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At least 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

NASA and ESA Collaboration on Hexavalent Chrome Free Coatings

Presentation on the NASA and ESA Collaboration on Hexavalent Chrome Free Coatings project. Project is in response to a Memorandum of Understanding between NASA and ESA Concerning Cooperation in the Field of Space Transportation - signed September 11, 2009. The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) have expressed mutual interest in pursuing cooperation in the areas of evaluating hexavalent chrome-free coatings, environmentally-preferable coatings for maintenance of launch facilities and ground support equipment, citric acid as an alternative to nitric acid for passivation of stainless steel alloys.

Hexavalent Chrome Free Coatings↗
NASA NTRS2017

High Temperature Degradation of Advanced Thermal and Environmental Barrier Coatings (TEBCs) by CaO-MgO-Al2O3-SiO2 (CMAS)

There is increasing interest in the degradation studies of thermal and environmental barrier coatings (TEBCs) of gas turbines by molten CaO-MgO-Al2O3-SiO2 (CMAS). CMAS minerals are usually referred as silica-containing sand dust and volcano ash materials that are carried by the intake air into gas turbines, e.g. aircraft engines. The low-melting deposits react at high temperatures (1000C) with the coating materials. This causes degradation and accelerated coating failure of the static and rotating components of the turbine engines. We discuss some preliminary results of the reactions between CMAS and Rare-Earth (RE Y, Yb, Dy, Gd, Nd and Sm) oxide stabilized ZrO2 or HfO2 systems, and the stability of the resulting oxides and silicates. Plasma sprayed hollow tube samples (outer diameter 4.7 mm, wall thickness 0.76 mm and 26 mm height) were half filled with CMAS powder, wrapped and sealed with platinum foil, and heat- treated at 1310 C for 5h. Samples were characterized by differential scanning calorimetry, X-ray diffraction and cross section electron microscopy analysis.

Thermal and environmental barrier coatings↗
NASA NTRS2015

Aluminum Mirror Coatings for UVOIR Telescope Optics Including the Far UV

NASA Cosmic Origins (COR) Program identified the development of high reflectivity mirror coatings for large astronomical telescopes particularly for the far ultra violet (FUV) part of the spectrum as a key technology requiring significant materials research and process development. In this paper we describe the challenges and accomplishments in producing stable high reflectance aluminum mirror coatings with conventional evaporation and advanced Atomic Layer Deposition (ALD) techniques. We present the current status of process development with reflectance of approx. 55 to 80% in the FUV achieved with little or no degradation over a year. Keywords: Large telescope optics, Aluminum mirror, far UV astrophysics, ALD, coating technology development.

large telescope optics↗
NASA NTRS2018

Simulation of Stochastic Mud-Crack Damage Formation in an Environmental Barrier Coating

The integrated Finite Element Analysis–Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program was used to simulate the formation of mudflat-cracks from thermomechanical loading on a multi-layered Environmental Barrier Coating (EBC) system deposited on a ceramic substrate. FEAMAC/CARES combines MAC/GMC multiscale composite micromechanics code with CARES/Life probabilistic multiaxial failure criteria code and Abaqusfinite element analysis. In this work, step function elastic modulus reduction of randomly damaged finite elements was used to represent discrete cracking events. The use of many small-sized low-aspect-ratio finite elements enabled the depiction of crack boundaries and formation of mudflat patterned damage. Demonstrated examples include finite element models of button–sized disk–shaped 3-D specimen, and a 2-D model of through-the-thickness cross-section. All models were subjected to a progressive cool down from 1300oC to room temperature. Mudflat crack damage in the coating system resulted from the buildup of residual tensile stresses between the individual material constituents from thermal expansion mismatch. A 2-parameter Weibull distribution characterized the coating layer stochastic strength response and the effect of the Weibull modulus on the formation of damage was studied here.

residual tensile stress↗
NASA NTRS2019

A Preliminary Study on the Use of a NASA Developed Coatings Technology for Protecting Natural Science Collections from Molecular Contaminants

