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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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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Moderate temperature sintering of BaZr 0.8 Y 0.2 O 3-δ protonic ceramics by A novel cold sintering pretreatment

The state-of-the-art protonic ceramic conductor BaZr 0.8 Y 0.2 O 3-δ (BZY20) requires an extremely high sintering temperature (≥1700 °C) to achieve the desired relative density and microstructure necessary to function as a proton conducting electrolyte. In this work, we developed a cold sintering pretreatment assisted moderate-temperature sintering method for the fabrication of high-quality pure BZY20 pellets. BZY20 pellets with high relative density of ~94% were fabricated with a final sintering temperature of 1500 °C (200 °C lower than the traditional sintering temperature). A comparison with BZY20 control samples indicated that the proper amount of BaCO 3 introduced on the BZY20 particle surface and the high green density achieved by cold sintering pretreatment were the main drivers for lowering the sintering temperature. The electrical conductivity measurement by electrochemical impedance spectroscopy showed that the as-prepared BZY20 pellets have a proton conductivity comparable to the state-of-the-art values. The cold sintering pretreatment outlined in this work has the potential to lower the sintering temperatures for similar types of protonic ceramic materials under consideration for a wide range of energy conversion and storage applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Exploitation of Defects in High Entropy Ceramic Barrier Materials

A critical mission need exists to develop new materials that can withstand extreme environments and multiple sequential threats. High entropy materials, those containing 5 or more metals, exhibit many exciting properties which would potentially be useful in such situations. However, a particularly hard challenge in developing new high entropy materials is determining a priori which compositions will form the desired single phase material. The project outlined here combined several modeling and experimental techniques to explore several structure-property-relationships of high entropy ceramics in an effort to better understand the connection between their compositional components, their observed properties, and stability. We have developed novel machine learning algorithms which rapidly predict stable high entropy ceramic compositions, identified the stability interplay between configurational entropy and cation defects, and tested the mechanical stability of high entropy oxides using the unique capabilities at the Dynamic Compression Sector facility and the Saturn accelerator.

36 MATERIALS SCIENCE↗
NASA NTRS1982

Development of high strength, high temperature ceramics

Improvement in the high-pressure turbopumps, both fuel and oxidizer, in the Space Shuttle main engine were considered. The operation of these pumps is limited by temperature restrictions of the metallic components used in these pumps. Ceramic materials that retain strength at high temperatures and appear to be promising candidates for use as turbine blades and impellers are discussed. These high strength materials are sensitive to many related processing parameters such as impurities, sintering aids, reaction aids, particle size, processing temperature, and post thermal treatment. The specific objectives of the study were to: (1) identify and define the processing parameters that affect the properties of Si3N4 ceramic materials, (2) design and assembly equipment required for processing high strength ceramics, (3) design and assemble test apparatus for evaluating the high temperature properties of Si3N4, and (4) conduct a research program of manufacturing and evaluating Si3N4 materials as applicable to rocket engine applications.

Hall, W. B.↗
DOE OSTI2021

The influence of stacking faults on mechanical behavior of advanced materials

We report there are abundant studies on deformation mechanisms in metallic materials dominated by grain boundaries and twin boundaries. In comparison, the influence of stacking faults on deformation mechanisms of materials remains less well understood. Recent studies have shown that when the density of stacking faults increases sharply, their influence on mechanical behavior of metallic or ceramic materials becomes prominent, and in fact, dominates in some cases. This article reviews recent research progress on how nanoscale stacking faults impact the mechanical behavior of metallic and ceramic materials. We primarily focus on studies that reveal the formation of pre-existing stacking faults, their interactions with dislocations, and phase transformations during plastic deformation as evidenced by experiments and simulations. The aim of this review is to highlight the potential opportunities in using stacking faults to tailor the deformation mechanisms of advanced materials.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Corrosion of SiC by Molten Salt

Advanced ceramic materials considered for wide range of applications as in gas turbine engines and heat exchangers. In such applications, materials may be in corrosive environments that include molten salts. Very corrosive to alloys. In order to determine extent of problem for ceramic materials, corrosion of SiC by molten salts studied in both jet fuel burners and laboratory furnaces. Surface of silicon carbide corroded by exposure to flame seeded with 4 parts per million of sodium. Strength of silicon carbide decreased by corrosion in flame and tube-furnace tests.

