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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Low Thermal Conductivity Thermal Barrier Coatings Developed

Thermal barrier coatings (TBCs) are used extensively in modern gas turbine engines to thermally insulate air-cooled metallic components from the hot gases in the engine. These coatings typically consist of a zirconia-yttria ceramic that has been applied by either plasma spraying or physical vapor deposition. Future engines will rely even more heavily on TBCs and will require materials that have even higher temperature capability with improved insulation (i.e., lower thermal conductivity even after many hours at high temperature). This report discusses new TBCs that have been developed with these future requirements in mind. The Ultra-Efficient Engine Technology Program at the NASA Glenn Research Center is funding this effort, which has been conducted primarily at Glenn with contractor support (GE and Howmet) for physical vapor deposition. As stated, the new TBC not only had to be more insulating but the insulation had to persist even after many hours of exposure-that is, the new TBC had to have both lower conductivity and improved sintering resistance. A new type of test rig was developed for this task. This new test approach used a laser to deliver a known high heat flux in an essentially uniform pattern to the surface of the coating, thereby establishing a realistic thermal gradient across its thickness. This gradient was determined from surface and backside pyrometry; and since the heat flux and coating thickness are known, this permitted continuous monitoring of thermal conductivity. Thus, this laser rig allowed very efficient screening of candidate low-conductivity, sinter-resistant TBCs. The coating-design approach selected for these new low-conductivity TBCs was to identify oxide dopants that had the potential to promote the formation of relatively large and stable groupings of defects known as defect clusters. This approach was used because it was felt that such clusters would reduce conductivity while enhancing stability. The approach proved to be successful: low-conductivity TBCs having improved sintering resistance were developed.

Zhu, Dongming↗
NASA NTRS1960

Thermal Design of the Micrometeoroid Satellite S-55

The thermal design of the micrometeoroid satellite S-55 involves both experimental and analytical approaches in selecting materials and coatings. A cutaway drawing of the S-55 satellite is shown. The purpose of which is to obtain scientific and engineering design data on the frequency and penetration hazard of micrometeoroids at altitudes between about 250 nautical miles and 700 nautical miles. The passive method of thermal control used involves the selection of materials and coatings that give the desired ratio of absorptivity to emissivity alpha/epsilon for keeping the telemetry temperature within narrow limits and also to prevent overheating of the separate experiments. The selection of a material or coating for this purpose, however, is dictated not only by its absorptivity and emissivity values, but also by its reliability and the constancy of these values under long exposure to the space environment. Several test programs have been conducted in order to evaluate the materials and coatings being considered. Some of these are as follows: (1) Ultraviolet radiation in a vacuum to study discoloration and weight change. (2) Solar radiation in a vacuum to determine maximum equilibrium temperature, discoloration, and weight loss. (3) Thermal cycling and thermal shock to study material integrity (leaking, spalling, melting, etc.). (4) Proton radiation to observe effects on color, crystal structure, and strength. (5) Determination of effects of heat associated with coating application on the leak rate of pressurized parts. (6) Absorptivity and emissivity measurements. The experimental tests outlined and the maximum use of coating methods successfully employed on previous satellites should provide high reliability of the material used for the thermal design of this vehicle. A theoretical analysis was made to determine the values of alpha/epsilon required for different areas in order that the telemetry remain within the desired temperature limits.

Hastings, Earl C., Jr.↗
NASA NTRS1987

Life prediction and constitutive models for engine hot section anisotropic materials

The results are presented of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and fatigue data, tests were conducted on uncoated and coated specimens loaded in the CH76 100 CH110 , CH76 110 CH110 , CH76 111 CH110 and CH76 123 CH110 crystallographic directions. Two constitutive models are being developed and evaluated for the single crystal materials: a micromechanic model based on crystallographic slip systems, and a macroscopic model which employs anisotropic tensors to model inelastic deformation anisotropy. Based on tests conducted on the overlay coating material, constitutive models for coatings also appear feasible and two initial models were selected. A life prediction approach was proposed for coated single crystal materials, including crack initiation either in the coating or in the substrate. The coating initiated failures dominated in the tests at load levels typical of gas turbine operation. Coating life was related to coating stress/strain history which was determined from specimen data using the constitutive models.

