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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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Spore recovery form cured silicone potting compounds using amine solvents to degrade the cured polymers was investigated. A complete list of solvents and a description of the effect of each on two different silicone polymers is provided.
A metal film liftoff process includes applying a polymer layer onto a silicon substrate, applying a germanium layer over the polymer layer to create a bilayer lift off mask, applying a patterned photoresist layer over the germanium layer, removing an exposed portion of the germanium layer, removing the photoresist layer and a portion of the polymer layer to expose a portion of the substrate and create an overhanging structure of the germanium layer, depositing a metal film over the exposed portion of the substrate and the germanium layer, and removing the polymer and germanium layers along with the overlaying metal film.
A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.
A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium boride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.
This work describes the development and evaluation of advanced technologies for the integration of electronic die within membrane polymers. Specifically, investigators thinned silicon die, electrically connecting them with circuits on flexible liquid crystal polymer (LCP), using gold thermo-compression flip chip bonding, and embedding them within the material. Daisy chain LCP assemblies were thermal cycled from -135 to +85degC (Mars surface conditions for motor control electronics). The LCP assembly method was further utilized to embed an operational amplifier designed for operation within the Mars surface ambient. The embedded op-amp assembly was evaluated with respect to the influence of temperature on the operational characteristics of the device. Applications for this technology range from multifunctional, large area, flexible membrane structures to small-scale, flexible circuits that can be fit into tight spaces for flex to fit applications.
Synthesis and thermal properties of fluoroaromatic silicon and carbon polymers for space use
Materials with potential applications in reflective and refractive solar dynamic concentrators are tested for resistance to atomic oxygen degradation. It is found that inorganic coatings such as MgF2, SiO(x), and ITO provide excellent protection for reflective surfaces while organic materials are much more susceptible to erosion and mass loss. Of the organic polymers tested, the silicones have the highest intrinsic resistance to atomic oxygen degradation.
The present thermal management system for a carrier-based Mach 5 cruise-capable aircraft whose propulsion system does not entail cryogenic fuels is predicated on the use of the catalytic endothermic reaction of a petroleum-derived hydrocarbon fuel as the heat sink for engine cooling. The insulation of engine flowpath surfaces reduces cooling requirements. The primary elements of this closed-cycle cooling system are a fuel preheater, a catalytic fuel reactor, and engine wall-cooling panels; a silicone-based liquid polymer is used as the coolant. Structural, weight, and thermal analysis results are presented for each of the primary components.
A cooling system and insulation concept for a Mach 5 cruise aircraft, using non-cryogenic fuel is presented. Catalytic endothermic reaction of petroleum fuel is used as the heat sink for engine cooling. A secondary closed-loop coolant circuit removes heat from the engine and transfers this heat to the catalytic reactor. Insulation on the engine flow path surfaces reduces the cooling requirements. A high temperature insulation system, which is capable of a surface temperature of 4,000 F, is used for the combustor and nozzle. A complete closed-loop cooling system design is shown in detail. Main features of this system include a fuel preheater, a catalytic fuel reactor, and engine wall cooling panels. A silicone-based liquid polymer, designed for extended use at 750 F, is used as the coolant. The preheater and reactor design are based on the results of recent experimental work. The cooling panels are designed using a thermal fluid analysis computer program, which was originally developed for the National Aero-Space Plane (NASP). Major components are analyzed structurally as well as thermally and weights are presented.
The objective of CAM is to develop, test, and analyze thin film membrane materials for separation and purification of carbon dioxide (CO2) from mixtures of gases, such as those found in the Martian atmosphere. The membranes are targeted toward In Situ Resource Utilization (ISRU) applications that will operate in extraterrestrial environments and support future unmanned and human space missions. A primary application is the Sabatier Electrolysis process that uses Mars atmosphere CO2 as raw material for producing water, oxygen, and methane for rocket fuel and habitat support. Other applications include use as an inlet filter to collect and concentrate Mars atmospheric argon and nitrogen gases for habitat pressurization, and to remove CO2 from breathing gases in Closed Environment Life Support Systems (CELSS). CAM membrane materials include crystalline faujasite (FAU) zeolite and rubbery polymers such as silicone rubber (PDMS) that have been shown in the literature and via molecular simulation to favor adsorption and permeation of CO2 over nitrogen and argon. Pure gas permeation tests using commercial PDMS membranes have shown that both CO2 permeance and the separation factor relative to other gases increase as the temperature decreases, and low (Delta)P(Sub CO2) favors higher separation factors. The ideal CO2/N2 separation factor increases from 7.5 to 17.5 as temperature decreases from 22 C to -30 C. For gas mixtures containing CO2, N2, and Ar, plasticization decreased the separation factors from 4.5 to 6 over the same temperature range. We currently synthesize and test our own Na(+) FAU zeolite membranes using standard formulations and secondary growth methods on porous alumina. Preliminary tests with a Na(+) FAU membrane at 22 C show a He/SF6 ideal separation factor of 62, exceeding the Knudsen diffusion selectivity by an order of magnitude. This shows that the membrane is relatively free from large defects and associated non-selective (viscous flow) transport mechanisms. The Membrane Test Facility (MTF) has been developed to measure membrane permeance over a wide range of temperature and pressure. The facility uses two volume compartments separated by the membrane that are instrumented to measure temperature, delta pressure across the membrane, and gas composition. A thermal shroud supports and encloses the membrane, and provides temperature control. Methods were developed to determine membrane permeance using the first order decay of the pressure difference between the sealed compartments, using the total pressure for pure gases, and partial pressure of each species in gas mixtures. The technique provides an end-to-end measurement of gas permeance that includes concentration polarization effects. Experiments have shown that in addition to membrane permeance properties, the geometry and design of associated structures play an important role in how membrane systems will function on Mars.
