Search NASA⌕ Search

SEARCH · Search NASA

Results for “Overcoated Materials”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Space vehicle glow measurements on STS 41-D

A flight experiment using a hand-held, image-intensified spectrographic camera was performed on mission 41-D. The instrument enabled the photographic documentation of the position of the spectral slit on the image to be subjected to spectrographic analysis. Because of this instrument feature, the spectrum of the glow on the Shuttle tail pod could be clearly separated from spectrum of the scattered light from the Orbiter. From the measurements it is clear that the spectrum of the glow is a continuum in the passband of the instrument between 4200 A and 8000 A. The measured spectral resolution of the instrument was 35 A. The scattered light from the Orbiter surfaces distinctly show the components of the earth's airglow at 5577 A and 7620 A. On the same flight material samples were also carried by the Orbiter attached to the Remote Manipulating System arm. These samples were representative of the material overcoatings used on the space telescope. The altitude of the 41-D flight was 290 km, instead of the 220 km which was originally planned for this experiment. The signal to noise ratio in the material glow discrimination experiment was quite low. This made it difficult to draw strong conclusions regarding the glow propensity of the materials. Nevertheless it was clear that polyethylene produces a very weak glow, while most black overcoating materials produce significant glow. MgF2 was also found to produce a relatively intense glow.

Mende, S. B.↗
NASA NTRS1992

Oxidation processes in magneto-optic and related materials

The surface oxidation processes of thin films of magneto-optic materials, such as the rare-earth transition metal alloys have been studied, starting in ultrahigh vacuum environments, using surface analysis techniques, as a way of modeling the oxidation processes which occur at the base of a defect in an overcoated material, at the instant of exposure to ambient environments. Materials examined have included FeTbCo alloys, as well as those same materials with low percentages of added elements, such a Ta, and their reactivities to both O2 and H2O compared with materials such as thin Fe films coated with ultrathin adlayers of Ti. The surface oxidation pathways for these materials is reviewed, and XPS data presented which indicates the type of oxides formed, and a critical region of Ta concentration which provides optimum protection.

Lee, Paul A.↗
NASA NTRS1994

Oxidation of Palladium-Chromium Alloys for High Temperature Applications

An alloy consisting of Pd with 13 wt % Cr is a promising material for high temperature applications. High temperature performance is degraded by the oxidation of the material, which is more severe in the fine wires and thin films used for sensor applications than in the bulk. The present study was undertaken to improve our understanding of the physical and chemical changes occurring at these temperatures and to identify approaches to limit oxidation of the alloy. The alloy was studied in both ribbon and wire forms. Ribbon samples were chosen to examine the role of grain boundaries in the oxidation process because of the convenience of handling for the oxidation studies. Wire samples 25 microns in diameter which are used in resistance strain gages were studied to correlate chemical properties with observed electrical, physical, and structural properties. Overcoating the material with a metallic Cr film did prevent the segregation of Pd to the surface; however, it did not eliminate the oxidation of the alloy.

Piltch, Nancy D.↗
NASA NTRS1981

Compact infrared detector

Broadband IR detector integrated into compact package for pollution monitoring and weather prediction is small, highly responsive, and immune to high noise. Sensing material is transparent sheet metalized with reflecting coating and overcoated with black material on same side. Pulse produced by chopping of infrared source beam creates transient "thermal lens" that temporarily defocuses laser beam probe. Detector monitoring beam measures defocusing which parallels infrared intensity.

Gupta, A.↗
NASA NTRS1977

Application of diffusion barriers to high modulus fibers

Barrier layers were coated onto high-modulus fibers, and nickel and titanium layers were overcoated as simulated matrix materials. The objective was to coat the high-strength fibers with unreactive selected materials without degrading the fibers. The fibers were tungsten, niobium, and single-crystal sapphire, while the materials used as barrier coating layers were Al2O3, Y2O3, TiC, ZrC, WC with 14% Co, and HfO2. An ion-plating technique was used to coat the fibers. The fibers were subjected to high-temperature heat treatments to evaluate the effectiveness of the barrier layer in preventing fiber-metal interactions. Results indicate that Al2O3, Y2O3, and HfO2 can be used as barrier layers to minimize the nickel-tungsten interaction. Further investigation, including thermal cycling tests at 1090 C, revealed that HfO2 is probably the best of the three.

