Download or read book In situ generated Yb Si O environmental barrier coatings to protect non oxide silicon based ceramics in gas turbines Band 16 written by Mateus Lenz Leite and published by Cuvillier Verlag. This book was released on 2022-02-25 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: In face of an accelerating climate change, the reduction and substitution of fossil fuels is crucial to decarbonize energy production. Gas turbines can operate with versatile fuel sources like natural gas and future fuels such as hydrogen and ammonia. In a next future, thermal efficiencies above 65% are expected to be achieved by implementing non-oxide silicon-based (i.e. Si₃N₄, SiC and SiC/SiC) ceramic components. However, water vapor is one of the main combustion products, which leads to rapid corrosion due to the volatilization of the protective SiO₂ layer above 1200 °C. Hence, an in situ generated Yb₂Si₂O₇ double layered environmental barrier coating system composed of silazanes and the active fillers Yb2O3 and Si was processed at 1415 °C for 5 h in air to protect Si3N4, SiC and SiC/SiC from corrosion. The easy to apply coating system exhibits a dense microstructure with a thickness of up to 150 µm, besides an excellent adhesion strength (36.9 ± 6.2 MPa), hardness (6.9 ± 1.6 GPa) and scratch resistance (28 N). It remarkably overcomes over 15 thermal cycles between 1200 and 20 °C and shows almost no mass loss after harsh hot gas corrosion at 1200 °C for 200 h (pH2O = 0.15 atm, v = 100 m s⁻¹).

Download or read book In Situ Generated Yb2Si2O7 Environmental Barrier Coatings to Protect Non oxide Silicon based Ceramics in Gas Turbines written by Mateus Lenz Leite and published by Cuvillier. This book was released on 2022-02-25 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: In face of an accelerating climate change, the reduction and substitution of fossil fuels is crucial to decarbonize energy production. Gas turbines can operate with versatile fuel sources like natural gas and future fuels such as hydrogen and ammonia. In a next future, thermal efficiencies above 65% are expected to be achieved by implementing non-oxide silicon-based (i.e. Si₃N₄, SiC and SiC/SiC) ceramic components. However, water vapor is one of the main combustion products, which leads to rapid corrosion due to the volatilization of the protective SiO₂ layer above 1200 °C. Hence, an in situ generated Yb₂Si₂O₇ double layered environmental barrier coating system composed of silazanes and the active fillers Yb2O3 and Si was processed at 1415 °C for 5 h in air to protect Si3N4, SiC and SiC/SiC from corrosion. The easy to apply coating system exhibits a dense microstructure with a thickness of up to 150 μm, besides an excellent adhesion strength (36.9 ± 6.2 MPa), hardness (6.9 ± 1.6 GPa) and scratch resistance (28 N). It remarkably overcomes over 15 thermal cycles between 1200 and 20 °C and shows almost no mass loss after harsh hot gas corrosion at 1200 °C for 200 h (pH2O = 0.15 atm, v = 100 m s⁻1).

Download or read book Environmental Barrier Coatings written by Kang N. Lee and published by MDPI. This book was released on 2020-12-29 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The global increase in air travel will require commercial vehicles to be more efficient than ever before. Advanced engine hot section materials are a key technology required to keep fuel consumption and emission to a minimum in next-generation gas turbines. Ceramic matrix composites (CMCs) are the most promising material to revolutionize gas turbine hot section materials technology because of their excellent high‐temperature properties. Rapid surface recession due to volatilization by water vapor is the Achilles heel of CMCs. Environmental barrier coatings (EBCs) is an enabling technology for CMCs, since it protects CMCs from water vapor. The first CMC component entered into service in 2016 in a commercial engine, and more CMC components are scheduled to follow within the next few years. One of the most difficult challenges to CMC components is EBC durability, because failure of EBC leads to a rapid reduction in CMC component life. Key contributors to EBC failure include recession, oxidation, degradation by calcium‐aluminum‐magnesium silicates (CMAS) deposits, thermal and thermo‐mechanical strains, particle erosion, and foreign object damage (FOD). Novel EBC chemistries, creative EBC designs, and robust processes are required to meet EBC durability challenges. Engine-relevant testing, characterization, and lifing methods need to be developed to improve EBC reliability. The aim of this Special Issue is to present recent advances in EBC technology to address these issues. In particular, topics of interest include but are not limited to the following: • Novel EBC chemistries and designs; • Processing including plasma spray, suspension plasma spray, solution precursor plasma spray, slurry process, PS-PVD, EB-PVD, and CVD; • Testing, characterization, and modeling; • Lifing.

