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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Preparation and properties of silane-endcapped polyimide adhesives

Silane-endcapped polyimide high temperature adhesive formulations were prepared by reacting anhydride-terminated poly(amic acid), obtained from benzophenonetetracarboxylic dianhydride and a diamine (3,3'-, 3,4'- or 4,4'-diaminodiphenylmethane and 3,3', 3,4'- or 4,4'-diaminobenzophenone) with varying amounts of gama-aminopropyltriethoxysilane in dimethylacetamide. Resin properties were evaluated by torsional braid analysis and thermogravimetric analysis. Lap shear strengths of some of the adhesive bonds were determined at room temperature and at 177 C before and after ageing at 200 C for 2500 h and after boiling in water for 72 h.

Maudgal, S.↗
NASA NTRS1984

Preparation and characterization of a siloxane containing bismaleimide

A novel siloxane containing bismaleimide has been prepared by reacting maleic anhydride, benzophenonetetracarboxylic dianhydride and bis(gamma-aminopropyl)tetramethyldisiloxane. Characterization of this monomer was done by comparing its nuclear magnetic resonance spectrum (NMR) to those of model compounds. Solubility of the prepolymer was tested in amide, chlorinated and ether solvents. Films were cast from solution as well as by melt processing and a cure cycle was determined. Infrared spectrum (IR) of the resulting film was obtained. Thermal polymerization was investigated by differential scanning calorimetry (DSC). Thermal properties of the cured resin were followed by means of thermogravimetric analysis (TGA), torsional braid analysis (TBA) and dynamic mechanical analysis (DMA). Thermomechanical analysis (TMA) was used to study the effect of postcure on the glass transition temperature (Tg) of the resin. Adhesive strength of the resin was obtained at ambient temperature.

Maudgal, S.↗
NASA NTRS1985

Dielectric properties of 'diamondlike' carbon prepared by RF plasma deposition

Metal-carbon-metal structures were fabricated using either gold or aluminum evaporated electrodes and RF plasma (methane) deposited 'diamondlike' carbon films. Alternating-current conductance and capacitance versus voltage and frequency (10 Hz to 13 MHz) data were taken to determine the dielectric properties of these films. Conductance versus frequency data fit a generalized power law, consistent with both dc and hopping conduction components. The capacitance versus frequency data are well matched to the conductance versus frequency data, as predicted by a Kramers-Kronig analysis. The dielectric loss tangent is nearly constant at 0.5 to 1.0 percent over the frequency range from 1 to 100 kHz. The dc resistivity is above 10 to the 13th ohm cm, and the dc breakdown strength is above 8 x 10 to the 6th V/cm is properly prepared samples.

Lamb, J. D.↗
NASA NTRS1986

Effects of specimen preparation on the electromagnetic property measurements of solid materials with an automatic network analyzer

Effects of specimen preparation on measured values of an acrylic's electomagnetic properties at X-band microwave frequencies, TE sub 1,0 mode, utilizing an automatic network analyzer have been studied. For 1 percent or less error, a gap between the specimen edge and the 0.901-in. wall of the specimen holder was the most significant parameter. The gap had to be less than 0.002 in. The thickness variation and alignment errors in the direction parallel to the 0.901-in. wall were equally second most significant and had to be less than 1 degree. Errors in the measurement f the thickness were third most significant. They had to be less than 3 percent. The following parameters caused errors of 1 percent or less: ratios of specimen-holder thicknesses of more than 15 percent, gaps between the specimen edge and the 0.401-in. wall less than 0.045 in., position errors less than 15 percent, surface roughness, hickness variation in the direction parallel to the 0.401-in. wall less than 35 percent, and specimen alignment in the direction parallel to the 0.401-in. wall mass than 5 degrees.

Long, E. R., Jr.↗
NASA NTRS1986

Evaluation of multilayer printed wiring boards by metallographic techniques: An illustrated guide to the preparation and inspection of plated-through hole test coupons based on the requirements of Mil-P-55110D

This work is an illustrated handbook containing the rationale and procedure for the evaluation of multilayer printed wiring board construction integrity with respect to plated-through holes in accordance with the requirements of MIL-P-55110D, Printed Wiring Boards. It is intended as a practical aid for those concerned with determining the construction integrity of multilayer boards for high reliability applications. Photomicrographs of cross sectioned holes illustrate defect types, acceptable and unacceptable conditions, and methods of measurement. A procedure for specimen preparation is given, and appropriate paragraphs of the military specification are included and explained.

