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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Activation analysis of admixtures in certain semiconductive materials

The use of extractions and chromatographic operations to separate macrobases, and to divide elements into groups convenient for gamma-spectrometric analysis is discussed. Methods are described for the activation detection of some impurities in silicon, arsenic, thallium, and trichloromethylsilane, on the basis of the extraction properties of bis(2-chlorethyl ether) and dimethylbenzylalkylammonium chloride. A schematic diagram of the extraction separation of elements-admixture is presented showing the aqueous and organic phases. The content percentage of the various elements are given in tables.

Artyukhin, P. I.↗
NASA NTRS1978

Surface temperatures and glassy state investigations in tribology, part 1

The research in this report is divided into two categories: (1) lubricant rheological behavior, and (2) thermal behavior of a simulated elastohydrodynamic contact. The studies of the lubricant rheological behavior consists of high pressure, low shear rate viscosity measurements, viscoelastic transition measurements, by volume dilatometry, dielectric transitions at atmospheric pressure and light scattering transitions. Lubricant shear stress-strain behavior in the amorphous glassy state was measured on several fluids. It appears clear from these investigations that many lubricants undergo viscoplastic transitions in typical EHD contacts and that the lubricant has a limiting maximum shear stress it can support which in turn will determine the traction in the contact except in cases of very low slide-roll ratio. Surface temperature measurements were made for a naphthenic mineral oil and a polyphenyl ether. The maximum surface temperature in these experiments was approximately symmetrical about the zero slide-roll ration except for absolute values of slide-roll ratio greater than about 0.9. Additional surface temperature measurements were made in contacts with rough surfaces where the composite surface roughness was approximately equal to the EHD film thickness. A regression analysis was done to obtain a predictive equation for surface temperatures as a function of pressure, sliding speed, and surface roughness. A correction factor for surface roughness effects to the typical flash temperature analysis was found.

Winer, W. O.↗
NASA NTRS1978

Development and evaluation of elastomeric materials for geothermal applications

A material for a casing packer for service for 24 hours in a geothermal environment was developed by synthesis of new elastomers and formulation of available materials. Formulation included use of commercial elastomer gumstocks and also crosslinking of plastic (high Tg) materials. Fibrous reinforcement of fluorocarbon rubbers was emphasized. Organic fiber reinforcement did not increase hot properties significantly. Glass fiber reinforcement gave significant increase in tensile properties. Elongation was reduced, and the glass-reinforced composition examined so far did not hold up well in the geothermal environment. Colloidal asbestos fibers were also investigated. A few experiments with polyphenyl ether gave material with low tensile and high compression set. Available high styrene SBR compositions were studied. Work to date suggests that new synthetic polymers will be required for service in geothermal environments.

Mueller, W. A.↗
NASA NTRS1978

Study of dynamic emission spectra from lubricant films in an elastohydrodynamic contact using Fourier transform spectroscopy

Infrared emission spectra were obtained through a diamond window from lubricating fluids in an operating sliding elastohydrodynamic contact and analyzed by comparison with static absorption spectra under similar pressures. Different loads, shear rates and temperatures were used. Most of the spectra exhibited polarization characteristics, indicating directional alignment of the lubricant in the EHD contact. Among the fluids studied were a "traction" fluid, an advanced ester, and their mixtures, a synthetic paraffin, a naphthenic reference fluid (N-1), both neat and containing 1 percent of p-tricresyl phosphate as an anti-wear additive, and a C-ether. Traction properties were found to be nearly proportional to mixture composition for traction fluid and ester mixtures. The anti-wear additive reduced traction and fluid temperature under low loads but increased them under higher loads, giving rise to formation of a friction polymer.

Lauer, J. L.↗
NASA NTRS1978

Organic geochemical studies on kerogen precursors in recently deposited algal mats and oozes

The same kerogen-like residue from the algal mats and oozes at Laguna Mormona, Baja California, is examined following degradation by saponification, alkaline KMnO4 oxidation, and HBr treatment. For comparison, pyrolytic degradation is performed for the residue and five others, two of which are obtained from algal mats at Baffin Bay, Texas. Major conclusions are that (1) Saponification of a residue specimen from the algal-ooze residue results in minor amounts of components bonded to it as esters; (2) Alkaline KMnO4 oxidation reveals that the same residue consists of a cross-linked aliphatic nucleus with additional components attached to it as esters; (3) the major products from pyrolysis of the residue include phytenes, pristenes, sterenes, and triterpenes; and (4) the HBr treatment yielded only one product, indicating the absence of a large number of ether-linkages readily cleaved by HBr.

