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At least 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Advanced Gasification and Novel Transformational Coal Conversion Technologies Development: Final Technical Report

This report summarizes the work carried out in furtherance of the NETL/DOE award, OTM-Enhanced Coal Syngas for Carbon Capture Power Systems and Fuel Synthesis Applications. The overall objective of the project was to further develop Oxygen Transport Membrane (OTM) technology and assess the potential for integration in coal power generation. OTM technology has the potential to enhance the quality of syngas produced by coal gasifiers, reduce the amount of cryogenic-derived oxygen required in Integrated Gasification Combined Cycle (IGCC) power plants, and allow for coal and natural gas integration. Process simulations and techno-economic analyses were carried out to estimate the cost and performance of OTM enhanced IGCC plants, IG-NGCC plants, and OTM enhanced Fischer Tropsch (FT) Liquids from coal and natural gas plants. The OTM enhanced power plants achieved higher carbon capture rates, higher efficiencies, and lower cost of electricity compared to the base cases. The most significant benefits were achieved for cases which used low rank coal as the feed. Fischer-Tropsch coal to liquids plants with iron-based catalysts and natural gas integration utilizing OTM technology showed improved carbon conversion, improved thermal efficiency and lower cost of production. With respect to OTM core technology development, significant advances have been made in several areas. The development and implementation of a third-generation membrane materials and manufacturing process has resulted in the availability of robust and reliable, high performance membranes, that can be manufactured at high yield. Progress towards the goal of higher pressure operation has been demonstrated with the development of improved metal-ceramic seals and components of the panel array module that integrate membrane-seal assemblies with primary and secondary reforming catalysts have been further developed and demonstrated. Work concluded with the successful start-up and operation of a multi-panel pilot-scale system which is the final step in technology development ahead of demonstration.

20 FOSSIL-FUELED POWER PLANTS↗
NASA NTRS1984

Subcritical crack growth and other time- and environment-dependent behavior in crustal rocks

Stable crack growth strongly influences both the fracture strength of brittle rocks and some of the phenomena precursory to catastrophic failure. Quantification of the time and environment dependence of fracture propagation is attempted with the use of a fracture mechanics technique. Some of the difficulties encountered when applying techniques originally developed for simple synthetic materials to complex materials like rocks are examined. A picture of subcritical fracture propagation is developed that embraces the essential ingredients of the microstructure, a microcrack process zone, and the different roles that the environment plays. To do this, the results of (1) fracture mechanics experiments on five rock types, (2) optical and scanning electron microscopy, (3) studies of microstructural aspects of fracture in ceramics, and (4) exploratory tests examining the time-dependent response of rock to the application of water are examined.

Swanson, P. L.↗
NASA NTRS1992

Nondestructive evaluation of ceramic and metal matrix composites for NASA's HITEMP and enabling propulsion materials programs

In a preliminary study, ultrasonic, x-ray opaque, and fluorescent dye penetrants techniques were used to evaluate and characterize ceramic and metal matrix composites. Techniques are highlighted for identifying porosity, fiber alignment, fiber uniformity, matrix cracks, fiber fractures, unbonds or disbonds between laminae, and fiber-to-matrix bond variations. The nondestructive evaluations (NDE) were performed during processing and after thermomechanical testing. Specific examples are given for Si3N4/SiC (SCS-6 fiber), FeCrAlY/Al2O3 fibers, Ti-15-3/SiC (SCS-6 fiber) materials, and Si3N4/SiC (SCS-6 fiber) actively cooled panel components. Results of this study indicate that the choice of the NDE tools to be used can be optimized to yield a faithful and accurate evaluation of advanced composites.

Generazio, Edward R.↗
NASA NTRS2000

Silicon-Based Ceramic-Matrix Composites for Advanced Turbine Engines: Some Degradation Issues

SiC/BN/SiC composites are designed to take advantage of the high specific strengths and moduli of non-oxide ceramics, and their excellent resistance to creep, chemical attack, and oxidation, while circumventing the brittleness inherent in ceramics. Hence, these composites have the potential to take turbine engines of the future to higher operating temperatures than is achievable with metal alloys. However, these composites remain developmental and more work needs to be done to optimize processing techniques. This paper highlights the lingering issue of pest degradation in these materials and shows that it results from vestiges of processing steps and can thus be minimized or eliminated.

Thomas-Ogbuji, Linus U. J.↗
NASA NTRS2011

Cryogenic Behavior of the High Temperature Crystal Oscillator PX-570

Microprocessors, data-acquisition systems, and electronic controllers usually require timing signals for proper and accurate operation. These signals are, in most cases, provided by circuits that utilize crystal oscillators due to availability, cost, ease of operation, and accuracy. Stability of these oscillators, i.e. crystal characteristics, is usually governed, amongst other things, by the ambient temperature. Operation of these devices under extreme temperatures requires, therefore, the implementation of some temperature-compensation mechanism either through the manufacturing process of the oscillator part or in the design of the circuit to maintain stability as well as accuracy. NASA future missions into deep space and planetary exploration necessitate operation of electronic instruments and systems in environments where extreme temperatures along with wide-range thermal swings are countered. Most of the commercial devices are very limited in terms of their specified operational temperature while very few custom-made and military-grade parts have the ability to operate in a slightly wider range of temperature. Thus, it is becomes mandatory to design and develop circuits that are capable of operation efficiently and reliably under the space harsh conditions. This report presents the results obtained on the evaluation of a new (COTS) commercial-off-the-shelf crystal oscillator under extreme temperatures. The device selected for evaluation comprised of a 10 MHz, PX-570-series crystal oscillator. This type of device was recently introduced by Vectron International and is designed as high temperature oscillator [1]. These parts are fabricated using proprietary manufacturing processes designed specifically for high temperature and harsh environment applications [1]. The oscillators have a wide continuous operating temperature range; making them ideal for use in military and aerospace industry, industrial process control, geophysical fields, avionics, and engine control. They exhibit low jitter and phase noise, consume little power, and are suited for high shock and vibration applications. The unique package design of these crystal oscillators offers a small ceramic package footprint, as well as providing both through-hole mounting and surface mount options.

Patterson, Richard↗
NASA NTRS2024

Short-Term Elevated Temperature Mechanical Performance and Microstructure of A Niobium-Zirconium Alloy Produced via Laser Powder Bed Fusion In-Situ Alloying

Nb-1Zr is a readily fabricable, dispersion-strengthened niobium alloy with improved elevated temperature properties compared to commercially pure niobium. This low to moderate strength niobium alloy is desirable in thermal management systems for fission power and propulsion applications; however, pre-alloyed spherical feedstock for powder-based additive manufacturing processes is generally unavailable. Laser powder bed fusion (L-PBF) in-situ alloying of a Nb-1Zr chemistry was performed using a high-purity niobium feedstock coated with 1 wt% of zirconium-based ceramic compound nano-powders: ZrO 2 , ZrC, and ZrH 2 . The additively manufactured material was mechanically tested at elevated temperatures within a controlled environment in the as-built condition. For comparison, traditionally manufactured wrought feedstock was also tested within an identical environment. Examination of the materials’ microstructure and short-term elevated temperature mechanical response determined: in-situ alloying of spherical Nb powder feedstock with Zr-based ceramic nanoparticles can be successfully implemented; the ZrO 2 addition offered the greatest elevated temperature stability and strength but exhibited brittle behavior; the ZrC addition achieved a balance of room temperature ductility and elevated temperature strength; and the ZrH 2 -modified material had the lowest as-built interstitial content and showed high ductility with mechanical performance most similar to wrought Nb-1Zr.

