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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 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Effect of high temperature aging on bonded and weld bonded joints

Development of adhesives for applications requiring long-term service at temperatures up to 600 F is discussed. This development work utilizes polyimide (PI) and polyphenylquinoxaline (PPQ) resin technology worked out previously. The resultant adhesives are evaluated in structural joints of titanium, steel and composite adherends and in honeycomb sandwich panels. Suitable adhesives also are evaluated in weld bonded titanium alloy joints. Testing includes determination of long-term aging of stressed and unstressed specimens at temperatures from about 450 F to 600 F as well as under dynamic fatigue conditions.

Vaughan, R. W.↗
NASA NTRS1977

Optical properties of ion beam textured metals

Copper, silicon, aluminum, titanium and 316 stainless steel were textured by 1000 eV xenon ions from an 8 cm diameter electron bombardment ion source. Simultaneously sputter-deposited tantalum was used to facilitate the development of the surface microstructure. Scanning electron microscopy of the ion textured surfaces revealed two types of microstructure. Copper, silicon, and aluminum developed a cone structure with an average peak-to-peak distance ranging from 1 micron for silicon to 6 microns for aluminum. Titanium and 316 stainless steel developed a serpentine ridge structure. The average peak-to-peak distance for both of these materials was 0.5 micron. Spectral reflectance was measured using an integrating sphere and a holraum reflectometer. Total reflectance for air mass 0 and 2, solar absorptance and total emittance normalized for a 425 K black body were calculated from the reflectance measurements.

Hudson, W. R.↗
NASA NTRS1977

Friction and wear properties of three hard refractory coatings applied by radiofrequency sputtering

The adherence, friction, and wear properties of thin hard refractory compound coatings applied to 440C bearing steel by radiofrequency sputtering were investigated. Friction and wear tests were done with nonconforming pin on disk specimens. The compounds examined were chromium carbide, molybdenum silicide, and titanium carbide. The adherence, friction, and wear were markedly improved by the application of a bias voltage to the bearing steel substrate during coating deposition. Analysis by X-ray photoelectron spectroscopy indicated that the improvement may be due to a reduction in impurities in bias deposited coatings. A fivefold reduction in oxygen concentration in MoSi2 coating by biasing was noted. Chromium carbide was not effective as an antiwear coating. Molybdenum silicide provided some reduction in both friction and wear. Titanium carbide exhibited excellent friction and antiwear properties at light loads. Plastic flow and transfer of the coating material onto the pin specimen appears to be important in achieving low friction and wear.

Brainard, W. A.↗
NASA NTRS1977

Method of preparing zinc orthotitanate pigment

Zinc orthotitanate suitable for use as a pigment for spacecraft thermal control coatings is prepared by heating a slightly zinc deficient reaction mixture of precipitated oxalates of zinc and titanium. The reaction mixture can be formed by coprecipitation of zinc and titanium oxalates from chloride solution or by mixing separately precipitated oxalates. The mixture is first heated to 400 to 600 C to remove volatiles and is then rapidly heated at 900 to 1200 C. Zinc orthotitanate produced by this method exhibits the very fine particle size needed for thermal control coatings as well as stability in a space environment.

Gates, D. W.↗
NASA NTRS1977

Thermionic converter performance with oxide collectors

Thermionic converters using a variety of metal oxide collector surfaces have been fabricated and tested. Both work function and power output data are presented and evaluated. Oxides of barium, strontium, zinc, tungsten and titanium have been incorporated into a variable spacing converter. Tungsten oxide was found to give the highest converter performance and to furnish oxygen for the emitter at the same time. Oxygenated emitters operate at reduced cesium pressure with an increase in electrode spacing. Electron spectroscopy for chemical analysis (ESCA) performed on several tungsten oxide collectors showed cesium penetration of the oxide layer, possibly forming a cesium tungstate bronze. Titanium oxide showed high performance but did not furnish oxygen for the emitter; strontium oxide, in the form of a sprayed layer, appeared to dissociate in the presence of cesium. Sprayed coatings of barium and zinc oxides produced collector work functions of about 1.3 eV, but had excessive series resistance. Lanthanum hexaboride, in combination with oxygen introduced through a silver tube, and cesium produced a low work function collector and better than average performance.

Lieb, D.↗
NASA NTRS1978

Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data.

Royster, D. M.↗
NASA NTRS1978

Titanium/beryllium laminates: Fabrication, mechanical properties, and potential aerospace applications

The investigation indicated that structural laminates can be made which have: a modulus of elasticity comparable to steel, fracture strength of comparable to the yield strength of titanium, density comparable to aluminum, impact resistance comparable to titanium, and little or no notch sensitivity. These laminates can have stiffness and weight advantages over other materials including advanced fiber composites, in some aerospace applications where buckling resistance, vibration frequencies, and weight considerations control the design.

