Hydrogen absorption behavior was studied on molybdenum and its titanium carbide coatings by observing the pressure change in the chamber during a glow discharge. Stainless steel (SS) was also examined for comparison. The apparent absorption rate of hydrogen strongly depended on the surface state of the samples. There were rather significant decreases in the chamber pressure for molybdenum conditioned with a "hydrogen glow discharge cleaning". The surface etched by the Ar-ion bombardment for a long time showed little pressure drop. This means that the Ar-ion etching removed the contamination layers and produced a "clean" surface with a very large recombination coefficient. The effects of several pre-conditioning procedures on the hydrogen absorption rate are discussed in detail. The titanium carbide coating on molybdenum showed a strong pressure drop of hydrogen, even for the surface cleaned by the long-time Ar-ion bombardment.
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