Many museum conservators and collection managers are faced with the challenge of molecular contaminants that can promote the degradation of specimens on display in exhibits or in cabinets at storage facilities. This has prompted the need to explore innovative techniques to alleviate the presence of chemical species that originate from atmospheric off-gassing of materials or cross-contamination among collection items. For example, the Smithsonian Institution's National Museum of Natural History (NMNH) has tackled this problem for many years, specifically targeting contaminants, such as mercury vapor, at its Museum Support Center (MSC) storage facility in Suitland, Maryland. Similarly, the presence of molecular contaminants poses a significant threat for NASA science and exploration missions. The deposition of chemical species on sensitive surfaces can degrade the performance and operational lifetime of satellites, telescopes, and instruments. As a result, a sprayable zeolite-based coatings technology was designed to passively capture molecular contaminants and reduce the risks associated with material outgassing in vacuum environments for aerospace applications. This technology, called the Molecular Adsorber Coating (MAC), was developed at NASA Goddard Space Flight Center (GSFC). MAC has been extensively used during thermal vacuum chamber testing of various spaceflight hardware and components, such as for the James Webb Space Telescope (JWST). The coating is also planned to fly aboard upcoming NASA missions to address on-orbit outgassing concerns within instrument and laser cavities. Recently, the MAC technology was evaluated as a possible solution for protecting the Smithsonian Institution's natural science specimens, specifically its mineral ore and botany collections at the MSC storage facility. The initial year-long study between NASA GSFC and NMNH involved investigating the effectiveness of the MAC technology in capturing molecular contaminants that are present within the collections and storage cabinets at ambient, non-vacuum conditions. The work included sample fabrication, installation and retrieval efforts, testing efforts and associated challenges, preliminary findings, and future plans for the multi-year project.

conservation↗
NASA NTRS2018

Weibull-Based Stochastic Simulation of Mud-Crack Damage Formation in an Environmental Barrier Coating

The integrated Finite Element Analysis Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program was used to simulate the formation of mudflat-cracks from thermomechanical loading on a multi-layered Environmental Barrier Coating (EBC) system deposited on a ceramic substrate. FEAMAC/CARES combines MAC/GMC (Micromechanics Analysis Code/Generalized Method of Cells) multiscale composite micromechanics code with CARES/Life probabilistic multiaxial failure criteria code and Abaqusfinite element analysis. In this work, step function elastic modulus reduction of randomly damaged finite elements was used to represent discrete cracking events. The use of many small-sized low-aspect-ratio finite elements enabled the depiction of crack boundaries and formation of mudflat patterned damage. Demonstrated examples include finite element models of button-sized disk-shaped 3-D specimen, and a 2-D model of through-the-thickness cross-section. All models were subjected to a progressive cool down from 1300 degrees Centigrade to room temperature. Mudflat crack damage in the coating system resulted from the buildup of residual tensile stresses between the individual material constituents from thermal expansion mismatch. A 2-parameter Weibull distribution characterized the coating layer stochastic strength response and the effect of the Weibull modulus on the formation of damage was studied here.

Residual Tensile Stress↗
NASA NTRSDate not supplied

Developing Materials and Coating Technologies for Mitigation of Lunar Dust Adhesion and Abrasion

In order to support long duration missions on the Moon’s surface, materials resistant to the harsh lunar environment are critically needed. Lunar dust poses a major threat to the durability of components and vehicles due to its fine, jagged morphology and highly abrasive nature, enabling the particles to adhere and embed onto surfaces of components and devices and potentially leading to premature failure. There is significant effort within NASA to develop novel materials and coating technologies to mitigate lunar dust adhesion and abrasion. This effort has been exploring a variety of production routes and examining properties of candidate material systems, including ceramic, metallic and polymeric. Manufacturing methods investigated include ceramic powder processing, additive manufacturing and surface modification via laser ablation patterning of bulk materials and coatings. An overview of ongoing NASA materials and coating research and development efforts to enable lunar surface exploration will be presented.

Materials, Coatings, lunar dust mitigation↗
NASA NTRSDate not supplied

Passive Thermal Coating Observatory Operating in Low-Earth Orbit (PATCOOL)

Long-term presence on the moon, mars, and beyond necessitates the transport of liquid oxygen (LOX). Resources are limited in space and LOX not only servers as an oxidizer for fuel, but can also be utilized in the production of breathable air for space habitats. A cryogenic thermal control coating, developed by scientists at Kennedy Space Center (KSC), is getting ready to demonstrate it has the potential to answer these challenges. Aluminum samples coated with the cryogenic thermal control coating and AZ-93 white paint will be launching to the International Space Station (ISS) and deployed on a CubeSat into a low-earth orbit. This work covers the predicted sample temperatures in a simulated space environment and a review of the Thermal Desktop model.

