Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “low-temperature”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Calculation of body-centered-cubic lattice sums with an application to ferromagnetism.

The lattice sums for the bcc lattice are recalculated using the method of Flax and Raich to obtain more general expressions, valid for all temperatures, in terms of a Langevin function and its derivatives. Formulas are presented which enable easy numerical evaluation. A comparison with well-known low-temperature expansions and with the results of direct numerical integration demonstrates the validity at low temperatures of the more general expressions calculated here.

Wintucky, E. G.↗
NASA NTRS1973

Development of design allowables data for adhesives for attaching reusables surface insulation, addendum 1A

The task consisted of conducting mechanical and thermal tests to establish design allowables data on a new room temperature vulcanizing (RTV) silicone adhesive, X3-6004. Low modulus, coupled with relatively low density and good low-temperature properties of this adhesive, places it in contention as a candidate for attaching reusable surface insulation on the space shuttle. Data obtained show that the modulus values of X3-6004 are significantly lower than those of RTV-560 and the other three adhesives characterized at test temperatures from 550 to -175 F. At -175, -200 and -270 F, the modulus of X3-6004 is approximately the same as GE RTV-560 and the other three silicone adhesives. The X3-6004 adhesive exhibits good processing properties. It has a 12 percent lower density than RTV-560. Although lower in overall strength properties as compared to the other adhesives in the program, X3-6004 has adequate adhesion to 2024T81 aluminum to compete as an adhesive for attaching reusable surface insulation. It does exhibit some tendency to revert and soften at temperatures above 350 F when in a confined area.

Owen, H. P.↗
NASA NTRS1972

Far-infrared brightness temperatures of the planets.

An airborne telescope operating in an altitude range from 45,000 to 50,000 feet together with a low-temperature germanium bolometer and six cooled filters were used in an investigation of the temperatures of the planets. The measurements conducted provide a basis for absolute calibration in the far infrared, confirm the high effective temperature and internal power of Jupiter, and give information on the far-infrared opacities and emissivities of the four bright planets.

Armstrong, K. R.↗
NASA NTRS1972

Viscous flow behavior of lunar compositions 14259 and 14310.

The flow characteristics of lunar compositions 14310 and 14259 have been determined over a wide range of viscosity. The temperature ranges covered by the measurements are 1270 to 1440 C and 700 to 825 C for the 14310 composition and 1154 to 1431 C and 700 to 820 C for the 14259 composition. Reliable data could not be obtained over the intermediate ranges of temperature because of the occurrence of crystallization. The apparent activation energies for viscous flow in the high-temperature and low-temperature regions are respectively about 60 and 160 kcal/gm at for the 14310 composition and 60 and 170 kcal/gm at for the 14259 composition.

Cukierman, M.↗
NASA NTRS1973

Mechanical properties of electron-beam-melted molybdenum and dilute Mo-Re alloys.

Study of Mo-Re alloys aimed at examining the effects of small rhenium additions on the low-temperature ductility of molybdenum and determining the mechanical properties of dilute Mo-Re alloys. The results obtained indicate that high-purity Mo-Re alloys have ductile-brittle transition temperatures considerably lower than those for unalloyed molybdenum and that rhenium promotes normal solid-solution strengthening in molybdenum at elevated temperatures.

Klopp, W. D.↗
NASA NTRS1972

Reference data for thermocouple materials below the ice point.

Standard thermoelectric data have been determined for four thermocouple combinations used below the ice point: commercial types E, K, and T and the special combination of KP vs Au-0.07 at.% Fe. Power series coefficients necessary to generate E = f(T) data for these combinations are given. In addition, extensive tests were carried out to ascertain the variability between materials from different manufacturers. Typical wires processed for low-temperature usage often have slightly thermoelectric properties (up to 1%) from those, nominally identical, wires made for high-temperature applications. Generally, type E is the most satisfactory standardized commercial combination. The Au-0.07 at.% Fe material has been examined in particular detail, because it is not yet an ISA standard material. It has excellent sensitivity in the liquid helium/liquid hydrogen temperature range and a nearly linear thermovoltage at higher temperatures.

