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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Tailor making high performance graphite fiber reinforced PMR polyimides

Studies performed to demonstrate the feasibility of using the polymerization of monomer reactants (PMR) approach to tailor make processable polyimide matrix resins are described. Monomeric reactant solutions containing the dimethyl ester of 3,3',4,4' -benzophenonetetracarboxylic acid, 4, 4' -methylenedianiline and the monomethyl ester of 5-norbornene-2, 3-dicarboxylic acid were used to impregnate Hercules HTS graphite fiber. Six different monomeric reactant stoichiometries were studied. The processing characteristics and elevated temperature mechanical properties of the PMR polyimide/HTS graphite fiber composites are described.

Serafini, T. T.↗
NASA NTRS1975

Tailor making high performance graphite fiber reinforced PMR polyimides

Studies performed to demonstrate the feasibility of using the polymerization of monomer reactants (PMR) approach in order to 'tailor-make' processable polyimide matrix resins are described. Monomeric reactant solutions containing the dimethyl ester of 3, 3', 4, 4'-benzophenonetetracarboxylic acid, 4, 4'-methylenedianiline and the monomethyl ester of 5-norborene-2, 3-dicarboxylic acid were used to impregnate Hercules HTS graphite fiber. Six different monomeric reactant stoichiometries were studied. The processing characteristics and elevated temperature mechanical properties of the PMR polyimide/HTS graphite fiber composites are described.

Serafini, T. T.↗
NASA NTRS1988

Nature and origin of C-rich ordinary chondrites and chondritic clasts

The abundance and the isotopic compositions of C, O, and noble gases were investigated together with the petrologic characteristics of four carbon-rich ordinary chondrites (Sharps and Allan Hills A77011, A78119, and A81024) and three C-rich chondritic clasts. The results of the analyses suggest that all of the chondrites and clasts analyzed belong to petrologic type 3 and contain abundant carbon-rich aggregates, which, in at least two of these samples, consist of poorly graphitized carbon commonly associated with metallic Fe,Ni. The data also suggest that the four C-rich chondrites originated on the H, L, and LL parental bodies, but that clasts in Dimmitt and Plainview and other regolith breccias may come from different bodies. The results obtained are consistent with the view that graphite is not a common nebular phase.

Scott, E. R. D.↗
NASA NTRS1980

Determination of the orientation symmetry axis of graphite specimens

A technique is described for determining the true orientation symmetry axis of graphite specimens from conventional X-ray diffraction data. The technique, although developed for graphite, is applicable to any material exhibiting crystalline orientation which is symmetric about some axis. The requisite equations are derived for applying the procedure to both Bacon transmission data and rotating specimen reflection data. Results are presented which show that the symmetry axis of eleven molded graphites tested differed significantly from their nominal pressing directions.

Schryer, D. R.↗
NASA NTRS1984

Morphology and Dynamic Mechanical Properties of Diglycidyl Ether of Bisphenol-A Toughened with Carboxyl-Terminated Butadiene-Acrylonitrile

The fracture toughness of an incorporation of a carboxyl-terminated butadiene acrylonitrile (CTBN) elastomer in diglycidyl ether bisphenol A (DGEBA) resin was investigated. Measurements of dynamic mechanical properties, scanning electron microscopy and small-angle X-ray scattering were carried out to characterize the state of cure, morphology and particle size and size distribution of the neat resins and their graphite fiber reinforced composites.

Hong, S. D.↗
NASA NTRS1985

Fabrication process of a high temperature polymer matrix engine duct

The process that was used in the molding of an advanced composite outer by-pass duct planned for the F404 engine is discussed. This duct was developed as a potential replacement for the existing titanium duct in order to reduce both the weight and cost of the duct. The composite duct is now going into the manufacturing technology portion of the program. The duct is fabricated using graphite cloth impregnated with the PMR-15 matrix system.

