The Effect of Ultrathin ALD Films on the Oxidation Kinetics of SiC in High-Temperature Steam

Charles Musgrave, Amanda Hoskins, Tyler Gossett, Alan Weimer

Research output: Contribution to journalArticlepeer-review

5 Scopus Citations

Abstract

Ultra-thin, oxidation-resistant, pinhole-free alumina coatings were deposited on silicon carbide (SiC) particles using atomic layer deposition (ALD), and investigated as environmental barrier coatings (EBCs) for high-temperature steam oxidation. The uncoated and alumina coated SiC particles were exposed to high-temperature steam for 20 h at temperatures ranging from 1050 degrees C to 1150 degrees C to assess oxidation rates. The kinetic triplet (activation energy, rate constant, and pre-exponential factor) for each sample was determined using the D4 kinetic model (representing 3-dimensional diffusion) which was demonstrated to be accurate via the isothermal isoconversional method. Activation energies for oxidation of 247.4 +/- 0.1 kJ/mol, 250.6 +/- 0.5 kJ/mol, and 253.0 +/- 1.0 kJ/mol were calculated for uncoated SiC, SiC coated with a 5 nm alumina film, and SiC coated with a 10 nm alumina film, respectively. Reaction rate data for the oxidation reaction of uncoated SiC and SiC coated with a 10 nm film indicate that the ALD coating reduces the rate of oxidation of SiC by up to a factor of 5 for steam oxidation at temperatures between 1050 degrees C and 1150 degrees C. This is the first investigation of steam oxidation kinetics for SiC coated with an ALD deposited EBC. The results of this study indicate that ultra-thin alumina films deposited by ALD act as effective EBCs with oxidation resistance comparable to CVD films that are orders of magnitude thicker.
Original languageAmerican English
Pages (from-to)230-236
Number of pages7
JournalChemical Engineering Science
Volume201
DOIs
StatePublished - 2019

NREL Publication Number

  • NREL/JA-5K00-73562

Keywords

  • atomic layer deposition
  • environmental barrier coatings
  • oxidation/corrosion
  • silicon carbide

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