Swanson, G. A.↗
NASA NTRS1995

The effect of interface properties on nickel base alloy composites

This program was performed to assess the extent to which mechanical behavior models can predict the properties of sapphire fiber/nickel aluminide matrix composites and help guide their development by defining improved combinations of matrix and interface coating. The program consisted of four tasks: 1) selection of the matrices and interface coating constituents using a modeling-based approach; 2) fabrication of the selected materials; 3) testing and evaluation of the materials; and 4) evaluation of the behavior models to develop recommendations. Ni-50Al and Ni-20AI-30Fe (a/o) matrices were selected which gave brittle and ductile behavior, respectively, and an interface coating of PVD YSZ was selected which provided strong bonding to the sapphire fiber. Significant fiber damage and strength loss was observed in the composites which made straightforward comparison of properties with models difficult. Nevertheless, the models selected generally provided property predictions which agreed well with results when fiber degradation was incorporated. The presence of a strong interface bond was felt to be detrimental in the NiAI MMC system where low toughness and low strength were observed.

Groves, M.↗
NASA NTRS2001

Testing of Environmentally Preferable Aluminum Pretreatments and Coating Systems for Use on Space Shuttle Solid Rocket Boosters (SRB)

The solid rocket booster (SRB) has historically used a chromate conversion coating prior to protective finish application. After conversion coating, an organic paint system consisting of a chromated epoxy primer and polyurethane topcoat is applied. An overall systems approach was selected to reduce waste generation from the coatings application and removal processes. While the most obvious waste reduction opportunity involved elimination of the chromate conversion coating, several other coating system configurations were explored in an attempt to reduce the total waste. This paper will briefly discuss the use of a systems view to reduce waste generation from the coating process and present the results of the qualification testing of nonchromated aluminum pretreatments and alternate coating systems configurations.

Clayton, C.↗
NASA NTRS1992

Life prediction and constitutive models for engine hot section anisotropic materials program

This report presents the results from a 35 month period of a program designed to develop generic constitutive and life prediction approaches and models for nickel-based single crystal gas turbine airfoils. The program is composed of a base program and an optional program. The base program addresses the high temperature coated single crystal regime above the airfoil root platform. The optional program investigates the low temperature uncoated single crystal regime below the airfoil root platform including the notched conditions of the airfoil attachment. Both base and option programs involve experimental and analytical efforts. Results from uniaxial constitutive and fatigue life experiments of coated and uncoated PWA 1480 single crystal material form the basis for the analytical modeling effort. Four single crystal primary orientations were used in the experiments: (001), (011), (111), and (213). Specific secondary orientations were also selected for the notched experiments in the optional program. Constitutive models for an overlay coating and PWA 1480 single crystal material were developed based on isothermal hysteresis loop data and verified using thermomechanical (TMF) hysteresis loop data. A fatigue life approach and life models were selected for TMF crack initiation of coated PWA 1480. An initial life model used to correlate smooth and notched fatigue data obtained in the option program shows promise. Computer software incorporating the overlay coating and PWA 1480 constitutive models was developed.

Nissley, D. M.↗
NASA NTRS1984

Advanced on-site power plant development technology program

A 30-cell, full area short stack containing advanced cell features was tested for 2900 hours. A stack acid addition approach was selected and will be evaluated on the stack at 5000 hours test time. A brassboard inverter was designed and fabrication was initiated. Evaluation of this brassboard inverter will take place in 1984. A Teflon coated commercial heat exchanger was selected as the preferred approach for the acid condenser. A reformer catalyst with significantly less pressure drop and equivalent performance relative to the 40-K baseline catalyst was selected for the development reformer. The early 40-kW field power plant history was reviewed and adjustments were made to the On-Site Technology Development Program to address critical component issues.

Source record↗
NASA NTRS2003

Microsample Characterization of Coatings for Grcop-84 for High Heat Flux Applications

A multidisciplinary Johns Hopkins University-NASA Glenn team is undertaking a collaborative research program to elucidate and model the thermal stability and mechanical integrity of candidate coatings for GRCop-84. GRCop-84 is a high conductivity, high strength copper alloy that was recently developed at NASA Glenn for use in high temperature, high heat flux applications. With potential applications in rocket motor combustion chamber liners, nozzle ramps and other actively cooled structures, this new material offers great potential for decreasing weight and increasing reliability of third generation reusable launch vehicles. Current emphasis has turned toward the development of environmentally resistant and thermal barrier coatings for this alloy. Metallic coatings such as NiCrAlY and Cu-8-30%Cr have shown promise in: prohibiting blanching, reducing dog-house failures, increasing operating temperatures and decreasing cooling requirements. The focus of this research program is to develop a fundamental understanding of the substrate-coating interactions that occur during thermal cycling (inter-diffusion, viscoplasticity, morphological evolution, crack formation, etc.) and to derive a science-based protocol for future coating selection, optimization and reliability assurance. The microsample tensile testing approach adopted for this study allows us to characterize small-scale and highly scale-specific coatings and properties in a way not possible by conventional means. In addition to providing much needed design data, the integration of microsample testing with detailed microstructural observations provides a mechanistic foundation for coating optimization and life prediction modeling.

