron and Core Hole (XCH) approximation, yields new insight into the solvation structure of the Li + ion in this model electrolyte. By generating linear combinations of the computed spectra of Li + -associating and free PC molecules and comparing to the experimental spectrum, we find a Li + –solvent interaction number of 4.5. This result suggests that computational models of lithium ion battery electrolytes should move beyond tetrahedral coordination structures.

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

Boron-hyperdoped silicon for the selective oxidative dehydrogenation of propane to propylene

Boron containing catalysts have great potential in the oxidative dehydrogenation of propane. Herein, a series of 15, 25 and 42 at% boron-hyperdoped silicon catalysts synthesized by laser pyrolysis was studied. Here, boron-hyperdoped silicon samples showed >6 times higher propylene productivity than commercial h-BN at 450 °C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

NMR T{sub 1} relaxation time measurements and calculations with translational and rotational components for liquid electrolytes containing LiBF{sub 4} and propylene carbonate

Longitudinal relaxation (T{sub 1}) measurements of {sup 19}F, {sup 7}Li, and {sup 1}H in propylene carbonate/LiBF{sub 4} liquid electrolytes are reported. Comparison of T{sub 1} values with those for the transverse relaxation time (T{sub 2}) confirm that the measurements are in the high temperature (low correlation time) limit of the T{sub 1} minimum. Using data from pulsed field gradient measurements of self-diffusion coefficients and measurements of solution viscosity measured elsewhere, it is concluded that although in general there are contributions to T{sub 1} from both translational and rotational motions. For the lithium ions, this is mainly translational, and for the fluorine ions mainly rotational.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Detection of diffusion limited oxidation in thermally aged ethylene propylene rubber cable insulation material

The lifetime prediction of electrical cable insulation in nuclear power plants (NPPs) is primarily based on accelerated aging. Polymeric insulation exposed to accelerated aging at high temperatures may demonstrate diffusion limited oxidation (DLO) where oxygen within the material is consumed faster than can be supplied by diffusion from the surrounding air. This situation leads to equilibrium oxidation at the exposed surfaces and limited oxidation away from the surfaces. Therefore, DLO results in a heterogeneously aged material which can lead to underestimation of lifetime for in-service cable insulation. In this study, the presence of inhomogeneous aging caused by DLO was evaluated on cross-sectioned cable insulation specimens made of ethylene propylene rubber (EPR). The studies were performed on thermally aged specimens (165 °C, 1 day and 165 °C, 16 days) using local measurement techniques including nanoindentation, micro-Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) - energy dispersive spectroscopy (EDS). All the results indicate some degree of heterogenous aging, with 165 °C, 16 days, aging demonstrating highest degree of oxidative degradation on the inside edges presumably caused due to copper catalyzed oxidation.

Pallaka, Madhusudhan Reddy↗
DOE OSTI2025

Effect of Transverse Compression on the Dielectric Breakdown of Power Cable with Ethylene Propylene Rubber Insulation

Understanding of the failure mechanisms of submarine dynamic power cables (SDPC) is critical for innovative design to meet the 2035 cost reduction target of U.S. DOE Floating Offshore Wind Shot. This is important because the current design suffers a significant failure rate in the field. This project explored a multiphysics approach and conducted systematic electro-thermo-mechanical (ETM) experimental study on the power cores extracted from a 15 kV power cable. The power cable had three cores of copper conductor and ethylene propylene rubber (EPR) insulation. An ETM testing system with transverse compression capability was developed. Mechanical loading induced dielectric breakdown. Increasing temperature from room temperature (RT, 22 degrees Celsius) to 90 degrees Celsius resulted in the 67% decrease in the failure mechanical load as defined by the dielectric breakdown. With the same temperature rise, the creep mechanical load was reduced by 70% at a given dielectric breakdown time. The post-test measurement revealed an impressive recovery of electrical resistance, although the dielectric breakdown occurred in the ETM test that would not be captured without the use of ETM testing.

