Materials and Coatings
Materials and Coatings
See for yourself how NASA materials and coatings can solve real-world problems.
Modification of Pigments Utilizing ALD (Atomic Layer Deposition) in Varying Electrical Resistivity
NASA Goddard Space Flight Center has developed an application for atomic layer deposition (ALD) for coating pigments to prevent charge buildup. Through introducing paired precursor gases, these coatings can be deposited on a myriad of substrates, including glass, polymers, metals, aerogels, and high aspect ratio geometries and powders.
Synthesis and Development of Polyurethane Coatings Containing Fluorine Groups for Adhesive Applications
Coatings offer an advantage over previous strategies due to ease of application, potentially negligible weight penalty, reduced environmental concerns, better economics, and continual function throughout the flight profile. In this present innovation, a particular coating has been developed that is similar to the basic component of a majority of aerospace coatings used on commercial aircraft. This coating was then sprayed from a solvent on various substrates. Once spray-coated on a substrate and dried, the coatings were then tested for adhesion mitigation of insect residues in a controlled insect impact facility propelled toward the engineered surface at approximately 150 mph. Once impacted, these coatings demonstrated hydrophobicity and a significant reduction in contaminant adhesion. The coatings were further tested in an operational environment on the eco-demonstrator Boeing 757 aircraft. The coatings resulted in lower insect accumulation than the control surface (no coating). The durability of these coatings was comparable to state-of-the-art formulations and satisfies current aircraft manufacturing requirements. These coatings likely have advantageous use in aerospace applications, wind turbine systems, and automotive industry, among other industries. This innovation not only appears to solve a problem that has persisted, thus fulfilling an unmet need, but also comprises a new composition of matter that can lead to numerous unforeseen applications.
High-Performance Polyimide Powder Coatings
Powder coatings are used throughout industry to coat a myriad of metallic objects. This method of coating has gained popularity because it conserves materials and eliminates volatile organic compounds. Resins traditionally chosen for powder coatings have low melting points that enable them to melt and flow into a smooth coating before being cured to a durable surface. High-performance resins, such as Teflon, nylon, and polyimide, have not been found suitable for use in powder coatings because of their high melting points. However, KSC's newly developed polyamic acid resins with low melting points can be used in a powder coating. These polyamic acid resins, when sprayed onto metal surfaces, can be cured in conventional powder coating ovens to deliver high-performance polyimide powder coatings. The polyimide powder coatings offer superior heat and electrical stability as well as superior chemical resistance over other types of powder coatings.
Molecular Adsorber Coating (MAC)
MAC is a zeolite based coating that captures and traps molecules in its microscopically porous structure. This microscopic nano-textured structure, consisting of large open pores or cavities, within a crystal- like structure, provides a large surface area to mass ratio that maximizes available trapping efficiency. MAC is a durable coating that is applied through spray application. These sprayable coatings eliminate the major drawbacks of puck type adsorbers (weight, size, and mounting hardware requirements), resulting in cost savings, mass savings, easier utilization, greater adsorber surface area, more flexibility, and higher efficiency. This coating works in air, as well as vacuum systems, depending on the application. There is potential for ground based spin-off applications of this coating, particularly in areas where contaminants and volatile compounds need to be collected and contained. Example industries include: pharmaceutical production, the food industry, electronics manufacturing (circuit boards and wafers), laser manufacturing, vacuum systems, chemical processing, paint booths, and general gas and water adsorption.
Niobium Titanium Nitride Thin Film Coating
The Niobium Titanium Nitride (NbTiN) Thin Film Coating can optically couple light to a bolometric detector, which is suspended on an ultra-thin dielectric membrane. The coating can also filter out low frequency spectral components, which would increase the photon-limited noise of the detector. NbTiN thin film coatings are fabricated on dielectric substrates using a specialized reactive sputtering co-deposition process. Two different sputtering sources are used, in which one source contains a niobium sputtering target and the other contains a titanium sputtering target. The niobium and titanium are deposited in a nitrogen-rich environment. NbTiN coating can be used by depositing it on one side of an ultra-thin silicon membrane and have a well-defined optical impedance requirement for a specific application. NbTiN coating can be deposited on non-silicon membranes as well. The NbTiN coating have low intrinsic stress, which makes it mechanically compatible with integration on ultra-thin dielectric membranes. The coating possesses the optical impedance required for a high optical efficiency absorption. Furthermore, the coating has a very low superconducting transition temperature, which enables it to filter out radiation at certain frequencies. The NbTiN coating is especially useful for ultrasensitive cryogenic bolometric detector applications. The NbTiN coating can be fabricated in a reproducible manner, while simultaneously not complicating the fabrication process of detector architectures.