Jacobson, Nathan S.↗
NASA NTRS1993

Improved ceramic slip casting technique

A primary concern in modern fluid dynamics research is the experimental verification of computational aerothermodynamic codes. This research requires high precision and detail in the test model employed. Ceramic materials are used for these models because of their low heat conductivity and their survivability at high temperatures. To fabricate such models, slip casting techniques were developed to provide net-form, precision casting capability for high-purity ceramic materials in aqueous solutions. In previous slip casting techniques, block, or flask molds made of plaster-of-paris were used to draw liquid from the slip material. Upon setting, parts were removed from the flask mold and cured in a kiln at high temperatures. Casting detail was usually limited with this technique -- detailed parts were frequently damaged upon separation from the flask mold, as the molded parts are extremely delicate in the uncured state, and the flask mold is inflexible. Ceramic surfaces were also marred by 'parting lines' caused by mold separation. This adversely affected the aerodynamic surface quality of the model as well. (Parting lines are invariably necessary on or near the leading edges of wings, nosetips, and fins for mold separation. These areas are also critical for flow boundary layer control.) Parting agents used in the casting process also affected surface quality. These agents eventually soaked into the mold, the model, or flaked off when releasing the case model. Different materials were tried, such as oils, paraffin, and even an algae. The algae released best, but some of it remained on the model and imparted an uneven texture and discoloration on the model surface when cured. According to the present invention, a wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell mold of the calcium sulfate-bonded investment material. The shell mold is cooled to room temperature, and a ceramic slip is poured therein. After a ceramic shell of desired thickness has set up in the shell mold, excess ceramic slip is poured out. While still wet, the shell mold is peeled from the ceramic shell to expose any delicate or detailed parts, after which the ceramic shell is cured to provide a complete, detailed, precision ceramic article without parting lines.

Buck, Gregory M.↗
NASA NTRS1982

Structural application of high strength, high temperature ceramics

The operation of rocket engine turbine pumps is limited by the temperature restrictions of metallic components used in the systems. Mechanical strength and stability of these metallic components decrease drastically at elevated temperatures. Ceramic materials that retain high strength at high temperatures appear to be a feasible alternate material for use in the hot end of the turbopumps. This project identified and defined the processing parameters that affected the properties of Si3N4, one of candidate ceramic materials. Apparatus was assembled and put into operation to hot press Si3N4 powders into bulk material for in house evaluation. A work statement was completed to seek outside contract services to design, manufacture, and evaluate Si3N4 components in the service environments that exists in SSME turbopumps.

Hall, W. B.↗
NASA NTRS1988

Hot corrosion of ceramic engine materials

A number of commercially available SiC and Si3N4 materials were exposed to 1000 C in a high velocity, pressurized burner rig as a simulation of a turbine engine environment. Sodium impurities added to the burner flame resulted in molten Na2SO4 deposition, attack of the SiC and Si4N4 and formation of substantial Na2O-x(SiO2) corrosion product. Room temperature strength of the materials decreased. This was a result of the formation of corrosion pits in SiC, and grain boundary dissolution and pitting in Si3N4. Corrosion regimes for such Si-based ceramics have been predicted using thermodynamics and verified in rig tests of SiO2 coupons. Protective mullite coatings are being investigated as a solution to the corrosion problem for SiC and Si3N4. Limited corrosion occurred to cordierite (Mg2Al4Si5O18) but some cracking of the substrate occurred.

Fox, Dennis S.↗
DOE OSTI2022

Fabrication and analysis of hydroxide/ceramic dual-phase (HCDP) membranes

Ceramic materials show potential to serve as support structures for membranes that can be used to uptake carbon dioxide from high temperature environments, like those found in nuclear flue plants. The porosity of ceramic materials allows for the infilling of those pores with molten hydroxides, that show a natural affinity for absorbing CO 2 from its surroundings. The membranes are easy to produce and were made with thickness of 0.5mm, 1.0mm, and 2.0mm. The membranes were exposed to various conditions after the infilling process and their responses were measured. The percent of hydroxides were measured after the infilled membranes had been in a tube furnace at 400°C, followed by exposure to 30 minutes of CO 2 , and lastly 4 hours of steam. Those tests yielded mole percent hydroxide results of 88.4% ± 4.6%, 68.6% ± 5.1%, and 80.7% ± 4.6%, respectively.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Design and aerodynamic performance evaluation of a high-work mixed flow turbine stage