Wang, Hong [ORNL] (ORCID:0000000201730545)↗
DOE OSTI2021

Highly Concentrated Electrolytes: Electrochemical and Physicochemical Characteristics of LiPF 6 in Propylene Carbonate Solutions

Highly concentrated electrolytes (HCEs) based on LiPF 6 in propylene carbonate (PC) have been examined as lithium-ion battery electrolytes. These HCEs have lower ionic conductivities and higher viscosities than ethylene carbonate (EC) electrolytes with 1.2 M LiPF 6 , but they have higher Li + ion transference numbers. Electrochemical cycling behaviour of LiNi 0.8 Co 0.015 Al 0.05 O 2 //graphite cells with 3.2 M LiPF 6 in PC resembles that of cells with EC-based electrolytes; the HCE cells have higher impedance, which can be lowered by increasing test temperature. By employing Raman and infrared spectroscopy, combined with density functional theory and ab initio molecular dynamics simulations, we reveal that the Li + solvation structure and speciation are key factors that determine cell performance. Two distinct regimes are observed as a function of salt concentration—in the conventional regime, the solvation number (SN) is mostly constant, while in the HCE regime it decreases linearly. Graphite exfoliation is suppressed only at very high salt concentrations ( > 2.4 M), where [ PC ] free /[Li + ] < 1 and P F 6 − f r e e > P C f r e e . Results from the Advanced Electrolyte Model indicate that Li + desolvation improves at higher LiPF 6 concentrations, thereby mitigating PC co-intercalation into the graphite. However, Li + ion transport is hindered in the HCEs, which increases impedance at both the oxide-positive and graphite-negative electrodes.

25 ENERGY STORAGE↗
DOE OSTI2016

Development of a reduced tri-propylene glycol monomethyl ether– n -hexadecane–poly-aromatic hydrocarbon mechanism and its application for soot prediction

A reduced chemical kinetic mechanism for Tri-Propylene Glycol Monomethyl Ether (TPGME) has been developed and applied to computational fluid dynamics (CFD) calculations for predicting combustion and soot formation processes. The reduced TPGME mechanism was combined with a reduced n-hexadecane mechanism and a Poly-Aromatic Hydrocarbon (PAH) mechanism to investigate the effect of fuel oxygenation on combustion and soot emissions. The final version of the TPGME-n-hexadecane-PAH mechanism consists of 144 species and 730 reactions and was validated with experiments in shock tubes as well as in a constant volume spray combustion vessel (CVCV) from the Engine Combustion Network (ECN). The effects of ambient temperature, varying oxygen content in the tested fuels on ignition delay, spray liftoff length and soot formation under diesel-like conditions were analyzed and addressed using multidimensional reacting flow simulations and the reduced mechanism. Here, the results show that the present reduced mechanism gives reliable predictions of the combustion characteristics and soot formation processes. In the CVCV simulations, two important trends were identified. First, increasing the initial temperature in the CVCV shortens the ignition delay and lift-off length, reduces the fuel-air mixing, thereby increasing the soot levels. Secondly, fuel oxygenation introduces more oxygen into the central region of a fuel jet and reduces residence times of fuel rich area in active soot forming regions, thereby reducing soot levels.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

Progress in Characterizing Thermal Degradation of Ethylene-Propylene Rubber

Ethylene-propylene rubber (EPR) is one of the two most common nuclear cable insulation materials. A large fraction of EPR-insulated cables in use in the nuclear industry were manufactured by The Okonite Company. Okoguard® is the name of the medium voltage thermoset EPR manufactured by The Okonite Company. Okoguard® has been produced with silane-treated clay filler and the characteristic pink color since the 1970’s. EPR is complex material that undergoes simultaneous reactions during thermal aging including oxidative and thermal cleavage and oxidative and thermal crosslinking. This reaction complexity makes precise EPR service life prediction from accelerated aging using approaches designed for single discreet reactions such as the Arrhenius approach problematic. Performance data and activation energies for EPR aged at conditions closer to service conditions will improve EPR lifetime prediction. In this report pink Okoguard® EPR insulation material has been thermally aged at elevated temperatures. A variety of characterization techniques have been employed to track material changes with aging. It was noted that EPR aged significant departure in aging behavior seemed to occur at accelerated aging temperatures between 140°C and 150°C at around 20 days of exposure. This may be due to alternative degradation mechanisms being accessed at this higher temperature and reinforces the need to perform accelerated aging for Okoguard® EPR service life prediction at temperatures below 150°C.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Initiation of Experimental Campaign to Address Knowledge Gaps Related to Simultaneous Thermal and Gamma Radiation Aging of Crosslinked Polyethylene and Ethylene-Propylene Rubber Cable Insulation

