Atomic layer deposition of tungsten nitride films as protective barriers to hydrogen

Nanoscale films of tungsten nitride (WN) were deposited as environmental barrier coatings (EBCs) by particle atomic layer deposition (ALD) on zirconia nanoparticles and yttria stabilized zirconia micropowders. Hydrogen diffusion in tungsten (W) was investigated computationally using density functional theory and experimentally using differential thermal analysis of the ALD samples in hydrogen at temperatures > 1000 degrees C. Reaction of hydrogen with the underlying material was delayed but not eliminated by the ALD film, consistent with the low computationally predicted hydrogen diffusion barrier in bulk W of 0.19 eV. This is the first study of WN ALD films as EBCs for hydrogen above 1000 degrees C.