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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Densification and properties of alpha-silicon carbide

The sintering behavior of alpha-SiC with B and C sintering aids and without sintering aids was investigated experimentally. The sintering was performed for 30-60 min in argon flow at 2150 and 2200 C. The density of the sintered bars was determined by weighing and measuring the bars, four-point flexure tests were conducted on machined bars, and the Weibull modulus was determined by regression analysis. It is found that type 1 alpha-SiC powder, which does not densify, can be sintered to a high final density (in excess of 96 percent of the theoretical value) using B and C sintering aids. Flexure test results and Weibull modulus data suggest that the strength of the alpha-SiC ceramic is greatly affected by processing flaws and also by inclusions and machining flaws.

Dutta, S.↗
NASA NTRS1993

Monolithic catalytic igniters

Catalytic igniters offer the potential for excellent reliability and simplicity for use with the diergolic bipropellant oxygen/hydrogen as well as with the monopropellant hydrazine. State-of-the-art catalyst beds - noble metal/granular pellet carriers - currently used in hydrazine engines are limited by carrier stability, which limits the hot-fire temperature, and by poor thermal response due to the large thermal mass. Moreover, questions remain with regard to longevity and reliability of these catalysts. In this work, Ultramet investigated the feasibility of fabricating monolithic catalyst beds that overcome the limitations of current catalytic igniters via a combination of chemical vapor deposition (CVD) iridium coatings and chemical vapor infiltration (CVI) refractory ceramic foams. It was found that under all flow conditions and O2:H2 mass ratios tested, a high surface area monolithic bed outperformed a Shell 405 bed. Additionally, it was found that monolithic catalytic igniters, specifically porous ceramic foams fabricated by CVD/CVI processing, can be fabricated whose catalytic performance is better than Shell 405 and with significantly lower flow restriction, from materials that can operate at 2000 C or higher.

La Ferla, R.↗
NASA NTRS2002

Bn and Si-Doped Bn Coatings on Woven Fabrics

A computer controlled, pulsed chemical vapor infiltration (CVI) system has been developed to deposit BN from a liquid borazine (B3N3H6) source, as well as silicon doped BN coatings using borazine and a silicon source, into 2-D woven ceramic fabric preforms. The coating process was evaluated as a function of deposition temperature, pressure, and precursor flow rate. Coatings were characterized by field emission scanning electron microscopy, electron dispersive spectroscopy and Auger spectroscopy. By controlling the reactant feed ratios, Si incorporation could be controlled over the range of 6-24 atomic percent.

Hurwitz, Frances I.↗
NASA NTRS2003

Impact of Defect Distributions on the Reliability of Structural Materials

The purpose of this study is to develop a probabilistic model to estimate the fatigue life of gas turbine disks made of powder superalloy metals. Such metals are known to have high strength and ductility under extremely high temperatures and known to have high fatigue lives. However, despite the high quality controls instituted during metal processing, sufficiently high numbers of ceramic inclusions materialize within the metal matrix creating weak links that lead to reduced fatigue lives. To study the effect of such ceramic inclusions on the fatigue life of gas turbine disks, an experimental program has been initiated at the NASA Glenn Research. In this phase of the study, a statistical analysis of the test results is undertaken which served as the basis of the probabilistic simulation model. The study is a part of the Crack Resistant Disk Materials task within the Ultra Safe Propulsion Project.

Ghosn, Michel J.↗
NASA NTRS2009

Synthesis, Decomposition and Characterization of Fe and Ni Sulfides and Fe and CO Nanoparticles for Aerospace Applications

We describe several related studies where simple iron, nickel, and cobalt complexes were prepared, decomposed, and characterized for aeronautics (Fischer-Tropsch catalysts) and space (high-fidelity lunar regolith simulant additives) applications. We describe the synthesis and decomposition of several new nickel dithiocarbamate complexes. Decomposition resulted in a somewhat complicated product mix with NiS predominating. The thermogravimetric analysis of fifteen tris(diorganodithiocarbamato)iron(III) has been investigated. Each undergoes substantial mass loss upon pyrolysis in a nitrogen atmosphere between 195 and 370 C, with major mass losses occurring between 279 and 324 C. Steric repulsion between organic substituents generally decreased the decomposition temperature. The product of the pyrolysis was not well defined, but usually consistent with being either FeS or Fe2S3 or a combination of these. Iron nanoparticles were grown in a silica matrix with a long-term goal of introducing native iron into a commercial lunar dust simulant in order to more closely simulate actual lunar regolith. This was also one goal of the iron and nickel sulfide studies. Finally, cobalt nanoparticle synthesis is being studied in order to develop alternatives to crude processing of cobalt salts with ceramic supports for Fischer-Tropsch synthesis.

