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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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Inexpensive process converts architectural reflective-coated glass into electrically heated panels. Technique utilizes reflective layer as heating element in ordinary glass. Panels have many applications, including automobile windows, home-heating panels, temperature-controlled windows or containers, and food warming trays.
The mechanical properties of FP-Al2O3 fiber reinforced composites prepared by liquid infiltration techniques are improved. A strengthening addition, magnesium, was incorporated with the aluminum-lithium matrix alloy usually selected for these composites because of its good wetting characteristics. This ternary composite, FP-Al2O3/Al-(2-3)Li-(3-5)Mg, showed improved transverse strength compared with FP-Al2O3/Al-(2-3)Li composites. The lower axial strengths found for the FP-Al2O3/Al-(2-3)Li-(3-5)Mg composites were attributed to fabrication related defects. Another technique was the use of Ti/B coated FP-Al2O3 fibers in the composites. This coating is readily wet by molten aluminum and permitted the use of more conventional aluminum alloys in the composites. However, the anticipated improvements in the axial and transverse strengths were not obtained due to poor bonding between the fiber coating and the matrix. A third approach studied to improve the strengths of FP-Al2O3 reinforced composites was the use of magnesium alloys as matrix materials. While these alloys wet fibers satisfactorily, the result indicated that the magnesium alloy composites used offered no axial strength or modulus advantage over FP-Al2O3/Al-(2-3)Li composites.
A passive hydrogen maser employing a smaller microwave cavity than previous masers is described. The volume of the entire resonator package, including a conventional source, hexapole state selector, and four magnetic shields, is estimated at 20 liters. The techniques for constructing the ceramic cavity, coating it with FEP, and attaching the endcaps to achieve a stable container (to allow its use as a single vacuum system) are described in detail. Frequency stability measurements were made of four such masers, against an NBS-4 cesium primary standard, against each other, and against eight commercial cesium clocks; frequency stability level is reported as 1.7 x 10 to the -12th tau exp -1/2 from 1 to 100,000 sec, and no drift above 1 x 10 to the -15th/day was found. Pressure and temperature effects on frequency stability were found at the 1 x 10 to the -14th level. Noise behavior beyond 200,000 sec is characterized as random walk. The potential use of a compact stable maser as a clock is suggested.
Use of infrared thermography proposed for inspection of some kinds of coatings. Sample heated radiantly from behind viewed by infrared thermography. Defects in coating visible at infrared wavelengths. Inspection technique executed by remote scanning or robotic scanning with automatic electronic detection of anomalies.
A small CO2 snow cleaning apparatus to clean both molecular films and particles from small and large components and surfaces was constructed. Various types of surfaces were cleaned using the CO2 technique. Vacuum deposited and sputtered metallic coatings such as germanium, aluminum, and silver and silicon wafers, and polished copper conical mirrors were purposely contaminated with everyday aerospace contaminants, including particle fallout and fingerprints. Precleaning characterization by Bidirectional Reflectance Distribution Function (BRDF), ellipsometry, nonvolatile residue, and microscopic particle evaluation served as evaluation of cleaning efficiency. Good results were obtained in trial application.
The development of techniques for the fabrication of multilayer coated mirrors which can function as energy selective X-ray and XUV mirrors at normal incidence has greatly expanded the options available to the astronomical spectroscopist. A rocket spectroheliograph which utilizes multilayer optics in three configurations has been developed. These are: (1) as Cassegrain telescopes for imaging at 256 A (He II) and 173 A (Fe IX, X); (2) as tertiary mirrors used with a conventional Wolter I telescope for imaging at 44 A (Si XI, XII), 173 A, and 256 A; and (3) as off-axis spherical mirrors for imaging at 44 A and 256 A. The paper reports on laboratory images and performance measurements obtained with these optical systems, and briefly on Solar Observations.
Hard, amorphous hydrogenated carbon films of diamondlike quality deposited at room temperature on silicon, optical glass, and quartz through decomposition of CH4 in electron-cyclotron-resonance (ECR) microwave plasma of CH4 diluted with H2. Technique provides hard, abrasion-resistant coatings for lenses and other optical components. Films chemically inert and posses high electrical resistivity and breakdown fields, valuable properties in microelectronics applications.
