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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Method of Making an Electroactive Sensing/Actuating Material for Carbon Nanotube Polymer Composite

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a, third component of micro -sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Ounaies, Zoubeida↗
NASA NTRS1973

Surface emissivity of a reinforced carbon composite material with an oxidation-inhibiting coating

Total effective emissivity and spectral emissivity over the wavelength range of 0.65 to 6.3 microns were determined for temperatures from 1300 t0 2250 deg K. A multi channel radiometer was used in the arcjet and laboratory tests. The black-body-hole method was used to independently check radiometer results. The results show the silicon-carbide coated reinforced carbon composite material is a nongray radiator. The total effective emissivity and the spectral emissivity at 0.65 micron both decreased with increasing temperature, respectively, from approximately 0.8 to 0.6, and from 0.4 to 0.25, over the temperature range. The emissivity values were the same when the sample was viewed normal to the surface or at a 45 deg angle. Recommended emissivity values are presented.

Wakefield, R. M.↗
NASA NTRS2006

Carbon Nanotube Material Quality Assessment

The nanomaterial activities at NASA Johnson Space Center focus on carbon nanotube production, characterization and their applications for aerospace systems. Single wall carbon nanotubes are produced by arc and laser methods. Characterization of the nanotube material is performed using the NASA JSC protocol developed by combining analytical techniques of SEM, TEM, UV-VIS-NIR absorption, Raman, and TGA. A possible addition of other techniques such as XPS, and ICP to the existing protocol will be discussed. Changes in the quality of the material collected in different regions of the arc and laser production chambers is assessed using the original JSC protocol. The observed variations indicate different growth conditions in different regions of the production chambers.

Yowell, Leonard↗
NASA NTRS1992

A finite element method for the thermochemical decomposition of polymeric materials. II - Carbon phenolic composites

A previously developed formulation for modeling the thermomechanical behavior of chemically decomposing, polymeric materials is verified by simulating the response of carbon phenolic specimens during two high temperature tests: restrained thermal growth and free thermal expansion. Plane strain and plane stress models are used to simulate the specimen response, respectively. In addition, the influence of the poroelasticity constants upon the specimen response is examined through a series of parametric studies.

Sullivan, R. M.↗
NASA NTRS2015

Evaluation of the Anisotropic Radiative Conductivity of a Low-Density Carbon Fiber Material from Realistic Microscale Imaging

The radiative heat transfer inside a low-density carbon fiber insulator is analyzed using a three-dimensional direct simulation model. A robust procedure is presented for the numerical calculation of the geometric configuration factor to compute the radiative energy exchange processes among the small discretized surface areas of the fibrous material. The methodology is applied to a polygonal mesh of a fibrous insulator obtained from three-dimensional microscale imaging of the real material. The anisotropic values of the radiative conductivity are calculated for that geometry. The results yield both directional and thermal dependence of the radiative conductivity.

Evaluation↗
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.↗
NASA NTRS1995

New Anode Material for Rechargeable Li-ION Cells

Carbon materials, such as graphite, cokes, pitch and PAN fibers, are being evaluated in lithium batteries as alternate anode materials with some degree of success. There is an effort to look for other non-carbon anode materials which have larger Li capacity, higher rate capability, smaller first charge capacity loss and better mechanical stability during cycling. A Li-Mg-Si material is evaluated.

rechargeable batteries anode materials Li-ION cell↗
NASA NTRSDate not supplied

Investigation of the Effect of Etch Pits on the Material Properties of Carbon Fiber Structures