Jellison, J.↗
NASA NTRS1986

Process for preparing essentially colorless polyimide film containing phenoxy-linked diamines

A polyimide film that is approximately 90% transparent at 500 nm, useful for thermal protective coatings and solar cells, and the processes for preparing the same by thermal and chemical conversion are disclosed. An essential feature for achieving maximum optical transparency films requires utilizing recrystallized and/or sublimated specific aromatic diamines and dianhydride monomers and introducing phenoxy or thiophenyl separator groups and isomeric m,m' or o,p'-oriented diamines into the polymer molecular structure. The incorporation of these groups in the polymer structure serves to separate the chromaphoric centers and reduce the formation of inter-chain and intra-chain charge transfer complexes which normally cause absorptions in the UV-visible range. The films may be obtained by hand, brushing, casting, or spraying a layer of polyamic acid solutions onto a surface and thermally converting the applied layer to the polyimide, or the polyamic acid solution can be chemically converted to the polyimide, subsequentially dissolved in an organic solvent, and applied as a polyimide film layer with the solvent therein thermally removed.

Stclair, A. K.↗
NASA NTRS1986

Preparation and optical properties of GA(x)IN(1-x)P alloys

The solution crystallization method was used to obtain Ga(z)In(1-x)P alloys for all values of x desired between zero and 1. The method of preparation makes it possible to crystallize the solid at a constant temperature. The points obtained by cathodoluminescence are nearly in straight lines. The optical absorption thresholds are confirmed in the results and make it possible to define the nature of the transitions except when x is in the neighborhood of 0.65. These determinations agree with those of Hilsum and Porteus (1968), but are not in agreement with those obtained by Lorenz et al, (1968).

Rodot, H.↗
NASA NTRS1985

Evaluation of fuel preparation systems for lean premixing-prevaporizing combustors

A series of experiments was carried out in order to produce design data for a premixing prevaporizing fuel-air mixture preparation system for aircraft gas turbine engine combustors. The fuel-air mixture uniformity of four different system design concepts was evaluated over a range of conditions representing the cruise operation of a modern commercial turbofan engine. Operating conditions including pressure, temperature, fuel-to-air ratio, and velocity, exhibited no clear effect on mixture uniformity of systems using pressure-atomizing fuel nozzles and large-scale mixing devices. However, the performance of systems using atomizing fuel nozzles and large-scale mixing devices was found to be sensitive to operating conditions. Variations in system design variables were also evaluated and correlated. Mixing uniformity was found to improve with system length, pressure drop, and the number of fuel injection points per unit area. A premixing system capable of providing mixing uniformity to within 15 percent over a typical range of cruise operating conditions is demonstrated.

Dodds, W. J.↗
NASA NTRS1985

The preparation and archiving of machine-readable astronomical data

The preparation of machine-readable astronomical catalogs for archiving and distribution from the ADC is described. Examples of specific format and data structure changes to improve compatibility with other computers, to homogenize the presentation of astronomical data among catalogs, and to increase storage efficiency are given. Various checks which are often made to insure internal consistency and for comparison with published versions are identified and the importance of permanently archiving astronomical data in the best possible condition is emphasized.

Warren, W. H., Jr.↗
NASA NTRS1985

Preparing a health care delivery system for Space Station

NASA's Space Station is viewed as the beginning of man's permanent presence in space. This paper presents the guidelines being developed by NASA's medical community in preparing a quality, permanent health care delivery system for Space Station. The guidelines will be driven by unique Space Station requirements such as mission duration, crew size, orbit altitude and inclination, EVA frequency and rescue capability. The approach will emphasize developing a health care system that is modular and flexible. It will also incorporate NASA's requirements for growth capability, commonality, maintainability, and advanced technology development. Goals include preventing unnecessary rescue attempts, as well as maintaining the health and safety of the crew. Proper planning will determine the levels of prevention, diagnosis, and treatment necessary to achieve these goals.

Logan, J. S.↗
NASA NTRS1986

Preparation of large-particle-size monodisperse latexes in space

Results are reported of latex sphere polymerization experiments performed on two flights of the Columbia and three flights of the Challenger. The trials were carried out because polymerization of the spheres in space avoids coagulation, nucleation of a new crop of particles, and excessive stirring requirements, and allows growth of spheres larger than 4 microns diam. The Monodisperse Latex Reactor (MLR) held four stirred 100 cc sealed stainless steel cylindrical containers. The mixtures were monitored for the conversion times, volume decreases as spheres formed and the mixture temperature. The spheres were grown from 0.19 micron seeds. Details of the flight preparation efforts are outlined. In flights which did not experience mechanical malfunctions spheres 3-30 microns diam were grown that had noticeably lower size variations than did the ground-based control particles. The 10 micron diam spheres grown on STS-6 were accepted as standard reference material by the NBS and became the first products made in space to be commercially sold on earth; the 30 micron spheres also became NBS standards. The experiments confirmed all projected benefits of producing the spheres in space, as well as provided the opportunity to grow more larger offsize spheres by finishing the growths on earth.