Recent needs in the non-aerospace industrial sector have revitalized interest in high performance alloys. TAZ-8A has a combination of properties that makes it unique: a high temperature strength, oxidation resistance, abrasion resistance, and exceptional thermal shock resistance. The major drawback for the utilization of this alloy is the relatively high cost compared with the more common iron base alloys. Reduced material consumption and lower costs are possible by using coatings of TAZ-8A on a low cost substrate. Coatings were applied using plasma spray techniques developed by NASA as well as modified plasma vapor deposition (PVD) techniques.
During this research period, we have effectively transferred existing computer codes from CRAY supercomputer to work station based systems. The work station based version of our code preserved the accuracy of the numerical computations while giving a much better turn-around time than the CRAY supercomputer. Such a task relieved us of the heavy dependence of the supercomputer account budget and made codes developed in this research project more feasible for applications. The analysis of pyramidal horns with impedance surfaces was our major focus during this research period. Three different modeling algorithms in analyzing lossy impedance surfaces were investigated and compared with measured data. Through this investigation, we discovered that a hybrid Fourier transform technique, which uses the eigen mode in the stepped waveguide section and the Fourier transformed field distributions across the stepped discontinuities for lossy impedances coating, gives a better accuracy in analyzing lossy coatings. After a further refinement of the present technique, we will perform an accurate radiation pattern synthesis in the coming reporting period.
CdTe crystals were grown by horizontal seeded physical vapor transport technique in uncoated and boron nitride coated fused silica ampoules with the source materials near the congruent sublimation condition. The grown crystals were characterized by current-voltage measurements, low temperature photoluminescence spectroscopy, near IR transmission optical microscopy, spark source mass spectroscopy and chemical etching. The measured resistivities of the crystals were in the high-10(exp 8) ohm-cm range. Although the crystal grown in the boron nitride coating was contaminated with boron from the photoluminescence measurements, the coating yielded a single crystal with no inclusions or precipitates.
Historically, thermopile detectors, generators, and refrigerators based on bulk materials have been used to measure temperature, generate power for spacecraft, and cool sensors for scientific investigations. New potential uses of small, low-power, thin film thermopiles are in the area of microelectromechanical systems since power requirements decrease as electrical and mechanical machines shrink in size. In this research activity, thin film thermopile devices are fabricated utilizing radio frequency sputter coating and photoresist lift-off techniques. Electrical characterizations are performed on two designs in order to investigate the feasibility of generating small amounts of power, utilizing any available waste heat as the energy source.
Thermally sprayed coatings are being studied and developed as methods of enabling lightweight composites to be used more extensively as structural components in propulsion applications in order to reduce costs and improve efficiency through weight reductions. The primary goal of this work is the development of functionally graded material [FGM] polymer/metal matrix composite coatings to provide improved erosion/oxidation resistance to polyimide-based polymer matrix composite [PMC] substrates. The goal is to grade the coating composition from pure polyimide, similar to the PMC substrate matrix on one side, to 100 % WC-Co on the other. Both step-wise and continuous gradation of the loading of the WC-Co reinforcing phase are being investigated. Details of the coating parameter development will be presented, specifically the high velocity oxy-fuel [HVOF] combustion spraying of pure PMR-11 matrix material and layers of various composition PMR-II/WC-Co blends onto steel and PMR-15 composite substrates. Results of the HVOF process optimization, microstructural characterization, and analysis will be presented. The sprayed coatings were evaluated using standard metallographic techniques - optical and scanning electron microscopy [SEM]. An SEM + electron dispersive spectroscopy [EDS] technique has also been used to confirm retention of the PMR-II component. Results of peel/butt adhesion testing to determine adhesion will also be presented.