It is well known that etch pits are formed on carbon surfaces during their consumption in reactive gas environments such as during ablation of carbon-based thermal protection system (TPS) materials. These pits start out from atomic defects on the carbon surface, grow in size and then ultimately lead to the complete removal of the solid carbon material. However, the effect of such etch pits on the material properties of carbon ablators such as FiberForm are poorly understood, as the maximum size of pits are on the order of microns in size, which makes them hard to observe experimentally. Hence, we have developed a module within the Porous Microstructure Analysis code PuMA that can generate etch pits on an arbitrary material surface, with a prescribed distribution of pit size and density. We use this newly developed module to calculate material properties of FiberForm, which is the base material for one of the most commonly used TPS materials - Phenolic Impregnated Carbon Ablator (PICA). The detailed microstructure of FiberForm in PuMA will either be generated synthetically or obtained from X-ray microtomography. Our simulations show that material properties such as the thermal conductivity and tortuosity decrease with increasing degree of pitting. This will be helpful to more accurately predict the degradation of carbon-based TPS during ablation, and furthermore may allow us to identify previously unknown TPS failure modes due to pitting.

PuMA↗
NASA NTRSDate not supplied

Investigation of the effect of etch pits on the material properties of carbon fiber structures

It is well known that etch pits are formed on carbon surfaces during their consumption in reactive gas environments such as during ablation of carbon-based thermal protection system (TPS) materials. These pits start out from atomic defects on the carbon surface, grow in size and then ultimately lead to the complete removal of the solid carbon material [1, 2]. However, the effect of such etch pits on the material properties of carbon ablators such as FiberForm are poorly understood, as the maximum size of pits are on the order of microns in size, which makes them hard to observe experimentally. Hence, we have developed a module within the Porous Microstructure Analysis code PuMA [3] that can generate etch pits on an arbitrary material surface, with a prescribed distribution of pit size and density. Figure 1 shows a FiberForm sample with artificially generated pits of varying radii and pit density. We use this newly developed module to calculate material properties of FiberForm, which is the base material for one of the most commonly used TPS materials - Phenolic Impregnated Carbon Ablator (PICA). The detailed microstructure of FiberForm in PuMA will either be generated synthetically or obtained from X-ray microtomography [4]. Our simulations show that material properties such as the thermal conductivity and tortuosity decrease with increasing degree of pitting. This will be helpful to more accurately predict the degradation of carbon-based TPS during ablation, and furthermore may allow us to identify previously unknown TPS failure modes due to pitting.

PuMA↗
NASA NTRS1993

A photovoltaic catenary-tent array for the Martian surface

To provide electrical power during an exploration mission to Mars, a deployable tent-shaped structure with a flexible photovoltaic (PV) blanket is proposed. The array is designed with a self-deploying mechanism utilizing pressurized gas expansion. The structural design for the array uses a combination of cables, beams, and columns to support and deploy the PV blanket. Under the force of gravity, a cable carrying a uniform load will take the shape of a catenary curve. A catenary-tent collector is self shading which must be taken into account in the solar radiation calculation. The shape and the area of the shadow on the array was calculated and used in the determination of the global irradiance on the array. The PV blanket shape and structure dimensions were optimized to achieve a configuration which maximizes the specific power (W/kg). The optimization was performed for three types of PV blankets (silicon, gallium arsenide over germanium, and amorphous silicon) and two types of structural materials (carbon composite and arimid fiber composite). The results show that the catenary shape of the PV blanket corresponding to zero end angle at the base with respect to the horizontal results in the highest specific power. The tent angle is determined by optimizing the specific mass and the output power for maximum specific power. The combination of carbon fiber structural material and amorphous silicon blanket produces the highest specific power.

