Functionally graded chemical vapor deposited mullite environmental barrier coatings for Si-based ceramics

Basu, Soumendra N.; Kulkarni, T.; Wang, H.Z.; Sarin, V.K.

doi:10.1016/j.jeurceramsoc.2007.03.007

Cited by 53 publications

(25 citation statements)

References 16 publications

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“…It is well known that growth rate of mullite along [001] direction is most favorable implying that atomic rearrangements happen fastest along the (001) plane. 3,11 This is consistent with the observation that CVD mullite coatings exhibit a distinct texture, with the c axis of the mullite grains being oriented along the growth direction for a columnar grain microstructure. 13 Therefore, the gas phase Al/Si ratio was manipulated initially until mullite nucleated and the Al/Si ratio in the coating reached a value of 8.…”

Section: Methodssupporting

confidence: 84%

“…All reactant gases were premixed just before introduction into the hot-wall reactor. 3,4 The typical deposition temperature, total reactor pressure, and deposition time were 975 C, 75 Torr, and 3 h, respectively. It is well known that growth rate of mullite along [001] direction is most favorable implying that atomic rearrangements happen fastest along the (001) plane.…”

Section: Methodsmentioning

confidence: 99%

“…[3][4][5][6] The composition of these functionally graded mullite coatings was varied from silica-rich close to the coating/substrate (SiC) interface to alumina-rich toward the outer surface of the coating, with the aim of achieving silica-free mullite hypothesized as i-alumina by Cameron. 7 It is well known that it is possible to change x from 0 to 1 in the general mullite formula of Al 4+2x Si 2-2x O 10-x .…”

Section: Introductionmentioning

confidence: 99%

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Compositionally graded mullite-based chemical vapor deposited coatings

et al. 2009

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Dense, crystalline mullite (3Al 2 O 3 Á2SiO 2 ) coatings have been deposited by chemical vapor deposition on Si-based substrates using the AlCl 3 -SiCl 4 -CO 2 -H 2 system. A graded coating composition has been achieved in the coatings, with the Al/Si ratio being stoichiometric ($3) at the coating/substrate interface, and increasing monotonically toward the outer coating surface. The highest reported Al-rich mullite has been deposited in the process. At high Al/Si ratios, the mullite structure breaks down and an aluminosilicate phase similar to the metastable d* Al 2 O 3 is nucleated. Experimental evidence is presented in this study that this phase has some Si-incorporation in it and has been called d* (Si) Al 2 O 3 . Like the other known aluminosilicates, d* (Si) Al 2 O 3 converts to mullite on heating at elevated temperatures.

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Section: Methodssupporting

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Compositionally graded mullite-based chemical vapor deposited coatings

et al. 2009

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“…Many CVD processes use the metal chloride-H 2 -CO 2 system [9–12]. In this study, thermodynamic calculations using HSC ™ were used to determine the viability of the CVD process.…”

Section: Methodsmentioning

confidence: 99%

“…This atomistic deposition method can provide high purity materials with structural control at atomic or nanometer scale level. Moreover, it can produce single layer, multilayer, composite, nanostructured, and functionally graded coating materials with well controlled dimension and unique structure at low processing temperatures [9]. Furthermore, one of the unique features of CVD over other deposition techniques is the non-line-of-sight-deposition capability that has allowed the coating of complex shaped components.…”

Section: Vapor Depositionmentioning

confidence: 99%

CVD Lu2O3:Eu coatings for advanced scintillators

Topping

Sarin

2009

International Journal of Refractory Metals and Hard Materials

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Currently Lu 2 O 3 :Eu 3+ scintillators can only be fabricated via hot-pressing and pixelization, which is commercially not viable, thus restricting their use. Chemical vapor deposition is being developed as an alternative manufacturing process. Columnar coatings of Lu 2 O 3 :Eu 3+ have been achieved using the halide-CO 2 -H 2 system, clearly signifying feasibility of the CVD process. Characterization of the coatings using high resolution scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis have been used as an aid to optimize process parameters and attain highly oriented and engineered coating structures. These results have clearly demonstrated that this process can be successfully used to tailor sub-micron columnar growth of Lu 2 O 3 :Eu 3+ , with the potential of ultra high resolution x-ray imaging.

