In situ generated ß-Yb2Si2O7 environmental barrier coatings to protect non-oxide silicon-based ceramics in gas turbines / Mateus Lenz Leite.

Format:

Book

Author/Creator:

Leite, Mateus Lenz, author.

Series:

Schriftenreihe Keramische Werkstoffe

Schriftenreihe Keramische Werkstoffe ; Volume 16

Language:

English

Subjects (All):

Combustion.

Physical Description:

1 online resource (131 pages)

Edition:

1st ed.

Place of Publication:

Göttingen : Cuvillier Verlag, [2022]

Summary:

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. Si?N?, 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 SiO? layer above 1200 °C. Hence, an in situ generated Yb?Si?O? 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).

Contents:

Intro

1 Introduction and motivation

1.1 Goals

2 State of the art

2.1 Overview about gas turbines

2.2 Non-oxide silicon-based ceramics

2.3 Oxidation and hot gas corrosion behavior of Si3N4

2.4 Suitable environmental barrier coating materials

2.5 Environmental barrier coatings for Si3N4, SiC and SiC/SiC

2.6 Polymer derived ceramics

2.7 Synthesis of rare-earth silicates

2.8 Preliminary studies: silazane and Yb2O3-based systems

3 Experimental procedure

3.1 Materials

3.2 Composition and preparation of the coating slurries

3.3 Processing of powder and monolithic samples

3.4 Deposition of the Si/Yb(2:1) coating system

3.5 Characterization methods

3.6 Résumé

4 Results and discussion

4.1 Pyrolysis behavior of the Yb(2:1) composite powder

4.2 Phase composition and microstructure of the Yb(2:1) monoliths

4.3 Oxidation behavior of uncoated Si3N4 substrates

4.4 Properties of the Si/Yb(2:1) coating system on Si3N4

4.5 Deposition of thicker Yb(2:1) coatings

4.6 Si/Yb(2:1) coating system on SiC/SiC

5 Summary

6 Outlook

7 Zusammenfassung

8 References

9 Acknowledgements

10 Annexes

10.1 List of symbols and abbreviation

10.2 List of chemical compounds

10.3 List of figures

10.4 List of tables

10.5 Publications

10.6 Curriculum Vitae.

Notes:

Description based on print version record.

Other Format:

Print version: Lenz Leite, Mateus In situ generated ß-Yb₂Si₂O₇ environmental barrier coatings to protect non-oxide silicon-based ceramics in gas turbines

ISBN:

9783736965829