Colozza, Anthony J.↗
NASA NTRS1993

A photovoltaic catenary-tent array for the Martian surface

To provide electrical power during an exploration mission to Mars, a deployable tent-shaped structure with a flexible photovoltaic (PV) blanket is proposed. The array is designed with a self-deploying mechanism utilizing pressurized gas expansion. The structural design for the array uses a combination of cables, beams, and columns to support and deploy the PV blanket. Under the force of gravity a cable carrying a uniform load will take the shape of a catenary curve. A catenary-tent collector is self shadowing which must be taken into account in the solar radiation calculation. The shape and the area of the shadow on the array was calculated and used in the determination of the global radiation on the array. The PV blanket shape and structure dimension were optimized to achieve a configuration which maximizes the specific power (W/kg). The optimization was performed for four types of PV blankets (Si, GaAs/Ge, GaAs CLEFT, and amorphous Si) and four types of structure materials (Carbon composite, Aramid Fiber composite, Aluminum, and Magnesium). The results show that the catenary shape of the PV blanket, which produces the highest specific power, corresponds to zero end angle at the base with respect to the horizontal. The tent angle is determined by the combined effect of the array structure specific mass and the PV blanket output power. The combination of carbon composite structural material and GaAs CLEFT solar cells produce the highest specific power. The study was carried out for two sites on Mars corresponding to the Viking Lander locations. The designs were also compared for summer, winter, and yearly operation.

Crutchik, M.↗
NASA NTRS2008

Lightweight Carbon-Carbon High-Temperature Space Radiator

A document summarizes the development of a carbon-carbon composite radiator for dissipating waste heat from a spacecraft nuclear reactor. The radiator is to be bonded to metal heat pipes and to operate in conjunction with them at a temperature approximately between 500 and 1,000 K. A goal of this development is to reduce the average areal mass density of a radiator to about 2 kg/m(exp 2) from the current value of approximately 10 kg/m(exp 2) characteristic of spacecraft radiators made largely of metals. Accomplishments thus far include: (1) bonding of metal tubes to carbon-carbon material by a carbonization process that includes heating to a temperature of 620 C; (2) verification of the thermal and mechanical integrity of the bonds through pressure-cycling, axial-shear, and bending tests; and (3) construction and testing of two prototype heat-pipe/carbon-carbon-radiator units having different radiator areas, numbers of heat pipes, and areal mass densities. On the basis of the results achieved thus far, it is estimated that optimization of design could yield an areal mass density of 2.2 kg/m (exp 2) close to the goal of 2 kg/m(exp 2).

Miller, W.O.↗
NASA NTRS2005

Further Geophysical Studies of the Haughton Impact Structure

The approximately 23 Ma Haughton impact structure, located at 75 deg 23 min N, 89 deg 39 min W in the Canadian Arctic, on Devon Island, Nunavut, Canada is a well-preserved impact structure with an original rim diameter estimated at about 23 - 24 km. Past studies, in the 1980s, did an initial survey of the Haughton structure, looking at its surface units, exposures, map surface geology, topographic and initial surveys of gravity and magnetic fields in profiles across the impact structure. A topological outer ring and the lack of a well-defined central peak was cited as evidence that Haughton was a multi-ring structure. However other authors consider it more likely that the Haughton structure is a central-peak basin with simply a limited extent, and/or full peak features having been removed through glaciations and subsequent years. The impact structure is located in approximately 2 km thickness of carbonate material on top of a gneissic basement. The impact structure itself can be described in terms of uplifted and moved blocks of altered gneissic and carbonate material with areas in the center of the crater covered with impact carbonate melts and/or reworked impact breccias. Additional information is included in the original extended abstract.

Glass, B. J.↗
NASA NTRS1992

Solar Probe thermal shield design and testing

This paper discusses the major thermal shield subsystem development activities in support of the Solar Probe study being conducted at JPL. The Solar Probe spacecraft will travel to within 4 solar radii of the sun's center to perform fundamental experiments in space physics. Exposure to 2900 earth suns at perihelion requires the spacecraft to be protected within the shadow envelope of a protective shield. In addition, the mass loss rate off of the shield at elevated temperature must comply with plasma instrument requirements and has become the driver of the shield design. This paper will focus on the analytical design work to size the shield and control the shield mass loss rate for the various spacecraft options under study, the application of carbon-carbon materials for shield components, development and preparation of carbon-carbon samples for materials testing, and a materials testing program for carbon-carbon and tungsten alloys to investigate thermal/optical properties, mass loss (carbon-carbon only), material integrity, and high velocity impact behavior.