Download or read book Environmental Barrier Coatings written by Kang N. Lee and published by . This book was released on 2020 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The global increase in air travel will require commercial vehicles to be more efficient than ever before. Advanced engine hot section materials are a key technology required to keep fuel consumption and emission to a minimum in next-generation gas turbines. Ceramic matrix composites (CMCs) are the most promising material to revolutionize gas turbine hot section materials technology because of their excellent high-temperature properties. Rapid surface recession due to volatilization by water vapor is the Achilles heel of CMCs. Environmental barrier coatings (EBCs) is an enabling technology for CMCs, since it protects CMCs from water vapor. The first CMC component entered into service in 2016 in a commercial engine, and more CMC components are scheduled to follow within the next few years. One of the most difficult challenges to CMC components is EBC durability, because failure of EBC leads to a rapid reduction in CMC component life. Key contributors to EBC failure include recession, oxidation, degradation by calcium-aluminum-magnesium silicates (CMAS) deposits, thermal and thermo-mechanical strains, particle erosion, and foreign object damage (FOD). Novel EBC chemistries, creative EBC designs, and robust processes are required to meet EBC durability challenges. Engine-relevant testing, characterization, and lifing methods need to be developed to improve EBC reliability. The aim of this Special Issue is to present recent advances in EBC technology to address these issues. In particular, topics of interest include but are not limited to the following: • Novel EBC chemistries and designs; • Processing including plasma spray, suspension plasma spray, solution precursor plasma spray, slurry process, PS-PVD, EB-PVD, and CVD; • Testing, characterization, and modeling; • Lifing.

Download or read book Tantalum Oxide based Plasma sprayed Environmental Barrier Coatings written by Christopher M. Weyant and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy efficiency in gas turbine engines is linked to the high temperature capabilities of materials used in the hot section of the engine. To facilitate a significant increase in engine efficiency, tough structural ceramics have been developed that can handle the thermo-mechanical stresses that gas turbine components experience. Unfortunately, the high-temperature, high-pressure, and high-velocity combustion gases in a gas turbine contain water vapor and/or hydrogen which have been shown to volatilize the protective silica layer on silicon-based ceramics. This degradation leads to significant surface recession in ceramic gas turbine components.

Download or read book Ceramic Fibers and Coatings written by Committee on Advanced Fibers for High-Temperature Ceramic Composites and published by National Academies Press. This book was released on 1998-05-05 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-temperature ceramic fibers are the key components of ceramic matrix composites (CMCs). Ceramic fiber properties (strength, temperature and creep resistance, for example)-along with the debonding characteristics of their coatings-determine the properties of CMCs. This report outlines the state of the art in high-temperature ceramic fibers and coatings, assesses fibers and coatings in terms of future needs, and recommends promising avenues of research. CMCs are also discussed in this report to provide a context for discussing high-temperature ceramic fibers and coatings.

Download or read book Thermal and Environmental Barrier Coatings for Advanced Turbine Engine Applications written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-20 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ceramic thermal and environmental barrier coatings (T/EBCs) will play a crucial role in advanced gas turbine engine systems because of their ability to significantly increase engine operating temperatures and reduce cooling requirements, thus help achieve engine low emission and high efficiency goals. Advanced T/EBCs are being developed for the low emission SiC/SiC ceramic matrix composite (CMC) combustor applications by extending the CMC liner and vane temperature capability to 1650 C (3000 F) in oxidizing and water vapor containing combustion environments. Low conductivity thermal barrier coatings (TBCs) are also being developed for metallic turbine airfoil and combustor applications, providing the component temperature capability up to 1650 C (3000 F). In this paper, ceramic coating development considerations and requirements for both the ceramic and metallic components will be described for engine high temperature and high-heat-flux applications. The underlying coating failure mechanisms and life prediction approaches will be discussed based on the simulated engine tests and fracture mechanics modeling results.Zhu, Dong-Ming and Miller, Robert A.Glenn Research CenterTHERMAL CONTROL COATINGS; GAS TURBINE ENGINES; CERAMIC COATINGS; CERAMIC MATRIX COMPOSITES; COMBUSTION CHAMBERS; ENGINE PARTS; CERAMICS; AIRFOILS; REFRACTORY MATERIALS; THERMAL CONDUCTIVITY; METALS; SILICON CARBIDES