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In Situ Generated Yb₂Si₂O₇ Environmental Barrier Coatings for Protection of Ceramic Components in the Next Generation of Gas Turbines

Leite

Degenhardt²,

Krenkel

et al. 2022

Adv Materials Inter

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CO 2 emissions should be cut in half by 2050 compared to 2009 in order to limit the increase in the world average temperature to 2 °C. Despite the advances in renewable energy alternatives, their supply strongly depends on favorable weather conditions and their efficient storage is still difficult. Thus, the key factor for the transition towards a more sustainable future relies on decarbonizing power generation. Alone the substitution of heavy fossil fuels by natural gas can decrease the related emissions in ≈50%. [1][2][3][4] Nevertheless, a developing interest has been shown for carbon-free sources as ammonia and liquid hydrogen, which are potential fuel alternatives to produce energy with a cleaner emission profile. [5] Besides the compactness and low maintenance costs, gas turbines can operate with versatile fuel sources, which make them a natural choice for the efficient production of energy. For this reason, they have found increasing service in the past 40 years in the power industry both among utilities and industrial plants as well as for aviation. [6] In combined cycle operation and with inlet temperatures exceeding 1400 °C, efficiencies as high as 63% can be achieved. [2] Therefore, different strategies are adopted to protect the currently used Nibased superalloys such as the deposition of yttria-stabilized-zirconia thermal barrier coatings (TBC) and intensive film cooling. This standard is, however, not realistic when considering service for considerable amount of times (t > 10 000 h), since the rapid creep of the TBC at above 900 °C, associated with the great mismatch between its coefficient of thermal expansion (CTE) with the alloy, increase the risk of spallation and limit the use of metal-based components in turbine engines. [7][8][9][10] Especially envisioning the use of carbon-free fuel sources in future gas turbines like hydrogen or ammonia, water vapor is one of the main products of combustion, which intensifies the degradation of these alloys. [5,[11][12][13] Hence, advances towards reduced greenhouse gas emissions and more efficient gas turbines require their substitution by more robust materials resistant to oxidation and corrosion, which can endure service at higher temperatures.Due to their reduced density, lower CTE (3-5.5 × 10 −6 K −1 ), high temperature creep resistance and melting points, nonoxide silicon based ceramics as Si 3 N 4 , SiC, and SiC/SiC composites stand out for application in combustion environments. [14][15][16][17][18][19][20][21] 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. Furthermore, thermal efficiencies above 60% can be achieved using non-oxide silicon-based ceramic components. However, water vapor is one of the main combustion products leading to rapid corrosion because of volatilization of the protective SiO 2 layer at 1200 °C. An in situ generated Yb 2 Si 2 ...

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Functionally graded chemical vapor deposited mullite environmental barrier coatings for Si-based ceramics

Cited by 53 publications

References 16 publications

Compositionally graded mullite-based chemical vapor deposited coatings

Compositionally graded mullite-based chemical vapor deposited coatings

CVD Lu2O3:Eu coatings for advanced scintillators

In Situ Generated Yb₂Si₂O₇ Environmental Barrier Coatings for Protection of Ceramic Components in the Next Generation of Gas Turbines

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Functionally graded chemical vapor deposited mullite environmental barrier coatings for Si-based ceramics

Cited by 53 publications

References 16 publications

Compositionally graded mullite-based chemical vapor deposited coatings

Compositionally graded mullite-based chemical vapor deposited coatings

CVD Lu2O3:Eu coatings for advanced scintillators

In Situ Generated Yb2Si2O7 Environmental Barrier Coatings for Protection of Ceramic Components in the Next Generation of Gas Turbines

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In Situ Generated Yb₂Si₂O₇ Environmental Barrier Coatings for Protection of Ceramic Components in the Next Generation of Gas Turbines