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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Generation of long time creep data on refractory alloys at elevated temperatures

Creep tests were conducted on two tantalum alloys (ASTAR 811C and T-111 alloy), on a molybdenum alloy (TZM), and on CVD tungsten. The T-111 alloy 1% creep life data have been subjected to Manson's station function analysis, and the progress on this analysis is described. In another test program, the behavior of T-111 alloy with continuously varying temperatures and stresses has been studied. The results indicated that the previously described analysis predicts the observed creep behavior with reasonable accuracy. In addition to the T-111 test program, conventional 1% creep life data have been obtained for ASTAR 811C alloy. Previously observed effects of heat treatment on the creep strength of this material have been discussed and a model involving carbide strengthening primarily at the grain boundaries, rather than in a classical dispersion hardening mechanism, has been proposed to explain the observed results.

Sheffler, K. D.↗
NASA NTRS1972

Neutrons produced by known energies of ions abundant in space

Particle accelerator radiation measurements are applied to the problem of calculating biological dose from radiation produced in the walls of a spacecraft by various ions in space. Neutrons, one of the products of the interactions of energetic ions with matter, are usually quite penetrating and have large values of Q.F. or R.B.E. Ions of helium, boron, carbon, nitrogen, and oxygen were accelerated and directed onto target materials of copper or tantalum. The secondary neutron production was determined. Studies were made of the angular distribution and an inferred neutron spectrum was calculated from activities of threshold reaction detectors.

Wadman, W. W., III↗
NASA NTRS1971

Study of structural behavior of thin films

The work directed towards developing methods of increasing the strength of thin boron films is reported. The program was divided into two main parts. The first involved the improvement of methods for the measurement of the strength of thin films. The second was a study of the effect of condensation of deposition temperature on the strength of the films. Techniques were developed for depositing boron films onto both sides of thin titanium and tantalum foils. Small dogbone sections of boron were made by masking. Strain gauges were then mounted on these to measure failure strains when the films were loaded in tension. Test results were consistent with those obtained by flexure tests. The most important flaws in the boron films appeared to have been generated by either small globules of boron ejected from the melt or small particles (possibly boron dust) on the substrate prior to deposition.

Feakes, F.↗
NASA NTRS1972

Interactions between creep, fatigue and strain aging in two refractory alloys

The application of low-amplitude, high-frequency fatigue vibrations during creep testing of two strain-aging refractory alloys (molybdenum-base TZC and tantalum-base T-111) significantly reduced the creep strength of these materials. This strength reduction caused dramatic increases in both the first stage creep strain and the second stage creep rate. The magnitude of the creep rate acceleration varied directly with both frequency and A ratio (ratio of alternating to mean stress), and also varied with temperature, being greatest in the range where the strain-aging phenomenon was most prominent. It was concluded that the creep rate acceleration resulted from a negative strain rate sensitivity which is associated with the strain aging phenomenon in these materials. (A negative rate sensitivity causes flow stress to decrease with increasing strain rate, instead of increasing as in normal materials). By combining two analytical expressions which are normally used to describe creep and strain aging behavior, an expression was developed which correctly described the influence of temperature, frequency, and A ratio on the TZC creep rate acceleration.

Sheffler, K. D.↗
NASA NTRS1972

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

Stephens, J. R.↗
NASA NTRS1972

Evaluation of zirconia, thoria and zirconium diboride for advanced resistojet use

A literature survey was conducted to collect material properties data on all advanced high temperature materials. Three of these, Y2O3-stabilized ZrO2, ThO2, and ZrB2 with additives of C and SiC were selected for further study. Stabilized ZrO2 and ThO2 were found to have higher temperature oxidation resistance than any metal and great potential for use in advanced biowaste resistojets. ZrO2 has a lower electrical resistivity and sublimation and a higher creep endurance strength. ZrO2 and ThO2 tubular heat exchangers, electrically heated indirectly, were evaluated in short tests to about 1900 K in flowing CO2. ZrO2 was subjected to N2, H2, H2O and vacuum as well. X-ray diffraction and fluorescence analyses were made. The metal-to-ceramic seal technology for ZrO2 and ThO2 was developed using chemical vapor deposition of tantalum for metallizing and 82 Au - 18 Ni filler braze.