Download or read book Slurry Based Coatings on Silicon Based Ceramics written by and published by . This book was released on 2008 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of advanced structural ceramics, such as Si3N4 (SN282), SiC, and SiC/SiC composites, is a promising technology to accomplish the high performance goals for advanced turbine applications. These materials exhibit excellent corrosion resistance by forming a dense silica scale. However, severe degradation of the silica scale has been observed due to the presence of certain environmental species, like alkali salts and water vapors, limiting the long-term reliability of structural ceramics. Presence of water vapor in the turbine environment leads to the formation of a gaseous silicon hydroxide species (Si(OH)4) via a reaction with silica layer, SiO2(s) + 2H2O(g) = Si(OH)4(g). The Si(OH)4 is swept away in turbine environments resulting in continued recession of the substrate. Purpose of this research is to develop environmental barrier coatings (EBCs) for silicon nitride substrates (Si3N4 and SN282) that will protect them from water/salt vapor damage and enhance their usage. Slurry dip coating is chosen as the coating method in this research because it is easy, cost- efficient, and suitable to coat on complex shaped ceramic components because of its non-line-of-site nature. Mullite (3A12O3.2SiO2) is chosen as coating material because it has good mechanical properties at high temperatures, and a coefficient of thermal expansion (CTE) that is very close to Si3N4 [SN282] (CTE of Mullite is 5.3 x 10-6 *C-1 and CTE of SiC is 4.7 x 10-6 *C-1 and Si3N4 [SN282] is 3-4 x 10-6 *C-1). Mullite slurry is modified with sintering enhancing additives of rare earth silicates, such as gadolinium, lutetium, hafnium, and erbium. Mullite/ rare earth silicate slurry, sintered at high temperatures (1375*C - 1450°C) and coated on Si3N4 and SN282 substrates, did not show good bonding with the substrates. Yttria-alumina containing Si3N4 substrates coated with Mullite slurry and sintered at high temperatures (1375*C - 1430*C) also showed lack of good bonding between the coat and substrate. 100% mullite coating sintered at 1475*C and 50% mullite sol + 50% mullite powder coating sintered at 1450*C on SN282 substrate showed good bonding of the coating to the substrate without any cracks at the interface.

Download or read book Refractory Oxide Coatings on SiC Ceramics written by and published by . This book was released on 1994 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Key durability issues with mullite based environmental barrier coatings for Si based ceramics ASME 99 GT 443 written by Kang N. Lee and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Indianapolis, Indiana, Jun 7-Jun 10, 1999.

Download or read book Functionally Graded Mullite Coatings for Gas Turbines written by Tushar Kulkarni and published by . This book was released on 2010 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The next generation of heat exchangers and gas turbines require high performance materials as they need to operate at higher temperatures for higher efficiency. SiC and Si 3 N 4 are promising candidates as they have excellent high temperature properties. However, when used in complex combustion environments found in gas-turbine applications, these materials have two major concerns; namely hot-corrosion and recession. It is well established that environmental barrier coatings (EBC) can be utilized to overcome these limitations. Although chemical vapor deposited (CVD) mullite (3Al 2 O 3 .2SiO 2 ) coatings developed before this study have shown promise in protecting Si-based substrates, there is concern that the silica content within the mullite coating itself might be susceptible to hot-corrosion and recession during long term exposure to corrosive atmospheres containing Na/V salts and water vapor. There is thus strong motivation to substantially reduce or even virtually eliminate the silica component from the surfaces of mullite coatings that are in direct contact with atmospheres containing corrosive oxides and steam. In this study, CVD has been used to deposit mullite coatings with potential promise to protect Si-based ceramics for high temperature applications. The composition of these functionally graded mullite coatings was varied from silica-rich close to the coating/substrate (SiC) interface for coefficient of thermal expansion match to alumina-rich towards the outer surface of the coating. In the process, the highest alumina-rich mullite ever reported has been deposited. The phase transformation and hot-corrosion behavior of the coatings was also investigated in this work. The coatings show immense potential to protect Si-based ceramics. It is expected that these coatings will have very broad impact by enabling gas turbines to operate at higher temperatures leading to improved fuel efficiency and reduced emissions.