Hemker, Kevin↗
NASA NTRS1984

Exposure of spacecraft coatings (S0010)

The objectives of this LDEF experiment are to determine the effects of both the Shuttle-induced environment and the space radiation environment on selected sets of spacecraft thermal control coatings. The experimental approach is to passively expose samples of thermal control coatings to Shuttle-induced and space radiation environments and to return the samples for postflight evaluation and comparison with preflight measurements to determine the effects of the environmental exposure. Optical measurements of the samples will include total normal emittance and spectral reflectance. The experiment will utilize a 6 in. deep peripheral tray and an experiment exposure control canister (EECC). The EECC will provide protection for some of the samples against exposure to the launch and reentry environments. The EECC will be programmed to open about 2 weeks after LDEF deployment and close pior to LDEF retrieval by the Shuttle and reentry. Some samples will not be housed in the EECC and will be exposed to the Shuttle-induced environment during launch and reentry. Comparison of the data from these samples with data from samples in the EECC will yield information about possible contamination induced degradation effects.

Slemp, W. S.↗
NASA NTRS2007

Increasing Durability of Flame-Sprayed Strain Gauges

Thermally sprayed dielectric ceramic coatings are the primary means of attaching strain and temperature gauges to hot-section rotating parts of turbine engines. As hot-section temperatures increase, lifetimes of installed gauges decrease, and seldom exceed one hour above 2,000 F (approx.1,100 C). Advanced engine components are expected to operate at temperatures approaching 2,200 F (approx.1,200 C), and the required high-temperature lifetime is 10 hours minimum. Typically, to enable a ceramic coating to adhere to the smooth surface of an engine component, a thermally sprayed NiCrAlY or NiCoCrAlY bond coat is applied to the smooth surface, thereby providing a textured surface to which the ceramic coat can adhere. The main failure mechanism of this system is decohesion and/or delamination at the interface between the ceramic top coat and the bond coat, caused by oxidation of the bond coat and stresses from the mismatch between the coefficients of thermal expansion of the ceramic top coat and the metallic bond coat. The approach taken to increase the high-temperature lifetime of a gauge attached to an engine component by the method described above involves (1) selective oxidation of the bond coat by means of a heat treatment in reduced oxygen partial pressure followed by (2) the application of a noble-metal diffusion barrier. In experiments to test this approach, heat treatments of NiCoCrAlY bond coats were carried out in a tube furnace in which, in each case, the temperature was alternately (1) increased at a rate of 3 C per minute and (2) held steady for one hour until the desired temperature was reached. The tube furnace was continuously purged with dry nitrogen gas. A final heat-treatment temperature range of 1,600 to 1,800 F (871 to 982 C) proved most beneficial.

Gregory, Otto J.↗
NASA NTRS1985

Finite element analysis of thermal barrier coatings

The near-term objective is to develop an understanding of the states of stresses and strains in a Zirconia-yttria thermal barrier coating (TBC) experiencing a given temperature drop. Results so obtained are expected to facilitate experimental work. In order to gain realistic insights into the distribution of stresses and strains in a complex TBC, the finite element approach was selected to model a cylindrical TBC specimen. Experimental evidence reported in the literature indicated the presence of rough interface between the ceramic coat and bond coat. Oxidation of the bond coat at ceramic-bond interface was observed, as was a small amount of cracking in the ceramics near the ceramic-bond interface. To account for these complex features, a plane-strain finite element computer program known as TBCOC was developed, taking advantage of a generic computer code known as MARC. This generic code was made available through the use of a supercomputer (Cray 1). The TBCOC model contains 1316 nodal points and 2140 finite elements. It is capable of a uniform isothermal loading. Results of a sample computer run are presented.

