Thin films of alumina, zirconia, tantalum oxide, and platinum were deposited on AISI304 by metal-organic chemical vapor deposition to investigate the effectiveness of these coatings in inhibiting carbon deposition and sulfide formation from thermal oxidative degradation of jet fuel. Coated AISI304 foils were heated in a laboratory scale flow reactor with a commercial jet fuel (Jet-A) flowing at 1 mL/min at a wall temperature of 350 °C and reactor pressure of 500 psig (3.4 MPa) for 5 h. Under these conditions, both liquid phase autoxidation and thermal decomposition of jet fuel contribute to carbon deposition. The surface composition of the metal oxide coatings was found by X-ray photoelectron spectroscopy. The morphology of the coating and the carbonaceous deposits formed during thermal stressing were examined by field emission scanning electron microscopy. The amount of solid carbonaceous deposits on the coated and uncoated surfaces was measured by temperature-programmed oxidation. The effectiveness of the coatings in mitigating carbon deposition was found to decrease in the following order: platinum > Ta2O 5 > alumina from acetyl acetonate > ZrO2 > alumina from aluminum trisecondary butoxide > AISI304. The coatings cover the metal surface by forming a protective layer that inhibits the formation of metal sulfides from the reaction of sulfur compounds in jet fuel with iron and nickel on stainless steel and inconel surfaces, respectively. The variation in the activity of the coatings can be attributed to the interaction of oxygenated intermediates formed by autoxidation during thermal stressing with coating surfaces having different degrees of acidity.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering