New Generation of Plasma‐Sprayed Mullite Coatings on Silicon Carbide

Lee, Kang N.; Miller, Robert A.; Jacobson, Nathan

doi:10.1111/j.1151-2916.1995.tb08236.x

Cited by 240 publications

(143 citation statements)

References 10 publications

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“…Details of the processing of these coatings can be found in previous publications (Faber et al, 2007;Lee et al, 1995). The thick· ness of the Si layer was ~ 130 µm and the mullite, mullite + 20% SAS and BSAS layers were each ~200 µm.…”

Section: Methodsmentioning

confidence: 99%

In situ stress analysis of multilayer environmental barrier coatings

et al. 2009

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The biaxial stress and thermal expansion of multilayer doped-aluminosilicate environmental barrier coatings were measured in situ during cooling using microfocused high-energy X-rays in transmission. Coating stresses during cooling from 1000 ° C were measured for as-sprayed and thermally cycled samples. In the as-sprayed state, tensile stresses as high as 75 MPa were measured in the doped-aluminosilicate topcoat at 375 °C, after which a drop in the sti;ess occurred accompanied by through-thickness cracking of the two outermost layers. After thermally cycling the samples, the stress in the topcoat was reduced to approximately 50 MPa, and there was no drop in stress upon cooling. This stress reduction was attributed to a crystallographic phase transformation of the topcoat and the accompanying change in thermal expansion coefficient. The addition of a doped aluminosilicate to the mullite layer did not lower the stress in the topcoat, but may offer increased durability due to an increased compressive stress.

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Section: Methodsmentioning

confidence: 99%

In situ stress analysis of multilayer environmental barrier coatings

et al. 2009

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“…Appropriate boundary conditions, such as thermal and mechanical, high temperature, burner flame, and cooling, are all included in the analyses. Table 1 [14] shows the material properties for the EBCs and the substrate used. The intermediate coat layer material properties are calculated using the rule of mixtures formulation.…”

Section: Analytical Approach and Finite Element Analysismentioning

confidence: 99%

Criteria for Crack Deflection-Penetration in EBC Coated Ceramics: A Parametric Study

Abdul-Aziz

Bhatt

Grady

2015

Mechanics of Advanced Materials and Structures

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This article discusses results obtained from a parametric study to analytically evaluate the impingement of a crack at the interface of an environmental barrier coating (EBC) and a monolithic Silicon nitride (Si 3 N 4 ) layered ceramics substrate. The study establishes a correlation that leads to determine if the crack is arrested or advanced by either penetrating or deflecting along the EBC/substrate interface. A finite-element-based fracture mechanics methodology is utilized to perform these calculations. Critical parameters determining penetration-deflection conditions in relation to EBC's physical characteristics, such as porosity level, voids, and mini cracks, are determined for a single layer and multi-layered coating system coordinating the interactions between the EBCs (Mullite, Mullite mixture, Silicon nitride, etc.) and the substrate structure. Results showing thermo-mechanical stresses and stress/strain energy release relations with respect to crack penetration-deflection are presented and discussed as the crack is advanced. = stress at the interface r and = radial distance and the polar angle f ij ( ) = angular distribution of the singular stress field = defines the strength of stress singularity ␣ and ␤ = Dundurs bi-material parameters E' j = E j is for plane stress E' j = E j /(1 -j ) for plane strain (1 and 2 denote the material) = shear modulus [MPa] G d = (material 1) is the strain energy release rate associated with the "deflected" crack or adhesive failure G p = (material 2) is the strain energy release rate associated with the "penetrated" crack (or cohesive failure of adjacent material) G pc = cohesive or penetrated fracture energy G dc = adhesive or deflected fracture energy, respectively K 1 and K 2 = stress intensity factors for the interface crack ε = a function of material constants Keywords

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“…, and the thermal expansion of the natural aluminosilicate crystal composite mullite (3·Al 2 O 3 +2·SiO 2 ) is well-matched to be between 4.5 × 10 − 6 K − 1 and 5.4 ×10 − 6 K − 1 [12][13][14]. Allowing a mismatch of less than ±50% from these values, only materials with thermal expansions in the range of 2×10 − 6 K − 1 to 8× 10 − 6 K − 1 would be practical.…”

Section: Thin Solid Films XXX (2012) Xxx-xxxmentioning

confidence: 99%

Ceramic thin film thermocouples for SiC-based ceramic matrix composites

2012

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Conductive ceramic thin film thermocouples were investigated for application to silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiC/SiC CMC) components. High temperature conductive oxides based on indium and zinc oxides were selected for testing to high temperatures in air. Sample oxide films were first sputtered-deposited on alumina substrates then on SiC/SiC CMC sample disks. Operational issues such as cold junction compensation to a 0°C reference, resistivity and thermopower variations are discussed. Results show that zinc oxides have an extremely high resistance and thus increased complexity for use as a thermocouple, but thermocouples using indium oxides can achieve a strong, nearly linear response to high temperatures.Published by Elsevier B.V.

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New Generation of Plasma‐Sprayed Mullite Coatings on Silicon Carbide

Cited by 240 publications

References 10 publications

In situ stress analysis of multilayer environmental barrier coatings

In situ stress analysis of multilayer environmental barrier coatings

Criteria for Crack Deflection-Penetration in EBC Coated Ceramics: A Parametric Study

Ceramic thin film thermocouples for SiC-based ceramic matrix composites

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