Niobium Alloy↗
DOE OSTI2023

Microstructured ion-conducting composites and uses thereof

A composite membrane with nanostructured inorganic and organic phases is applied as an ion-selective layer to prove processability, prevent dendrite shorting, and increase power output of lithium-metal anodes through better Li-ion conductivity. Nanoconfinement, as opposed to macroscale confinement, is known to dramatically alter the properties of bulk materials. Control over a ceramic's size, shape, and properties is achieved with polymer templates. This is a new composition of matter and unique approach to composite membrane design.

Frischmann, Peter David↗
NASA NTRS2017

Advanced Environmental Barrier Coating Development for SiC-SiC Ceramic Matrix Composite Components

This presentation reviews the NASA advanced environmental barrier coating (EBC) system development for SiC-SiC Ceramic Matrix Composite (CMC) combustors particularly under the NASA Environmentally Responsible Aviation, Fundamental Aeronautics and Transformative Aeronautics Concepts Programs. The emphases have been placed on the current design challenges of the 2700-3000F capable environmental barrier coatings for low NOX emission combustors for next generation turbine engines by using advanced plasma spray based processes, and the coating processing and integration with SiC-SiC CMCs and component systems. The developments also have included candidate coating composition system designs, degradation mechanisms, performance evaluation and down-selects; the processing optimizations using TriplexPro Air Plasma Spray Low Pressure Plasma Spray (LPPS), Plasma Spray Physical Vapor Deposition and demonstration of EBC-CMC systems. This presentation also highlights the EBC-CMC system temperature capability and durability improvements under the NASA development programs, as demonstrated in the simulated engine high heat flux, combustion environments, in conjunction with high heat flux, mechanical creep and fatigue loading testing conditions.

CMAS↗
NASA NTRS2009

Recent Developments in Ultra High Temperature Ceramics at NASA Ames

NASA Ames is pursuing a variety of approaches to modify and control the microstructure of UHTCs with the goal of improving fracture toughness, oxidation resistance and controlling thermal conductivity. The overall goal is to produce materials that can perform reliably as sharp leading edges or nose tips in hypersonic reentry vehicles. Processing approaches include the use of preceramic polymers as the SiC source (as opposed to powder techniques), the addition of third phases to control grain growth and oxidation, and the use of processing techniques to produce high purity materials. Both hot pressing and field assisted sintering have been used to make UHTCs. Characterization of the mechanical and thermal properties of these materials is ongoing, as is arcjet testing to evaluate performance under simulated reentry conditions. The preceramic polymer approach has generated a microstructure in which elongated SiC grains grow in the form of an in-situ composite. This microstructure has the advantage of improving fracture toughness while potentially improving oxidation resistance by reducing the amount and interconnectivity of SiC in the material. Addition of third phases, such as Ir, results in a very fine-grained microstructure, even in hot-pressed samples. The results of processing and compositional changes on microstructure and properties are reported, along with selected arcjet results.

Johnson, Sylvia M.↗
DOE OSTI2024

Surface exsolving perovskite ceramics as catalyst for microwave methane pyrolysis to co-generate hydrogen and carbon nanotube

In this study, we have successfully developed a novel surface exsolving perovskite ceramic, which demonstrates the ability to simultaneously generate CO x -free hydrogen and carbon nanotubes (CNTs) through methane pyrolysis under the influence of microwave irradiation. We conducted an extensive survey and optimization of various perovskite materials specifically tailored for microwave applications. Among the materials investigated, nickel-doped strontium titanium oxide (STON) emerged as the most promising candidate, exhibiting both a satisfactory methane conversion rate and excellent responsiveness to microwave irradiation. Refinement of STON was carried out by fine-tuning the Ni content, optimizing the reduction dwell time, and adjusting the reduction temperature. Notably, SrTiNi 0.08 O 3 (STON8), demonstrated an impressive initial methane conversion rate of up to 40%. Transmission Electron Microscopy (TEM) provided visual evidence of the correlation between Ni content and reduction temperature, with respect to the exsolved Ni metal particle size. This finding highlights the immense potential of surface exsolving perovskite ceramics as a highly effective catalyst for the simultaneous production of CNTs and COx-free hydrogen via methane pyrolysis under microwave irradiation. Furthermore, it represents a step forward in the field of catalytic materials and microwave-driven processes.