Chamis, C. C.↗
NASA NTRS1978

Wear of single-crystal silicon carbide in contact with various metals in vacuum

Sliding friction experiments were conducted in vacuum with single crystal silicon carbide (0001) surface in contact with transition metals (tungsten, iron, rhodium, nickel, titanium, and cobalt), copper, and aluminum. The hexagon shaped cracking and fracturing of silicon carbide that occurred is believed to be due to cleavages of both the prismatic and basal planes. The silicon carbide wear debris, which was produced by brittle fracture, slides or rolls on both the metal and silicon carbide and produces grooves and indentations on these surfaces. The wear scars of aluminum and titanium, which have much stronger chemical affinity for silicon and carbon, are generally rougher than those of the other metals. Fracturing and cracking along the grain boundary of rhodium and tungsten were observed. These may be primarily due to the greater shear moduli of the metals.

Miyoshi, K.↗
NASA NTRS1978

NR-150B2 adhesive development

Adhesive based polyimide solutions which are more easily processed than conventional aromatic polyimide systems and show potential for use for extended times at 589K are discussed. The adhesive system is based on a solution containing diglyme as the solvent and 2,2 bis(3',4'-dicarboxyphenyl)hexafluoropropane, paraphenylenediamine, and oxydianiline. The replacement of N-methylpyrrolidone with diglyme as the solvent was found to improve the adhesive strengths of lap shear samples and simplify the processing conditions for bonding both titanium and graphite fiber/polyimide matrix resin composites. Information was obtained on the effects of various environments including high humidity, immersion in jet fuel and methylethylketone on aluminum filled adhesive bonds. The adhesive was also evaluated in wide area bonds and flatwise tensile specimens using titanium honeycomb and composite face sheets. It was indicated that the developed adhesive system has the potential for use in applications requiring long term exposure to at least 589K (600 F).

Blatz, P. S.↗
NASA NTRS1978

Effect of oxygen and nitrogen interactions on friction of single-crystal silicon carbide

Friction studies were conducted with single-crystal silicon carbide contacting silicon carbide and titanium after having been exposed to oxygen and nitrogen in various forms. After they had been sputter cleaned, the surfaces were (1) exposed to gaseous oxygen and nitrogen (adsorption), (2) ion bombarded with oxygen and nitrogen, or (3) reacted with oxygen (SiC only). Auger emission spectroscopy was used to determine the presence of oxygen and nitrogen. The results indicate that the surfaces of silicon carbide with reacted and ion-bombarded oxygen ions give higher coefficients of friction than do argon sputter-cleaned surfaces. The effects of oxygen on friction may be related to the relative chemical, thermodynamic properties of silicon, carbon, and titanium for oxygen. The adsorbed films of oxygen, nitrogen, and mixed gases of oxygen and nitrogen on sputter-cleaned, oxygen-ion bombarded, and oxygen-reacted surfaces generally reduce friction. Adsorption to silicon carbide is relatively weak.

Miyoshi, K.↗
NASA NTRS1977

Boron/aluminum skins for the DC-10 aft pylon

Three boron/aluminum aft pylon 'boat tail' skins were designed, fabricated, and installed on three DC-10 aircraft for a five-year flight service demonstration test. Inspection and tests of the skins will establish the ability of the composite to withstand long-time flight service exposures to high temperatures, sonic fatigue, and flutter. The results of a preliminary testing program yielded room and elevated temperature data on the tension, compression, in-plane shear, interlaminar shear, bolt bearing, and tension fatigue properties of the oriented eleven-ply boron/aluminum laminates, and this information, together with a stress analysis, was used to obtain Federal Aviation Administration approval. Present state-of-the-art technology was used in the fabrication of the skins, and these were installed on the existing titanium substructure with the same number and size mechanical fasteners as are used for the present titanium skins.

Elliott, S. Y.↗
NASA NTRS1977

The search for the cause of the low albedo of the moon

The effects of different weathering processes on the albedo of the lunar surface cover is discussed. The surface chemical composition of numerous lunar soil and pulverized rock samples was determined by auger electron spectroscopy. The optical albedo of these samples was also measured. The chemical concentration of iron and titanium is greater on the surface of soil samples than it is on the surface of crushed rock samples with similar bulk composition, whereas the albedo of soil samples is lower than that of the crushed rock samples. A correlation is presented between the surface iron + titanium content and the albedo. Results of solar wind simulation experiments show that irradiation of crushed lunar rock samples with a small dose (corresponding to 3000 years of solar wind) of 2-keV energy protons changed the surface chemistry of the rock to that of the soil. A much larger dose of protons (corresponding to 30,000 years of solar wind) was needed to darken crushed rock to the albedo of the soil of similar bulk chemical composition. The mechanism of darkening by solar wind is discussed, and its effectiveness is compared to that of other darkening processes.