Sparks, L. L.↗
NASA NTRS1973

Role of Hf and Zr in the hydrogen embrittlement of Ta and Cb alloys

Investigation of the hydrogen embrittlement of aged Ta alloy T-111 (Ta-8W-2Hf) and similar Ta and Cb alloys. It is found that aging ternary Ta alloys such as T-111 near 1040 C for 1000 hr or longer increases their sensitivity to low-temperature hydrogen embrittlement. Segregation of Hf to grain boundaries during aging causes embrittlement upon testing at -196 C and is responsible for the observed hydrogen embrittlement. Binary Ta and Cb alloys, Ta-2Hf and Cb-1Zr, are not susceptible to hydrogen embrittlement under the conditions of this study and did not exhibit grain boundary segregation of Hf or Zr. Ternary alloys Ta-8W-.5Hf, Ta-8W-1Hf, and Ta-4W-2Hf are superior to T-111 for containment of alkali metals in that they do not exhibit aging embrittlement. However, these alloys in the aged condition are susceptible to hydrogen embrittlement.

Stephens, J. R.↗
NASA NTRS1973

Prospects for obtaining metallic hydrogen with spherical presses

Description of a split-sphere apparatus modified for use at low temperature and affording a possible method for compressing molecular hydrogen to a pressure in excess of 1 Mbar and for converting it to the metallic state. The construction costs of the apparatus are relatively low and the amount of liquid helium required for low-temperature operation is readily obtainable with modern liquefiers.

Spain, I. L.↗
NASA NTRS1973

Temperature, stress, and annealing effects on the luminescence from electron-irradiated silicon

Low-temperature photoluminescence spectra are presented for Si crystals which have been irradiated with high-energy electrons. Studies of isochronal annealing, stress effects, and the temperature dependences of the luminescence are used to discuss the nature of the luminescent transitions and the properties of defects. Two dominant bands present after room-temperature anneal of irradiated material are discussed, and correlations of the properties of these bands are made with known Si defects. A band between 0.8 and 1.0 eV has properties which are related to those of the divacancy, and a band between 0.6 and 0.8 eV has properties related to those of the Si-G15(K) center. Additional peaks appear in the luminescence after high-temperature anneal; the influence of impurities and the effects of annealing of these lines are discussed.

Jones, C. E.↗
NASA NTRS1973

Recombination luminescence from electron-irradiated Li-diffused Si

Lithium doping has a dramatic effect on the low-temperature photoluminescence of electron-irradiated Si. In oxigen-lean Si with Li doping, a new irradiation-dependent luminescence band between 0.75 and 1.05 eV is observed, which is dominated by a zero-phonon peak at 1.045 eV. This band is believed to be due to radiative transitions involving a Li-modified divacancy. This band is present also in oxygen-rich, Li-diffused Si and is accompanied by bands previously related to the Si-G15(K) center and the divacancy. The intensities of the Li-modified divacancy and Si-G15(K) center bands are relatively weak in the oxygen-rich material, apparently due to the formation of lithium-oxygen complexes which reduce the concentration of unassociated interstitial Li and O.

Johnson, E. S.↗
NASA NTRS1973

Volatile element chemistry of selected lunar, meteoritic, and terrestrial samples

Using vacuum pyrolysis and high resolution mass spectrometry, a study is made of the gas release patterns of representative lunar samples, meteorites, terrestrial samples, and synthetic samples doped with various sources of carbon and nitrogen. The pyrolytic gas evolution patterns were intercorrelated, allowing an assessment of the possible sources of the volatilizable material in the lunar samples to be made. Lightly surface adsorbed species and more strongly chemisorbed species are released from ambient to 300 C and from 300 to 500 C, respectively. The low-temperature volatiles (less than 500 C) derived from various chondrites correlate well with the gas evolution patterns of volatile-rich samples, as for example 74220 and 61221. Solar wind entrapped species and molecules derived from reactions probably in the grain surfaces are evolved from about 500 to 700 C, respectively. Solar wind implanted C, N, and S species are generated from 750 to 1150 C, probably by reaction with the mineral matrix during the annealing process. Possible indigenous and/or refractory carbide, nitride, and sulfide C, N, and S are released in the region from 1200 C to fusion.

Simoneit, B. R.↗
NASA NTRS1973

Experimental interstellar organic chemistry - Preliminary findings

Review of the results of some explicit experimental simulation of interstellar organic chemistry consisting in low-temperature high-vacuum UV irradiation of condensed simple gases known or suspected to be present in the interstellar medium. The results include the finding that acetonitrile may be present in the interstellar medium. The implication of this and other findings are discussed.