08 HYDROGEN↗
DOE OSTI2014

Electrical and optical properties of NdAlO{sub 3} synthesized by an optimized combustion process

Nanocrystals of neodymium aluminate (NdAlO{sub 3}) are synthesized using an optimized single step auto-ignition citrate complex combustion process. The combustion product was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and Ultraviolet–visible reflection spectroscopy. The combustion product is single phase and composed of aggregates of nanocrystals of sizes in the range 20–40 nm. The NdAlO{sub 3} crystallized in rhombohedral perovskite structure with lattice parameters a = 5.3223 Å and c = 12.9292 Å. The absorption spectrum of the NdAlO{sub 3} nanocrystals shows characteristic absorption bands of the Nd atom. The polycrystalline fluffy combustion product is sintered to high density (∼ 97%) at ∼ 1450 °C for 4 h and the microstructure was characterized by scanning electron microscopy. The electrical properties of the sintered product were studied using dielectric measurements. The sintered NdAlO{sub 3} has a dielectric constant (ε{sub r}) and a dielectric loss (tan δ) of 21.9 and ∼ 10{sup −3} at 5 MHz, respectively. - Highlights: • NdAlO{sub 3} nanocrystals were synthesized through a citrate combustion process. • The nanocrystals were sintered to ∼ 97% of theoretical density. • The materials were characterized using a number of analytical techniques. • Nanostructured NdAlO{sub 3} showed crystal field splitting of Nd ions. • Dielectric properties of the sintered NdAlO{sub 3} ceramics were studied.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Review on dielectric properties of rare earth doped barium titanate

Rare earth doped Barium Titanate (BaTiO{sub 3}) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO{sub 3} (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO{sub 3} downshifted the Curie temperature (T{sub C}). Transition temperature also known as Curie temperature, T{sub C} where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO{sub 3}, Er-doped BaTiO{sub 3}, Sm-doped BaTiO{sub 3}, Nd-doped BaTiO{sub 3} and Ce-doped BaTiO{sub 3} had been proved to increase and the transition temperature or also known as T{sub C} also lowered down to room temperature as for all the RE doped BaTiO{sub 3} except for Er-doped BaTiO{sub 3}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

HGMS: Glasses and Nanocomposites for Hydrogen Storage

The primary goal of this project is to fabricate and investigate different glass systems and glass-derived nanocrystalline composite materials. These glass-based, two-phased materials will contain nanocrystals that can attract hydrogen and be of potential interest as hydrogen storage media. The glass materials with intrinsic void spaces that are able to precipitate functional nanocrystals capable to attract hydrogen are of particular interest. Proposed previously, but never practically implemented, one of promising concepts for storing hydrogen are micro-containers built of glass and shaped into hollow microspheres. The project expanded this concept to the exploration of glass-derived nanocrystalline composites as potential hydrogen storage media. It is known that the most desirable materials for hydrogen storage do not interact chemically with hydrogen and possess a high surface area to host substantial amounts of hydrogen. Glasses are built of disordered networks with ample void spaces that make them permeable to hydrogen even at room temperature. Glass-derived nanocrystalline composites (two-phased materials), combination of glasses (networks with ample voids) and functional nanocrystals (capable to attract hydrogen), appear to be promising candidates for hydrogen storage media. Key advantages of glass materials include simplicity of preparation, flexibility of composition, chemical durability, non-toxicity and mechanical strength, as well as low production costs and environmental friendliness. This project encompasses a fundamental research into physics and chemistry of glasses and nanocrystalline composite materials, derived from glass. Studies are aimed to answer questions essential for considering glass-based materials and composites as potential hydrogen storage media. Of particular interest are two-phased materials that combine glasses with intrinsic voids spaces for physisorption of hydrogen and nanocrystals capable of chemisorption. This project does not directly address any hydrogen storage technical barriers or targets in terms of numbers. Specifically, hydrogen sorption and desorption tests or kinetics measurements were not part of the project scope. However, the insights gained from these studies could help to answer fundamental questions necessary for considering glass-based materials as hydrogen storage media and could be applied indirectly towards the DOE hydrogen storage technical targets such as system weight and volume, system cost and energy density. Such questions are: Can specific macro-crystals, proven to attract hydrogen when in a macroscopic form (bulk), be nucleated in glass matrices as nanocrystals to create two-phased materials? What are suitable compositions that enable to synthetize glass-based, two-phase materials with nanocrystals that can attract hydrogen via surface or bulk interactions? What are the limits of controlling the microstructure of these materials, especially limits for nanocrystals density and size? Finally, from a technological point of view, the fabrication of glass-derived nanocomposites that we explore is a very simple, fast and inexpensive process that does not require costly or specialized equipment which is an important factor for practical applications.

