(547b) Atomic Layer Deposition of Boron Nitride As a Hydrogen Environmental Barrier Coating

Hydrogen environmental barrier coatings can be used to reduce hydrogen embrittlement of structural materials by reducing diffusion into susceptible substrates. This protection is especially important for hydrogen pipelines and in fields such as nuclear and fuel cell applications where hydrogen is used as a fuel source. The higher the operational temperature, though, the fewer options for material choice. A nanoscale film of the current state-of-the-art material for nuclear applications, tungsten, was previously shown to increase the temperature at which hydrogen reacts with the substrate. However, the increase was still far from the operational temperature of these nuclear applications. In this work, density functional theory (DFT) calculations for energy barriers of atomic hydrogen diffusion were used to predict h-BN as a favorable material for preventing hydrogen diffusion. In addition, the diffusion pathway and the effects of hydrogen in the BN lattice were characterized. To experimentally confirm the effectiveness of BN as a barrier film, particles were coated with nanoscale BN environmental barrier coatings via atomic layer deposition (ALD). The films were then characterized for composition and thickness, and the samples were tested in a high temperature hydrogen environment using differential thermal analysis. Results showed that BN performed as predicted, preventing reaction of hydrogen with the coated sample beyond the maximum temperature of the current state-of-the-art, tungsten.