Cryogenic Thermal Control Coating↗
NASA NTRSDate not supplied

Developing Materials and Coating Technologies for Mitigation of Lunar Dust Adhesion and Abrasion

In order to support long duration missions on the Moon’s surface, materials resistant to the harsh lunar environment are critically needed. Lunar dust poses a major threat to the durability of components and vehicles due to its fine, jagged morphology and highly abrasive nature, which enables the particles to adhere and embed into surfaces of components and devices potentially leading to premature failure. Consequently, significant effort within NASA aims to develop novel materials and coating technologies to limit lunar dust adhesion and abrasion by exploring a variety of production routes and examining properties of candidate material systems, including ceramic, metallic and polymeric. Manufacturing methods investigated include traditional powder processing, additive manufacturing and surface modification via laser ablation patterning of bulk materials and coatings. An overview of ongoing NASA materials and coating research and development to enable lunar exploration will be presented.

Materials↗
NASA NTRS2021

Modeling of the Influence of Thermally Grown Oxide (TGO) Layers on the Driving Forces in Environmental Barrier Coating Systems

Environmental barrier coatings (EBC) are an enabling technology for the successful application of ceramic matrix composites (CMCs) in air-breathing gas turbine engines. EBCs are susceptible to several failure modes including oxidation/delamination, recession, chemical attack and dissolution, thermomechanical degradation, erosion, and foreign object impact damage in a combustion environment. Spallation of environmental barrier coating (EBC), induced by a thermally grown oxide (TGO) layer, is a key EBC failure mode. The TGO layer, resulting from steam oxidation, grows either from a silicon bond coat layer (if present) or from a silicon carbide (SiC) based substrate itself. The TGO layer evolves (i.e., thickness increases with time) as water vapor and oxygen gradually diffuse through the EBC, and the EBC spalls off once the TGO layer reaches some critical thickness. The critical thickness of the TGO layer for failure is in the range of 20-30 microns, with the actual value depending upon exposure temperature, microstructure, etc. Current work at NASA Glenn Research Center, under the Transformative Tools and Technology (TTT) subproject is aimed at addressing associated failure modes in EBC systems and developing robust analysis tools to aid in the design/analysis of these systems. The objective of the current work is to conduct a sensitivity study to examine the influence of uniformly and non-uniformly grown oxide layers on the associated driving forces leading to spallation of the EBC when subjected to isothermal loading. The effect of damage in the TGO layer on the resulting stress states is also assessed both in uniform and non-uniform TGO layers.

Coatings↗
NASA NTRS2021

Solid Particle Erosion of a Plasma Spray – Physical Vapor Deposition Environmental Barrier Coating in a Combustion Environment

Environmental barrier coatings (EBCs) were developed to reduce the susceptibility of SiC-based composites to the rapid volatilization and surface recession that occurs in the presence of water vapor. Extensive research and development has been performed on EBCs, and their corresponding failure mechanisms under different environmental conditions. However, one key failure mechanism, solid particle erosion (SPE), has not been thoroughly investigated. As a result, the present work investigates the SPE behavior of a ytterbium disilicate (Yb2Si2O7) environmental barrier coating (EBC) deposited via plasma spray-physical vapor deposition (PS-PVD). Erosion testing was performed at elevated temperature (1,200 °C) in a simulated combustion environment at the NASA Glenn Research Center Erosion Burner Rig Facility. Alumina (Al2O3) particles were used as the eroding media. A range of particle kinetic energies and impingement angles were investigated along with the effect of coating surface roughness. The post-erosion damage morphology was characterized using scanning electron microscopy (SEM). The SPE behavior of the PS-PVD EBC was shown to be comparable to other EBC systems reported in the literature.

