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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Extending tetrahedral network similarity to carbon: A type-I carbon clathrate stabilized by boron

Clathrates are guest/host framework compounds composed of polyhedral cages, yet despite their prevalence among tetrahedral network formers, clathrates with a carbon host lattice remain unrealized synthetic targets. Here, we report a type-I carbon-based framework—a ubiquitous clathrate structure type found throughout compounds containing tetrahedral building blocks. Following a boron-stabilization scheme based on first-principles predictions in the Ca–B–C system at high pressure, type-I Ca 8 B x C 46−x (x ≈ 9) was synthesized in the archetypal $Pm\bar{3}n$ lattice with stability derived from substitutionally disordered boron atoms on hexagonal ring framework positions. The synthesized clathrate, which is recoverable to ambient conditions, expands topological network similarity across tetrahedral systems and opens possibilities for a broad family of diamond-like, carbon-based compounds with tunable properties based on the wide potential for guest/host-atom substitutions and framework versatility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Carbonate Management to Enable Energy- and Carbon-Efficient CO 2 Electrolysis (Final Technical Report)

The rapid growth and plummeting cost of solar energy have created great interest in using CO 2 electrolysis to produce chemical feedstocks and fuels such as carbon monoxide, ethylene, ethanol, and propanol. While research in CO 2 electrolysis has yielded substantial progress in both fundamental understanding of the requisite electrocatalytic reactions and design of prototype devices, the energy efficiency (electrical energy to-product) and carbon efficiency (CO 2 -to-product) of CO 2 electrolysis remain far too low for large-scale deployment. A preponderance of evidence indicates that the principal reason for these low efficiencies is the rapid and thermodynamically favorable reaction of CO 2 with hydroxide (OH–) to form carbonate , which forces CO 2 electrolysis cells to operate under conditions that result in large voltage and CO 2 losses. This “CO 3 2 – problem” presents a fundamental scientific barrier to creating a viable electrochemical option for converting solar energy into chemicals and fuels.

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

Stoichiometrically coupled carbon and nitrogen cycling in the MIcrobial-MIneral Carbon Stabilization model version 1.0 (MIMICS-CN v1.0)

Explicit consideration of microbial physiology in soil biogeochemical models that represent coupled carbon–nitrogen dynamics presents opportunities to deepen understanding of ecosystem responses to environmental change. The MIcrobial-MIneral Carbon Stabilization (MIMICS) model explicitly represents microbial physiology and physicochemical stabilization of soil carbon (C) on regional and global scales. Here we present a new version of MIMICS with coupled C and nitrogen (N) cycling through litter, microbial, and soil organic matter (SOM) pools. The model was parameterized and validated against C and N data from the Long-Term Inter-site Decomposition Experiment Team (LIDET; six litter types, 10 years of observations, and 13 sites across North America). The model simulates C and N losses from litterbags in the LIDET study with reasonable accuracy (C: R 2 =0.63; N: R 2 =0.29), which is comparable with simulations from the DAYCENT model that implicitly represents microbial activity (C: R 2 =0.67; N: R 2 =0.30). Subsequently, we evaluated equilibrium values of stocks (total soil C and N, microbial biomass C and N, inorganic N) and microbial process rates (soil heterotrophic respiration, N mineralization) simulated by MIMICS-CN across the 13 simulated LIDET sites against published observations from other continent-wide datasets. We found that MIMICS-CN produces equilibrium values in line with measured values, showing that the model generates plausible estimates of ecosystem soil biogeochemical dynamics across continental-scale gradients. MIMICS-CN provides a platform for coupling C and N projections in a microbially explicit model, but experiments still need to identify the physiological and stoichiometric characteristics of soil microbes, especially under environmental change scenarios.

58 GEOSCIENCES↗
NASA NTRS1983

Eikonal phase shift analyses of carbon-carbon scattering

A high-energy double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series is used in determining eikonal phase shifts for carbon-carbon scattering at 204.2, 242.7, and 288.6 MeV. The double-folding potentials are derived by folding the energy-dependent free nucleon-nucleon interaction with densities for the projectile and target; these latter are obtained by unfolding the finite nucleon charge density from harmonic-well carbon charge distributions. The charge parameters for these distributions are taken from the results of electron scattering experiments. Predictions are made for total, reaction, and elastic differential cross sections using standard partial wave analysis for the scattering of identical particles and are then compared with recent experimental results. Excellent agreement is obtained despite the absence of arbitrarily adjusted parameters in the theory.