Millard, Jerry M.↗
NASA NTRS1994

Scaling craters in carbonates: Electron paramagnetic resonance analysis of shock damage

Carbonate samples from the 8.9-Mt nuclear (near-surface explosion) crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance (EPR). Samples from below the OAK apparent crater floor were obtained from six boreholes, as well as ejecta recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to the spectra of Solenhofen and Kaibab limestone, which had been skocked to known pressures. Analysis of the OAK Crater borehole samples has identified a thin zone of allocthonous highly shocked (10-13 GPa) carbonate material underneath the apparent crater floor. This approx. 5- to 15-m-thick zone occurs at a maximum depth of approx. 125 m below current seafloor at the borehole, sited at the initial position of the OAK explosive, and decreases in depth towards the apparent crater edge. Because this zone of allocthonous shocked rock delineates deformed rock below, and a breccia of mobilized sand and collapse debris above, it appears to outline the transient crater. The transient crater volume inferred in this way is found to by 3.2 +/- 0.2 times 10(exp 6)cu m, which is in good agreement with a volume of 5.3 times 10(exp 6)cu m inferred from gravity scaling of laboratory experiments. A layer of highly shocked material is also found near the surface outside the crater. The latter material could represent a fallout ejecta layer. The ejecta boulders recovered from the present crater floor experienced a range of shock pressures from approx. 0 to 15 GPa with the more heavily shocked samples all occurring between radii of 360 and approx. 600 m. Moreover, the fossil content, lithology and Sr isotopic composition all demonstrate that the initial position of the bulk of the heavily shocked rock ejecta sampled was originally near surface rock at initial depths in the 32 to 45-m depth (below sea level) range. The EPR technique is also sensitive to prehistoric shock damage. This is demonstrated by our study of shocked Kaibab limestone from the 49,000-year-old Meteor (Barringer) Crater Arizona.

Polanskey, Carol A.↗
NASA NTRS2001

Effects of Surface Oxygen on the Performance of Carbon as an Anode in Lithium-Ion Batteries

Carbon materials with similar bulk structure but different surface oxygen were compared for their performance as anodes in lithium-ion battery. The bulk structure was such that the graphene planes were perpendicular to the surface. Three types of surfaces were examined: surface containing C=O type oxygen. surface containing -O-C type oxygen, and surface containing high concentration of active sites. The test involved cycles of lithium insertion into and release from the carbon materials, which was in the half cells of carbon/saturated LiI-50/50 (vol %) EC and DMC/lithium. During the first cycle of lithium insertion, the presence of adsorbed oxygen, -O-C type oxygen, active carbon sites, and C=O type oxygen resulted in the formation of solid-electrolyte interface (SEI) when the carbon's voltage relative to lithium metal was >1.35, 1 to 1.35, 0.5 to 1, and 0.67 to 0.7 V, respectively. An optimum -O-C type oxygen and a minimum C=O type oxygen was found to increase the reversible and decrease the irreversible capacity of carbon. Active sites on the carbon surface result in a large irreversible capacity and a second lithium insertion-release mechanism. However, this new mechanism has a short cycle life.

Hung, Ching-Cheh↗
NASA NTRS2003

Engineered Carbon Nanotube Materials for High-Q Nanomechanical Resonators

This document represents a presentation offered by the Jet Propulsion Laboratory, with assistance from researchers from Brown University and Northrop Grumman. The presentation took place in Seoul, Korea in July 2003 and attempted to demonstrate the fabrication approach regarding the development of high quality factor (high-Q) mechanical oscillators (in the forms of a tunable nanotube resonator and a nanotube array radio frequency [RF] filter) aimed at signal processing and based on carbon nanotubes. The presentation also addressed parallel efforts to develop both in-plane single nanotube resonators as well as vertical array power devices.

chemical vapor depositions↗