Mechanical properties of superhard materials synthesised at various pressure–temperature conditions investigated by nanoindentation

Abstract

Nanoindentation is applied to synthetic diamond crystals, a chemical vapour deposition (CVD) grown diamond film and to aggregated diamond nanorods produced by high-pressure compression of fullerite. Characteristic load–displacement curves are used to determine the mechanical properties and to classify these materials. Atomistic simulations have also been carried out. The results show that diamond undergoes a mainly elastic deformation during nanoindentation. Both simulations and experiments show that the force exerted on the indenter varies as the depth raised to the power 1.6. Results for the CVD grown diamond films give smaller hardness values than for the diamond crystals. For the diamond nanorods sample, hardness values lie up to those determined for diamond, whereas the elastic modulus can exceed the diamond value.