Veltri, R. D.↗
NASA NTRS1982

Retractor Tool for Brain Surgery

Proposed brain-surgery tool has an octogonal fixture for positioning latex tube over incision. Eight stainless-steel wires embedded in latex extend to hold positioning fixture. Another eight are also embedded in the latex. Concentric sleeves are successively inserted into expandable latex tube. The first sleeve is placed over a solid rod. Last sleeve is a stainless-steel tube 1 inch in diameter. It is overcoated with Teflon (or equivalent) material.

Helms, R.↗
NASA NTRS1984

Interaction of atomic oxygen with solid surfaces at orbital altitudes (A0114)

The basic approach to this experiment is to expose a wide variety of material surfaces to the atomic flux in orbit. The experiment is passive and depends on preflight and postflight measurements of the test surfaces in the laboratory. The experiment will also include a reflectometer device to measure atomic beam reflection angles and thus momentum accommodations, and a unique passive spacecraft attitude sensor. Samples consisting of solid disks or thin film coatings on substrate disks will be mounted in a panel. The face of this panel will be flown on Long Duration Exposure Facility normal to the incident stream of oxygen atoms. Each disk will have part of its front surface masked so exposure to the atomic-oxygen reaction will be limited to selected areas, the shadowed areas being used as control surfaces in the measurements. A typical sample is an optically flat quartz disk overcoated with a film of the material of interest. These include Ag, Au, Pt, Nb, Ni, Al, C, Si, Ge, LiF, and a few engineering materials. Some materials for which the expected removal rate is high, such as carbon, will be solid disks rather than thin films.

Gregory, J. C.↗
NASA NTRS2014

Venus Landsailer Zephyr

Imagine sailing across the hot plains of Venus! A design for a craft to do just this was completed by the COncurrent Multidisciplinary Preliminary Assessment of Space Systems (COMPASS) Team for the NASA Innovative Advanced Concepts (NIAC) project. The robotic craft could explore over 30 kilometers of the surface of Venus, driven by the power of the wind. The Zephyr Venus Landsailer is a science mission concept for exploring the surface of Venus with a mobility and science capability roughly comparable to the Mars Exploration Rovers (MER) mission, but using the winds of the thick atmosphere of Venus for propulsion. It would explore the plains of Venus in the year 2025, near the Venera 10 landing site, where wind velocities in the range of 80 to 120 centimeters per second (cm/s) were measured by earlier Soviet landing missions. These winds are harnessed by a large wing/sail which would also carry the solar cells to generate power. At around 250 kilograms (kg), Zephyr would carry an 8 meter tall airfoil sail (12 square meters area), 25 kg of science equipment (mineralogy, grinder, and weather instruments) and return 2 gigabytes of science over a 30 day mission. Due to the extreme temperatures (450 degrees Centigrade) and pressures (90 bar) on Venus, Zephyr would have only basic control systems (based on high temperature silicon carbide (SiC)electronics) and actuators. Control would come from an orbiter which is in turn controlled from Earth. Due to the time delay from the Earth a robust control system would need to exist on the orbiter to keep Zephyr on course. Data return and control would be made using a 250 megahertz link with the orbiter with a maximum data rate of 2 kilobits per second. At the minimal wind speed required for mobility of 35 cm/s, the vehicle move at a slow but steady 4 cm/s by positioning the airfoil and use of one wheel that is steered for pointing control. Navigation commands from the orbiter will be based upon navigation cameras, simple accelerometers and stability sensors; Zephyr's stability is robust, using a wide wheel base along with controls to "feather" or "luff" the airfoil and apply brakes to stop the vehicle in the case of unexpected conditions. This would be the science gathering configuration. The vehicle itself would need to be made from titanium (Ti) as the structural material, with a corrosion-barrier overcoating due to extreme temperatures on the surface.

