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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Post Irradiation Examination Results of the NT-02 Graphite Fins NUMI Target

The NT-02 neutrino target in the NuMI beamline at Fermilab is a 95 cm long target made up of segmented graphite fins. It is the longest running NuMI target, which operated with a 120 GeV proton beam with maximum power of 340 kW, and saw an integrated total proton on target of 6.1 1020. Over the last half of its life, gradual degradation of neutrino yield was observed until the target was replaced. The probable causes for the target performance degradation are attributed to radiation damage, possibly including cracking caused by reduction in thermal shock resistance, as well as potential localized oxidation in the heated region of the target. Understanding the long-termstructural response of target materials exposed to proton irradiation is critical as future proton accelerator sources are becoming increasingly more powerful. As a result, an autopsy of the target was carried out to facilitate post-irradiation examination of selected graphite fins. Advanced microstructural imaging and surface elemental analysis techniques were used to characterize the condition of the fins in an effort to identify degradation mechanisms, and the relevant findings are presented in this paper.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Long Baseline Neutrino Experiment (LBNE) Target Material Radiation Damage from Energetic Protons of the Brookhaven Linear Isotope Production (BLIP) Facility

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) various grades of graphite were irradiated with 140-180 MeV protons to fluence up to ~6 10 20 cm -2 and irradiation temperatures in the range of 100-200oC. The objective of the irradiation experiment was to assess the radiation induced changes in the graphite onset by its interaction with energetic protons and deduce some measure of performance and survivability under the design conditions of LBNF. A multi-faceted post-irradiation evaluation was conducted to both qualify and quantify the induced material property changes. These studies included dimensional stability and thermal expansion, damage annealing via thermal cycling, high temperature post-irradiation annealing to mimic irradiation at elevated temperatures, stress-strain behavior, oxidation contribution to the postirradiation analysis, potential influence of the argon atmosphere under which irradiation took place, and lattice evolution. Dilatometry-based techniques were coupled with ultrasound-based annealing methodologies as well as DSC and TGA analyses. X-ray diffraction experiments assessed the lattice parameter changes and SEM analyses were used to study the different graphite grade structures. The multi-faceted post-irradiation evaluation, in conjunction with off-beam analyses, revealed some important facts regarding the choice of a graphite grade. Specifically, it was observed that the microstructure of a grade plays an important role in its dimensional stability. X-ray diffraction data indicated variability in basal plane spacing prior to irradiation with POCO d 002 =3.3833 Å, IG-430 d 002 =3.36814 Å and R7650 d 002 =3.37944 Å. Isotropic graphite grades such as POCO and IG-430 are confirmed to undergo microstructural shrinking under irradiation. All four irradiated graphite grades experience irradiation-induced creep leading to increased Young’s modulus with changes as high as 50% that varies with microstructure. X-ray diffraction on irradiated graphite confirmed previously made observations where under both energetic protons as well as fast neutrons of fluence > 5 10 20 cm -2 and at temperatures around 200°C acceleration of the effects on both the micro-and macrostructure is observed. Amongst the irradiated grades POCO graphite showed tendency to increase crystallinity order but also shows turbostratic state resulting from the interaction of its lattice with protons. This report presents and discusses the details of the irradiation experiment and the results of the postirradiation evaluation with main objective the assessment of the applicability and survivability of the selected four graphite grades as high-power accelerators pion production targets where the structural integrity, density reduction, dimensional and physical property stability are of paramount importance.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Spectroscopic insight into carbon speciation and removal on a Cu/BEA catalyst during renewable high-octane hydrocarbon synthesis