Pratt, R. D.↗
NASA NTRS1987

'Oxide-free' tip for scanning tunneling microscopy

A new tip for scanning tunneling microscopy and a tip repair procedure that allows one to reproducibly obtain atomic images of highly oriented pyrolytic graphite with previously inoperable tips are reported. The tips are shown to be relatively oxide-free and highly resistant to oxidation. The tips are fabricated with graphite by two distinct methods.

Colton, R. J.↗
NASA NTRS1979

Silicon Halide-alkali Metal Flames as a Source of Solar Grade Silicon

A program is presented which was aimed at determining the feasibility of using high temperature reactions of alkali metals and silicon halides to produce low cost solar-grade silicon. Experiments are being conducted to evaluate product separation and collection processes, measure heat release parameters for scaling purposes, and determine the effects of the reactants and/or products on materials of reactor construction. During the current reporting period, the results of heat release experiments were used to design and construct a new type of thick-wall graphite reactor to produce larger quantities of silicon. A reactor test facility was constructed. Material compatibility tests were performed for Na in contact with graphite and several coated graphites. All samples were rapidly degraded at T = 1200K, while samples retained structural strength at 1700K. Pyrolytic graphite coatings cracked and separated from substances in all cases.

Olson, D. B.↗
NASA NTRS1980

Silicon halide-alkali metal flames as a source of solar grade silicon

The feasibility of using continuous high-temperature reactions of alkali metals and silicon halides to produce silicon in large quantities and of suitable purity for use in the production of photovoltaic solar cells was demonstrated. Low pressure experiments were performed demonstrating the production of free silicon and providing experience with the construction of reactant vapor generators. Further experiments at higher reagent flow rates were performed in a low temperature flow tube configuration with co-axial injection of reagents and relatively pure silicon was produced. A high temperature graphite flow tube was built and continuous separation of Si from NaCl was demonstrated. A larger scaled well stirred reactor was built. Experiments were performed to investigate the compatability of graphite based reactor materials of construction with sodium. At 1100 to 1200 K none of these materials were found to be suitable. At 1700 K the graphites performed well with little damage except to coatings of pyrolytic graphite and silicon carbide which were damaged.

Olson, D. B.↗
NASA NTRS1975

Carbide coated fibers in graphite-aluminum composites

Thin, uniform coats of titanium carbide, deposited on graphite fibers by chemical vapor deposition with thicknesses up to approximately 0.1 microns were shown to improve fiber strength significantly. For greater thicknesses, strength was degraded. The coats promote wetting of the fibers and infiltration of the fiber yarns with aluminum alloys, and act as protective barriers to inhibit reaction between the fibers and the alloys. Chemical vapor deposition was used to produce silicon carbide coats on graphite fibers. In general, the coats were nonuniform and were characterized by numerous surface irregularities. Despite these irregularities, infiltration of these fibers with aluminum alloys was good. Small graphite-aluminum composite samples were produced by vacuum hot-pressing of aluminum-infiltrated graphite yarn at temperatures above the metal liquidus.

Imprescia, R. J.↗
NASA NTRS1986

Behavior of insoluble particles during parabolic flight solidification processing of Fe-C-Si and Fe-C-V alloys

In a high-g rapid solidification environment, Fe-base alloy insoluble particles at the solidification interface may be pushed ahead of the interface or may be trapped in the solid, depending on the correlation of various interface energies, the solidification rates, and the Stokes force; particle agglomeration due to buoyancy-driven convection further complicates the problem. Attention is presently given to results obtained for directionally solidified Fe-C-Si and Fe-C-V alloys during parabolic low-g flight and ground experiments. In these systems, graphite and vanadium carbide can be considered to be the insoluble particles.

Stefanescu, D. M.↗
NASA NTRS2002

Comparison of graphite, aluminum, and TransHab shielding material characteristics in a high-energy neutron field

Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study. Published by Elsevier Science Ltd.

NASA Center JSC↗