Upper Temperature Limit of Environmental Barrier Coatings Based on Mullite and BSAS

Lee, Kang N.; Fox, Dennis S.; Eldridge, Jeffrey I.; Zhu, Dongming; Robinson, R. Craig; Bansal, Narottam P.; Miller, Robert A.

doi:10.1111/j.1151-2916.2003.tb03466.x

Cited by 328 publications

(228 citation statements)

References 17 publications

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“…Due to its high resistance to oxidation and reduction [1], low dielectric constant [2] and low thermal expansion coefficient [3], barium aluminosilicate (BaAl 2 Si 2 0 8 , or BAS 2 )\ particularly in its monoclinic form, constitutes an attractive material for the matrix of ceramic composites [4,5], as well as for protective coatings [6]. BaAl 2 Si 2 0 8 has three polymorphic forms: monoclinic (usually denominated either as Celsian or as Monocelsian), hexagonal (Hexacelsian) and orthorhombic [3,7].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of monoclinic Celsian from Coal Fly Ash by using a one-step solid-state reaction process

Long-González

López-Cuevas

Gutiérrez-Chavarría

et al. 2010

Ceramics International

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Monoclinic (Celsian) and hexagonal (Hexacelsian) Ba 1 _ JC Sr JC Al 2 Si 2 0 8 solid solutions, where x = 0,0.25,0.375,0.5,0.75 or 1, were synthesized by using Coal Fly Ash (CFA) as main raw material, employing a simple one-step solid-state reaction process involving thermal treatment for 5 h at 850-1300 °C. Fully monoclinic Celsian was obtained at 1200 °C/5 h, for SrO contents of 0.25 < x < 0.75. However, an optimum SrO level of 0.25 < x < 0.375 was recommended for the stabilization of Celsian. These synthesis conditions represent a significant improvement over the higher temperatures, longer times and/or multi-step processes needed to obtain fully monoclinic Celsian, when other raw materials are used for this purpose, according to previous literature. These results were attributed to the role of the chemical and phase constitution of CFA as well as to a likely mineralizing effect of CaO and Ti0 2 present in it, which enhanced the Hexacelsian to Celsian conversion.

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Section: Introductionmentioning

confidence: 99%

Synthesis of monoclinic Celsian from Coal Fly Ash by using a one-step solid-state reaction process

Long-González

López-Cuevas

Gutiérrez-Chavarría

et al. 2010

Ceramics International

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“…EBC systems consisting of a silicon bond coat and a rare-earth (RE) silicate (e.g., Yb 2 Si 2 O 7 , Lu 2 Si 2 O 7 ) top coat layer were successfully tested in gas turbine engines [10][11][12][13][14]. In these EBC systems, RE-silicates with a high water vapor stability impede the diffusion of oxygen and water vapor to the substrate.…”

Section: Introductionmentioning

confidence: 99%

Application of High-Velocity Oxygen-Fuel (HVOF) Spraying to the Fabrication of Yb-Silicate Environmental Barrier Coatings

et al. 2017

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From the literature, it is known that due to their glass formation tendency, it is not possible to deposit fully-crystalline silicate coatings when the conventional atmospheric plasma spraying (APS) process is employed. In APS, rapid quenching of the sprayed material on the substrate facilitates the amorphous deposit formation, which shrinks when exposed to heat and forms pores and/or cracks. This paper explores the feasibility of using a high-velocity oxygen-fuel (HVOF) process for the cost-effective fabrication of dense, stoichiometric, and crystalline Yb 2 Si 2 O 7 environmental barrier coatings. We report our findings on the HVOF process optimization and its resultant influence on the microstructure development and crystallinity of the Yb 2 Si 2 O 7 coatings. The results reveal that partially crystalline, dense, and vertical crack-free EBCs can be produced by the HVOF technique. However, the furnace thermal cycling results revealed that the bonding of the Yb 2 Si 2 O 7 layer to the Silicon bond coat needs to be improved.

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“…In gas turbines, a low permeability for water vapors is a critical characteristic for an EBC system so as to inhibit the formation of silicon hydroxide (Si(OH) 4 ) gas by the reaction of the water vapor originating from the jet fuel combustion with the SiO 2 scale formed on the Si-based substrate (Ref [1][2][3][4][5][6]. Future hypersonic vehicles flying in low Earth orbit will also employ Si-based materials on their external structure.…”

Section: Introductionmentioning

confidence: 99%

“…Coatings for components formed of Si-based materials must fulfill an important coincident role namely to provide an environmental protection against water vapors and corrosive molten aluminosilicates. Thus these coatings have been named environmental barrier coatings (EBCs) (Ref [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Elastic Modulus Evolution and Behavior of Si/Mullite/BSAS-Based Environmental Barrier Coatings Exposed to High Temperature in Water Vapor Environment

et al. 2010

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Elastic modulus evolution and behaviour of Si/Mullite/BSAS-based environmental barrier coatings exposed to high temperature in water vapour environment Cojocaru, C. V.; Kruger, S. E.; Moreau, C.; Lima, R. S. Submitted May 14, 2010; in revised form October 22, 2010) Si-based ceramics (e.g., SiC and Si 3 N 4 ) are known as promising high-temperature structural materials in various components where metals/alloys reached their ultimate performances (e.g., advanced gas turbine engines and structural components of future hypersonic vehicles). To alleviate the surface recession that Si-based ceramics undergo in a high-temperature environmental attack (e.g., H 2 O vapor), appropriate refractory oxides are engineered to serve as environmental barrier coatings (EBCs). The current stateof-the-art EBCs multilayer system comprises a silicon (Si) bond coat, mullite (3Al 2 O 3 AE2SiO 2 ) interlayer and (1 2 x)BaOAExSrOAEAl 2 O 3 AE2SiO 2 ,0 £ x £ 1 (BSAS) top coat. In this article, the role of hightemperature exposure (1300°C) performed in H 2 O vapor environment (for time intervals up to 500 h) on the elastic moduli of air plasma sprayed Si/mullite/BSAS layers deposited on SiC substrates was investigated via depth-sensing indentation. Laser-ultrasonics was employed to evaluate the E values of as-sprayed BSAS coatings as an attempt to validate the indentation results. Fully crystalline, crack-free, and near-crack-free as-sprayed EBCs were engineered under controlled deposition conditions. The absence of phase transformation and stability of the low elastic modulus values (e.g.,~60-70 GPa) retained by the BSAS top layers after harsh environmental exposure provides a plausible explanation for the almost crack-free coatings observed. The relationships between the measured elastic moduli of the EBCs and their microstructural behavior during the high-temperature exposure are discussed.

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Upper Temperature Limit of Environmental Barrier Coatings Based on Mullite and BSAS

Cited by 328 publications

References 17 publications

Synthesis of monoclinic Celsian from Coal Fly Ash by using a one-step solid-state reaction process

Synthesis of monoclinic Celsian from Coal Fly Ash by using a one-step solid-state reaction process

Application of High-Velocity Oxygen-Fuel (HVOF) Spraying to the Fabrication of Yb-Silicate Environmental Barrier Coatings

Elastic Modulus Evolution and Behavior of Si/Mullite/BSAS-Based Environmental Barrier Coatings Exposed to High Temperature in Water Vapor Environment

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