Download or read book Creep Behavior of Hafnia and Ytterbium Silicate Environmental Barrier Coating Systems on Sic Sic Ceramic Matrix Composites written by Dongming Zhu and published by BiblioGov. This book was released on 2013-06 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Environmental barrier coatings will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability and stability of SiC/SiC ceramic matrix composite (CMC) engine components, thus improving the engine performance. In order to develop high performance, robust coating systems for engine components, appropriate test approaches simulating operating temperature gradient and stress environments for evaluating the critical coating properties must be established. In this paper, thermal gradient mechanical testing approaches for evaluating creep and fatigue behavior of environmental barrier coated SiC/SiC CMC systems will be described. The creep and fatigue behavior of Hafnia and ytterbium silicate environmental barrier coatings on SiC/SiC CMC systems will be reported in simulated environmental exposure conditions. The coating failure mechanisms will also be discussed under the heat flux and stress conditions.

Download or read book Novel Environmental Barrier Coatings for Resistance Against Degradation by Molten Glassy Deposits in the Presence of Water Vapor written by Caitlin Maureen Toohey and published by . This book was released on 2011 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Environmental barrier coatings (EBCs) are used to prevent oxidation of underlying ceramic-matrix composite (CMC) structural components in aircraft gas-turbine engines. As operating temperatures increase, ingested airborne sand poses a serious threat to the stability of these coatings, because the sand adheres to the hot EBC surfaces and melts, forming calcium--magnesium--aluminosilicate (CMAS) glass. The reaction of EBCs with molten CMAS can lead to EBC delamination. Additionally, the interaction of water vapor with the CMAS--reacted EBCs can result in the formation of undesirable phases. Yb2Si2O-- has been identified as a promising EBC ceramic, based on its desirable properties: phase stability up to 1600°C, low thermal expansion coefficient mismatch with common CMCs, and potential resistance against degradation by CMAS and water vapor. As--sintered Yb2Si2O-- and CMAS--coated Yb2Si2O-- are tested in an air environment and in a water vapor environment, at a temperature of 1300°C in both cases. The behavior of these ceramics is compared to that of reference materials. Results from oxidation and chemical stability studies and analyses are presented.

Download or read book Micro and Nanomecanical Behavior of Mullite based Environmental Barrier Coatings written by Carlos Alberto Botero Vega and published by . This book was released on 2013 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mullite coatings deposited by chemical vapor deposition (CVD) have been introduced and proven as excellent candidates to protect silicon carbide (SiC) from severe pitting corrosion and recession, becoming part of the new generation of environmental barrier coatings (EBCs). In these coatings mullite columns nucleate from a thin vitreous silicon layer in contact with the substrate and can grow over a wide range of increasing Al/Si ratios in constant or graded compositions. This feature allows for obtaining Al-rich coatings at the outer surface (conferring superior corrosion protection to the substrate) while keeping the stoichiometric mullite composition at the interface (representing great adhesion because of the good match with SiC). Although the excellent performance of these coatings in corrosive environments has been proved, information about the mechanical behavior of these systems is quite limited. The mechanical properties and structural integrity of CVD mullite coatings on SiC substrates are key issues facing the implementation of these systems in real applications. The study of such aspects constitutes the basis of this investigation. Considering the compositional variations, microstructure, and thickness of CVD mullite coatings, it is essential to evaluate their mechanical properties, and the structural integrity of the coated system, from a local perspective. In this regard, nanoindentation and nanoscratch appear as the most suitable techniques for this purpose. This investigation is based on implementing nanoindentation and nanoscratch tests, together with advanced characterization techniques, to evaluate the main local mechanical properties of mullite-based EBCs as well as to investigate the structural integrity of the coated systems. In doing so, columnar mullite coatings composed of stoichiometric (¿ 3) and increasing (¿ 5, 6, 7, 8, 11) Al/Si ratios, as well as compositionally graded coatings, were accounted for. Regarding stoichiometric coatings, main mechanical properties; i.e. hardness (Hf), elastic modulus (Ef), yield strength (sy) and fracture toughness (Kf), are asessed by means of nanoindentation. As a consequence of the columnar nature of coatings as well as the vitreous silicon layer from which they grow, properties were found to be slightly lower than the ones reported for bulk stoichiometric mullite. Also, properties ascribed to the coated system such as energy of adhesion (Gint) and interface fracture toughness (Kint), are assessed. Nanoscratch tests demonstrate great resistance of coatings to the sliding contact, as considerable plastic deformation ocurrs without significant damage. The effect of coating composition on its mechanical behavior is studied through evaluation of specimens with increasing Al/Si ratios. Enrichment in Al produce hardening, stiffening and enbrittlement of mullite coatings. Nevertheless, nanoscratch tests show that structural integrity of the systems is satisfactory since no complete loss of the coating material is registered. An enhancement in Hf and Ef is also evidenced through the thickness of coatings with graded compositions. Nanoscratch tests performed in the cross section of compositionally graded mullite coatings show an optimum combination of stiffness/hardness and cohesive/adhesive scratch strength, as compared to coatings with stoichiometric or extreme Al-enriched compositions. Finally, temperature and corrosion effects on the mechanical behavior are investigated. In stoichiometric mullite, the effect of high temperature is an increase in Hf and Ef, accompanied by a decrease in Kc, whereas none of these properties are altered for Al-rich and the compositionally graded coatings. In addition, nanoscratch tests show that the effect of temperature and hot-corrosion on the structural integrity of tested coatings may be considered as negligible. This is an interesting finding as CVD mullite coatings are expected to be used in gas turbines, under sam.

