Abstract: The mechanical properties of the near-surface region of oxide ceramics such as sapphire are affected by adsorbate-induced changes to dislocation mobility that can be assessed by nanoindentation with contact depth less than 30nm. Modification of this chemomechanical behaviour of the surface of sapphire by titanium ion implantation has been investigated in this study. At high doses, a soft surface amorphous layer has formed due to implantation-induced damage. However, hardness increases at low implanted doses, which is associated with implantation-induced damage but that also chemomechanical softening of the surface is reduced due to the removal of adsorbed water. For the optimum implanted dose the water readsorption does not recur even several years after the implantation treatment. This is associated with the formation of a thin, hydrophobic carbonaceous layer on the surface. This is important when designing ceramic devices such as orthopaedic implants and fibre guides that operate in an aqueous environment.
Authors: S. J. Bull and A. Yadav
Keywords: Chemomechanical effects; Imp lantation; Mechanical properties; Sapphire