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At least 73 records · Page 4

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NASA NTRS1972

Corrosion study of bare and coated stainless steel

A program was conducted at Kennedy Space Center from February 1968 to February 1971 to evaluate the performance of austenitic stainless steel alloys used in fluid systems lines. For several years, there had been numerous failures of stainless steel hardware caused by pitting and stress corrosion cracking. Several alloys were evaluated for effectiveness of certain sacrificial-type protective coverings in preventing corrosion failures. Samples were tested in specially designed racks placed 91 meters (100 yards) above high-tide line at Cape Kennedy. It is concluded that: (1) unprotected tubing samples showed evidence of pitting initiation after 2 weeks; (2) although some alloys develop larger pits than others, it is probable that the actual pitting rate is independent of alloy type; (3) the deepest pitting occurred in the sheltered part of the samples; and (4) zinc-rich coatings and an aluminum-filled coating have afforded sacrificial protection against pitting for at least 28 months. It is believed that a much longer effective coating life can be expected.

Morrison, J. D.↗

NASA NTRS1975

Monotectic and syntectic alloys: ASTP experiment MA-044

A postflight preliminary technical evaluation is presented of the returned samples of aluminum antimonide (AlSb) syntectic compound and lead-zinc (PbZn) monotectic immiscible processed during the Apollo-Soyuz Test Project (ASTP) mission. The returned cartridges, extracted ampoules, and removed samples were examined in detail. A genesis of the experiment is given along with a summary of the efforts and various scheduled tests up to the ASTP mission. A tentative characterization plan is developed from the postflight preliminary examination which makes use of the limited number of available samples and is based on the initial observations. It is indicated that a higher degree of compositional homogeneity in aluminum antimonide was achieved under flight test conditions.

Ang, C. Y.↗

NASA NTRS1980

Ohmic contact for P type indium phosphide

A body including P type indium phosphide has an ohmic contact thereon of an alloy of by weight 81% to 86% gold (Au), 11% to 14% germanium (Ge) and 2% to 5% zinc (Zn). This contact has a low resistance and good adhesion to the indium phosphide body.

Hawrylo, Frank Z.↗

NASA NTRS2003

Aluminum Alloy and Article Cast Therefrom

A cast article from an aluminum alloy, which has improved mechanical properties at elevated temperatures, has the following composition in weight percent: Silicon 14 - 25.0, Copper 5.5 - 8.0, Iron 0.05 - 1.2, Magnesium 0.5 - 1.5, Nickel 0.05 - 0.9, Manganese 0.05 - 1.0, Titanium 0.05 - 1.2, Zirconium 0.05 - 1.2, Vanadium 0.05 - 1.2, Zinc 0.05 - 0.9, Phosphorus 0.001 - 0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10 - 25, and the copper-to-magnesium ratio is 4 - 15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a LI2, crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix and containing up to about 60% by volume of a secondary filler material.

Lee, Jonathan A.↗

NASA NTRS2005

High Strength Aluminum Alloy For High Temperature Applications

A cast article from an aluminum alloy has improved mechanical properties at elevated temperatures. The cast article has the following composition in weight percent: Silicon 6.0-25.0, Copper 5.0-8.0, Iron 0.05-1.2, Magnesium 0.5-1.5, Nickel 0.05-0.9, Manganese 0.05-1.2, Titanium 0.05-1.2, Zirconium 0.05-1.2, Vanadium 0.05-1.2, Zinc 0.05-0.9, Strontium 0.001-0.1, Phosphorus 0.001-0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10-25, and the copper-to-magnesium ratio is 4-15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a LI2 crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix containing up to about 60% by volume of a secondary filler material.

Jonathan A Lee↗

NASA NTRS1995

Ignition and combustion of bulk metals under elevated, normal and reduced gravity conditions

This research effort is aimed at providing further insight into this multi-variable dependent phenomena by looking at the effects of gravity on the ignition and combustion behavior of metals. Since spacecraft are subjected to higher-than-1g gravity loads during launch and reentry and to zero-gravity environments while in orbit, the study of ignition and combustion of bulk metals at different gravitational potentials is of great practical concern. From the scientific standpoint, studies conducted under microgravity conditions provide simplified boundary conditions since buoyancy is removed, and make possible the identification of fundamental ignition mechanisms. The effect of microgravity on the combustion of bulk metals has been investigated by Steinberg, et al. on a drop tower simulator. However, no detailed quantitative work has been done on ignition phenomena of bulk metals at lower or higher-than-normal gravitational fields or on the combustion characteristics of metals at elevated gravity. The primary objective of this investigation is the development of an experimental system capable of providing fundamental physical and chemical information on the ignition of bulk metals under different gravity levels. The metals used in the study, iron (Fe), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), and copper (Cu) were selected because of their importance as elements of structural metals and their simple chemical composition (pure metals instead of multi-component alloys to avoid complication in morphology and spectroscopic studies). These samples were also chosen to study the two different combustion modes experienced by metals: heterogeneous or surface oxidation, and homogeneous or gas-phase reaction. The experimental approach provides surface temperature profiles, spectroscopic measurements, surface morphology, x-ray spectrometry of metals specimens and their combustion products, and high-speed cinematography of the heating, ignition and combustion stages of the metal specimen. This paper summarizes the results obtained to date from experiments conducted under normal and high-gravity conditions.