Khare, B. N.↗
NASA NTRS1952

Flame Speeds of Methane-Air, Propane-Air, and Ethylene-Air Mixtures at Low Initial Temperatures

Flame speeds were determined for methane-air, propane-air, and ethylene-air mixtures at -73 C and for methane-air mixtures at -132 C. The data extend the curves of maximum flame speed against initial mixture temperature previously established for the range from room temperature to 344 C. Empirical equations for maximum flame speed u(cm/ sec) as a function of initial mixture temperature T(sub O) were determined to be as follows: for methane, for T(sub O) from 141 to 615 K, u = 8 + 0.000160 T(sub O)(exp 2.11); for propane, for T(sub O) from 200 to 616 K, u = 10 + 0.000342 T(sub O)(exp 2.00); for ethylene, for T(sub O) from 200 to 617 K, u = 10 + 0.00259 T(sub O)(exp 1.74). Relative flame speeds at low initial temperatures were predicted within approximately 20 percent by either the thermal theory as presented by Semenov or by the diffusion theory of Tanford and Pease. The same order was found previously for high initial temperatures. The low-temperature data were also found to extend the linear correlations between maximum flame speed and calculated equilibrium active-radical concentrations, which were established by the previously reported high-temperature data.

Dugger, Gordon L↗
NASA NTRS1951

Ignition-delay Characteristics in Modified Open-cup Apparatus of Several Fuels with Nitric Acid Oxidants Within Temperature Range 70 to 105 Degrees F

Fluid properties and low-temperature ignition delays were obtained for approximately 90 fuel-oxidant combinations. A red fuming nitric acid containing approximately 3 percent water and 19 percent nitrogen tetroxide froze at approximately -87 degrees F and ignited several low-viscosity fuel blends of aromatic amines in triethylamine at -76 degrees F and lower. With this acid, the following average ignition delays were obtained with a blend of 30 percent o-toluidine in triethylamine: ...

FUEL SYSTEMS - ENGINES, ROCKET↗
NASA NTRS1952

Spreading of Exhaust Jet from 16 Inch Ream Jet at Mach Number 2.0 / Fred Wilcox, Donald Pennington

An investigation of the jet-spreading characteristics of a 16 inch ram-jet engine was conducted in the 8 by 6 foot supersonic tunnel at a Mach number of 2.0; both a converging nozzle having a contraction ratio of 0.71 and a cylindrical extension to the combustion chamber were used. The jet boundaries determined by means of pitot pressure surveys were compared with boundaries calculated from one-dimensional continuity and momentum relations. For the cylindrical nozzle, the jet reaches its maximum diameter, 4 percent greater than calculated, about 0.6 nozzle-exit diameter downstream of the nozzle exit. The maximum diameter for the converging nozzle was 7 percent greater than calculated from one dimensional relations and occurred from 1 to 1.5 nozzle-exit diameters downstream of the exit. Non dimensional maximum jet diameters agreed closely with results of an investigation by Rousso and Baughman; these data were obtained with low-temperature jets exhausting into a stream at a Mach number of 1.91 from nozzles having exit diameters of 0.75 inch.

INTERFERENCE, JET-MISSILES↗
NASA NTRS1957

Nonmetallic Material Compatibility with Liquid Fluorine

Static tests were made on the compatibility of liquid fluorine with several nonmetallic materials at -3200 F and at pressures of 0 and 1500 pounds per square inch gage. The results are compared with those from previous work with gaseous fluorine at the same pressures, but at atmospheric temperature. In general, although environmental effects were not always consistent, reactivity was least with the low-temperature, low-pressure liquid fluorine. Reactivity was greatest with the warm, high-pressure gaseous fluorine. None of the liquids and greases tested was found to be entirely suitable for use in fluorine systems. Polytrifluorochloroethylene and N-43, the formula for which is (C4F9)3N, did not react with liquid fluorine at atmospheric pressure or 1500 pounds per square inch gage under static conditions, but they did react when injected into liquid fluorine at 1500 pounds per square inch gage; they also reacted with gaseous fluorine at 1500 pounds per square inch gage. While water did not react with liquid fluorine at 1500 pounds per square inch gage, it is known to react violently with fluorine under other conditions. The pipe-thread lubricant Q-Seal did not react with liquid fluorine, but did react with gaseous fluorine at 1500 pounds per square inch gage. Of the solids, ruby (Al2O3) and Teflon did not react under the test conditions. The results show that the compatibility of fluorine with nonmetals depends on the state of the fluorine and the system design.

Price, Harold G , Jr↗
NASA NTRS1960

Equipment for Thermal-Balance Studies in the Langley Instrument Research Division

The Langley Research Center is in the process of obtaining emissivity measuring apparatus. This apparatus will be used to measure the solar absorptance and low-temperature emittance of space-vehicle materials. Two types of instrumentation will be used. One type will be the total hemispherical emissivity apparatus being constructed at this Center. The other will be double-beam photoelectric ratio-recording spectrophotometer apparatus which is being purchased.

Spiers, Robert B., Jr.↗