Hydrogen permeation properties and surface structure of BN-coated stainless steel membrane

Abstract

We developed boron nitride-coated stainless steel for vacuum vessel materials, with low adsorption rate of oxygen and carbonates. In extremely high vacuum, of a range 10 −10 Pa, the main component of the residual gas is hydrogen. We found a low adsorption rate of hydrogen on the surface of precipitated BN. A precipitated BN layer can also lower the hydrogen permeation rate of a stainless steel membrane. BN-coating has an effect on the reduction of outgassing due to, not only adsorbed hydrogen on the surface of vessel materials, but also contained hydrogen in vessel materials. We successfully coated BN on a stainless steel surface by using surface segregation from BN and the stainless steel co-deposited film. The RHEED pattern of BN showed the diffraction rings and spots of hexagonal-BN which has its C-axis orientated to the surface normal. The image using transmission electron microscopy showed a lattice of h-BN basal plane, and that the diameter of the BN crystals was 50–80 nm. This crystal structure inhibited hydrogen permeation.