Gold, T.↗
NASA NTRS1977

High temperature composite bonding with PPQ

A polyphenylquinoxaline (PPQ) was evaluated as a high temperature adhesive for joining polyimide graphite laminates (PI/Gr) to PI/Gr, PI/Gr to titanium (Ti), and Ti to Ti. The effect of polymer molecular weight, processing parameters, 3-day water boil, and 316 C (600 F) aging in air upon lap shear strengths is presented. Titanium to Ti climbing drum peel and PI/Gr to polyimide glass honeycomb flatwise tensile strengths are also presented.

Hergenrother, P. M.↗
NASA NTRS1977

Toroidal tank evaluation

The reported study had been conducted to determine the feasibility of developing toroidal tanks for an auxiliary propulsion system that could be integrated into a Pioneer spin-stabilized spacecraft. The system evaluated consisted of two toroidal tanks equipped with surface tension devices. One tank is intended for nitrogen tetroxide, the other for monomethylhydrazine. The study included the definition of a propellant acquisition system concept that could satisfy the requirements of a spinning tank. It was found that an oxidizer tank spin rate of 76 rpm and a fuel tank spin rate of 110 rpm would be required to produce liquid loss from the acquisition system during spacecraft operation. An investigation showed that toroidal tanks can be fabricated with present technology using either titanium or aluminum alloys. The preferred material would be titanium because of its significantly higher strength.

Fester, D. A.↗
NASA NTRS1978

Study of heat sink thermal protection systems for hypersonic research aircraft

The feasibility of using a single metallic heat sink thermal protection system (TPS) over a projected flight test program for a hypersonic research vehicle was studied using transient thermal analyses and mission performance calculations. Four materials, aluminum, titanium, Lockalloy, and beryllium, as well as several combinations, were evaluated. Influence of trajectory parameters were considered on TPS and mission performance for both the clean vehicle configuration as well as with an experimental scramjet mounted. From this study it was concluded that a metallic heat sink TPS can be effectively employed for a hypersonic research airplane flight envelope which includes dash missions in excess of Mach 8 and 60 seconds of cruise at Mach numbers greater than 6. For best heat sink TPS match over the flight envelope, Lockalloy and titanium appear to be the most promising candidates

Vahl, W. A.↗
NASA NTRS1977

Composite pressure vessels for the Space Shuttle Orbiter

During the development of the Space Shuttle Orbiter propulsion and environmental control subsystems it was recognized that use of composite pressure vessels with load sharing liners could provide significant weight savings for high pressure gas containment. A program is described which was undertaken to assess the utility for orbiter applications of titanium 6Al-4V and Inconel 718 liners overwrapped with Kevlar fibers. Vessel characteristics, design features and test results are presented along with brief descriptions of processes and nondestructive evaluation techniques. The resolutions of anomalies and development of design are also presented. Fracture control as applied to the orbiter composite vessels is briefly discussed. Five of the seven titanium lined vessels in the program experienced premature cyclic failures. These failures were shown to be primarily due to metallurgical anomalies rather than an inherent composite design problem. A nonfragmentary leakage mode of failure was demonstrated at operating pressures. The composite designs will be approximately 25 percent lighter than their all metal counterparts.

Ecord, G. M.↗
NASA NTRS1977

Computer-generated maps of lunar composition from gamma-ray data

Processing of some of the gamma-ray data obtained by Apollo 15 and 16 has been accomplished by analyzing count rates in three energy bands. The count rate variations in the three energy bands are due in various degrees to thorium, uranium, potassium, iron and titanium. The mapping which results from the gamma-ray count rates has an effective resolution of about two degrees. Regions of high titanium content in certain maria, the low values of iron in a zone of the central equatorial highland and the relatively low value of iron near Archimedes are noted.

Arnold, J. R.↗
NASA NTRS1977

A TiO2 abundance map for the northern maria

A map of TiO2 abundance for most of the northern maria is presented. The telescopic data base used is the 0.38/0.56-micron ratio mosaic from Johnson et at. (1977). The titanium content has been estimated using the correlation established by Charette et al. (1974). The combination of observational, processing, and calibration errors indicates that the TiO2 map is accurate to + or - 2% (wt% TiO2) for high TiO2 content (more than 5%) and + or - 1% for low values of TiO2. Analysis of the lunar sample and telescopic data suggests strongly that the spectral parameter mapped is sensitive primarily to TiO2 abundance in the range 3-9% and does not correlate directly with iron content. It is suggested, however, that for the low TiO2 mare regions (less than 2-3% TiO2) there may be a relation between the spectral ratio and iron content and that some of the reddest mare areas in the Imbrium region may have low iron contents as well as low titanium abundances.

Johnson, T. V.↗