Page, R. J.↗
NASA NTRS1972

Development study of compositions for advanced wrought nickel-base superalloys

Using NASA IIb as a base composition, the effects of five key elements (carbon, tungsten, tantalum, aluminum, and hafnium) on resultant properties were investigated in an effort to optimize the composition and derive new wrought high temperature alloys with improved strength characteristics. A total of nineteen compositions were melted, extruded, and rolled to bar stock using thermomechanical processing. Both full and partial solution heat treatments were developed for the compositions. Tensile properties from room temperature to 1800 deg F, stress and creep rupture properties to 1800 deg F, and thermal stability characteristics were evaluated. NASA IIb-7 exhibited the best response to the partial solution heat treatment for optimum properties up to 1200 deg F. The alloy contained 0.13C, 9.0 Cr, 9.0 Co, 2.0 Mo, 7.5 W, 10.0 Ta, 3.5 Al, 0.75 Ti, 0.02 B, 0.10 Zr, 0.50 V, 1.0 Hf, and balance nickel.

Kent, W. B.↗
NASA NTRS1972

High-temperature strength of refractory-metal wires and consideration for composite applications

Tensile and stress-rupture tests were conducted on wires of W-Hf-C, W-Re-Hf-C, ASTAR 811C (a tantalum alloy), and B-88 (a columbium alloy) at room temperature, 1093 C (2000 F), and 1204 C (2200 F). Metallographic examinations were also made of the wire microstructure after testing. Ultimate tensile strength values up to 2170 meganewtons per square meter (314000 psi) at 1093 C (2000 F) and 1940 meganewtons per square meter (281 000 psi) at 1204 C (2200 F) were obtained for W-Re-Hf-C wire. The best strength values obtained for a 100-hour rupture life were, 1410 meganewtons per square meter (205 000 psi) at 1093 C (2000 F) and 910 meganewtons per square meter (132 000 psi) at 1240 C (2200 F) for W-Re-Hf-C wire. The properties obtained suggested that the wires studied showed promise as potential fiber reinforcement in the 1093 to 1204 C (2000 to 2200 F) temperature range.

Petrasek, D. W.↗
NASA NTRS1972

Interactions between creep, fatigue, and strain-aging in two refractory metal alloys.

The application of low-amplitude, high-frequency fatigue vibrations during creep testing of two strain-aging refractory alloys (molybdenum-base TZC and tantalum-base T-111) significantly reduced the creep strength of these materials. This strength reduction caused dramatic increases in both the first-stage creep strain and the second-stage creep rate. The magnitude of the creep rate acceleration varied directly with both frequency and A ratio (ratio of alternating to mean stress), and also varied with temperature, being greatest in the range where the strain-aging phenomenon was most prominent. It was concluded that the creep rate acceleration resulted from a negative strain rate sensitivity which is associated with the strain-aging phenomenon in these materials. (A negative rate sensitivity causes flow stress to decrease with increasing strain rate, instead of increasing as in normal materials.)

Sheffler, K. D.↗
NASA NTRS1972

Adhesion of metals to a clean iron surface studied with LEED and Auger emission spectroscopy.

Discussion of the results of adhesion experiments conducted with various metals contacting a clean iron surface. The metals included gold, silver, nickel, platinum, lead, tantalum, aluminum, and cobalt. Some of the metals were examined with oxygen present on their surface as well as in the clean state. The results indicate that, with the various metals contacting iron, the cohesively weaker will adhere and transfer to the cohesively stronger. The chemical activity of the metal also influenced the adhesive forces measured. With oxygen present on the metal surface, the adhesive forces measured could be correlated with the binding energy of the metal to oxygen.

Buckley, D. H.↗
NASA NTRS1971

Angiographic analysis of heart geometry.

Basic steps in the acquisition and reconstruction of cardiac dimensions obtained from angiocardiograms for spatial reconstruction and analysis are described, and example applications include a reconstruction of the human left ventricle and a study of the motion of the free wall of the right ventricle in a dog. Computer analysis of the spatial motion of implanted tantalum markers is discussed along with corrections for distortion and magnification incurred in the process. Graphics display of three-dimensional ventricle models is examined, and future improvements in angiocardiographic studies are considered.