Wind Sailing↗
NASA NTRS1975

Combined environmental effects on polymers

A series of space simulation tests on FEP Teflon and other polymeric thermal control coatings was conducted using UV, electrons, protons and Lyman-alpha wavelength vacuum UV radiation. Interest was centered on simulating synchronous altitude radiation environment conditions. Physical changes in materials included loss of specularity and introduction of a high density of photographable tracking defects on a microscopic scale. An example shows the discharge of trapped electrons when dielectric strength is exceeded. This leaves a portion of the Teflon volume no longer clear, but diffusely transmitting and reflecting. Thermophysical changes included degradation of solar absorptance coefficients as much as five-fold. The situation that prevails for earth orbit contrasted with polymer performance in the solar wind. It is suggested that conductive overcoatings be developed for polymers and other flexible materials, comparable or superior to those available for fused silica SSMs.

Fogdall, L. B.↗
NASA NTRS1995

Durability of reflector materials in the space environment

Various reflector configurations were flown as part of the Long Duration Exposure Facility (LDEF) A0171 experiment. These reflectors consisted of nickel substrates with aluminum, enhanced aluminum (multiple layers of aluminum and silver), silver, and silver alloy coatings with glassy ceramic overcoatings. These samples have been evaluated for changes in reflectance due to 5.8 years in the space environment. The reflector materials have also been evaluated using angstrometer, Rutherford backscattering (RBS), and electron spectroscopy for chemical analysis (ESCA) techniques.

Whitaker, Ann F.↗
NASA NTRS1986

Effects on optical systems from interactions with oxygen atoms in low earth orbits

Modifications of material surface properties due to interactions with ambient atomic oxygen have been observed on surfaces facing the orbital direction in low earth orbits. Some effects are very damaging to surface optical properties while some are more subtle and even beneficial. Most combustible materials are heavily etched, and some coatings, such as silver and osmium, are seriously degraded or removed as volatile oxides. The growth of oxide films on metals and semiconductors considered stable in dry air was measured. Material removal, surface roughness, reflectance, and optical densities are reported. Effects of temperature, contamination, and overcoatings are noted.

Peters, P. N.↗
NASA NTRS1988

Amorphous silicon carbide coatings for extreme ultraviolet optics

Amorphous silicon carbide films formed by sputtering techniques are shown to have high reflectance in the extreme ultraviolet spectral region. X-ray scattering verifies that the atomic arrangements in these films are amorphous, while Auger electron spectroscopy and Rutherford backscattering spectroscopy show that the films have composition close to stoichiometric SiC, although slightly C-rich, with low impurity levels. Reflectance vs incidence angle measurements from 24 to 1216 A were used to derive optical constants of this material, which are presented here. Additionally, the measured extreme ultraviolet efficiency of a diffraction grating overcoated with sputtered amorphous silicon carbide is presented, demonstrating the feasibility of using these films as coatings for EUV optics.

Kortright, J. B.↗
NASA NTRS2024

Optimization of Mission Enabling Broadband Lyman Ultraviolet Series to Infrared Aluminum Lithium Fluoride Reflectors

