Nitride and amorphous/crystalline multilayers as hydrogen permeation barriers

Hydrogen-permeation remains a critical challenge for hydrogen-based energy systems, necessitating effective hydrogen permeation barrier (HPB) coatings. This study investigates nitride-based monolithic and multilayer (ML) coatings deposited by magnetron sputtering, including TiN, (Ti,Al)N, MoN/TaN, and Si-B-C-N-O, as well as TiN/AlN and Si-B-C-N-O/TiN MLs. Microstructural characterization revealed pronounced differences, ranging from columnar morphologies to glass-like, essentially columnar-free architectures. Hydrogen permeation resistance was evaluated on EUROFER97 substrates at 400 °C using a gaseous hydrogen permeation method and quantifying the permeation reduction factor (PRF). Monolithic crystalline coatings showed limited performance, with TiN reaching PRF ∼190, while (Ti,Al)N failed due to bias-induced defects. Contrary, TiN/AlN multilayers composed of alternating 2-nm-thin TiN and 1-nm-thin AlN layers achieved PRF >20000 by suppressing columnar diffusion paths. Amorphous Si-B-C-N-O exhibited excellent barrier performance (PRF >1000), which further improved in Si-B-C-N-O/TiN MLs (PRF ∼5300). These results demonstrate that interface engineering and microstructural control provide decisive design strategies for advanced HPBs. • TiN/AlN multilayer with 2 nm TiN and 1 nm AlN layer ratio reached PRF above 20000. • TiN and TiAlN show a correlation between reduction of defects and increase in PRF. • Amorphous Si-B-C-N-O coatings showed PRF above 1000. • Si-B-C-N-O/TiN (2:3) exhibit high PRF >5000 while boasting 28.3 ± 1.8 GPa hardness.