Sandler, H.↗
NASA NTRS1973

Production of small diameter high-temperature-strength refractory metal wires

Special thermomechanical techniques (schedules) have been developed to produce small diameter wire from three refractory metal alloys: colombian base alloy, tantalum base alloy, and tungsten base alloy. High strengths of these wires indicate their potential for contributing increased strength to metallic composites.

Petrasek, D. W.↗
NASA NTRS1972

High temperature thermocouple development program, part A and part B

The problem of extending the useful life of thermocouples intended for in-core and out-of-core thermionic applications in a vacuum environment at temperatures up to 2273 K for periods of time up to 10,000 hours was investigated. Many factors that may influence this useful life were examined, and a basic probe design was developed. With a few modifications, twenty-three thermocouple assemblies were fabricated. Generally the finished thermocouple consisted of solid doped W-3% Re and W-25% Re wires and high purity and high density BeO insulators, and was sheathed in a high purity tantalum tube. In a few probes, stranded thermocouple wires were substituted; commercial grade BeO was used; and in two cases, CVD W-22% Re tubing was used. Each of the components was made of the highest purity materials available; was subjected to special cleaning steps, and was assembled in a class 10,000 clean room. Pertinent physical and chemical properties were determined on each of the components. Special processing techniques were used in the fabrication of the high purity (99.95%), high density (over 95% of theoretical) BeO.

Toenshoff, D. A.↗
NASA NTRS1973

Testing of uranium nitride fuel in T-111 cladding at 1200 K cladding temperature

Two groups of six fuel pins each were assembled, encapsulated, and irradiated in the Plum Brook Reactor. The fuel pins employed uranium mononitride (UN) in a tantalum alloy clad. The first group of fuel pins was irradiated for 1500 hours to a maximum burnup of 0.7-atom-percent uranium. The second group of fuel pins was irradiated for about 3000 hours to a maximum burnup of 1.0-atom-percent uranium. The average clad surface temperature during irradiation of both groups of fuel pins was approximately 1200 K. The postirradiation examination revealed the following: no clad failures or fuel swelling occurred; less than 1 percent of the fission gases escaped from the fuel; and the clad of the first group of fuel pins experienced clad embrittlement whereas the second group, which had modified assembly and fabrication procedures to minimize contamination, had a ductile clad after irradiation.

Rohal, R. G.↗
NASA NTRS1973

Theoretical analysis of oxygen diffusion at startup in an alkali metal heat pipe with gettered alloy walls

The diffusion of oxygen into, or out of, a gettered alloy exposed to oxygenated alkali liquid metal coolant, a situation arising in some high temperature heat transfer systems, was analyzed. The relation between the diffusion process and the thermochemistry of oxygen in the alloy and in the alkali metal was developed by making several simplifying assumptions. The treatment is therefore theoretical in nature. However, a practical example pertaining to the startup of a heat pipe with walls of T-111, a tantalum alloy, and lithium working fluid illustrates the use of the figures contained in the analysis.

Tower, L. K.↗
NASA NTRS1972

Long life assurance study for manned spacecraft long life hardware. Volume 2: Long life assurance studies of EEE parts and packaging

Guidelines for the design, development, and fabrication of electronic components and circuits for use in spacecraft construction are presented. The subjects discussed involve quality control procedures and test methodology for the following subjects: (1) monolithic integrated circuits, (2) hybrid integrated circuits, (3) transistors, (4) diodes, (5) tantalum capacitors, (6) electromechanical relays, (7) switches and circuit breakers, and (8) electronic packaging.

Source record↗
NASA NTRS1972

Long life assurance study for manned spacecraft long life hardware. Volume 5: Long life assurance test and study recommendations

A study was conducted to establish the guidelines to be applied to the selection of equipment for manned spacecraft systems. Recommendations for expansion of the original study are submitted. The subjects considered are: (1) designing to severe dynamic requirements; (2) analysis of in-space failures due to life limitations; (3) accelerated testing of semiconductors; (4) fan life verification; (5) testing of solid tantalum capacitors; (6) testing of teflon valve seats; and (7) electromigration model verification.

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