Philp, R. P.↗
NASA NTRS1979

Magnetic shielding in a low temperature torsion pendulum experiment

A new type of ether drift experiment searches for anomalous torques on a permanent magnet. A torsion pendulum is used at liquid helium temperature, so that superconducting cylinders can be used to shield magnetic fields. Lead shields attenuate the earth's field, while Nb-Sn shields fastened to the pendulum contain the fields of the magnet. The paper describes the technique by which the earth's field can be reduced below 0.0001 G while simultaneously the moment of the magnet can be reduced by a factor 7 x 10 to the 4th.

Phillips, P. R.↗
NASA NTRS1979

Determination of physical and chemical states of lubricants in concentrated contacts, part 1

A Fourier emission infrared microspectrometer, set up on a vibration-proof optical table and interfaced to a dedicated minicomputer, was used to record infrared emission spectra from elastohydrodynamic bearing contacts. Its range was extended to cover the entire mid-infrared from 2 to 15 micron. A series of experiments with 5P4E polyphenyl ether showed the existence of a temperature gradient through the lubricant in an ehd contact, which is perpendicular to the flow direction. The experiments also show marked polarization of some of the spectral bands, indicating a molecular alignment. Alignment is less evident at high pressure than at low pressure. To account for this behavior, a model is suggested along the lines developed for the conformational changes observed in long-chain polymers when subjected to increased pressure--to accommodate closer packing, molecules become kinked and curl up. Experiments with a traction fluid showed periodic changes of flow pattern associated with certain spectral changes. These observations will be studied further. A study by infrared attenuated total reflection spectrophotometry was undertaken to determine whether gamma irradiation would change polyethylene wear specimens. The results were negative.

Lauer, J. L.↗
NASA NTRS1979

Synthesis and biological screening by novel hybrid fluorocarbon hydrocarbon compounds for use as artificial blood substitutes

A series of hybrid fluorochemicals of general structure R(1)R(2)R(3)CR(4) was prepared where the R(i)'s (i=1,2,3) is a saturated fluoroalkyl group of formula C sub N F sub 2n+1, and R(4) is an alkyl group C sub n H sub 2n+1 or a related moiety containing amino, ether, or ester functions but no CF bonds. Compounds of this class containing approximately eight to twenty carbons total have physical properties suitable for use as the oxygen carrying phase of fluorochemical emulsion artificial blood. The chemical synthesis, and physical and biological testing of pure single isomers of the proposed artificial blood candidate compounds are included. Significant results are given.

Moacanin, J.↗
NASA NTRS1980

Steady-state wear and friction in boundary lubrication studies

A friction and wear study was made at 20 C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25 min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible steady-state wear rates and steady-state friction coefficients were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods.

Loomis, W. R.↗
NASA NTRS1980

Effects of centrifugation stress on pituitary-gonadal function in male rats

The effects of centrifugation for various lengths of time on circulating levels of luteinizing hormone (LH) and testosterone in male rats were investigated. In a chronic 52-day experiment, centrifugation at 4.1 G significantly reduced LH and testosterone levels for the entire period. Centrifugation at 2.3 G had less effect inasmuch as LH levels were not significantly decreased and testosterone levels were significantly reduced only during the first few days of centrifugation. In more acute experiments, centrifugation at 4.1 G for 4 h resulted in reduced testosterone levels, whereas centrifugation for 15 min did not significantly alter the hormone levels. These results indicate that centrifugation can decrease circulating LH and testosterone levels if the gravitational force is of sufficient magnitude and is maintained for a period of hours. Chronic centrifugation may also inhibit the acute excitatory response of LH to handling and ether stress.

Gray, G. D.↗
NASA NTRS1980

Energy status and oxidation reduction status in rat liver at high altitude /3.8 km/

Adult male rats were exposed to 3.8-km altitude for intervals ranging from 1 h-60 d. Liver samples were taken under light ether anesthesia and were examined by enzymatic analyses. Within 1-6 h of hypoxic exposure, ATP levels decreased while ADP and AMP levels increased, producing a fall in calculated ATP/ADP and adenylate charge ratios. Concurrently, lactate/pyruvate and alpha-glycerophosphate/dihydroxyacetone phosphate ratios increased markedly. Direct measurements of cellular pyridine nucleotides indicated increased NADH/NAD and NADPH/NADP ratios. Levels of total adenosine phosphates and pyridine nucleotides decreased in a significant accompanying response. Many metabolite levels and calculated ratios returned to near-normal values within 1 week of exposure, indicating secondary intracellular adjustments to hypoxic stress; however, persistence of that stress is reflected in lactate concentrations and both substrate redox ratios. Results support and explore concepts that increased oxidation-reduction status and decreased energy status are primary events during hypoxia.