Conversion of methanol and dimethyl ether (DME) to high-octane gasoline catalyzed by beta zeolite (BEA) provides an opportunity for the production of high-quality fuels from renewable carbon sources (e.g., gasified biomass). Recent research demonstrated that a Cu-modified BEA zeolite catalyst (Cu/BEA) offered advantages over the unmodified BEA catalyst due to multifunctional Cu species that enabled incorporation of co-fed H2, reactivation of light alkanes, and reduction of products from the aromatic hydrocarbon pool. The shift in hydrocarbon pool chemistry has the potential to influence the identity and relative composition of surface carbon species that are often linked to deactivation. A detailed understanding of these carbon species is important to develop an effective and efficient regeneration procedure that can enable the transition from fundamental catalyst development to commercial application. Here, we applied complementary ex situ and in situ characterization techniques to compare the structures of surface carbon species on post-reaction Cu/BEA and unmodified BEA catalysts. Both catalysts contained acyclic and aromatic hydrocarbons along with graphitic carbon species. However, the post-reaction Cu/BEA catalyst had a lower polycyclic aromatic content, and further, the graphitic species were more hydrogenated and defective. It was also found that the presence of Cu promoted carbon removal at lower temperatures than for unmodified BEA through activation of O2 by Cu oxide during thermal oxidation. The fundamental insight into the composition of surface carbon species enabled the design of an effective and efficient regeneration strategy for the DME homologation reaction over Cu/BEA, resulting in full recovery of the catalyst activity.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

Structure and energetics of SiOC and SiOC ‐modified carbon‐bonded carbon fiber composites

Abstract The incorporation of SiOC polymer‐derived ceramics into porous carbon materials could provide tailored shapeable, mechanical, electrical, and oxidation‐resistant properties for high‐temperature applications. Understanding the thermodynamic and kinetic stability of such materials is crucial for their practical application. We report here the dependence of structures and energetics of SiOC and SiOC ‐modified carbon‐bonded carbon fiber composites ( CBCFs ) on the pyrolysis temperature using spectroscopic methods and high‐temperature oxide melt solution calorimetry. The results indicate that a SiOC ceramic pyrolyzed at 1200°C and 1600°C is energetically stable with respect to an isocompositional mixture of cristobalite, silicon carbide, and graphite by 4.9 and 10.3 kJ/mol, respectively, and more energetically stable than that pyrolyzed at 1450°C. Their thermodynamic stability is related to their structural evolution. SiOC ‐modified CBCF s become energetically less stable with increasing preparation temperature and concomitant increase in excess carbon content.

Niu, Min↗
NASA NTRS1993

Oxidation during metamorphism of the ordinary chondrites

It is suggested that some current concepts about the conditions of metamorphism in ordinary chondrites may be flawed. These meteorites display small systematic variations in the oxidation state of Fe. Evidence is presented that oxidation of Fe is linked to metamorphic grade in types 4-6 ordinary chondrites. This conclusion is at variance with a commonly accepted model for chondrite metamorphism that assumes Fe reduction by graphite.

Mcsween, Harry Y., Jr.↗
DOE OSTI2017

Post Irradiation Examination Results of the NT-02 Graphite Fins NuMI Target

The NT-02 neutrino target in the NuMI beamline at Fermilab is a 95 cm long target made up of segmented graphite fins. It is the longest running NuMI target, which operated with a 120 GeV proton beam with maximum power of 340 kW and saw an integrated total proton on target of 6.1 x 10^20. Over the last half of its life, gradual degradation of neutrino yield was observed until the target was replaced. The probable causes for the target performance degradation are attributed to radiation damage, possibly including cracking caused by reduction in thermal shock resistance, as well as potential localized oxidation in the heated region of the target. Understanding the long-term structural response of target materials exposed to proton irradiation is critical as future proton accelerator sources are becoming increasingly more powerful. As a result, an autopsy of the target was carried out to facilitate post-irradiation examination of selected graphite fins. Advanced microstructural imaging and surface elemental analysis techniques were used to characterize the condition of the fins in an effort to identify degradation mechanisms, and the relevant findings are presented in this paper.