Chang, G. C.↗
NASA NTRS2024

Hybrid Thermally Efficient Core (HyTEC) HyTEC Phase 1 – Combustor Final Report

The objective of the HyTEC – Combustor Technology project is to develop technology for a compact, low emissions, rich-burn combustor that maintains a high-level of durability. To accomplish this, the combustor will incorporate CMC liners and a CMC Dome to enable improved air utilization for mixing and NOx reduction. In particular, three technology areas were matured: metallic swirler attachment to the CMC dome, Nickel diffusion in CMC, and EBC advancements with improved durability. The maturation of these technology areas is critical to successfully designing a combustor for an engine intended to demonstrate increased thermal efficiency with integrated high-power density-core engine technologies. As part of the project, multiple swirler attachment architectures were matured through the design process, manufactured, and tested in simulated engine conditions. These architectures utilized two different approaches to attachment: a pressure loaded approach and a clamped approach. Each approach required testing at simulated engine conditions to mature the technology. These tests were developed to ensure that the probable failure mechanisms for each architecture were assessed relative to its long-term durability. After successfully testing both approaches, the pressure loaded approach was chosen based on its simplicity and its similarity to the attachment approach used on lean burn combustors. Finally, this successful testing resulted in the swirler attachment technology achieving TRL 4 status. Another aspect of concern with the metallic swirler attachment is the potential for nickel diffusion into the CMC to cause durability shortfalls. A series of tests were completed to understand both the amount of nickel that is expected to diffuse into the CMC and the effect this diffusion will have on mechanical properties of the CMC. After successfully completing this testing, the reduction in local mechanical properties was found to not have an impact on the overall durability of the CMC Dome. To further improve the overall durability, three different EBC coating architectures were also studied. One of these coatings being the current state of the art for CMC liners with the other two being proposed improvements. Coupons were produced using each coating and subjected to a series of laboratory testing. One coating was found to have an overall superior durability in laboratory testing and survived rig testing without indication of degradation. This successful testing resulted in the EBC technology achieving TRL 5 status. Overall, a design approach was successfully down-selected that achieves both the TPM requirements and the need for TRL 4+ status. This design incorporates a pressure loaded swirler attachment with an improved EBC coating (Architecture 1). This combination allows the continued use of a CMC dome and results in an improved durability for the proposed compact core combustor.

CMC↗
NASA NTRSDate not supplied

Material Compatibility Study of Coated Metals to Maintain Biocidal Silver in a Spacecraft Potable Water System

Ionic silver-based biocide is an option of strong interest for future exploration and has been baselined for several emerging spacecraft potable water systems. A challenge for the use of silver biocide remains the depletion of ionic silver on wetted materials of construction. Consequently, the design and/or selection of materials that can be used as the wetted system components need specific consideration. As part of the strategy to address this issue, a multitiered approach is being investigated that looks at combinations of conventional and non-conventional spacecraft treatment processes and materials. In this study, eleven chemically-resistant polymer coatings were applied as surface treatments onto coupons that were cut out from three types of conventional spacecraft-grade metals (Titanium Grade 2, Inconel 718, and 316L Stainless Steel). The coated metals were immersed in a static 400 parts per billion silver biocide solution at a surface-area-to-volume ratio of 2.0 cm^-1 and left to soak for predefined periods of time. The concentration of the solution in contact with the coated samples were then analyzed via inductively coupled plasma mass spectrometry, and the data used to determine the extent to which the coatings provided a barrier to silver loss. This paper summarizes the coating selection process, the configuration of the test, and the performance of each coating-metal combination as a mitigation to silver depletion. The preliminary results demonstrate that select coatings are proving effective at maintaining biocidal silver concentrations. The knowledge acquired through this investigation will be used to assess the feasibility of using these coatings as a robust strategy for maintaining biocidal silver in the water systems. Future studies are planned to assess the specific use of these coatings and to better understand the implications of utilizing this material approach in the future spacecraft potable water system designs.

coatings↗
NASA NTRSDate not supplied

Material Compatibility Study of Coated Metals to Maintain Biocidal Silver in a Spacecraft Potable Water System

