Hexagonal boron nitride as a new ultra-thin and efficient anti-coking coating for jet fuel nozzles

The pyrolysis coking of hydrocarbon fuel during active cooling has a significant impact on engine performance. The implementation of a passivation layer with a high aspect ratio within the cooling channel is considered to be an effective approach. The achievement of ultra-thin coatings with high permeability, exceptional mechanical properties, outstanding oxidation resistance, while preserving the physical and chemical characteristics of the substrate and the coating morphology remains a formidable challenge. In this study, a dense hexagonal boron nitride (hBN) film was uniformly deposited onto the surface of Ni using the chemical vapor deposition (CVD) process, serving as an effective passivation layer for anti-coking coatings. We conducted a comprehensive investigation into the thermal oxidation coking process and structural evolution of RP-3 jet fuel on Ni surface utilizing various characterization techniques, including FT-IR, SEM, and other advanced methodologies. The Raman intensity ratio (I_D/I_G) of the coking carbon material was observed to increase from 0.6286 to 0.8952 with increasing temperature, indicating an enhanced degree of coking order and a more complete cyclization of the precursor. The quality of carbon deposition in coke products was determined using the char firing method, and a quantitative investigation was conducted on the coking resistance of hBN coating. The experimental results demonstrated that the hBN coating exhibited remarkable coking inhibition rates of 83.7%, 87.1%, and 86.9% at temperatures of 450 ℃, 400 ℃, and 350 ℃, respectively. These findings demonstrate the excellent prospects of hBN as a coating for effectively inhibiting coking on metal surfaces.