Accelerator, Target, Graphite, NuMI, FermiLab, Neu↗
DOE OSTI2020

Long-Term Cyclability of NCM-811 at High Voltages in Lithium-Ion Batteries: an In-Depth Diagnostic Study

High-nickel layered oxides, such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM-811), offer higher energy density than their low-nickel counterparts at a given voltage and are gaining major traction in automotive lithium-ion batteries for electric vehicles. Besides high-Ni content, higher charging voltages above 4.3 V vs Li + /Li boost the energy and represent another focus in battery development. Here, we investigate the long-term cyclability of NCM-811 in graphite pouch cells over 1000 deep cycles between 2.5–4.2, 2.5–4.4, and 2.5–4.5 V through a suite of sensitive characterization techniques. The NCM-811 full cells show severely deteriorated cyclability with higher charging voltages, from 78% at 4.2 V to 52 and 32% at 4.4 and 4.5 V, respectively. At 4.2 V, minor parasitic electrolyte oxidation as well as cathode Li/Ni mixing and cracking are revealed after cycling, while transition-metal dissolution and surface reconstruction into rock-salt NiO are virtually undetectable. At 4.4 and 4.5 V, transition-metal dissolution and crossover to the anode become much more pronounced and a primary contributor to the capacity fade, while significant surface NiO formation causes substantial voltage polarization, which is less noticeable at 4.2 V. Meanwhile, more severe electrolyte oxidation, Li/Ni mixing, and particle pulverization exacerbate the voltage and capacity fade. Finally, these results outline distinct challenges for stable high-Ni layered oxide cathodes in high-voltage Li-ion batteries.

25 ENERGY STORAGE↗
NASA NTRS1990

Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various continuous fibers

An experimental study was conducted to measure the thermooxidative stability of PMR-15 composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers studied include graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight-loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

Bowles, Kenneth J.↗
DOE OSTI2018

The Influence of Artificial Photodegradation on Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)/Graphite Nanosheets (GNS) Nanocomposites

The potential use of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/graphite nanosheets (GNS) as a biodegradable nanocomposite has been explored. PHBV/GNS nanocomposites films were prepared by solution casting at various concentrations of GNS—0.25, 0.50 and 1.00 wt% GNS. The films were exposed to artificial ultraviolet radiation (UV) during 52 h. The effect of GNS on PHBV photodegradation was investigated and compared to neat PHBV film. The artificial photodegradation induced changes in physical (weight loss), chemical carbonyl index by Fourier transform infrared spectroscopy, thermal degree of crystallinity and melting temperature by differential scanning calorimetry and morphological scanning electron microscopy characteristics. Based on the results obtained from aforementioned analyzes it was verified that GNS inhibits the oxidative degradation of PHBV matrix.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Toward a high-voltage fast-charging pouch cell with TiO 2 cathode coating and enhanced battery safety

Nickel-rich layered lithium transition metal oxides, LiNi x Co y Mn 1-x-y O 2 , are key cathode materials for high-energy lithium-ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides has been hampered by their poor thermostability and insufficient cycle life. In this work full batteries with uncoated and TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathodes and graphite anodes are compared in terms of electrochemical performance and safety behavior. The battery using a TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode exhibited better cyclic performance at high cutoff voltage. Electrochemical impedance spectroscopy analysis indicated that the TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode gave the battery a more stable charge transfer resistance. Transmission electron microscopy demonstrated that TiO 2 coating reduced accumulation of the cathode electrolyte interface layer on the particle surface. Time-of-flight secondary ion mass spectrometry demonstrated that TiO 2 coating markedly enhanced the interface stability of the cathode particle and protected the particle from serious etching by the electrolyte. Accelerating rate calorimetry revealed that the trigger temperature of thermal runaway for the battery using TiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 as cathode material was 257 °C, which was higher than that of the battery with the uncoated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode (251 °C). In situ X-ray diffraction during heating demonstrated that this enhanced safety can be attributed to the suppressed phase evolution of the coated cathode material.