The Habitable Worlds Observatory (HWO) concept NASA flagship mission aims extend the ultraviolet (UV) observation range and sensitivity capabilities of the Hubble Space Telescope (HST) with respective goals of reaching photons down to 100 nm and containing an ultraviolet multi-object spectrograph with sensitivity improved 30-100 times. Adding the sensitivity capabilities near the Lyman series spectral range of ~100-121.6 nm reduces the reliance of redshift for key diagnostic ion lines such as O VI (103.2 nm), and heavily ionized gases of Ne VIII (77.5 nm) and MgX (62.5 nm). Clean and unoxidized aluminum (Al) reflectors provide optimal efficiency over a broadband down to the extreme ultraviolet (EUV) wavelength of ~83 nm. To prevent oxidation and maintain high spectral efficiency down to ~100 nm, the Al reflector is conventionally overcoated with a thin lithium fluoride (LiF) layer. We investigate the optimization of the deposition of the Al+LiF coating material composition to attain high spectral efficiency broadband reflectors down to 100 nm and enable the scientific goals of HWO. Lithium hexafluoroaluminate (Li3AlF6) is investigated as a different composition form of LiF to overcoat Al. The spectral efficiency and durability of the reflectors is evaluated. We will demonstrate the use of Li3AlF6 as an overcoat to protect aluminum yields ultra-high efficiency at the Hydrogen Lyman-alpha (HLyα, 121.6 nm) line with experimental reflectance values peaking up to 99%.

optical coatings↗
NASA NTRS2024

Optimization of Mission Enabling Broadband Lyman Ultraviolet Series to Infrared Aluminum Lithium Fluoride Reflectors

The Habitable Worlds Observatory (HWO) concept NASA flagship mission aims extend the ultraviolet (UV) observation range and sensitivity capabilities of the Hubble Space Telescope (HST) with respective goals of reaching photons down to 100 nm and containing an ultraviolet multi-object spectrograph with sensitivity improved 30-100 times. Adding the sensitivity capabilities near the Lyman series spectral range of ~100-121.6 nm reduces the reliance of redshift for key diagnostic ion lines such as O VI (103.2 nm), and heavily ionized gases of Ne VIII (77.5 nm) and MgX (62.5 nm). Clean and unoxidized aluminum (Al) reflectors provide optimal efficiency over a broadband down to the extreme ultraviolet (EUV) wavelength of ~83 nm. To prevent oxidation and maintain high spectral efficiency down to ~100 nm, the Al reflector is conventionally overcoated with a thin lithium fluoride (LiF) layer. We investigate the optimization of the deposition of the Al+LiF coating material composition to attain high spectral efficiency broadband reflectors down to 100 nm and enable the scientific goals of HWO. Lithium hexafluoroaluminate (Li3AlF6) is investigated as a different composition form of LiF to overcoat Al. The spectral efficiency and durability of the reflectors is evaluated. We will demonstrate the use of Li3AlF6 as an overcoat to protect aluminum yields ultra-high efficiency at the Hydrogen Lyman-alpha (HLyα, 121.6 nm) line with experimental reflectance values peaking up to 99%.

optical coatings↗
NASA NTRS1971

The effect of rocket plume contamination on the optical properties of transmitting and reflecting materials

The preliminary results of plume contamination from a 5-pound thrust single-doublet, bipropellant rocket engine on the transmittance of quartz and the reflectance of a silicon monoxide overcoated aluminum mirror are presented. Changes in quartz transmittance were found to be significant and were due to both absorption and scattering effects. Contaminant absorption effects were predominant at the short wavelengths and scattering effects were greatest in the visible wavelengths. Measured changes in mirror reflectance were due primarily to contaminant absorption. Scattering effects were found to be as much as 9 percent of the total reflected energy from the mirror. There were no noticeable chemical or erosion effects on either the quartz or the front surface mirror.

Jack, J. R.↗
NASA NTRS1972

The effect of rocket plume contamination on the optical properties of transmitting and reflecting materials.

The preliminary results of plume contamination from a 5-pound thrust single-doublet, bipropellant rocket engine on the transmittance of quartz and the reflectance of a silicon monoxide overcoated aluminum mirror have been presented. Changes in quartz transmittance were found to be significant and were due to both absorption and scattering effects. Contaminant absorption effects were predominant at the short wavelengths and scattering effects were greatest in the visible wavelengths. Measured changes in mirror reflectance were due primarily to contaminant absorption. Scattering effects were found to be as much as 9% of the total reflected energy from the mirror. There were no noticeable chemical or erosion effects on either the quartz or the front surface mirror.

Jack, J. R.↗