Cowen, Jonathan E.↗
NASA NTRSDate not supplied

Voltage-Controlled Differential Faraday Rotation from FMNWs and Magnetoelastic Silicone-Nickel Composites

Differential Faraday rotation has been observed from strain-Differential Faraday rotation has been observed from strain-modulated magnetoelastic membranes using millimeter-wave polarimetry at 61.25 GHz. The membranes, consisting of aligned chains of nickel micro-particles embedded in silicone rubber, were manufactured using a roll-to-roll electromagnetic processing line, mounted onto piezoelectric ceramic annuli, and immersed in externally-generated static magnetic fields. Experiments were conducted in which the membranes were periodically stretched by operating the piezoelectric crystals close to their radial resonant frequencies—thereby modulating nickel particle density as well as magnetic material properties. A customized quasi-optical apparatus was used to determine the Faraday-rotation difference between the strained and unstrained states of the magnetoelastic membranes. Possible applications that could emerge from this polymer-based technology include nonreciprocal millimeter-wave components with voltage-controlled frequency response and bio-inspired geomagnetic sensors for GPS-denied navigation. Investigations were conducted to estimate the maximum attainable differential Faraday rotation and the minimum detectable static magnetic field.

nickel↗
DOE OSTI2016

Tribological synthesis method for producing low-friction surface film coating

An article of method of manufacture of a low friction tribological film on a substrate. The article includes a substrate of a steel or ceramic which has been tribologically processed with a lubricant containing selected additives and the additives, temperature, load and time of processing can be selectively controlled to bias formation of a film on the substrate where the film is an amorphous structure exhibiting highly advantageous low friction properties.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Method of making dielectric capacitors with increased dielectric breakdown strength

The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Efficient Silicon Carbide (SiC) Fiber Manufacture: Continuous Processing of Novel Precursors via Modified Material Handling

General Atomics Electromagnetic Systems (GA-EMS) together with The Nonwovens Institute (NWI) and Harper International have executed on a development project to improve the production efficiency and reduce the production cost of silicon carbide (SiC) fiber – a critical material that advances US energy security and aerospace leadership. In the first budget period (BP1), the modified tow throughput (MTT) apparatus was developed, enabling fiber spinning in the form of loose coils rather than tightly packed spools (Figure 1) for batch processing of SiC fiber. This coil-based approach was proven to be capable of uniform fiber crosslinking and ceramic conversion, as well as demonstrating key process efficiencies while meeting the program fiber property targets.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Additive manufacturing of ceramic materials for energy applications: Road map and opportunities

Among engineering materials, ceramics are indispensable in energy applications such as batteries, capacitors, solar cells, smart glass, fuel cells and electrolyzers, nuclear power plants, thermoelectrics, thermoionics, carbon capture and storage, control of harmful emission from combustion engines, piezoelectrics, turbines and heat exchangers, among others. Advances in additive manufacturing (AM) offer new opportunities to fabricate these devices in geometries unachievable previously and may provide higher efficiencies and performance, all at lower costs. This article reviews the state of the art in ceramic materials for various energy applications. The focus of the review is on material selections, processing, and opportunities for AM technologies in energy related ceramic materials manufacturing. The aim of the article is to provide a roadmap for stakeholders such as industry, academia and funding agencies on research and development in additive manufacturing of ceramic materials toward more efficient, cost-effective, and reliable energy systems.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Siloxanes, silanes, and silazanes in the preparation of ceramics and glasses

The use of selected organosilicon compounds for the preparation of silicon based ceramic materials is discussed in terms of processing microstructure-property relationships. The mechanisms operative in the formation of gel derived silicate glasses and glass ceramics are reasonably well understood, but this is not true for silicon carbide/nitride based ceramics. The properties of organosilicon precursors and the mechanism of pyrolysis affect the microstructural features of the ceramic. Reaction mechanisms are proposed and the microstructural features and properties of organosilazane derived ceramics discussed.

Wills, R. R.↗
NASA NTRS1991

Lightweight ceramic components for propulsion applications

It is demonstrated that two ceramic engine components of reduced weight can be efficiently produced and employed at higher combustion gas temperatures. The engine components, containing internal cooling and hydraulic passages, are fabricated in a process involving platelet technology, tape casting, and multilayer ceramic packaging techniques. Traditional metal platelet design techniques are used to fabricate components from ceramic tape which are then laminated and processed to densities of close to 100 percent. A methane cooled regenerator for an air turbo ramjet engine and a rocket engine bipropellant injector are fabricated from silicon nitride. The two components are tested under conditions similar to the pressurization, thrusts, and temperatures encountered in a combustion gas environment. The survivability and leak-free nature of the components demonstrate that more complex ceramic engine components can be fabricated using these techniques.

Franklin, J. E.↗
NASA NTRS1999

Phoretic Force Measurement for Microparticles Under Microgravity Conditions

This theoretical and experimental investigation of the collisional interactions between gas molecules and solid and liquid surfaces of microparticles involves fundamental studies of the transfer of energy, mass and momentum between gas molecules and surfaces. The numerous applications include particle deposition on semiconductor surfaces and on surfaces in combustion processes, containerless processing, the production of nanophase materials, pigments and ceramic precursors, and pollution abatement technologies such as desulfurization of gaseous effluents from combustion processes. Of particular emphasis are the forces exerted on microparticles present in a nonuniform gas, that is, in gaseous surroundings involving temperature and concentration gradients. These so-called phoretic forces become the dominant forces when the gravitational force is diminished, and they are strongly dependent on the momentum transfer between gas molecules and the surface. The momentum transfer, in turn, depends on the gas and particle properties and the mean free path and kinetic energy of the gas molecules. The experimental program involves the particle levitation system shown. A micrometer size particle is held between two heat exchangers enclosed in a vacuum chamber by means of ac and dc electric fields. The ac field keeps the particle centered on the vertical axis of the chamber, and the dc field balances the gravitational force and the thermophoretic force. Some measurements of the thermophoretic force are presented in this paper.