25 ENERGY STORAGE↗
NASA NTRS1972

Thermal testing techniques for space shuttle thermal protection system panels

An experimental system was developed for evaluation of the effects of aerodynamic heating and cooling, vacuum, and pressure loading on candidate insulation packages proposed for use on the space shuttle. The system includes a number of design features which facilitate rapid recycle times. This is necessary to efficiently conduct extensive thermal cycling tests on these insulation packages to determine their reuse capabilities. The heart of the system is a 26-inch graphite element radiant heater. A susceptor plate functions as a uniform-temperature intermediate radiating surface. The susceptor also forms the lid of an inert atmosphere enclosure which separates the heater from the oxidizing test atmosphere. In some tests the plate properly simulates the heating from an actual flight heat-shield panel. Although other materials were used at lower required test temperatures, 2500 F was routinely achieved using a coated columbium susceptor plate.

Cox, B. G.↗
DOE OSTI2016

Asphaltene based photovoltaic devices

Photovoltaic devices and methods of making the same, are disclosed herein. The cell comprises a photovoltaic device that comprises a first electrically conductive layer comprising a photo-sensitized electrode; at least one photoelectrochemical layer comprising metal-oxide particles, an electrolyte solution comprising at least one asphaltene fraction, wherein the metal-oxide particles are optionally dispersed in a surfactant; and a second electrically conductive layer comprising a counter-electrode, wherein the second electrically conductive layer comprises one or more conductive elements comprising carbon, graphite, soot, carbon allotropes or any combinations thereof.

14 SOLAR ENERGY↗
DOE OSTI2017

Sulfur redox reactions on nanostructured highly oriented pyrolytic graphite (HOPG) electrodes: Direct evidence for superior electrocatalytic performance on defect sites

Fundamental research of sulfur redox reactions on well-defined controlled model electrode surfaces can provide new information to design high-performance lithium-sulfur batteries. In this paper, we study the electrochemical reduction and oxidation of sulfur on the nanostructured HOPG electrodes with pure basal planes, step plans, and pure edge planes. Finally, our results directly indicate that electrochemical reduction and oxidation of sulfur is significantly affected by the carbon surface structure, namely, the electrochemical reversibility of sulfur redox reaction is much better on edge plane, compared with basal plane and step plane.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Stoichiometric Layered Potassium Transition Metal Oxide for Rechargeable Potassium Batteries

K-ion batteries are promising alternative energy storage systems for large-scale applications because of the globally abundant K reserves. K-ion batteries benefit from the lower standard redox potential of K/K + than that of Na/Na + and even Li/Li + , which can translate into a higher working voltage. Stable KC 8 can also be formed via K intercalation into a graphite anode, which contrasts with the thermodynamically unfavorable Na intercalation into graphite, making graphite a readily available anode for K-ion battery technology. However, to construct practical rocking-chair K-ion batteries, an appropriate cathode material that can accommodate reversible K release and storage is still needed. We show that stoichiometric KCrO 2 with a layered O 3 -type structure can function as a cathode for K-ion batteries and demonstrate a practical rocking-chair K-ion battery. In situ X-ray diffraction and electrochemical titration demonstrate that KxCrO 2 is stable for a wide K content, allowing for topotactic K extraction and reinsertion. We further explain why stoichiometric KCrO 2 is unique in forming the layered structure unlike other stoichiometric K-transition metal oxide compounds, which form nonlayered structures; this fundamental understanding provides insight for the future design of other layered cathodes for K-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Interface-engineered (AlMnCoNiZn) 3 O 4 @PPy nanocomposites for superior lithium storage: Mechanism and performance