Abbud-Madrid, Angel↗

NASA NTRS1978

The 1.1 micrometer and visible emission semiconductor diode lasers

In (AlGa)As, the first of three alloy systems studied, Continuous Wave (CW) operation was obtained at room temperature at a wavelength as low as 7260 A. Reliability in this system was studied in the incoherent mode. Zinc doped devices had significant degradation, whereas Ge or Ge plus Zi doped devices had none. The Al2O3 facet coatings were shown to significantly reduce facet deterioration in all types of lasers, longer wavelength units of that type having accumulated (at the time of writing) 22,000 hours with little if any degradation. A CL study of thin (AlGa)As layers revealed micro fluctuation in composition. A macro-scale fluctuation was observed by electroreflectance. An experimental and theoretical study of the effect of stripe width on the threshold current was carried out. Emission below 7000 A was obtained in VPE grown Ga(AsP) (In,Ga)P with CW operation at 10 C. Lasers and LED's were made by LPE in (InGa) (AsP). Laser thresholds of 5 kA/cm2 were obtained, while LED efficiences were on the order of 2%. Incoherent life test over 6000 hours showed no degradation.

Ladany, I.↗

NASA NTRS1991

Interface demarcation in Bridgman-Stockbarger crystal growth of II-VI compounds

In preparation for anticipated microgravity space missions carrying the Advanced Automated Directional Solidification Furnace, experiments were conducted to determine growth of interface in growing crystals of cadmium-doped germanium (test case), cadmium telluride, and mercury zinc telluride, using three different techniques. It was found that compositional variations detectable by microprobe and EDS techniques were most successful for detecting interfaces in materials with extensive transient regions, large segregation coefficients, and high alloy content.

Gillies, Donald C.↗

NASA NTRS2014

Micrometeoroid Impacts on the Hubble Space Telescope Wide Field and Planetary Camera 2: Larger Particles

The Wide Field and Planetary Camera 2 (WFPC2) was returned from the Hubble Space Telescope (HST) by shuttle mission STS-125 in 2009. In space for 16 years, the surface accumulated hundreds of impact features on the zinc orthotitanate paint, some penetrating through into underlying metal. Larger impacts were seen in photographs taken from within the shuttle orbiter during service missions, with spallation of paint in areas reaching 1.6 cm across, exposing alloy beneath. Here we describe larger impact shapes, the analysis of impactor composition, and the micrometeoroid (MM) types responsible.

Kearsley, A. T.↗

NASA NTRS1977

Monotectic and syntectic alloys. Experiment MA-044

The flight test furnace run of the monotectic and syntectic alloys experiment was successfully performed during the Apollo-Soyuz Test Project mission in July 1975. Examination of the returned sample cartridges and the formal comparative characterization of the low-g and one-g processed samples of lead-zinc and aluminum antimonide were completed. The results for aluminum antimonide show that polycrystalline and multiphased material can be homogenize in space under low-g conditions. Microstructural study on the lead-zinc flight samples shows that complete interdiffusion of lead and zinc had not been achieved, even though the flight data indicated a soak temperature in the miscible region that was 40 K above the published consolute temperature.

Lacy, L. L.↗

NASA NTRS1977

Thermionic converter studies at Thermo Electron

The Thermionic Energy Converter (TEC) development program includes theoretical and experimental surface studies, diode evaluation, enhanced mode converter investigations and system studies, as well as materials fabrication and testing. The primary effort has been concentrated on increasing converter performance via improved electrodes. Diodes with oxide collectors (i.e., tungsten oxide, titanium oxide, zinc oxide and barium oxide) have provided the best performance. Emitters requiring reduced cesium pressure (such as oxygenated tungsten, lanthanum hexaboride, platinum and graphite) are being tested. Converter configurations using particle spacing are under investigation. Experiments with auxiliary electrode thermionic converters are in progress. Both silicon carbide and alloy hot shells (i.e., barriers to isolate the converter from the combustion environment) have been fabricated and tested.

Huffman, F. N.↗

NASA NTRS1993

High energy density aluminum-oxygen cell

An alternative to a secondary battery as the power source for vehicle propulsion is a fuel cell. An example of this is the metal-air fuel cell using metals such as aluminum, zinc, or iron. Aluminum is a particularly attractive candidate, having high energy and power densities, being environmentally acceptable, and having a large, established industrial base for production and distribution. An aluminum-oxygen system is currently under development for a UUV test vehicle, and recent work has focussed upon low corrosion aluminum alloys and an electrolyte management system for processing the by-products of the energy-producing reactions. This paper summarizes the progress made in both areas. Anode materials capable of providing high utilization factors over current densities ranging from S to 150 mA/sq cm have been identified. These materials are essential to realizing an acceptable mission life for the UUV. With respect to the electrolyte management system, a filter/precipitator unit has been successfully operated for over 250 hours in a large scale, half-cell system.