Townsend, L. W.↗
NASA NTRS1987

Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

Wannier, P. G.↗
NASA NTRS1989

The formation of weathering products on the LEW 85320 ordinary chondrite - Evidence from carbon and oxygen stable isotope compositions and implications for carbonates in SNC meteorites

Isotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the delta C-13 and delta O-18 values of the two generations of bicarbonate (Antarctic and Texas) are different: delta C-13 = + 7.9 per mil and + 4.2 per mil; delta O-18 = + 17.9 per mil and + 12.1 per mil, respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at - 2 + or - 4 C (Antarctic) and + 16 + or - 4 C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapor or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar delta C-13 values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.

Grady, Monica M.↗
NASA NTRS1989

The production of low mass carbon stars - Carbon-rich dredge up or oxygen-rich mass loss?

Conventional theory explains the origin of carbon stars as due to dredge up of carbon enriched material from the stellar core during helium flash events late in the life of solar mass AGB stars. This relatively efficient process, however, seems to produce a larger C/O ratio than observed (Lambert et al., 1987). A secondary effect which could contribute to the appearance of carbon stars, is the selective removal of oxygen from the atmosphere by radiative force expulsion of oxygen-rich dust grains. Calculations for this scenario are presented, which evaluate the degree of momentum coupling between the grains and gas under the thermodynamical conditions of AGB star atmospheres.

Stencel, R. E.↗
NASA NTRS1991

Spectral evidence for carbonates on Mars: Hydrous carbonates

Although many of the spectral features of the Martian samples studied are not unique mineralogical indicators, much of the current spectral data is consistent with (possibly abundant) hydrous carbonates on the surface of Mars. The absorption features in the measured samples were quite weak compared with those of anhydrous carbonates. The weak features imply that significantly more hydrous carbonates can be incorporated onto the surface before becoming spectrally evident; however, exact limits have yet to be determined. The stability of these materials in the Martian environment is not known, but their formation and occurrence in low temperature terrestrial environments makes them appealing candidates for weathering products on Mars.

Calvin, W. M.↗
NASA NTRS1992

The cyclic carbonates of the Latemar Massif: Evidence for the orbital forcing of a carbonate platform during the Middle Triassic

The Latemar Massif is an exhumed carbonate platform in the Dolomites of Northern Italy that was deposited during the Ladinian stage of the Middle Triassic. The platform interior is comprised of hundreds of vertically stacked, meter scale, subtidal limestone/vadose cap carbonate cycles ('Latemar couplets') arranged into upward thinning bundles of 5. The individual couplets are interpreted as the products of sea level oscillations occurring with an approximately 20,000 year periodicity; the 5:1 bundling is indicative of a lower order approximately 100,000 year modulating component. This combination of cycling is interpreted as a platform response to precession forcing with the 5:1 bundling an expression of modulation by the eccentricity. Spectral analysis confirms the significance of the 5:1 bundling, and identifies other significant bundling components related to other components of the eccentricity. The results show that the Latemar bundling spectrum is complex, with a splitting of components around the 1 percent bundling frequency, suggestive of the multiple component eccentricity in the 100,000 year range. On the other hand, there is no direct evidence for the major 400,000 year eccentricity component, although there is a dominant approximately 700,000 year cycling in the buildup (a 35:1 bundling period). Other higher frequency bundling components may be related to obliquity forcing. Simple models are presented to argue for and against an astronomical origin of these cyclic platform carbonates.

Hinnov, Linda↗
NASA NTRS1993

Carbon-carbon grid for ion engines

A method and apparatus of manufacturing a grid member for use in an ion discharge apparatus provides a woven carbon fiber in a matrix of carbon. The carbon fibers are orientated to provide a negatibe coefficient of thermal expansion for at least a portion of the grid member's operative range of use.