Key cable knowledge gaps identified in the Expanded Materials Degradation Assessment (EMDA) volume on Aging of Cables and Cable Systems (Volume 5) specifically relate to the combined effects of thermal and gamma irradiation stresses on cable insulation materials. These include dose rate effects (DRE), inverse temperature effects (ITE), and synergistic effects (S/E). Extent of radiation-induced polymer degradation is proportional to absorbed dose, but DRE describe the phenomenon in which degree of damage is based not only on total dose, but also on the dose rate experienced during dose accumulation. This can be particularly complicated in the presence of thermal stress as a material spends more time at elevated temperature to receive the same total dose at a lower dose rate. Rates of cable polymer degradation generally increases with temperature, but ITE describes the situation in which polymer material damage under irradiation is greater at lower temperatures than at higher temperatures. Finally, S/E describe the concept that the mechanism of polymer material degradation when exposed to thermal aging and radiation aging in succession may be different than when exposed to thermal and radiation aging concurrently. The experimental campaign at the Pacific Northwest National Laboratory (PNNL) described in this report seeks to address these knowledge gaps through investigation of the degradation of relevant cable insulation materials at select conditions using controlled temperatures, dose rates and total doses. Insulation materials considered were chosen to represent those most commonly found in U.S. nuclear power plants in terms of manufacturers and polymer systems. They include products from manufactures including The Rockbestos Company; The Okonite Company; Boston Insulated Wire & Cable Company; Kerite Company; Anaconda Company; Brand Rex, Inc.; and Samuel Moore Company. The products include the most ubiquitous cross-linked polyethylene (XLPE) and ethylene-propylene rubber (EPR) classes of insulation polymer. Circulating air ovens with remote temperature sensing and control are positioned within the gamma irradiation beam to enable controlled temperatures during radiation exposure. Dose rates are controlled through repeatable positioning of specimens at determined distances from the Cobalt-60 gamma source. Total absorbed doses for comparing temperature and dose rate effects are controlled by removing samples from exposure at pre-determined time points. The effects of gamma beam geometry, source decay and attenuation due to samples, ovens and racks are determined and controlled for using local point dosimetry. The temperature, dose and dose rates selected for the experimental campaign described in this report were determined following input from a range of stakeholders and intended to balance the constraints of the experimental capabilities, available material, project timeline and project funding with the value of the effort in narrowing EMDA-identified knowledge gaps. Results from this campaign are anticipated to reduce uncertainty in the understanding of cable material degradation behavior in nuclear power plant environments and thereby support cable aging management in long term operation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

Atomistic Materials Modeling of High-Pressure Hydrogen Interactions in Ethylene Propylene Diene Monomer (EPDM) Rubber

Elastomeric rubbers serve a vital role as sealing materials in the hydrogen storage and transport infrastructure. With applications including O-rings and hose-liners, these components are exposed to pressurized hydrogen at a range of temperatures, cycling rates, and pressure extremes. Cyclic (de)pressurization is known to degrade these materials through the process of cavitation. This readily visible failure mode occurs as a fracture or rupture of the material and is due to the oversaturated gas localizing to form gas bubbles. Computational modeling in the Hydrogen Materials Compatibility Program (H-Mat), co-led by Sandia National Laboratories and Pacific Northwest National Laboratory, employs multi-scale simulation efforts to build a predictive understanding of hydrogen-induced damage in materials. Modeling efforts within the project aim to provide insight into how to formulate materials that are less sensitive to high-pressure hydrogen-induced failure. In this document, we summarize results from atomistic molecular dynamics simulations, which make predictive assessments of the effects of compositional variations in the commonly used elastomer, ethylene propylene diene monomer (EPDM).

08 HYDROGEN↗
DOE OSTI2021

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

Presented at the NETL Project Review Meetings (virtual) in 2021, the presentation summary includes the following status updates: -Initiated synthesis, characterization and testing of various supported metal catalysts -Some catalysts show greater than 90% propylene selectivity -Plasma testing shows greater than 80% propane conversion without a catalyst -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

Zhou, S. James↗
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↗