The practical application of graphite anodes in lithium-ion batteries (LIBs) is constrained by low specific capacity (372 mAh g -1 ) and sluggish kinetics. Here, to address these limitations, our present study focuses on high-entropy oxides (HEOs), which offer high theoretical capacity and structural stability. We synthesized spinel-structured (AlMnCoNiZn) 3 O 4 nanoparticles via a solution combustion method and fabricated an (AlMnCoNiZn) 3 O 4 @polypyrrole (PPy) nanocomposite through in-situ polymerization. Our electrochemical tests demonstrate that the PPy modification significantly enhances performance. While the pristine (AlMnCoNiZn) 3 O 4 delivered 445 mAh g −1 after 100 cycles at 100 mA g −1 and 350 mAh g −1 after 1000 cycles at 1000 mA g −1 , the (AlMnCoNiZn) 3 O 4 @PPy composite achieved 695 mAh g −1 after 100 cycles and maintained 675 mAh g −1 after 1000 cycles. Furthermore, the composite improved rate capacity at 1000 mA g −1 from 211 mAh g −1 to 403 mAh g −1 . This work highlights how conductive and flexible polymer modifications can dramatically improve the electrochemical properties of HEOs. The developed (AlMnCoNiZn) 3 O 4 @PPy composite provides a promising direction for designing advanced anodes to meet next-generation energy storage demands.

Anodes material↗
DOE OSTI2018

Study of reaction sequences during MSR synthesis of TiC by controlled ball milling of titanium and graphite

Highlights: • Insights on oxygen-bonded features formed during reactive ball milling • Evolution of off-stoichiometric TiC before ignition • Growth sequence of the TiC manifested as stacks and multilayers • Dual morphology of the MSR reaction product - Abstract: During reactive ball milling of Ti and C, mechanically induced self-propagating reaction (MSR) synthesis of TiC is reported to occur via a process including initial formation of small amounts of TiC prior to exothermic ignition, followed by MSR and the formation of stiochiometric TiC (Dorofeev et al., 2011; Oghenevweta et al., 2016 [1, 2]). However, both the chemical evolution and mechanisms of reaction and growth of TiC both prior to, during and after ignition are not fully understood. This research focuses on fundamental understanding of the reaction sequences during MSR synthesis of TiC from elemental Ti and C (graphite). Magnetically controlled ball milling of stoichiometric (1:1) powder mixtures of titanium (Ti) and graphite (C) was performed under He gas with the exothermic ignition point by determined via in-situ temperature measurement. X-ray diffraction, Scanning Transmission Electron Microscopy (STEM) with electron energy loss spectroscopy (EELS), Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were employed to interpret the reaction sequences. The reaction sequence involved the following: During milling prior to ignition, severely deformed Ti, spheriodised graphite and amorphous carbon forms, and minor amounts of off-stiochiometric nano-TiC{sub 1−x} crystals. In addition to the formation of TiC{sub 1−x}, XPS revealed the formation of oxide skins coating the surface regions of the milled powders. There is also an evolution towards stiochiometric TiC with increasing milling time. Immediately after ignition, a reacted product comprising a mixture of multi-layer stacks of thin TiC plates form, in addition to a matrix comprising large TiC particles which have been liquid phase sintered under the high local heat of reaction by thin layers of unreacted Ti. MSR occurs via a dual mechanism involving rapid growth of existing TiC, plus nucleation and growth of new TiC. High spatially resolved EELS combined with STEM revealed additional information about the inhomogeneous chemical environment of the milled powders.

36 MATERIALS SCIENCE↗
NASA NTRS1990

The effect of leveling coatings on the atomic oxygen durability of solar concentrator surfaces

Space power systems for Space Station Freedom will be exposed to the harsh environment of low earth orbit (LEO). Neutral atomic oxygen is the major constituent in LEO and has the potential of severely reducing the efficiency of solar dynamic power systems through degradation of the concentrator surfaces. Several transparent dielectric thin films have been found to provide atomic oxygen protection, but atomic oxygen undercutting at inherent defect sites is still a threat to solar dynamic power system survivability. Leveling coatings smooth microscopically rough surfaces, thus eliminating potential defect sites prone to oxidation attack on concentrator surfaces. The ability of leveling coatings to improve the atomic oxygen durability of concentrator surfaces was investigated. The application of a EPO-TEK 377 epoxy leveling coating on a graphite epoxy substrate resulted in an increase in solar specular reflectance, a decrease in the atomic oxygen defect density by an order of magnitude and a corresponding order of magnitude decrease in the percent loss of specular reflectance during atomic oxygen plasma ashing.

Degroh, Kim K.↗