Garner, Charles E.↗
NASA NTRS1995

Carbon-carbon grid for ion engines

A method and apparatus of manufacturing a grid member for use in an ion discharge apparatus provides a woven carbon fiber in a matrix of carbon. The carbon fibers are orientated to provide a negatibe coefficient of thermal expansion for at least a portion of the grid member's operative range of use.

Garner, Charles E.↗
NASA NTRS1996

Studies of the Surface Treatment and Sizing of Carbon Fiber Surfaces on the Mechanical Properties of Composites Containing Carbon Fibers

Carbon fiber reinforced composites are materials where carbon fibers are used to reinforce a matrix to produce a light and strong material with important applications in the aerospace industry. There are many aspects of the preparation of these materials that would benefit from a study which combines the research of groups involved in the production, testing and analysis of these materials, and studies of the basic surface chemistry involved. This final reports presents the results of a project that has developed a collaboration between groups in all three of the major research universities in the State of Kansas, and promises to lead to a collaborative program that covers the major aspects of composite development and application. Sherwood has provided initial fiber surface treatment and sizing together with fiber and composite surface analysis; Lease, Tomblin and Wang have worked together toward the goal of preparing pre-preg and fabrication of laminated panels; Locke has developed computational models to evaluate the effect of surface treatment (and chemistry) on mechanical properties; Lease, Tomblin and Wang have worked together to perform all necessary mechanical testing. The research has been focused on materials that would benefit the High Speed Civil Transport (HSCT) program. The group has visited Dr. Howard Maars and his colleagues at NASA Langley, and has focused their studies on the NASA requirements discussed in this meeting. An important development, requested by NASA scientists, has been the acquisition and study of K3B as a matrix material for the composites. The project has led to the successful acquisition and surface analysis of K3B, together with the successful deposition of this material onto surface oxidized carbon fibers. Mechanical testing, modelling and the construction of composite preparation equipment has been achieved during the grant period.

Sherwood, Peter M. A.↗
NASA NTRS1994

Durability of Carbon-Carbon Composites to a Simulated Martian Atmosphere

A new facility was designed and constructed to investigate the effects of the Martian atmosphere on high temperature radiator components. Preliminary experimental results from carbon-carbon composite radiator samples suggest that carbon is unstable in the simulated Martian atmosphere at a temperature of 600 C, consistent with previous thermodynamic modeling. However, more work is needed to identify the exact mechanism. The versatile design of the facility permits additional study of materials stability in the presence of other atmospheres.

Jaworske, D. A.↗
NASA NTRS1998

Design Considerations for Lightweight Space Radiators Based on Fabrication and Test Experience with a Carbon-Carbon Composite Prototype Heat Pipe

This report discusses the design implications for spacecraft radiators made possible by the successful fabrication and Proof-of-concept testing of a graphite-fiber-carbon-matrix composite (i.e., carbon-carbon (C-C)) heat pipe. The proto-type heat pipe, or space radiator element, consists of a C-C composite shell with integrally woven fins. It has a thin-walled furnace-brazed metallic (Nb-1%Zr) liner with end caps for containment of the potassium working fluid. A short extension of this liner, at increased wall thickness beyond the C-C shell, forms the heat pipe evaporator section which is in thermal contact with the radiator fluid that needs to be cooled. From geometric and thermal transport properties of the C-C composite heat pipe tested, a specific radiator mass of 1.45 kg/m2 can be derived. This is less than one-fourth the specific mass of present day satellite radiators. The report also discusses the advantage of segmented space radiator designs utilizing heat pipe elements, or segments, in their survivability to micro-meteoroid damage. This survivability is further raised by the use of condenser sections with attached fins, which also improve the radiation heat transfer rate. Since the problem of heat radiation from a fin does not lend itself to a closed analytical solution, a derivation of the governing differential equation and boundary conditions is given in appendix A, along with solutions for rectangular and parabolic fin profile geometries obtained by use of a finite difference computer code written by the author.

