Release of hydrogen molecules from hydrogen-containing carbon film deposited on molybdenum

Molybdenum (Mo) plates covered with a hydrogen-containing carbon film, C(H)/Mo, were prepared as a model system to simulate carbon-metal mixed materials. The C(H)/Mo samples annealed at given temperatures and times in vacuum were analyzed by means of X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), thermal desorption spectroscopy (TDS) along with X-ray diffraction measurements (XRD). The XPS measurements revealed that the sample surface was covered with a carbon film containing hydrogen and a small amount of oxygen below 773 K. The Mo3d(5/2) peak appeared only after annealing at 873 K for 600 s, indicating that carbon atoms diffused to the bulk of Mo. The XRD measurements showed that Mo2C formed in the surface layer after annealing at 1073 K for 600 s. In addition, it uas observed with TDS that hydrogen molecules desorbed from the sample above 873 K. All of the above observations indicate that solid state chemical reactions take place at relatively low temperatures to cause Mo2C formation and H-2 release in the subsurface layer or out of the C(H)/Mo system. (C) 1999 Elsevier Science B.V. All rights reserved.