Hydrogen desorption from sand-blasted and acid-etched titanium surfaces after glow-discharge treatment

Hydrogen desorption from argon plasma-treated titanium implants with a high surface roughness was studied. Implants with a high surface roughness have shown an increase in mechanical stability in bone tissue and a different b ehavior of osteoblasts in vitro. High surface roughness was produced by gri t blasting and acid etching, resulting in an increase of the sub-surface hy drogen concentration and the formation of a titanium hydride. After an argo n plasma treatment the surface oxide, which always covers titanum surfaces exposed to an oxygen-containing environment, and some of the hydrogen were sputtered away, decreasing the hydrogen concentration in the subsurface reg ion. Nuclear reaction analysis was used to determine the hydrogen concentra tion as a function of depth. The total amount of sub-surface (down to a dep th of less than or equal to 2 mum) hydrogen remaining after plasma treatmen t decreased with increasing plasma intensity to below the levels observed i n non-acid-etched samples (similar to1-2%). Thermal desorption spectroscopy was used for desorption studies and investigation of H-2 desorption activa tion energies. With a surface oxide present, the onset of hydrogen desorpti on is at ca 400 degreesC, which is the oxide decomposition temperature in v acuum, with an activation energy of ca 2 eV/molecule of H-2. After plasma t reatment, that is, without surface oxide present, the onset of desorption w as observed at ca 300 degreesC and with an activation energy of ca 0.8 eV/m olecule of H-2, indicating a bulk diffusion-limited desorption. (C) 2000 Jo hn Wiley & Sons, Inc.