Juhasz, Albert J.↗
NASA NTRS1998

Assessment of Anthropogenic and Climatic Impacts on the Global Carbon Cycle Using a 3-D Model Constrained by Isotopic Carbon Measurements and Remote Sensing of Vegetation

Our original proposal called for improved modeling of the terrestrial biospheric carbon cycle, specifically using biome-specific process models to account for both the energy and water budgets of plant growth, to facilitate investigations into recent changes in global atmospheric CO2 abundance and regional distribution. The carbon fluxes predicted by these models were to be incorporated into a global model of CO2 transport to establish large-scale regional fluxes of CO2 to and from the terrestrial biosphere subject to constraints imposed by direct measurements of atmospheric CO2 and its 13C/12C isotopic ratio. Our work was coordinated with a NASA project (NASA NAGW-3151) at the University of Montana under the direction of Steven Running, and was partially funded by the Electric Power Research Institute. The primary objective of this project was to develop and test the Biome-BGC model, a global biological process model with a daily time step which simulates the water, energy and carbon budgets of plant growth. The primary product, the unique global gridded daily land temperature, and the precipitation data set which was used to drive the process model is described. The Biome-BGC model was tested by comparison with a simpler biological model driven by satellite-derived (NDVI) Normalized Difference Vegetation Index and (PAR) Photosynthetically Active Radiation data and by comparison with atmospheric CO2 observations. The simple NDVI model is also described. To facilitate the comparison with atmospheric CO2 observations, a three-dimensional atmospheric transport model was used to produce predictions of atmospheric CO2 variations given CO2 fluxes owing to (NPP) Net Primary Productivity and heterotrophic respiration that were produced by the Biome-BGC model and by the NDVI model. The transport model that we used in this project, and errors associated with transport simulations, were characterized by a comparison of 12 transport models.

Keeling, Charles D.↗
NASA NTRS2002

Design Considerations for Lightweight Space Radiators Based on Fabrication and Test Experience With a Carbon-Carbon Composite Prototype Heat Pipe

This report discusses the design implications for spacecraft radiators made possible by the successful fabrication and proof-of-concept testing of a graphite-fiber-carbon-matrix composite (i.e., carbon-carbon (C-C)) heat pipe. The prototype heat pipe, or space radiator element, consists of a C-C composite shell with integrally woven fins. It has a thin-walled furnace-brazed metallic (Nb-1%Zr) liner with end caps for containment of the potassium working fluid. A short extension of this liner, at increased wall thickness beyond the C-C shell, forms the heat pipe evaporator section which is in thermal contact with the radiator fluid that needs to be cooled. From geometric and thermal transport properties of the C-C composite heat pipe tested, a specific radiator mass of 1.45 kg/sq m can be derived. This is less than one-fourth the specific mass of present day satellite radiators. The report also discusses the advantage of segmented space radiator designs utilizing heat pipe elements, or segments, in their survivability to micrometeoroid damage. This survivability is further raised by the use of condenser sections with attached fins, which also improve the radiation heat transfer rate. Since the problem of heat radiation from a fin does not lend itself to a closed analytical solution, a derivation of the governing differential equation and boundary conditions is given in appendix A, along with solutions for rectangular and parabolic fin profile geometries obtained by use of a finite difference computer code written by the author.

Juhasz, Albert J.↗
NASA NTRS2006

Carbon Nanotube-enhanced Carbon-phenolic Ablator Material

Phenolic impregnated carbon ablator (PICA) is a thermal protection system (TPS) material developed at NASA Ames Research Center in the mid-90 s for Discovery missions. It was used on the Stardust return capsule heat shield which successfully executed the highest speed Earth entry to date on January 15, 2006. PICA is a porous fibrous carbon insulation infiltrated with phenolic resin, and is an excellent ablator that is effective for heating rates up to 1000 W/sq cm. It is one of several candidate TPS materials for the next generation of crewed spacecraft for Lunar and Mars missions. We will describe an ongoing research effort at NASA to improve mechanical properties of the phenolic matrix with carbon nanotubes. The aim is two-fold: to increase overall TPS strength during reentry and to improve Micrometeoroid/Orbital Debris (MMOD) protection in space. The former requires at least a good dispersion of nanotubes in phenolic, while the latter also requires covalent bonding between them to couple and transfer impact energy effectively from matrix to nanotubes. We will discuss the required chemical functionalization of nanotubes, processing issues and test results.

Nikolaev, P.↗