Download or read book Semiconductor Gas Sensors written by Raivo Jaaniso and published by Woodhead Publishing. This book was released on 2019-09-24 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor Gas Sensors, Second Edition, summarizes recent research on basic principles, new materials and emerging technologies in this essential field. Chapters cover the foundation of the underlying principles and sensing mechanisms of gas sensors, include expanded content on gas sensing characteristics, such as response, sensitivity and cross-sensitivity, present an overview of the nanomaterials utilized for gas sensing, and review the latest applications for semiconductor gas sensors, including environmental monitoring, indoor monitoring, medical applications, CMOS integration and chemical warfare agents. This second edition has been completely updated, thus ensuring it reflects current literature and the latest materials systems and applications. Includes an overview of key applications, with new chapters on indoor monitoring and medical applications Reviews developments in gas sensors and sensing methods, including an expanded section on gas sensor theory Discusses the use of nanomaterials in gas sensing, with new chapters on single-layer graphene sensors, graphene oxide sensors, printed sensors, and much more

Download or read book Cementitious Materials for Nuclear Waste Immobilization written by Rehab O. Abdel Rahman and published by John Wiley & Sons. This book was released on 2014-11-17 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cementitious materials are an essential part in any radioactive waste disposal facility. Conditioning processes such as cementation are used to convert waste into a stable solid form that is insoluble and will prevent dispersion to the surrounding environment. It is incredibly important to understand the long-term behavior of these materials. This book summarises approaches and current practices in use of cementitious materials for nuclear waste immobilisation. It gives a unique description of the most important aspects of cements as nuclear waste forms: starting with a description of wastes, analyzing the cementitious systems used for immobilization and describing the technologies used, and ending with analysis of cementitious waste forms and their long term behavior in an envisaged disposal environment. Extensive research has been devoted to study the feasibility of using cement or cement based materials in immobilizing and solidifying different radioactive wastes. However, these research results are scattered. This work provides the reader with both the science and technology of the immobilization process, and the cementitious materials used to immobilize nuclear waste. It summarizes current knowledge in the field, and highlights important areas that need more investigation. The chapters include: Introduction, Portland cement, Alternative cements, Cement characterization and testing, Radioactive waste cementation, Waste cementation technology, Cementitious wasteform durability and performance assessment.

Download or read book Ceramic Materials and Components for Engines written by Jürgen G. Heinrich and published by John Wiley & Sons. This book was released on 2008-11-21 with total page 678 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several ceramic parts have already proven their suitability for serial application in automobile engines in very impressive ways, especially in Japan, the USA and in Germany. However, there is still a lack of economical quality assurance concepts. Recently, a new generation of ceramic components, for the use in energy, transportation and environment systems, has been developed. The efforts are more and more system oriented in this field. The only possibility to manage this complex issue in the future will be interdisciplinary cooperation. Chemists, physicists, material scientists, process engineers, mechanical engineers and engine manufacturers will have to cooperate in a more intensive way than ever before. The R&D activities are still concentrating on gas turbines and reciprocating engines, but also on brakes, bearings, fuel cells, batteries, filters, membranes, sensors and actuators as well as on shaping and cutting tools for low expense machining of ceramic components. This book summarizes the scientific papers of the 7th International Symposium "Ceramic Materials and Components for Engines". Some of the most fascinating new applications of ceramic meterials in energy, transportation and environment systems are presented. The proceedings shall lead to new ideas for interdisciplinary activities in the future.