Rudd, E. J.↗

NASA NTRS1998

Cathodic Protection Deployment on Space Shuttle Solid Rocket Boosters

Corrosion protection of the space shuttle solid rocket boosters incorporates the use of cathodic protection(anodes) in concert with several coatings systems. The SRB design has large carbon/carbon composites(motor nozzle) electrically connected to an aluminum alloy structure. Early in the STS program, the aluminum structures incurred tremendous corrosive attack due primarily to the galvanic couple to the carbon/carbon nozzle at coating damage locations. Also contributing to the galvanic corrosion problem were stainless steel and titanium alloy components housed within the aluminum structures and electrically connected to the aluminum structures. This paper will highlight the evolution in the protection of the aluminum structures, providing historical information and summary data from the operation of the corrosion protection systems. Also, data and information will be included regarding the evaluation and deployment of inorganic zinc rich primers as anode area on the aluminum structures.

Zook, Lee M.↗

NASA NTRS1986

Reactively-sputtered zinc semiconductor films of high conductivity for heterojunction devices

A high conductivity, n-doped semiconductor film is produced from zinc, or Zn and Cd, and group VI elements selected from Se, S and Te in a reactive magnetron sputtering system having a chamber with one or two targets, a substrate holder, means for heating the substrate holder, and an electric field for ionizing gases in the chamber. Zinc or a compound of Zn and Cd is placed in the position of one of the two targets and doping material in the position of the other of the two targets. Zn and Cd may be placed in separate targets while a dopant is placed in the third target. Another possibility is to place an alloy of Zn and dopant, or Zn, Cd and dopant in one target, thus using only one target. A flow of the inert gas is ionized and directed toward said targets, while a flow of a reactant gas consisting of hydrides of the group VI elements is directed toward a substrate on the holder. The targets are biased to attract negatively ionized inert gas. The desired stochiometry for high conductivity is achieved by controlling the temperature of the substrate, and partial pressures of the gases, and the target power and total pressure of the gases in the chamber.

Stirn, Richard J.↗

NASA NTRS1978

Life test results for an ensemble of CO2 lasers

The effects of cathode material, cathode operating temperature, anode configuration, window materials, and hydrogen additives on laser lifetime are determined. Internally oxidized copper and silber-copper alloy cathodes were tested. The cathode operating temperature was raised in some tubes through the use of thermal insulation. Lasers incorporating thermally insulated silver copper oxide cathodes clearly yielded the longest lifetimes-typically in excess of 22,000 hours. The use of platinum sheet versus platinum pin anodes had no observable effect on laser lifetime. Similarly, the choice of germanium, cadmium telluride, or zinc selenide as the optical window material appears to have no impact on lifetime.

Peruso, C. J.↗

NASA NTRS2016

Integrated Multi-Color Light Emitting Device Made with Hybrid Crystal Structure

An integrated hybrid crystal Light Emitting Diode ("LED") display device that may emit red, green, and blue colors on a single wafer. The various embodiments may provide double-sided hetero crystal growth with hexagonal wurtzite III-Nitride compound semiconductor on one side of (0001) c-plane sapphire media and cubic zinc-blended III-V or II-VI compound semiconductor on the opposite side of c-plane sapphire media. The c-plane sapphire media may be a bulk single crystalline c-plane sapphire wafer, a thin free standing c-plane sapphire layer, or crack-and-bonded c-plane sapphire layer on any substrate. The bandgap energies and lattice constants of the compound semiconductor alloys may be changed by mixing different amounts of ingredients of the same group into the compound semiconductor. The bandgap energy and lattice constant may be engineered by changing the alloy composition within the cubic group IV, group III-V, and group II-VI semiconductors and within the hexagonal III-Nitrides.

Park, Yeonjoon↗

NASA NTRS2017

Integrated Multi-Color Light Emitting Device Made with Hybrid Crystal Structure

Park, Yeonjoon↗

NASA NTRS2020

Transmutations Observed from Pressure Cycling Palladium Silver Metals with Deuterium Gas

Hydrogen, deuterium, and helium gases were separately cycled through a Johnson-Mattheypurifier containing coiled palladium silver alloy tubing: Pd25Ag (75 wt% Pd and 25 wt% Ag).During the cycling of D2 gas, evidence of anomalous heat production was observed. However,during the cycling of H2 and He,very little (H2) or no (He) unusual heat events were observed.After cycling the D2 gas through the coiled tubing for several months, Pd25Ag samples showedan increase in Cu and Fe compared with the amounts in unexposed Pd25Ag. Chromium,manganese, and zinc were detected in gas-cycled Pd25Ag samples, whereas they were notdetected in unexposed Pd25Ag samples. In particular, Zn was present in the gas-cycled Pd25Agmaterial in larger quantities than either Cr or Mn. Although a small amount of Cu was present inthe Pd25Ag coil before the D2 gas cycling, 7 times more was present after the cycling. Multiplematerial characterization techniques were used to obtain both pre-test and post-test elementalcomposition. The results indicate that novel post-test elements, primarily on the surface, werecreated by unknown nuclear mechanisms at low energy.

Gustave C Fralick↗