Vanderhoff, J. W.↗
NASA NTRS1985

Preparation and analysis of particulate metal deposits

Small particles and clusters of palladium were grown by deposition from the vapor phase under ultrahigh vacuum conditions. Amorphous and crystalline support films of Al2O3 and ultrathin amorphous carbon films were used as substrate materials. The growth of the metal deposit was monitored in situ by scanning transmission diffraction of energy-filtered 100 kV electrons and high resolution transmission electron microscopy (TEM) analysis was performed in a separate instrument. It was established by in situ TEM, however, that the transfer of specimens in this case did not unduly affect the size and distribution of deposit particles. It was found that the cleanness, stoichiometry, crystallinity and structural perfection of the support surface play an essential role in determining the crystalline perfection and structure of the particles. The smallest palladium clusters reproducibly prepared contained not more than six atoms but size determinations below 1 nm average particle diameter are very problematic with conventional TEM. Palladium particles grown on carbon supports feature an impurity-stabilized mosaic structure.

Poppa, H.↗
NASA NTRS1987

A review of tin oxide-based catalytic systems: Preparation, characterization and catalytic behavior

This paper reviews the important aspects of the preparation, characterization and catalytic behavior of tin oxide-based catalytic systems including doped tin oxide, mixed oxides which contain tin oxide, Pt supported on tin oxide and Pt/Sn supported on alumina. These systems have a broad range of applications and are continually increasing in importance. However, due to their complex nature, much remains to be understood concerning how they function catalytically.

Hoflund, Gar B.↗
NASA NTRS1987

Process for preparing phthalocyanine polymer from imide containing bisphthalonitrile

Imide-linked bisphthalonitrile compounds are prepared by combining a dicyano aromatic diamine and an organic dianhydride to produce an amic acid linked bisphthalonitrile compound. The amic acid linked bisphthalonitrile compound is dehydrocyclized to produce the imide-linked bisphthalonitrile compounds. The imide-linked bisphthalonitrile compounds may be polymerized to produce a phythalocyanine polymer by heating the imide-linked bisphthalonitrile compound, either alone or in the presence of a metal powder or a metal salt. These compounds are useful in the coating, laminating and molding arts. The polymers are useful in composite matrix resins where increased fire resistance, toughness and resistance to moisture are required, particularly as secondary structures in aircraft and spacecraft.

Achar, Bappalige N.↗
NASA NTRS1987

Preparation of B-trichloroborazine

The present invention relates to a method of preparing B-trichloroborazine. Generally, the method includes the combination of gaseous boron trichloride in an anhydrous aprotic organic solvent followed by addition of excess gaseous ammonia at ambient temperature or below. The reaction mixture is heated to about 100 to 140 C followed by cooling, removal of the solid ammonium chloride at ambient temperature, distillation of the solvent under vacuum if necessary at a temperature of up to about 112 C, and recovery of the B-trichloroborazine. Solvents include toluene, benzene, xylene, chlorinated hydrocarbons, chlorinated aromatic compounds, or mixtures thereof. Toluene is a preferred solvent. The process provides a convenient synthesis of a material which often decomposes on standing. B-trichloroborazine is useful in a number of chemical reactions, and particularly in the formation of high temperature inorganic polymers and polymer precursors.

Riccitiello, Salvatore R.↗
NASA NTRS1987

Procedure to prepare transparent silica gels

This invention relates to the production of silica gels and in particular to a process for the preparation of silica gels which can be used as a crystal growth medium that simulates the convectionless environment of space to produce structurally perfect crystals. Modern utilizations of substances in electronics, such as radio transmitters and high frequency microphones, often require single crystals with controlled purity and structural perfection. The near convectionless environment of silica gel suppresses nucleation, thereby reducing the competitive nature of crystal growth. This competition limits the size and perfection of the crystal; and it is obviously desirable to suppress nucleation until, ideally, only one crystal grows in a predetermined location. A silica gel is not a completely convectionless environment like outer space, but is the closest known environment to that of outer space that can be created on Earth.

Barber, Patrick G.↗
NASA NTRS1986

Preparation of silicon carbide-silicon nitride fibers by the pyrolysis of polycarbosilazane precursors - A review

The development of silicon carbide-silicon nitride fibers (SiC-Si3N4) by the pyrolysis of polycarbosilazane precursors is reviewed. Precursor resin, which was prepared by heating tris(N-methylamino)methylsilane or tris(N-methylamino)phenylsilane to about 520 C, was drawn into fibers from the melt and then made unmeltable by humidity conditioning at 100 C and 95 percent relative humidity. The humidity treated precursor fibers were pyrolyzed to ceramic fibers with good mechanical properties and electrical resistivity. For example, SiC-Si3N4 fibers derived from tris(N-methylamino)methylsilane had a tensile rupture modulus of 29 million psi and electrical resistivity of 6.9 x ten to the 8th power omega-cm, which is ten to the twelfth power times greater than that obtained for graphite fibers.

Penn, B. G.↗