Ionic silver-based biocide is an option of strong interest for future exploration and has been baselined for several emerging spacecraft potable water systems. A challenge for the use of silver biocide remains the depletion of ionic silver on wetted materials of construction. Consequently, the design and/or selection of materials that can be used as the wetted system components need specific consideration. As part of the strategy to address this issue, a multitiered approach is being investigated that looks at combinations of conventional and non-conventional spacecraft treatment processes and materials. In this study, eleven chemically-resistant polymer coatings were applied as surface treatments onto coupons that were cut out from three types of conventional spacecraft-grade metals (Titanium Grade 2, Inconel 718, and 316L Stainless Steel). The coated metals were immersed in a static 400 parts per billion silver biocide solution at a surface-area-to-volume ratio of 2.0 cm^-1 and left to soak for predefined periods of time. The concentration of the solution in contact with the coated samples were then analyzed via inductively coupled plasma mass spectrometry, and the data used to determine the extent to which the coatings provided a barrier to silver loss. This paper summarizes the coating selection process, the configuration of the test, and the performance of each coating-metal combination as a mitigation to silver depletion. The preliminary results demonstrate that select coatings are proving effective at maintaining biocidal silver concentrations. The knowledge acquired through this investigation will be used to assess the feasibility of using these coatings as a robust strategy for maintaining biocidal silver in the water systems. Future studies are planned to assess the specific use of these coatings and to better understand the implications of utilizing this material approach in the future spacecraft potable water system designs.

coatings↗
NASA NTRS2015

Microencapsulation Technologies for Corrosion Protective Coating Applications

Microencapsulation technologies for functional smart Coatings for autonomous corrosion control have been a research area of strong emphasis during the last decade. This work concerns the development of pH sensitive micro-containers (microparticles and microcapsules) for autonomous corrosion control. This paper presents an overview of the state-of-the-art in the field of microencapsulation for corrosion control applications, as well as the technical details of the pH sensitive microcontainer approach, such as selection criteria for corrosion indicators and corrosion inhibitors; the development and optimization of encapsulation methods; function evaluation before and after incorporation of the microcontainers into coatings; and further optimization to improve coating compatibility and performance.

Microencapsulation↗
NASA NTRS1988

High resolution video monitoring of coating thickness during plasma spraying

A new approach to monitoring the thickness of plasma sprayed coatings during application is described. The method employs a high resolution video camera and width analyzer to accurately measure the dimensions of samples having simple geometries. This approach is best suited for cylindrical or flat substrates but it may also work for selected locations on more complex geometries. Measurement accuracy is a function of specimen dimensions and extent of magnification. Tolerances of plus or minus 0.5 mil (0.13 mm) on final coating thickness can be achieved. Additionally, the plot of cumulative coating thickess versus the number of passes has proven to be a useful diagnostic tool. While the ideal plot is linear, strong deviations from linearity - indicating the need for corrective action - may be observed.

Miller, Robert A.↗
NASA NTRS2011

Spacesuit Soft Upper Torso Sizing Systems

The passive sizing system consists of a series of low-profile pulleys attached to the front and back of the shoulder bearings on a spacesuit soft upper torso (SUT), textile cord or stainless steel cable, and a modified commercial ratchet mechanism. The cord/cable is routed through the pulleys and attached to the ratchet mechanism mounted on the front of the spacesuit within reach of the suited subject. Upon actuating the ratchet mechanism, the shoulder bearing breadth is changed, providing variable upper torso sizing. The active system consists of a series of pressurizable nastic cells embedded into the fabric layers of a spacesuit SUT. These cells are integrated to the front and back of the SUT and are connected to an air source with a variable regulator. When inflated, the nastic cells provide a change in the overall shoulder bearing breadth of the spacesuit and thus, torso sizing. The research focused on the development of a high-performance sizing and actuation system. This technology has application as a suit-sizing mechanism to allow easier suit entry and more accurate suit fit with fewer torso sizes than the existing EMU (Extravehicular Mobility Unit) suit system. This advanced SUT will support NASA s Advanced EMU Evolutionary Concept of a two-sizes-fit-all upper torso for replacement of the current EMU hard upper torso (HUT). Both the passive and nastic sizing system approaches provide astronauts with real-time upper torso sizing, which translates into a more comfortable suit, providing enhanced fit resulting in improved crewmember performance during extravehicular activity. These systems will also benefit NASA by reducing flight logistics as well as overall suit system cost. The nastic sizing system approach provides additional structural redundancy over existing SUT designs by embedding additional coated fabric and uncoated fabric layers. Two sizing systems were selected to build into a prototype SUT: one active and one passive. From manned testing, it was found that both systems offer good solutions to sizing a SUT to fit a crewmember. This new system provided improved suit don/doff over existing spacesuit designs as well as providing better fit at suit operational pressure resulting in improved comfort and mobility. It was found that a SUT with a sizing system may solve several problems that have plagued existing HUT designs, and that a SUT with a sizing system may be a viable option for advanced suit architectures.

Graziosi, David↗