Davis, E. J.↗
NASA NTRS1982

Fibrous ceramic insulation

Some of the reusable heat shielding materials used to protect the Space Shuttles, their manufacturing processes, properties, and applications are discussed. Emphases is upon ceramic materials. Space Shuttle Orbiter tiles are discussed.

Howard E. Goldstein↗
DOE OSTI2016

Nd:AlN polycrystalline ceramics: A candidate media for tunable, high energy, near IR lasers

We present processing and characterization of Nd-doped aluminum nitride (Nd:AlN) polycrystalline ceramics. We compare ceramics with significant segregation of Nd to those exhibiting minimal segregation. Spatially resolved photoluminescence maps reveal a strong correlation between homogeneous Nd doping and spatially homogeneous light emission. The spectroscopically resolved light emission lines show excellent agreement with the expected Nd electronic transitions. Notably, the lines are significantly broadened, producing near IR emission (~1077 nm) with a remarkable ~100 nm bandwidth at room temperature. We attribute the broadened lines to a combination of effects: multiple Nd-sites, anisotropy of AlN and phonon broadening. These broadened, overlapping lines in a media with excellent thermal conductivity have potential for Nd-based, tunable lasers with high average power.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Thermal-Mechanical Analysis of an Additive Manufacturing Ceramic Heat Exchanger for High-Temperature Recuperator in a sCO2 Power System

Supercritical CO2 (sCO2) Brayton power cycle can be configured in a closed-loop power system and has a potentially high cycle efficiency. Compactness and high efficiency of a sCO2 power block make the sCO2 Brayton cycle a versatile power cycle in broad applications. While many heat sources are of sufficient intensity to produce high temperature working fluids to achieve high cycle efficiency, the thermal-mechanical stability of traditional materials (e.g., steels and nickel-based superalloys) used in construction of heat exchangers and turbine components limits the operating conditions and thus thermodynamic efficiency of the system. This effort seeks to establish the viability of ceramic heat exchanger technologies for the most extreme operating conditions envisioned for power generation and other high temperature processes. Heat exchangers constructed from ultra-high temperature ceramics, a class of extreme environment materials featuring melting points (Tmp.) above 3000 degrees C, is particularly appealing for sCO2 Brayton cycles given their ultra-low creep rates and very high retained strength at low homologous temperatures (i.e., T < 0.5 Tmp., or at least 1500 degrees C). To translate these materials properties to ultra-high temperature heat exchangers, innovations are required in ceramic manufacturing techniques to realize the complex architectures featured in compact heat exchangers with high power density. With appropriate processing, ZrB2-SiC based compositions can be sintered to near full density and shaped into complex topologies via ceramic additive manufacturing methods. This paper analyzes heat exchanger designs and explores thermal-mechanical implications of the operating environment. Thermal flow, heat transfer, and conjugate mechanical analyses provide insights into benefits and risks associated with the design approach.

additive manufacturing↗
DOE OSTI2022

Particle Migration in Large Cross-Section Ceramic On-Demand Extrusion Components

Ceramic On-Demand Extrusion (CODE) is a direct ink writing process which allows for the creation of near theoretically dense ceramic components with large cross-sections due to oil-assisted drying. Here, Yttria-stabilized zirconia (YSZ) colloidal pastes were used in CODE to produce dense (multi-road infill and ≳ 98% relative density), large continuous volume (> 1 cm 3 ), and high fidelity (nozzle diameters ≲ 1 mm) structural ceramic components with nanoparticle feedstocks (~d 50 ≲ 1 µm). However, many of these printed components underwent significant particle migration after forming. The reason for this particle migration defect was investigated using the coffee-ring effect for dilute solutions and rheological methods for dense suspensions. Modifications to the colloidal paste, such as changes in solids loading, pH, or surfactant concentration were explored as to their effectiveness to mitigate the defect. Ultimately, paste formulation and printing trade-offs are discussed with respect to the post-printing defect and as to general direct-write patterning.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Final Crada Report For CR-13-004 Between SRNS And Tetramer Technologies

During this CRADA, processing technology was developed to apply a fluorescent coating to Ceramic Seals which had sufficient luminescence to be visibly detected. The processes developed were effective for the application of highly fluorescent coatings and the coatings were compatible with LSA unique ID examination. A handheld reader was developed which can work in conjunction with existing handheld reader designs and provided a method for the determination of the authenticity of the applied fluorescent coatings.

36 MATERIALS SCIENCE↗