Despite many studies of subsurface imaging of carbon nanotube (CNT)-polymer composites via scanning electron microscopy (SEM), significant controversy exists concerning the imaging depth and contrast mechanisms. We studied CNT-polyimide composites and, by threedimensional reconstructions of captured stereo-pair images, determined that the maximum SEM imaging depth was typically hundreds of nanometers. The contrast mechanisms were investigated over a broad range of beam accelerating voltages from 0.3 to 30 kV, and ascribed to modulation by embedded CNTs of the effective secondary electron (SE) emission yield at the polymer surface. This modulation of the SE yield is due to non-uniform surface potential distribution resulting from current flows due to leakage and electron beam induced current. The importance of an external electric field on SEM subsurface imaging was also demonstrated. The insights gained from this study can be generally applied to SEM nondestructive subsurface imaging of conducting nanostructures embedded in dielectric matrices such as graphene-polymer composites, silicon-based single electron transistors, high resolution SEM overlay metrology or e-beam lithography, and have significant implications in nanotechnology.
The integration of high quality, single crystal thin film gallium arsenide (GaAs) and indium phosphide (InP) based photonic and electronic materials and devices with host microstructures fabricated from materials such as silicon (Si), glass, and polymers will enable the fabrication of the next generation of micro-opto-mechanical systems (MOMS) and optoelectronic integrated circuits. Thin film semiconductor devices deposited onto arbitrary host substrates and structures create hybrid (more than one material) near-monolithic integrated systems which can be interconnected electrically using standard inexpensive microfabrication techniques such as vacuum metallization and photolithography. These integrated systems take advantage of the optical and electronic properties of compound semiconductor devices while still using host substrate materials such as silicon, polysilicon, glass and polymers in the microstructures. This type of materials optimization for specific tasks creates higher performance systems than those systems which must use trade-offs in device performance to integrate all of the function in a single material system. The low weight of these thin film devices also makes them attractive for integration with micromechanical devices which may have difficulty supporting and translating the full weight of a standard device. These thin film devices and integrated systems will be attractive for applications, however, only when the development of low cost, high yield fabrication and integration techniques makes their use economically feasible. In this paper, we discuss methods for alignment, selective deposition, and interconnection of thin film epitaxial GaAs and InP based devices onto host substrates and host microstructures.
Specifications for polymer spacecraft materials - standardized vacuum weight loss apparatus and procedure - weight loss behavior of silicone, epoxy, and fluorocarbon polymers in vacuum
The topics discussed include the following: effects of solvent and polymer exposures on nitriding kinetics of high purity Si powders and on resulting phase distributions; effects of solvent and polymer exposures on Si Surface Chemistry; effects of solvent and polymeric exposures on nitriding kinetics; and fabrication of flexural test samples.
Highly crosslinked polymers, commonly utilized in spacecraft component fabrication, especially for heatshields, have historically encountered challenges due to their inherent brittleness. To overcome this issue, researchers have explored the incorporation of additives into the polymer backbone to enhance flexibility and durability. This study aims to improve the flexibility and durability of highly crosslinked polymers by introducing long-chain aliphatic silicon-based additives with varying molecular weights into the polymer backbone. By increasing the flexibility of these brittle polymers, they can be effectively employed in constructing intricate curvatures for heatshields, eliminating the need for gap fillers. In this study, we investigated six different additives, comparing them to a highly crosslinked high-temperature polymer used as a baseline. Various characterization techniques, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dilatometry, dynamic mechanical analysis (DMA), nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR), were employed to assess the properties of the materials. The FTIR and NMR results indicated the successful incorporation of the silicon-based additives into the polymer backbone. Furthermore, thermal characterization results demonstrated that certain additives exhibited superior flexibility and lower densities compared to the baseline polymer.
Commercially available polymer derived SiC fibers were treated at temperatures from 1000 to 2200 C in vacuum and argon gas pressure of 1 and 1360 atm. Effects of gas pressure on the thermal stability of the fibers were determined through property comparison between the pressure treated fibers and vacuum treated fibers. Investigation of the thermal stability included studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 1360 atm argon gas treatment was found to shift the onset of fiber weight loss from 1200 to above 1500 C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high pressure treatments. Additional heat treatment in 1 atm argon of the fibers initially treated at 1360 atm argon caused further weight loss and tensile strength degradation, thus indicating that high pressure inert gas conditions would be effective only in delaying fiber strength degradation. However, if the high gas pressure could be maintained throughout composite fabrication, then the composites could be processed at higher temperatures.
Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (Si3N4), and silicon borides (SiB4, SiB6) have thermal stability, oxidation resistance, hardness, and varied electrical properties. All these materials can be prepared in a fiber form from a suitable polymer precursor. The above mentioned fibers, when tested over a temperature range from 25 to 1400 C, experience degradation at elevated temperatures. Past work in ceramic materials has shown that the strength of ceramics containing both carbides and borides is sustained at elevated temperatures, with minimum oxidation. The work presented here describes the formation of ceramic fibers containing both elements, boron and silicon, prepared via the polymer precursor route previously reported by the authors, and discusses the fiber mechanical properties that are retained over the temperature range studied.
This report summarizes results from research on high performance polymers. The research areas proposed in this report include: 1) Effort to improve the synthesis and to understand and replicate the dielectric behavior of 6HC17-PEK; 2) Continue preparation and evaluation of flexible, low dielectric silicon- and fluorine- containing polymers with improved toughness; and 3) Synthesis and characterization of high performance polymers containing the spirodilactam moiety.