Mechanical properties of superhard nanocomposites

Novel superhard nanocomposites prepared according to the generic design concept [Thin Solid Films 268, (1995) 64], which is based on the formation of the appropriate nanostructure due to strong segregation and spinodal decomposition, show an unusual combination of mechanical properties, such as high intrinsic (i.e. not falsified by a large compressive stress) Vickers microhardness from 40 to ≥100 GPa, high elastic recovery (up to ≥90%), high resistance against crack formation even at a large strain of ≥10% and high thermal stability. We shall show that these properties can be relatively easily understood on the basis of conventional fracture mechanics scaled down to dimensions of a few nanometers small nanocrystals and nanocracks, in combination with a low concentration of possible flaws introduced into the material during its preparation. The latter is a consequence of the ‘self-organization’ of the system due to the thermodynamically driven formation of the stable nanostructure.