As axial and radial turbine designs have been pushed to their aerothermodynamic and mechanical limits, the mixed-flow turbine (MFT) concept has been projected to offer performance and durability improvements, especially when ceramic materials are considered. The objective of this NASA/U.S. Army sponsored mixed-flow turbine (AMFT) program was to determine the level of performance attainable with MFT technology within the mechanical constraints of 1997 projected ceramic material properties. The MFT geometry is similar to a radial turbine, exhibiting a large radius change from inlet to exit, but differing in that the inlet flowpath is not purely radial, nor axial, but mixed; it is the inlet geometry that gives rise to the name 'mixed-flow'. The 'mixed' orientation of the turbine inlet offers several advantages over radial designs by allowing a nonzero inlet blade angle yet maintaining radial-element blades. The oblique inlet not only improves the particle-impact survivability of the design, but improves the aerodynamic performance by reducing the incidence at the blade inlet. The difficulty, however, of using mixed-flow geometry lies in the scarcity of detailed data and documented design experience. This paper reports the design of a MFT stage designed with the intent to maximize aerodynamic performance by optimizing design parameters such as stage reaction, rotor incidence, flowpath shape, blade shape, vane geometry, and airfoil counts using 2-D, 3-D inviscid, and 3-D viscous computational fluid dynamics code. The aerodynamic optimization was accomplished while maintaining mechanical integrity with respect to vibration and stress levels in the rotor. A full-scale cold-flow rig test was performed with metallic hardware fabricated to the specifications of the hot ceramic geometry to evaluate the stage performance.

Neri, Remo N.↗
DOE OSTI2025

Validation of a Custom Ball-on-Ring Apparatus and Consideration of Common Issues for Use in Further Testing (SULI Deliverables)

Ceramic materials are well-known for their high hardness and strength but are limited in their application due to low toughness and sudden failure. As a potential solution, inspiration can be taken from dental enamel nanostructure, where undulating rods cause cracks to branch or deflect, increasing the energy needed to cause total fracture of a ceramic part. Following the dental enamel structure, a novel ceramic which uses 3D printed Yttria stabilized Zirconia rods in an alumina matrix was developed. To test this bio-inspired ceramic material, a proper testing apparatus needed to be created and tested to verify its accuracy. For this project, a bespoke ball on ring testing apparatus was created and tested using both conventionally sintered alumina disks and purchased alumina disks to validate its accuracy. By comparing the Weibull distribution of rupture strengths measured by the tests to literature values, it was shown that the testing frame had a wide distribution of strength which did not align with literature values on the lower end. Through fractography, it was found that some samples fractured from the contact stress induced by the ball indenter, which could not be used to calculate rupture strength. This fracture was often linked to low stress to failure, which was initiated by a flaw on the surface near the indenter which acted as a stress concentrator. Removal of these samples from the data set increased the accuracy of the reported rupture strength values for the ceramic. Considering the equations for the magnitude of contact and flexural strength, along with observations of initiating flaws, several measures can be taken for testing the bio-inspired composite. These measures include proper polishing of both sides of the sample, reducing sample thickness, and potentially using a softer indenter material.

36 - MATERIALS SCIENCE↗
NASA NTRS1979

Plasma-sprayed zirconia gas path seal technology: A state-of-the-art review

The benefits derived from application of ceramic materials to high pressure turbine gas path seal components are described and the developmental backgrounds of various approaches are reviewed. The most fully developed approaches are those employing plasma sprayed zirconium oxide as the ceramic material. Prevention of cracking and spalling of the zirconium oxide under cyclic thermal shock conditions imposed by the engine operating cycle is the most immediate problem to be solved before implementation is undertaken. Three promising approaches to improving cyclic thermal shock resistance are described and comparative rig performance of each are reviewed. Advanced concepts showing potential for performance improvements are described.