08 HYDROGEN↗
DOE OSTI2021

High Temperature CMC Nozzles for 65% Efficiency

GE Gas Power has executed a development project that targeted cooled high-temperature ceramic matrix composite (CMC) nozzles as an innovative turbomachinery component that contributes toward the DOE’s goal for advanced gas turbines that are capable of at least 65% efficiency in combined cycle application. This technology advancement has potential to also benefit gas turbines used in coal-based IGCC applications with pre-combustion carbon capture and hydrogen as the resulting fuel. The development of this technology built upon CMC capability advancements made under earlier DOE programs. The objective for this project was to develop the application of ceramic matrix composite for nozzle application in an industrial gas turbine hot gas path. The CMC component development activity done in this project facilitates high firing temperatures through improved cooling designs and concepts, better sealing, reduced leakage, advanced manufacturing processes to facilitate high performing turbomachinery, and revolutionary component architecture to improve the gas turbine performance in a combined cycle application.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2019

Carbonized Microvascular Composites for Gas Receivers

This project is focused on the development and characterization of a novel carbonized microvascular composite intended for use in advanced, gas-phase Concentrating Solar Power (CSP) collectors, a muVASC receiver. These are polymer-fiber composites with directly integrated microchannels that will be carbonized to form a lightweight, high-absorptivity material that includes an embedded microvascular network of channels. The topology of these microchannels will be engineered to optimize heat transfer to a supercritical carbon dioxide (sCO2) heat transfer fluid. This system is based on the microVasc technology which enables the formation of defined channels within a composite material through selective depolymerization of polymer fibers. The resulting composite can then be carbonized and coated with an oxidation resistant coating, perhaps in situ, to form a thermally efficient, mechanically robust carbon-carbon composite. Carbon- carbon composites are a potential alternative to metallic systems, because these materials have extreme resistance to high temperatures and maintain mechanical properties with little change from room temperature up to almost 1800 °C and have high thermal conductivity. Compared to metallic microchannel receiver systems, we expect that the proposed system will allow for more efficient heat transfer, improved mechanical durability, and enhanced response to off-axis heating. These advantages will be realized through a combination of material performance and improved microchannel architectures as they are not constrained by available machining processes (weaving and 3-D printing for composites vs. machining for metal).

14 SOLAR ENERGY↗
NASA NTRS1983

A basic design fault in ceramic flat packs

Recent moisture resistance tests of various multilayer top brazed ceramic flat packs and leaded and unleaded chip carriers has revealed a serious design defect. These packages, which utilize a tungsten interconnect system, in the presence of high humidity, suffer a galvanic corrosion which anodically consumes the tungsten. This process can continue until the package suffers an open circuit. The test results indicate that the lead plating system does not adequately seal off the interface area where the tungsten strips egresses from the inside of the package.

Drotman, B.↗