There is a well-established need for high-resolution radionuclide imaging techniques that provide non-invasive measurement of physiological function in small animals. We, therefore, have begun developing a small animal radionuclide imaging system using grazing incidence mirrors to focus low-energy gamma-rays emitted by I-125, and other radionuclides. Our initial prototype optic, fabricated from thermally-formed glass, demonstrated a resolution of 1500 microns, consistent with the performance predicted by detailed simulations. More recently, we have begun constructing mirrors using a replication technique that reduces low spatial frequency errors in the mirror surface, greatly improving the resolution. Each technique offers particular advantages: e.g., multilayer coatings are easily deposited on glass, while superior resolution is possible with replicated optics. Scaling the results from our prototype optics, which only have a few nested shells, to system where the lens has a full complement of several tens of nested shells, a sensitivity of approx. 1 cps/micro Ci is possible, with the exact number dependent on system magnification and radionuclide species. (Higher levels of efficiency can be obtained with multi-optic imaging systems.) The gamma-ray lens will achieve a resolution as good as 100 microns, independent of the final sensitivity. The combination of high spatial resolution and modest sensitivity will enable in vivo single photon emission imaging studies in small animals.
Thermally sprayed coatings are being studied and developed as methods of enabling lightweight composites to be used more extensively as structural components in propulsion applications in order to reduce costs and improve efficiency through weight reductions. The primary goal of this work is the development of functionally graded material [FGM] polymer/metal matrix composite coatings to provide improved erosion/oxidation resistance to polyimide-based polymer matrix composite [PMC] substrates. The goal is to grade the coating composition from pure polyimide, similar to the PMC substrate matrix on one side, to 100% WC-Co on the other. Both step-wise and continuous gradation of the loading of the WC-Co reinforcing phase are being investigated, Details of the coating parameter development will be presented, specifically the high velocity oxy-fuel [HVOF] combustion spraying of pure PMR-I1 matrix material and layers of various composition PMR-II/WC-Co blends onto steel and PMR-15 composite substrates. Results of the HVOF process optimization, microstructural characterization, and analysis will be presented. The sprayed coatings were evaluated using standard metallographic techniques - optical and scanning electron microscopy [SEMI. An SEM + electron dispersive spectroscopy [EDS] technique has also been used to confirm retention of the PMR-I1 component. Results of peel/butt adhesion testing to determine adhesion will also be presented.
The purposes of our ongoing investigations of Apollo 15 green and Apollo 17 orange and black volcanic glasses are threefold: first, to increase our understanding of the volcanic origin of the glasses; second, to determine the nature of the coating materials deposited on the glasses during their cooling in the volcanic environment; and, third, to help determine the nature of the gases involved in the volcanic fire-fountaining that occurred at approximately 3.5 Ga on the moon. We are continuing studies of coatings on volcanic glasses using analytical techniques not available when these glasses were originally studied; these include high-resolution FE-TEM and X-ray mapping, along with other highly detailed methods including TEM electron diffraction analysis. Initial studies of Apollo 15 green volcanic glasses using the techniques described above revealed for the first time the presence of areas containing distinct layering of volcanic surface deposits. S was associated with some of the inner layer of metallic Fe but was absent from the outer layer. Zn was associated with S in some places in the inner layer. An example of a typical spherule used for this study is shown in Fig. 1. It is a black (quench-crystallized) bead from near the bottom of the 74001/2 double drive tube; black beads such as this one are essentially identical in composition to the orange (uncrystallized) beads of the 74001/2 core.
Waveguide component technology at terahertz frequencies has come of age in recent years. Essential components such as ortho-mode transducers (OMT), quadrature hybrids, filters, and others for high performance system development were either impossible to build or too difficult to fabricate with traditional machining techniques. With micromachining of silicon wafers coated with sputtered gold it is now possible to fabricate and test these waveguide components. Using a highly optimized Deep Reactive Ion Etching (DRIE) process, we are now able to fabricate silicon micromachined waveguide structures working beyond 1 THz. In this paper, we describe in detail our approach of design, fabrication, and measurement of silicon micromachined waveguide components and report the results of a 1 THz canonical E-plane filter.
Atomic Layer Deposition (ALD) is a cost effective nano-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. Through the introduction of paired precursor gases thin films can be deposited on a myriad of substrates ranging from glass, polymers, aerogels, and metals to high aspect ratio geometries. This talk will focus on the utilization of ALD for engineering applications.
Microstructured optical fibers containing quantum dots scintillation material comprised of zinc sulfide nanocrystals doped with magnesium sulfide are presented. These quantum dots are applied inside the microstructured optical fibers using capillary action. The x-ray photon counts of these fibers are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The results of the fiber light output and associated effects of an acrylate coating and the quantum dot application technique are discussed.