Reed, R. D.↗
NASA NTRS1980

Structural wood panels with improved fire resistance

Structural wood paneling or other molded wood compositions consisting of finely divided wood chips, flour, or strands are bound together and hot pressed with a modified novolac resin which is the cured product of a prepolymer made from an aralkyl ether or halide with a phenol and a hardening agent such as hexamethylene tetramine. The fire resistance of these articles is further improved by incorporating in the binder certain inorganic fillers, especially a mixture of ammonium oxalate and ammonium phosphate.

Sawko, P. M.↗
NASA NTRS1981

Development of urethane coating and potting material with improved hydrolytic and oxidative stability

A series of saturated hydrocarbon based urethanes was prepared and characterized for hydrolytic and oxidative stability. A series of ether based urethanes was used as a basis for comparison. The alkane base urethanes were found to be hydrolytically and oxidatively stable and had excellent electrical properties. The alkane based materials absorbed little or no water and were reversion resistant. There was little loss in hardness or weight when exposed to high temperature and humidity. Dielectric properties were excellent and suffered little adverse effects from the high temperature/humidity conditions. The alkane based urethanes were not degraded by ozone exposure.

Morris, D. E.↗
NASA NTRS1981

New polymers for phase partitioning

The synthesizing of several polyethylene glycols having crown ethers attached is reported. This work led to the identification of three new polymer types which promise to be more effective at selectively binding specific cell types. Work was completed on identification of chemical properties of the new polymer crowns and on development of new techniques for determination of polymer-phase composition.

Harris, J. M.↗
NASA NTRS1980

Temperature gradients through EHD films and molecular alignment evidenced by infrared spectroscopy

Partial and complete emission band reversals have been observed in the infrared emission spectra from portions of operating sliding contacts. An elementary analysis has been carried out to show that partial reversals are due to temperature gradients in the fluid film - the film acts both as a radiation-emitter and absorber, and that total reversals - an emission spectrum appears as an absorption spectrum are likely to be due to a continuum source, such as hot solid asperities. The total energy radiated under the latter conditions exceeds that under the others. A decrease in gap width with increased load was accompanied by a dramatic spectral change in the case of 5P4E polyphenyl ether, which is indicative of molecular alignment.

King, V. W.↗
NASA NTRS1980

Formate esters of 1,2-ethanediol - Major decomposition products of p-dioxane during storage

Research done on detecting the contaminants of p-dioxane that cause a positive response for highly reactive acyl groups is discussed. Attention is given to the fact that the positive hydroxamate response might indicate an unsuspected hazard. It is found that all acyl groups transferred are formyl groups, and the mono- and diformates of 1,2-ethanediol are identified as major sources of this activity. It is also found that the formate esters are formed by way of peroxide intermediates. Concentrations of the formate ester group as high as 1.8 M are found in partially consumed bottles of dioxane but not in other common ethers stored under similar conditions. Attention is called to the possibility that the exposure to the glycol formates is probably much wider than expected. It is noted that by purging containers of dioxane with nitrogen each time they are opened and storing them in the cold away from light can prevent both the economic loss and possible health hazard caused by contamination with peroxide and formate ester.

Jewett, D.↗
NASA NTRS1983

Stable Polyurethane Coatings for Electronic Circuits

Alkane-based polyurethanes resist deterioration while maintaining good dielectric properties. Weight loss after prolonged immersion in hot water far less for alkane-based polyurethanes than for more common ether based polyurethanes, at any given oxygen content. Major uses of polyurethanes are as connector potting materials and conformal coatings for printed circuit boards.

Morris, D. E.↗
NASA NTRS1981

Aluminum ion-containing polyimide adhesives

A meta-oriented aromatic diamine is reacted with an aromatic dianhydride and an aluminum compound in the presence of a water or lower alkanol miscible ether solvent to produce an intermediate polyamic acid. The polyamic acid is then converted to the thermally stable, metal ion-filled polyimide by heating in the temperature range of 300 C to produce a flexible, high temperature adhesive.

St.clair, A. K.↗