Bill, R. C.↗
DOE OSTI2024

Development of Additive Manufacturing for Ceramic Matrix Composite Vanes

This report discusses the development of additive manufacturing for polymer-derived ceramic materials to create novel cooled gas turbine airfoils made from ceramics. Gas turbine engines have extremely high temperatures in the hot section of the engine that exceed the melting point of nickel superalloy materials that the engine is made from. Advanced cooling technologies have been developed over decades for metallic parts. Ceramic materials have higher temperature capabilities than superalloys, but are difficult to shape in the complex designs used in modern turbines. Several thrusts were investigated during the project, including development of higher material strength resins, improvement of ultraviolet (UV) photopolymerization and post-processing techniques to increase survivability of ceramic parts, thermomechanical modeling of novel ceramic airfoil designs for higher cooling effectiveness, and experimental validation of the modeling and manufacturing in a turbine vane test facility at nondimensional conditions that are relevant to modern gas turbines. Some major findings of the work include a significant increase in ceramic survivability during pyrolysis (a high temperature process that converts the organic material to a ceramic) by adjusting the composition ratios of the resins, as well as a tolulene soak after printing to remove unreacted polymer material. Thermomechanical optimization of the internal cooling structure indicated that a high density pin fin array would enable an 80% increase in overall cooling effectiveness relative to a baseline geometry, which was later verified during experimental testing in a high speed linear cascade. Ceramic vanes were tested at Mach numbers of up to 0.9 which is relevant to modern gas turbines. High temperature capability of the ceramic vanes was not tested in this work.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Design and development of ceramic components

The development of the AGT 100 turbine components in structural ceramic materials is described. Development is defined as the complete and iterative cycle from design, analysis, test, and design refinement culminating in successful demonstration of the design requirements. The components are analyzed by a linear elastic probabilistic approach, which involves finite element (three- and/or two-dimensional) simulation of the component combined with a Weibull characterization of the brittle ceramic material strength distribution to calculate a probability of survival for the component in the operating environment. Component test failure investigation has resulted in design modifications, and an improvement in component reliability has been demonstrated. Engine testing (over 570 h to date) continues to assess design/development of structural ceramic components.

Holtman, R. L.↗
NASA NTRS2001

The Low Pressure Gas Effects On The Potency Of An Electron Beam On Ceramic Fabric Materials For Space Welding

This investigation was undertaken to evaluate if molten metal or electron beam impingement could damage or burn through the fabric of the astronauts Extravehicular Mobility Unit (EMU) during electron beam welding exercises performed in space. An 8 kilovolt electron beam with a current in the neighborhood of 100 milliamps from the Ukrainian space welding "Universal Hand Tool" burned holes in Nextel AF-62 ceramic cloth designed to withstand temperatures up to 1427 C. The burnthrough time was on the order of 8 seconds at standoff distances between UHT and cloth ranging from 6 to 24 inches. At both closer (2") and farther (48") standoff distances the potency of the beam against the cloth declined and the burnthrough time went up significantly. Prior to the test it had been expected that the beam would lay down a static charge on the cloth and be deflected without damaging the cloth. The burnthrough is thought to be an effect of partial transmission of beam power by a stream of positive ions generated by the high voltage electron beam from contaminant gas in the "vacuum" chamber. A rough quantitative theoretical computation appears to substantiate this possibility.

Nunes, Arthur C., Jr.↗
NASA NTRS1980

Ceramic regenerator systems development program

The DOE/NASA Ceramic Regenerator Design and Reliability Program aims to develop ceramic regenerator cores that can be used in passenger car and industrial/truck gas turbine engines. The major cause of failure of early gas turbine regenerators was found to be chemical attack of the ceramic material. Improved materials and design concepts aimed at reducing or eliminating chemical attack were placed on durability test in Ford 707 industrial gas turbine engines late in 1974. Results of 53,065 hours of turbine engine durability testing are described. Two materials, aluminum silicate and magnesium aluminum silicate, show promise. Five aluminum silicate cores attained the durability objective of 10,000 hours at 800 C (1472 F). Another aluminum silicate core shows minimal evidence of chemical attack after 8071 hours at 982 C (1800 F). Results obtained in ceramic material screening tests, aerothermodynamic performance tests, stress analysis, cost studies, and material specifications are included.

Fucinari, C. A.↗
NASA NTRS1995

Ceramic Replaces Metal In High Performance Optomechanical Structures

Recently developed ceramic materials and fabrication techniques integrated by Langley Research Center workers to produce superior optomechanical structures for spacecraft and aircraft instrumentation. Basic features of these novel supports, such as dimensional stability, low cost, and ease of fabrication, also make them ideal for many commerical optical systems as well. Ceramic supports for optical components and benches offer important advantages over usual metal parts. Ceramic materials expand and contract only slightly with changes in temperature. Moreover, they are relatively inexpensive and lightweight.

Vasquez, Peter↗