Solid particle erosion; environmental barrier coat↗
NASA NTRSDate not supplied

Preliminary Coating Development for Solar Thermal Propulsion (STP)

Solar Thermal Propulsion (STP) utilizes the sun’s thermal energy to create thrust, enabling rapid transit to interstellar medium via the Oberth Maneuver. For this, the system would fly very close to the sun, so an optical, “white” coating on a graphite substance is required to regulate the system’s temperature. However, standard heat shield coatings degrade over the STP heating profile of 2500 °K over multiple hours. Thus, an optical coating should be designed with the ability to control reflectance and microstructural evolution during operation.

Solar Thermal Propulsion↗
NASA NTRSDate not supplied

Development of Luminescence Lifetime-Based Surface Temperature Mapping for Environmental Barrier Coatings

Luminescence lifetime-based temperature mapping for thermal barrier coatings (TBCs) has been previously demonstrated up to temperatures approaching 1200 °C. Advantages of this method include insensitivities to reflected radiation and emissivity uncertainties. Because of a push towards greater efficiency turbine engine operation using higher turbine inlet temperatures, there is an ongoing movement from TBC-coated superalloy turbine engine components to SiC/SiC ceramic matrix composite components protected by environmental barrier coatings (EBCs). The useful application of luminescence lifetime-based temperature mapping to EBCs requires a significant increase in high temperature capability from below 1200 °C up into the 1300 to 1500 °C temperature range where the much higher background thermal radiation is a challenging issue. In addition, the luminescing sensing layer must exhibit thermochemical compatibility with the EBC. To meet these requirements, Er-doped Y 2 SiO 5 was selected as the luminescing sensor layer material both for its enhanced temperature sensitivity above 1300 °C and its compatibility with rare-earth disilicate EBC topcoats. Both localized spot temperature measurements as well as luminescence lifetime imaging-based temperature mapping were demonstrated up to 1560 °C for Er-doped Y 2 SiO 5 disks. In addition, temperature mapping capability was demonstrated from a 15 µm thick Er-doped Y 2 SiO 5 layer at the surface of a Sc 2 Si 2 O 7 based EBC topcoat. Both localized spot and temperature mapping by luminescence lifetime imaging were demonstrated up to 1380 °C (upper temperature limit of this slurry-based layered EBC) with excellent suppression of background thermal radiation and no degradation of the Er-doped Y 2 SiO 5 temperature sensing surface layer. The source of the novel enhanced temperature sensitivity above 1300 °C will be discussed as well as a path towards compatibility between sensing layer and EBC topcoat to higher temperatures.

temperature measurement↗
NASA NTRSDate not supplied

Passive Charge Dissipating Work Function Matching Coating for Reducing Adhesion of Lunar Dust

The NASA Glenn Research Center Environmental Effects and Coatings Branch is developing a passive coating for lunar dust mitigation. This simple, transparent, conductive coating will be capable of reducing lunar dust adhesion to surfaces and dissipating surface charge. Anticipated benefits include compatibility with active dust mitigation strategies, improved efficiency and performance of solar cells and thermal control surfaces, and protection of astronauts and equipment on the lunar surface.

Lunar dust↗
DOE OSTI2024

Effects of Coatings on Water Intrusion and Strain Gauge Durability in Submerged Fatigue Conditions: Preprint

Marine energy structures are typically made using composite materials and are repeatedly loaded by currents and waves. Submersion and repeated loading lead to two environmental effects: moisture intrusion and mechanical fatigue. To understand the combined effects of moisture intrusion and mechanical fatigue on marine energy structures, submerged fatigue testing can be used. Submerged fatigue testing often requires submerged instrumentation to validate component manufacturing methods and models. Measuring strain is critical for understanding marine energy component loads. One common method for measuring strain is by using foil strain gauges, but the durability of strain gauges in submerged fatigue conditions was not well-understood. To increase strain gauge durability and protection from contamination, delamination, and water intrusion, strain gauge coatings may be applied over strain gauges and wire connections. In this study, strain gauges were adhered to composite coupons, coated, and mechanically tested in a water tank. Cycles to composite failure, cycles to strain gauge failure, strains, and strain gauge failure modes were used to measure the effects of strain gauge coatings on composite fatigue life and strain gauge durability. The methods developed and measurements taken at the coupon scale in this study will be used to inform methods and designs for subsequent submerged subcomponent testing, full-scale testing, and standards development. The benefits of designing marine energy structures to informed standards and designs are decreased lifetime costs and increased reliability and energy production, ultimately leading to a sustainable and low-carbon energy system.

