The recently reported strong effect of minor oxygen impurities on the degradation of mechanical properties of superhard can be, by analogy with similar effects known in metallic alloys, understood on the basis of a simple size effect of large impurity species incorporated into the interface. The electronic effect of the sites within the interface is also likely to play an important role in weakening the Si–N and, possibly to a lesser extent, also Ti–N bonds. A simple model which assumes that the strength (and hardness) of these materials is approximately proportional to the reciprocal surface coverage of the TiN nanocrystals by oxygen impurities shows a surprisingly good agreement with the measured data.
© 2005 American Vacuum Society.
American Vacuum Society