Liquid Coating for Corrosion Prevention in Rebar
NASA's highly reliable, low-cost liquid-applied coating offers companies the ability to conveniently protect embedded steel rebar surfaces from corrosion. The inorganic, galvanic coating contains one or more of the following metallic particles: magnesium, zinc, or indium. In addition, the coating may contain moisture-attracting compounds that facilitate the protection process. After the coating is applied to the outer surface of reinforced concrete, an electrical current is established between the metallic particles and the surfaces of the embedded steel rebar. This electrical (ionic) current is responsible for providing the necessary cathodic protection for the embedded rebar surfaces. Coating performance has been characterized by KSC's Materials Science Laboratory and Beach Corrosion Test Site. Early tests determined that the coating met National Association of Corrosion Engineers (NACE) RP0290-90 100-millivolt (mV) polarization development/decay depolarization criteria for complete protection of steel rebar embedded in concrete. Other tests verified that the embedded rebar became negatively polarized, indicating the presence of a positive current flow with a shift in potential of over 400 mV. Accelerated life tests, tests with chlorides to simulate contamination, and compound optimization tests are currently being performed.
Conductive High-Toughness Oxides
Oxide coatings have been used in thermal and environmental barrier layers for coatings for hot section turbine applications, among other uses. With the PS-PVD method, Glenn researchers observed the formation of a minority phase of a metastable oxide (zirconium oxide) that is usually found only in a vapor state. They found that the high temperatures and fast deposition process of the PS-PVD system incorporated nonequilibrium phases in the coating and retained them at room temperature as well as at high temperature in the absence of oxygen. The material is vaporized and condensed on the surface via a rapid quenching, essentially "trapping" this phase in the deposited coating. The coating microstructure and composition can also be manipulated by changing the processing parameters, allowing the thickness of the coating to be tailored to a given application. Since this metastable phase is conductive, this coating can be used as (for example) an extremely sensitive (thermal or temperature) sensor. It also has very good durability and erosion resistance, making it useful as a protective and conductive coating for electronics and microelectronics. This is an early-stage technology requiring additional development, and Glenn welcomes co-development opportunities.
Nanostructured coatings for enhanced hardness and superior lubrication in space mechanisms
Ultra-Thin Large Area Polymer Film Fabrication Process
The Ultra-Thin Large Area Polymer Film Fabrication Process incorporates a class of polymer materials called cyclic olefin copolymers (COC). COC films have high transparency, minimal absorption bands in far-infrared, exceptional mechanical strength, low moisture absorption and compatibility with standard fabrication process chemicals. The process creates ultra-thin sheets of COC film over large areas that can be used for optical windows, filters and optical components from the X-ray to the far-infrared. Additionally, the process allows for allows highly uniform thin films with topography. The fabrication process starts begins with a silicon wafer that is patterned with photolithography and etched using deep reactive ion etching. A cryogenic etching process may be used to reduce sidewall roughening. After the photoresist is removed, the silicon is cleaned and rendered hydrophobic through standard microfabrication processes. The COC film is spun on the etched silicon wafer, where the etched silicon wafer acts as a mold for the COC film. The COC film is baked on a hotplate. Since the COC film is a thermoplastic it will reflow during the curing process and fill the areas etched in the silicon wafer and planarize it's thickness. The COC film is able to be removed from the silicon wafer using a polymer tape frame and water submersion process. This fabrication process ultimately results in thin film that can have bumps or steps in areas where the silicon wafer has been etched for topography purposes.
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