composite fatigue testing↗
DOE OSTI2025

The Effect of Flow on CO2 Corrosion of Self-Healing Metallic Coatings

Internal corrosion is an issue that affects natural gas pipelines, a significant part of the United States energy infrastructure. Over time, this corrosion has worn away longstanding pipelines due to the original construction materials used for the lines and impurities in the gas and liquid streams flowing through them. The main impurities in natural gas are H2O, CO2, H2S, and O2. One of the leading causes of corrosion is the CO2 dissolved in water, giving rise to carbonic acid formation, which can further dissolve the steel pipe. The National Energy Technology Laboratory (NETL) has been studying different solutions to this problem. One potential answer is a self-healing sacrificial metallic coating applied by a novel cold spray technique. Previous studies at NETL have shown that the zinc-rich self-healing coating can withstand corrosion through passivation and create a barrier to the diffusion of corrosive species. This study explored the impact of flow on corrosion with this coating and carbon steel when exposed to a saturated CO2 environment by simulating the pipeline flow profile in a small-scale lab setting. The samples were evaluated using multiple electrochemical techniques that found corrosion rates and were backed up with surface analysis to conclude the behavior of the corrosion mechanisms.

CO2 corrosion↗
DOE OSTI2025

Fe Coated Optical Fiber for Distributed Corrosion Monitoring in Soil and Aqueous Environment

Natural gas pipeline corrosion represents a substantial cost and safety concern during normal operations. Effective monitoring of corrosion is important to detect and mitigate pipeline risks before corrosion-related catastrophic events happen. Here, we describe the use of Fe-coated optical fiber sensors (OFS) for distributed corrosion monitoring where Fe acts as a corrosion proxy. By using an optical backscatterring reflectometer (OBR), corrosion was monitored based on the increase in backscattered intensity amplitude of the light being passed as Fe undergoes corrosion. The Fe-coated OFSs were prepared with a film thickness between 25-225 nm by an electroless plating approach and corroded by a CO2-saturated acidic electrolyte. The corrosion rate was approximately 2.5 mm/yr for Fe with a film thickness of 30 nm and increased with film thickness. Backscattering-based corrosion rates were supported by visible light transmission measurements, which have been previously demonstrated. Additionally, a correlation between the intermittent transmission and residual Fe film thickness during corrosion of Fe was established. Corrosion was measurable out to > 100 m which is a significant improvement over our previous work showing corrosion sensing at < 10 m. The corrosion sensor was also tested in soil at >1 ft depth. Fe-coated OFS was loaded into a Draka cable which provides mechanical support during fiber deployment and installation into either acidified soil, top-soil, or sandy soil.

aqueous environment↗
DOE OSTI2025

Sequential Infiltration Synthesis of Bilayer Porous Alumina Nanostructures for Broad-Angle, Broadband Antireflective Coatings

Antireflective coatings (ARCs) are thin films engineered to reduce light reflections. Delivering broadband, wide-angle performance is essential for photovoltaics, imaging, and sensing, yet truly omnidirectional antireflection remains difficult due to angle-dependent optical paths and a narrow palette of suitable refractive indices. Here, in this study, we systematically investigate an emerging class of multilayer inorganic ARCs based on conformally coated nanoporous alumina templated by intrinsically microporous polymers (PIMs) and block copolymers (BCPs). We establish a design framework that maps thickness reflectance relationships to identify thickness pairs minimizing reflection across wavelength and incidence angle. We show that deliberately separating the local reflectance minima of the top and bottom layers in bilayer nanostructures broadens the antireflective bandwidth and angular range. We show that 235-nm single-side bilayer porous alumina nanostructures achieves under 2 % reflectance from 380–750 nm for incidence angles up to 45° with less than 0.6% reflectance for incidence angles under 20°. The approach is readily extensible to additional layers or materials with refractive indices tuned via templated nanoporosity and composition, enabling practical, etch-free ARC fabrication without HF or fluorinated precursors and advancing straightforward design of broadband, wide-angle (quasi-omnidirectional) ARCs for next-generation optical systems.

antireflective coatings↗